8 Chemistry of the d-and f-Block Metals By J. R. DILWORTH G. J. LEIGH and R. L. RICHARDS ARC Unit of Nitrogen Fixation University of Sussex Brighton BN 1 9QJ K. W. BAGWALL Department of Chemistry University of Manchester Manchester M13 9PL PART I The Transition Metals By J. R. Dilworth G. J. Leigh and R. L. Richards 1 Introduction This year we have again concentrated on a selection of topics which we have judged to be particularly active and interesting. Inevitably some topics which were dis- cussed last year are again included and in particular sulphur ligands receive more detailed coverage. 2 Macrocyclic Ligands Within this wide area we have chosen to discuss in some detail metal porphyrin complexes complexes of dinucleating ligands and the influence of ring size on the properties of complex compounds of macrocyclic ligands.Metal-Porphyrin Complexes.-These compounds merit considerable attention because of their relevance to natural species such as chlorophyll haemoglobin myoglobin catalase peroxidase and the cytochromes. We will not cover the dioxygen-carrier properties of porphyrin complexes in detail since it was discussed last year but rather will concentrate on their general chemical and structural features. Structural aspects of metal-porphyrin complexes have been reviewed this year,’ and a recent book gives a more general coverage of their chemistry.’ We have used the following abbreviations PH =general porphyrin; TPP(R)H2 = apy&tetraphenylporphyrin with substituent R on phenyl ring or rings; OEPH2 = octaethylporphyrin; PP(IX)(DME)H2= protoporphyrin(XX)(dimethyl ester); TNMPP(3- or 4-)H2= tetra(3- or 4-N methylpyridy1)porphyrin; TPrPH = tetra-n-propylporphyrin; DP(DME)H2 = deuteroporphyrin(dimethy1 ester).Less com-monly used porphyrins will be named in the text as appropriate. Titanium. The complexes [TiX2(TPP)] (X = F C1 or Br) prepared by treatment of [TiO(TPP)] with the gaseous halogen acids in dichlorom,:thane easily revert to ’ W. R. Scheidt Accounts Chem. Res. 1977 10 339. ‘The Porphyrins’ ed. K. M. Smith Elsevier Amsterdam 1975. 169 J. R. Dilworth G. J. Leigh R. L. Richards and K. W.Bagnall their oxide precursor on hydrolysis.3 Reduction of [TiF,(TPP)] at a rotating pla- tinum electrode in CH2C12-[Bu4N][PF6] gives a purple product formulated as [TiF(TPP)] which reacts readily with dioxygen to give a mixture of [Ti(O,)(TPP)] and [TiF2(TPP)].3 The series [TiO(TPPR)] (R=C1 OMe Me NEt, CF3 Pr’ or OH as para-substituent of one TPP phenyl group) has been prepared and the rate of rotation of the substituted phenyl group determined from its ‘H n.m.r.spectrum. The rate is greater when R is electron-donating than when it is electron-withdraw- ing but is not proportional to the upvalues of R. Relative rotation rates for these complexes and analogues with other metals are in the order [TiP(TPPR)]> [InCl(TPPR)]>[RU(TPPR)(CO>(BU‘C,H~N)].~ Niobium and Molybdenum. The complexes [M203(TPP)2] (M = Nb or Mo),’ although having the same empirical formula have been shown by X-ray crystallo- graphy to have quite different structures.The niobium complex (1) has a triple oxygen bridge between metal atoms whilst the molybdenum complex (2) has a 0 N-N-N-N ‘h6’ /\\ I 000 0 I \\ 1 Nb 0 (1) (2) linear O(Mo)O(Mo)O group.6 This structural difference is thought to reflect the different affinities of the metals for the porphyrin core. Thus the more strongly binding molybdenum atom is displaced by only 90pm from the mean nitrogen atom plane towards terminal oxide. This requires an energetically demanding radial expansion of the porphinato-core and a close intramolecular porphyrin interplanar spacing. In the niobium complex the much larger displacement of the more weakly held metal atom (101pm) towards oxygen allows a decreased metal- porphyrin interaction and less radial strain within the porphyrin ring.6 A similar large displacement of niobium has also been observed’ in [Nb(O)(CO,Me)(TPP)].It has been suggested6 that the complexes [M203(TPP)2] (M =W or Re)5 have the same structure as (2). Treatment of [MoOP] (P = TPP or OEP) with anhydrous HCI in benzene gives the complexes [MC12P]. Thz X-ray structure of [MoCl,(TPP)] (p = 2.9 B.M.) shows that although the molybdenum atom is in the plane of the porphyrin nitrogen atoms the MoCl distances differ (234.7 and 227.6 pm) thus far inexplicably.8 M. Nakajima J.