INORGANIC CHEMISTRY.1. INTRODUCTION.THIS Report follows the pattern adopted last year. The chemistry ofelements in the main groups is discussed systematically according to thePeriodic Table in Section 2, and this is followed by a treatment of thetransition elements which deals first with some general aspects of co-ordination chemistry and then with the chemistry of the individual elementsgroup by group. We begin with a summary of some recent applications ofligand-field theory to problems in inorganic chemistry. This theory hasproved helpful in understanding the stereochemistry of complex ions, theirmagnetic and optical behaviour, and their heats of formation. It has alsobeen successful in interpreting interionic distances in simple binary com-pounds, e.g., the occurrence of several M-F distances in a fluoride such asMnF,. Several general reviews of the theory have appeared during theyear.l These include introductory accounts la) as well as more rigorousand detailed treatments.lCyd Applications to the stereochemistry andmagnetic behaviour of transition elements have also been discussed.lb, I t istherefore unnecessary to restate the theory in detail or to give a generalsurvey of the results obtained, and the present Report will be restricted tothose advances of direct interest to inorganic chemistry which have beenmade during the past year.Ligand(or crystal)-field theory deals with the influence which the electro-static field generated by surrounding groups or ligands has on the energylevels of the central ion.The effect arises because the electrons on thecentral ion tend to avoid those regions where the electrostatic field of thesurrounding ligands is largest. For example, in an isolated Ti3+ ion whichhas just one electron in a d orbital, the five d orbitals are degenerate; ie.,they have the same energy. However, if the Ti3+ ion is surrounded octa-hedrally by six fluoride ions, as in TiFG3-, the d orbitals split into two sub-sets:(i) Those orbitals (d,z, dx8--y2) which are directed mainly towards the positionsoccupied by the six surrounding ions are destabilized because electrons inthem would be repelled by the charges on the ions; they are sometimescalled d, or e, orbitals; (ii) those orbitals (dxy, d, d,) which are directedin between the positions occupied by the surrounding groups will be stabilizedbecause they represent favourable distributions in which electrons on thecentral ion can be disposed as far away from the ligands as possible; thissub-set is referred to as d, or tzq.The following paragraphs indicate howthese ideas have been applied recently to several inorganic systems.TLe crystal structure of many transition-inetal trifluorides is built up ofregular or almost regular octahedra of fluoride ions which are joined by( n ) J . S. Griffith and L. E. Orgel, Quai,f. Rev., 1957, 11, 381; (G) X i . J. Gillespieand R. S . Nyholm, ibid., p. 339; (s) W. Moffitt and C. J. Ballhausen, Ann. Rev. Phys.Chewz., 1956, 7, 107; ( d ) L. E. Orgel, Inst. Infernat. Ckiwz.Solvay, l O & h Conseil Chini.,1956, 289; R. S. Nyholm, ibid.. p 22.94 INORGANIC CHEMISTlZY.sharing corners, each octahedron having a metal ion at its centre.2 Man-ganese trifluoride, however, has a lower symmetry resulting from thepresence of three different Mn-F distances in the lattice, 1.79, 1-91, and2.09 This can be understood in terms of ligand-field theory by suppos-ing that the octahedral field of the fluoride ions splits the d orbitals of theMn3+ ion into a lower triplet (d,) and an upper doublet (a,) but that thissplitting is not very large. The four d electrons in Mn3+ will therefore beunpaired and will be distributed one in each of the three d, orbitals, pointingin between the surrounding fluoride ions, and one in the d,t orbital.Thecharge on this last electron will repel the fluoride ions on the z-axis and thisaccounts for the abnormally large interionic distance in this direction. Thetheory predicts the same effect for any octahedrally co-ordinated crystalstructure or co-ordination compound in which the central ion has four un-paired d electrons, and this has been confirmed for chromous fluoride, CrF,,in which the Cr2+ ion is isoelectronic with the Mn3+ The C r F distanceis 2.43 A along the z-axis of the octahedron but only 2.01 and 1.98 A alongthe x- andy-directions. It is clear that it is no longer possible in many casesto think of ionic radii and of spherically symmetrical ions, since the interionicdistance depends on the geometry of the occupied orbitals and the directionof approach of the surrounding groups.An extension of the arguments outlined above leads one to expect largedistortions from octahedral symmetry not only in the case of four unpairedd electrons but also (a) when there are six electrons paired off in the d,orbitals and one unpaired electron in d, (e.g., low-spin Co2+), and (b) whenthere are nine d electrons.An example of the latter case is cupric fluoridein which there are two fluoride ions at 2-27 A and four at 1.93 A.5 Otherdifluorides with 5, 6, 7, 8, or 10 d electrons have an essentially un-distorted rutile-type lattice in which the various M-F bonds differ by onlyabout 0.03 A, the z-axis of the octahedron being the shortesL6Distortions from cubic symmetry which occur in certain transition-metaloxides can be simply related to the electronic configuration of the metal ion.Large deviations are expected for d4 and d9 ions in octahedral sites as justmentioned, and also for d3, d4, d8, and d9 ions in tetrahedral sites.' Thusthe following spinels deviate from cubic symmetry at room temperature :CuFe20,, CuCr20g, NiCr20a, Mn,O,, and ZnMn,O,.It seems possible thatcrystal-field theory may also explain the observed distribution of spinelsbetween the normal and inverted structures. Of the simple monoxides, allhave rock-salt symmetry except CuO which has four oxide ions in square planararrangement around each Cu2+ ion; this is an extreme example of the pre-dicted distortion, in which the two remaining oxide ions of the octahedronhave been removed right away from the influence of the central ion.2 M.A. Hepworth, K. H. Jack, R. D. Peacock, and G. J. Westland, Acfa Crysf.,8 M. A. Hepworth and K. H. Jack, ibid., p. 345; M. A. Hepworth, I(. H. Jack,1967, 10, 63.and R. S. Nyholm, Nature, 1957, 179, 211.Orgel and J. D. Dunitz, Nature, 1957, 179, 462.6 W. H. Baur, Naturwiss., 1957, 44, 349.7 J. D. Dunitz and L. E. Orgel, J . Phys. and Chetn. Solids, 1967, 3, 30.K. H. Jack and R. Maitland, Proc. Cheat. SOL, 1957, 232.C. Billy and H. M. Haendler, J . Amer. Chem. Soc., 1957, 79, 1049; see also L. EThe magnetic behaviour of octahedral complexes of iron, ruthenium, andosmium in various oxidation states has been interpreted in terms of ligand-field theory.8 The effective paramagnetic moment is frequently less than thatexpected for the spin-only moment and is markedly temperature-dependent.This is related to the strength of the coupling between the spin and orbitalangular momenta which increases with atomic number.As the effectivemoment is inversely proportional to the spin-orbit coupling constant itfollows that, for comparable complexes, the magnetic moment will increasein the sequence 0s < RLI < Fe. Variation of magnetic moment withtemperature is reported and discussed for the complexes K,KuCl,,K ,RuCl,,H ,O, (NH,) ,RuCl,,H ,O, K ,RuCl,, and K20sC1,.2. THE MAIN GROUPS.Group 1.-A model has been suggested for dilute solutions of alkali metalsin liquid ammonia based on the concept of a neutral species comprising ametal ion solvated with ammonia molecules, the valency electron from themetal being localized on the protons of these mole~ules.~ This neutralspecies can dissociate like an ion pair and can associate to a dimer.Themodel is consistent with the paramagnetic and electrical properties of suchsolutions, with the large volume increase on mixing, and with some aspectsof the absorption spectra; it is also consistent with recent nuclear magneticresonance data on solutions of sodium in liquid ammonia and is consideredto remove some of the inconsistencies inherent in the " electron cavity "model. Solutions in alkylamines have also been studied; in particular, theconductivity of lithium in methylamine lo and the absorption spectra oflithium, sodium, and potassium in a variety of primary mono- and di-amines.11Moderately stable blue solutions of potassium or sodium-potassium alloyscan be obtained in tetrahydrofuran, ethylene glycol dimethyl ether, andother ethers, but sodium alone does not dissolve.12 The solutions are goodreducing agents and are frequently more convenient to handle than aredispersions or amalgams.Advantages over solutions in liquid ammonia arefreedom from ammonolysis and the possibility of working at room tem-perature.Potassamide forms a diammine at low temperatures, KNH2,2NH,; ithas a dissociation pressure of 52 mm. Hg at -65" and is completely dis-sociated into ammonia and potassamide at room temperature. Lithiumamide and sodamide do not appear to form analogous compounds.13 Ninehydrates of sodium hydroxide have been isolated and identified by X-raydiffraction techniques, and the complete crystal structures of the mono-,tetra-, and hepta-hydrates determined.Other hydrates contained 2&, ZP,A. Earnshaw, B. M. Figgis, J. Lewis, and R. S. Nyholm, Nafuve, 1957,179, 1121.E. Becker, R. H. Lindquist, and B. J. Alder, J . Cheqn. Phys., 1956, 25, 971; seel o E. C. Evers, A. E. Young, and A. J. Panson, J . Amer. Chem. SOC., 1967, 79,G. Hohlstein and U. Wannagat, 2. anorg. Chem., 1956, 288, 193; G. \V. A.also H. M. McConnell and C. H. Holm, ibid., 1957, 26, 1517.6118.Fowles, W. R. McGregor, and M. C. R. Symons, J., 1957, 3329.l2 J. L. Down, J. Lewis, B. Moore, and G. Wilkinson, Proc. Chem. SOC., 1967, 209.l3 R.Juza and H. Liedtke, Z. anovg. Chew., 1967, 290, 20596 INORGANIC CHEMISTRY.3&, 3*, and 5 equivalents of water, the 24-hydrate being dimorphic. Therewas no evidence for a dihydrate and it was concluded that reports of thiscompound in the literature probably referred to one of the 2&-hydrates.14A study of the molecular composition of alkali halide vapours indicatesthat, except for the cmium salts, there is a significant concentration ofdimers. For sodium fluoride, lithium chloride, and lithium bromide thereis also an observable number of trimers. For the last two salts, for example,at a total pressure of lo-, mm. Hg, there is one trimer for every six monomers,and nearly three times as many dimers as monomers. Heats of dimeriz-ation are about 45 kcal.mole-l and heats of trimerization about 35 kcal.Group 11.-Beryllium amalgam has been prepared by electrolysis of afused equimolar mixture of sodium chloride and beryllium chloride, a mercurycathode being used under an atmosphere of argon.16 The amalgam, whichis very sensitive to traces of oxygen, varies from a free-flowing liquid to athick paste depending on the concentration of beryllium, and can be used toprepare the pure element.Thermal and X-ray analysis of the system KF-BeF, has shown thepresence of the compounds K,BeF, (peritectic pt. 740"), K,BeF, (m. p. 791"),KBeF, (m. p. 406"), and KBe,F, (decomp. 275").17 Ammonium trifluoro-beryllate and ammonium trifluoromanganate(I1) react in aqueous solutionto give diammonium manganous tetrafluoroberyllate, which was identifiedby analysis and X-ray powder diagram : l8mole-1.152NH4BeF3 + NH4MnF3 - (NHJ,Mn(BeF,),,6H20 + NH,FBeryllium oxyacetate, Be,O(OAc),, m.p. 285", and beryllium oxymono-chloroacetate, Be40(CH2C1*CO2),, m. p. 230°, when fused together yieldeither Be,O(OAc) ,(CH,Cl*CO ,) or Be40 ( OAC)~( CH ,Cl*CO ,) depending onthe molar ratio used; the former compound melts incongruently at 198" andthe latter congruently at 230°.19 Beryllium oxyacetate (A) forms additioncompounds with ammonia, amines, and sulphur dioxide having the formulae :A,4NH3, A,4MeNH ,, A, 3E t N H ,, and 3A,4S 0 2.20 Beryllium oxynapht hoateshave been prepared, the product from a-naphthoic acid melting at 247" andthat from the p-acid at 336".,l Both compounds are monomeric, covalentmolecules.The use of unipositive magnesium as a reducing agent in organic chemistryhas been reviewed.22The compounds HMgX have been obtained as crystalline diether com-plexes by reduction of the corresponding Grignard compounds RMgX withP.W. Hemily, Acta Cvyst., 1957, 10, 37; J. A. Wunderlich, ibid., p. 462; P. W.Hemily and J. A. Wunderlich, ibid., p. 454.l5 R. C. Miller and P. Kusch, J . Chern. Pltys., 1956, 25, 860.lC M. C. Kells, K. B. Holden, and C. I. Whitman, J . Awzer. Chem. SOC., 1957, '79, 3925.1 7 M. P. Borzenkova, A. V. Novoselova, Yu. P. Simanov, V. I. Chernykh, and Ye. I.l8 L. R. Batsanova, A. V. Novoselova, and Yu. P. Simanov, ibid., p. 2638.lB A. V. Novoselova and K.N. Semenenko, ibid., p. 2344.2o A. I. Grigor'yev, A. V. Novoselova, and K. N. Semenenko, ibid., 1957, 2, 1374.5?1 L. Krasnec, J . Kratsmjr-SmogroviC, and A. Pivoda, Chem. Zvesti, 1957, 11, 575.22 M. D. Rausch, W. E. McEwen, and J. Kleinberg, Chenz. Rev., 1957, 57, 417.Yarembash, Zhur. neorg. Khim., 1956, 1, 2071ADDISON AND GREEN WOOD : MAIN GROUPS. 97diborane. The chloride crystallizes from tetrahydrofuran and the bromideand iodide from diethyl ether, but the bound ether cannot be removedwithout decomposition of the h ~ d r i d e . ~ ~ By contrast, the hydride bromidesand hydride iodides of calcium, strontium, and barium, like the hydridechlorides reported last year, are stable salts melting in the region 660-860';they are readily prepared by fusing the appropriate alkaline-earth metalhydride and halide together at 900°.24Group 111.-The conditions under which amorphous boron of high puritycan be produced have been extensively studied 25 and an ever-increasingnumber of papers is being published on the chemistry of this element.Details have been given of the preparation and properties of the cubic formof boron nitride.26 Up to 300 mg.have been prepared in a single experiment(typically at 1800" and 85,000 atm.), and, under special conditions, octa-hedral crystallites as large as 0-3 mm. in edge have been obtained. Thenitride, which is exceptionally hard, has the zinc-blende structure andvaries in colour from black through brown and red to yellow and whitedepending on impurities.Boron phosphide has also been prepared in thezinc-blende structure 27 and a new group of compounds in the closely relatedchalcopyrite structure has been announced, vix., ABX,, where A = Zn orCd, B = Si, Ge, or Sn, and X = P or As.28Several reviews have appeared on the structure of the boron hydridesand other electron-deficient molecules.29 The structure of the new hydrideB9HI5 is built up from the boron skeleton shown in (Ia). This is an icosa-hedral fragment formed by removing three connected boron atoms not23 E. Wiberg and P. Strevel, Annalen, 1957, 607, 9.24 P. Ehrlich and H. Gortz, 2. anorg. Chem., 1956, 288, 148; P. Ehrlich and H.26 V. I. Mikheyeva, F. I. Shamai, V. Yu. Markina, and Ye. Ya. Krylova, Zhur.28 R. H. Wentorf, J . Chem.Phys., 1957, 26, 956.27 P. Popper and T. A. Ingles, Nature, 1957, 179, 1075.28 C. H. L. Goodman, ibid., p. 828.29 H. C. Longuet-Higgins, Quart. Rev., 1957, 11, 121; W. N. Lipscomb, J . Pleys.Chem., 1957, 61, 23; R. E. Rundle, ibid., p. 45; R. E. Dickerson and W. N. Lipscomb,J. Chem. Phys., 1957, 27, 212.Kulke, ibid., p. 156.neorg. Khirn., 1957, 2, 1223, 1232, 1242, 1248.REP.-VOL. LIV 98 INORGANIC CHEMISTRY.forming an equilateral triangle. The position of the bridging hydrogenatoms is indicated in (Ib).30 When decaborane, B1,H1,, reacts with iodine,substitution occurs at the apices of the two pentagonal pyramids to giveB1,H121, (2) .31 Reaction with acetonitrile, however, is more complicatedand the structure of the product, Bl,H1,,2MeCN, has not been completelyel~cidated.~,Diborane is conveniently prepared by reaction of a mixture of hydrogen,ethylene, and boron trifluoride on aluminium: 33Diborane is also formed by the displacement reaction of boron trifiuoridewith borine-trialkylamine addition compounds, but when alkali- or alkaline-earth-metal hydrides are used instead of boron trifluoride, borohydrides areformed: 33BH3*NR3 + MH = MBH, + NR3Solutions of lithium or sodium borohydrides in di(methoxyethy1) etherabsorb a molar equivalent of borine to give a product which has beenformulated as a single-bridge compound M[H,B H BH,]-.34 In thesame solvent, sodium trimethoxyborohydride, NaBH(OMe),, disproportion-ates into (soluble) sodium borohydride and insoluble sodium tetramethoxy-borate, NaB (OMe),.The solubilities are reversed if tetrahydrofuran is thesolvent, and passage of diborane through the solution results in a quanti-tative conversion of the tetramethoxyborate into sodium borohydride, thusaffording a convenient new method for synthesizing this compound.35Potassium borohydride is more stable to oxidation and to thermal decom-position than is sodium borohydride, and both salts are more stable inhydrogen than in nitrogen at high temperature^.,^Diborane reacts with cyclopropane at 80" to give tri-Pz-propylboron asone of the main prod~cts.~' With dimethylaniline, diborane gives theaddition compound BH,,Ph-NMe,, but with aniline itself substitution occursto give dianilinoborine, (Ph*NH) 2BH.38 Tetramethyldiborane, Me,B,H,,reacts with calcium in liquid ammonia to give the new compoundCaHBMe,,NH,, which is considered to be the solvated calcium salt of theanion HBMe,,-.With excess of tetramethyldiborane the compoundCa[H,BMe,],,xNH, is formed.39The diammine of tetraborane, B,H1,,2NH,, has been prepared in SO%yield by addition of ammonia to an ethereal solution of tetraborane at-78". It is monomeric, stable in air, soluble in water with only very slowevolution of hydrogen, and reacts with sodium in liquid- ammonia to give30 M. Atoji, P. J. Wheatley, and W. N. Lipscomb, J . Chern. Plys., 1957, 27, 200.31 R. Schaeffer, J . Awe?.. Chem. SOC., 1957, 79, 2726.32 Idem, ibid., p. 1006.33 R. Koster and K. Ziegler, Angew. Chem., 1957, 69, 94; R. Koster, ibid., p.94.34 H. C. Brown, P. F. Stehle, and P. A. Tierney, J . Amer. Chem. SOC., 1957, 79,35 H. C. Brown, E. J. Mead, and P. A. Tierney, ibid., p. 5400.3 6 A. G. Ostroff and R. T. Sanderson, J . Inorg. Nuclear Chern., 1957, 4, 230.37 W. A. G. Graham and F. G. A. Stone, Chem. and Ind., 1957, 1096.3* V. I. Mikheyeva and Ye. M. Fedneva, Zhur. fieorg. Khim., 1957, 2, 604.39 G. W. Campbell, J . Amer. Chem. SOC., 1957, 79, 4023.2020ADDISON AND GREENWOOD: MAIN GROUPS. 99half a mol. of hydrogen and a significant yield of the recently describedborohydride NaB,H,.40 Pentaborane adds two mols. of trimethylamine at-78" to give a product B5H,,2NMe, which, when heated above loo", partlydissociates into the original components and partly decomposes intoBH,,NMe, and the polymer (BH),.With excess of trimethylamine thc,adduct yields BH,,2NMe3 and BH polymers incorporating some trimethyl-amine, which makes them thermoplastic. The reaction is envisaged asinvolving simply the removal of 2BH, by breaking bonds of order less thanone without any rearrangement of boron or hydrogen (3).41 On the other( 3 ) ( 4 ) ( 5 )hand, the reaction of pentaborane with diinethylaniiiie or dirnethylarnino-boron hydrides, (Me,N),BH,,, yields the compounds (hlc2N),B,H4 and(Me,N) 2B,H, which appear to represent a new class of boron-nitrogencompound.41 The reaction of alcohols and ketones with ycntaborane hasalso been studied.42 The reaction with acetone was complicated but withalcohols the products were alkyl borates and hydrogen :15ROH + B,Ho = 5B(OR), + 12H, (R = Me, E t , Bu)Alkyl fluorides absorb one mol.of boron trifluoride a t low teniperaturesto give complexes which melt in the region -95" & 15" and which alkylatealkylbenzenes in good yields. The electrical conductivity of the fused methyland ethyl complexes is only of the order of 4 x but the propyl, tert.-butyl, and cyclohexyl compounds have a conductivity of 4 x ohm-Icm.-land may be considered as tetrafluoroborates, R+BF,-.43 Boron trifluorideforms a yellow 1 : 1 : 1 complex with nitryl fluoride and trifluoromethyl-benzene, [Ph*CF3,N02]'BF4-, which decomposes without melting at - 50"to give boron trifluoride and an almost quantitative yield of m-nitrotrifluoro-methylbenzene.a The infrared spectrum of solid boron trifluoride-acetylfluoride at -40" indicates that the complex is acetyl tetrafluoroborate,Me*CO+BF4-.45 Ligands (L) such as pyridine and triethylamine can absorbtwo mols.of boron trihalide at low temperatures. The complexes could beformulated as ion pairs, [L,BX,] +BX4-, but single-bridge structures suchas L-BX, X BX, were preferred (X = H, F, C1, Br).