INORGANIC CHEMISTRY.1. INTRODUCTION.THE particular form of the Periodic Table used in inorganic chemistry isstill to some extent a matter of personal preference. Advances in inorganicchemistry during 1956 are presented in this report on the basis of its " longform "; the chemistry of the main groups is discussed first and this isfollowed by a systematic treatment of the transition elements.The list of atomic weights approved by the International Union of Pureand Applied Chemistry includes revised values for 12 elements : Dy, Er,Gd, Hf, In, Ni, Pd, Pt, Re, Sm, W, and Xe. The greatest change is forgadolinium which is altered from 156.9 to 157.26, and substantial modi-fications are also recommended for palladium (from 106.7 to 106.4) andplatinum (from 195.23 to 195.09).The changes reflect a general tendencyto favour values obtained by precise physical methods and it is significantthat most of the elements mentioned above have presented unusual diffi-culties of determination by chemical means either because of difficulties inseparation and purification, or because of difficulties in preparing compoundsof exactly known composition.Two new journals, both Russian, of interest to inorganic chemists beganpublication during 1956, Zhzurnal Neorganicheskoi Khimii and KrystaZZo-gra$yn, Reviews have appeared on the periodicity of thermodynamicproperties of compounds,2 the variations and relationships of some ionizationpotential^,^ the lattice energy of ionic crystal^,^ the Raman spectra ofinorganic compounds, the purification of the rare gases, and the chemistryof non-aqueous ~olutions.~ The last topic is mentioned frequently in thefollowing sections whenever it is relevant to.the chemistry of particularcompounds, but it is convenient here to draw attention to two further moregeneral investigations. The first is the development of diethyl ether as asolvent for ionic reactions.8 The solvent is considered to dissociate to aminute extent as ethyl ethoxide, Et'OEt-, so that compounds like lithiumethoxide behave as bases, and complexes which the solvent forms withelectron acceptors (A), and which may be formulated as E t i [EtO+A]-,behave as acids. The interpretations are based on conductimetric titrationsrather than the isolation and analysis of compounds. The second investig-ation concerns a study of carbonyl chloride as an acid-base solvent ; on thebasis of chlorine-exchange experiments it is concluded that this solvent doesnot undergo self-ionization as C 0 2 &(Cl-), or COCl IC1- but is essentiallycovalent .9E.Wichers, J . Amer. Chena. Soc., 1956, 78, 3235.B. Lakatos, Acta Chim. Acad. Sci. Hwng., 1955, 8, 207.L. H. Ahrens, J . Inorg. Nuclear Chem., 1956, 2, 290.A. F. Kapustinskii, Quart. Rev., 1956, 10, 283.L. A. Woodward, zbid., p. 185.D. S. Gibbs, H. J. Svec, and R. E. Harrington, I n d . Eng. Chem., 1956, 48, 289.V. Gutmann, Svensk kem. Tidskr., 1956, 68, 1; Quart. Rev., 1956, 10, 451.G. Jander and K. Kraffczyk, 2. anorg. Chem., 1956, 282, 121 ; 283, 217.J . L.Huston, .I. Inorg. Nwclrnr Chem., 1956, 2, 12884 INORGANIC CHEMISTRY.An increasing amount is being published on the nature of non-stoicheio-metric compounds and, whilst much of the interest is in the more physicalaspects of the subject, substantial advances are also being made in thechemistry of these systems. The crystal chemistry of non-stoicheiometriccompounds has been reviewed.1° A careful X-ray investigation of theproducts of thermal decomposition of lead dioxide shows that two inter-mediate non-stoicheiometric phases with narrow composition ranges existbetween PbO, and Pb304. The or-phase Pb01.50-1.62 is close to Pb7011 andthe p-phase, Pbl.42-1.50, is close to Pb203.11 Refined phase diagrams in thelead-sulphur system suggest that PbS has 6 x lo1, atoms of excess of Pbper C.C.at the composition of maximum m. p., 1127".12 A series of sevendiscrete phases has been found in the titanium-oxygen system betweenTiO,.,, and TiOl.go. The compositions of these appear to be constantwithin &0.002 and can be represented by the formula Tin02n-l where4 < n < 10.13 A re-investigation of the phases present in the iron-oxygensystem at compositions near FeO has shown that, above lOOO", the composi-tion range of ferrous oxide is from Fe,.,,,O to Fe,.,,,O; below this temper-ature the composition limits converge and at 570" the compound has thecomposition Fe, 930 ; at still lower temperatures a two-phase system(or-Fe + Fe304) separates.14 The cobalt-selenium system has three inter-mediate solid phases : B-CogSe,, which is related to Cogs8 and (Fe,Ni),S,;a y-phase of NiAs structure with some vacant cation sites, which exists overthe composition range CoSe,.,,,.,, at 600" ; and a &phase CoSe,, of pyritesstructure.15 In the cobalt-tellurium system the p-phase has a much widercomposition range (CoTe,.,-,., at 600", CoTe,.,-,., at 335") .16 The ternarycompound Li,Mn,-,O formed by sintering Li,O, and MnO at high temper-atures comprises a single non-stoicheiometric phase of NaCl structure over alarge range of compositions.At higher lithium concentrations, dependingon the temperature, the compound LiMnO, is also f0rrned.l' Strontium-niobium bronzes with the perovskite structure and similar to the sodium-tungsten bronzes have been prepared in the composition range Sr,.,NbO,-Sro.,,Nb03.The colour changes from deep blue to red with increasingstrontium content and compressed-powder specimens have a high electricalconductivity. Other phases, with complex X-ray patterns, exist betweenSr,.,NbO, (white) and Sr,.68Nb0, (black) and there is also evidence forbronzes in the systems Ba,NbO, and Ba,TaO,.ls2. MAIN GROUPS.Group 1.-The dissolution of sodium in methylamine to give a bluesolution has been shown to depend on traces of ammonia in the methyl-lo A. D. Wadsley, Rev. Pure Appl. Chem. (Australia), 1955, 5, 165.l1 G. Butler and J. L. Copp, J . , 1956, 725.12 J. Bloem and F. A. Kroger, 2. phys. Chem. (Frankfurt), 1956, 7 , 1.l3 S. Andersson and A. Magneli, Naturwiss., 1956, 43, 495.l4 J.Aubry and F. Marion, Compt. rend., 1956, 242, 776.l5 F. Bahm, F. Grranvold, H. Haraldsen, and H. Prydz, Acta Chem. Scund., 1955, 9,16 H. Haraldsen, F. Grernvold, and T. Hurlen, 2. anorg. Chem., 1956, 283, 143.1 7 W. D. Johnston and R. R. Heikes, J . Amer. Chem. SOC., 1956, 78, 3255.18 D. Ridgley and R. Ward, ibid., 1956, 77, 6132.1510ADDISON AND GREENWOOD: MAIN GROUPS. 85amine.19 Liquid sodium does not react with zinc phosphate below 160" andthis is also the critical wetting temperature of zinc by liquid sodium if thezinc has been electropolished in a phosphate bath; no such critical temper-ature was found for abraided zinc plates2*Extensive studies of the systems Na20-A120,-Si02 and K,O-A1,0,-SiO,have been reported.21 A new series of crystalline acid metaphosphates hasbeen obtained from a phase study of the system N+O-H,0-P,0,.22Rubidium and casium react with sulphur in liquid ammonia to givecrystalline polysulphides of formula M2S, where x is 2, 3, or 5; these com-pounds and also cs'& were isolated and their physical properties determined.Rb2S4, Rb2S6, and Cs2S4 were not formed under these condition^.^^It has been confirmed that czsium monoxide Cs20 has the anti-CdCI,-typeof crystal structure and it remains the only known example of this structure ;the abnormally large Cs-Cs distance and the short Cs-0 distance indicateconsiderable polarization of the czsium ion.24 The crystal structure oftricasium monoxide has also been determined.25 The Cs-0 bond is ionic asin Cs20 but the Cs-Cs bond length is similar to that in metallic casium.Its semimetallic structure is also reflected by its low m.p. (165") and veryhigh electrical conductivity which is one-third of that of caesium itself.Group II.-Unipositive beryllium is obtained by anodic oxidation duringthe electrolysis of aqueous solutions between beryllium electrodes in adivided cell. In short runs, the Be+ ion is quantitatively oxidized by waterto Be2+ with liberation of hydrogen ; in longer runs some metallic berylliumis formed by disproportionation, 2Be+ _+ Be2+ + Be, and is depositeduniformly throughout the anolyte. The existence of unipositive berylliumwas further demonstrated by its ability to reduce permanganates to man-ganese dioxide and silver salts to metallic silver.26 Similar experiments withorganic oxidants have confirmed that unipositive magnesium Mg+ is formedby anodic oxidation when a solution of sodium iodide in pyridine is electro-lysed between magnesium electrodes2'Beryllium oxymonochloroacetate, Be40 (C1CH2*C02),, has been made andits X-ray cell dimensions found to be approximately the same as those of theoxypropionate Be40(MeCH2*C02)6.28 In the presence of anhydrous ethanol,beryllium oxyacetate splits off acetic anhydride to form higher basic acetatesaccording to the equation :Both the original oxyacetate and the higher basic acetates occlude appreci-able amounts -of the solvent .29Be,O(MeCO,), = Be,O,'+ $- 4MeC0,- + (MeCO),Ole G.Hohlstein and U. Wannagat, 2.anorg. Chem., 1956, 284, 191.2e C. C. Addison, W. E. Addison, D. H. Kerridge, and J. Lewis, J., 1956, 1454.21 J. F. Schairer and N. L. Bowen, Amer. J . Sci., 1955, 253, 681; 1956, 254, 129.22 E. J. Griffith, J . Amer. Chem. SOC., 1956, 78, 3867.23 F. FehCr and K. Naused, 2. anorg. Chem., 1956, 283, 79.Khi-Ruey Tsai, P. M. Harris, and E. N. Lassettre, J . Phys. Chern., 1956, 60, 338.Idem, ibid., p. 345.26 B. D. Laughlin, J. Kleinberg, and A. W. Davidson, J . Ames.. Chem. Soc., 1956,27 W. E. McEwen, J. Kleinberg, D. L. Burdick, W. D. Hoffman, and J. Y . Yang,28 A. V. Novoselova and K. N. Semenenko, Zhur. neorg. Khinz., 1956, 1, 887.2B H. D. Hardt, 2. anorg. Chem., 1956, 286, 254.78, 559.ibid., p. 458786 INORGANIC CHEMISTRY.Magnesium hydride has very different properties depending 011 whetherit is prepared directly from the elements or by pyrolysis of organomagiiesiumcompounds.It has now been shown by X-ray methods that both formshave the rutile crystal structure and that the differences in properties arerelated to the degree of subdivision of the sample.30 Calcium hydridechloride (CaHC1, m. p. 700") and its strontium and barium analogues (m. p.s840" and 850") may be prepared either by melting together the appropriatehydride and anhydrous chloride or by heating the metal and its chloride inan atmosphere of hydrogen. The compounds, which are stable at hightemperatures even under vacuum, resemble mica in appearance and have thePbClF-type crystal structure.31The formation of calcium superoxide Ca(O,), during the dehydration ofcalcium peroxide octahydrate with phosphoric oxide has been discussed.32The possibility of preparing barium superoxide Ba(O,), has also been con-sidered and the equilibrium pressure of oxygen above the compound hasbeen calculated to be 32 atm.at 25", 75 atm. a t loo", and 2300 atm. at 200" 33Group II1.-The boron hydrides and their derivatives continue to attracta great deal of interest. A new B, hydride has been detected by X-raytechniques and a partial elucidation of its structure shows that the boronatoms form an icosahedral fragment similar to that formed by a juxta-position of B4H,, and B,Hl, suitably bridged to give an overall formulaB,H1,.34The effect of nitrogen-bond strain on the chemistry of aminoboronhydrides has been studied by synthesising a series of derivatives in which thenitrogen is in small heterocyclic rings.35 DimethylaminomethylborineMe,NBH*Me, made by treating methylborine with dimethylamine, is pre-dominantly monomeric in the vapour phase but dimeric as aDiborane diammine B,H6,2NH3 reacts with alkali metals in liquid ammoniato give a borohydride and aminoborine :M + B1H,,2NH, + &HZ + NH, + MBH4 -I- BHZ-NH,During removal of the solvent, the aminoborine undergoes ammonolysis toan extent which depends on the metal used, increasing from potassium tolithium.37 The sodium-diborane reaction has been clarified by recognitionof Na,B,H, as an intermediate; the product, which has the empiricalformula NaB,H,, is actually an equimolar mixture of sodium borohydrideand a new borohydride NaB3H, : 382Na + 2B2H6 NaBH, + NaB,H,30 W.Freundlich and B. Claudel, Bull. SOC. chim. France, 1956, 967 ; see also Ann.31 P. Ehrlich, B. Alt, and L. Gentsch, 2. anorg. Chem., 1956, 283, 58.32 C. Brosset and N.-G. Vannerberg, Nature, 1956, 177, 238; S. 2. Makarov and33 I. I. Volnov and A. N. Shatunina, Doklady Akad. Nauk S.S S.R., 1956, 110, 87.34 R. E. Dickerson, 1'. J. Wheatley, P. A. Howell, and W. K. Lipscomb, J . Chew.36 A. B. Burg and C. D. Good, J . Inorg. Nuclear Chem., 1956, 2, 237.36 A. B. Burg and J. L. Boone, J . Amer. Chew SOC., 1956, 78, 1521.37 G. W. Schaeffer, M. D. Adams, and F. J. Koenig, ibid., p. 725.3 8 W. V. Hough, L. J. Edwards, and A. D. McElroy, ibid., p.689.Reports, 1955, 52, 99.N. K. Grigor'eva, Zhur. neorg. Khim., 1956, 1, 1607.Phys., 1956, 25, 606ADDISON AND GREENWOOD : MAIN GROUPS. 87The long-sought monomeric addition compound ammonia-borineH,N,BH, has now been made by the action of lithium borohydride on am-monium salts and its structure is confirmed by X-ray structural analysis.39The preparation, characterization, and chemical reactions of the monomericaddition compounds of borine with pyridine and quinoline are described.mDiborane reacts with phosphorus trifluoride under pressure at room temper-ature to give the addition compound F,P,BH,. The properties of thissomewhat unexpected compound are very similar to those of the carbonylderivative OC,BH, and its ethane-like structure has been confirmed byRaman spectro~copy.~~ The relative ability of borine, boron trifluoride, andtrimethylboron to co-ordinate with the dialkyls of oxygen, sulphur, andselenium has been compared.42A kinetic study of the reaction of decaborane B1,H,, with low-molecularweight alcohols to give borate esters and hydrogen is reported.43 Unlike thelower boranes, decaborane dissolves in aqueous solutions of alcohols ordioxan without rapid hydrolysis and the rate of hydrogen .evolution exhibitsa marked induction period.I t is now found that decaborane forms amonobasic acid in these solutions without the evolution of hydrogen, thatthe decaborane is partly recoverable, and that the solutions can be potentio-metrically titrated with aqueous sodium hydr~xide.~,Borohydrides can be prepared by a new method involving the hydrolysisof magnesium boride MgB, with bases such as potassium hydroxide or tetra-methylammonium hydroxide.45 Trisubstituted borohydrides of the typeNa[B(OR),*H], which are readily prepared by the addition of sodium hydrideto alkyl borate esters, are more powerful reducing agents than sodium boro-hydride itself.This is attributed to the greater ease of removing a hydrideion from [B(OR),*H]-, because B(OR), is a weaker acceptor than borine,BH,.46 Tetra-alkoxyborohydrides are prepared similarly, the sodium hydridebeing replaced by sodium alk~xide.~' The addition compounds of lithiumborohydride and lithium aluminium hydride with tetrahydrofuran and tri-methylamine, and of aluminium hydride itself with tetrahydrofuran, havebeen investigated.An elegant series of experiments on the nuclear magnetic resonancespectrum of aluminium borohydride shows that Al(BH,), dissociates re-versibly at 80" into diborane and a new compound A12B4H1, : 49ZAIB,H,, e.B,H, + AI,B,H,,39 S. G. Shore and R. W. Parry, J . Amer. Chem. SOL., 1955, 77, 502; E. L. 6084;E. W. Hughes, ibid., 1956, 78, Lippert and W. N. Lipscomb, ibid., p. 503.40 V. I. Mikheyeva and Ye. M. Fedneva, Zhur. neorg. Khim., 1956, 1, 894.4 1 R. W. Parry and T. C . Bissot, J . Amer. Chem. SOC., 1956, 78, 1524; R. C. Taylorand T. C. Bissot, J . Chem. Phys., 1956, 25, 780.42 W. A. G. Graham and F. G. A. Stone, Chem. and Ind., 1956, 319.43 H. C. Beachel and T.R. Meeker, J . Amer. Chem. SOC., 1956, 78, 1796.44 G. A. Guter and G. W. Schaeffer, ibid., p. 3546.4 5 A. J. King, F. A. Kanda, V. A. Russell, and W. Katz, ibid., p. 4176.4 6 H. C. Brown, E. J. Mead, and C. J. Shoaf, ibid., p. 3616.4 7 H. C. Brown and E. J. Mead, ibid., p. 3614.4 8 E. Wiberg and W. Gosele, 2. Naturforsch., 1956, l l b , 485; idem, ibid., p. 486;E. Wiberg, H. Noth, and R. Uson, ibid., p. 487; E. Wiberg and A. Jahn, ibid., p. 489;E. Wiberg, H. Noth, and R. Uson, ibid., p. 490.49 R. A. Ogg and J. D. Ray, Discuss. Faraday Soc., 1955, 19, 239, 24688 INORGANIC CHEMISTRY.All protons in aluminium borohydride are chemically equivalent and verysimilar to those in a simple borohydride ion BH,- ; moreover, all the protonsare covalently bonded to both aluminium and boron and the three boronatoms are covalently bonded tetrahedrally to four equivalent protons.These findings cannot be reconciled with a static model of the molecule, orwith intermolecular exchange of borohydride ions or rotation within eachmolecule.The only tenable explanation appears to be in terms of aquantum-mechanical tunnel effect.49 Perhaps the simplest representationof the compound is (1) in which a double line represents bridge-bondingwith two protons between the aluminium atom and a boron atom. Thesecond borohydride may be similarly represented by (2).Boron trifluoride addition compounds have been studied by a variety oftechniques. Nuclear resonance spectra indicate that the structure of borontrifluoride hydrates depends on the rate of crystallization : slowly cooledsamples are un-ionized (BF,,H,O and BF3,2H20) whereas more rapidlycooled samples retain some of the ions which characterize the compounds inthe molten state (e.g., H,0+BF3*OH-).m Boron trifluoride forms a 1 : 1compound with urea which melts at 82"; above 125" the compounddecomposes to ammonium fluoroborate, boron nitride, and polymeric hydro-gen cyanate, from which it is concluded that boron is bonded to nitro-gen rather than oxygen in the complex.51 Boron trifluoride-dinitrogentetroxide, which does not melt in a sealed tube at 300", is insoluble in non-polar solvents, and rapidly nitrates benzene, has been formulated as an ioniccompound N02+(BF3.N0,)-.52 A complete structure determination ofboron trifluoride-pyridine has shown that the B-N bond length (1.53 A) isshorter in this compound that in other boron complexes in which nitrogenis the ligand (167-1.64 A).