-M. Latour and J.-C. Marchon J.C.S. Chem. Comm. 1977 763. S. S. Eaton and G. R. Eaton J. Amer. Chem. SOC.,1977,99 6594. B. Fleisher and T. Srivastava Inorg.Chim. Acta 1967 5 151; J. W. Buchler L. Puppe K. Rohbock and H. H. Schneehage Chem. Ber. 1973,106 2710. J. F. Johnson and W. R. Scheidt J. Amer. Chem. SOC.,1977,99 294. ’C. Lecomte J. Protas R. Juilard B. Fliniaux and P. Fournari J.C.S.Chem. Comm. 1976 434. T. Diebold B. Chevrier and R. Weiss Angew. Chem. Internat. Edn. 1977 16 788. Chemistry of the d-and f-Block Metals Manganese and Rhenium. An X-ray study of [Mn(TPP)] which binds dioxygen at low temperatures showed minimal structural differences at -175 "C compared to 20 "C. The manganese(I1) d5-ion is expected to be too large to fit into the plane of the porphyrin ring and the metal atom has a high degree of thermal motion in which it probably alternates between positions above and below the porphyrin plane.' On the basis of ab initio calculations it has been suggested that dioxygen should bind to this complex in a terminal-bent rather than sideways fashion and that the valency formalism [Mn"'-O2-] rather than [Mn'V-022-] (as was previously suggested; see last year's Report) should describe the metal-dioxygen interaction." Displacement of the large high-spin manganese(I1) ion out of the plane of the porphyrin nitrogen atoms (by 56 pm) occurs in the square-pyramidal complexes [Mn(TPP)(l-methylimidazole)] A smaller displacement (27 pm) of the smaller manganese(Ir1) ion occurs in [MnCl(TPP)] which also has a (slightly distorted) square-pyramidal structure.l2 Dechelation of manganese(I1) from the complex [Mn{TNMPP(-3)}] occurs under acidic conditions at a rate more than lo6 times faster than for analogous complexes of manganese(111).~~ Oxidation of [{Re(C0)3}2(TPP)](3) with SbC15 gives the products shown in reaction (1).The oxidation state of rhenium in (4)is formally 1.5 and its Re-Re distance (295 pm) which is shorter than that of (3) (312 pm) indicates that there is a metal-metal interaction. The TPP ligand of (4)is distorted; the two pyrrole rings which co-ordinate both rhenium atoms are coplanar with the mean plane of the macrocycle whereas the other two rings are tilted towards the metal ions to which they are co-ordinated [see structure (4)].The structure of (5) which formally contains Re"' is considered to have a similar arrangement of metal atoms.14 Iron. Of all porphyrin complexes those of iron receive the most attention because of their obvious relevance to biological systems.Those aspects examined this year include the synthesis of dihaem- and polymer-bound haem-complexes the binding of various ligands at iron centres oxidation and reduction of iron porphyrin complexes and n.m.r. properties. The dihaem complex (6) has been synthesized and the ligation of the iron centres by dioxygen and carbon monoxide studied. Like monohaem compounds (6) binds dioxygen reversibly but unlike the monomeric complexes it binds two molecules of CO with different rate constants. It has been suggested that the first fast rate J. F. Kirner C. A. Reed and W. R. Scheidt J. Amer. Chem. SOC. 1977,99 1093. lo A. Dedieu and M. M. Rohmer J.Amer. Chem. SOC. 1977,99 8050. J. F. Kirner C. A. Reed and W. R. Scheidt J.Amer. Chem. SOC. 1977,99 2557. A. Tulinsky and B. M. L. Chen J. Amer. Chem. SOC. 1977,99 3647. l3 P. Hambright Znorg. Nuclear Chem. Letters 1977 8 403. S. Katon M. Tsutsui D. L. Cullen and E. F. Meyer jun. J. Amer. Chem. SOC. 1977 99 620. J. R. Dilworth G. J. Leigh R. L. Richards and K. W. Bagnall 0 1 (4) (Ph groups omitted) X I Me Et 7 Me 0 MeO,CCH,CH Me I X (6) X (when present) =O2or CO corresponds to binding at one iron which is partially in a strained four-co-ordinate form. After binding CO this iron centre closes to a six-co-ordinate form making available a less strained conformer about the central C-C bond (A) so that the second iron atom binds CO by a slower associative me~hanism.'