= Pyridiniunitetrachloroborate [PyH]+BC14- (m. p. 118", decomp.) and tetrabromoboratc(m. p. 140", decomp.) have been prepared by reaction of boron trihalide onpyridine h y d r ~ h a l i d e . ~ ~ The crystal structure of BaBOF, is related to that40 G. Kodama and R. W. Parry, J . Amer. Client. SOC., 1957, 79, 100T.4l A. B. Burg, ibid., p. 2129.42 A. F. Zhigach, Y e .B. Kazakova, and 12. A. Kigel', Proc. Arcid. Sri. (U.S.S.R.),43 G. OlAh, S. Kuhn, and J. Olrih, J., 1957, 2174.44 G. OlAh, L. Noszkb, and A. PavlAth, Nature, 1957, 179, 146.46 B. P. Susz and J. Wuhrmann, Helv. Chim. ,4cfa, 1957, 40, 722.46 M. F. Lappert, Proc. Chem. SOC., 1957, 121.1956, 106, 9100 INOKGAKIC CHEMISTRY.of RbBF,, the rubidium being replaced by barium and one fluorine atom byoxygen .47Boron trifluoride forms a stable, white complex with dinitrogen trioxidewhich sublimes a t room temperature but does not melt in a sealed tube at300". The complex has only weak nitrating properties but is zstrongnitrosating and diazotizing reagent, suggesting that its structure isNO+BF,N0,-.48 Amino-alcohols add 18 mol. of boron trifluoride to givecomplexes which are readily converted by protonic solvents into hydroxy-alkylamine tetrafluoroborates. For example, 2-aminoethanol gavethe complex 3BF3,2NH,*CH2*CH2*OH which was converted into[OH*CH2*CH2-NH,] +BF,-.Similarly, diamines such as ethylenediaminereacted with boron trifluoride diether complex to give amine tetrafluoroboratesof the type [NH2*CH2*CH2*NH,]+BF4-.49 The gas-phase reaction ofdiazomethane with a 200-fold excess of boron trifluoride at low pressuresand temperatures gives a quantitative yield of fluoromethylboron difluoride,F2B-CH2F (m. p. -47", b. p. +7"), which is monomeric in the gas phase butassociated in the liquid and the solid phase.50 Trisilylamine reacts withboron trifluoride to form disilylaminoboron difluoride and silyl fluoride :N(SiH,), + BF, = (SiHJ,N*BF2 + Siti,FMethyldisilylamine and dimethylsilylamine react similarly to giveMe(SiH,) N-BF, and Me,N*BF,.The silylaminoboron difluorides eliminatea further mol. of silyl fluoride at higher temperatures to give borazolederivatives. 51Diboron tetrachloride has been shown by X-ray crystal structure analysisto have the planar configuration Cl,B=BCl, with a long B-B bond; it istherefore analogous to the isoelectronic species C2o4'- and N,O, (p. l10).52However, Raman data on liquid B&14 and infrared and electron-diffractiondata on the gas indicate a structure in which the plane of one BC1, group isat right angles to that of the other.63 This surprising effect is being in-vestigated further.Polymers of overall composition BC13,BC0 have been produced bysubjecting a low-pressure mixture of boron trichioride and carbon monoxideto a discharge of 11 kv €or 160 hours.The pale yellow product has a softeningpoint of 115" and, when dispersed in water, gives a fluid of the same con-sistency as raw egg-white. This solution gives no reaction for chloride ionand, when evaporated to dryness, leaves the unchanged polymer. Thepolymer is also soluble in ethanol but without appreciably increasing theviscosity of the solvent. Preliminary experiments suggest that boron tri-fluoride and carbon monoxide give a similar solid polymer and that theproduct obtained by using silicon tetrafluoride as the halide is a viscousliquid.544 7 D. &I. Chackraburtty, A c f a Cvyst., 1957, 10, 199.4 8 G.B. Bachman and T. Hokama, J . Anaer. CIaeni. SOC., 1c357, 79, 4370.4 9 E. L. Muetterties, 2. Naturforsch., 1957, 12b, 264, 265.6" J. Goubeau and I<. H. Rohwedder, Annalen, 1957, 604, 168.51 S. Sujishi and S. Witz, J . Amer. Chem. SOL., 1957, 79, 2447.62 &I. Atoji, P. J. Wheatky, and W. N. Lipscomb, J . Ckem. Yhys., 1967, 27, 196.53 D. E. Mann and L. Fano, ibid., 1957, 26, 1665.54 T. Wartik and R. M. Rosenberg, J . Inorg. Nuclew Chcm., 1957, 3, 388ADDISON AND GREENWOOI): MAIN GROUPS. 101Triphenylborondoes not form addition compounds directly with thioethers (sulphides), butwhen bromine complexes of thioethers, R,S,Br,, react with sodium tetra-phenylborate the addition compounds are formed by a reaction which canbe written as [R,SBr]+Br- + Na+BPh,- __t NaBr + [R2SBr]+BPh4--NaBr + PhBr + R2S,BPh,.Halogen addition compounds of tetrahydro-thiophen, pyridine, and trimethylamine react similarly. 56Thermal decomposition of trimethylboron at 400-600" and 1-6 atm.gives a variety of products from which the liquid CsHzoBa (4) has beenisolated. Solid polymers of composition (B,C,H,),, (BCH),, and (BC), arealso formed during the pyrolysis, the first by elimination of methane (5) andthe others by further c~ndensation.~~ Reaction of trimethylboron withoxygen at pressures below the explosion limit produces a 1 : 1 compoundwhich is not MeB(OMe), as has been previously suggested but is dimethyl-boryl methyl peroxide, Me,BOOMe. The peroxide rearranges in a sealedtube in the liquid or the gas phase at room temperature with first-orderkinetics to give the originally suggested isomeric compound MeB(0Me) ,.The physical and chemical properties of both compounds have been studied.58Several borazens in which the B=N bond is conjugated to an aromaticsystem have been prepared by the reaction of trimethylboron with aniline orpyrrole, or the reaction of boron trichloride with diphenylamine. Theinfrared spectra of these compounds indicate a lowering of the R-N bondorder and suggest that the free electron of the nitrogen is no longer availablefor B-N bonding.59A large number of alkylboronic anhydrides, (R*BO),, have been preparedby azeotropic dehydration of the corresponding alkylboronic acids ,R*B(OH),; the arylboronic anhydrides can be prepared by the reaction oftriarylborons with boric oxide.The reaction of these anhydrides with borontrichloride has been found to be a general method for preparing alkyl- andaryl-boron dichlorides, R*BC12.60 The corresponding difluorides are bestprepared by the action of antimony trifluoride 011 the dichlorides. The dipolemoments of these various compounds and their tendencies to isomerize ordisproportionate were also studied, as were the preparation and dis-proportionation of dialkylboron chlorides, R,BCl.GOBoron trichloride forms stable 1 : 1 addition compounds with cyclicethers if these have five- or six-membered rings, but three- and four-membered rings were cleaved to form chloroalkoxyboron esters.Additioncompounds are also formed with alkyl chloroalkyl ethers, but di(ch1oro-methyl) ether did not react.61 The interaction of ethylene glycol with boronThe organic compounds of boron have been reviewed. 5565 M. F. Lappert, Chem. Rev., 1956, 56, 959.56 H. Bohme and E. Boll, 2. anorg. Chem., 1957, 291, 160.5 7 J. Goubeau and R. Epple, Chem. Ber., 1957, 90, 171.5 8 K. C. Petry and F. H. Verhoek, J . Amer. Chem. SOL, 1966, 78, 6416.59 H. J. Becher, 2. anorg. Chew., 1957,289, 262; see also idem, ibid., 1956, 288, 235.e0 P. A. McCusker, E. C. Ashby, and H. S. Makowski, J . Atner. Chenz. SOC., 1957,79, 5179, 5182; P. A. McCusker and H. S. hlakowski, ibid., p. 6185; C. Curran, P. A.McCusker, and H. S. Rlakowski, ibid., p. 5188; G.F. Hennion, P. A. McCusker, E. C.Ashby, and A. J. Rutkowski, ibid., p. 5190; P. A. McCusker, G. I;. Hennion, and E. C .Ashby, ibid., p. 5192; G. F. Hennion, P. A. McCusker, E. C. Ashby, and A. J. Rutkow-ski, ibid., p. 5194.81 J. 1). Edwards, Gerrard, and M. F. Lappert, J., 1957, 348, 377102 INORGANIC CHEMISTRY.trichloride or alkoxyboron chlorides has been used to prepare cyclic boroncompounds of general formula (CH,O),BX where X is C1, OH, OR, OPh,O*CH,*CH,*OH, O*CH,*CH,*O*B (O-CH,) ,, or O*CH2-CH,*O*B (OR) 2.62Phenylboron dichloride does not react with ethers at room temperature, butat higher temperatures C-0 fission occurs [except with diphenyl ether anddi(chloroethy1)etherl to give an alkyl chloride and Ph*BCl*OR. Studies withoptically active ethers indicate that fission is preceded by carbonium-ionformation.63Recent developments in organometallic syntheses have been reviewedwith particular emphasis on stcreospecific catalysts based on organo-aluminium compounds. 64 Triethylaluminium reacts slowly with a sus-pension of dicyclopentadienyltitanium dichloride in It-heptane to give a bluesolution which, on being cooled to -50", gives a good yield of a compoundformulated as (C5H5),TiC1,-A1Et2, m. p. 126". The complex is a weakcatalyst for the polymerization of ethylene.65 An alternative structure hasbeen suggested which involves tervalent titanium, (C,H,),TiCl,Et,AlCI,because of the known paramagnetism of the closely related comples(C,H5) ,TiCl,Etl~AlCll~, m. p. 80°, formed under similar conditions.66A kinetic study of the exchange of chloride between aluminium trichlorideand liquid carbonyl chloride has been interpreted in terms of a weak donor-acceptor interaction between the two compounds.Hydrogen chloridereduces the rate of exchange, possibly by means of the reactionAlCl, -k HC1+ COCl, + H*COCl,+ + AlC1,- despite the fact that thereis no compound formation between aluminium chloride and hydrogenchloride in the absence of a proton acceptor (in this case the very weakacceptor carbonyl ~hloride).~' The 1 : 1 addition compound betweenaluminium trichloride and acetyl chloride has been shown by infraredspectroscopy to be predominantly in the ionic form Me*CO+AlCl,-, and asimilar structure was found for the new complex with mesitoyl chloride :Me,C,H2-CO+AlC14-.68 A reinvestigation of the system aluminium tri-chloride-phosphorus oxychloride has demonstrated the existence of twocongruent compounds, AlCl,,POCl,, m.p. 186-5", and A1C1,,2POC13, m. p.165", as well as a solvate, A1Cl,,GPOCl3, which separates on long standingfrom solutions rich in the ox;ychloride.69 The complex HA1C1,OH,2Et2O isconsidered to be formed (analogously to HA1C1,,2Et2O) when a saturatedsolution of water in ether reacts with the stoicheiometric amount of an-hydrous aluminium trichloride. 70The crystal structure of gallium &chloride confirms that it is Ga+GaCl,-Each univalent Ga' ion has eight nearest ncighbours, all chlorine atoms fromsurrounding tetrahedral GaC1,- groups, arranged at the corners of a dodeca-82 J. A.Blau, W. Gerrard, and M. F. Lappert, J . , 1967, 308, 4116.63 S. H. Dandegaonker, W. Gerrard, and M. F. Lappert, ibid., p. 2893.8q K. Ziegler, Angew. Chew., 1956, 68, 721; Suomen Kern., 1957, 30, 109.85 G. Natta, P. Pino, G. Mazzanti, and U. Giannini, J . -4mer. Chpn?. Sor., 1957,6 8 D. S. Breslow and h-. R. Newburg, ibid., p. 5072.13' J. L. Huston and C. E. Lang, J . Inorg. Nuclear Chem., 1957, 4, 30.6 8 B. P. Susz and J. J. Wuhrmann, Helv. Chinz. A d a , 1957, 40, 971.69 W. L. Groeneveld and A. P. Zuur, Rec. Trav. chim., 1967, 76, 1005.70 J. Miliotis, Compt. rend., 1957, 245, 1134.79, 2975ADDISON AND GREENWOOD: MAIN GROUPS. 103hedron as in the [Mo(CN)J4- Gallium dichloride and the relatedcompound Ga+AlCl,- form stable complexes with benzene, GaPhH+MCl,-,which are not isomorphous with the apparently similar complexes of benzenewith perchloric acid and silver perchlorate.This arises from the fact thatthe lowest acceptor orbital in Ga+ is a p orbital and not an s orbital as inH+ or Ag+, so that distortion is not necessary before interaction can occurwith the donor x orbital of benzene.72 The solubility of post-transitionmetals in their molten halides, of which the solubility of gallium in itsdibromide is a typical example, has been interpreted in terms of unstablesubhalides. The solutions are diamagnetic and the solubility, which dependson the temperature as well as on the particular metal and halide considered,varies between 0.01 and 10 moles %.73The physical properties of molten gallium trichloride have been studied,and it appears that there is a slight discontinuous increase in the activationenergy of viscous flow as the compound becomes supercooled despite thesymmetrical nature of the Ga,Cl, dimer.74 The electrical conductivity offused gallium trichloride and tribromide is of the order of 10-6 ohm-l cm.-l,but this increases markedly on solidification owing to formation of an ioniclattice.75 A similar effect is well known for aluminium trichloride and forphosphorus pentachloride but seems to be a t variance with the nuclearquadrupole spectrum of gallium tribromide which has been interpreted onthe basis of the bridged dimer structure known to be present in the fusedcompound.76Phase studies on the system gallium trichloride-phosphorus oxychlorideindicate a 1 : 1 compound melting at 118.5".The electrical conductivity,viscosity, surface tension, and other properties of the fused complex havebeen determined over a range of temperature and interpreted in terms ofthe ionic structure POC1,+GaC1,-.77 The C1 + Ga bond in the complex is12 kcal. mole-1 stronger than the sum of the two bridging C1+ Ga bonds inthe gaseous Ga2C1, dimer, and the heat of formation of the crystallinecomplex from its components at 25" is 10.2 kcal. m01e-l.~~ By contrast, theheat of interaction of gallium trichloride with phosphorus trichloride isonly 3-4 kcal. mole-l, and the 1 : 1 complex, which melts incongruently at2S0, is completely dissociated into its components in the liquid phase.Absence of electrical conductivity implies a simple covalent structure forthe solid, C1,P,GaC1,.79 An analogous but more stable addition compoundis reported between triphenylphosphine and triphenylaluminium, Ph3P,A1Ph,m.p. 300°.80Thermal analysis of the indium-iodine system indicates the presence of71 G. Garton and H. M. Powell, J . Inorg. Nuclear Chem., 1957, 4, 84.72 R. E. Rundle and J. D. Corbett, J . Amer. Chem. Soc., 1957, 79, 757.7 3 J. D. Corbett, S. von Winbush, and F. C. Albers, ibid., p. 3020.74 N. N. Greenwood and K. Wade, J . Inorg. Nuclear Chem., 1957, 3, 349.7 5 N. N. Greenwood and I. J. Worrall, ibid., p. 357.76 K. G. Barnes, S. L. Segel, P. J. Bray, and P. A. Casabella, J .Chewz. P1ys., 1957,7 7 N. N. Greenwood and K. Wade, J., 1957, 1516.7 8 N. N. Greenwood and P. G. Perkins, J . Inorg. Nuclear Chern., 1957, 4, 291.7 9 N. N. Greenwood, P. G. Perkins, and K. Wade, J., 1957, 4345.8 0 0. Nennhoeffer and W. Weigel, J . prnkt. Chenz., 1957, 4, 201.26, 1345; see also S. L. Segel and R. G. Barnes, ibid., 1956, 25, 578104 INORGANIC CHEMISTRY.three congruently melting compounds, In1 (365"), InI, (225"), and Id,(207") ; these m. p.s are considerably above those recorded in the literature.81Indium halides are reduced by lithium hydride in ether at -30" to givethe solid triether complex of lithium indium hydride, LiInH,,SEt 20, whichdecomposes above 0" into lithium hydride and polymeric indium hydride(InH3),. The reduction proceeds via the intermediates LiInX,H (X = C1,Br); these were isolated as liquid ether complexes and found to react bothas LiX,InX,H and as LiH,InX,.82 Reduction of indium trichloride withlithium indium hydride affords dimeric indium trihydride, In2H6, whichpolymerizes slowly at -30" and rapidly at room temperature to the in-soluble (InH3)x; when this is warmed in vacuo white polymeric indiummonohydride (InH), is formed with evolution of hydrogen, and decompositioninto metallic indium occurs above 340".82 Indium borohydride has beenprepared by reduction of trimethylindium with diborane in tetrahydrofuranat -45", but the compound decomposes above -10" and is therefore only alittle more stable than indium aluminium hydride.82 Very similar resultsare reported for the hydrogen compounds of thallium except that the reduc-tion of thallium trichloride with lithium borohydride at -110" leads tosubstitution of only two chlorine atoms, the resulting complex, TlCl(BH,) 2,decomposing above - 95" into thallous chloride, hydrogen, and diborane.83Thallous hydroxide reacts with cyclopentadiene in aqueous solutions togive a quantitative precipitate of cycZopentadienylthallium(I), C,H,Tl; thereaction is specific for thallium and detects one part in 30,000 of this ion.84Thallous sulphide, T12S, when oxidised by dry air at 250" and 100-200 mm.pressure, forms a mixture of T1,O and TI,S,03 which interact to give thecompound T1,S02.This compound is converted into thallous sulphate onprolonged oxidation and is considered to be the addition compoundTl2S,2TI2SO3.85Group 1V.-Most lamellar compounds of graphite are ionic; a possibleexception was the system with aluminium trichloride, but it has now beenfound that intercalation will not occur unless a third substance (e.g., chlorine)capable of forming negative ions is present, SO that these compounds arealso ionic.86 Sorption of bromine on graphite diminished the diamagnetismof the host to 6% of its original value. The bromine could not be completelyremoved by pumping at low pressures and the diamagnetism did not returnto its original value, about 0.1 g. of bromine being retained per g. of theswollen graphite.87 Further chemical studies on graphitic oxide are re-ported and it is concluded that five groups are present in the structure:(i) ether-bound oxygen, (ii) C=C double bonds, (iii) tertiary hydroxyl groups,81 E.A. Pereti, J . Amer. Chem. SOC., 1956, 78, 5745.* a E. Wiberg and M. Schmidt, 2. Natwforsch., 1957, lab, 54; E. Wiberg, 0. Ditt-mann, H. Noth, and M. Schmidt, ibid., p. 56; E. Wiberg, 0. Dittmann, and M. Schmidt,ibid., p. 57; E. Wiberg and H. Noth, ibid., p. 59.83 E. Wiberg, 0. Dittmann, and M. Schmidt, ;bid., p. 60; E. Wiberg, 0. Dittmann,H. Noth, and M. Schmidt, ibid., pp. 61, 62; E. Wiberg and H. Noth, ibid., p. 63.84 13. Meister, Angew. Chem., 1957, 69, 533.8 5 B. Reuter and H. TV. Levi, Z. anovg. Chem.. 1957, 291, 239, 254.8 6 M. L. Dzurus and G. R. Hennig, J . Amer. Chem. Soc., 1957, 79, 1051.87 L. 13. Reyerson, J.E. Wertz, W. Weltner, and A. Whitehurst, J . Phys. Chem.,1957, 61, 1334ADDISON AND GREENWOOD: MAIN GROUPS. 105(iv) enol groups, and (v) keto-groups.88 Carbon monofluoride (CF), is colour-less and non-conducting, suggesting that there is a direct C-F bond involvingthe fourth carbon valency in the graphite structure; this is confirmed by theinfrared spectrum which contains only one band, namely, at the frequencyof the C-F valency vibration in fluorocarb~ns.~~The preparation, properties, and chemical reactions of carbonyl sulphidehave been reviewed.g0 The infrared spectra of (dimeric) thiocarbonylchloride and its hydrolysis product confirm the structures (6) and (7).g1The " dimer " and " trimer '' of carbonyl chloride itself, however, do nothave analogous cyclic structures despite their ready dissociation into carbonylchloride ; they are trichloromethyl chloroformate, CCl,*O*COCl, and bis-trichloromethyl carbonate, CCl,*O*CO*O*CCl,, in agreement with theirformation by exhaustive chlorination of methyl formate and methylcarbonate re~pectively.~~The hydrolysis of the trithiocarbonate ion CS,2- has been elucidated bystudying its reactions with OH-, H+, Ag+, T1+, Pb2+, and Ph-NH, by use ofchemical, potentiometric, and spectroscopic methods.The process involvesaddition of OH- to a C=S double bond followed by proton rearrangement,and comprehensive reaction schemes have been evolved. Detailed in-structions for the preparation of anhydrous sodium trithiocarbonate and itshydrates are included, as well as instructions for the preparation of sodiumalkyl xanthates by the new reaction :Na,CS, + ROH = S:C(OR)*SNa + NaSH (R = Me, E t , Pr, CH,.CH,*OH)Many other reactions and equilibria were studied and the original papershould be consulted for details.93Benzoyl chloride has been used as the basis for an ionising solvent systemand numerous reactions have been studied potentiometrically and conducto-metrically. The solvent is a useful medium for preparing anhydrouschlorides and oxychlorides as well as complexes such as (Et,N)2TiC16 and(Et,N) ,ZrC16.94 Trifluoroacetic acid has also been investigated as a solventfor ionic-type reactions.Reactions with hydrogen sulphlde closely parallelthose in aqueous acids, but fewer chlorides, perchlorates, and hydrogensulphates are soluble in this solvent.Redox reactions were also investigated,88 A. Clauss, R. Plass, H. P. Boehm, and U. Hofmann, 2. anorg. Chew., lU:?i, 291,89 W. Rudorff and K. Brodersen, 2. Naturforsch., 1957, 12b, 595.91 J. Idris Jones, W. Kynaston, and J. L. Hales, J., 1957, 614.92 J. L. Hales, J. Idris Jones, and W. Kynaston, ibid., p. 618.93 G. Ingram and B. A. Toms, ibid., p. 4328.94 V. Gutmann and H. Tannenberger, Monatsh., 1957, 88, 216, 292; V. Gutmann205.R. J . Ferm, Cheun. Rev., 1957, 57, 621.and G. Schober, ibid., p. 404I o6 INORGANIC CHEMISTRY.and there was a slow reaction between the solvent itself and potassiumpermanganate to give the gases CO,, COF,, and CF,*COF, the permanganatebeing reduced to manganese(111).95 Cryoscopy indicates that, contrary toearlier ideas, acetyl trifluoroacetate reacts almost completely with excess ofacetic acid to give acetic anhydride and trifluoroacetic acid: 96Salts of the triplienylmethyl cation Ph3C+ with complex iluoro- andchloro-anions (e.g., BF,-, Tap,-, SbC1,-, SnC1,-) have been prepared byionic reactions between triphenylmethyl chloride and the appropriate silversalts in organic solvents. Infrared evidence for the configuration of thecation is considered to favour the propellor-like D, configuration rather thanthe planar D3h.97 The compounds Ph,CCl, Ph,SiCl, Ph,GeCl, and Ph,SnCldo not dissociate into triphenylmetalloid cations and chloride anions indimethylformamide if water is rigorously excluded.Other organometallichalides of Group IV and other non-aqueous solvents were studied withsimilar results.98Silicon tetrachloride forms a 1 : 2 compound with pyridine; the whiteprecipitate formed when silicon tetrachloride reacts with a large excess ofpyridine is not the 1 : 4 compound SiC1,,4py as previously claimed, but amixture of silicic acid and pyridinium hydrochloride formed by hydrolysiswhen the pyridine has not been scrupulously dried. 