% It is, however, comparable with the value of1-56 found for H3N,BH,.39 Stable 1 : 1 complexes of boron trifluoride,hydrogen fluoride, and the methylbenzenes have been isolated.These com-pounds melt below room-temperature and have a high specific electrical con-ductivity (about 10-2 ohm-l cm.-l) ; they may be formulated as ArH+BF4-(Ar = Me*C6H5, m-Me,C,H,, s-Me3C6H3, as-Me,C,H,) .54 The correspondingcompounds formed by replacing hydrogen fluoride by either ethyl fluoride orformyl fluoride have also been isolated and have similar proper tie^.^^The molar heats of solution of the boron trihalides in nitrobenzene, andthe heats of reaction of the trihalides with pyridine in nitrobenzene arereported and lead to the unexpected result that, under these conditions, theelectron-acceptor strength increases in the order BF, < BCI, < BBr3.566o P.T. Ford and R. E. Richards, J., 1956, 3870.61 H. J. Becher, Chem. Bey., 1956, 89, 1691.S2 G. B. Bachman, H. Feuer, B. R. Bluestein, and C. M. Vogt, J . Amer. Chem. SOC.,63 2. V. Zvonkova, Kristallograjiya, 1956, 1, 73.b4 G. OlAh, S. Kuhn, and A. PavlAth, Nature, 1956, 178, 693.65 G. OlAh and S. Kuhn, ibid., p. 1344.66 H. C. Brown and R. R. Holmes, J . Amer. Chem. Soc., 1956, 78, 2173.1955, 77, 6188ADDISON AND GREENWOOD MAIN GROUPS. 89Boron trifluoride is not ammonolysed by liquid ammonia in the temper-ature range -78" to +50° unless an alkali metal is also present in thesolution.57 Furthermore, the addition compound boron trifluoride-ammonia,which can be isolated from solutions of boron trifluoride in liquid ammonia,reacts with solutions of the alkali metals in ammonia in a way which variesmarkedly with the particular metal chosen : with potassium and caium thereacting mole-ratio of metal to complex is 1 : 1, with sodium the ratio is 2.5 : 1and with lithium 3 : 1, though in the last case temporary end-points could bedetected at the two smaller ratios as well. The following reaction schemeshave been suggested to represent the overall stoicheiometry and the productsformed : 58BF,,NH, + K = NHZ*BFz + KF + +Ha2BF,,NH3 + 5Na + 2NHB = (NH,),B(NH).BF(NH,) + 5NaF + 24H,2BF,,NH3 + 6Na + 2NH3 = (NH,),B(NH)*B(NH) + 6NaF + 3H,Ammonolysis of boron tri-iodide on the other hand proceeds rapidly inliquid ammonia even in the absence of alkali metals. The products areammonium iodide and boron imide B2(NH),.59 Studies of the effect ofsteric strain on the reaction rate and heat of reaction of substituted pyridinebases with diborane, boron trifluoride, and trimethylborine continue.60Phase studies have confirmed the existence of the addition compoundboron trichloride-acetyl chloride in the solid state despite the fact that abovethe m.p., -54", the vapour pressure of the system shows a positive deviationfrom ideality. There is no compound in the system boron trichloride-benzoyl chloride, and neither system shows catalytic activity, in contrast tothe behaviour of these ligands with gallium trichloride.61 The crystalstructure of the addition compound between diboron tetrachloride andethylene shows that the structure of the molecule is a zig-zag chainC12B*CH2*CH,-BCl,, in agreement with chemical evidence.62A new class of organoboron compound, RBXoOR', in which two of thehalogens in BX, have been replaced by an alkyl (or aryl) and an alkoxy-group has been reported.63 The thermal stability, solvolysis, and co-ordin-ation reactions of these compounds and the related series RB(OR), andRBX, were studied as well as the preparation and stability of dialkyl chloro-boronates C1B(OR),.64 A series of triaryl borates were prepared by thereaction of boron trichloride with substituted phenols or naphthols and theiramine addition compounds investigated for steric and polar influences. 65The studies have also been extended to include the interaction of unsaturatedalcohols and ethers with boron trichloride.66 Some convenient procedures5 7 W.A. Jenkins, J . Amer. Chem. SOC., 1956, 78, 5500.68 W. J. McDowell and C . W. Keenan, ibid., p. 2065.59 Idenz, zbid., p. 2069.6o H. C. Brown, D. Gintis, and H. Podall, ibid., p. 5375; H . C. Brown and D. Gintis,ibid., p. 5378; H . C. Brown and L. Domash, ibid., p. 5384; H . C. Brown, D. Gintis, andL. Domash, ibid., p . 6387.N. N. Greenwood and K. Wade, J., 1966, 1627.Idem, ibid., p. 1540; M . F.Lappert, ibid., p . 1768.6a E. B. Moore and W. N. Lipscomb, Acta Cryst., 1956, 9, 668.63 P. B. Brindley, W. Gerrard, and M. F. Lappert, J., 1956, 824.66 T. Colclough, W. Gerrard, and M. F. Lappert, ibid., p. 3006.66 W. Gerrard, M. F. Lappert, and H. B. Silver, ibid., p . 3286'30 INORGANIC CHEMISTRY.for the preparation of primary, secondary, and tertiary alkyl borate estershave been outlined.67Unipositive aluminium is formed by anodic oxidation when aqueous solu-tions are electrolysed between an aluminium anode and a platinum cathode.68This is similar to the behaviour of beryllium and magnesium anodes men-tioned on p. 85.The Raman spectra of several methylaluminium halides of the typeMe,AlX and MeAlX, (X = C1, Br, or I) indicate that the compounds aredimeric, the bridging occurring via two methyl groups in each case ratherthan via halogen atoms as had formerly been supposed.Trimethylindiumis m0nomeric.6~The crystal structure of the addition compound AlBr,,H,S, and thefact that solutions of the complex in organic solvents are acidic and can beelectrolysed to give hydrogen at the cathode, support the formulationHi (AlBr,*SH)-. 7O The determination of the solubility of aluminium chlorideby a new experimental method reveals weak complex formation with aromatichydrocarbons at room temperature which disappears at about 70°.71 Theinteraction of aluminium bromide with olefins and benzene was furtherstudied. 72 The kinetics of bromine-exchange between ethyl bromide andaluminium bromide in carbon disulphide has been interpreted as indicatingthat carbonium ions are not involved in the reaction.73The constitution of gallium dichloride has been resolved ; Raman spectrashow it to be Ga+GaCl,- in the molten state 74 and X-ray data confirm thisstructure for the solid also.75 Further reduction of the dichloride bymetallic gallium can be achieved in the presence of aluminium trichloride :GaGaCI, + 2Ga + ZAICI, = 4GaAIC1,All the gallium is then present in the unipositive state and the product,GaAlCl,, m.p. 176", is very similar to the dichloride itself, GaGaCl,, m. p.17Oo.''j (Bismuth trichloride may likewise be quantitatively reduced withmetallic bismuth in thepresence of aluminium trichloride to give the uni-valent bismuth salt BiAlCl,, m.p. 253", and cadmium chloride gives 72%conversion into the corresponding CdAlCl,. 76)Addition compounds of gallium trichloride with alkyl halides have beeninvestigated tensimetrically and by phase diagrams, 7 7 and a similar in-vestigation is reported for the addition compounds of gallium trichloridewith acyl chlorides.61Trimethylindium is a stronger electron-acceptor than trimethylthallium6 7 H. C. Brown, E. J. Mead, and C . J. Shoaf, J . Anzer.. Chem. SOC., 1856, 78, 3613.6 8 E. Raijola and A. W. Davidson, ibid., p. 556.69 G. P. van der Kelen and M. A. Herman, Bull. SOC. chim. belges, 1956, 65, 362.70 A. Weiss, R. Plass, and A. Weiss, 2. anorg. Chem., 1956, 283, 390.71 F. Fairbrother, N. Scott, and H. Prophet, J., 1956, 1164.72 F.Fairbrother and K. Field, ibid., p. 2614.73 F. L. J. Sixma, H. Hendriks, and D. HoltzapffeI, Rec. Trav. chim., 1956, 75, 127;74 L. A. Woodward, G. Garton, and H. L. Roberts, J . , 1956, 3723; L. A. Woodwart175 G. Garton and H. &I. l'owell, personal coniniunication ; see also ref. 76.76 J. D. Corbett and K. K. McMullan, J . Amer. Chem. SOC., 1956, 78, 2906.7 7 R. Wong and H. C. Brown, J . Inorg. Nuclear Chenz., 1955, 1, 402.F. L. J. Sixma and H. Hendriks, Proc. k . ned. Akad. Wetemchap., 1956, 59, B, 61.and -4. A. Kord, ibid., p. 3721ADDISON AND GREENWOOD : MAIN GROUPS. 91so that the order of acceptor character of the Group 111 trimethyls towardsa ligand like trimethylamine is B < A1 > Ga > In > T1. The thermal andchemical stability of derivatives such as (Me,Tl*SMe),, obtained from thereaction of Me2T1F with NaSMe in methanol, indicate that thallium andpossibly indium may form dative x bonds to sulphur and selenium.78 Thedipole moments of some addition compounds of indium and thallium tri-halides with ethers and cyclic nitrogen-containing ligands have been pub-lished.79Group 1V.-Considerable progress has been made in the field of graphitecompounds and other molecular compounds of the layer-lattice type whichmay be prepared by intercalation. Over 30 new graphite compounds havebeen prepared : intercalation is most probable with chlorides of multivalenttransition elements in their higher oxidation states but also occurs with thechlorides of certain lanthanide metals and of iodine.In addition, thechlorides of all Group I11 elements form graphite compounds but these canbe hydrolysed, in contrast to the compounds formed by the transitionelements.80 The results suggest that intercalation involves transfer ofelectrons from the conduction band of graphite to the cation of the reactinghalide and cannot be interpreted in terms of sieve action or dipole inter-action.81 It appears that any substance may intercalate any other substanceprovided that electron donor-acceptor interaction is possible and that thehost can provide physical accommodation by lattice expansion-a layerlattice is not essential. On the basis of these ideas it was predicted thatboron nitride, aluminium diboride, and chromium trichloride should be ableto act as host and should be able to occlude oxides, sulphides, and oxyhalidesas well as chlorides.This was found to be the case.82There is no radiochemical exchange between graphite ferric chlorideC,,FeCl, and ferric ions. 83 High-resolution electron diffraction and X-raypowder photography show that single layers of ferric chloride lie betweensuccessive parallel layers of graphite. The infrared spectrum of graphiteoxide has been further i n ~ e s t i g a t e d . ~ ~ It is curious that, although graphitetakes up 24 times its weight of iodine monochloride and about a third of thisamount of bromine, neither chlorine nor iodine alone is noticeably inter-calated.*6 Solutions of the alkali metals in liquid ammonia react withgraphite to give compounds of ideal formuk C12M(NHJ2, in which thereare alternate layers of graphite and alkali ammine, and C,,M(NH,), in whichevery third layer of the graphite lattice is replaced.Lithium and methyl-amine give a similar compound C,2Li(MeNH,),.87Carbon tetraiodide is not solvolysed by liquid ammonia near its b. p.but reversibly forms the addition compound, CI4,2NH,. However, ini 8 G. E. Coates and R. A. Whitcombe, J., 1956, 3351.70 I . A. Sheka, J . Gen. CJzem. (U.S.S.R.), 1956, 26, 25.8o R. C. Croft, Austral. J . Chem., 1956, 9, 184.81 Idem, ibid., p . 194.82 Idem, ibid., p p . 201, 206.83 R. M. Lazo and J . G. Hooley, Caitad. J . CIaem., 1956, 34, 1574.J. M. Cowley and J . A. Ibers, A d a Cryst., 1956, 9, 421.a 6 D. IIadii and A.Novak, Trans. Faraday Soc., 1955, 51, 1614.t ~ * W. Rudorff, V. Sils, and R. Zeller, 2. anorg. Chem., 1956, 283, 299.W. Riidorff, W. Schulze, and 0. Rubisch, ibid., 1966, 282, 23292 INORGANIC CHEMISTRY.the presence of potassium amide there is a base-catalysed reactionCI, + NH,* CHI, + INH,, and the iodine amide reacts further withpotassium amide to give hydrazine : INH, + KNH, + N2H4 + KI.88An improved synthesis of thiocyanogen (CNS), has been described; thecompound forms addition products with boron trifluoride and trichloride,and its derivative potassium cyanosulphite, K(NCSO,), was prepared frompotassium cyanide in liquid sulphur dioxide. 89 Selenosemicarbazide,NH,-CSe*NH*NH,, has been synthesised by isomerising hydrazine seleno-cyanate in the presence of aldehydes or ketones and then hydrolysing theselenosemicarbazone so formed.g0Polymeric silicon subhydride (SiH), is formed by the reaction of tri-bromosilane with magnesium.g1 Silicon tetrabromide and magnesium givethe sub-bromide (SiBr),, but when the tetrabromide reacts with silicon at1200°, silicon dibromide (SiBr,), is formed, together with the well knowncompound Si,Br,.The dibromide gives dialkyls with Grignard reagents, isreduced by lithium aluminium hydride, and hydrolyses to the subsilicicacid [Si(OH),.,],.92In a series of experiments on the hydrolysis of trichlorosilane and itsderivatives, a crystalline silicon oxyhydride (HSiO,.,), was synthesised andshown to have a " mica-like " structure which could be formulated as thetwo-dimensional polymer (3).This could be dehydrogenated at 507" instages which correspond to the reactions :H,Si,Oa __t H4Si,0a H&O, Si,O, (i.e., Si,O,)It is suggested that the structure of the sesquioxide is similar to (3) exceptthat Si-H bonds within each sheet are replaced by Si-Si bonds betweenI0ISiH ,'0, ,o' ' O\ loSiH S i HI I/Y"'i i"' MelSi \ CH2 /siMe2H'C I / siY 742MeS i --CH2- S i MeI IS i Me2adjacent sheets. When alkyltrichlorosilanes RSiCl, were hydrolysed theproduct depended on the size of the alkyl group. The ethyl derivativesgave a sheet polymer like (3) :nEtSiCI, + I-5nH20 + (EtSiOl.&, + 3nHCIThe tert.-butyl derivative on the other hand was sterically hindered fromcomplete polymerization and formed the tetramer (ButSiO,.,) , ; isopropyl-88 G.W. Watt, W. R. McBride, and D. M. Sowards, J. Amer. Chem. SOC., 1956, 78,*O R. Huls and M. Renson, Bull. SOC. chim. belges, 1956, 65, 209, 611.@2 M. Schmeisser and M. Schwarzmann, 2. Naturforsch., 1966, l l b , 278.1562.F. See1 and E. Miiller, Chem. Ber., 1955, 88, 1747,G. Schott, W. Herrmann, and E. Hirschmann, Angew. Chem., 1966, 68, 213ADDISON AND GREENWOOD MAIN GROUPS. 93trichlorosilane gave some tetramer (4) and some mica-like polymer (3) .93The structure of the tetramer has been shown by X-ray analysis to be thesame as that of adamantane and hexamethylenetetramine with which it isisosteric-( RSi) 406, (HC) 4(CH2)6, and N,(CH,),.94 Hexathia-adamantane(CH),S6 also has the same molecular structure, the six sulphur atoms forminga regular octahedron about the tetrahedron of carbon atoms.95Silicon tetrachloride reacts with ammonia to give silicon di-imide andammonium chloride as the only products and the compound formulated asSiC14,6NH, is in fact Si(NH), + 4NH,CLS6The chemistry of silyl compounds has been revie~ed.~' Trisilylamine(SiH,),N has been shown by electron diffraction to have a planar skeleton withthe nitrogen atom surrounded by three silicon atoms at the corners of anequilateral triangle.This shape, together with the abnormally short Si-Nbond length, implies partial double-bonding by back-donation of the nitrogenlone-pair electrons into d orbitals of the silicon atoms, and is consistent withthe chemistry of the compo~nd.~8 The recently prepared tetrasilylhydrazine(SiH,),N*N(SiH,), also has negligible donor or acceptor proper tie^.^^ Silylisocyanide SiH,NC and isothiocyanate SiH,NCS have been prepared andtheir physical properties reported.100 Further work on the infrared andRaman spectra of disiloxane (SiH,),O has been interpreted on the basis of astructure in which the silyl groups rotate freely about a linear 5-0-5 axis.lo1This is at variance with an earlier interpretation on the basis of anasymmetric-top model.A new series of cyclic organosilicon compounds has been obtained byrapid, low-pressure pyrolysis of tetramethylsilicon at 720".The compoundSi,C,H,, has the structure (5), one methyl group of which is sometimesreplaced by hydrogen to give Si,C,H,,.Another compound isolated had theformula Si,C,,H,, ; it melted at 106" and may be assigned the structure (6).lo2The chemistry of germanium has been comprehensively reviewed.lo3Germanium monoxide is formed by the action of carbon dioxide on german-ium at 700-900" : Ge + CO, + GeO + C0.lo4 TrichloromonogermaneGeHCl,, which is best prepared by the low-temperature reaction of hydrogenchloride on germanium sulphide, is more unstable than formerly supposedand readily loses HC1 at -30" to give germanium dichloride; this in turnrapidly disproportionates to germanium and the tetrachloride via inter-mediate polymeric subchlorides. lo5Lead fluoride reacts with alkali fluorides to form addition compoundsE. Wiberg and W. Simmler, 2.anovg. Chew., 1966, 283, 401.94 G.