~ The stimulus for the above work is the occurrence of four integrated haem units in haemoglobin and another advance in the synthesis of analogues of natural carriers of dioxygen has been the linkage of an [Fe(PPIX)] core to a polymer surface cia condensation of a l5 T.G. Taylor Y. Tatsuno D. W. Powell and J. B. Cannon J. C. S. Chem. Comm. 1977,732. Chemistry of the d-and f-Block Metals 173 peripheral carboxylate group. The linking group and a porphyrin side-chain carry imidazole groups which can axially ligate the iron centre. The dithionite-reduced haem polymer is very soluble in water and can take up dioxygen reversibly through several cycles before being irreversibly oxidized.Reduction with dithionite restores dioxygen-carrier activity.16 Interaction of dioxygen with iron(I1)-porphyrin complexes generally leads to irreversible oxidation unless measures are taken to prevent it (see above and last year's Report). Generally the oxidation process is considered to involve a dioxygen-bridged intermediate. This year such an intermediate [{TPP(p-Me)}FeO,Fe{TPP(p-Me)}] (petf=2.2 B.M. at -83 "C) which is involved in the interaction of [Fe{TPP(p-Me)}] with dioxygen in toluene at -80 OC has been detected by its 'H n.m.r. spectrum. It changes into [{TPP(p-Me)}FeOFe{TPP(p-Me)}] at -30 OC." Axial inner-sphere electron-transfer mechanisms are thought to operate in the oxidation of high-spin Fell-porphyrin complexes by quinones (to give hydroquinones) or aromatic nitro-compounds.l8 Low-spin axially ligated five- or six-co-ordinated porphyrin complexes are much more difficult to oxidize; they generally require the presence of an acid and use an outer-sphere mechanism.'* The complex [FeCl(OEP)] catalyses the epoxidation of cyclohexene in nitrobenzene solution. The mechanism of the reaction is not clear but it does not appear to involve a direct iron-dioxygen interaction since the cobalt(II1) analogue which is inert to dioxygen is also an active catalyst." Iron-porphyrin complexes with axial mercaptide ligands reproduce the charac- teristic U.V. absorptions at about 450 nm and about 360 nm (generally obscured) observed for cytochrome P-450 in the presence of CO. It has been shown that this characteristic spectral pattern arises by mixing of a charge-transfer transition from a lone-pair sulphur orbital of the mercaptide to a porphyrin ring orbital [e.g.(T*)] with a transition of the porphyrin ring that has the same symmetry [al,(T) a2,(7r)-* e,(~)].~' Generally the P-450-type spectra are shown by iron(I1) complexes such as [Fe(SR)(TPP)(CO)] but the low-spin iron(II1) complexes formulated as [Fe(SR)2{PP(IX)DME}]- and [Fe(SR)(PP(IX)DME}(PEt,Ph)] (R = Bun Ph C6H4CH2 or p-NO2C6H4) have now been shown also to have these spectral features. Evidently the combinations of iron(II1) with either two SR groups or one SR plus one PEt2Ph group are equivalent to iron(I1) with ligating SR plus axial CO in producing the right conditions for suitable mixing of charge-transfer transitions.21 The complex [Fe(C,H,s)(TPP)(PhSH)] which also has a P-450-type spectrum changes from a high- to a low-spin configuration as its temperature is lowered.A multiple-temperature X-ray study of this process has revealed that at 115 K the complex forms a 1:2 disordered mixture of five-co-ordinate high-spin [Fe(PhS)(TPP)] and six-co-ordinate low-spin [Fe(PhS)(TPP)(PhSH)]. At 4.2 K [Fe(PhS)(TPP)(PhSH)] is virtually exclusively formed and thus the change to the l6 E. Bayer and G. Holzbach Angew. Chem. Internat. Edn. 1977,16 117. l7 D.-H. Chin J. D. Gandio G. N. LaMar and A. L. Balch J. Amer. Chem. SOC.,1977 99 5486. C. E. Castro G. M. Hathaway and R. Havlin J. Amer. Chem. Soc. 1977 99 8032; J. H. Ong and C. E. Castro ibid. p. 6740.l9 M. Baccouche J. Ernst J.-H. Fuhrhop R. Schlozer and H. Arzoumanian J.C.S.Chem. Comm. 1977 821. 