99 Silicon tetrachloridereacts with nitrogen in a glow discharge to give tristrichlorosilylamine,(SiCl,),N, as one of the products. Condensation by elimination of SiCl,from this compound also occurs to give two series of compounds, (i)crystalline, cyclic compounds (Si,NCl,). of which (8) is a typical member,C I- S i -IC IMe CI\ /CH2-S I - C H ~N I I ,Sic13C IH 1C - S i-CH2-Si- CH,CI/ \Me C I'SIC13 I tCHz-Si-CHzand (ii) oily chain polymers of which the first member is Si,N,Cl,, (9), thelimiting composition at high molecular weights being the same as for thecyclic series.100 Pyrolysis of trimethylchlorosilane Me,SiCl at 800" yields acrystalline product Si,C,C1,H2, to which structure (10) has been assigned onthe basis of its chemical properties and its relation to the products of pyrolysisof tetramethylsilane mentioned in last year's Report.lol Solvolysis ofsilylphosphine, SiH,*PH,, with aqueous or alcoholic alkali gave phosphine95 G.S. Fujioka and G. H. Cady, J . Amer. Chem. SOC., 1957, 79, 2451.96 E. J. Bourne, J.C. Tatlow, and R. Worrall, J., 1957, 315.9 7 D. W. A. Sharp and N. Sheppard, ibid., p. 674.9 9 U. Wannagat and F. Veilberg, 2. anorg. Chem., 1957, 291, 310.100 A. Pflugmacher and EI. Dahmen, ibid., 1957, 290, 184.101 G. Fritz. Z . Natztrforsch., 1957. 12b, 123; see also Ann. Repovts, 1956, 53, 93.A. B. Thomas and E. G. Rochow, J . Amer. Chem. SOC., 1957, 79, 1843; J. Inorg.Nuclear Chem., 1957, 4, 205ADDISON AND GREENWOOD: MAIN GROUPS. 107and one mol. of hydrogen for each Si-H bond broken, whereas acid mediasplit only the P-S bond: lo2SiH,.PH, -t 4ROH = Si(OR), + 3H, + PH, (R = H, Et)SiH,-PH, + ROH = SiH,*OR + PH,Liquid ammonia, on the other hand, gave phosphine, silane, and a range ofsolid silicon-nitrogen compounds such as (SiH,*NH),.lo2The problem of the composition and structure of silicon nitride, Si,N,,has been resolved.The compound exists in two forms which differ only inthe sequence in which planes of atoms are linked along the 001 direction ofthe crystal.lo3An inductively heated, differential thermal-analysis apparatus has beenused to show that silicon dioxide does not react with silicon to form a solidmonoxide even at the m. p. of silicon. Similarly, no evidence was found fora solid germanium monoxide.lo4The crystal structures of silicates with highly condensed anions have beenreviewed.lo5 Cation exchange between nitrosyl chloride and the zeolitesodium analcite yields nitrosyl analcite. Exchange with anhydrous sodiummetasilicate, however, indicates that nitrosyl metasilicate is unstable evenat room temperature and decomposes as follows : lo6Na,SiO, + 2NOCI + 2NaCI + (NO),SiO, __+ 2NaCI + SiO, + N,O,Germane, GeH,, can be prepared in 75% yield by reduction of an acidicaqueous solution of germanium dioxide with sodium borohydride.Lessthan 1% of digermane and only a trace of germanium are formed simul-taneously. Stannane can be prepared by the same method, but not~1urnbane.l~~Solubility measurements and anion-exchange studies indicate that anionicchloro-complexes of the type [Ge(OH),Cl,-,]- or [Ge(OH),C1,-,]2-, where xlies between 3 and 4, are the principal species present in solutions of quad-rivalent germanium in 6--9~-hydrochloric acid.lo8 No evidence was foundfor bromo-complexes in aqueous hydrobromic acid solutions.Similarexperiments with quadrivalent tin in hydrochloric acid indicated the presenceof the ions SnC1,- and SnC1,2-.108The reactions of stannic chloride with numerous alcohols have beenstudied. Primary and secondary alcohols gave either volatile additioncompounds, SnC14,2ROH, or non-volatile products, SnCl,(OR)*ROH, ormixtures of these, whereas tertiary alcohols under appropriate conditionsgave SnCl,,ROH, SnCl,(OR),ROH, or SnCl,(OR). There was no evidencefor the formation of alkyl halides, olefins, water, hydrogen chloride, orsolvolised metal chlorides which are the typical products of the reaction of102 G. Fritz and H. 0. Berkenhoff, 2. anorg. Chem., 1957, 289, 250.Io3 D. Hardie and K. H. Jack, Nature, 1957, 180, 332.104 L.Brewer and F. T. Greene, J . Phys. aizd Chem. Solids, 1957, 2, 286; I,. Brewerlo5 F. Liebau, Z.$hys. Chem. (Leipzig), 1956, 206, 73.106 I. R. Beattie, J., 1957, 367.1 0 7 T. S. Piper and M. K. Wilson, J . Inorg. Nuclear Chew., 1957, 4, 22.108 D. A. Everest and J. C. Harrison, J., 1957, 1820, 1439.and P. Zavitsanos, ibid., p. 284108 IXORGANIC CHEMISTRY.tertiary alcohols with the tetrachlorides of silicon, titanium, zirconium, andhafnium.lo9 Lithium aluminium hydride reduces triethyliodostannane,Et,SnI, to the new compound Et,SnH, b. p. 146", which is itself a strongreducing agent.l1° The vinyl ll1 and acetylene 112 compounds of tin havealso been investigated.Stannic fluoride and phosphorus pentafluoride are Friedel-Crafts catalystsand have been found to form complexes with both one and two mols.ofaldehydes, ethers, nitriles, and amines; there is also evidence of interactionwith ethyl methyl ketone, acetic acid, and ethyl acetate.l13 Stanniciodohypophosphite, Sn14,Sn(H2P02)4, has been obtained by the action ofhypophosphorous acid on a solution of stannic iodide in alcohol. It is a paleyellow solid which melts at 319" with evolution of phosphine.l14The well-known suggestion that hydrated sodium stannate,Na2Sn0,,3H20, has the structure Na,Sn(OH), has been proved correct byan analysis of the infrared spectrum of the solid.l15A new lead hydroxycarbonate, 3PbC03,2Pb(OH) 2, has been preparedfrom a solution of lead acetate and sodium hydroxide at pH 7.7 andcharacterized by its X-ray power diagram.ll6 Cryoscopic and conducto-metric studies on dilute solutions of lead acetate in sulphuric acid point tothe formation of hexa(hydrogen su1phato)plumbic acid, H2Pb(HS0,),.Itsfirst dissociation constant, 1.1 x is slightly less than that of pyro-sulphuric acid.l17Group V.-There has been considerable activity during the year on thehydrides of the Group V elements in addition to the work already reportedunder the heading of Group I on solutions in liquid ammonia and amines.A study of solid-liquid equilibria in the ternary system NH,-N2H4-NH,C1at pressures near atmospheric suggests the formation of a 1 : 1 : 1 compound,NH3,HC1,N2H4, melting incongruently at -2.5". The compoundNH4C1,3NH3 was also confirmed.l16 A lower hydride of phosphorus,PgH4, has been obtained as a yellow solid by the decomposition of P2H4at room temperature under anhydrous conditions.In the presence ofmoisture substances are formed which correspond closely to Stock's P12H,,and by heating diphosphine under appropriate conditions non-stoicheio-metric hydrides of almost any composition below PgH4 can be obtained.ugThe conflicting reports on solid hydrides of arsenic have been reviewed andseveral methods of preparing such substances have been evaluated. Anunstable, volatile hydride thought to be diarsine, As,H,, was prepared byuse of a silent electric discharge.120109 D. C. Bradley, E. V. Caldwell, and W. Wardlaw, J , 1957, 3039.110 H. H. Anderson, J . Amer. Chem. Soc., 1957, 79, 4913.111 D.Seyferth, ibid., p. 2133; S. D. Rosenberg, A. J. Gibbons, and H. E, Ramsden,ibid., p. 2137; S. D. Rosenberg and A. J. Gibbons, ibid., p. 2138.112 H. Hartmann and H. Honig, Angew. Chem., 1957, 69, 614.113 A. A. Woolf, J . Inorg. Nuclear. Chem., 1956, 3, 285.114 D. A. Everest, J., 1957, 4149.115 R. L. Williams and R. J. Pace, ibid., p. 4143.116 H. Maunch and A. Brunold, HeEu. Chim. Acta, 1957, 40, 86.1 1 7 R. J, Gillespie and E. A. Robinson, Proc. Chem. Soc., 1957, 145.118 F. R. Hurley and H. H. Sisler, J . Anaer. Clzem. SOC., 1957, 79, 2999.119 E. C. Evers and E. H. Street, ibid., 1956, 78, 5726.120 W. L. Jolly, L. B. Anderson, and R. T. Beltrami, ibid., 1957, 79, 2443ADDISON .4ND GREENWOOD: MAIN GROUPS. 109Hydrogenation of phosphorus pentachloride with lithium borohydride at-80" or lithium aluminium hydride at - 100" did not give the pentahydridebut a mixture of phosphine and hydrogen.Antimony pentachloridebehaved similarly. Hydrogenation of derivatives of quinquevalent arsenic,antimony, and bismuth of the type MR,X,, also yielded only tervalentproducts .I21 Lithium aluminium hydride and calcium aluminium hydridereduced not only tertiary aliphatic phosphine oxides and sulphides, &POand R,PS, but also triarylphosphine sulphides, Ar,PS, to trialkyl(or aryl) -phosphines, R,P, whereas with triarylphosphine oxides an aryl group waseliminated and the product was Ar2PH.122 Lithium borohydride reducesarsenic trichloride in 93% yield to arsine, and antimony trichloride in 98%yield to stibine, but with bismuth trichloride mainly decomposition productswere 0btained.1~~ Attempts to obtain the phosphorus analogue of aniline,Ph-PH,, in the same way from Ph*PCl, resulted in production of the borineaddition compounds BH3,Ph*PH2 and BH,,Ph*PClH; these, like thehomologous nitrogen compounds, readily eliminated hydrogen or hydrogenchloride, but the resulting polymers were chain compounds rather thancyclic trimers analogous to the borazoles.The arsenic and antimonyanalogues of aniline and diphenylamine were isolated as low-melting, readilyoxidizable liquids by reduction of the appropriate phenyl-substituted tri-halide, and the arsenic analogues of piperidine and pyrrolidine (in which thearsenic is in a heterocyclic ring) were likewise prepared by the reduction ofpentamethylene- and tetrarnethylene-arsenic chloride with lithium boro-hydride : 123 {CH,).AsCl _..t (CH,),AsH.Tetrapotassium hydrazinetetrasulphonate has been prepared by electro-lytic oxidation of tripotassium aminodisulphonate in aqueous solutions byusing carbon, platinum, or lead oxide anodes and fluoride ion as a catalyst : 1%2[N(S03)J3- = 2e- + [(S0,),N*N(S03),]4-A kinetic study of the hydrolysis of the nitrilotrisulphonate ion in acetate,pyridine perchlorate, or sulphite buffers (pH 5-7) shows that the reactionis of first order with respect to both nitrilotrisulphonate and hydrogen-ionconcentrations :where B is Me*CO,-, py, or SOP-.It was assumed that the velocity of thereaction was controlled by the rate of formation or decomposition of thetrisulphonated ammonium ion, [HN (S03)J2- :[N(SO3)J" + H*OH + B = [HN(SO3)JL + + BHfH S O ' + [N(S0Jsl3-= H80 + [HN(SOJJ"or [HN(so3)d2- + H,O = H&Op + [HN(SO$J"Hydrolysis is extremely rapid in unbuffered solutions.125The infrared spectrum of solid, liquid, and gaseous dinitrogen tetroxideconfirms the planar structure O,N*NO, in all three phases in agreement with121 E.Wiberg and K. 3Edi-itzer, 2. Naturfovsch., 1956, l l b , 747, 748, 750, 751,753, 755.132 F. Hein, K. Issleib, and H. Rabold, 2. anorg. CAem., 1956, 287, a 8 .123 E. Wiberg and K. Modritzer, 2. Naturforsch., 1957, 12b, 123, 135; E. Wibergand H. Noth, ibid., pp. 125, 127, 128, 131, 132.1%4 R. R. Grinstead, J . Inorg.Nuclear Chem., 1957, 4, 287.125 I;. Seel, E. Degener, and K. Kehrer, 2. anorg. Chem., 1957,2180, 103li 10 INORGANIC CHEMISTRY.X-ray diffraction, Raman, and electron-diffraction data.126 However, theinfrared spectrum of dinitrogen tetroxide dissolved in anhydrous nitric acidshows the presence of nitrosonium and nitrate ions, NO+N03-. As theconcentration of solute is increased the lines due to non-ionised N20,molecules increase in intensity. The spectrum of NO, was not observed,and magnetic measurements confirmed that the concentration of this para-magnetic species was very ~ma11.l~~ The vapour pressures of 13 systems ofdinitrogen tetroxide with organic solvents at 0" are reported and comparedwith similar data on nitrosyl chloride-organic systems.Deviations fromideality are correlated with the polar nature and donor properties of thesolvents, and used to indicate the degree of addition compound formationin each system.128The equilibrium N20, - NO + NO, has been restudied in thetemperature range 5-45', an all-glass apparatus being used, and theresults confirm and extend earlier work.129 Nitric oxide reacts withsodium amalgam to give a quantitative yield of nitrosylsodium, NaNO.Lithium, potassium, magnesium, and barium amalgams react similarly butiron, nickel, zinc, and tin amalgams form metal(@ oxides, and cadmiumamalgam does not react at all.130 When solid hyponitrites (N,0,2-) weredispersed in a potassium bromide disc for infrared experiments, the complexspectrum of the ion as observed in mulls disappeared and was replaced bya single new frequency (1445 cm.-l).It has been claimed that this indicatesthe presence of the monomeric NO- ion in solid solution though it seemssurprising that this treatment would be sufficient to rupture the N-N bondof the hyponitrite ion.131The occurrence of multiple bonding in phosphorus compounds has beenreviewed. With few exceptions phosphorus forms essentially single bondsin those compounds where its co-ordination number is 3, 5, or 6, whereascompounds with a co-ordination number of 1 or 4 almost invariably haveappreciable multiple-bond character. This can be understood in terms ofthe overlap integrals associated with the potential ~ - b o n d s . l ~ ~ The nuclearmagnetic resonance spectra of over 200 compounds of phosphorus have beenexamined and qualitatively discussed ; the technique has also proved usefulin confinning the structure of several anions of phosphorus 0xyacids.1~~The type of thermal dehydration observed with dihydrogen mono-phosphates depends on the size of the cation rather than the temperatureof dehydration.With small (Li, Be), large (K, Rb, Cs, Ag, Zn, Cd, Hg, Ca,Sr, Ba, Pb) or highly charged (Cr3+, Fe3+, Bi") cations high-molecular chainpolyphosphates are obtained, whereas with cations of intermediate size126 R. G. Snyder and I. C. Hisatsune, J . Chern. Phys., 1957, 26, 960; R. N. Wienerand E. R. Nixon, ibid., p. 906; D. W. Smith and K. Hedberg, ibid., 1956, 25, 1283.127 D. J. Millen and D. Watson, J., 1957, 1369.128 C.C. Addison and J. C. Sheldon, ibid., p. 1937.129 I. R. Beattie and S. W. Bell, ibid., p. 1681.130 H. Hohn, V. Gutmann, and 0. Sova, Monatsh., 1957, 88, 502.131 D132 J.'k. van Wazer, J . Amer. Chern. SOC., 1956, 78, 5709; H. H. Jaff6, J . Inorg.Nuclear Chew&., 1957, 4, 372.133 J. R. van Wazer, C . F. Callis, J. N. Shoolery, and R. C. Jones, J . Amer. Chewt.SOC., 1956,78, 5715; C. F. Callis, J. R. van Wazer, J. N. Shoolery, and W. A. Anderson,ibid., 1957, 79, 2719.. Millen, C. Polydoropoulos, and D. Watson, Proc. Chern. Soc., 1967, 18ADDISON AND GREENWOOD : MAIX GROUPS. 111(Na, Mg, Al, Mn2+, Fe2+, Co, Ni, Cu2+, Zn, Cd) ring nietaphosphates areformed. The structureof insoluble magnesium tetrametaphosphate was established during thecourse of this work.134 There have also been extensive investigations of(a) the thermal dehydration of phosphoric acid a t temperatures up to 870”,(b) the hydrolysis of high molecular-weight polyphosphates, and (c) theformation and properties of condensed and cross-linked p01yphosphates.l~~The reaction of alkoxytrimethylsilanes with phosphorus trichloride ortribromide results in the stepwise replacement of halogen by alkoxy-groupsand avoids the presence of hydrogen halides or tertiary bases:Me,SiOR + PX, = Me,SiX + PX,(OR), etc.136 Alkoxyphosphorus di-chlorides can be condensed at room temperature in the presence of metaloxides to give esters of polymetaphosphorous acids : 137There is some overlap between the two types.134xROPCI2 + xM,O = 2xMCI + x(RO-P”O) + [-O-P(OR)-],Molecular-weight determinations indicate that x = 4 when K --- Bu, thcstructure being that of a normal tetrametaphosphate (11).0 0R0,ll II,ROR RO/ p- 0- p,( R = M e , E t )Hypophosphoric acid is known to be symmetrical and to contain aP-P bond.The methyl and the ethyl ester of this acid, R,P20, (la), havenow been prepared by reaction of the acid with the appropriate diazoalkaneand shown to have the same structure.138 The infrared and Rarnan spectraof tetramethyldiphosphine disulphide indicate that it too has the relatedstructure Me,P(S)*P(S)Me,.139 In addition, esters of the new isomeric iso-hypophosphoric acid (13) have been shown to be capable of existence;they are prepared by the elimination of alkyl chloride from a mixture ofdialkyl chlorophosphate (phosphorochloridate) and trialkyl phosphite : l 4 O(RO)2POCI + (RO),P(O)R = RCI + R4P206 (13)The corresponding trisodium salt has been prepared by heating a mixtureof disodium hydrogen phosphate with either sodium dihydrogen phosphiteor sodium pyrophosphite : 141Na2HPOa,12H20 + NaH2P03,24H20 = Na3(HP20,) + 154H,ONa2HP04 + Na,H,P,O, = Na,(HP,06) + NaH,P03 __ ._ _ ~ -134 E. Thilo and I. Grunze, Z. mzorg. Chem., 1957, 290, 209, 223.135 (a) E. Thilo and R. Sauer, J . prakt. Chem., 1957, 4, 324; (b) J. IV. Edwardsand A. H. Herzog, J . Amer. Chem. SOC., 1957, 79, 3647; E. Thilo and W. Wicker,2. anorg. Chenz., 1957, 291, 164; (c) E. Thilo and A. Sonntag, ibid., p. 186.136 J.Fertig, W. Gerrard, and H. Herbst, J., 1957, 1488.137 R. Schwarz and H. Geulen, Chem. Ber., 1957, 90, 952.138 M. Baudler, 2. anorg. Chem., 1956, 288, 171.139 J. Goubeau, H. Reinhardt, and D. Bianchi, 2. phys. Cheni. (Fmnkfupf), 1957,140 M. Baudler and W. Giese, Z. mrovg. Cheni., 1957, 290, 268.141 H. Remy and H. Falius, Naturwiss., 1957, 44, 419.12, 387112 INORGANIC CHEMISTRY.Reaction of phosphorus trichloride with aqueous phosphoric acid gives thefree acid: PCl, + 2H,O + H,PO, = H3(HP20,) + 3HC1.1aWhen solid disodium hypophosphate (14) is heated to 230" it undergoesinternal rearrangement to form disodium pyrophosphite (15) and disodiumpyrophosphate (16). This involves breaking the P-P bonds and formingP-0-P bonds : 1420 0 0 0 0 0Na0,II II,ONa Na0,ll II O N a Na0,ll II,ONa2 P-P 3 p-o--P= f ,P-0-P,HO' ' OH H' H HO OH( 1 4 ) ( 1 5 ) (16)The disodium pyrophosphate then condenses to higher polyphosphates.Sodium pyrophosphite (15) is also formed during the pyrolytic oxidation ofdisodium hydrogen phosphite at 180", disodium hypophosphate (14) beingformed as the intermediate : 1422Na,HPO, + I, = 2Nal + Na,H,P,O, (14)An improved preparation of monoamidophosphoric (phosphoramidic)acid, H,P0,(NH2), has been given 143 and it has been shown that the com-pound readily undergoes quantitative rearrangement at 100" to givecrystalline, soluble ammonium polyme t aphospha t e ( NH,P03),.144 Improvedpreparations of diamidsphosphoric (phosphorodiamidic) acid (1 7) have alsobeen d e v i ~ e d .l ~ $ l ~ ~ The compound is slowly hydrated by moist air at roomtemperature to give ammonium hydrogen monoamidophosphate (phosphor-amidate) (18). Replacement of the five hydrogen atoms in diamidophos-phoric (phosphorodiamidic) acid by silver gives an explosive derivative.145(17) (18) (19)The reaction between pyrophosphoryl chloride and ammonia in anhyd-rous ether gives the tetramido-derivative, reaction (A), or a polymer offormula P20,N,H, which may be considered as an amide of polymeta-phosphoric acid in which one quarter of the oxygen atoms are replaced bythe isosteric NH group (19).146 In the presence of more than 0.01% ofwater the products are phosphoric triamide and diamidophosphoric(phosphorodiamidic) acid (reaction B), and with still more water (reaction C)the ammonium salt is obtained: 1460 0 0 0!I II II !IC1,P-O-PCIz + 8NH3 = 4NH4CI + (NHs)ZP-O-P(NHJz .. . (A)0 0II I I 0 0II I1CI,P-O-PCIz + 9NH3 = 4NHICI + (NH,),P-NH, + HO-P(NHJ2 . . (B)0I10 0II I IH,O + C1,P-0-PCI, + IONH, = 4NH4CI + Z(NH,),P-ONH, . . . . . (C)142 J. H. Kolitowska, Bull. Acad. polon. Sci., GI. III, 1956, 4, 783; 1957, 5, 827.143 M. Becke-Goehring and J. Sambeth, Chem. Ber., 1957, 90, 2075.144 M. Goehring and J. Sambeth, ibid., p. 232.145 R. Klement, G. Biberacher, and V. Hille, 2. anorg. Chenz., 1957, 289, 80.146 M. Goehring and K. Niedenzu, Chem. Ber., 1957, 90, 151ADDISON ,4ND GREENWOOD : MAIN GROUPS. 