-M. Schwab, J. Grabmaier, and W. Simmler, 2. phys. Chem. (FrankJuyt), 1966,6,96 E. K. Andersen and I. Lindqvist, Arkiv Kemi, 1956, 9, 169.9 7 A. G. MacDiarmid, Quart. Rev., 1966, 10, 208.88 K. Hedberg, J . Amer. Chem. Soc., 1955, 77, 6491.99 B. J. Aylett, J . Inorg. Nuclear Chem., 1956, 2, 325.loo A. G. MacDiarmid, ibid., p. 88.lol R. C. Lord, D. W. Robinson, and W. C. Schumb, J . Amer. Chem. SOC., 1966, 78,lo2 G. Fritz and B. Raabe, 2. Nalurfovsch., 1956, l l b , 57.lo3 E. Gastinger, Fortschr. chem. Forsch., 1955, 8, 603.lo4 Idem, 2. anorg. Chem., 1956, 285, 103.lo6 C. W. Moulton and J. G. Miller, J . Amer. Chem. SOC., 1956, 78, 2702.376.M. Billy, Compt. rend., 1956, 242, 137.132794 I NOKG.\N IC CHEMISTRY.whose formulze depend on the ionic radius of the alkali metal. Potassiumforms K,PbF,, whereas rubidium and czsium form the perowskite-typeMPbF,. In addition, potassium and rubidium also form the non-stoicheio-metric compounds M,,Pb,_,F,-,, where n = 0.2-0.3 ; these crystallize in theanti-a-AgI structure with additional fluoride ions.lo6Group V.-A redetermination of the electrochemical properties of liquidammonia over a range of temperature leads to a specific conductivity of1.97 x Thethermoelectric properties of nietal-ammonia solutions cannot be interpretedon ionic or semiconductive mechanisms and imply a quantum-mechanicaltunnel process for electron transport.lo8Improved syntheses of hydrazine,log NN-disubstituted hydrazines, l10and hydroxylamine ll1 have been described.The product of the reactionof nitric oxide with potassium sulphite (K,SO,,BNO), which was recentlyshown to be the potassium salt of nitrosohydroxylaminesulphonic acidON*N(OH)*SO,H, can also be prepared by nitrosating hydroxylaminemonosulphonate with an alkyl nitrite in alkaline so1ution.ll2 The constitu-tion of hydroxylamine-0-sulphonic acid H,N*O*SO,H (sometimes calledsulphoperamidic acid) ha5 been further studied. The compound, which maybe made by direct addition of hydroxylamine to sulphur trioxide, reacts withdiazomethane to give the trimethyl derivative Me,N*O-SO, rather than theexpected monomethyl derivative H,N-O*SO,Me. Since the trimethylderivative has an X-ray pattern which is identical with that of the additioncompound formed between trimethylamine oxide and sulphur trioxideMe,NO,SO,, the previously rejected formula for sulphoperamidic acidH,&*O*sO, should be re~0nsidered.l~~Several reviews have been written on the structure and reactivity ofdinitrogen tetroxide.ll* The electrical conductivity of the liquid is 1000times less than that of the solid at -20" and is 2-36 x lo-', ohm-l cm.-l at170.115 Molecular addition compounds of dinitrogen tetroxide with cyclicethers 116 and with a range of nitrogen, oxygen, and aromatic hydrocarbondonors 117 have been reported.Certain of these systems, for example thosewith ethyl acetate and 9-tolyl cyanide, show two distinct liquidus ciu-vesand imply that the complexes may have two different m.p.s.l18ohm-l cm.-l at -38.9" and an ionic product of 10-29*1.107lo6 0. Schmitz-Dumont and G. Bergerhoff, 2. anorg. Chem., 1956, 283, 314.lo' J. Cueilleron and RI. Charret, Bull. SOC. chim. France, 1956, 798, 800; Cotupf.Io8 G. Lepoutre and J . F. Dewald, J. Amer. Chem. SOC., 1956, 78, 2953, 2956.IoS L. F. Audrieth, U. Scheibler, and H. Zimmer, ibid., p. 1852.110 R. A. Rowe and L. F. Audrieth, ibid., p. 563.l l 1 R. E. Benson, T. L. Cairns, and G. M. Whitman, ibid., p. 4202.112 E. Degener and F. Seel, 2. anorg. Chem., 1956, 285, 129.113 U. Wannagat and K. Pfeiffenschneider, Naturwiss., 1956, 43, 178.114 P. Gray and A. D. Yoffe, Quart. Rev., 1955, 9, 362; idem, Chem. Rev., 1955, 55,1069; C. M. S. Teese and A . G. Whittaker, J. Chem.Phys., 1956, 24, 776; A. G. Whit-taker, ibid., p. 780; C. C. Addison, Kec. Trav. claim., 1956, 75, 626; 2. G. Szab6, L. G.Bartha, and B. Lakatos, J., 1956, 1784; T. M. Oza and V. T. Oza, J . Arne$/. Chew. SOC.,1956, 78, 3564.rewd., 1956, 242, 521.R. S. Bradley, l'?,ans. Faraday SOC., 1956, 52, 1255.116 H. H. Sisler and P. E. Perkins, J. Awzer. Chem. SOC., 19.56, 78, 1135.1 1 7 C. C. Addison and J . C. Sheldon, J., 1956, 1941.Idp???, ihid., p. 2709ADDISON ANI) GREENW001) : MAIN GROUPS. 95Dinitrogen tetroxide oxidises dialkyl sulphides smoothly to sulphoxidesR2S0 without any formation of the corresponding sulphone K,S02, and alsooxidises trisubstituted phosphines to phosphine oxides R,PO. Since thesulphoxides formed 1 : 1 addition compounds with dinitrogen tetroxide incontrast with the sulphones and phosphine oxides, it was concluded thatsulphur was the electron donor in the s u l p h o ~ i d e s .~ ~ ~ The reactions of di-nitrogen tetroxide with mercury,120 and with copper, zinc, and uranium inthe presence of organic electron-donor solvents have also been investigated.I2lThe electrical conductance of anhydrous nitric acid and of solutions ofwater and dinitrogen pentoxide in nitric acid have been interpreted in termsof the self-ionic dissociation :2HNO3 NO,' -t NOS- -t- HZO.,4t -10" the conductivity of the pure acid is 3-67 x and this corre-sponds to a mole-fraction dissociation constant of 9.30 x in agreementwith the results of cryoscopic measurements. The addition of water lowersthe conductivity of the pure acid owing to a repression of the dissociation.122A systematic study of the ultraviolet spectra of solutions of sodiumnitrite in aqueous sulphuric acid shows that below 40% acid the spectrum isessentially that of nitrous acid and above 70% acid is that of the nit.rosoniumion NO ; at intermediate concentrations the nitrous acidium ion H2N0,+is an important constituent, and equilibria involving the three species havebeen calculated.Similar results were obtained for aqueous phosphoric acidsolutions of sodium nitrite, but in concentrated hydrochloric acid there isalmost total conversion into nitrosyl ch10ride.l~~ The equilibrium betweenthe nitrosonium ion and nitrous acid in aqueous perchloric acid has alsobeen investigated spectrophotometrically.124Additioncompounds of nitrosyl chloride have been studied by chemical exchange ofradioactive chlorine.126 Dinitrosyl pyrosulphate has been formulated as anionic compound (NOi),S20,2- on the basis of its high m.p. 233" and lowmolecular weight in sulphuric acid ; it is rapidly solvolysed by water, alcohols,ammonia, and methylamine, and reacts with a variety of other compounds.12iThe infrared, Raman, and nuclear magnetic spectra of nitryl fluoride allsupport the plane-triangular structure 0,NF rather than the zigzag formulaONOF.l28 The reactions which occur when nitryl fluoride dissolves insulphuric, selenic, and phosphoric acids have been studied by following theconductivity and other physical properties of the NitrylThe chemistry of the nitrosonium ion has been reviewed.12jllS C.C. Addison and J. C. Sheldon, J., 1956, 2705.1x1 E. S. Freeman and S. Gordon, J . Ame7,. Chem. SOL., 1956, '78, 1813.121 C. C. Addison, J . C. Sheldon, and (in part) I?i. Hodge, J . , 1956, 3900.l Z 2 W. H. Lee and D. J. hlillen, ibid., p. 4463.lZ3 N. S. Bayliss and I>. W. Watts, ,4ustral. J . Chem., 1956, 9, 319.lZ4 K. Singer and P. A . Vamplew, J . , 1956, 3971.lZ5 F. Seel, Angew. Chem., 1956, 68, 272; see aleo <*. C . Addison and J . Lewis, Quart.126 J. Lewis and D. B. Sowerby, Rec. l r a v . chim.. 1956, 75, 615.lZ7 U. Wannagat and G. Hohlstein, 2. anorg. Chem., 1956, 284, 177.128 R. E. Dodd, J. A. Rolfe, and L. A. Woodward, Trans. Faraday SOC., 1956, 52,12s G.Hetherington, D. R. Hub, and P. L. Robinson, J . , 1955, 4041.lt'eu., 1955, 9, 115.145; R. A. Ogg and J . R. Ray, J - Chem. Phys., 1956, 25, 79'796 INORGANIC CHEMISTRY.chloride when dissolved in polar solvents chlorinates rather than nitratesalkylbenzenes. This is contrary to expectations and may be due to re-action with traces of moisture to give free chlorine : 3N02C1 + H,O +C1, + NOCl + 2HN0,. In agreement with this, reactive solutions werefound to have the same spectrum as nitrosyl chloride whereas non-reactivesolutions in non-polar solvents were colourless. 130Fluorine analogues of the phosphoronitrile chlorides (PNCl,), cannot besynthesised by methods used for the chlorides or by fluorination of thechlorides with normal reagents ; however, the compounds (PNF,), and(PNF,) have now been successfully prepared by fluorinating the correspond-ing chlorides with solid potassium fluorosulphite KS0,F.Both compoundsare volatile solids melting at 27.1" and 30.4" respectively and boiling at51.8" and 89.7"; they are stable up to 300" but at higher temperatures givecolourless liquid polymers (PNF,),.l31Phosphorus pentachloride PC14+Pc&- reacts with an equivalent amountof arsenic trifluoride in arsenic trichloride to give the compound PCI,+PF,-,a hygroscopic salt which sublimes with some decomposition a t 135". Itshould be noticed that this compound has the same empirical formula as themixed halide PF3Cl, which is a gas at room temperature.132 PCl,+PF6-decomposes above 70" to give phosphorus pentafluoride and the new com-pound PC1,F which exists as a non-polar liquid and an ionic solid PCl4+F-.luConsiderable progress has been made in the formulation of the products ofaddition of bromine to phosphorus trichloride : the stable mixed halide ofempirical formula PC1,.6,Bro.,, has a face-centred cubic lattice with 12phosphorus atoms in the unit cell, P12C156Br4.Further analysis shows thatthe structure is 8PC14+4PC16-4Br-.134 Conductance experiments on solutionsof phosphorus pentabromide in acetonitrile indicate that the compoundiOniSeS in this solvent as PBr4+PBr6-. 135Pyrophosphoryl chloride P,0,C14 and tetraphosphoryl chloride P40,C1,0have been prepared together with phosphoryl chloride by the reaction ofphosphorus trichloride with dinitrogen tetroxide, and their structure,physical properties, and chemical reactions studied.136 The complexmixture of products resulting from the mild alkaline hydrolysis of thephosphorus trihalides has been separated chromatographically and a newisohypophosphate identified.This compound, which has the formulaNa,(HP,O,), has been ascribed the structure (7) and differs from the hypo-phosphate Na,H(P,O,) (8) in having no P-P bond.137The co-ordination chemistry of phosphorus oxychloride and other multi-valent chlorides of elements in Groups V and VI was discussed at theAmsterdam Conference, and new data were presented on the electrical con-lSo M. J. Collis, F. P. Gintz, D. R. Goddard, and E. A. Hebdon, Chem. and Irtd., 1955,lS1 F.Seeland J. Langer, Angew. Chem., 1956, 68, 461.13a L. Kolditz, 2. anorg. Chem., 1956, 284, 144.lSs Idem, ibid., 1956, 286, 307.134 A. I. Popov, D. H. Geske, and N. C. Baenziger, J . Amer. Chem. SOC., 1956, 78,lSb Idem, ibid., p. 4617.lS8 R. Klement and K. H. Wolf, 2. anoug. Chem., 1956, 282, 149.lS7 E. Thilo and D. Heinz, ibid., 1955, 281, 303.1742.1793; see also G. S. Harris and D. S. Payne, J., 1956, 4613ADDISON AND GREENWOOD : MAIN GROUPS. 97ductivity and heat of dissociation of the complex TiC14,2POC1,.138 Theconfusion which has existed about the composition of complexes formedbetween phosphorus oxychloride and the tetrachlorides of zirconium andhafnium has been clarified by a careful phase study of the system ZrC1,-POC13.Two compounds were found, ZrCl,,POCl,, m.p. 205", and ZrC1,,2POC13,m. p. 184-7°.139 This agrees with the results of cryoscopic work in nitro-benzene. 140 Distillation gives a product of constant composition which maybe represented approximately as 321-C1,,2POCl,,~~~ but this is presumably anazeotrope rather than a definite compound. The complexes of phosphorusoxycliloride with ierric chloride have also been investigated.142NaO ONa'P-0--P /" ) / I I I I \H 0 0 ONa( 8 )/ONa'P--PNaO/ll l l \HO 0 0 ONaA general structural theory of condensed phosphates has been developedfor predicting the structures to be expected in various systems and forcalculating the number of P-0-P links they contain. 143 Chromatographicseparation of the products formed by the partial hydrolysis of Graham'ssalt has revealed the existence of ring phosphates higher than the tetra-metaphosphate ; the penta- 2nd possibly the hexa-metaphosphate have beenidentified and it appears probable that a continuous range oi even largerring phosphates is also present.144 The thermal dehydration of alkali-metaldihydrogen monophosphates has been investigated and similar studiesindicate that, with the exception of sodium trimetaphosphate Na,P30,, allthe tri- and tetra-metaphosphates of lithium, sodium, potassium, andammonium and their hydrates are thermally unstable; five types of thermalbehaviour were recognized.145 The first complete X-ray structural analysisof a fibrous colloidal metaphosphate has been carried out on rubidiummetaphosphate, which was shown to consist of continuous chains of (PO,),n-which spiral round the b axis of the crystal with a repeated pattern everytwo PO, The crystal structures of Maddrell's salt (NaPO,), andof lithium and sodium polyarsenate (MASO,).are somewhat similar to thisbut differ in the orientation of the chains and their repeat-patterns.147Phosphoric triamide OP(NH,), may be prepared by the reaction ofphosphorus oxychloride with liquid ammonia ; the use of substituted oxy-chlorides leads to the alkylamides of ortho- and thio-phosphoric acids andto the amides of phosphoric acid esters OP(0Et) (NH&, etc.148 Similarly,1313 W. L. Groeneveld, Rec. Trav. chim., 1956, 75, 594; V. Gutmann, ibid., p. 403;D.S. Payne, ibid., p. 620.139 I. A. Sheka and B. A. Voitovich, Zhzw. neorg. Khim., 1956, 1, 964.140 E. M. Larsen and L. J. Wittenberg, J . Amer. Chem. SOC., 1955, 77, 5850.141 L. A. Nisel'son and B. N. Ivanov-Emin, Zhur. neorg. Khim., 1956, 1, 1766.142 V. V. Dadape and M. R. A. Kao, J . Amer. Claem. SOC., 1955, 7'7, 6192.143 J. R. Van Wazer and E. J. Griffith, ibid., p. 6140.144 J. R. Van Wazer and E. Karl-Kroupa, ibid., 1956, 78, 1772; J. F. McCullough,145 E. Thilo and H. Grunze, 2. u+?.org. Chem.. 1955, 281, 262, 284.146 D. E. C. Corbridge, Acta Cryst., 1956, 9, 308.1 4 7 K. Dornberger-Schiff, F. Liebau, and E. Thilo, ibid., 1955,8,752 ; F. Liebau, ibid.,148 M. Goehring and K. Niedenzu, Chma. Brv , 1956, 89, 1768.J. R. Van Wazer, and E. J.Griffith, ibid., p. 4528.1951, 9, 811; W. Hilmer, ibid., p. 87.KEP.-VOT.. 1.111 st3 INORGANIC CHEMISTRY.pyrophosphoryl chloride gives the tetra-amide of diphosphoric acid(NH,),PO*O*PO(NH,),. This is isotypic with the tetra-amide of imidodi-phosphoric acid (NH,),PO*NH~PO(NH,), which can be prepared fromphosphoric triamide by splitting out ammonium chloride with hydrogenchloride : 2(NH2),P0 + HC1+ (NH,),PO*NH*PO(NH,), + NH,CI. Somepenta-amide of di-imidotriphosphoric acid(NH,),PO*NH*PO( NH,)*NH-PO( N H2) ,is also formed.149 On the other hand, when phosphoric triamide reactswith phosphorus oxychloride the tetramer of orthophosphoric amide imide(9) may be obtained via the chloride intermediate : l503PO(NH,), + POCI, + P4H,oO4N,CI + 2NHdClN H,P,Hl0O4N,CI __t P4HI2O4N8y 2 y 4 2 NaO, yNk!, ,ONaO=P-NH-P=OI I 0 4 P o (10)HN NH( 9 ) YH NH IO=P-NH-P=OI I / ** NH2 NHz NaOSodium monoamidophosphate Na2P03NH2, when heated in vacuuiii at210" for several days, lost ammonia -to give tetrasodium imidodiphosphateNa,(PO,*NH*PO,) which is isotypic with the pyrophosphate Na,P,O,.Further heating to 450" yielded sodium nitrilotriphosphate (Na,P0,),N.151Similarly when sodium diamidophosphate was heated in vacuum to 160°,diamido-imidophosphates of general formula Na,P,O,,(NH) ,- I(NH,)2 (1 1)were formed where IZ = 2-6. Treatment of the products with sodiumnitrite gave sodium imidophosphates of formula Na, + 2P1102n 2(NH), -(lZ).152 The reactions may be written as follows:......... ONa ONa ONa I ............ONa I .. ONa I I I '. I .*.ONaH ~ N - P-NH.~ + H ~ N ~ P-NH:;' + -.--H~N;- P - N H ~ - (n- I NH) + H~N-P~NH~P-NH .. -..P-NH~ It ........... . * I 1 . . . . . . . . * I 1 II II II0 ( 1 1 ) 0 0 0 0ONa ON a ONa ONaI I I 1II II II II0 0 0 0 (12)H~N-P-NH..*-.-P--NH2 + 2NaN02 + 2H20+ ZN2 4- NaO-P-NH*.*-** P-ONaContrary to assertions in the older literature it now appears that hydrolysisof sodium trimetaphosphimate (10) tends to occur by replacement of thering-NH groups by oxygen atoms ; chain imidophosphates are never presentin large a m 0 ~ n t s . l ~ ~R. Klement and L. Benek, 2. anorg. Chem., 1956, 287, 12.149 M. Goehring and K. K. Niedenzu, Chem. Ber., 1956, 99, 1171; see also1-50 M. Goehring and K. Niedenzu, Chem.Ber., 1956, 89, 1774.151 R. Klement and G. Biberacher, 2. amrg. Chem., 1956, 283, 246162 Idew, ibid., 1950, 285, 74.l53 A. Narath, F. H. Lohman, and 0. T. Quimby, J . Amer. Chem. Soc., 1956, 78,4493ADDISON AND GREENWOOD : MAlN GROUPS. 99X-Ray analysis has shown that the compound KAs,O,I has a new typeof layer structure with the following layer sequence parallel to the G axis :. . . I-2As-30-K-30-2As-I . . . ; the As-0 distance corresponds to covalentbonding.lM Arsenic(II1) selenide reacts with liquid ammonia to give asoluble metaselenoarsenite and an insoluble amidoselenide according to theequation As,Se, + 2NH, + NH,AsSe, + AsSeNH2, whereas the corre-sponding arsenic(II1) sulphide gives an imido-derivative : As,S, + 2NH, ----tAs,S,NH + NH,HS.155Two new antimony salts are described: Rb2SbBr5 and Rb,Sb,Br,,.The first is prepared by removing bromine vapour from solid Rb,SbBr,, andthe second by adding bromine to Rb,Sb,Br,.156 Various derivatives ofliexafluoro- and hexachloro-antimonic acids have been made.15' Additionof chlorine to tristrifluoromethylantimony Sb(CF,), gives the compound(CF,),SbCl, which reacts with water to form a mono- and a di-hydrate; asolution of tristrifluoromethylantimonic acid H(CF,),Sb( OH),, which isunique in being the only known strong monobasic acid of antimony(v), canalso be is01ated.l~~ Antimony pentachloride reacts with dialkyl sulphites,(RO),SO, to give C1,SbOR.157 Reaction with a solution of sulphur trioxidein sulphuryl chloride yields pyrosulphuryl chloride and the new compoundSb,CI,SO, which may be formulated as the salt (SbC14+)2S042-.159X-Ray powder photographs show that " sodium metabismuthate '' hasthe ilmenite structure and is best described as sodium bismuth(v) trioxide.160Group V1.-The stereochemistry of the elements in Group VI has beenreviewed.161 The Raman spectrum of the hydroxonium ion H,O+ isreported for the first time,lG2 and the ion is now recognized as a latticecomponent in several hydrated sulphates and phosphates of iron analogousto ferrous ammonium salts.lG3Physicochemical measurements continue on the sulphuric acid system,164and the work has been extended to solutions in disulphuric acid.165 A re-investigation of the system HN0,-H,SO,,nSO, establishes the identity oflive compounds in the range n < 1 ; when n > 1 nitronium hydrogen tetra-sulphate is formed (N02,HS,013).166 With dioxan, sulphuric acid forms thecompound H,S0,,C4H,02 which melts at 100" and has a conductivity of2 x lo-, ohm-l ~ r n .- l . l ~ ~ Two new incongruently melting compounds have154 2. Galdecki, Roczniki Chem., 1956, 30, 355.156 G. Brauer and Ti.-D. Schnell, ibid., 1956, 283, 49.15' A. Meuwsen and H. Mogling, ibid., 1956, 285, 262.158 H. J. Emeleus and J. H. Moss, ibid., 1956, 282, 24.159 R. Appel, ibid., 1956, 285, 114.160 B. Aurivillius, Acta Chem. Scand., 1955, 9, 1219.161 S. C. Abrahams, Quart. Rev., 1956, 10, 407.162 J. T. Mullhaupt and D. F. Hornig, J. Chem. Phys., 1956, 24, 169; see also D. J.Millen and E.G. Vaal, J., 1956, 2913.N. V. Shishkin and Ye. A. Krogius, Zhur. neorg. Khim., 1956, 1, 1252; see alsoF. Halla and E. van Tassel, Natzwwiss., 1956, 43, 80.164 R. J. Gillespie and J. V. Oubridge, J., 1956, 80; R. Flowers, R. J. Gillespie, andS. Wasif, ibid., p. 607; R. Flowers, R. J. Gillespie, and J. V. Oubridge, ibid., p. 1925;R. J. Gillespie and R. C. Passerini, ibid., p. 3850.165 J. R. Brayford and P. A. H. Wyatt, Trans. Faraday Soc., 1956, 52, 642.lo6 V. A. Usol'tseva, Zhur. priklad. Khim., 1956, 29, 302, 306.167 Ya. F. Mezhennyi, J . Gen. Chenz. (U.S.S.R.), 1956, 26, 397.H. Behrens and L. Glasser, 2. anorg. Chenz., 1956, 282, 12100 INORGANIC CHEMISTRY.been detected in the binary system water-selenic acid : H2Se0,,2H,0,m. p. -24", and H2Se0,,6H,O, m. p.-68.4°.168 Thermal analysis of thesystem water-selenium trioxide also reveals two new compounds : H2Se,0,,m. p. 18.8", and H,Se3OIl melting incongruently with a peritectic temper-ature 169 of 25.4".A single-crystal structure analysis of sodium dithionite Na,S,O, revealsthat the anion consists of two SO,- groups joined by a very long S-S bond(2.39 A) ; the sodium ions are also in an unusual, approximately square,co-~rdination.~~~ A considerable amount of work is being published on thechemistry of the sulphanes H,S, and the chlorosulphanes S,C1, and many ofthe lower members of these series (n < 6) can be obtained reasonably pure.171Fluorosulphites are prepared by the addition of gaseous sulphur dioxideto alkali-metal or tetra-alkylammonium fluorides, the reaction being moreready the larger the cation : M F + SO, MS0,F. The fluorosulphiteion, which is isoelectronic with the chlorate ion, is stable in an atmosphereof SO, up to 150" but above this temperature it reacts to give the corre-sponding fluorosulphate : 2MS0,F + SO, --+ ZMSO3F + S.Fluorineand chlorine convert the compounds into S0,F2 and SO,ClF, and a phasestudy of the system HF-SO, demonstrates the existence of the parent acidHSO,F, m. p. -84°.172 The amide of fluorosulphurous acid SO(NH,)F isobtained from ether solutions as the product of the reaction of ammoniawith a large excess of thionyl fluoride; the volatile compound soon forms asolid yellow linear polymer [OS(NH,)F].. Primary amines tend to reactanalogously but the product OS(NHR)F readily splits off hydrogen fluorideto give thionyl imines OSNR ; secondary amines yield stable dialkylamidesof fluorosulphurous acid OS(NR,)F.173The generic relation of pyrosulphuryl fluoride S,05F, as the anhydride offluorosulphuric acid HS0,F has at last been established by using arsenic(v)oxide as a mild dehydrating agent; the reaction proceeds at 300" via theintermediate formation of a volatile arsenic fluorosulphonylfluoi-ide : 174IOHSO3F + As206 __t 2AsF,(SO,F), + HzSO, + HZ0~AsF~(SO~F)~ - 3SaO6Fz + As,O,F,Earlier work on the ammonolysis of pyrosulphuryl choride which had beeninterpreted on the basis of the reaction S,O,Cl, + 6NH, + 2NH,C1 +(NH4)2[S205(NH)2] could not be confirmed and the reaction is now formu-lated as 1752SzOjCIz + I2NHS- 4NHdCI + (NH,)SO,NH, + SO,(NHZ)Z + NH,*SOg.N(NH4)*SO,NH4168 G. Vuillard, Compt.rend., 1956, 242, 1326.189 K. DostAl, COX Czech. Chem. Comm., 1955, 20, 1033; Chem. Listy, 1955, 49,633 ; see also K. DostAl and M. Cernohorsky, ibid., 1956, 50, 702.17O J. D. Dynitz, Acta Cryst., 1956, 9, 579.171 F. Feller, W. Laue, and J. Kraemer, 2. a n o ~ g . Chem., 1955, 281, 151; F. FehQand G. Rempe, ibid., p. 161; F. Feh6r and L. Meyer, 2. Naturforsch., 1956, l l b , 605;F. FehCr and W. Laue, 2. anorg. Chem., 1956, 287, 45; H. P. Meissner, E. R. Conway,and H. S. Mickley, I n d . Eng. Chem., 1956, 48, 1347.172 F. See1 and L. Riehl, 2. anorg. Chem., 1956, 282, 293.173 M. Goehring and G. Voigt, Chem. Ber., 1956, 89, 1050.174 E.Hayek, A. Aignesberger, and A. Engelbrecht, Monatsh., 1956, 86, 735.175 R. Appel, G. Voigt, and E . H . Sadelr, Naturwiss., 1966, 43, 496ADDISON AND GREENWOOD : MAIN GROUPS. 101The last compound is the diammonium salt of a formerly unknown imido-sulphuric acid, and is also formed by the ammonolysis of trisulphurylfluoride : 1752SaOeFZ + IONH:,ZNH,SO,F + 2HF + NH,SO,NH, + SO,(NH,), + NH,*S02.N(NH,).SOa*NH,On the other hand ammonolysis of trisulphuryl chloride appears to giveNH,SO,NH,, SO,(NH,),, and the corresponding triammonium salt(NH4)JN (SO,),]. 17G Finally, NN'-dimethylsulphamidedisulphuric acid an-hydride (13) is completely ammonolysed by ammonia to give sulphamide,dimethylsulphamide, N-methylsulphamic acid, and amidosulphuric acid.17sAll these experiments indicate that the S-0-S system is much less stabletowards ammonlysis than the P-0-P grouping.Sulphur trioxide reacts with cyanogen chloride CNCl to give three newcompounds : N-carbonylsulphamyl chloride OC=N*SO,Cl, which hydrolysesto CO,, NH,.SO,H, and HC1; the corresponding derivative of pyrosulphuricacid OC=N*SO*O*SO,Cl; and the cyclic compound (14).177 Thiazyl bromide(NSBr), reacts with potassium amide to give a yellow reactive solid K,N,Swhich may be considered as a derivative of sulphur di-imide S(NH),.From thiazyl chloride (NSCl), and mercuric iodide in liquid ammonia thecorresponding salt HgN,S was prepared.17*The chemistry of sulphur nitride and its derivatives has been revie~ed.17~Disulphur dinitride can be obtained by the thermal decomposition of tetra-sulphur tetranitride under very carefully controlled conditions ; its structureis thought to be S=N-S=N.lG0 The formation of S,N,Cl from S,N, andacetyl chloride or sulphur chloride is ascribed to traces of free hydrogenchloride in the reagents.lG1 The thermal decomposition of SN,F, gives amixture of sulphur tetrafluoride, nitrogen, and the colourless gas SNF whichis the monomer of (SNF), mentioned in last year's Report (p.117). Undermilder conditions SN,F, disproportionates into SNF and SNF,.l82 The lastcompound, which is the most stable of the sulphur-nitrogen fluorides m-ayalso be prepared by the reaction of a gaseous mixture of SNF and SN,F2with silver difluoride; the sulphur is in the +4 oxidation state and thestructure of the compound is therefore F,S=NF in contrast with thio-phosphoryl fluoride which is S=PF3.ls3+176 H.-A.Lehmann and G. Ladwig, 2. anorg. Chem., 1956, 284, 1.1 7 7 R. Graf, Chern. Ber., 1956, 89, 1 0 7 1 .178 W. Berg, M. Goehring, and H. Malz, 2. anorg. Chem., 1956, 283, 13.179 M. Goehring, Quart. Rev., 1956, 10, 437.160 M. Goehring and D. Voigt, Z . anorg. Chem., 1956, 285, 181.181 A. G. MacDiarmid, J . Amer. Chem. Soc., 1956, 78, 3871.182 0. Glemser and H. Haeseler, 2. anorg. Chem., 1956, 287, 54.18s 0. Glemser and H. Schroder, ibid., 1966, 284, 97102 INORGANIC CHEMISTKY.The tetrafluorides of sulphur and selenium form solid 1 : 1 additioncompounds with boron trifluoride melting at 80" and 46", and there are in-dications that tellurium tetrafluoride reacts similarly.Addition compoundsof these tetrafluorides with arsenic and antimony pentafluorides are alsodescribed.184 A convenient preparation of tellurium tetrafluoride fromtellurium dioxide and selenium tetrafluoride is reported.lS5 The fluorinationof tellurium has been studied under a variety of conditions ; TeF,, TeF,, andTe,F,, were obtained. In the presence of tellurium dioxide a telluriumoxyfluoride Te302F14 is also obtained which may be formulatedTeF5*O*TeF4*O*TeF5 ; this compound has a ratio of molecular weight toboiling point of 1.67 and is therefore even more volatile for its molecularweight than Te,F,,, which previously had the highest value for this ratio(1.36) of any known compound.Another product of the reaction appearsto be Te,05F2,, i.e., TeF5[O*TeF4],*O~TeF5.1s6The extraction of polonium(1v) from nitric acid into ethers depends on thepresence of reducing agents such as SO,, H20,, N2H4, NH20H, and organicperoxides; in the absence of these agents negligible extraction occurs in thedark.187 The preparation of a basic sulphate of polonium 2P002,S03, abasic selenate 2PoO,,SeO,, and a less stable disulphate Po(SO4), is described,and these reflect the increased basicity of polonium compared with itslighter congeners. la8 Polonium tetraiodide has been prepared by directreaction of the elements at 40°/1 mm., by the reaction of PoO, and HI at200", and by the. reaction of the dioxide with aqueous hydriodic acid.Addition of czsium iodide gives a black precipitate of the hexaiodopolonateCs2PoI6 which is isostructural with C S , T ~ I , .~ ~ ~ The potential of the poloniumelectrode (polonium deposited on gold in contact with a solution of Porv inN-HNO,) against a saturated calomel electrode is E, = -/-0.?'6 v.lgoGroup VII.-The purification of hydrogen fluoride in an apparatus con-structed of Fluorethene plastic leads to samples of considerably lowerconductivity than previously obtained; the lowest value was 1.6 xohm-l crn.-l at 0" compared with the accepted vahe of 1-4 x at - 15'.191Antimony pentafluoride behaves as an acid in hydrogen fluoride (SbF, +2HF -e H2Ft + SbF,-) and the mobilities of these ions, together withthose from the strong electrolytes NaF, KF, and NaSbF, have been deter-mined at infinite dilution.The low value for the hydrogen ion eliminatesthe possibility of a chain mechanism involving this species but the rather largemobility of the fluoride ion may indicate an abnormal process for this ion.lg2The fluorides of titanium, niobium, and tantalum are good electron acceptorsin hydrogen fluoride in the sense that they favour the reaction m-xylene +N. Bartlett and P. L. Robinson, Chew. and Ind., 1956, 1352.lE5 R. Campbelland P. L. Robinson, J . , 1956, 785.186 Idem, ibid., p. 3454; see also G. Hetherington and P. L. Robinson, ihid., I>. 3682187 J. Danon and A. A. L. Zamith, Nature, 1956, 177, 746.188 K. W. Bagnalland J. H. Freeman, J., 1956, 4579.189 K.W. Bagnall, R. W. M. D'Eye, and J. H. Freeman, ibid., p. 3385; see also100 K. W. Bagnall and J. H. Freeman, J., 1956, 2770.191 M. E. Runner, G. Balog, and M. Kilpatrick, J . Amer. Chem. Soc., 1956, 78, 5183.182 M. Kilpatrick and T. J. Lewis, ibid., p. 5186.for viscosity of Te,F,,.0. M. JankoviC, Bull. Inst. NucZear Sci. Boris Kidrich, 1956, 6, 143;\I>l)ISON AND GREENWOOL) MAIN GKOUPS. 103H F + (m-xylene H)+ + F- by removing the fluoride ions according toreactions like F- -t NbF, + NbF,-. Phosphorus pentafluoride is lesseffective, and the fluorides of Ba, Si, PbII, SbIII, BPI1, ZrIV, Cr1IT, WF*,and Zn are inactive.lg3Hydrogen chloride forms a hexahydrate, m. p. - 70.0", in addition to theknown di- and tri-hydrates.lg4 The electron-donor capacity of x orbitals inunsaturated hydrocarbons has been studied by using hydrogen chloride as aconvenient, small, acceptor molecule.Phase diagrams with olefins show thepresence of low-melting addition compounds with one and two mols. of acid,acetylenes form compounds at these ratios and also with four mols. of acid,whereas aromatic hydrocarbons tend to form 1 : 1 compounds only.lg5The thermal decomposition of dichlorine hexaoxide in the presence offluorine gives a 70% yield of chloryl fluoride C10,F. The hexaoxide de-composes according to the equations C1206 + ZlO, 2C10, + 0, ;neither Cl,06 nor ClO, reacts with fluorine but the dioxide does and indeedchloryl fluoride may be prepared by the direct reaction of undiluted chlorinedioxide and fluorine.lg6 Perchloryl fluoride ClO,F, which was recentlyobtained in small yields either by electrolysis of perchlorates in H F or bydirect fluorination of chlorates, has now been prepared in 67% yield by thereaction of perchlorates with fluorosulphuric acid. lg7 It is a colourless,inert, thermally stable gas (m. p. -146", b. p. -47.5") in contrast to C10,Fand ClO,OF which are explosive or highly reactive. Perchloryl fluoridereacts slowly with ammonia to give ammonium imidoperchlorate :C10,F + 3NH, + NH,F -t NH,NHC10,.lg8 Analysis of the vibrationspectrum and rotational fine structure of ClO,F indicates a central C1 atomwith the 0 atoms at the base and the F atom at the apes of a trigonalpyramid, FClO,, but the absence of microwave absorption suggests that themolecular dipole is very small and probably much less than 0.09 D.lg9Fluorine fluorosulphonate, prepared by the action of fluorine on sulphurtrioxide in the presence of silver difluoride, is a reactive oxidizing agent,m.p. --158.5", b. p. -31.3"; its chemical reactions and infrared spectrumconfirm the structure S02F*OF.200 The catalytic fluorination of thionylfluoride over silver difluoride yields thionyl tetrafluoride F,S=O (m. p. -99.6",b. p. -49-0") and pentafluorosulphur hypofluorite F,S-OF (m. p. -86-0",b. p. -335.0"); the structures were deduced from chemical reactions andinfrared spectra,201 and confirmed by nuclear magnetic resonance.202The electric dipole moment of gaseous bromine trifluoride suggests aplanar T-shaped molecule similar to that found for chlorine trifluoride.,N193 D.A. McCaulay, W. S. Higley, and A. P. Lien, J. Amer. Chem. SOC., 1956, 78,3009.194 G. Vuillard, Compt. rend., 1955, 241, 1308.195 D. Cook, Y. Lupien, and W. G. Schneider, Canad. J . Chem., 1966, 34, 955, 964.1913 A. J. Arvia, W. H. Basualdo, and H. J. Schumacher, 2. anorg. Chew., 1056, 286,197 G. Barth-Wehrenalp, J . Inorg. Nuclear Chem., 1956, 2, 266.198 A. Engelbrecht and H. Atzwanger, ibid., p. 348.199 R. P. Madden and W. S. Benedict, J . Chem. Phys., 1956, 25, 594; D. R. Lideand D. E. Mann. ibid., p. 595.200 F. B. Dudley, G. H. Cady, and D. F. Eggers, J . Amer. Chem. SOC., 1956, 78, 290.201 Idem, ibid., p. 1553.202 F. B. Dudley, J. N. Shoolery, and G. H. Cady, ibid., p.568.tos M. T. Rogers, R. D. P r i i e t t , and J. L. Speirs, ;bid., 1955, 77, 5280.58; see also J. E. Sicre and H. J. Schumacher, ibid., p. 232104 INORGANIC CHEMISTRY.There are two congruently melting compounds in the system bromine tri-fluoride-antimony pentafluoride ; BrF,,SbF,, m. p. 129.8", and BrF3,3SbF5,m. p. 33.5" ; and also two incongruently melting compounds, 3BrF,,SbF5,m. p. -16.3", and 3BrF,,2SbF5, m. p. 3043".204 An X-ray crystal-structuredetermination has shown that the tetrafluorobromate ion in KBrF, is tetra-hedral 205 in contrast to the tetrachloroiodate ion in KICl, which is planar.The vapour pressures of the addition compounds of bromine trifluoride withpotassium bromide and antimony pentabromide (KBrF, and BrF,,SbF,) havebeen measured up to 350" and are of such a magnitude that the compoundscan be used for high-temperature fluorinations in closed reaction vessels evenup to 500°.206 The electric dipole moments of bromine pentafluoride 207 andiodine pentafluoride 203 are consistent with a square-based-pyramidal struc-ture and exclude trigonal-bipyramidal and plane-pentagonal symmetries.The phase diagrams of the systems bromine pentafluoride-hydrogenfluoride 208 and iodine pentafluoride-hydrogen fluoride 209 each show a singleeutectic; there is no evidence of compound formation.The crystal structure of x-iodine monochloride involves ICl molecules intwo non-equivalent sets; these molecules, of bond length 2.37 and 2.44 Arespectively, are arranged in puckered zigzag chains with strong interactionbetween the molecules in individual chains but with normal van der Waalsdistances between the chains.210 A detailed study of the crystal structuresof the addition compounds of iodine monochloride with pyridine 211 anddioxan has shown that the N-I-C1 bond in Py,ICl and the 0-I-C1 bondin C,I-I8O2,2ICl are both linear and non-ionic By contrast, $-chlorobenzeneiododichloride C1*C6H,*ICI, has a linear Cl-I-Cl group at right-angles to theC-I bond, the whole molecule being planar.The structure is allied to thatof benzene iododichloride except that in this compound the ICl, group isalso at right-angles to the plane of the benzene ring.213 (It may benoted that these two iododichlorides together with chlorine trifluoride andbromine trifluoride constitute the four known examples of T-shapedcovalent bond angles so that chlorine, bromine, and iodine can all adoptthis symmetry.)The cryst a1 structure of t etraeth ylammonium hept aiodide Et ,N I isbuilt up of I,- ions and I, molecules with large holes for the Et,N+ cations;the compound therefore is best written as Et,N+I,-,212; there is no indic-ation of an I,- i0n.214 The structure of tetramethylammonium enneaiodide204 J.Fjscher, R. Liimatainen, and J. Bingle, J . Amer. Chenz. Soc., 1956, 78, 5848.805 S. Siegel, Acta Cryst., 1956. 