113Phosphorus pentachloride also undergoes complicated ammonolysis ; 14'phosphoric triamide, formed via the intermediate imido-triamide, can beisolated (reaction D) as well as the pentamide of tri-imidotriphosphoric acid(reaction E).In addition, there is a compound isomeric with phosphorictriamide which is apparently the ammonium salt of a polymeric di-imido-phosphoric (phosphorodi-imidic) acid (F) .Ha0 PCI, + 9NH3 ___t 5NH,CI + (NH2),P:NH (NH,),P:O + NH, . . (0)O H NH H O 0 NH 0I I I! II 1 1(NHJ,P-NtH + NH2tP+NH2 + HfN-P(NHJ2 __t (NH2),P-NH-P-NH-P(NHdaII , ----------;I1 . - - _ _ _ _ _ _ _ _ _,! - - - - - - - - - - - I I ! . _ _ L _ _ _ _ _ _ _ ,I I I t . (EJNH2 NH2An X-ray structure analysis of P4S3, as well as the Raman spectrum ofthe compound in the solid, liquid, and dissolved states, indicates the struc-ture (20) 148 in agreement with earlier electron-diffraction work.The penta-sulphide, P,S,, however, has the unexpected asymmetric structure (21) inwhich one P-S bond is significantly longer than the others.149The slightly volatile compound (CF3P),, which is the first known exampleof a homocyclic ring of four phosphorus atoms, has been made by threemethods: (i) reaction of CF3*P12 with mercury at room temperature,(ii) thermal decomposition of P2(CF3), a t 350" to (CF,P), and (CF,),P, and(iii) thermal decomposition of (CF,) ,PH at the same temperature to (CF,P),and CF3H. The compound melts at 65" and has an extrapolated b. p. of145". It reacts with iodine to regenerate trifluoromethylphosphorus di-iodide, and is hydrolysed by alkali to fluorofonn and other degradationproducts.150 Improved syntheses of the intermediates CF,*PI, and(CF,),PI have been published,151 and it has been found that the methodwhereby P2(CF3), is produced by shaking (CF,),PI with mercury is a goodsource of (CF3),PH if performed in the presence of a protonic acid.152A white solid of approximate composition P,O,,F1, is formed when anequimolar mixture of phosphorus trifluoride and oxygen is subjected to147 M.Becke-Goehring and K. Niedenzu, Chern. Ber., 1957, 90, 2072.148 N. Gerding, J. W. Maarsen, and P. C. Nobel, Acta Cryst., 1957, 10, 156; YuenChu Leung, J. Waser, S. van Houten, A. Vos, G. A. Wiegers, and E. H. Wiebenga,ibid., p. 574.149 S. van Houten and E. H. Wiebenga, ibid., p. 156.150 W. Mahler and A.B. Burg, J . Avner. Ghem. SOC., 1957, 79, 251.151 A. B. Burg, W. Mahler, A. J. Bilbo, C. P. Haber, and D. L. Herring, ibid.,152 A. B. Burg and W. Mahler, ibid., p. 4212.p. 247I14 IN ORGANIC CHEMISTRY.an electrical discharge at -75". At -38" this solid evolves phosphorusoxyfluoride and phosphorus pentafluoride , leaving the new polymericmaterial (PO,F),. The decomposition of P,O1,Fl, in the temperature range-25" to 0" yields the same three products and the new compound P20,F,,m. p. -0.1", b. p. 72", which behaves chemically as pyrophosphoryl fluoride,F,0P*0*POF,.153Numerous ionic reactions in phosphorus oxychloride have been studiedpotentiometrically and with visual end-point indicators.lS4 Rapid andcomplete exchange of labelled chlorine has been observed between ionicchlorides and the solvents phosphorus oxychloride, arsenic trichloride, andselenium oxychloride.Exchange is also rapid between nitrosyl chloride andits addition compounds with ferric chloride and antimony pentachloride, inagreement with their formulation as nitrosonium salts. With the morecovalent compounds carbon tetrachloride and phosphorus oxychloride,exchange with nitrosyl chloride is slow, but rapid exchange was observedwith arsenic trichloride, and phase studies showed the presence of the newcompound AsC13,2NOC1, m. p. -S5°.155Phosphorus pentachloride reacts with the trichlorides of arsenic andantimony to give white products P2C1,,,5AsC1,, m. p. 40", and P2Cl1,,4SbC1,,m. p. 111" (decomp.). Solutions of these complexes in excess of the tri-chlorides are good electrical conductors, and cryoscopy indicates that thecompounds are predominantly solvates of the ionic pentachloride,PCl,+PCl,- ,5AsCl, and PC14+PC1,-,4SbC1,, though in the former complexthere may also be a contribution from the structure 2(PC14+AsC14-),3AsC1,.156Arsenic trifluoride reacts exothermally with potassium, rubidium,cmium, and thallium fluorides to give the tetrafluoroarsenates MAsF,, butthe fluorides of lithium and sodium do not react, suggesting that stability ofthe complexes is inversely proportional to the size and polarizing power ofthe cation.157 Arsenic trifluoride does not react with chlorine under an-hydrous conditions, but in the presence of a small amount of water therecently discovered compound AsC~,~ASF,- is formed by a reaction whichis thought to involve AsF,*OH as an intermediate. The cation AsCl,+ isreadily hydrolysed but the anion AsF,- is very resistant to hydrolysis.158Similarly, arsenic trifluoride does not react with bromine or iodine in theabsence of water.However, in the presence of water hydrolytic oxidationproceeds right through to arsenic acid, H,AsO,, and compounds of the cationsAs&,+ and Ad,+ could not be is01ated.l~~ It has also been found that48% aqueous hydrofluoric acid converts potassium dihydrogen arsenate intothe hydroxyfluoroarsenate K[AsF,OH] and not the hexafluoroarsenateKAsF, as claimed in the earlier literature. The former complex, unlike thelatter, is readily hydrolysed; it can be converted into the hexafluoroarsenateby the action of anhydrous hydrofluoric acid.lG0153 U.Wannagat and J. Rademachers, 2. agzorg. Chem., 1957, 289, 66.154 V. Gutmann and F. Mairinger, ibid., p. 279.155 J. Lewis and D. B. Sowerby, J., 1957, 556, 1617.156 L. Kolditz, 2. anorg. Chem., 1957, 289, 118.157 E. L. Muetterties and W. D. Phillips, J . Amer. Chenz. Soc., 1957, 79, 3686.1 5 8 H. M. Dess, R. W. Parry, and G. L. Vidale, ibid., 1956, 78, 5730.159 H. M. Dess and R. W. Parry, ibid., p. 5735.1 6 0 I d e m , ibid., 1957, 79, 1589ADDISON AND GREENWOOD: MAIN GROUPS. 115The previously unknown acidium salts of fatty acids have been preparedas derivatives of the SbF,- anion, and numerous other oxonium, sulphonium,and hydrazinium salts of this anion have also been isolated.161 Fluorinationof antimony pentachloride with arsenic trifluoride gives tetrachloroantimonyfluoride, SbCl,+F-, m.p. 83" (decomp.) : 1623SbCI5 + AsF, = 3SbC14+F- + AsCI,The complex is a strong electrolyte in arsenic trifluoride.The chemistry of trifluoromethyl derivatives of antimony has beenextensively studied. Trifluoromethyl iodide reacts with antimony or amixture of antimony and its tri-iodide at 165" to give the compounds(CF,),Sb, (CF,) ,SbI, and (CF,)Sb12. At higher temperatures fluorocarbonsare produced. Tristrifluoromethylstibine has much weaker donor propertiesthan has trimethylstibine and can act as an electron-acceptor to form a1 : 1 compound with pyridine. The quinquevalent derivative (CF,),SbC12also forms a 1 : 1 adduct with pyridine.The preparation and reactions ofthe chloro- and bromo-derivatives were studied and they were comparedwith the corresponding compounds of phosphorus and arsenic; e.g., theiodo-trifluoromethyl compounds of antimony disproportionate more readilythan the corresponding derivatives of phosphorus and arsenic. The distibinederivative (CF,) ,Sb*Sb(CF,) , was also investigated.163Group V1.-Plastic sulphur, at least in the extended state of fibrous+sulphur, is made up of two constituents in roughly equal proportion.One is fibrous $-sulphur, formed by helices of radius 0.92 A with a period often atoms in three turns (134' A). In the needle-shaped holes of this spongystructure, small crystals of y-sulphur occur with a repeat-pattern of 9.2 A;these crystals are built up of s8 molecules.The value 3 : 2 for the ratio ofthe two periods brings about a curious epitaxis between the two constituents.After elution with carbon disulphide only the $ skeleton is left.164When sulphur, s8, is dissolved in oleum or anhydrous sulphur trioxide,the solutions vary in colour from yellow to blue and a blue solid can beisolated which has previously been assigned the formula (SO,*S),. It is nowfound that both the solid and the solutions are paramagnetic though theprecise nature of the species is not ~ 1 e a r . l ~ ~ The product obtained by passingan electric discharge through a mixture of sulphur and sulphur dioxide,which was previously thought to be a mixture of SO and S,O, in the gasphase, has been shown to be a mixture of SO, and the new compound di-sulphur monoxide, S,O; there is no evidence for sulphur monoxide.166The generally assumed structure for N,S,H,, in which there is a puckeredeight-membered ring with alternate sulphur and nitrogen atoms, has been161 F.Klages and E. Zange, Angew. Chem., 1956, 68, 704; F. Klages, E. Miihlbauer,162 L. Kolditz, 2. anorg. Chem., 1957, 289, 128.163 J. W. Dale, H. J. Emelkus, R. N. Haszeldine, and J. H. Moss, I., 1957, 3708.164 J. A. Prins, J. Schenk, and L. H. J. Wachters, Physica, 1957, 23, 746; see alsoJ. Schenk, ibid., p. 546; A. G. Pinkus, J. S. Kim, J. L. McAtee, and C. B. Concilio,J . Amer. Chem. SOC., 1957, 79, 4566.165 D. M. Gardner and G.K. Fraenkel, ibid., 1956, 78, 6411; see also D. J. E.Ingram and M. C . R. Symons, J., 1957, 2437; M. C. R. Symons, ibid., p. 2440.166 D. J. Meschi and R. J. Myers, J . Amer. Chem. SOC., 1956, 78, 6220.and W. Uhl, ibid., p. 704; F. Klages and H. Wolf, ibid., p. 705116 INORGANIC CHEMISTKY.established as correct by an X-ray crystal structure determination.167Green-yellow crystals of the new compound S,N2F2, m. p. 86", form spon-taneously when the gases SN2F, and SNF are left in contact at reducedpressure for a long lime. The compound contains no N-N or N-F bondssince it is quantitatively hydrolysed by alkali to ammonia, and this, inconjunction with its mean oxidation number of 2.6 and its monomericmolecular weight, implies the formula F*S*N*kN*S*F.168A careful reinvestigation of the system S03-H20 near the compositionH2S0, has shown that the composition of minimum conductivity (expressedin millimoles of H20 per kg. of solution " H2S04 ") varies from 2.3 at 9-66'to 1.5 a t 40.0" and is 1.9 at 25.00" at which temperature tlic minimumconductivity is 1.0432 ohm-l cm.-l and the conductivity of pure H,SO, is1.0439 ohm-l cm.-1.169 Conductivity measurements on solutions of nitro-compounds in sulphuric acid suggest that, whereas the mononitro-compoundsbehave as weak bases, di- and tri-nitro-compounds arc non-electrolytes, inagreement with earlier conclusions drawn from cryoscopy and ultravioletspectroscopy.170 Refined chemical and thermodynamic analysis has shownthat the compound known as sulphuric acid hexaliydrate is, in fact,H2S0,,6.5H20, and detailed work has thrown some light on the nature ofthe octahydrate.lnA recent determination of the crystal structure of potassiuiii pyrosulphiteconfirms earlier work that this compound contains the 02S*S0,2- ion.172This differ from the conclusions drawn from a study of the Raman spectraof aqueous solutions of pyrosuIphites, which have been interpreted in termsof the structure 02S*O*S022-.173 However, both structures should give riseto 15 Raman lines and differ only in the detailed assignment of these lines.Studies with isotopically labelled sulphur indicate that the oxidation ofsulphite by persulphate to give dithionate proceeds via the pyrosulphateion : 174SOs2- + 0,S*0.0*S0,2- = SO,2- + OsS*0.S0,2-SO,z- + OsS*0*SO,*- = SO,2- + 0,S*S0,2-An extensive study of some oxyacids of sulphur has been published.175Thivsulphuric acid has been prepared by direct addition of hydrogen sulphideto sulphur trioxide in ether at -78" and has been isolated at low temperaturesas the diether complex, H2S20,,2Et20.By use of the sulphanes, H,S,, thisreaction affords a new class of suIphuric acid, H2S,03 ( x = 92 + 1 = 2-6).With the exception of the first member, thiosulphuric acid, which is dibasic,167 E. W. Lund and S. R. Svendsen, Acta Chcm. Scand., 1057, 11, 940.168 0. Glemser and E. It'yszomirski, Angew. Chew., 1957, 69, 534.169 R. J. Gillespie, J . V. Oubridge, and C. Solomons, J., 1057, 1804.1 7 0 H. J . Gillespie and C. Solomons, ibid., p.1796; see also R. J. Gillespie and171 $:. W. Hornung, T. E. Brackett, and IV. I:. Giauque, J. Acmv. Client. Soc., 1056,172 I. Lindqvist and M. Mortsell, Acla Cryst., 1967;10, 406.173 A. Simon, K. Waldmann, and E. Steger, Z. anorg. Chem., 1958, 288, 131.174 A. W. H. Aten, K. P. Louwrier, P. Coppens, H. A. Kok, A. hI. de lioos, E.Kriek, A. Hillege, L. Vollbracht, and F. Hartog, J . Iaorg. Nuclear Chem., 1956, 3, 296.176 M. Schmidt, 2. anorg. Chem., 1957, 289, 141, 158, 175, 193.E. A. Robinson, ibid., p. 4233.78, 5747ADDISON AND GREENWOOD: MAIN GROUPS. 117these acids are strong monobasic acids and form monoether complexes;their structure is thus H(O,S*S,*H). Addition of sulphur trioxide to theseacids gives anhydrous polythionic acids, H2S,+106, which were isolated as thediether complexes. The polythionic acids are also formed by oxidation withiodine :2H,S,03 + I , = H,S,O, + 2H1In this way the previously unknown acids H2S,06, H2S1,06, and H2S1206have been prepared.Their properties indicate that the stability of thepolythionic acids is a maximum at hexathionic acid.175A method for preparing kilogram amounts of crude sulphanes, H2S,(x = 4-6) by addition of hydrogen chloride to Na,S, has been described.176The oils so obtained can be cracked and fractionated to give pure sulphanes(x = 2-5), and the higher homologues ( x = 6-8) have been prepared in apure state by the reaction 2H,S2 + S,C1, = 2HC1 + H,S,,,. In thepresence of excess of chlorosulphanes the reaction leads to higher chloro-sulphanes: 2S,C1, + H,S, = 2HC1+ S,.,,,Cl,. The physical properties andRaman spectra of all these compounds are re~0rted.l~'A convenient means of separating and purifying sulphur tetrafluoridefrom other volatile substances has been described which involves formingthe addition compound SF,,BF, and then heating this with selenium tetra-fluoride which releases the sulphur tetrafluoride quantitatively.The com-plex can also be prepared directly by fluorinating a mixture of boron andsulphur at -75". The pentafluorides of arsenic and antimony likewise form1 : 1 complexes with sulphur tetrafl~0ride.l~~ The stability of Auoro-sulphates, MSO,F, depends on the lattice energy of the fluorides from whichthey are formed and is greatest for large cations of small charge.Thermaldecomposition of thallous and silver fluorosulphates gives pyrosulphurylfluoride, S,O,F,, which is itself decomposed at higher temperatures intosulphuryl fluoride and sulphur trioxide and is hydrolysed to fluorosulphuricacid.179 Peroxydisulphuryl difluoride, S206F2, m. p. - 55.4", b. p. 67.1 O ,has been prepared by the high-temperature reaction between sulphur tri-oxide and fluoride and has been shown by chemical reactions and infraredand nuclear magnetic resonance spectroscopy to have the structureO:S(:O)F~O~O~S(:O)F:0.180 Exchange studies with radioactive sulphurindicate that thionyl chloride and thionyl bromide can dissociate ionicallyboth as pure liquids and when dissolved in sulphur dioxide.lslThe kinetics of the reaction of the selenosulphate ion with selenious acidhave been interpreted on the basis of the overall equation lS2.4SeSOZ2- + H2Se03 + 4H+ = Se,S,0,2- + Se3S2Os2- + 3H20--1 7 6 F.Fehkr and W. Laue, ibid., 1956, 288, 103.177 F. FehQ, W. Laue, and G. Winkhaus, ibid., pp. 113, 123; 1957, 290, 52; F.Fehtr and R. Berthold, ibid., p. 251; F. Feher, K. Naused, and H. Weber, ibid., p. 303.178 N. Bartlett and P. L. Robinson, Proc. Chew. SOG., 1957, 230.1 7 9 E. Hayek, A. Czaloun, and B. Krismer, Monatsh., 1956, 87, 741; E. Hayek180 F. B. Dudley and G. H. Cady, J . Amer. Chern. Soc., 1957, 79, 513.182 I. V. Yanitskii and V. I. Zelionkaite, Zhur. neoi'g. Khim., 1957, 2, 1349; seeand A. Czaloun, ibid., p. 790.L. F. Johnson and T. H. Norris, ibid., p.1584.aIso 0. M. Baram and M. P. Soldatov, ibid., p. 1289118 I N ORGANIC CHEMISTRY.The preparation of the urea and the diazine salts of pentahalogeno-tellurous acid, HTeX,, in which the stability of TeX,- increases in the se-quence C1 < Br < I, has been described. The preparation and propertiesof the 1 : 1 addition compounds of tellurium tetrabromide with S,N,,S,N,H,, and dioxan were also investigated.l= The compound TeF,,ZCsFhas been prepared by heating caesium fluoride with an excess of telluriumhexafluoride at 250" and then cooling the mixture to room temperatureduring 24 hours. The fluorides of rubidium and potassium reacted onlyincompletely under these conditions, and those of sodium, lithium, andbarium not at all.lS4 Tellurium hexafluoride also forms 1 : 2 additioncompounds with tertiary amines but does not react with amides, nitriles, orethers.185The chemistry of polonium has been exhaustively reviewed and it appearsthat knowledge of the chemistry of this element is now comparable with thatof its lighter (and less metallic) congener tellurium.lS6 The a+ phasetransition in polonium, which occurs just above room temperature, is subjectto a hysteresis of some 36" according to recent X-ray crystallographicinvestigation.ls6" More ion-exchange and solvent extraction studies onpolonium compounds have been reported.ls7 The dependence of thesolubility of polonium hydroxide on hydroxide-ion concentration shows thatthe compound is but feebly acidic.The results have been interpreted interms of the equilibrium PoO(OH), + 2KOH K2Po03 + 2H20, forwhich the equilibrium constant K, = [K,PoO,]/[KOH]~ = (8.2 & 0.4) x 10-5.The compound is thus much less acidic than tellurous acid.188 Poloniummonosulphide has been prepared on the milligram scale by precipitation withhydrogen sulphide from hydrochloric acid solutions of polonium(1v) oxy-chloride or polonium tetrachloride.Its solubility product a t room tem-perature is about 5.5 x and its decomposition in vacuo has been usedas the basis of a new method for preparing polonium metal.189Group VI1.-General aspects of the inorganic chemistry of fluorine havebeen reviewed.lgO There has been an extensive study of hydrogen fluorideas a solvent system. Of the three common binary, protonated, self-ionizingsolvents (ammonia, water, and hydrogen fluoride) the first two are knownto dissolve ranges of compounds which can act as acids and bases, but inhydrogen fluoride only " bases " were known, i.e., compounds which in-creased the fluoride-ion concentration.The study of a wide range of binaryfluorides reveals only four compounds which are capable of increasing theconcentration of the hydrofluoronium ion H2F+ and are thus able to act as" acids "; these are boron trifluoride, stannic fluoride, and the pentafluorides183 E. E. Aynsley and W. A. Campbell, J., 1957, 832.184 E. L. Muetterties, J . Amer. Chem. Soc., 1957, 79, 1004.18s E. L. Muetterties and W. D. Phillips, ibid., p. 2975.186 K. W. Bagnall, Quart.Rev., 1957, 11, 30; " Chemistry of the Rare Radioele-18*@ J. M. Goode, J . Chem. Phys., 1957, 26, 1269.187 J. Danon and A. A. L. Zamith, J . Phys. Chem., 1957, 61, 431; T. Isimori andA. Tateda, J . Chem. SOC. Japan, 1957, 78, 78; K. W. Bagnall and D. S. Robertson,J., 1957, 509.1*8 K. W. Bagnalland J. H. Freeman, ibid., p. 2161.189 K. W. Bagnall and D. S. Robertson, ibid., p. 1044.190 A. G. Sharpe, Quart. Rev., 1957, 11, 49.ments," Butterworths, 1957, pp. 3-94AIIDISON .AND GREENWOOD: MAIN GROUPS. 119of arsenic and antimony. The acidic nature of these solutes is due to theirability to act as fluoride-ion acceptors, e.g.,2HF + BF, z+= H,F+ + BF4-Such solutions can dissolve electropositive metals. A large variety ofinorganic reactions have been carried out in anhydrous hydrogen fluorideto illustrate amphoteric behaviour, solvolysis, complex formation, etc., andto prepare compounds such as BaHF3.1g1Perchloryl fluoride, which was first prepared in 1952, is now beingproduced in ton quantities, and several papers have appeared on its physicalproperties lg2 and heat of formation.lg3 The compound is a stable gas, inertand non-corrosive at room temperature, but a powerful oxidizer at highertemperatures, and its importance is due to its possible use in metal cuttingand welding and in propulsion. It is non-toxic and has the highest dielectricstrength of any known gas. Conditions have been defined for the preparationof pure perchloryl fluoride lg4 and the kinetics of its thermal decomposition,which is unimolecular and homogeneous in quartz, have been studied in thetemperature range 470-500" .lTrifluoromethyl hypofluorite, CF,*OF, decomposes reversibly a t hightemperatures into carbonyl fluoride and fluorine.In the range 250-300"the carbonyl fluoride so formed reacts with unchanged hypofluorite to giveyerfluorodimethyl peroxide, CF,*O*O*CF3, and this compound could also beobtained by the catalytic reaction of fluorine or carbonyl fluoride with carbonmonoxide or dioxide.lg6When hydrogen chloride is bubbled through a concentrated aqueoussolution of czesium chloride the compound CsC1,HCl is precipitated and itis suggested that this contains the hydrogen-bonded ion HC1,- analogous tothe HF2- ion. The other alkali-metal chlorides do not react in this wayand it appears that a large cation is necessary for ~tability.1~7Phase studies and conductivity measurements give no evidence of acompound between chlorine trifluoride and hydrogen fluoride.198 Themicrowave spectrum of gaseous bromine trifluoride establishes that themolecule is planar and has a slightly distorted T-shape just as inchJorine t r i f l u ~ r i d e .~ ~ ~ This result agrees completely with the structurededuced from an X-ray investigation on the solid at -1125°.200 Bromine191 A. F. Clifford, H. C. Beachell, and W. M. Jack, J . Inorg. Nuclear Chem., 1957,5, 57; A. F. Clifford and A. G. Morris, ibid., p. 71; A. F. Clifford and S. Kongpricha,ibid., p. 76; A. F. Clifford and J. Sargent, J . Amer. Chem.Soc., 1957, 79, 4041; seealso F. See1 and H. Sauer, Angew. Chem., 1957, 69, 135.192 R. L. Jarry, J . Phys. Chem., 1957, 61, 498; J. Simkin and R. L. Jarry, ibid.,p. 503; A. A. Maryott and S. J. Kryder, J . Chem. Phys., 1957, 27, 1121.193 C. A. Neugebauer and J. L. Margrave, J . Amer Chem. Soc., 1957, 79, 1338;see also V. H. Dibeler, R. M. Reese, and D. E. Mann, J . Chem. Phys., 1957, 27, 176.194 J. E. Sicre and H. J. Schumacher, Angew. Chem., 1957, 69, 266; see also AH^.Reports, 1956, 53, 103.195 R. Gatti, J. E. Sicre, and H. J. Schumacher, Angew. Chem., 1957, 69, 638.196 R. S. Porter and G. H. Csdy, J . Amer. Chem. SOC., 1957, 79, 5628.lg7 R. West, ibid., p. 4568.19s M. T. Rodgers, J. L. Speirs, and M. B. Panish, J . Phys. Chem., 1957, 61, 366;see also R.M. McGill, W. S. Wendolkowski, and E. J. Barber, ibid., p. 1101.199 D. W. Magnuson, J . Chern. Phys., 1957, 27, 223.200 R. D. Burbank and F. N. Bensey, ibid., p. 982120 INORGANIC CHEMISTRY.pentafluoride has likewise been shown to have a tetragonal-pyramidal-shapedmolecule with the bromine atom below the base of the pyramid, but thestructure determination of iodine pentafluoride was not completed becauseof the low symmetry and experimental difficulties.200 The crystal-structuredetermination of iodine heptafluoride at low temperatures also proveddifficult and it appears that the structure is considerably disordered owing torandom orientation of the molecules; however, it is believed that the resultsindicate a molecular geometry in which five of the fluoride atoms form atetragonal pyramid about the iodine atom which is below the base of thepyramid as in the pentafluoride, the other two fluorine atoms being situatedbelow the iodine atom.201 This is in sharp contrast to the pentagonalbipyramid suggested on the basis of Raman and infrared spectra.The equilibrium constants for the gas-phase reaction ErF, + Br2+3BrF have been determined both manometrically and by absorption spectrain the temperature range 55-107" and lead to the values -AG298 = 1.2 kcal.mole-1, -AH = 11.9 kcal.mole-1.202 The electrical conductivity of thesystem BrF,-Br, in the liquid phase has been reinvestigated and the resultsagree with earlier work. The systems BrF,-BrF, and HF-BrF, were alsoinvestigated; the conductivity of the former system varied smoothly withconcentration, whereas that of the latter was in general greater than that ofeither pure component and was maximum near 70 moles yo of HF.Theconductivity of pure bromine trifluoride at 25" is 8-01 x 10-3 and that ofthe pentafluoride 9 x ohm-lThe X-ray data on the compound KBrF,, which was remarked upon inlast year's Report, have now been reinterpreted and it has been shown that astructure with planar rather than tetrahedral BrF4- fits the data equallywell and gives more acceptable geometry and bond distances.204The formation of polyhalide complexes by reaction of interhalogencompounds with aluminium halides in acetonitrile has been studied spectro-photometrically and electr~lytically.