9. 493.208 I. Sheft, A. F. Martin, and J. J. Kstz, J . Amer. Chem. Soc., 1956, 78, 1557.807 M. T. Rogers, R. D. Pruett, H. B. Thompson, and J. L. Speirs, ibid., p. 44;208 M. T.Rogers, J. L. Speirs, and M. B. Panish, J . Amer. Chenz. SOL, 1956, 78,209 M. T. Rogers, J . L. Speirs, M. B. Panish, and H. B. Thompson, ibid., p. 936;210 K. H. Boswijk, J. van der Heide, A. Vos, and E. H. Wiebenga, Acts Cryst., 1956,211 0. Hassel and C. Rsmming, Acla Chevz. Scand., 1956, 10, 696.212 0. Hassel and J . Hvoslef, ibid., p. 138.213 D. A. Bekoe and R. Hulme, Nature, 1956, 177, 1230.214 E. E. Havinga and E. H. Wiebenga, PYOC. k . ned. Akad. Wetenschafi., 1055, 58, B,see also M. T. Rogers and J. L. Speirs, J . Phys. Chem., 1956, 60, 1462.3288.see also G. Hetherington and P. L. Robinson, J . , 1956, 3681.9, 274.412ADDISON AND GREENWOOD : THE TRANSITION ELEMENTS. 105Me,NI, is more complicated. It consists of planes of densely packed iodineatoms which contain 5/9ths of the iodine atoms in the compound and withinwhich there is some justification for singling out 1,- ions similar to but lesssymmetrical than, the V-shaped ions in h'Ie,NI,.Between these planes,which are 9.1 apart, lie Me,N+ cations each surrounded by six I, molecules ;these molecules also lie between the main planes, normal to them and weaklyassociated with them. Except for the I, molecules between the planes, all1-1 distances are considerably longer than in I, and are comparable withthose found in 13-, 15-, and 182-.2153. THE TRANSITION ELEMENTS.A large proportion of the work published during the year on the chemistryof the transition elements has been concerned with complexes. Work whichillustrates the structure or general properties of particular types of complexis correlated under the heading " Complexes." The remaining chemistryof the transition elements is then discussed systematically ; these sectionscontain references to complexes which are more directly concerned with thechemistry of the particular elements.The paramagnetic resonance ofcrystalline solids containing ions of the transition groups has been reviewed.216The proceedings of the International Conference on Co-ordination Com-pounds (Amsterdam, 1955),217 and a symposium on the chemistry ofcomplex compounds,218 have been published. \V. Klemm has reviewedthe present position regarding valency ranges in the transition elements,particularly the abnormal valencies shown in their oxygen and fluorinec0mplexes.~19Complexes.-Import ant advances have been made in the elucidation ofthe mechanism of substitution in octahedral (mainly CoIII) complexes, and therelated stereochemical changes."O They involve kinetic studies which lieoutside the scope of this Section.The stability and the spectra of complexesof transition metal cations have also been discussed,221 with emphasis on theapplication of crystal field theories.z22The well-known reducing and catalytic properties of a solution of ironpentacarbonyl in aqueous hydroxide solutions are interpreted satisfactorily onW. J. James, R. J. Ilach, D. French, and R. E. Rundle, Acla Cryst., 1955, 8,216 K. D. Bowers and J. Owen, Reports Progr. Phys., 1955, 18, 304; see also Discuss.217 Rec.Trav. chim., 1956, 75, 557-924.218 Chem. Weekblad, 1956, 52, 193.219 W. Klemm, Bull. SOC. chim. France, 1956, 1325.220 S. Akperger and C. K. Ingold, J., 1956, 2862; F. Basolo, W. R. Matoush, andR. G. Pearson, J . Amer. Chem. SOC., 1956, 78, 4883; R. K. Murmann and H. Taube,ibid., p. 4886; A. W. Adamson and F. Basolo, Acta Chena. Scand., 1955, 9, 1261 ; andrefs. therein.814.Faraday Soc., 1955, 19.221 H. Irving and H. Rossotti, ibid., p. 72.222 C. K. Jm-gensen, ibid., p. 887; R. J. P. Williams, J . , 1956, 8 ; P. George, D. S .McClure, J. S. Griffith, and L. E. Orgel, J . Chem. Phys., 1956, 24, 1269; C. J. Ballhausen,Rec. Trav. chim., 1956, 75, 666; and refs. therein106 INORGANIC CHEMISTRY.the basis of an intermediate dimeric ion (15) formed from two [Fe(CO),H]-ions which is oxidised to ion (16) : 223(15) (16)Dirhenium decacarbonyl undergoes a similar reaction : 2241 K[ (OC),R\;/Re(CO), Lo\ R*2(CO)Io + 3KOH + H 2 0 + CO + K2CO3-t 2H1( 1 7 )The compound (17) is diamagnetic, each sexaco-ordinate Re atom maintain-ing its inert-gas configuration.The same product is formed from thecarbonyl chloride :Re,(CO),O,HK + 2KCI + 2CO + H,Oand with thiophenol the carbonyl chloride gives the non-electrolyte2Re(CO),CI + 3KOHll(CO)4Re(S'C6H5)212*The position of the hydrogen atom in cobalt carbonyl hydride has been - -further examined from its infrared spectrum. In the absence of an 0-Hstretching vibration, the spectrum is consistent with a model in which thehydrogen atom bridges three CO groups; its covalent bonding to the COgroups is stronger than to the Co atom.225The compound Ru(CO),I, has high stability and low vapour pressure, inmarked contrast to the iron compound.226 This is consistent with a halogen-bridged polymeric structure (18) in which each Ru atom may also achieveinert-gas configuration.The chemistry of mixed complexes containing isoelectronic groups hasbeen developed.Nitrosylcyano-complexes of iron and nickel are known,and the corresponding cobalt complexes now isolated are correlated asfollows : 227KCN HCN[Co(NH,),NO]CI, __t K3[Co(CN),NO] ___t [Co(CN)dS- + $NzOIn the pentammino-complex the NO group has entered the complex as NO- ;the lower formal valency of the cobalt resulting from electron distribution togive NO+ is revealed by the reduction to nitrous oxide on replacement of theNO group.Again,KCNCo(CO),NO __t [Co(CN)(CO),(NO)]- --j- Co(CO),NO + [Co(CN),(CO)(NO)]-'CN-and [CO(CN),(CO)(NO)]~- __+ [Co(CN)3NOIS-which is directly analogous to the carbonyl nitrosyl.22s H. W. Sternberg, R. Markby, and I. Wender, J . Anzer. Chem. SOC., 1956, 78,224 W. Hieber and L. Schuster, 2. anorg. Chem., 1956, 285, 205.226 W. F. Edgell, C. Magee, and G. Gallup, J . Amer. Chem. SOC., 1956, 78, 4185,2Z8 R. J. Irving, J., 1956, 2879.227 R. Nast and M. Rohmer, 2. anorg. Chem., 1956, 285, 271.5704.4188; see also F. A. Cotton and G. Wilkinson, Chem. and Ind., 1956, 1305A1)I)ISON ANI) GREENWOOD THE TRANSITION ELEMENTS. 107A number of derivatives of iron and cobalt nitrosyl carbonyls withphosphorus, arsenic, and antimony alkyls and aryls are described.228 Theyinclude Co( NO) (CO) (PPh,) ,, Co (NO) (CO) , [As (C,H,Cl) J, Fe (NO),( PPh,),, andFe(NO),[P(OPh),],, and a carbonyl derivative is obtained by the reaction 229Hs[CO(CO),I~ + 2PPh3 HdCo(C0)3(PPhs)l2isocyanides give 1 : 1 replacement of the CO group in carbonyls.Withiron pentacarbonylCIH,-NC CHs.NCFe(CO)5 - Fe( CO)4,C2H5NC ___t Fe(CO)3C2H5NCCH3*NCThis class of compound has been ~urveyed.2~0 Reaction of rhodium tri-chloride with RNC (R = tolyl, 9-chlorophenyl, methoxyphenyl) givescompounds of formula [(RNC),Rh]Cl in which the Rh atom is formallyunivalent .231. The chemistry of metal acetylide complexes has been extended to includeIn liquid ammonia, the compounds analogous to ferro- and ferri-cyanides.following reaction occurs :6MCECR + Fe(SCN)?,4NH3(where M = K, Na and R = H, Me, Ph).in liquid ammoniaM4[Fe(C-CR),] + ZMSCN + 4NH3On reaction with gaseous oxygenand the FeIII product can be reduced again by reaction with a solution ofpotassium in liquid ammonia.232 An analogous series of CoII and COTITcomplexes has been prepared.2aThe trans-directing effect in platinous complexes has been furtherexamined.The elimination of groups in the trans position is attributed tothe high double-bonding capacity of the directing ligand, and occurs by anSN2 mechanism. This is supported by the infrared spectra of a series of squareplanar complexes.234 An electronic interpretation of the lability of groupstrans to the double-bonding ligand has been given which involves a distortedbipyramidal structure for the transition state.235 Advantage has been taken228 M.Malatesta and A. Araneo, -4Iti Accad. naz. Lincei, lie9id. Classc Sci. j s . Inat.229 W. Hieber and R. Breu, Angew. Chem., 1956, 68, 679.230 W. Hieber and D. von Pigenot, Chem. Ber., 1956, 89, 610, 616.231 L. Malatesta and L. Vallarino, J., 1956, 1867.232 R. Nast and F. Urban, 2. anorg. Chem., 1956, 287, 17.233 R. Nast and H. Lewinsky. ibid., 1956, 282, 210.234 J. Chatt, L. A. Duncanson. and L. M. Venanzi, J., 1955, 4456, 4461 ; see alsoD. B. Powell, J., 1956,4495; 0. Y . Zvyagintsev and Y. F. Karandasheva, Doklady Akad.Nauk, S.S.S.R., 1956, 108, 477.235 Id.E. Orgel, J . T w o ~ g . Nuclear Chem., 1956, 2, 137.nnt., 1956, 20, 365108 INORGANIC CHEMISTRY.of the labile nature of the group trans to an ethylene molecule to determineequilibrium constants for the reactionsand trans-C,H,,H20PtC12 + am + tmns-C,H,,amPtCl, + H20and thus the relative tendencies of a series of simple amines (am) to co-ordinate with the meta1.236 The possibility that the cyclobutadiene moleculecan be stabilised by combination with a transition-metal ion has beenexamined by molecular-orbital theory.237 An interesting olefin complex[C,H,,RhCl], is formed by reaction of rhodium trichloride with cycloocta-1 : 5-diene.238 When treated with an amine (am) itgives the mononuclear planar complex C8H1,,Rh amC1, and on treatmentC2H,PtC13- + am trans-C,H,,amPtCl, + C1-It has structure (19).OHwith cyclopentadienylsodium gives the novel derivative C,H,,,RhC,H,(m.p. 108'). Acetylene complexes of some transition metals have beenprepared, but structures are uncertain. The infrared spectrum of the knowncompound Fe,C,,H,O,, prepared by reaction of acetylene with iron carbonylhydricle, indicates that it is binuclear (80) and closely related to the nona-carbonyl. The two acidic hydrogen atoms are attached directly to oxygenatoms.239 A wide range of substituted acetylenes RCGCR, undergo thereactionRC-CR, + CO,(CO), (CO)~CO*RC-CR,*CO(CO)~ + 2CObut the multiplicity of the bonds connecting the two Co atomsthrough the acetylene has not yet been ascertained.240 The complexK[Cl3Pt ,Me,( 0H)C-CrC*C (OH) Me,] has been described.241There have been considerable developments in the chemistry of metal-cyclopentadiene complexes during the year, and many compounds are nowclassified according to whether they form sandwich-type bonds, ionic bondsbetween metal and C,H,- ions, or localised metal-carbon bonds.The twowell-known approaches to the structure of ferrocene-type compounds, i.e.,the single bond concept and that involving multiple bonding (and the attain-ment by the metal of the inert-gas structure), have been compared and arenot necessarily irreconcilable ; 242 in the series (C,H,)V(CO),, (C,H,)Mn(CO),,296 J. Chatt and G. A. Gamlen, J., 1956, 2371.237 H. C. Longuet-Higgins and L. E. Orgel, ibid., p.1969.238 J. Chatt and L. M. Venanzi, Nature, 1956, 177, 852.239 H. W. Sternberg, R. A. Friedel, R. Markby, and I. Wender, J . Amer. Chem. SOC.,240 H. Greenfield, H. W. Sternberg, R. A. Friedel, J. H. Wotiz, R. Markby, and241 S. V. Bukhovets, Izvest. Sekt. Platiny, 1955, No. 29, 55,242 J. W. Linnett, Trans. Faraday Soc., 1956, 52, 904.1956, 78, 3621.I. Wender, ibid., p. 120ADDISON AND GREENWOOD : THE TRANSITION ELEMENTS. 109(C,H,)Co(CO),, C,H,NiNO there is agreement that only the latter concept istenable.243 A detailed crystallographic examination of ferrocene, (x-C,H,),Fe,gives the Fe-C distance, d(Fe-C), as 2.045 & 0.010.02 A; electron-diffraction studies give d(Fe-C) 2-03 & 0.02 andd(C-C) 1.43 & 0.03 H1.245 Crystallographic data are also available fordicycZopentadienylchromium( 11) 246 and for molybdenum, tungsten, and ironcyclopentadienyl ~arbonyls.~*~More metals have been added to the list of those forming cyclopentadienylcomplexes; the usual method of preparation is by reaction of sodiumpentadienide with a salt (e.g., halide) of the metal in an organic solvent(e.g., tetrahydrofuran or dimethylformamide).Scandium, yttrium, lanthan-um, and the lanthanide elements Ce, Pr, Nd, Sm, Gd, Dy, Er, and Yb givecrystalline solids of formula M(C5H5), ; the metal-to-ring bonds are ionic innature.248 Titanium dichloride gives dark green crystals of (x-C,H,),Ti,a ferrocene-type compound.249 The manganese compound (C5H5),Mn showsionic bonding, in contrast to the sandwich structure of neighbouring elements.This is related to the extra stability of the &In2+ ion, with its singly occupied3d orbitals.250 The Cu+ ion might be expected to form sandwich-bondcompounds of the type C5H5CuR, isoelectronic with C,H,NiNO, but theinfrared spectrum of the compound C5H5CuPEt, suggests that it should beformulated with a localised metal-carbon bond,251 as is the case with themercury compound (C,H,),Hg. The dipole moments of the tin252 andlead 253 compounds (C,H,),Sn and (C,H,),Pb, 1-01 D and 1.63 D, indicate thatthey are also normal organometallic compounds.Many derivatives of simple cyclopentadienyl complexes have beenprepared.and d(C-C) 1.403Dicyclopentadienyliron dicarbonyl is obtained by the reactionsBra C,H,Na(C,H,),Fe,( CO), __t 2C,H,Fe(CO),Br ___+_ C,H6Fe( C0)2C5H6Only one C,H, group is symmetrically bonded to the iron atom, and thecompound is useful in the synthesis of unsymmetrically substituted ferrocenederivatives2S4 The carbonyl hydrides C5H5M(C0),H (where A1 = Cr, Mo,W) have been prepared.The tungsten compound (m. p. 66') is the moststable.255 They represent fission of the dimeric complex by hydrogen, andare related in the same way as are the simple carbonyl and carbonyl hydrideof cobalt. The hydrides readily give salts of the anion [C,H,M(CO),]-.Two new nitrosyl derivatives C5H5Cr(NO),C1 and (C,H,),Mn,(NO), havebeen described.25G The former has a sandwich-bonded cyclopentadienyl243 L. E. Orgel, J . Inorg. Nuclear Chern., 1956, 2, 315.244 J.D. Dunitz, L. E. Orgel, and A. Rich, Acta Cryst., 1956, 9, 373.245 E. A. Seibold and L. E. Sutton, J . Chem. Phys., 1955, 23, 1967.246 E. Weiss and E. 0. Fischer, 2. anorg. Chem., 1956, 284, 69.247 F. C. Wilson and D. P. Shoemaker, Naturwiss., 1956, 43, 57.Z48 J. hl. Birmingham and G. Wilkinson, J . Awzer. Chem. Soc., 1956, 78, 42.249 A. K. Fischer and G. Wilkinson, J . Inorg. Nuclear Chem., 1956, 2, 149.250 G. Wilkinson, F. A. Cotton, and J. M. Birmingham, ibid., p. 95.251 G. Wilkinson and T. S. Piper, ibid., p. 32.252 E. 0. Fischer and H. Grubert, 2. Naturforsch., 1956, l l b , 423.253 Idenz, 2. anorg. Chern., 1956, 286, 237.254 B. F. Hallam and P. L. Pauson, J., 1956, 3030.255 E. 0. Fischer, W. Hafner, and H. 0. Stahl, 2. anorg. Chem., 1956, 282, 47.2 5 6 T.S. Piper and G. Wilkinson, J . Inorg. NucZear Chem., 1966, 2, 38, 136110 INORGANIC CHEMISTRY.group, with zero-valent chromium. Structure (21) whicli is suggested forthe latter compound involves the use of nitric oxide as a bridging group.Reaction of (21) with sulphur in carbon disulphide gives a disulphur deriv-ative (C,H,)Mn(NO)S, ; 257 this may represent a cyclopentadienyl derivativeof a Roussin-type salt (Z), with possible polymerisation by linkage throughsulphur at oms.(23) (21) (rl2)Whilst metal-to-carbon CJ bonds are unstable for most transition elements,the presence of a x-cyclopentadienyl ring on the metal so changes the orbitalsthat stable metal-carbon c bonds can be formed. Thus by reaction ofx-C,H,Cr( NO),I with Grignard reagents, x-C5HgMo(C0),H with diazomethane,or x-C,H,Fe(CO),Na with alkyl or aryl halides, a number of derivatives ofgeneral type x-C,H,M(CO),(NO),R have been isolated in which the alkyl oraryl group R is bonded directly to the An analogous silyl-ironcompound x-CSH,Fe(CO),SiMe, has an Fe-Si G bond.259cycZoPentadienylchromium-acetylacetone bromide (23) is novel in that acyclopentadienyl group is bonded to a transition metal which is also part ofa chelateUranium tetrachloride reacts with the sodium derivative of cyclopenta-diene to give the monochloride (x-C,H,),UC1.261 This compound does notreact with ferrous chloride in tetrahydrofuran and the metal-to-ring bondsare therefore not electrostatic.The compound is formulated [(C,H,),U] U-,the cation having three coplanar sandwich-type bonds a t angles of 120".Thorium forms cyclopentadienyl-metal halides analogous to those of titaniumand zirconium.261 Platinum forms a compound (C,H6),PtC1,, but lack of acharacteristic double-bond frequency in the infrared spectrum indicates thatthere may be cross-bonding between the two C,H, molecules.262The isolation of dibenzenechromium(O), (C6H,),Cr,263 in which theelectronic configuration of the chromium atom is the same as that of theiron atom in ferrocene, is of outstanding importance since it indicates thatthe orbitals of suitable transition metals can be filled with all the x-electronsof an aromatic system up to the configuration of the next inert gas.I t isprepared by heating together anhydrous chromic chloride, aluminiumpowder, aluminium chloride, and benzene.Hydrolysis of the product givesthe salt [Cr(C,H6)2]fC1-, which is reduced by sodium dithionite to brown-257 T. s. Piper and G. Wilkinson, J . Amer. Chem. Soc., 1956, 78, 900.258 Idem, J . Iizorg. Nuclear Chem., 1956, 3, 104.259 T. S . Piper, D. Lemal, and G. Wilkinson, Natuvwiss., 1956, 43, 129.260 J. C. Thomas, Chena. and Ind., 1956, 1388.2 6 1 L. T. Reynolds and G. Wilkinson, J . Inorg. Nuclear Chem., 1956, 2, 246.262 J. R. Doyle and H. B. Jonassen, J . Amer. Chem. soc., 1966, 78, 3965.263 E. 0. Fischer and W. Hafner, 2. Naturforsch., 1966, lob, 665ADDISON AND GREENWOOD THE TRANSITION ELEMENTS. 11 1black diamagnetic crystals of dibenzenechromium (m. p.284") which de-compose at 300" to metallic chromium and benzene.264 Crystallographicexamination shows the molecule to be centrosymmetrical, with parallelrings.265 Compounds containing toluene, &-xylene, tetralin, mesitylene, andhexamethylbenzene in place of benzene have also been prepared.265 A similarmethod with molybdenum pentachloride gives dibenzenemolybdenum(0)which is also diamagnetic and has the " doppelkegel structure.'' 266 Re-action with diphenyl gives bisdiphenylchromium iodide [Cr(C6H5*C6H5)2]I,26ithe magnetic properties and spectrum of which are identical with those of" tetraphenyl chromium iodide " prepared by Hein in 1919.268 Reactionstypical of the ferrocinium ion occur also with the Cr(C6H6),' cation; thusdibenzenechromium cyclopentadienylchromium tricarbonyl is found to bethe ionic compound [Cr(C6H6)~+[C5H5Cr(C0)3]- analogous to the cyclo-pentadienyl compound already known.269 The product of the reactionAICI,FeBr, + 2C,H,Me, + [Fe(C,H,Me3),]'+ + 2Br -is a niesitylene-iron(I1) cation which is isoelectronic with the neutralchromium(0)-mesitylene compound, and has the same structure.2i0The Scandium Group and Lanthanides.-By combination of fractionalhydroxide and carbonate precipitation with chromatographic separation ony-A1203, pure yttrium oxide (magnetic susceptibility -0.197 x 10-6/g.)containing < 0.002% of other lanthanides has been prepared.271 Theefficiency of scandium separations has been tested by using the 46Sc isotope;precipitation as the potassium double fluoride, ammonium double tartrate,or by disodium hydrogen phosphate is more efficient than precipitation ashydroxide, oxalate, or pyrophosphate.Solvent extraction of scandiumoxine chelate by chloroform can be made quantitative in one operation.272Conditions of cathode potential and pH have been defined for separation ofsamarium from gadolinium by electrolysis of the citrate complexes with alithium amalgam cathode, which is superior to sodium amalgam for thispurpose.273 The stability constants of lanthanide complexes with hydroxy-ethylethylenediaminetriacetic acid show little variation from samarium toerbium ; 274 separations on cation-exchange resins with 2-hydroxyethylimino-diacetic acid complexes are also described.275 Weight-temperature curvesfor thermal decomposition of the nitrates M(N03),,6H20 give the followingtemperatures for complete conversion into oxide : La 780"; Ce 450";Pr 505" ; Nd 830" ; Sm 750".276Lanthanum, cerium, praseodymium, and neodymium behave similarly264 E.0. Fischer and W. Hafner, 2. anorg. Chem., 1956, 286, 146.265 E. Weiss and E. 0. Fischer, ibid., p. 142.266 E. 0. Fischer and H. 0. Stahl, Chem. B e y . , 1956, 89, 1806.267 E. 0. Fischer and D. Seus, ibid., p. 1809; I?. Hein, ibid., p. 1816.268 Idem, Bey., 1919, 52, 195.269 E. 0. Fischer and H. P. Kogler, Angew. Chem., 1956, 68, 462.270 E. 0. Fischer and R. Bottcher, Chem Bey., 1956, 89, 2397.2 7 1 W. Fischer and K. E. Niemann, Z. anorg. Chem., 1956, 283, 96.272 R. C. Vickery, ./., 1956, 3113.173 E.I. Onstott, J . Anzer. Chem. SOC., 1956, 78, 2070.274 F. H. Spedding, J. E. Powell, and E. J. Wheelwright, ibid., p. 34.275 L. Wolf and J. Massonne, J . prakt. Chenz., 1956, 3, 178.2713 W. W. Wendlandt, Analyt. Chinz. Acfa, 1956, 15, 435112 IN ORGANIC CHEMISTRY.in their systems with hydrogen. For compositions between &I and MH, twosolid phases (metal and hydride) exist ; compositions MH, to MH, representa single solid phase, and in this range these elements, with samarium, forman isomorphous series of hydrides. The MH, hydrides have a fluorite-typestructure, and additional hydrogen is distributed in octahedral inter~tices.~"The deuterides of ytterbium and europium (which give maximum composi-tions YbDl.g8 and EuD,.,J are isostructural with hydrides of alkaline-earthmetals.278 An earlier claim that the hydride Gd,H, is formed on heatinggadolinium in hydrogen is not supported by detailed pressure-temperature-composition data.Two solid phases exist; the first has cubic structure ofideal composition close to GdH,, the second a hexagonal structure of com-position close to GdH,. The system is a counterpart of the plutonium-hydrogen system.279 New borides PrB,, SmB,, GdB,, and YbB, (iso-morphous with CeB,, ThB,, and UB,) have been prepared by heating theoxide M,O, with boron and carbon at 1500-1800", and their lattice constantsmeasured.280 They are less stable than the known borides MB,. The loweroxide of samarium, SmO, has been prepared by distillation from a Sni-Sm,O,mixture at 1100-1300" in an argon atmosphere and in complete absence ofoxygen.An oxide SmOo.,-,, was also obtained, which may imply thepresence of univalent samarium. The oxide EuO is prepared under similarconditions by heating a La-Eu,O, mixture.281Reaction of hydrogen chloride with ceric oxide (in dioxan) precipi-tates orange needles of hexachloroceric acid as the dioxan complexH,CeC16,4C,H802.282 Kinetic study of the reaction between ColI1 and CeIIIions in perchloric acid indicates that a perchlorate complex of CeIII takes partin the rate-determining step CeC10,2i' + CoOH2+ ---9 CeIV + COII."~ Incontrast to the ceric sulphate-hydrogen peroxide reaction, which is fast atpH (1.4, ceric perchlorate solutions above pH 0.7 contain part of theCeIV in the form of a colloidal polymer related to the dimer [Ce-O-CeI6+;this gives a coloured complex with hydrogen peroxide which decomposesDipyridinium cerium hexachloride is sufficiently stable to be dried in aslowly.284vacuum at 120".(C,H6N)2,CeCI, + 4Bu"OH + 6NH3+ Ce(OBuU)* + 2C,H,N + 6NH,CIOn use of isopropyl alcohol, the addition compound Ce(0Pr) ,,PrOH crystal-lises.The pure isopropoxide is used as starting material for the preparation,by alcohol interchange, of alkoxides Ce(OR), where R = Me, Et, Prn, Bun,Bui, Yt-pentyl, and Yteopentyl. Only the neopentyl oxide is volatile (sublimesat 260"/0-05 mm.).285 Apart from this case, the alkoxides resemble the.277 R. N. R. Mulford and C. E. Holley, J. Phys. Chem., 1955, 59, 1222; C.E. Holley,R. N. R. Mulford, F. H. Ellinger, TV. C. Koehler, and W. H. Zachariasen, ibid., p. 1226.278 W. L. Korst and J . C. Warf, Acta Cryst., 1956, 9, 452.279 G. E. Sturdy and R. N. R. Mulford, J . Amer. Chem. Soc., 1956, 78, 1083.280 B. Post, D. Moskowitz, and F. W. Glaser, ibid., p. 1800.281 H. A. Eick, N. C. Baenziger, and L. Eyring, ibid., p. 5147.282 S. S. Moosath and M. R. A. Rao, Current Sci., 1956, 25, 14; S. S. Moosath, Pwc.283 L. H. Sutcliffe and J . R. Weber, Trans. Faraday Soc., 1956, 52, 1225.284 M. Ardon and G. Stein, J., 1956, 104.285 D. C . Bradley, A. K. Chatterjee, and IV. Wardlaw, ibid., p. 2260.It undergoes the reactionIndian Acad. Sci., 1956, 43, A , 272ADDISOX AND GREENWOOD : THE TRANSITION ELEMENTS. 113zirconium derivatives in molecular complexity, but the thorium derivativesin their lack of volatility.Of the ceric secondary alkoxides Ce(OCHMe*R),only the tetraisopropoxide is volatile (sublimes at 160-170"/0~05 mm.) .286The Titanium Group.-At -17" titanium tetraiodide is converted byclinitrogen tetroxide into the anhydrous tetranitrate Ti(NO,),. This isunstable, evolving brown fumes at 10" to give the oxynitrate TiO(NO,),.Zirconium tetraiodide reacts ~imilarly.~~7 The preparation of titanyl amidein liquid ammonia, and some of its reactions, are summarised in the followingscheme.288KSCN KNH, KNHa350" I 000"TiO(NH& + (Ti0)3N2 __t Ti0 + N2TiO(S0,) + K,[TiO(SCN),] ___) TiO(NH,), + TiO(NHKhThe thermodynamic properties of the lower chlorides of titanium havebeen studied in detail.The heats of formation of TiCl,(s) and TiCl,(s) are-172.2 & 0.7 and -123.3 kcal,/mole from measurements of heats of solu-compared with -169.1 & 0.4 and -120-1 & 0.8 kcal./mole deter-mined by direct chlorination.29o The disproportionation of titanium di-chloride has also been r e - e ~ a r n i n e d . ~ ~ ~ ~ 291 The range of molecular additioncompounds which tetrachlorides of titanium-group elements form withorganic compounds has been extended. Fusion diagrams of titanium tetra-chloride with 15 monocarboxylic esters show 1 : 1 addition compounds, ofwhich the complex TiCl,,Me*CO,Me has the highest melting point ( 145°).292Dipole moments of complexes with esters and nitriies have been recorded.2s3Zirconium and hafnium tetrachlorides give with acetonitrile a solid phaseMC1,,2MeCN together with two liquid phases of variable composition ; themaximurn separation factor of hafnium and zirconium between the twophases is Hf/Zr = 1 ~ 8 .~ ~ ~The readiness with which the alkoxy-derivatives (RO),TiCl, - , areobtained by direct reaction of alkyl orthotitanates with titanium tetra-chloride depends upon the reaction medium. Each of the compounds inwhich = 1, 2, 3, or 4 forms an addition compound (RO),TiC1,-,,C,HloNH,and in piperidine the addition compounds are sufficiently stable to be usedin separation of individual products.295 The solvolysis MCl, 4- nROH +=(RO),,MCl,-, + nHCl in methyl or ethyl alcohol is more extensive withhafnium than with zirconium t e t r a c h l ~ r i d e .~ ~ ~ The chemistry of thoriumalkoxides Th(OR), has been extended to include 12-butyl, 92-pentyl, and286 D. C. Bradley, A. K. Chatterjee, and W. Wardlaw, J . , 1956, 3469.2 8 7 V. Gutinann and H. Tannenberger, filonatsh., 1956, 87, 421.288 0. Sclimitz-Dumont and F. Fiichtenbusch, 2. al-zorg. Chem., 1956, 284, 278.289 D. G. Clifton and G. E. MacWood, J . Phys. Chem., 1956, 60, 309, 311; B. S.2Qo W. F. Krieve, S. P. Vango, and D. M. Mason, J . Chem. Phys., 1056, 25, 519;291 A3. Farber and A. J. Darnell, ibid., p. 526.i92 Yu. A. Lysenko, 0. A. Osipov, and Ye. K. Akopov, Zhur. neorg. Khim, 1956,293 0. A. Osipov, J . Geia. Chem. (U.S.S.R.), 1956, 26, 343.294 E. &I. Larsen and LaV. E. Trevorrow, J . Inovg.Nucleav Chem., 1966, 2, 254.295 A. N. Nesmeyanov, R. Kh. Freidlina, and E. M. Brainina, Bull. Acad. Sci.Sanderson and G. E. MacWood, ibid., pp. 314, 316.D. Altman, 11. Farber, and D. M. Mason, ibid., p. 531.1, 536.U.S.S.R., 1954, 861.C. R. Simmons and R. S. Hansen, J . Phys. Chem., 1955, 59, 1072114 INORGANIC CHEMISTRY.lzeopen tyl derivatives. In benzene solution they have molecular com-plexities 6-44, 6.20, and 4.01 respectively ; none will volatilise in a vacuum.285Secondary alkoxides Th(0CHEt-R),, where R = Me or Et, are also non-volatile, and polymeric in benzene.286A mono- and a tri-hydrate of zirconium tetrafluoride have been identifiedby X-ray diffraction. The monohydrate is formed at 100" from the tri-hydrate, and hydrolysis to zirconyl fluoride and zirconium oxide occurs at250°.297 An X-ray investigation of the thorium-silicon system shows theexistence of p-ThSi, (in addition to the known a-ThSi2), ThSi, and Th3Si2.All are unstable in air.298The Vanadium Group.-Dipyridyl complexes of vanadium in the oxid-ation states +1, 0, and -1 have been isolated. When the salt [V11dipy3]12is reduced with magnesium or zinc in aqueous alcohol, the neutral complexpodipy3] is formed ; it gives blue solutions not having appreciable electricalconductivity.299 Oxidation with one equivalent of iodine gives a red-violetsolution containifig the ion [Vrdipy3]-'-, and reduction of a [Vodipy,] solutionin tetrahydrofuran (THF) containing a lithium salt gives black crystals offormula Li[V-Idipy3],4THF.Representation of this as a V-1 compound issupported by its diarnagneti~m.~W The valency of vanadium in its ternarynitrides differs from that in the binary nitride VN (as with titanium, whichgives TIN, but Li,TiN,). When the compounds Li,N and VN are heatedtogether, nitrogen is evolved leaving a product of approximate compositionLi,VN,, the chemical properties of which indicate the presence of vana-dium(v) .301Spectrophotometric and potentiometric studies in perchlorate media at25" indicate that the orange-yellow vanadium(v) species present in acidsolution are relatively few. In the pH range 0.5-1.3, the cation VO,+(aq.)is the only species. In the pH range 1-3-66 the isopolyvanadate ions areH,Vlo0284-(aq.), HVlo02,5-(aq.), and Vlo02,6-(aq.), -in proportions whichdepend on pHO3O2 Niobium pentoxide dissolves (4 g./lOO ml.) in concentratedhydrochloric acid and chloro-complexes are formed.In solutions in whichhydrogen- and chloride-ion concentrations were varied, the three speciesNb(OH),Cl,-, Nb(OH)Cl,+, and Nb(OH),Cl, were identified.303 The degreeof condensation of the isopolytantalate ion has been re-examined. Diffusioncoefficients, cryoscopy, and conductivity measurements indicate that inalkaline solution the only ion present is [Ta5016-j7-(aq.), which undergoes nochange throughout the alkaline pH range. The ion is formulated from theorthotantalate ion TaO,,-, the four oxygen atoms being replaced by TaO,groups.304297 R. VCT. M. D'Eye, J. P. Burden, and E. A. Harper, J .Inorg. Nuclear Chem., 1956,2, 192.29* E. L. Jacobson, R. D. Freeman, A. G. Tharp. and A. W. Searcy, J . Amer. Chem.Soc., 1956, 78, 4850.299 S. Herzog, Naturwiss., 1956, 43, 35.300 S. Herzog and R. Taube, ibid., p. 349.301 I<. Juza and W. Gieren. ibid., p. 225.~2 I;. J. C. Rossotti and H. Rossotti, Acta Chem. Scmd., 1956, 10, 957.303 J . H. Kanzelmeyer, J. Ryan, and H. Freund, J. Amer. Chem. Soc., 1966, 78,3020 ; see also D. I. Kurbatov and N. V. Demenev, Zhur. priklad. Khim., 1966,29,944.30* G. Jander and D. Ertel, J . Inorg. Nuclear Chem., 1956, 3, 139; see also V. I.Spitsyn and N. N. Shavrova, Zhur. obshchei Khim., 1956, 26, 1268ADDlSOK AND GREENWOOD THE TRANSITION ELEMENTS. 115'I'hermal and X-ray analysis of t,he system K20-V20, shows clear evidencefor the five compounds K,0,4V20,, K20,V205, 16K20,9V205, 2K,0,V205 and3K20,V2O5, but reveals no evidence for the existence of the previouslyreported allotropic modifications of vanadium pent~xide.~, The K20-T+0,system shows four compounds K20,5T%05, K20,2Ta205, K,O,Ta,O,, and3K20,Ta,05.Tantalum pentoxide is dimorphic.306Niobium trifluoride has now been prepared by the action of an HF-H,mixture on niobium hydride (NbH,.,) at 570". It is dark-blue and can besublimed in a vacuum.3o7 The oxyfluorides Nb0,F and Ta0,F both havethe Re03 structure, with fluorine and oxygen atoms randomly distributed inoctahedral positions about the metal atom .m8 Tantalum pentaiodide canbe prepared by heating the pentoxide with the stoicheiometric quantity ofaluminium iodide for 24 hr.at 230". A similar reaction with niobiumpentoxide probably gives the pentaiodide as initial product, but only thetri-iodide is i s ~ l a b l e . ~ ~ ~The alkoxides of the vanadium-group elements differ markedly fromthose of the titanium group. The alkoxides Nb(OR), (R = Et, Pr", Run, orn-pentyl) are yellow liquids, and the methoxide is a white crystalline solidof m. p. 60". The methoxides and ethoxides of tantalum are more volatilethan those of niobium, but the reverse becomes the case for the higher~ t - a l k o ~ i d e s . ~ ~ ~ All these ?z-alkoxides are dimeric in benzene, with sexaco-ordinate niobium and tantalum atoms in the molecule. A number ofisomeric butoxides and pentyloxides of niobium have been compared ; 311there is a general increase in volatility with increased branching of the chain.In contrast to tantalum, which forms stable tertiary alkoxides,312 niobiumgives no penta-tert.-alkoxides.Its greater tendency to give oxy-complexesis shown in the formation of oxide-tert.-butoxides of the type Nb,O(OBut),and NbO(OBut),. The molecular complexity of the tantalum alkoxidesTa(OR), is influenced by the donor properties of the solvent. When R = Me,Et, Prn, or Bun the compounds are dimeric in benzene but monomeric in~ y r i d i n e . ~ ~ ~The critical potential for electrodeposition of protactinium from 10-1l~-solutions of the fluoride is -1.20 v in relation to the hydrogen electrode.The normal potential of the Pa-PaF,2- couple is near 1.0 v.Conditions foroptimum deposition on nickel, gold, and platinum cathodes, and on a leaddioxide anode, have been defined.,l*The Chromium Group and Transuranium Elements.