~~~ Conductance experiments onsolutions of tetra-alkylammonium polyiodides in acetonitrile indicate thatthe ion I,- is relatively stable at concentrations greater than O ~ O ~ M , but thatbelow this concentration its dissociation into I, and I,- is virtually complete.The I,- ion in turn is unstable below 0.0002M.206 It therefore appears thatthe I,- ion can exist in solution despite the crystal-structure determinationof Et,NI, mentioned in last year's Report which showed that compoundto be Et4NI,,212.The parent acid of the tri-iodides, HI,, has been identifiedby its absorption spectrum in carbon tetrachloride solution at 25". Theequilibrium constant for the reaction HI + I,+HI, is about 100,implying a fair degree of stability for the complex.207201 R.D. Burbank and F. N. Bensey, J . Chena., Phys., 1957, 27, 981.202 R. K. Steunenberg, R. C. Vogel, and J. Fischer, J . Amer. Chem. SOC., 1957,205 L. A. Quarterman, H. H. Hyman, and J. J- Katz, J . Phys. Chem., 1957,61, 912.204 W. G. Sly and R. E. Marsh, Acta Cryst., 1957, 10, 378; S. Siegel, ibid., p. 380;205 A. I. Popov and F. B. Stute, J . Amer. Chena. SOC., 1956, 78, 5737.206 A. I. Popov, R. Y. Rygg, and N. E. Skelly, ibid., p. 5740; see also Awn. Reports,207 J. A. Magnuson and J. H. Wolfenden, J . Phys. Chenz., 1956, 60, 1665.79, 1320.see also Ann. Reports, 1956, 53, 104.1956, 53, 104ADDISON AND GREENWOOD: MAIN GROUPS. 121Complexes of iodine, iodine monochloride, and iodine monobromide withpyridine, 2-picoline, and 2 : 6-lutidine have also been studied spectro-photometrically in carbon tetrachloride, and dissociation constants obtained.The order of stability is ICI > IBr > I, as expected, but the sequencepicoline > pyridine > lutidine suggests the intervention of a steric effectwith lutidine.The complexes, many of which were previously unknown,have been isolated and characterized by m. p.208Iodine dissolves in concentrated oleums to give blue solutions which arecharacterized by an intense band at 650 mp. This band has been tentativelyassigned to the (forbidden) triplet-singlet transition of the I+ ion. Para-magnetic-susceptibility measurements on the blue solutions have beeninterpreted by postulating that the iodine is present partly as free I+, whichshould have two unpaired electrons, and partly combined as IHSO,,IHS207, or IS0,+.209Solvent-distribution studies have established that the oxidation ofastatine with fairly concentrated hydrochloric acid results in a chloro-complex, the ether-extractability of which has been used for the isolationof astatine from bismuth targets.The complex is probably AtC1,- but maypossibly be AtCl,-. Acidic solutions, which presumably contain theastatine as HAtO, react with phenol to give astatophenol analogous toiodophenol.2103. THE TRANSITION ELEMENTS.The treatment of the chemistry of the transition elements follows thepattern of the 1956 Report. Much of the published work deals with thechemistry of complexes. Those aspects which concern the structure orgeneral properties of particular types of complex are discussed first under theheading " complexes." This section involves discussion of (a) generalaspects, including properties of ligands and the " trans "-effect, (b) metalcarbonyls and their derivatives, (c) olefin and acetylene complexes, and (d)aromatic-type complexes. The chemistry of the transition elements is thendiscussed systematically in the ten transition groups.Although this divisionis necessarily somewhat arbitrary, the complexes referred to in these latersections are regarded as being more directly concerned with the chemistryof the particular elements.An excellent review (126 pages) has been published on the use of isotopictracers in the elucidation of mechanism and structure in inorganicchemistry.211 The review is comprehensive, ard covers compounds of themain-group elements as well as transition elements.Reviews have alsobeen published on " non-stoicheiometric compounds and intermetallicphases," 212 I' interstitial compounds of transition metals " (particularlythe hydrides, nitrides, and carbides) ,213 and " non-stoicheiometric ionic208 A. I. Popov and R. H. Rygg, J . Amev. Chem. SOC., 1957, 79, 4622; see also20B M. C . R. Symons, J., 1957, 387, 2186.%lo H. M. Neumann, J . Inorg. Nuclear Chem., 1957, 4, 349.211 D. R. Stranks and R. G. Willrins, Chcm. Rev., 1957, 57, 743.212 R. Collongues, Inst. Internat. Chim. Solvay, 10th Conseil Chim., 1956, 151.m J. Bknard, ibid., p. 83.0. Hassel, Proc.Chem. Soc., 1957, 250122 INORGANIC CHEMISTRY.compounds ’’ (which is concerned with recent work on binary chalkogenidesof the transition elements) .214Complexes.-(a) General. The rate of exchange of the NH, moleculebetween solvent liquid ammonia and the 15N-labelled ammines [Ag(NH,) 2J+,[Cu(NH3)J2+, and [Ni(NH3),I2+ is rapid; in contrast, slow exchange occurswith [cr(NH3),l3+ and [CO(NH,),]~+, which is consistent with their classi-fication as inner-orbital complexes.215 The importance of traces of impurityin exchange studies has been emphasized by the observation that tris-1 : 10-phenanthroline- and tris-2 : 2’-dipyridyl-cobalt (111) ions are inert to exchangewith the free ligands in acid solution, but undergo exchange in neutralsolution owing to catalysis by cobalt(I1) impurity.From exchange ex-periments with 63Ni, it has been possible to measure rate constants fordissociation of [Ni(phen) 2]2+ and [Ni(phen)12+ for comparison with knowndata on the [Ni(phen),12+ species. The rates of dissociation of nickel(r1)and copper(I1) complexes of carbon-substituted ethylenediamines,H,N-CRR’CR”R”’*NH,, decrease as alkyl substitution increases216 Therates of dissociation of tris-1 : 10-phenanthroline-iron(z1) and -iron(m), andthe racemization of the latter, depend upon the nature and concentration ofadded anions and cations. The behaviour of the iron(II1) complex isattributed to ion-pair formation with added ions (as shown by ultravioletspectra), but with the iron(I1) complex it is an ionic background effect 0nly.217By using water as solvent, the oxygen isotope fractionation (l80/160)occurring in the aquation of [Co(NH,),XI2+ (X = C1, Br, I) ions under theinfluence of the ions Hg2+, Ag+, and TP’ has been determined.These ionsincrease the rate of halide replacement, but not the rate at which isotopicequilibrium is reached. When Hg2+ is used, there is evidence for a commonintermediate from the different halogeno-cations.218 Redox potentials forthe system L2PtC1,-L2PtC12 have been measured in mixed aqueous solvent.When L = PPrn,, the cis-isomer system has higher potential than the frans-analogue. The work provides evidence for the influence of dative x-bondingon the total transfer of charge in co-ordinate bonds; the lower-valent stateof the metal is stabilized both by inductive withholding and by mesomericwithdrawal of electrons from the metal by the ligar~d.~lgA detailed account of the tram-effect in 4- and 6-co-ordinate platinumcomplexes has been presented, with many examples of the directing effectof ligands.220 The stability of the products of the reaction[Pt(CO)X212 + 2L __t 2[P (C0)LXJ(where X = C1, Br, I) depends upon the trans-effect of the ligands L intro-duced. Weakly x-bonding ligands (e.g., NH,, 9-toluidine) do not expelcarbon monoxide, but more strongly bonding ligands (pyridine or PCl,) do214 J.BCnard, Inst. Internat. Chim. Solvay, 10th Conseil Chim., 1956, 109.215 H. IJ. D. Wiesendanger, W. H. Jones, and C. S. Garner, J . Chem. Phys., 1957,27, 668.216 K.G. Wilkins and M. J. G. Williams, J., 1957, 1763, 4514; P. Ellis, R. G.Wilkins, and M. J. G. Williams, ibid., p. 4456; R. G. Wilkins, ibid., p. 4521.217 J. E. Dickens, F. Basolo, and H. M. Neumann, J . Amer. Chem. SOC., 1957,79,1286.218 F. A. Posey and H. Taube, ibid., p. 255.219 S. Ahrland and J. Chatt, J., 1957, 1379.220 I. T. Chernyayev, Zhzsr. iaeorg. Khim., 1957, 2, 475ADDISON AND GREENWOOD: THE TRANSlTION ELRMEiXTS 123so readily.221 This directing effect also operates in solutions of cupricchloride with cupric bromide in acetone, where the formation of the complexion [CuCl3Br]2- has been examined.222 The trans-eff ect influences reactionrates ; the rates of substitution of chlorine by pyridine, ammonia, glycine,aniline, thiourea, ally1 alcohol, water, and the ions OH-, NO,-, C2042-, and36Cl- in 4-co-ordinate platinum(r1) chloroammines varies with the nature ofthe entering group. An attractive dissociation mechanism for substitutionreactions in these square complexes is ~uggested.~~3 Substitution rates havealso been measured for a series of trans-compounds [Co(AA) ,Cl,]+ (whereAA = substituted ethylenediamine) and for cis-[Co(en) 2C12]+ in methanol,where reaction of the methoxide ion becomes significant.224 From an X-raystudy of seven 4-co-ordinate platinum complexes of the type K [PtAX,](where A = C1, Br, NH,, or C2H,, and X = C1 or Br) an interesting " trans "-influence in crystals is observed.The Pt-C1 or Pt-Br distance dependsupon the ligand in the trans-position, and it is claimed that under theseconditions the nitro-group has a weaker trans-influence than chlorine orbromine.225Infrared spectra for a number of nitrato-complexes of metals have beenexamined in the region 4000-700 cm.-l, and it is now possible to distinguishthe NO,- ion from a co-ordinated nitrate group. Strong absorption bandsin the regions 1530-1480 and 1290-1250 cm.-l indicate that the nitrategroup is bonded to the metal through a single oxygen atom. Absorptiondue to -0-NO, stretching occurs as a strong peak in nitrato-complexeswithin the region 1034-970 cm.-1.226 The degenerate and symmetricaldeformation vibrations of the co-ordinate NH, group have also been charac-terized from the infrared spectra of many solid ammines. The influence ofoxidation state of the metal and of other ligands present on these vibrationshas been examined.227 The spectrophotometric study of complex ions infused salts represents an interesting development.Several transition-metalchlorides were dissolved in fused potassium nitrate-lithium nitrate melts at184"; chloro-complexes are formed on addition of potassium chloride, andattempts to follow the spectral changes involved were quite successful.228The infrared spectra of cobalt (111) complexes containing groups (SO,2-,COZ2-, C2042-, CH,=CO,-) which can co-ordinate as unidentate or bidentateligands have been compared. The lowering of symmetry of the ligand, orthe frequency shifts are more pronounced in the bidentate state.229 Workon multident ate ligands has been developed.230 The tris-salicylidene andtris-( 2-pyridylmethylene) derivatives of 2-aminomethyl-1 : 3-diaminopropanefunction as sexadentate chelate compounds with cobalt (111) and iron(II1).221 R.J. Irving and E. A. Magnusson, J., 1957, 2018.222 J. GaEo, Chern. Zvesti, 1957, 11, 7 .223 D. Banerjea, F. Basolo, and R. G. Pearson, J . Amer. Chem. SOC., 1957, 79, 4055.224 R. G. Pearson, P. M. Henry, and F. Basolo, ibid., pp. 5379, 5382.225 G. B. Bokii and G. A. Kukina, Krystallografiya, 1957, 2, 400.226 B. M. Gatehouse, S. E. Livingstone, and R. S. Nyholm, J., 1957, 4222.227 G. F. Svatos, D. M. Sweeny, S. Mizushima, C. Curran, and J. V. Quagliano,228 D. M. Gruen, J . Inorg. Nuclear Chem., 1957, 4, 74.229 K. Nakamoto, J. Fujita, S.Tanaka, and M. Kobayashi, J . Amev. Chem. SOC,.230 F. Lions and K. V. Martin, ibid., p. 1572, 2733.J . Amer. Chem. SOC., 1957, 79, 3313.1957. 79, 4904124 INORGANIC CHEMISTRY.The compounds have not yet been resolved into their optically activeantipodes.231 The complex-forming tendency of tetraethylenepentaminewith the cobalt(11) ion indicates that all five of the amino-groups co-ordinate,and the sixth position can be occupied by such groups as H,O, CH,*OH, orthe OH- ion.232 The stability constants for the corresponding nickel@)complex have been determined.233 In the complexes of copper(I1) withtrie thylenet etramine, te trae thylenepen tamine, and pent ae t hylenehexamine,the copper ion has an amine co-ordination number of five.234(b) Carbortyls.A new method for the preparation of chromium hexa-carbonyl employs readily available starting materials. Chromic acetyl-acetone complex, or chromic and chromous salts of organic acids (e.g., acetic)in pyridine are reduced readily to the hexacarbonyl at 80-170" in thepresence of powdered zinc or magnesium, and under a pressure of 100-300atm. of carbon monoxide. Soluble chromium compounds being used, theyield is 80-90%.235 In contrast to the behaviour of dimeric carbonyls, themonomeric chromium, molybdenum and tungsten carbonyls are decomposedon reaction with alkali metals in liquid ammonia: 236M(CO), + 2Na __t Na,[M(CO)51 + COMore than three of the six CO groups in these carbonyls are usually difficultto replace. However, o-phenylenebisdimethylarsine (Diarsine) reacts withthe hexacarbonyls (4-6 hours at 150" in an evacuated tube) to giveM(COj,(Diarsine) and M(CO),(Diarsine),, but replacement of the two re-maining CO groups is much more difficult.A complete X-ray study of bis( cyclopentadienylmolybdenum tricarbonyl)rules out the earlier structure in which the metal atoms and ring centreswere in the sequence C,H,-Mo-(CO),-Mo-C,H, on a straight line normal tothe plane of a ring of six CO groups.The molecule has structure (22) with aThe products are stable in( 2 3 ) ( 2 2 )Mo-Mo &stance of 3.32 A. None of the CO groups is a bridging group, andthis is the first well-established case in this class of compound in which ametal-metal bond provides the only link between the two halves of a bi-nuclear compound.In this structure the metal atoms follow the effectiveatomic number231 F. P. Dwyer, N. S. Gill, E. C. Gyarfas, and F. Lions, J . Anzer. Chem. SOL, 1957,23? H. B. Jonassen and F. W. Frey, ibid., p. 2454.218 H. B. Jonassen and L. Westerman, ibid., p. 4275.234 H. B. Jonassen, J. A. Bertrand, F. R. Groves, and R. I. Stearns, ibid., p. 4279;235 G. Natta, R. Ercoli, F. Calderazzo, and A. Rabizzoni, J . Amer. Chem. SOL,236 H. Behrens and R. Weber, 2. anorg. Chem., 1957, 291, 122.237 H. L. Nigam and R. S. Nyholm, Proc. Chem. SOL, 1957, 321.238 F. C. Wilson and D. P. Shoemaker, J. Ghem. PAYS., 1957, 27, 809.79, 1269.B. ICirsrn, Bull. SOC. chim. France, 1957, 1178.1957, 79, 3611ADDISON AND GREENWOOD : THE TIIAKSITIOB ELEMENTS 125X-Ray diffraction also shows that the structure previously postulated formanganese and rhenium carbonyls, Mn,(CO) and Re,(CO) which in-volved two bridging CO groups, is incorrect. The molecules have structure(23), with direct metal-metal bonds, and there are no bridging CO groups.The octahedron round one metal atom is rotated by 45" with respect to theother.239 The reactions of manganese carbonyl have been further in-vestigated.=(' It resembles the corresponding rhenium compound in theformation of monomeric halogen derivatives Mn(C0) ,Hal.In alkalinesolution, compounds of the [Mn(CO) 5j- ion such as the tris-o-phenanthroline-nickel(I1) salt fli(C12HsN2)3] [Mn(CO),] , are readily isolated. Reaction withsodium in liquid ammonia gives Na+[Mn(CO),]-, and the carbonyl hydrideMn(CO),H is obtained by usual methods.This melts at -20", and sublimesi n vacuo below its m. p. Treatment with diazomethane gives the methylester Mn(CO),CH, as a colourless, stable, diamagnetic compound, m. p. 95".Corresponding benzyl (m. p. 38"), acetyl (m. p. 54"), and benzoyl (m. p. 95')derivatives have been described.=l With the substituted phosphines,arsines, and stibines, manganese carbonyl gives products such asMn(CO),(PR,) ; these are monomeric and paramagnetic (= one unpairedelectron) in contrast to the cobalt compound [Co(CO),(PPh,)] which is adiamagnetic dimer. With many non-ionic ligands (ammonia, isonitriles,triphenylphosphine) rhenium chloropentacarbonyl gives derivatives of thetype [Re(CO),(NH,) ,]C1; potassium cyanide gives the analogous complexK [ Re (CO), (CN) ,] .242Suggestions regarding the structure of iron dodecacarbonyl, Fe,(CO) 12,have been made on the basis of its infrared spectrum 243 and X-ray ana1ysis.wThe structure is not yet finally settled, and there is still doubt as to therelative positions of the iron atoms and the nature of the Fe-Fe bonding.Complex ruthenium carbonyl iodides can only be obtained in the presenceof other ligands which are bonded to the metal by mesomeric double bonds.245For instance, the polymeric, diamagnetic compound [Ru(CO) 21,] givesproducts of the type [RuX,(CO) with pyridine and triphenylphosphine,and K,[Ru(CO)~(CN),I,] by reaction with potassium cyanide, butundergoes total substitution of CO by aromatic isonitriles, giving, e.g.,Many reactions of iron carbonyls have now been satisfactorily interpretedon the basis of the formation of carbonyl fe~-rate,,~~ e.g., in alcoholic alkali:Fe8(CO)lp 4- 40H-+ EFe3(C0),,I2- + C0,2- 3- 2H,Oand reactions of iron dodecacarbonyl in alcoholic solution depend upon theprimary disproportionation3Fe3(C0)1z + MeOH __t [Fe(MeOH>~JIFeS(CO),,l + 5Fe(CO),[Ru(p-CN*C6H4*O*CH,)4I2] -238 L.F. Dahl, E. Ishishi, and R. E. Rundle, J . Chem. Phys., 1957, 26, 1750.240 W. Hieber and G. Wagner, Z. Naturforsch., 1957, 12b, 478.241 R. D. Closson, J. Kozikowski, and T. H. Coffield, J . Org. Chem., 1967, 22, 598.242 W. Hieber and L. Schuster, 2. anorg. Chem., 1956, 287, 214.243 F. A.Cotton and G. Wilkinson, J . Amer. Chem. SOC., 1957, 79, 762.244 L. F. Dahl and R. E. Rundle, J . Chew. Phys., 1957, 26, 1751; 27, 323; 0. S.245 W. Hieber and H. Heusinger, J. Inorg. NucEear Chem., 1957, 4, 179.246 W. Nieber and G. Brendel, Z. anorg. Chem., 1967, 289, 324, 338.Mills, Chem. and Ind., 1957, 73126 INORGANIC CHEMISTRY.Similarly with ethylenediamine, direct substitution of the normal carbonylsto give, e.g., Fe,(CO),en,, is believed not to occur. Rather, the compoundobtained depends on t e m p e r a t ~ r e , ~ ~ and the reaction follows the schemeFe dC0) I Z+ en --+ [Wen) 31 [Fe 3(CO) 1 --t [Wen) ,I[Fe,(CO)40" 90"145"____I) [Wen) 31 [Fe(CO) 41The compound E'e(CO),(NH,)2, believed to be formed by the action of gaseousammonia in the presence of pyridine at 65", has in fact the compositionFe,(CO),(NH,),, and its properties show it to be [Fe(NH,),][Fe,(CO)8].218The well-known o-phenanthroline derivatives of Fe,(CO) are not directsubstitution products.In acetone or benzene solution at 80" the product is[Fe(phen),] [Fe,(CO),] ; in pyridine at higher temperatures the compound[Fe(phen),] [Fe,(CO) is produced. This way of representing the compoundsis supported by their electrical conductivity and reactions.249 They resemblethe products formed by reaction of metal-cobalt carbonyls with ammonia,250e*g. JHg[Co(CO)J, + 12NHS __t 3Hg + ~[CO(NH~),][CO(CO),], + 8COConipounds containing the cobalt carbonyl anion are being prepared inincreasing complexity. An organotin compound is formed by the reaction 251Sn(C4HJzCIz + 2Na[Co(CO)J __t NaCl + [Sn(C,H~),][Co(CO>,],and from an ethereal solution of this product, triphenylphosphine precipitatesyellow crystals of constitution [Sn(C,H,) ,] [Co(CO),(PPh,)] 2.Several new substituted phosphine derivatives of cobalt and rhodiumcarbonyls have been prepared.The compound [(RNC),Co]+[Co(CO),]-,formed by reaction of Co,(CO), with aromatic isonitriles, is already known;by an analogous reaction with triphenylphosphine, the compound[(PPh,)2Co(CO),]+[Co(CO),]- is formed which retains 5-co-ordination in thecati0n.~52 Rhodium(1) is isolectronic with palladium(II), and also formsstable complexes in which the low valency state is stabilized. Rhodiumcarbonyl chloride reacts as follows :[Rh,(CO)4CIJ + 4L __t 2[RhL,(CO)CI] + 2CO(where L = Ar,P, Ar,As, or Ar,Sb) to give products of high thermal stability;they are monomeric, diamagnetic, and non-electrolytes. The triarylphosphites [L = (PhO),P, (9-C,H,Me*O),P, or ($-C6H4C1*O),P] reactsimilarly. The products resemble, but are less stable than, the triaryl-phosphine compounds, and in contrast give complexes of the type [RhL,ClJwith excess of triaryl p h o ~ p h i t e .~ ~ ~247 W. Hieber, J. Sedlmeier, and R. Werner, Chem. Ber., 1967, 90, 278; ?V. Hieber248 W. Hieber and R. Werner, ibid., p. 11 16.249 W. Hieber and J. G. Floss, ibid., p. 1617.260 W. Hieber and R. Breu, ibid., p. 1259.251 W. Hieber and R. Breu, ibid., p. 1270.252 A. Sacco, Atli Accad. naz. Lincei, Rend.Classe Sci. jis. mat. Itat., 1956, 21, 442.253 L. Vallarino, J., 1957, 2287, 2473.and R. Werner, ibid., p. 286ADDISON AND GREENWOOD: THE TRANSITION ELEMENTS 127A range of olefin chelate complexesof platinum, of the type [(diene)PtX,] where X = halogen, has now beendescribed. The stabilities of the complexes are in the order cycloocta-1 : 5-diene-dicyclopentadiene > dipentene > hexa-1 : 5-diene. The stabili-ties of the dihalides decrease in the order Cl > Br > I, in accord withthe increasing trans-effect of the halogens C1 < Br < I.254 All the halidecomplexes are monomeric, and are formulated as in (24). Palladium(I1)(c) Olefin and acetylene complexes.forms a similar range of olefin chelate complexes. In general, they have thesame structures, but are more deeply coloured, more easily formed, and morereactive than the corresponding platinum(I1) complexes.255 Withrhodium(I), chloro-bridged complexes [(diene) ,Rh,Cl,] are obtained, andthe cycloocta-1 : 5-diene compounds are again the most stable.Aminesreact with halogeno-bridged dimers to give mononuclear complexes[C,H,,(am)Rh*X] and there are related cationic and anionic rhodium(1)complexes of the type [C,H,,(diamine)Rh] + and [C,H,,RhCl,]-. A bi-nuclear acetate [(C,H,,) ,Rh,(OAc) ,] is obtained by boiling an acetonesolution of the chloride with potassium acetate. The acetate groups replacethe bridging chlorine atoms, and are symmetrically Butadienecompounds of platinum(II), palladium(II), and copper(1) halides have beendescribed; they include [PtC12,C4H6] ,, [PdC12,C4H,] ,, Cu,Cl,,C,H,, andCU2Br2,C4H6.The infrared spectrum of the palladium compound indicatesthat it is a butadiene-bridged dimer.257 Crystalline complexes [PtC12,C4H,] ,have been prepared by using both cis- and trans-but-%ene, and their infraredspectra show them to be different compounds. Decomposition of thecomplexes with sodium cyanide yields the respective isomeric olefin withoutrearrangement .258A new series of acetylene complexes of general formula [Pt (PPh,) Jac)],where (ac) = acetylenic substance, have been found to result from the reduc-tion of an alcoholic suspension of cis-[Pt(PPh,),Cl,] in presence of the acetyl-ene. They are more stable to air and moisture than are the well-known olefincomplexes of platinum(I1).The complexes increase in stability in the orderC,H, < AlkCiCH < C,(Alk),-Ph-CiCH < C,Ph, < C2(p-C6H4*N02)2. Theinfrared spectra of the complexes give no indication of the presence of atriple bond, but indicate rather that the bond has been reduced almost to adouble bond and the principal structure is probably that shown in (25).259Research on alkynyl complexes has continued. The nitrosyl group in254 J. Chatt, L. M. Vallarino, and L. M. Venanzi, J . 1957, 2496.255 Idem, ibid., p. 3413.256 J. Chatt and L. M. Venanzi, ibid., p. 4735.2 5 7 P. E. Slade and H. B. Jonassen, J . Amer. Chem. SOC., 1957, 79, 1277.258 H. B. Jonassen and W. B. Kirsch, ibid., p. 1279.259 J . Chatt, G. A. Rowe, and A.A. Williams, Proc. Chern. SOL, 1957, 208128 INORGANIC CHEMISTRY.the nitroprusside ion can be replaced by the acetylide ion by reaction withpotassium acetylide in liquid ammonia:KdFe(CN),NO] + KCzR + KNH,+ K,[Fe(CN),*C,R] + N, + H,O(where R = H, CH,, C,H,). The methyl and phenyl derivativesare stable, yellow, diamagnetic compounds. The acetylide compoundK,[Fe(CN),*C,H],NH, can be obtained only at low temperatures. Above-33" oxidation occurs to give a blue-black explosive dimerK, [ (NC) ,Fe-C C-C C-Fe (CN) ,I, 2NH,. 260 Manganous thiocyanate reactswith the potassium salt of acetylene, phenylacetylene, or propene in liquidammonia :4KC,Me + Mn(SCN), + K2[Mn(C2Me),] + 2KSCNThe tetra-alkynylmanganate(11) is pyrophoric but not explosive. Magneticmeasurements indicate five unpaired electrons, consistent with sp3 hybridiz-ation.With oxygen, the acetylene complex is readily oxidized to thehighly explosive rxanganese(II1) complex K,[Mn(C,H),] .261 Systems ofsilver nitrate and silver perchlorate with but-2-yneJ pent-2-yne, andhex-3-yne have also been studied ; solid complexes are formed.262(d) Aromatic complexes. The electronic structure of metal-aromaticcomplexes formed by the cyclopentadienyl radical and by benzene has beenfurther studied. A semi-quantitative theory of the bonding has beenproposed 263 which retains those parts of the previous theories of Jaffe,Dunitz and Orgel, and Moffitt and Ruch which are most appealingphysically. The magnetic moments of 24 such compounds have beendetermined.264 An interesting comparison arises in the aromatic reactivityof ferrocene and dibenzene-chromium.In the former, the C,H,- ionacquires aromatic character by virtue of its being an anion, whereas thechromium-benzene bonding can only detract from the aromatic characterof benzene. The following reaction occurs :AlClCr(CH8*CBH5)2 + 2CH,COCI LL CH,C6H,*COCH3 + 2HCI + Crand several other reactions of dibenzene- and ditoluene-chromium have beenexamined from the point of view of aromatic reactivity.265 Ultraviolet,visible, and infrared absorption spectra on dibenzene-chromium(1) iodidein solution and in the solid state indicate that the electronic state of thebenzene rings in [Cr(C,H,)dI involves very little aromatic character; thex-electrons of benzene are thus strongly attracted to the CrI ion.,66 Protonhyperfine structure is observable in the resonance spectrum of this cation,again indicating deep-seated hybridization of the x-orbitals of the rings andthe d-orbitals of the CrI atom.267 In contrast to the extreme resistance of260 R.Nast and I?. Urban, 2. anoi'g. Chem., 1957, 289, 244.261 R. Nast and H. Griesshammes, Chem. Ber., 1957, 90, 1315.262 A. E. Comyns and H. J. Lucas, J . Amer. Chem. SOC., 1957, 79, 4341.263 A. D. Liehr and C. J. Ballhausen, Acta Chem. Scand., 1957, 11, 207.264 E. 0. Fischer and U. Piesbergen, 2. Naturforsch., 1956, llb, 758.265 H. P. Fritz and E. 0. Fischer, ibid., 12b, 67.266 S. Yamada, H. Nakamura, and R. Tsuchida, Bull. Chem. SOC. Japan, 1957,30,647.2 6 7 R.D. Feltham, P. Sogo, and M. Calvin, J . Chew. Phys., 1957, 26, 1354ADDISON AND GREENWOOD : THE TRANSITION ELEhfEKiTS. 129ferrocene to catalytic reduction, cleavage to metallic iron and cyclopentadieneis readily achieved by using lithium in ethylamine. This is of value inassigning structures to isomeric substituted ferrocenes.268Following the isolation of dibenzene complexes of chromium, molyb-denum, and tungsten, analogous compounds of other transition metals havenow been prepared. By using the system VC1,-A1C1,-A1-C6H6, red-brown[Vo(C,H,) 2] has been 0btained.26~ Its paramagnetism corresponds to oneunpaired electron, indicating a " Doppelkegelstruktur ". It can be sublimedin a vacuum at 120-150" and its m. p. (277") is near that of [Cr(C&6)2](m.p. 284"). A new preparation of the dibenzene-chromium cation employsreaction between phenylmagnesium bromide and chromyl chloride orchromium trichloride. Reduction of the tetraphenyl borate or picrate withhypophosphorous acid gives [Cro(C6H6) 21 (m. p. 282-284') identical withthat prepared by using benzene.270 By reactions in the systemReC1,-AlC1,-Al-mesitylene under reflux a t 130" (or in a bomb tube ifbenzene is used), the cations [Re(C,H,) 2]+ and [Re(C,H,Me,) 2]+ are obtained.They are diamagnetic and isoelectronic with the uncharged [Cro(C6H6) 23,which is no doubt responsible for the failure to reduce these rhenium(1)complexes to the uncharged state.271 Reactions with the systemRuC1,-A1C1,-Al-rnesitylene give pale yellow products containing the cation[Ru(C,H,Me,) 2]2+.Its diamagnetism has been confirmed by examinationof its slightly soluble salts with BPh,- and PI?,- anions.272The synthesis of a mixed sandwich complex in which a C5H5- and aC,H, ring are co-ordinated to the same metal atom is of particular interest.273In view of the stability of [Re(c6H6),]+, it was to be expected thatsubstitution of one C,H6 ring by C,H5- might give a highly stable, electricallyneutral complex. Such a preparation has in fact been achieved in the caseof manganese; reaction of phenylmagnesium bromide with methylcyclo-pentadienylmanganese chloride gives red crystals (m. p. 116-118") of thecompound [Mn(MeC,H,) (c,H,)]. On treatment of cyclopentadienyliron di-carbonyl chloride with aluminium trichloride in refluxing mesitylene, carbonmonoxide is lost and hydrolysis in the presence of iodide gives the closelyrelated compound [Fe(C,H,) (C6H3Me,)]+I-. The following group of com-pounds is therefore now available :[Cr(C6H CRe(C6H J EFe(C*H,Me,),12+1: M n (C 5 H 4 M 4 (C 6 H 611 I: Ru (C 6 H 3 Me 3) 21 2+[WC, H6)21[Fe(C5H5)(c6H s ~ e , ) i +Each has the same sandwich structure and the same electron distribution inthe metal atom.,4 detailed account has now been published of the work leading to therepresentation of Hein's polyphenylchromium compounds as sandwich268 D.S. Trifan and L. Nicholas, J . Amer. Chem. SOC., 1957, 79, 2746.2 1 3 ~ E. 0. Fischer and H. P. Kogler, Chem. Ber., 1957, 90, 250.270 H.H. Zeiss and W. Henvig, J . Anzer. Chem. Soc., 1956, 78, 5959.271 E. 0. Fischer and A. Wirzmuller, Chem. Ber., 1957, 90, 1725.272 E. 0. Fischer and R. Bottcher, 2. anorg. Chem., 1957, 291, 305.273 T. IT. Coffield, V. Sandel, and R. D. Closson, J . Amer. Chem. SOC., 1957, 79,6826.REP.-VOL. LIV 130 I N OHG AN IC CI3 E MISTKY.complexes in which the Cr atom lies between diphenyl-diphenyl or diphenyl-benzene planes. This has dispelled much of the confusion associated withthe structure of these compounds.274 The mercuric iodide complex de-composes on heating according to the equation 2T5The preparation of benzodiphenylchromium compounds by a Grignarcimethod, and some chemical properties, have been described.,76The Scandium Group and Lanthanides-The thermal decomposition ofchloride hydrates of Y, Sc, La, Ce, Pr, Nd, Sm, and Gd has been studied inthe thermobalance. The oxychloride MOCl is produced except in the casesof scandium and cerium, which give Sc,O, and CeO, re~pectively.~~' Inexperiments in which tri-n-butyl phosphate (TBP) was used to extract andseparate yttrium and the lower lanthanides, extractability was found toincrease with atomic number (La- Gd).Experiments with varying con-centrations of tributyl phosphate indicated the formation of Y (NO3),,3TBP,and the corresponding cerium and europium compounds.278 Over the fulllanthanide range (2 = 57-71) the extraction into tributyl phosphate fromaqueous nitric acid passes through a maximum at 2 = 64, so that the " half-filled shell " effect operates here as in ion-exchange separations.279 Thenitrides SmN, EuN, and YbN have been prepared by direct combination;each has the NaC1-type structure.Differential thermal analysis of SmN inmoist nitrogen indicates the formation of SmO(0H) at 250-375°.280 Thelattice constants of the lanthanide nitrides vary regularly with atomicnumber except for GdN, which is high.281 In contrast to the earlier lanth-anides, for which the sulphides M,S, involve M3+ ions only, the chemicalreactions of the samarium sulphide Sm,S, appear to justify its representationas Sm,S,,SmS, thus involving Sm2+ ions.282Ceric tert.-alkoxides Ce(OR), (where R = CMe,, CMe,Et, CMeEt,,CEt,, CMe,Prn, CMe,Pri, and CMeEtPr") have been prepared fromCe(OPri),,PriOH by alcohol interchange.The tert.-butoxide and tert.-amyl-oxide are deep yellow sublimable solids. The higher tert.-alkoxides arebright yellow liquids which distil unchanged, and are the first volatile liquidcompounds of cerium(1v) to be reported.283 A reinvestigation of thepraseodymium oxides by X-ray diffraction has shown the presence of atwo-phase system in the region PrOl.,,-Pr02, at temperatures above 350"and pressures above 10 atm. Oxidation of Pr,O,, at temperatures up to760" and pressures up to 331 atm. gives Pro, and/or Pro1.,,, with no evidence274 H. H. Zeiss and M. Tsutsui, J . Amer. Chem. SOC., 1957, 79, 3062.275 F. Hein and E. Kurras, 2. anorg. Chem., 1957, 290, 179.2 7 6 F. Hein, P. Kleinert, and E. Kurras, ibid., 289. 229.2 7 7 W.W. Wendlandt, J . Inorg. Nuclear Chem., 1957, 5, 118.278 D. Scargill, K. Alcock, J. M. Fletcher, E. Hesford, and H. A. C . McKay, ibid.,2 7 9 D. F. Peppard, W. J. Driscoll, R. J. Sironen, and S. McCarty, ibid., p. 326.280 H. A. Eick, N. C. Baenziger, and L. Eyring, J . Amer. Chem. SOC., 1956, '78, 5987.z81 W. Klemm and G. Winkelmann, 2. anorg. Chem., 1956, 288, 87.282 M. Picon and J. Flahaut, Compt. rend., 1956, 243, 2074.288 D. C. Bradley, A. K. Chatterjee, and W. Wardlaw, J., 1957, 2600.4, 304ADDISON AND GREENWOOD : THE TRANSITION ELEMEKTS. I31of an intermediate phase.284 Data on the complex-formation of CeIlI, LaTLL,and GdlIr by fluoride ions in solution can be interpreted satisfactorily byassuming only the presence of the simplest complex MF2+.285Europium and ytterbium metals dissolve in liquid ammonia at -78" togive characteristic blue solutions.Evaporation of the solutions left goldenmetallic crystals, presumably of the metal hexa-ammines. Samarium isinsoluble.286 The heat of formation of the holmium oxide Ho203 is-449.5 kcal./mole; this value lies midway between known values fordysprosium and erbi~m.~87 The five lanthanide elements immediatelypreceding thulium have similar vapour pressures, but measurements onthulium at 809-1219" K indicate a high vapour pressure. The heat ofsublimation is 57.4 kcal./mole. This enhanced volatility (which is stillhigher in ytterbium) is attributed to the approach towards the filling of the4f electron shell.288The Titanium Group.-The trialkoxy-titanium compounds (RO),Tioxidize in air to give dialkoxytitanium oxides (RO),TiO.Under suitableexperimental conditions, a current of dry oxygen being used, hexa-alkoxy-dititanoxanes (RO),Ti*O*Ti(OR), can be obtained. Thus the main productof oxidation of triethoxytitanium is (EtO) 6Ti20.289 Attempts to preparetitanium tetra-acetate by treatment of the tetrachloride or its alkoxides withacetic anhydride resulted in formation of the basic triacetate [T~(OAC),],O.~~~The crystal structure of the simple compound TiOS0,,H20 is built up from-Ti-O-Ti-O- chains held together by sulphate groups.291 The nature ofthe alkyl group has a significant influence on the hydrolytic behaviour oftitanium alkoxides, Ti(OR),. There is a remarkably low degree of poly-merization in the products of hydrolysis in alcohols of high boiling point.292The equilibrium between titanium di- and tri-chlorides and titaniummetal, in the presence of a NaC1-KC1 melt, is such that Ti2+ is thepredominant species, representing 90% of the dissolved titanium.The Ti4+content of melts equilibrated with titanium metal is negligible.293 Methodsof preparation of titanium(II1) oxychloride have been re-examined.Titanium trichloride reacts with quartz at 600" (50, + 2TiC13---t2TiOC1+ SiC1,) and the oxychloride is not volatile even under vacuum atred heat.294 X-Ray and infrared studies on addition compounds oftitanium tetrabromide with 1 : 4-dioxan, tetrahydrofuran, and tetra-hydropyran indicate that the ether oxygen atoms are involved in thebonding.The C-0-C ring stretching frequency in the infrared spectrum of284 C. L. Sieglaff and L. Eyring, J . Anzer. Chem. SOG., 1957, 79, 3024.285 J. W. Kury, 2.2. Hugus, jun., and W. M. Latimer, J . Phys. Chem., 1957,61, 1021.2 8 6 J. C. Warf and W. L. Korst, ibid., 1956, 60, 1590.E. J. Huber, jun., E. L. Head, and C. E. Holley, jun., ibid., 1957, 61, 1021.288 F. H. Spedding, R. J. Barton, and A. H. Daane, J . Amer. Chem. SOC., 1957,289 A. N. Nesmeyanov, 0. V. Nogina, and R. K. Freidlina, Bull. Acad. Sci. U.S.S.R.,290 K. C. Pande and K. C. Mehrotra, Chew. aptd Igtd., 1957, 114; %. aiiovg. Chew.,291 G. Lundgren, Arkiu Kemi, 1957, 10, 397.292 D. C. Bradley, R. Gaze, and W. Wardlaw, J., 1957, 469.293 W. C . Kreye and H.H. Kellogg, J . Electrochenz. SOL., 1957, 104, 50-4.294 H. Schafer, E. Weise, and F. Wartenpfuhl, Angew. Chem., 1957, 69, 479.79, 5160.1956, 3, 355.1957, 291, 97132 INORGANIC CHEMISTRY.dioxan is absent from the spectrum of the compound TiBr4-dioxan.,96 Therange of monocarboxylic esters which form addition compounds withtitanium tetrachloride has been extended to include n-butyl and isopentylformat e , qz-bu t yl chloroacet at e , and some esters of t richloroacet ic acid. 86The properties of zirconium tetrachloride in non-aqueous media POCl,,SOCl,, NOCl, and SeOC1, have been examined ; the compounds ZrCl4,2POC1,,ZrC1,,SOCl2, ZrC14,2NOC1, and ZrC1,,2SeOC12 are formed in solution. Withtypical bases, chlorozirconates such as (R4N) 2[ZrC16] are formed.WithSbCl, in phosphorus oxychloride medium, a compound ZrC14,SbC15 is ob-tained as its bright yellow solvate ZrCl4,SbC1,,2POC1,, and electrolysisindicates that the ions ZrC13+ and SbC1,- are present.297 When zirconiumand hafnium tetrachlorides are heated together with zirconium powder in avacuum at 400450", zirconium tetrachloride is reduced to the com-paratively involatile trichloride. Hafnium tetrachloride is not reduced, andcan be removed by sublimation. Zirconium trichloride dispropoitionates at550', yielding the tetrachloride again, and the process therefore has possi-bilities as a separation technique.298 Thorium metal dissolves in alkalichloride melts containing thorium tetrachloride, and at 500-900" Th4+ isreduced to Th2+.Equilibrium constants have been evaluated.299 There isalso chemical and magnetic evidence for the formation of thorium(I1) andthorium(1) iodides, as well as ThI,, in the reduction of ThI, by metallicthoriurn at 550°.300The extraction of zirconium nitrate from aqueous solutions by tributylphosphate (TBP) in the presence of uranyl nitrate, has been examined.Partition coefficients fall considerably on addition of kerosene to thesystem.301 Thorium nitrate is extracted into tributyl phosphate as adisolvate Th(N0,),,2TBP. It is more readily extracted than are thelanthanides, but less extractable than plutonium(1v) nitrate by a factor often.30,The Vanadium Group.-It has been found that vanadium pentafluoridecan be prepared, purified, and examined in all-glass systems provided thatmoisture and grease are rigidly excluded, and further physical propertieshave been determined.It has m. p. 19-6" (cf. NbF, 80-0", TaF, 91.5') andb. p. (extrapolated) 48.3". Vapour pressures have been recorded over mostof this range. The postulate of self-ioniz-ation 2VF5 __1L VF,+ + VF6- in the liquid is supported by specific con-ductivity (2.4 x 104 at 25'). Vanadium pentafluoride VF, is more effectivethan iodine pentafluoride IF5 as a fluorinating agent, and gives carbontetrafluoride on reaction with the tetrabromide or tetraiodide.,03 TheThe Trouton constant is 33.1.295 R. F. Rolsten and H. H. Sisler, J . Amer. Chem. SOC., 1957, 79, 1068, 1819.296 Yu. A. Lysenko, Zhuv. obshchei Khirn., 1956, 26, 2963, 3273.297 V.Gutmann and R. Himml, 2. anorg. Chem., 1956, 287, 199.298 I. E. Newnham, J . Amer. Chem. SOC., 1957, 79, 5415.299 M. V. Smirnov and L. Ye. Ivanovskii, Zhur. $2. Khim., 1957, 31, 802.soO G. W. Watt, D. M. Sowards, and S. C. Malhotra, J . Amer. Chem. SOC., 1957,301 I<. Alcock, (the late) F. C. Bedford, W. H. Hardwick, and H. A. C. McKay,302 E. Hesford, H. A. C. McKay, and D. Scargill, ibid., p. 321.303 H. C. Clark and H. J. Emel(.us, J . , 1957, 2119.79, 4908.J . Inorg. Nuclear Chern., 1957, 4, 100ADDISON AND GREENWOOD : THE TRANSITION ELEMENTS. 133species present in the vapour phase is the monomer VF5.304 Reaction ofvanadium tetrachloride with the amines dimethylamine and trimethylaminein 2-methylheptane solution gives mainly 1 : 1 adducts VCl,,NHMe, andVCl,,NMe,, which are stable up to 150" and are compounds of pentaco-ordinate vanadium.At high dimethylamine concentrations a base-catalysed elimination of hydrogen chloride occurs :VCI,,NHMe, __t VCI3,NMe, VCI,(NMeJ,The compounds VCl,(NHMe) ,,NH,Me, and VCl,(NMe,) , were also isolated.305Aliphatic amines react with niobium pentachloride. With dimethylamineat -78", elimination of HC1 occurs to give NbC1,(NhIe2)2,NHMe, whichloses a dimethylamine molecule in nitrobenzene solution. At room tem-perature, mono- and tri-methylamine give NbCl,(NHMe), and NbC1,,2NMe3 ;the former is largely dimeric in nitroben~ene.~06 The b. p.s of niobium andtantalum pentachlorides are 247.4" and 232.9", and the heats of vaporization12.6 and 13.1 kcal./mole, respectively.From a study of liquid-vapourequilibrium in this binary system, the relative volatility (TaC1,/NbC15) isfound to be 1.36 at atmospheric pressure over the full composition range.307The reductions of NbCl, to NbC1, and TaC1, to TaCl,, have been accomplishedby using hydrogen in an electric discharge. Tantalum tetrabromide isobtained in this way from the pentabrornide; the disproportionationTaBr, TaBr, + TaBr, occurs in a vacuum at 300". In contrast,niobium pentabromide is reduced under the same conditions to the di-br~mide.