-Nitrosyl reineckate,[Cr(NCS),(NCS*NO) (NH3)2], h'as the constitution shown and is not a305 F. Holtzberg, A. Reisman, M. Berry, and M. Berkenblit, J . Amer. Chem. Soc.,1956, 78, 1536; see also V. V. Illarionov, R. P. Ozerov, and Y . V. Kil'disheva, Zhur.ncorg. Khim., 1956, 1, 775.306 A. Reisman, F. Holtzberg, M. Berkenblit, and M. Berry, ibid., p. 4514.307 P. Ehrlich, F. Ploger, and G. Pietzka, 2. anorg. Chem., 1956, 282, 19.308 L. K. Frevel and H. W. Rinn, Acta Cryst.. 1956, 9, 626.309 M. Chaigneau, Compt. relad., 1956, 242, 263.310 I). C. Bradley, B. N. Chakravarti, and W.Wardlaw, J., 1956, 2381.311 Idem, ibid., p. 4439.312 D. C. Bradley, W. ?Yardlaw, and A. Whitley, ibid., p. 1139.313 Idem, ibid., p. 5 .314 C. Ferradini, J . Chin&. Phys., 1956,53, 714; C. Ferradini and M. Haissinsky, ibid.,p. 722116 INORGANIC CHEMISTRY.nitrosonium salt. On being warmed, its soJutions decompose to give binuclearcomplexes :- 2NO2[Cr(NCS),(NCS*N0)(NH8)J ___t [Cr(NH3),(NCS),NCSaSCN(NCS),(NH,),Cr]- (SCNIo - rCr(NHd2(NCS)31,The complexes are linked through sulphur atoms.315 The oxidation ofchromous perchlorate solutions by molecular oxygen involves primaryformation of oxygen-bridged chromic c0mplcxes.~~6Red magnesium peroxychromate, Mg,(CrO,),, 13H,O, and various doublesalts of calcium, strontium, and barium peroxychromates with alkali metalperoxychromates, e.g., Ca5K2(Cr,0,,),,19H,0 and Ca2K2(Cr20,,),7H2O havebeen described.317 The acid H,[Mo,07*0,] has been recognised in concen-trated perchloric acid solutions of molybdenum(v1) containing hydrogenperoxide.'' Perniolybdic acid " is regarded as a salt of this acid with thecation [HM0206]', which itself is not p e r ~ x i d i c . ~ ~ ~New phosphates of sexavaleiit molybdenum have been prepared bycrystallisation from solutions of molybdenum trioxide in glacial phosphoricacid. From mixtures heated at 600", crystals of composition MoO,,P2O5 ( A )and ZMoO,,P,O, (13) are obtained. From mixtures heated at NO",2Mo0,,P20,,3H,0 (C) crystallises ; (C) is inolybdenyl hydrogen phosphate(Mo02)HP0,,H20 which at 300" gives the pyrophosphate (MoO,),P,O, (23) ;( A ) is probably molybdenyl polymetaphosphate ( M O O , ) ~ + ( P O ~ - ) ~ .~ ~ ~ Froma melt of MOO, and Graham's salt (polymeric NaPO,), the compoundNa,0,2Mo03,P205, which is probably inolybdenyl sodium orthophosphate(MoO,)NaPO,, crystallises.320 Analogous tungsten compounds are formed.Unusual heteropoly-anions have been described which contain both cobaltand tungsten in the anion :oxidation H+[co~~co~Iw,zo4Js- ____) [co~~co~'Iwl,o,2]'- ----+ [COIII( W20,)J9-The first two polyanions consist of a CoII ion enclosed in a basket of twelveWO, octahedra ; the other CoT1 ion (which is less readily oxidised but readilyremoved by acid) is in a COO, octahedron outside the basket but attachedby sharing corners with WO,Ternary oxides of quadrivalent molybdenum of formula hI,Mo,O,,(M = Mg2+, Zn2', Co2+, Fe2+) are formed when appropriate oxide mixturesare heated at 1150".322 Thermogravimetric and X-ray analysis of the manystages involved in the reduction of tungsten ti-ioxide by hydrogen have beendescribed.323 The crystal chemistry of oxygen compounds of molybdenum315 F.Seel, A. Hauser, and D. Wesemann, 2. afioi'g. Chem., 1956, 283, 351.316 M. Ardon and G. Stein, J., 1956, 2095.317 J. Beltran Martinez and M. Roca Adell, Publ. Inst. Quim. Aloizso Barba, 1955,316 F. Chauveau, P. Souchay, and G. Tridot, Bull. SOC. chim. France, 1955, 1519.319 I. Schulz, 2. anorg. Chem., 1955, 281, 99.320 Idem, ibid., 1956, 284, 31.321 L. C .W. Balier and T. P. McCutcheon, J . Anzer. Chem. SOC., 1966, 78, 4503.322 R. W. Schmid and C. N. Reilley, ibid., p. 2909.323 A. J. Hegediis, T. Millner, J. Neugebauer, and K. SasvBri, 2. anorg. Chew., 1955,9, 1, 15.281, 64ADI)ISOX AND GREENWOOD : THE TRANSITION ELEMENTS. 117and tungsten having structural elements of ReO, or perovskite type hasbeen reviewed.324 When water vapour-nitrogen mixtures are passed overtungsten trioxide at lOOO", the solid removed is a linear function of the watervapour pressure ; \VO,(OH), is the volatile species.325Complex fluorides of general formula M,[MoF,] and M2DVF,] are formedby condensing molybdenum or tungsten hexafluoride on solid alkali metalfluorides (M = K, Rb, Cs). The complexesare decomposed by bromine trifluoride yielding tetrafl~orobromites.~~~Molybdenum hexafluoride can be handled in normal glass vacuum apparatusif sodium fluoride is used to remove traces of hydrogen Thethermodynamic propertes of the system Moo3-HC1 can be accounted for onthe assumption that gaseous molybdenum oxychloride, MoO,Cl,, is formedwith traces of water present.328 When chlorotungstates [WC1,]G-z arereduced by tin in hydrochloric acid, the equilibrium in solution is representedby 3W,C1,3- + C1- + 2vI',c1145-, and the compounds K,W,Cl, andK,W,Cl,, can be crystallised.The latter, a dark green solid, gives deep-redsolutions in water.329 The former, on refluxing with aniline or pyridine, givesthe non-electrolytes W,C16,(C,H5*NH,), and W,C16,(C5H5N), which have thesame spatial distribution as the parent W,C1,3- ion, i.e., two fused octahedrawith a common triangular face of chlorine ~oIIs.~~O Treatment of eitherpotassium salt with bromine vapour at 450" yields dark crystals of the mixedhalide W B r C1,.331The same uranium mixed halide UClF, is obtained by each of the re-actions UO,F,-CCl,, U0,F2-CCl,~CC1:CC12, UF4-UCl,, UF3-Cl,,and UF,-CCl,,and has been shown to be the product to which the formula UCl,F, waspreviously assigned.332 In perchlorate solution, complex formation takesplace between U0,2+ and F- ions, with the ion UO,F4,- as the upper limit.,,,More extensive information is available on the U03-H,0 system.At 180"an orthorhombic hydrate U03,0.8H,0 is stable; between 200" and 280" thephase UO,,l-OH,O appears, and the hemihydrate U0,,0.5H20 is stableabove 280".33p Solvent-extraction and spectrophotometric studies show thatenhanced extraction of uranyl nitrate into ketonic solvents in the presenceof a substituted ammonium nitrate is due to the formation of the ioniccomplex R+[UO,(NO,),]- (R = alkylammonium, alkylpyridini~m).~~~An important series of papers describe organic compounds ofuranium.sG* Twenty-seven uranium( ~ v ) dicarbonyl chelates324 A.MagnCli, J . Inorg. Nztclear Chesn., 1956, 2, 330.325 0. Glemser and H. G. Volz, Natztrwiss., 1956, 43, 33.326 B. Cox, D. W. -4. Sharp, and A. G. Sharpe, J . , 1956, 1242.327 T. A. O'Donnell, ibid., p. 4681.328 N. Hultgren and L. Brewer, J . Phys. Chem., 1956, 60, 947.329 R. A. Laudise and R.C . Young, J . Amer. Chem. SOC., 1955, 77, 5288.330 H. B. Jonassen, S. Cantor, and A. R. Tarsey, ibid., 1956, 78, 271.331 R. C. Young and R. A. Laudise, ihid., p. 4861.332 A. W. Savage, ihid., p. 2700.333 S. Ahrland, R. Larsson, and K. Rosengren, Acta Chem. Scand., 1956, 10, $05.334 J. K. Dawson, E. Wait, K. Alcock, and D. R. Chilton, J . , 1956, 3531.336 L. Kaplan, R. A. Hildebrandt, and M. Ader, J . Inorg. Nuclear Chem., 1956,2, 153.336 H. Gilman, R. G. Jones, E. Bindschadler, D. Blume, G. Karmas, G. A. Martin,J. F. Nobis, J. R. Thirtle, H. L. Yale, and F. A. Yoeinan, J . Amer. Chem. Soc., 1956, 78,2790.337 R. G. Jones, G. Karmas, and G. A. Martin, and H. Gilman, ibid., p. 4285; R. G.Sodium fluoride does not react118 INORGANIC CHEMISTRY.U(R*CO*CHCO*R1) , and fourteen uranyl compounds UO,( R*CO*CH*CO*R1),have been prepared.The former are mostly volatile but the latter are not.336Uranium diethylamide U(NEt,), is a green volatile compound, m. p. 35.5";attempts to prepare other UIv dialkylamides were unsuccessful. From thediethylamide, reaction with thiols gives Urn ethyl and n-butyl mercaptidesU(SR), as light green pyrophoric solids. The methoxide and ethoxideU(OR), are readily decomposed by moisture. A number of uranium(v)alkoxides U(OR), have also been isolated ; the ethoxide U(OEt), is thermallystable and readily distilled.%,The recent chemistry of the transuranium elements has been reviewedby H. J. Emelkus and A. G . Maddock.338 Plutonium nitrate separates asthe pentahydrate Pu(N0,),,5H20 on slow crystallisation from a concentratedsolution in nitric acid.The dilute aqueous solution is brown, changingrapidly to green as colloidal plutonium is formed.339 Plutonium nitride,PUN, is prepared from the metal and nitrogen above 230". Unlike uraniumnitride, it is completely hydrolysed in moist air in a few hours at 80-90°.340Examination of the plutonium-hydrogen system shows that in the rangePuH,-PuH2.,, hydrogen is in solid solution in the fluorite structure ofPuH,. Between PuH,,, and PuH, a hexagonal hydride phase appears.341Fuller information is now published on the preparation and properties ofplutonium hexafluoride. It may be formed in the following ways :(1) 2Pu0, + 12HF + 0, __t 2PuF, + 6H,O; (2) 2PuF, + 0, +PuF, + PuO,F,; (3) PuF, + F, _t PuF, (AmF, is not produced underthese conditions) ; (4) 2PuF3 + 3F, + 2PuF, ; and (5) Pu0, + 3F, +PuF, + 0,.The hexafluoride is a white crystalline solid, melting at 50.7"to a brown liquid. Low-temperature hydrolysis with traces of moisture givesthe oxyfluoride PuO,F,, but hydrolysis by water at room temperature is vio-lent, giving PuO, and P u F , . ~ ~ The small magnetic susceptibility of the PuF,molecule has been considered in terms of its two non-bonding electrons.343Purv in hydrochloric acid forms the complex ion P U C ~ ~ + . ~ Since separationof tervalent plutonium, americium, and curium occurs on ion-exchangecolumns in chloride solutions, chloride complex-formation has been studiedas a function of hydrochloric acid concentration.Dissociation constants ofthe monochloride complexes MC12+ are identical in dilute acid, but in strongacid the complexing powers (MC1,-) are in the order Pu >Am > Cm.The results are of interest with reference to 5f orbital h y d r i d i s a t i ~ n . ~ ~ ~Conditions have been given for quantitative deposition of ,,lArn onsteel, platinum, or copper electrodes.a6 The 248-isotope of berkeliumJones, E. Bindschadler, G. Karmas, F. A. Yoeman, and H . Gilman, J . Anzer. Chem.SOC., 1956, 78, 4287; R. G. Jones, E. Bindschadler, G. Karmas, G. A. Martin, J. R.Thirtle, F. A. Yoeman, and H. Gilman, ibid., p. 4289.338 H. J. Emel6us and A. G. Maddock, Osterr. Chem.-Ztg., 1956, 57, 153.339 J. L. Drummond and G. A.Welch, J., 1956, 2565.340 F. Brown, H. M. Ockenden, and G. A. Welch, J . , 1955, 4196.341 R. N. R. Mulford and G. E. Sturdy, J . Amer. Chem. Soc., 1956, 78, 3897.342 C. J. Mandleberg, H. K. Rae, R. Hurst, G. Long, D. Davies, and K. E. Francis,J . Inorg. Nuclear Chem., 1956, 2, 358. 368; B. Weinstock and J. G. Malm, ibid., p. 380.843 D. M. Gruen, J. G. Malm, and B. Weinstock, J . Chem. Phys., 1956, 24, 905.344 S. W. Rabideau and H. D. Cowan, J . Amer. Chem. SOC., 1955, 71, 6145.346 M. Ward and G. A. Welch, J . Inorg. Nuclear Chem., 1956, 2, 395.346 R . KO, Nucleonics, 1956, 14, No. 7, 74ADDISON AND GREENWOOD : THE TRANSITION ELEMENTS. 119(half-life 23 & 5 hr.) is formed by 25 Mev-helium-ion bombardment of24QCm ; the berkelium fraction is separated from curium, californium, andfission products by precipitation and ion e~change.3~7 The half-life of245Bk is 5 daysu8 Some nuclides were found in the debris from the 1952thermonuclear test which have not been detected in reactor irradiationproducts. These include 24eCm and 2aCf (spontaneous fission half-life< 1.2 x lo7 yr., and 55 days).a9 Neutron irradiation of plutonium hasyielded isotopes of einsteinium * (253E, 254E, 255E) and fermium * (2aFm,255Fm).350 The decay of 252Fm has been studied.351The Manganese Group.-Manganese shows univalency in its isocyanidecomplexes.Each product of the reaction2Mn12 + I2RNC [Mn(RNC),]I 4- [Mn(RNC)J2contains univalent manganese, and is diamagnetic. The monoiodide is con-verted into the tri-iodide by iodine.Complex isocyanides [Mn(RNC),]Xhave been isolated in which R = MeO*C,H,*NC, Me*C,H,*NC, C,H,-NC,$-C1*C6H4*NC and X = C103-, Cl-, Br-, OH-, PF,-, HCO,-, BF,- andBPh4-.353 The reactivity of the oxyanions MnO,-, Mn0,2-, and MnOd3-has been compared in terms of the free-energy changes involved.353Values for the electrode potentials between different valency states oftechnetium have been revised.3a Radioactive technetium almost certainlyexists in terrestrial substances in minute quantities (e.g., in uranium ores byspontaneous fission of 238U), but the search for primordial technetium hasbeen unsuccessful: The possibility of discovering primordial technetiumdepends on whether the 9 8 T ~ half-life exceeds lo8 years, and there is evidencethat it is near lo5 years.Technetium is believed not to exist in the sun.355Rhenium of high purity (> 99.95%) has been prepared by hydrolysis ofthe pentachloride, and hydrogen reduction of the hydrated rhenium dioxideso formed.356 The yellow solution obtained on reduction of the trichlorideRe,Cl, in sodium cyanide solution with sodium amalgam represents quantita-tive reduction to rhenium(1) cyanide. Potentiometric measurements indicatethat oxidation of this solution by ferricyanide proceeds in two distinct stepsRe1 + Rem and ReITr + ReV.357 Fluororhenic acid H2ReF, cannot be347 E. K. Hulet, Phys. Rev., 1956, 102, 182.348 L. B. Magnusson, A. M. Friedman, D. Engelkemeir, P. R. Fields, and F. Wagner,ibid.. p. 1097.349 P. R. Fields, M.H. Studier, H. Diamond, J. F. Mech, M. G. Inghram, G. L. Pyle,C. M. Stevens, S. Fried, W. M. Manning, A. Ghiorso, S. G. Thompson, G. H. Higgins,and G. T. Seaborg, ibid., p. 180.260 M. Jones, R. P. Schuman, J. P. Butler, G. Cowper, T. A. Eastwood, and H. G.Jackson, ibid.. p. 203.351 A. M. Friedman, J. E. Gindler, R. F. Barnes, R. Sjoblom, and P. R. Fields, ibid.,p. 585.352 A. Sacco and L. Naldini, Gazzelta, 1956, 86, 20'7.353 A. Camngton and M. C. R. Symons, J., 1956, 3373.354 G. H. Cartledge and W. T. Smith, J . Phys. Chem., 1955, 59, 1111.355 F. Daniels, ibid., 1956, 60, 705.356 D. M. Rosenbaum, R. J. Runck, and I. E. Campbell, J . Electrochem. Soc.. 1966.5 5 7 J. Meier and W. D. Treadwell, Helv. Chim. Acta, 19.55, 38, 1679.* The names einsteinium and fermium (E and Fm) for elements of atomic number 99and 100 respectively have been used in the literature, but have not yet receivedapproval from I.U.P.A.C.103, 618120 INORGANIC CHEMISTRY.isolated as a solid by evaporation of its solutions since this results in decomposi-tion to rhenium dioxide.However, many salts "a+, K+, Rb+, Cs+, NH4+,Ba2+, Ni(NH,),2+, CO(NH3)63+] containing the ReF,2- ion are now character-ised. Both the acid and its salts shows a surprising stability towards alkaliesand strongThe Iron Group.-A quadrivalent iron compound is produced by nitric acidoxidation of the complex [FeCl,(diarsine),J [FeCl,] (where diarsine = o-phenylenebisdimethylarsine). I t has the formula [FerVC12(diarsine)J [FeCl,],and a magnetic moment indicating two unpaired electrons as requiredfor FeIV with six d2sp3 bonds.In titration with iodide ions, one equi-valent of iodine is liberated.359 Iron pentacarbonyl is decomposed by nitro-gen sulphide, N,S,, in benzene solution to give a black solid Fe(NS),, andthe magnetic moment again indicates two unpaired electrons.360 The pre-paration of a range of ferrates(vI), orthoferrates(Iv), and metaferrates(1v)of alkali and alkaline-earth metals has been described.361 A new deca-hydrate FeCl,, 10H20, melting incongruently at O", has been recognisedduring phase study of the FeC1,-H20 system.362A series of nitratoaquo-nitrosylruthenium complexes, of general formula[RuNO(NO,),(OH), -g(H20)2] have been identified which further illustratethe pronounced stability of the RuN03+ complex.In aqueous solution theygive rise to both anionic and cationic ruthenium species. The trinitrato-complex [RuN0(NO3),(H2O),] is formed by the action of boiling 8x-nitricacid on nitrosylruthenium and its proton dissociation andhydrolysis has been examined.364 Hydrogen peroxide reduces rutheniumtetroxide in nitric acid to give a deep red solution containing a series ofhydroxyaquo-complexes of general formula [Ru(OH),(H,O), -J(NO,), --2.No evidence was found for the parent compound [RU(H20)6](N03)4,365Potassium fluororuthenate(II1) K,RuF, is prepared by fusing an hydrouspotassium hydrogen fluoride at 250" with ruthenium tri-iodide. Unlessoxygen is rigidly excluded, K,RuF, is formed also.366Some unusual ethylenediamine complexes of osmium ( ~ v ) have beendescribed. Ammonium hexabromo-osmate( ~ v ) , (NH,),[OsBr,], reacts exo-thermally with anhydrous ethylenediamine giving the pink sexacovalent 0sIvcomplex [Os en (en-H),I2+ (BI--)~ [(en-H) represents a molecule of ethylenedi-amine less one proton].This is readily reduced to [Os en,(en-H)]3+(Br-)3,maintaining the 0sIv valency state, and an additional molecule ofethylenediamine can be added to yield the %covalent OsIV complex[Os en2(en-H)2]Br2.365 From the Raman and infrared spectrum of liquid3 6 8 R. D. Peacock, J . , 1956, 1291; E. Weise, 2. anorg. Chem., 1956, 283, 377.359 R. S. Nyholm and R. V. Parish, Chem. and Ind., 1956, 470.360 M. Goehring and K.