~O~ Contrary to previous belief, niobium pentaiodide begins to beformed from the elements at 250", and is formed rapidly at 280".309A double oxide U2Ta20, (formed by heating UO, with Ta,O,) has beenidentified from its X-ray diagram.310 The non-stoicheiometric compoundLi,,,V,O, is monoclinic; the structure is formed from VO, octahedra andVO, trigonal bipyramids grouped as sheets by sharing edges and corners.The sheets are held together by Li+ ions in octahedral inter-layer sites, andmore are located in additional tetrahedral positions.311 From the ultravioletspectra of the solutions, three peroxy-niobium complexes have been recog-nized in sulphuric acid solution.The Nb : H20, ratios are 2 : 3 in con-centrated acid, 1 : 2 in acid concentrations down to 60%, and 1 : 1 in diluteacid or neutral solution 312 Ternary phosphides and arsenides ofvanadium(v), Li,VP, and Li,VAs,, have been prepared which are analogousto the nitride Li,VN, recently described.313Published work on protactinium chemistry has been concerned largelywith separation processes.These are important as a means of isolating304 L. E. Trevorrow, J. Fischer, and R. K. Steunenberg, J . Amer. Chem. SOC., 1957,3 0 5 G. W. A. Fowles and C. M. Pleass, J., 1957, 1674.306 Idem, ibid., p. 2078.307 J. B. Ainscough, R. J. W-. Holt, and F. W. Trowse, ibid., p. 1034.308 V. Gutmann and H. Tannenberger, Monatsh., 1956, 87, 769.309 R. F. Rolsten, J . Anzer. Chem. SOC., 1957, 7'9, 6409.310 M. Gasperin, Compt. rend., 1956, 243, 1534.311 A. D. Wadsley, Acta Cryst., 1957, 10, 261.312 N. Adler and C. F. Hiskey, J . Amer. Chem. SOL, 1957, 79, 1827, 1831, 1834.31s R. Juza and W. Uphoff, Angew. Chem., 1957, 69, 96.79, 5167134 INORGANIC CHEMISTRY.protactinium, and also because 233Pa is an intermediate in the formation of233U from 232Th.The extraction of 233Pa from 1M-nitric acid solutioncontaining 2% of oxalic acid, into mono-, di-, and tri-butyl phosphates hasbeen compared. The distribution ratios (organiclaqueous phase) are 8.1,100.0, and 0.049 respectively, so that dibutyl phosphate is the active complex-forming agent. Protactinium is separated from thorium and fission productsby precipitation with niobium compounds; it is then separated from theniobium by extraction into dibutyl hydrogen pho~phate.~l~ Experimentshave also been described on the purification of 231Pa by chromatography andpaper electroph~resis,~~~ and on the solvent extraction of quadrivalent 233Pawith isobutyl methyl ketone and tributyl phosphate.316 Concentration of231Pa can be effected by recycling through Dowex-1 resin.After initialsorption from hydrochloric acid solution, it is eluted with an HC1-HFmixture. Addition of aluminium chloride or boric acid to the effluentrenders the protactinium readsorbable by the resin. Re-elution withHCI-HF mixture then produces a marked concentration of the pro-ta~tinium.~~' For exhaustive chemical study, the long-lived 231Pa is to bepreferred to the more active 233Pa. Only very small quantities have hithertobeen separated. One of the best sources has been found to be the residuesfrom the processing of uranium minerals, which are available in ton quantitiesand contain 0.1-0.3 p.p.m.of protactinium. A method has been describedfor the recovery of more than 90% of this in high purity. It consistsessentially in dissolution of the source material in acid, concentration ofprotactinium by precipitation with an internal silicate carrier, and finalisolation by ion e~change.~1* Protactinium is now becoming available inlarger quantities, and rapid developments in its chemistry are expected inthe near future.The Chromium Group.-Aqueous chromic acid solutions in closed con-tainers at 300-325" evolve oxygen. At oxygen pressures of 50-200 atm.the solid decomposition products are CrO, and HCrO, [or CrO(OH)]. Thelatter is dehydrated to Cr20,; 319 its structure consists of distorted (CrOJ9-octahedra, each sharing six edges with coplanar octahedra to form continuoussheets, which are stacked so that oxygen atoms are superimposed, withhydrogen ions between.These symmetrical hydrogen bonds are uniqueamong known isoformular stru~tures.~~O When heated in a melt ofpotassium hydroxide and water (5 : 1 wlw) and in the absence of oxygen,potassium chromate forms a clear green solution which contains quinque-valent chromium as the hypochromate ion Cr02-.321 The structure of blue" perchromic acid " is now resolved in favour of CrO, by spectrophotometryof aqueous methyl-alcoholic solutions and of aqueous solutions,322 and314 A. J. Fudge and J. L. Woodhead, Chew. and I n d . , 1957, 1122.315 M. Lederer and J. Vernois, Compt. rend., 1957, 244, 2388.316 G. Bouissibres and J. Vernois, ibid., p.2508.317 M. K. Barnett, J. Inorg. Nuclear Chem., 1957, 4, 358.318 M. L. Salutsky, K. Shaver, A. Elmlinger, and M. L. Curtis, ibid., 1966, 3, 289.ylo B. J. Thamer, R. M. Douglass, and E. Staritzky, J . Arne?. Ghem. SOC., 1957,K. M. Douglass, Acta Cryst., 1957, 10, 423.321 N. Bailey and M. C. R. Symons, J., 1957, 203.a22 D. F. Evans, ibid., p. 4013.79, 547ADDISON AND GREENWOOD: THE TRANSITION ELEMENTS. 135solutions in ethyl acetate.323 The predominant equilibrium in dilute aqueoussolution isA stable 1 : 10-phenanthroline-perchromic acid complex is known, theanalysis of which also supports the formula CrO,. The brown peroxideCr0,,3NH3 is a &peroxide of quadrivalent chromium.322 The products ofthe chromium trioxide-liquid ammonia reaction are complex ; they includeammonium chromate, hexamminochromium(II1) chromate, and an ammino-and a nitro-ammino-chromium(rI1) chromate polymer.324 About one quarterof the chromium(v1) is reduced to chromium(II1).An oxalato-complex of molybdenum, (NH4)4[M~(C204)4], 8H,O, has nowbeen obtained by electrolytic reduction of an ammonium molybdate solutionin the presence of oxalic acid.The product is soluble in water, insoluble inorganic solvents, and chars at 60". A carbonato-complex K,[Mo(CO,)~] hasbeen prepared by similar methods.325 The spectra of heteropolytungstatescontaining cobalt(II), cobalt(m), or manganese(1v) as central ions indicatethat the central structural unit is a tetrahedron MO,, not MO,.The polyanion [co111(w20~)6]g- is therefore now represented as[CO~~~O~(W,,O,,)]~-.~~~ Binary tungstates Fe,Mnl-zW04, where x = 0-25,0.41, and 0.66 have been synthesized and their lattice constants deter-mined.327 Non-stoicheiometric solids of the formula Cu,WO,, where x liesbetween 0.26 and 0.77, are prepared by electrolytic reduction of aCuW0,-WO, melt at 800".These materials are copper analogues of thealkali tungsten bronzes.328 By mass-spectrometric analysis, the polymericgaseous species formed during sublimation of MOO, have been identified asMo,O,, Mo,O,,, and M05015; corresponding species are formed in thesublimation of wo,.329Gaseous fluorine acts upon molybdenum hexacarbonyl in two differentways depending on temperature. Above 50°, a vigorous reaction givesMoF, and COF,.At -75", an olive-green solid results, which when heatedat 170" gives a distillate of the new pentafluoride MoF, (a yellow solid,m. p. 64") and a residue of MoF,.~~O Complex fluorides of quinquevalentmolybdenum and tungsten, involving the ions MoF,- and WF,-, have beenobtained from the hexafluorides by the reducing action of potassium iodidein liquid sulphur dioxide.=1The uranium hydride UH, has a dissociation pressure of 1 atm. at 430".Pressure-composition isotherms have now been measured at pressures up to65 atm. and temperatures up to 650". The heat of formation of UH, is- 30.3 kcal./mole, and is almost independent of temperature.332 HydrogenHCr0,- + 2H202 + H+--- CrO, + 3H20323 A. Glasner and M. Steinberg, J., 1957, 2569.324 R.S. Drago and H. H. Sisler, J . Amer. Chem. SOL, 1957, 79, 1811; S. I. Tannen-baum, R. S. Drago, and H. H. Sisler, ibid., p. 1815.325 M. C. Steele, Austral. J . Chem., 1957, 9, 367, 368.328 Y. Shimura and R. Tsuchida, Bull. Chem. SOC. Japan, 1957, 30, 502.327 Yu. P. Simanov and R. D. Kukshakova, Zhur. $2. Khim., 1957, 31, 820.32* I,. E. Conroy and M. J. Sienko, J . Amer. Chem. SOL, 1957, 79, 4048.329 J. Berkowitz, M. G. Inghram, and W. A. Chupka, J. Chewz. Phys., 1957, 28,330 R. D. Peacock, P ~ o c . Chern. Soc., 1957, 69.331 G. B. Hargreaves and R. D. Peacock, J., 1957, 4212.832 G. G. Libowitz and T. R. P. Gibb, jun., J. Phys. Chem., 1957, 61, 793.S42; 27, 85136 INORGANIC CHEMISTRY.selenide reacts with uranium tetrachloride at 620" to give a compoundUse,, which magnetic and chemical properties suggest is a polyselenide ofquadrivalent uranium.333 When this is heated in a vacuum at 580°, thediselenide Use, is obtained.334 A uranyl silicate hydrate (U0,)2Si04,3H20results from reaction of U02F2 solution with silica at 300°.335 Themechanism of hydrolysis of the U4+ ion has been studied by calorimetricmeasurements 336 on uranium tetrachloride, and by electrometric titrationin SM-sodium perchlorate solutions.337 The latter data are explained onthe basis of a mononuclear reaction U4+ + H20 + U(OH)3+ + H+, and apolynuclear product U[(OH),U],4*n.The hydrolysis of the uranyl ion isinterpreted in terms of two reactions, leading to the formation of monomericUO,*OH+ and the dimeric U02*U032+ ions.336During attempts to prepare uranyl alkoxides, it was observed that thedisproportionation 3UO,(OR), + U,O,(OR), + UO(OR), occurredreadily. This is unusual in view of the stability of the uranyl group.338The chemistry of uranium(v) alkoxides has been developed.From analcoholic solution of the thionyl chloride complex UCl,,SOCl,, the alcoholateUOCl,,EtOH can be isolated, and this is probably an intermediate in thereaction of the alcoholic solution with pyridine, when (C,H,N),,UOCl, isproduced. Reaction of this with alcohol and ammonia affords a novelmethod for the preparation of the penta-alkoxides U(OR),, which are surpris-ingly resistant to disproportionation and distil unchanged. The pentaiso-propoxide is a golden, crystalline Uranium(v) ethoxide behaves asan acid, and reacts with sodium, calcium, or aluminium ethoxides to givepounds of the type U(OR),Cl, U(OR),Cl,, and U(OR)&l, are produced byreaction of U(OR), with hydrogen chloride.340 Uranium(v1) ethoxide, adark-red distillable liquid, is formed by oxidation of Na[u(OEt),] withbenzoyl per~xide.~~l The structure of a range of penta-rt-alkoxides U(OR),,where R = Me, Et, Prn, Bun, TZ-C,H~~, has been examined.Except for thepentamethoxide, which is trimeric, they are all dimeric like the correspondingquinquevalent niobium and tantalum complexes.342The Trans-uranium Elements.-Reviews published during the year in-clude an account of the work carried out at the Radiation Laboratory,University of California, on the trans-curium elements.This deals chrono-logically with the development of the work, and the technical difficultiessalt-like compounds Na[U(OEt),], Ca[U(OEt)6]zY and AI[U(OEt)J,. COm-333 P. Khodadad and J. Flahaut, Gompt. rend., 1957, 244, 462.334 P. Khodadad, ibid., 245, 934.335 W. L. Marshall and J. S. Gill, J . Amer. Chem. SOL, 1957, 79, 1300.336 J. A. Hearne and A. G. White, J., 1957, 2081, 2168.357 S. Hietanen, Acta Chem. Scand., 1956, 10, 1531.338 D. C. Bradley, Amar K. Chatterjee, and Amiya K. Chatterjee, Proc. Chem. Soc.,3S9 D. C. Bradley, B. N. Chakravarti, and A. K. Chatterjee, J . Inorg. Nuclear Chem.,340 R. G. Jones, E. Bindschadler, D. Blume, G. Karmas, G. A. Martin, jun., J. R.341 R. G. Jones, E. Bindschadler, D. Blume, G. Karmas, G.A. Martin, J. R. Thirtle,342 D. C. Bradley and A. K. Chatterjee, J . Inorg. Nuclear Chem., 1957, 4. 279.1957, 260.1957, 3, 367.Thirtle, and H. Gilman, J . Amer. Chem. Soc., 1956, 78, 6027.1;. A. Yeoman, and H. Gilman, ibid., p. 6030ADDISON AND GREENWOOD : THE TRANSITION ELEMENTS. 137encountered.343 The chemistry of the trans-uranium elements up tomendelevium has been reviewed from the point of view of preparation,separations, and physical proper tie^.^^ The crystal structures of theactinide elements (and manganese) have been correlated; the existence ofcomplex structures may be related to the possibility of Jahn-Teller dis-tortions occurring in the body-centred cubic lattice.345 The principalspectroscopic and magnetic properties of uranyl-like ions are due to theadditional electrons in the 5f shell (one in neptunyl, two in the plutonyl ion,etc.) , and the absorption spectra, microwave resonance data and magneticsusceptibility of the plutonyl ion have been interpreted on this basis.346Neptunium metal has density 20.2 g./c.c.at 20"; the specific heat is0.0319 cal. g.-l deg.-l over the range 29-99', and this lies between knownvalues for uranium and plutonium. The metal is much harder than uranium,the ultimate tensile strength being about 80-90 tonslsq. Quadri-valent uranium rapidly reduces plutonium to the plutonium(II1) state innitric acid solution :3U4+ + ~ P u O , ~ + 3- 2H20 + 3U02+ + 2Pu3+ + 4H+This has applications in liquid-liquid extractions for uranium-plutoniumseparations, since Pu3+ concentrates in the aqueous phase.348 Plutonium(1n)nitrate is relatively inextractable by tri-n-butyl phosphate, but plutonium(1v)and plutonyl nitrates are readily extracted ; the compounds Pu(N0,),,2TBPand PuO,(NO,) ,,2TBP appear to be formed.Plutonium (like americium)can therefore be rendered extractable or inextractable by reduction oro x i d a t i ~ n . ~ ~ The magnetic susceptibility of the five plutonium(1v) com-pounds Pu (SO,) ,,4H20: Rb4Pu(S03,,2H ,O, Pu ( C204) 2,6H 20, (Me,N) iPuCl,,and PuF, has been measured. In each case a large departure from theCurie-Weiss law is observed.350 The plutonium(1v) alkoxide Pu(OPri),,mixed with its addition compound with pyridine, has been prepared fromthe complex (C,H,N) 2PuC1,.Crystallization of the isopropoxide frompropan-2-01 gives an emerald-green solvate Pu(OPri),,PriOH, analogous tothe zirconium, hafnium, and cerium compounds. Pure plutonium iso-propoxide sublimes at 220'/0-05 mm.351 The ions Pu3+, Pu4+, and PuOa2+form 1 : 1 chelate complexes with ethylenediaminetetra-acetic acid. Inthe first two cases, complexes with Pu : edta ratio of 2 : 1 are also formed.352The relationships between the various valency states of americium havebeen further studied. Americium-(v) and -(vI) undergo self-reduction, andkinetics have been studied in perchloric acid solution. Americium(II1) doesnot appear during simultaneous self-reduction and it is suggested thata43 S. G. Thompson, Sveszsk kern. Tidskr., 1957, 69, 359.344 P.Graf, Chimia (Switz.), 1957, 11, 57.345 L. E. Orgel, J . Phys. and Chem. Solids, 1957, 3, 50.346 J. C. Eisenstein and M. H. L. Pryce, Proc. Roy. Soc., 1956, A , 238, 31.a47 V. W. Eldred and G. C. Curtis, Nature, 1957, 179, 910.3a8 J. Rydberg, J . Inorg. Nuclear Chem., 1957, 5, 79.G. F Best, H. A. C. McKay, and P. R. Woodgate, ibid., 1957, 4, 315.W. B. Lewis and N. Elliott, J . Chern. Phys., 1957, 27, 904.351 D. C. Bradley, B. Harder, and I;. Hudswell, J., 1957, 3318.s62 J. K. Foreman and T. D. Smith, ibid., pp. 1762, 1758138 INORGANJC CHEMISTRY.americium(v1) reacts with the americium(1v) formed to give americium(v) .353The curium oxide CmO, is known; curium tetrafluoride has now been made,and in this compound the curium is also unequivocally quadrivalent.244Cm(half-life 18.4 years), in the form of CmF,, was treated with gaseous fluorineat 300-400”. The X-ray data show that CmF, has the same monoclinicstructure as have UF,, NpF,, PuF,, and AmF,.354 The existence of thiscompound shows that the stability of the half-filled 5f shell in curium ismarkedly less than that of the half-filled 4f shell in gadolinium, and em-phasizes that predictions of the valency of trans-uranium elements on thebasis of lanthanide analogy should be treated with caution. The separationof berkelium as the quadrivalent species has been described. Nitric acidsolutions being used against a ut-heptane solution of di-2-ethylhexyl hydrogenphosphate, the distribution coefficient for berkelium(1v) is lo6 times greaterthan for berkelium(II1) or curium(rI1).Under the oxidizing conditions used(KBrO, in 10~-HNO,), americium remains in the AmIII state.355 Theisotope 253Fm has been identified among the products of reaction of 252Cfwith 40 Mev a-particles. I t has a 4.5 day half-life, and is thus the longest-lived fermium isotope known (compare 250Fm 30 min., ,51Frn 7 hours,252Fm 30 hours). Only the undiscovered 257Fm is expected to have a longerhalf-life.356 Details are now available of the work leading to the preparationof a few atoms of element 102, carried out co-operatively by the UnitedStates, Great Britain, and Sweden. The name “nobelium” has beensuggested in honour of Alfred Nobel, and of the Institute at which the workwas carried out. Element 102 was made by bombarding 2MCm with90 Mev ions of 13C4+. The isotope produced had mass 251 or 253 (probablythe latter), formed by the nuclear reaction 244Cm(13C, 4 ~ ~ ) ~ ~ ~ 1 0 2 .Theproduct was collected by recoil; a new a-activity of 8.5 Mev was detected,though only 17 events of this energy were observed. When the productswere eluted from a cation-exchange column, the 8-5 Mev a-activity appearedat the position expected for element 102.357The Manganese Group.-Reduction of potassium permanganate bypotassamide, and the disproportionation of potassium manganate in liquidammonia, are of interest for their analogy with corresponding reactions inwater.358 From consideration of a thermodynamic cycle involving therhenide ion Re-, it is deduced that for stability this ion must exist as anoxygenated complex such as Re(H,0)4-.359 A simple technique wherebymetal oxides and carbon tetrachloride are heated at 400” in a sealed tube togive the anhydrous chloride has been applied to the preparation of tech-netium and rhenium compounds.The technetium product is a blood-red353 G. R. Hall and T. L. Markin, J . Inorg. Nuclear Chem., 1957, 4, 296; see alsoS. R. Gunn and B. B. Cunningham, J . Amer. Chem. Soc., 1957, 79, 1563.354 L. P. Asprey, F. H. Ellinger, S. Fried, and W. H, Zachariasen, J . Amer. Chewi.SOC., 1957, 79, 5825.355 D. F. Peppard, S. W. Moline, and G. W. Mason, J . Inorg. Nuclear Chem., 1957,356 S. Amiel, Phys. Rev., 1957, 105, 1412.357 P. R. Fields, A. M. Friedman, J. Milsted, H.Atterling, W. Forsling, L. W. Holm,and B. Astrom, ibid., 107, 1460; see also H. A. C. McKay and J. Milstead, Nature,358 T. Inoue, S. Takamoto, and S. Kurokawa, J . Chenz. SOC. Japan, 1951, 78, 274.359 J. W. Cobble, J . Phys. Chem., 1957, 61, 727.4, 344.1957,180, 1010, 1012ADDISON AND GREENWOOD : THE TRANSITION ELEMENTS. 139powder TcCl,, whereas with rhenium the pentachloride ReC1, is formed.360Quinquevalent rhenium has a strong tendency to disproportionate, andpreparative methods which employ oxidizing agents (e.g., F, or BrF,) areunsuccessful. The complex K[ReF,], which is very sensitive to traces ofmoisture, has been prepared by the action of potassium iodide on ReF, inliquid sulphur dioxide, iodine being released.361 A simple method for thepreparation of the hexachlororhenate(rv) complex K2[ReC16] involvesreduction of the per-rhenate with chromous chloride in concentrated hydro-chloric acid; K,[ReBr,] is prepared by the same method.362The Iron Group.-When a stream of nitrogen containing iodine vapouris passed over ferrous iodide at 500-560", the vapour phase then containsthe species FeI, (which is unstable in the solid state) and Fe,16.363 Equi-librium vapour pressures for the ferrous bromide-water system over thetemperature range 2 5 4 0 0 " represent hydrates of FeBr, with 1, 2, and4H,O; in the absence of oxygen no appreciable amounts of hydrogenbromide were observed in the vapour throughout this temperature range.364Ruthenium tetroxide in aqueous hydrofluoric acid can be reduced byhydrogen peroxide to the RuIV state.Evaporation of the resulting redsolution gives a black solid of composition [Ru(H,O) 50H]F,.365 An interest-ing aspect of the equilibrium RuIV +- RuIII concerns the complexK,[Ru(OH)CI,] ; treatment of this with reducing agents (e.g., TiC1,) givesK,[Ru(H,O)C~,].~~~ Nitrosyl-ruthenium chemistry has been further studiedand the compounds examined include (RuNO)(NO,),, 2 and 3H,O,(RuNO)(OAc),, Na[(RuNO)(OAc),], H,[(RuNO)(C,O,),] and its ammoniumand magnesium salts.367 Osmium forms an octavalent oxyfluoride Os0,F2by treatment of osmium metal sponge with an oxygen-fluorine mixture inthe volume ratio 2 : 1. It is an orange solid, melting at 170-172" to a redliquid, and is the parent of the trifluoroperosmates M[OsO,F,] (whereM = K, Cs, Ag).An oxychloride OsOCl, has also been prepared. Theseare the first true simple oxyhalides of osmium to be reported. Attempts toprepare the simple or complex oxyfluorides of ruthenium were un-successful.368The Cobalt Group.-Univalent cobalt has been obtained in the form of itsdipyridyl complex. The perchlorate [Co(dipy),] (C10,),,3H20, in suspensionin aqueous ethanol, was reduced with sodium borohydride. Evaporation(in an inert atmosphere) of the deep blue solution obtained gave dark bluecrystals of the compound [Co(dipy),]ClO,. It is slightly soluble in water,and is oxidized by oxygen to the [Co(dipy)J2+ i0n.