-W. Daum, 2. anorg. Chem., 1956, 282, 83.361 W.F. Linke, J. Phys. Chem., 1956, 60, 91.362 R. Scholder, F. Kindervater, and W. Zeiss, 2. anorg. Chem., 1056, 283, 338;363 J. M. Fletcher, I. L. Jenkins, F. M. Lever, F. S. Martin, A. R. Powell, and R.364 I. L. Jenkins and A. G. Wain, ibid., 1956, 3, 28.s65 J. S. Anderson and J . D. M. McConnell, ibid., 1955, 1, 371.366 R. D. Peacock, Chem. and Ind., 1956, 1391.367 F. P. Dwyer and J. W. Hogarth, J . Amer. Chem. SOC., 1965, 77, 6152.R. Scholder, H. von Bunsen, F. Kindervater, and W. Zeiss, ibid., 1956, 282, 268.Todd, J . Inorg. Nuclear Chem., 1955, 1, 378ADDISON AND GREENWOOD : THE TRANSITION ELEMENTS. 121osmium tetroxide it is deduced that the molecule is regular tetrahedral.Since the Raman spectra of the Re0,- and WO,,- ions are closely similar,it is concluded that these ions are also tetrahedral, and not octahedralowing to co-ordination of water molecules as previously supposed.368The Cobalt Group.-X-Ray analysis of bis-(NN-dimethy1dithiocarbamato)-nitrosylcobalt(II), [Co(S,CNMeJ,(NO)], has shown this molecule to be anexample of square pyramidal configuration in a quinqueco-ordinate complex.The cobalt atom lies 0-5 A above the plane of the four sulphur atoms (24);in this structure the lines join bonded atomsThe NO group is inclined at an angle of 135"tothe vertical axis of the pyramid, and itsbonding is therefore unusual. It may well Me2N/c\s/ \s /iiNMezbe a r-complex in which the N and 0 atomsare arranged unsymmetrically because of thedifference in their electronegativitie~.~~~ The quadrico-ordinate complex[CO~~CI,, (CH3*c6H4*NH2),] has been shown crystallographically to be planar,370and the infrared spectrum of the complex HIColIIC1,, (dimethylglyoxime),],when normal and deuterated dimethylglyoxime are used, justifies the assump-tion that -0-H-O-bonds are present in the dimethylglyoxime plane.371Outer-sphere association of the cobaltammine ions [CO(NH,),]~+ and[CO(NH,),,H,O]~+ with sulphate ions in solution, which is responsible forimmediate changes in the absorption spectrum, has been studied quanti-tatively and equilibrium constants evaluated.372 The compounds Co30, andZnCo,O, have spinel structures, and the very low paramagnetic suscepti-bility indicates that Co3+ ions are situated in octahedral interstices andcovalently bonded as in other CoIII c0mplexes.~7~The interaction of bromine trifluoride and sodium hexachlororhodate(II1)has been rein~estigated.~,~ The product, identified from its predictedX-ray powder pattern, is the complex Na,RhF6, and not Na3RhF, asoriginally thought.Some sexico-ordinate sulphitoammine complexes ofrhodium and iridium have been described in which the SO3,- ion acts as amono- or a bi-dentate ligand.374The chemistry of iridium fluorides has been re-examined and extended.Iridium hexafluoride (m. p. 44", b. p. 53") gives a deep yellow vapour stableto red heat. Its magnetic moment (3.3 B.M.) is consistent with octahedralconfiguration. When kept in glass rigorously dried, there is no evidence ofthe oxyfluoride IrOF,, thought to be formed by reaction with glass.In itsreactions, reduction to IrV frequently occurs ; thus sulphur tetrafluoride andsulphur dioxide give IrF,,SF, (which may have the ionic form SF3+JrF,-)and IrF,,SO,. Nitric oxide and gaseous dinitrogen tetroxide give thewithout indicating the bond multiplicity. NOI/s -cO - s\ass L. A. Woodward and H. L. Roberts, Trans. Faraday SOC., 1956, 52, 615.368 P. R. H. Alderman and P. G. Owston, Nature, 1956, 178, 1071.370 G. B. Bokii, T. I. Malinovskii, and A. V. Ablov, Kristallografiya, 1956, 1, 49.371 A. Nakahara, J . Fujita, and R. Tsuchida, Bull. Chem. SOC. Japan, 1956, 29, 296.s73 P. Cossee, Rec. Tvav. chim., 1956, 75, 1089.874 V. V. Lebedinskii and 2. M. Novozhenyuk, Izvest.Sekt. PZuatiny, 1955, No. 29,F. A. Posey and H. Taube, J . Amev. Chem. SOC., 1956, 78, 15.66; V. V. Lebedinslrii and Ye. V. Shenderetskaya, ibid., 1955, No. 30, 99122 INOHGANIC CHEMISTRY.nitrosonium and nitronium compounds (NO),IrF, and (NO,),IrF, ; each losesan atom of fluorine on being heated. As with osmium, no simple pentafluorideof iridium has been found. Above ZOO", iridium hexafluoride attacks glassto give the tetrafluoride (m. p. 1 0 6 O ) , which is reduced to the trifluoride byheating in an atmosphere of sulphur tetrafl~oride.,'~The Nickel Group.-In solutions 2-3 molar in alkali-metal chlorate orchloride, electrolytic reduction of Nirl to NiI is the principal process.376The small magnetic moment of the complex fluoride KNiF, has been shownto be due to antiferromagnetism; complexes of the type KMIIF, (M = Mn,Fe, Co, Ni, Cu, Zn) all have perovskite structures and are antiferr~magnetic.~~~Magnetic properties of the complexes Ni(PEt,),X, are consistent with thesquare planar structure when X = C1-, Br-, or I-, and the tetrahedralstructure when X = X-Ray investigation of bisacetylacetone-nickel(r1) shows it to be the trinuclear Ni3(C,H,0,)G with nickel atoms almostc01linea.r.~~~ The infrared spectrum of the [Ni,(cN),l4- ion shows absorptionin the C=N region only.Bridging does not therefore occur by C=N groups,and the nature of this bridging is not so well understood as was thought.It may involve bridging C-N groups using three-centre molecular orbitals.380Exchange of [14C]ethylenediamine with the [Ni enJ2+ ion occurs at a measur-able rate, whereas exchange with [Zn en,]", [Cu en2I2+, and [Hg en,]2t isimmeasurably fast .381The complexes [Pd(diarsine),X,] formed by Pdl[ salts with o-phenylene-bisdimethylarsine present an interesting range of co-ordination numbers.The colourless diperchlorate is the 4-co-ordinated [Pd(diarsine),] (C104),.When X = C1, Br, I, CNS, and NO, highly coloured compounds are obtainedwhich behave as uni-univalent electrolytes in nitrobenzene, and are 5-co-ordinated complexes of the type [Pd(diarsine),X]X.In the solid state,[Pd(diarsine),I,] has a distorted octahedral structure.382 Methods used toprepare isocyanonickel, Ni(RNC),, give diisocyanopalladiuin(0) compoundsPd(RNC), (R = phenyl, 9-tolyl, 9-anisyl) which are not analogous and areprobably polymeric.383 Bridged complexes of palladium containing thiol(e.g., alkylthiobenzoic acid) bridge groups are less reactive (i.e., the bridgingis stronger) than halogen-bridged complexes.384 Successive equilibriumconstants for replacement of rt-octylamine in the complex [PdC1,,(C8H,,NH,)Jby tributylphosphine, by use of trimethylpentane as solvent, have beenevaluated.The system is characteristic of those found useful for studyingequilibrium in water-insoluble complexes.385 The hydroxide Pd(OH),obtained by hydrolysis of sodium palladate(I1) differs from the product375 P. L. Robinson and G. J. Westland, J., 1956, 4481.376 R. H. Sanborn and E. F. Orlemann, J. Amer. Chem. Soc., 1956, 78, 4852.377 R.L. Martin, R. S. Nyholm, and N. C. Stephenson, Chem. and Ind., 1956, 83;378 R. W. Asmussen, A. Jensen, and H. Soling, Acfa Chern. Sca?zd., 1955, 9, 1391.379 G. J. Bullen, Nature, 1956, 177, 537.380 M. F. A. ElSayed and R. K. Sheline, J . Amer. Chenz. SOC., 1956, 78, 702.381 D. S. Popplewell and R. G. Wilkins, J . , 1955, 4098.382 C. M. Harris and R. S. Nyholm, J., 1956, 4375.383 L. Malatesta, Rec. Trav. chim., 1966, 75, 644.384 S. E. Livingstone, J . , 1956, 1989.3 8 5 €3. Rileddings and A . R . Bnrkin, ibid., p . 1116.see also R. W. Asmussen and H. Soling, 2. anorg. Chem., 1956, 283, 3A1)L)ISON AND GREENW001) : THE TRANSITION ELEMENTS. 123PdO,H,O resulting from the action of heat on acid palladium nitrate solution.The latter contains molecules of water within the Pd-0 lattice.366Palladium and platinum form tetrathionitrosyl compounds analogousto those of iron, cobalt, and nickel.Palladium dichloride reacts withnitrogen sulphide (N4S4) in methyl alcohol to give red-brown crystalsof Pd(NS),, m. p. 165". The platinum compound Pt(NS), (m. p. 144")is formed from chloroplatinic acid and nitrogen sulphide in hot dimethyl-formamide. Both are soluble in organic solvents but insoluble in water.387An X-ray examination of sesquiethylenediaminetrimethylplatinic iodide,Pt(CH3),J,1*5en, shows that the molecule is a dimer, the two mononuclearcomplexes being linked through a single ethylenediamine molecule, i.e.,[(CH,), en Pt-en-Pt en (CH,),]2f.388 The equilibrium between cis- andtrans-forms of (MR,),PtX, (where M = P, As, Sb, and X =halogen) inbenzene solution has been studied.The equilibrium shifts towards thetram-form when chlorine is replaced by iodine, and as the homologousseries is ascended from R = Me to Prn.389 A detailed infrared spectroscopicinvestigation of absorption due to N-H stretching modes of vibration hasbeen made, with particular reference to amine complexes of platinous~hloride.~w Development of the use of infrared spectra to determine whetherthiocyanato-groups are in bridge or terminal positions in complexes has madeit possible to re-examine the two known isomers of the compound(PPr,n),Pt,C1,(SCN),. Both isomers are now found to have SCN groups inbridging positions, so that geometric isomerism is involved, with -CN groupscis or trans to each other about the planar PtS,Pt ring.391 The course of thethermal dissociation of platinic chloride and bromide has been described.392The Copper Group.-The remarkably small distance between the twocopper atoms (2.64 A) in binuclear cupric acetate Cu,(CH,*C0,),,2H20 hasstimulated further work on the metal-metal bonding involved.The temper-ature variation of magnetic susceptibility of this and the anhydrous salthas been measured, and it is suggested that Cu-Cu bonding occurs bylateral overlap of 3dz~-yt orbitals.393 A detailed study has been made of anti-ferromagnetic resonance in hydrated cupric chloride CUC~,,~H,O.~~~ The in-frared spectrum of the ethylenediaminetetra-acetato- (edta) and diaspartato-(asp) copper complexes K,[Cu edta] and K,[Cu(asp),] indicates that allnitrogen atoms and carboxyl groups are co-ordinated to the metal, which isthus sexaco-ordinate. This is consistent with the optical activity of theformer.395 For comparison with CuCr204, the ternary chalcogenidesCuV,S,, CuCr,S,, CuCr,Se,, and CuCr,Te,, have been prepared by heating3*6 0.Glemser and G. Peuschel, 2. anorg. Chem., 1955, 281, 44.s87 E. Fluck, M. Goehring, and J. Weiss, ibid., 1956, 287, 51.388 M. R. Truter and E. G. Cox, J., 1956, 948.389 J. Chatt and R. G. Wilkins, ibid., p. 525.3g0 J. Chatt, 1;. A.. Duncanson, and L. M. Venanzi, ibid., p. 2712.391 J. Chatt and L. A. Duncanson, Nature, 1956, 178, 997.39* S. A. Shchukarev, T. A. Tolmacheva, M. A. Oranskaya, and L.V. Komandrov-skaya, Zhwv. neorg. Khim., 1956, 1, 8 ; S. A. Shchukarev, M. A. Oranskaya, and T. S.Shemyakina, ibid., p. 17.398 B. N. Figgis and R. L. Martin, I., 1956, 3837.sg4 H. J. Gerritsen,.M. Garber, and G. W. J. Drewes, Physica, 1966, 22, 213, andrefs. therein.395 S. Kirschner, , J . Anzer. Cheau. SOC., 1956, 78, 2372124 INORGANIC CHEMISTRY.the binary chalcogenides in equivalent quantities at 600-800". All crystal-lise in a normal spinel lattice.396Like the fluoroborate, silver hexafluoro-phosphate, -arsenate, -antimon-ate, -niobate, and -tantalate are soluble in benzene, toluene, and m-xylene.Evaporation of the solution gives addition complexes with the aromatichydrocarbons (e.g., AgPF,,C,H,). Copper displaces silver from the abovesilver salts in toluene, forming corresponding cuprous cornpo~nds.~97 Equi-librium constants for complex formation between the aqueous Ag+ ion andcyclic olefins indicate that the reactivity of the olefin as an electron donorin x-complex formation is a function of ring strain ; the constants are in theorder cydopentene > cycloheptene > cyclohe~ene.~~~ The silver perchlorate-dioxan compound AgC1O4,3C,H,O2 has an interesting structure.Silveratoms at the corners of a cube are surrounded by an octahedron of dioxanoxygen atoms, and the dioxan molecules rotate without hindrance.399Sulphimide silver hydrate AgNS02,H,0 exists as a trimer, and X-rayanalysis has revealed that the basic unit in the structure is a &memberedring of alternate N and S atoms.400In strongly alkaline solution, silver and argentocyanide ions react togive hydroxy-anions [Ag(OH) (CN)]-.401 The ion Ag(IO,),- has beenrecognised in solution by measurement of the solubility of silver iodate inlithium iodate solutions, by use of radioassay techniq~es.~O~ Solubility andpotentiometric methods give evidence for the complex ions Ag132-, Ag143-,and the polynuclear speciesHowever,complex-formation with o-phenylenebisdimethylarsine gives [Au(diarsine),]I,with tetrahedral configuration. Tervalent gold gives the quadricovalentcomplex [Au(diarsine),13+, but in the presence of halide ions the 5- and 6-covalent complexes [Au(diarsine),XI2+ and [Au(diarsine),X,] + have beenidentified.404 The acid HAu(CN), has been prepared as colourless crystalsby passage of a solution of its potassium salt through the €€+-form of Dowex-50 resin, followed by rapid evaporation. It loses hydrocyanic acid rapidlyat 1200.405 X-Ray analysis of gold(1) iodide indicates that the solid consistsof endless zig-zag Au-I-Au-I chains.406The Zinc Group.-Potentiometric titration of the iodides of zinc, cadmium,and mercury with potassium in liquid ammonia showed only reduction tothe metal, and no evidence for the +I oxidation state under these condi-tions.407 The melting-point of anhydrous zinc chloride, for which widelyvarying values have been reported, is 318"; the anhydrous compound wasand Ag3185-.403The co-ordination number 4 for univalent gold is unusual.396 H. Hahn, C . de Lorent, and B. Harder, 2. anorg. Chern., 1956, 283, 138.397 D. W. A. Sharp and A. G. Sharpe, J.. 1956, 1855, 1858.398 J . G. Traynham and M. F. Sehnert, J . Amer. Chenz. SOC., 1956, 78, 4024.388 R. J. Prosen and K. N. Trueblood, Acta Cryst., 1956, 9, 741.400 K. Fischer and K. R. Andress, 2. anorg. Chem., 1955, 281, 169.401 I. M. Kolthoff and J . T. Stock, J . Amer. Chem. SOC., 1956, 78, 2081.402 J. J. Renier and D. S. Martin, zbid., p. 1833.403 I. Leden, Acta Chenz. Scand., 1956, 10, 540, 812.404 C. M. Harris, R. S. Nyholm, and N. A. Stephenson, Rec. Trav. chirn., 1956, 75,405 R. A. Penneman, E. Staritzky, and L. H. Jones, J . Amer. Chem. Soc., 1956,78, 62.408 A. Weiss and A. Weiss, 2. Naturforsch., 1956, llb, 604.407 G. Mr. Watt and P. S. Gentile, J , Amer. Chem. SOC., 1965, 77, 6462.687ADDISON AND GREENWOOD : THE TRANSITION ELEMENTS. 125obtained from zinc and hydrogen chloride, and by dehydration of thehydrated salt in a stream of hydrogen chl0ride.~08 The terpyridyl complex[(terpy)ZnCl,] shows an interesting case of quinquecovalency. The latticeis molecular, the Zn atom being linked in a distorted trigonal bipyramid tothree N and two C1 atoms. The cadmium and copper compounds have thesame ~tructure.~0~ Exchange of 36Cl between zinc, cadmium, and mercurychlorides and liquid nitrosyl chloride is rapid between absorbed nitrosylchloride and the metal halides, followed by a slow heterogeneous exchangewith excess of liquid. This favours the existence of unstable nitrosoniumsalts of the metal chloride complexes. No exchange occurs between nitrosylchloride and a stable nitrosonium salt (e.g., (NO),SnC16) or sodium or potas-sium chlorides.410Cadmium dialkyls CdR, (R = Me, Et, Pri) in liquid propane at < -120"react with hydrogen sulphide giving pure cadmium hydrogen sulphideCd(HS),. Above -40" this decomposes, evolving hydrogen ~ulphide.~llPure anhydrous cadmium chloride can be prepared by the action of chlorinegas on the molten metal, and sublimation of the Formationconstants for the complexes CdI+, CdI,, CdI,-, and CdI,2- have beenevaluated.413Crystallographic studies on mercurous salts give further informationon HgHg bond lengths. In Hg2(N0,),,2H,0 the HgHg distance is2.54 0.01 A, and the close approach of a water molecule to each Hgatom [d(Hg-0) = 2.15 A] suggests the presence of an oxonium ion(H2O*Hg*Hg*OH.J2+. The Hg-Hg distance in mercuroiis fluoride is 2.43 -J=0.04 A, which falls in line with known values 2.53, 2-58, and 2.69 A for thechloride, bromide, and iodide.414 Heptasulphur imide (S,NH) reacts withmercurous nitrate giving the yellow product S,N-Hg*Hg*NS,, which darkensin air and light. Tetrasulphur tetraimide (N4S4H,) yields [HgI(NS)]z.415The compound described in the literature as mercury amidofluoride, HgNH,Fhas been shown to have the constitution (Hg,N)F,NH,F ; when Millon's baseis treated with aqueous ammonium hydrogen difluoride, the compound separ-ates during 24 hr. as a yellow powder.416 A similar compound Hg,NHBr,has a layer lattice of [Hg,(NH),] units; Br- ions are in holes in the layersand HgBr3- groups between the layers.417 Molecules of a compound HgK,have been identified in the vapour of molten potassium amalgam.418C. C . ADDISON.N. N. GREENWOOD.408 D. A. Craw and J. L. Rogers, J., 1956, 217.409 D. E. C. Corbridge and E. G. Cox, ibid., p. 594.410 J. Lewis and D. B. Sowerby, ibid., p. 150.4 l 1 U. Hauschild and 0. GIemser, Naturwiss., 1955, 42, 624.d l 3 J. L. Barton, H. Bloom, and N. E. Richards, Chew. and Ind., 1956, 439.413 M. Quintin and S. Pelletier, Compt. rend., 1956, 242, 768.414 D. GrdeniC, J . , 1956, 1312; D. Grdenib and C. DjordejeviC, ibid., p. 1316.415 M. Goehring and G. Zirker, 2. anorg. Chem., 1956, 285, 70.416 K. Brodersen and W. Rudorff, ibid., 1956, 287, 24.417 K. Brodersen, Acta Cryst., 1955, 8, 723.4 l 8 A. Roeder and W. Morawietz, 2. Elektrochem., 1956, 60, 431