~6~ The properties ofcobalt(Ir1) acetate differ from those of many simple cobaltic salts, which3130 K.Knox, S. Y. Tyree, jun., R. D. Srivastava, V. Norman, J. Y. Bassett, jun.,361 R. D. Peacock, J., 1957, 467.362 V. W. Meloche and R. Martin, J . Amev. Chem. SOC., 1956, 78, 6965.363 H. Schafer and W. J . Hones, Z . anorg. Chem., 1956, 288, 64.Y B 1 N. W. Gregory, J . Phys. Chem., 1957, 61, 369.ae5 M. L. Hair, M. A. Hepworth, and P. L. Robinson, J., 1957, 1927.3 B 6 N. K. Pshenitsyn and S. I. Ginzburg, Zhur. neorg. Khin~., 1957, 2, 112.367 0. Ye. Zvyagintsev and S. M. Starostin, ibid., p. 1281.36* M. A. Hepworth and P. L. Robinson, J . Inorg. Nuclear Chem., 1957, 4, 24.368 A. A. VICek, Nature, 1957, 180, 753.and J. H. Holloway, J . Amer. Chem. Soc., 1957, 79, 3358140 INORGANIC CHEMISTRY.decompose rapidly in water. It is stable at room temperature but de-composes at loo", evolving acetic acid.Solutions in acetic acid or ethylalcohol are stable, the oxidizing power remaining unchanged for long periods.In aqueous solution slow hydrolysis to cobaltic hydroxide occurs, but additionof dilute mineral acids causes rapid reduction to the cobaltous state.370The kinetics of this spontaneous reduction from cobalt (111) to cobalt(11) hasbeen examined with cobalt (111) perchlorate s0lutions.3~~ Very few examplesexist of cobalt(I1z) complexes having the phosphate group as ligand.Two such compounds have recently been prepared, the neutral[Co(NH3),P0,],2H,0 (in which the phosphate group is bidentate) and[Co(NH,),HP04],P0,. It is significant that attempts to prepare phosphato-pentamminocobalt (111) complexes were unsuccessful.372 The alkali-metalsalts M,[CoF,] are strongly paramagnetic (5.2 B.M.), whereas the ion[co(H20),l3' is diamagnetic.The magnetic moment of hydrated cobaltfluoride, CoF3,3.5H,0, represented as [CoF,,3H20],0.5H,0, is 4-47 B.M.This is regarded as indicating that when three of the F- ions in [CoF,I3- arereplaced by water molecules, the ligand field is still not sufficient to bringabout any appreciable degree of spin coupling, a result which is in contrastto that for the complex [COF,(NH,),].~~~A stable rhodium perchlorate, Rh(C10,),,6H20, has been prepared byreactbn of the trichloride with perchloric acid. It is crystalline and water-soluble. The six water molecules are probably co-ordinated to the rhodiumcation, and can be replaced by other ligand~.~'~ When iridium powder isheated with strontium oxide at 1200" in air, a double oxide Sr,IrO, is formed,isotypic with K,NiF,.No perovskite-type compound could be obtained inthis system.375The Nickel Group.-Consideration of the magnetic moments and re-flection spectra of a number of nickel(I1) (mainly triaminotriethylamino)complexes indicates that many which are apparently tetrahedral are in factoctahedral.376 Nickel@) complexes with 1 : 2-diethylthio- and 1 : 2-di-methylthio-ethane (which act as a chelate group by virtue of the twosulphur atoms) have been prepared. With nickel halides, dihalogeno-complexes (Ni[R*S*(CH,) ,*SR] 2Hal,} are formed, but nickel perchlorate givesthe tris-chelate (Ni[R~S*(CH,),*SR],}(C102)a.In all cases the nickel atom isoctahedrally b0nded.3'~ Several compounds of the type Ni(PX,), are al-ready known, but the first synthesis of such a compound by direct reactionwith metallic nickel is now reported. Methyldichlorophosphine was refluxedthrough a column of nickel turnings; on cooling, the compound Ni(MePCl,),crystallized. It is soluble in organic solvents, decomposes at 170" and isonly stable while protected from the atmosphere.378 The blue compoundNi(DH\,,2HCl (where DH, = dimethylglyoxime) formed by addition ofs70 J . A. Sharp, J., 1957, 2030.372 S. S. Daniel and J. E. Salmon, J., 1957, 4207.a75 H. C. Clark, B. Cox, and A. G. Sharpe, ibid., p. 4132.s74 G. H. Ayres and J. S. Forrester, J . Inorg. Nuclear Chem., 1957, 3, 365.375 J.J. Randall, jun,, L. Katz, and R. Ward, J. Amer. Ghem. SOL, 1957, 79, 266.376 R. W. Asmussen and 0. Bostrup, Acta Chem. Scand., 1957, 11, 1097.s77 R. Backhouse, M. E. Foss, and R. S. Nyholm, J.. 1957, 1714.378 L. D. Quin, J . Amer. Chem. SOC., 1957, 79, 3681.J . H. Baxendale and C. F. Wells, Trans. Favaday SOC., 1957, 53, 800ADDISON AN11 GREENWOOD: THE TRANSITION ELEMENTS. 141hydrogen chloride to the red nickel derivative Ni(DH) , has a magneticmoment (3.07 B.M.) compatible with either tetrahedral or octahedral con-figuration. However, its solution in acetone reacts only slowly with silvernitrate, and has a slight conductivity. It is probably an octahedral complex[Ni(DH,) ,Cl,] with two trans-chlorine atoms.The palladium complex[Pd( DH ,) Cl,] is not analogou~.~ 79 The bis-(N-me thylsalicylaldimine) -nickel(I1) complex is diamagnetic in the solid state, but paramagnetic insolution in benzene or chloroform. Although conversion from planar intoa tetrahedral configuration might account for this, solvent molecules mayco-ordinate to the metal and change its magnetic properties. Accordingly,measurements have been made on the complexes (from bis-N-ethyl tobis-N-decyl) in the molten state, and paramagnetism (O%--1-15 B.M.) isfound in the molten state as well as in solution.380 However, dipole momentsmeasured in benzene or chloroform solution do not support a tetrahedralstructure, and the paramagnetism has been explained in terms of anequilibrium involving outer-orbital sp2d planar config~ration.~*l Nickel(I1)bisacetylacetone, shown recently to be trimeric in the solid state, has beenstudied in the vapour by electron diffraction.The four oxygen atoms aresquare planar round each nickel atom, in spite of the paramagnetism of thecompound (3.2 B.M.).382Belucci’s salt K4[Ni2(CN)J reacted with sulphur nitride (N4S4) in alcoholicsolution to give a blood-red solution from which a stable orange complexwas isolated which appeared by analysis to be K[Ni(CN),(NS),]. However,its infrared spectrum indicated that an N-H bond was present in thecomplex; the anion therefore has structure (26) or its tautomeric forms, andHIN=S\ ,N-S,~i’ I I Nix INZC K S = N s-y’ S=N? NEC, N-SH( 2 6 ) ( 2 7 )the nickel atom is formally bivalent.3s3 In the interesting series of com-pounds M(NS), formed by N4S4 with transition metals, there has beendifficulty in envisaging satisfactory electronic structures for the two planarN2S, chelate groups.The problem is now modified by the observation(by analysis, spectroscopy, isotope exchange, and proton-spin resonance)that the nickel compound contains two hydrogen atoms, and is in factNiN4S4H2. Since this is formed from N,S, + NiC1, in ethanol, the hydrogenmust come from the solvent ; no product is obtained when carbon disulphideor benzene is used as solvent. The structure (27) may now represent thecompound, with nickel in the +Z oxidation state.384Further examination of the physical properties of the nickel cyanide-ammonia clathrate compound Ni(CN) $H,,C,H, has shown that, contraryL.Sacconi, R. Cini, and F. Maggio, J . Amw. Chem. Soc., 1957, 79, 3933.379 A. G. Sharpe and D. B. Wakefield, J., 1967, 496, 3323.381 L. Sacconi, P. Paoletti, and G. Del Re, ibid., p. 4062.882 S. Shibata, M. Kishita. and M. Kubo, Nature, 1957, 179, 320.383 J. Weiss, 2. Naturforsch., 1957, 12b, 481.a*4 T. S. Piper, Chem. and Ind., 1957, 1101; see also E. Fluck and M. Goehring,2. Natuvforsch., 1956, l l b , 756142 INORGANIC CHEMISTRY.to previous belief, benzene can be removed rapidly in vacuum at 40-60".X-Ray powder photographs taken during this process reveal progressivechanges in unit-cell dimensions, but no breakdown of the lattice.385 Nickelcyanide forms two ammines; with concentrated ammonia solution theunstable Ni(CN)2,4NH,,2H,0 is formed, which on exposure to air gives thepale blue, stable compound Ni(CN) 2,NH3,H20.386 The products of reactionof nickel with sodium hydroxide, in a vacuum and at temperatures nearlOOO", are numerous; they include hydrogen, water, sodium oxide, nickeloxide, sodium nickelate, and sodi~rn.~8'In the chloro-bridged dirneric complexes [L2Pd2C1,], where L is an amine,a tertiary organic phosphine, arsine, or stibine, or a dialkyl sulphide, selenide,or telluride, two well-graded series are found depending upon the positionof L in the Periodic Table. The reaction with monoamines (am)[L,Pd,CI,] + 2am Z[L,am,PdCI,]varies with the identity of L.The mononuclear complex can be isolatedonly when the donor atom in L is phosphorus or arsenic.When the donoris sulphur, selenium, or tellurium, the product disproportionates at roomtemperature :Z[L,am,PdCI,] L,PdCI, + am,PdCIand when L is an olefin, immediate decomposition O C C U T S . ~ ~ ~ A number ofcomplex compounds of null-valent palladium with phosphorus donors havebeen prepared. Starting with Pd(R*NC),, three types of complex have beenisolated: (R*NC)L,Pd, PdL,, and PdL,, where L = triarylphosphine or tri-aryl phosphite. Compounds of the last class, e.g., (Ph,P),Pd, are largelydissociated in benzene to give (Ph3P),Pd.389 Palladium difluoride has beenprepared in the pure state by reaction of palladium(I1) iodide with brominetrifluoride. This gives an addition product PdF,,BrF,, which when heatedto 220" at atmospheric pressure with selenium tetrafluoride leaves the paleviolet PdF2.390 Spectrophotometric studies 391 on nitrobenzene solutionscontaining [PdBr4l2- and Br- ions give evidence of the formation of unstablehexabromopalladate (11) ion [PdBr6l4-.The discovery of a new valency state of platinum in a simple compoundis of obvious importance.Platinum hexafluoride has been formed byreaction of fluorine vapour (300 mm. pressure) with a platinum filament,very close to which was a liquid-nitrogen cold finger. The major productwas the involatile PtF,, but a more volatile fraction of PtF, (1.4 g. from10 g. of platinum) collected on the cold finger. Solid platinum hexafluorideis dark red, m. p. 56.7", and its vapour resembles that of bromine. The solidis isostructural with OsF, and IrF,.3923s5 E.E. Aynsley, W. A. Campbell, and R. E. Dodd, Proc. Chem. Soc., 1957, 310.386 E. E. Aynsley and W. A. Campbell, J., 1957, 4137.38' D. M. Mathews and R. F. Kruth, I n d . Eng. Chem., 1957, 49, 55.388 J. Chatt and L. M. Venanzi, J., 1957, 2351, 2445.3s9 L. Malatesta and M. Angoletta, ibid., p. 1186.390 N. Bartlett and M. A. Hepworth, Chem. and Ind., 1956, 1425.301 C. M. Harris, S. E. Livingstone, and I. H. Reece, Austral. J . Chew., 1957, 9, 282.392 B. Weinstock, H. H. Claassen, and J. G. Malm, J . Amer. Chem. SOC., 1957,79,5832ADDISON AND GREENWOOD : THE TRANSITION ELEMENTS. 143By reduction of ethylenediamine complexes of platinum(I1) with potass-amide or potassium metal in liquid ammonia, a series of compounds has beenprepared in which the platinum atom is in the (+1) or the (0) valent state;eg., reduction of [Pt(en),]I, with two equivalents of potassium gives[Pt (en) 2]0.393 An X-ray examination of single crystals of the compound[Pt(NHJ4(CH,*CN),]C1, has revealed that the four NH, groups lie in a planeabout the Pt atom, while the trans-acetonitrile molecules appear to lieparallel to this plane.They are therefore not co-ordinated through thenitrogen atom lone electron pairs {as in [Pd(C,H,-CN) ,C12]) and x-bondingof the C-N group is probably involved, resembling that in the olefincomplexes.394 Interest in the structure of Wolffram’s red saltPt (C2H,*NH2),C1,,2H20 has been maintained because of the apparent ter-valency of the platinum atom.From polarized absorption spectra it appearsthat the true structure may be [Pt(Et*NH2),C12] [Pt(Et*NH,),]Cl4,4H2O.The deep colour is attributed to a band which is strongly polarized along theneedle axis, owing to the presence of infinite chains -Pt2+-Cl-Pt4+-Cl-Pt2+-C1-parallel to this axis.395 Improved synthetic routes have beenCI ’ v ‘PPr,(20, CN ( 2 9 )devised for the preparation of octahedral platinum complexes, such as[PtBrClI(py) (NO,) (NH,)] containing five or six different ligands. Use ismade of the trans-effect of the ligands c0ncerned.~96 The two isomers ofthe binuclear platinous complex (28) were believed to represent cis- andtrans-positions of the CN groups about the PtS,Pt ring.The discovery thatsilver thiocyanate consists of infinite chains 409 in which bonding occursthrough nitrogen atoms has led to re-examination of structure (28). Infraredspectra and X-ray analysis now show that the a-isomer has structure (29).The two isomers of the tetrathiocyanate (PPrJ2Pt,(SCN), may also be ofthisReduction of cis- or trans-(PEt,) ,PtCl, gives a remarkable volatile chloro-hydride of formula (PEt,),PtHCl, m. p. 82”. It is soluble in all organicsolvents, distils unchanged at 130”/0.01 mm., and is colourless and dia-magnetic. It is the first definite example of a transition-metal hydridewhich exists as discrete molecules, and without carbon as a ligand atom.398The Copper Group.-Copper metal reacts vigorously with a mixture ofliquid dinitrogen tetroxide and ethyl acetate, and the compoundCu(N0,) ,,N,04 crystallizes from solution.Heating of this at 85-100”s93 G. W. Watt, R. E. McCarley, and J. W. Dawes, Amer. Chem. SOC., 1957, 79, 5163.394 C. M. Hams and N. C. Stephenson, Chem. and Ind., 1957, 426.395 S. Yamada and R. Tsuchida, Bull. Chem. SOC. Japan, 1956, 29, 894.396 L. N. Essen and A. D. Gel’man, Proc. Acad. Sci. U.S.S.R., 1956, 108, 309;s97 J. Chatt, L. A. Duncanson, F. A. Hart, and P. G. Owston, Nature, 1958,181, 43.Zhur. neorg. Khim., 1956, 1, 2475.J. Chatt, L. A. Duncanson, and B. L. Shaw, Proc. Chenz. SOC., 1957, 343144 INORGANIC CHEMISTRY.leaves the anhydrous nitrate Cu(NO,),, which is blue. When this is heatedat ~ ~ - 2 0 0 " it sublimes, and copper nitrate is found to be monomeric inthe gaseous phase.These surprising properties indicate that the nitrategroup is capable of a type of bonding not hitherto realized.399 Cuprous,argentous, and aurous ions form complexes with (o-diethylphosphinophenyl) -diethylarsine; the cuprous and aurous complexes have configuration (30) ;I- -+they have additional interest in comparison with the analogous o-phenylene-bisdirnethylarsine complexes, since they should show cis-trans-isomerism ifthe metal has planar configuration, or optical activity in the case of tetra-hedral configuration. X-Ray analysis of the iodides shows them to havetetrahedral configuration, but in spite of this no resolution was p0ssible.~00The variation in magnetic susceptibility of the copper(I1) salts of C,, C,, C,,,C,,, and C,, fatty acids is anomalous in that antiferromagnetic rather thanCurie-Weiss characteristics are observed. It is concluded that the salts havebasically identical structures [CU,(R*CO,)~(H~O), or ,] involving a weakCu-Cu bond.401 Electron-diff raction measurements on bisacetylacetone-copper(I1) (by evaporation of the solid at 170") confirm that in the vapourthe chelate has a square planar configuration (Cu-0 distance 1.95 A), inagreement with X-ray investigation^.^^The analogoussilver and gold compounds have discrete linear complex ions [NC-M-CN]-,but in the copper compound spiral polymer chains [Cu(CN),]; are formed,as in (31).This is claimed to be the first time that the copper(1) atom hasThe cyanide KCu(CN), has an unusual crystal structure.been proved to be 3-co-ordinate. The [Cu(CN),]- units are held together bya Cu-N bond (compare the A g N bond in AgSCN 409), the length of which,2.05 A, is somewhat longer than the value expected for a Cu-N singlebond.*03 The infrared spectrum of cuprous chloride vapour is consistentwith the presence of a cyclic polymer as the principal and electrondiffraction indicates that this is a trimer (CuCl), in the form of a six-memberedaQQ C. C. Addison and B. J. Hathaway, Proc. Chem. SOC., 1957, 19.400 W. Cochran, F. A. Hart, and F. G. Xlann, J., 1957, 2816.401 R. L. Martin and H. Waterman, ibid., p. 2645.402 S. Shibata and K. Sone, Bull. Clteiiz. SOC. Japan, 1956, 20, 852.404 W. Klemperer, S. A. Rice, and R. S. Berry, J. Amer. Chem. SOC., 1957, 79, 1810.D. T. Cromer, J. Phys. Chem., 1957, 61, 1388ADDISON AND GREENWOOD : THE TRANSITION ELEMENTS. 145ring of alternate copper and chlorine atoms having a very large amplitude ofsymmetrical bending vibration. The Cu-C1 distance is 2.16 k 4 0 6 Onaddition of lithium bromide to alcoholic solutions of cupric perchlorate, newbands appear successively in the absorption spectrum; these are ascribed 406to the formation of the groups CuBr+, CuBr,, CuBr,-, CuBr,,-, CUB^,^-,and CUBr64-. Similar observations have been made upon ether solutions.The halides MBr, (M = Mn, Fe, Co, Cu, Cd) are insoluble in ether, butdissolve on addition of lithium bromide. The complexes identified includeLi6CUBr7 and Li,MBr4.407 The anodic oxidation of copper in a number ofaqueous electrolytes can be explained on the assumption that the primaryelectrode reaction is the formation of unipositive copper. In the presenceof ions (CN-, C1-, S,0,2-) which form stable complexes with copper(I), themetal enters solution solely in the +1 state. or C10,-as electrolyte, the valency number is higher than unity at 25", but falls tounity at higher temperatures.408The structural unit in crystalline silver thiocyanate is an endless zigzagchain [as shown in (32)] which results from the formation of a covalent bondfrom the silver atom to the nitrogen atom of another SCN On theother hand, ammonium silver dithiocyanate is built up from AgSCNmolecules and NH4+ and SCN- ions; [Ag(SCN),]- ions are not formed, andthe chain structure of silver thiocyanate has been lost by addition ofNH4SCN.410 The infrared spectra of the compounds KAg(CN), andI(Au(CN), have been compared with those for the 13C- and 15N-substitutedspecies, and it is confirmed that the cyanide groups are bonded to the metalthrough carbon atoms, i.e., [N-C-AgC-N]-.4U The relative tendencies ofa series of similar (sulphonated) organic derivatives of the two groupsnitrogen, phosphorus, arsenic, and oxygen, sulphur, selenium to formcomplexes with silver ions have been compared. Silver forms the moststable complexes with the heavier donor atoms of each The hydro-lysis of sodium aurate has been examined from the variation in conductivity,diffusion, and light-absorption with change in pH. Only the monomericform of the anion (Au02,aq.)- was observed, and there was no evidence ofpolyacid formation.413It can be melted underas little as 50 lb./sq. in. of argon, rather than the 100-150 atm. pressurepreviously considered necessary. The m. p. of cadmium sulphide, at 150lb./sq. in. of argon, is 1475°.413 Tracer techniques have been employed tostudy the disproportionation reaction HgZ2+ =+= Hg2+ + Hg(aq.) in verydilute ( 10-T~) mercurous nitrate solution. The equilibrium constant isWith NO,-,The Zinc Group.-Zinc sulphide has m. p. 1830'.405 Chi-Hsiang Wong and V. Schomaker, J . Phys. Chem., 1957, 61, 358.406 E. M. Kosower, R. L. Martin, and V. W. Meloche, J . Anzer. Chem. SOL., 1957,*07 G. Monnier, Ann. Chim. (France), 1957, 2, 14.408 D. J. Royer, J. Kleinberg, and A. W, Davidson, J . Inorg. Nuclear Chew., 1957,409 I. Lindqvist, Acta Cryst., 1957. 10, 29.410 I. Lindqvist and B. Strandberg, ibid., p. 173.411 L. H. Jones, J . Chem. Phys., 1957, 26, 1578; 27, 468.412 S. Ahrland, J. Chatt, N. R. Davies, and A. A. Williams, Nature, 1957, 179, 1187.*13 G. Jander and G. Krien, 2. anorg. Chem., 1957, 291, 89.79, 1509.4, 115146 INORGANIC CHEMISTRY5.5 x The concentration of free mercury was estimated by extractioninto non-polar organic solvents. The solubility of mercury metal in wateris 3 x 10-7 mole/litre at 25". No evidence was found for the presence ofthe ion Hg+.415 The kinetics of reaction between mercurous and thallicsalts are also in agreement with this disprop~rtionation.~~~ The ,03Hgisotope has been used in the determination of formation constants of Hg1,-and HgI,2- by extraction of mercuric iodide into benzene.417 The cyanidegroups in the molecule Hg(CN), are bonded to the metal through carbonatoms,418 as in the argentous and aurous cyanide c o m p l e ~ e s . ~ ~ Hexagonalmercuric oxide contains infinite spiral chains -0-Hg-O-Hg, and is thusisostructural with the hexagonal form of mercuric ~ u l p h i d e . ~ ~ ~ A study ofthe reaction of the hydroxide ion with mercuric nitrate, the l80 isotopebeing used, has revealed that the initial step is the formation of the basicnitrate Hg,02(N0,),,H,0. In the presence of excess of mercuric nitratethis can be isolated, but with excess of hydroxide it is rapidly hydrolysed toHgO. The oxygen of the HgO so formed is derived from the water whicheffects the hydrolysis.420 By the reaction.3Hg0 + HgXz + 2RNHSX + [Hg,(NR),]X,HgXS + 3HZOa series of mercury iminohalides have been prepared in which X = C1 or Br,and R = H, C,H,, OEt, C,H,, or CO*NH2.421 The action of ammonia onmercury halides is known to give addition compounds [Hg(NH,) ,]X2, andtheir derivatives Hg*NH,X, where X = C1, Br, or I. The correspondinghydrazine compound [Hg(N,H,) ,]Cl, has been shown, from its infraredspectrum, to contain the ion [NH,*NH,*Hg*NH2*NH2l2 f-, analogous to thediammine. The mono-addition compounds [Hg(N,H,)]X, (X = C1, Br)contain the infinite chain -Hg-NH ,-NH ,-HgNH ,-NH ,-. The substitutioncompound [Hg,N,H,]Cl, has a layer lattice.422C. C. ADDISON.N. N. GREENWOOD.414 A. Addamiano and P. A. Dell, J . Phys. Chem., 1957, 61, 1020, 1253.416 H. C. Moser and A. F. Voigt, J . Amer. Chem. SOC., 1957, 79, 1837.416 A. M. Armstrong, J. Halpern, and W. C. E. Higginson, J . Phys. Chem., 1956,417 H. C. Moser and A. F. Voigt, J . Inorg. Nuclear Chem., 1957, 4, 354.418 L. H. Jones, J . Chem. Phys., 1957, 27, 665.419 K. Aurivillius and I. B. Carlsson, Acta Che,m. Scand., 1957, 11, 1069.420 R. B. Bernstein, H. G. Pars, and D. C. Blumenthal, J . Amer. Chenz. Soc., 1957,421 A. Meuwsen and G. Weiss, 2. anorg. Chem., 1957, 289, 5.422 K. Brodersen, ibid., 290, 24.60, 1661.79, 1579