20 L. K. Hanson W. A. Eaton S. G. Sligar I. C. Gunsalus M. Gouterrnan and C. R. Connell J. Amer. Chem. SOC.,1976,98,2676. H. H. Ruf and P. Wende J. Amer. Chem. SOC.,1977.99 5499. 174 J. R. Dilworth G.J. Leigh R. L. Richards and K. W.Bagnall high-spin form is associated with the loss of a thiol ligand.22 Further refinement of this work will establish more clearly its detailed mechanism and its relation to the change from a low-spin to a high-spin configuration that is undergone by cyto- chrome P-450 on binding a substrate. The binding of various other neutral and anionic ligands to iron-porphyrin centres has been studied. The 'H n.m.r.linewidths of the complexes [FeCl(P)B,] (P = TPP OEP or TPrP; B = substituted imidazole or pyridine) have shown that the lability of the axial ligands B is increased by electron-donating substituents on the porphyrin electron-withdrawing groups on the imidazole or greater steric bulk of the substituents of B. Pyridines are more labile than imidazole~.~~ A kinetic study of the displacement of Me2S0 from the complex [Fe(TPP)(Me,SO)]' by imidazole (ImH) has shown that the first step is addition of ImH followed by the rate-determining displacement of Me,SO by ImH to give [Fe(TPP)(ImH)2]+.24 Deprotonation (by such bases as hydroxide or Bu'O-) of ImH ligating this latter complex [equation (2)] has been postulated to occur but attempts to isolate (7) and (8).gave only {Fe(TPP)(Im)}n.2s -H+ -H+ [Fe(TPP)(ImH)2]+ [Fe(TPP)(Im)(ImH)] + [Fe(TPP)(Im)J (2) +H+ +H+ (7) (8) Substituent effects on the ligation of pyridine in [FeCI{TPP(m-or p-R)}-(py),(DMFX-,] and [Fe{TPP(rn-or p-R)}( py),(DMF)2-,] (R = various substi- tuents n = 1 or 2 py = pyridine DMF = dimethylformamide) have been examined electrochemically.Values of the Hammett reaction parameter p derived from equilibrium constants for binding of pyridine were independent of the degree of both axial ligation and of the meta- or para-substituent for the iron(1r) series. For the iron(1II) complexes however whereas the value for [FeCl{TPP(m -R)}-(DMF)( py)] (-0.123) differs from that of its para-substituted analogue (-0.454) only a single value is obtained for [FeCl{TPP(m -or p-R)}( p~)~] (-0.433).26 Adducts of iron(I1) porphyrins with nitroso-alkanes e.g.[Fe(TPP)(RNO)B] (R = Me Pr' or PhCH2CH2; B = various N-donor bases),27 and with dichlorocarbene e.g. [Fe(TPP)(CC1,)],28 have been reported. The X-ray structures of two different crystalline forms of the nitrosyl adduct [Fe(TPP)(NO)(p-CH,C,H,N)] have been determined. These structures differ in their Fe-N (N = axial pyridine nitrogen atom) distances (232.8 and 246.3 pm) and corresponding Fe-N-0 angles (138.5' and 143.7" respectively). 'The iron atom is also displaced out of the porphyrin-N plane towards NO by 9 and 11 pm respectively. The reasons for the occurrence of two crystalline forms are not clear but a linear correlation between v(N0) and Fe-N for these and related nitrosyl adducts was demonstrated and was consid- ered to reflect the lengthening of the Fe-N bond as a result of varying electron 22 J.P. Collman T. N. Sorrell K. 0.Hodgson A. K. Kulrestha and C. E. Strouse J. Amer. Chem. SOC. 1977,99,5180. 23 J. D. Saterlee G. N. LaMar andT. J. Bold J. Amer. Chem. SOC.,1977 99 1088. 24 R. F. Pasternack and J. R. Stahlbush J.C.S.Chem. Comm. 1977 106. 25 M. Nappa J. S. Valentine and P. Snyder J. Amer. Chem. SOC.,1977 99 5799. 26 K. M. Kadish and L. A. Bottomley J. Amer. Chem. SOC.,1977,99 2380. 27 D. Mansuy P. Battini J. C. Chottard and M. Lange J. Amer. Chem. SOC.,1977,99 6441. 28 D. Mansuy M. Lange J. C. Chottard P. Gueri P. Maliere D. Brault and M. Rougee J.C.S. Chem. Comm. 1977 648. Chemistry of the d- and f-Block Metals 175 release from the trans-NO ligand to the iron d,.orbital. The more nearly linear is the NO ligand the greater is its electron release.29 The demetallation of the complexes [FeCl(P)] (P = TPP or DPME) by HCl only proceeds via formation of iron(I1tporphyrin intermediates in their solutions pro- duced by the addition of iron(^^).^' The aquation of [Fe(TNPP-4)IS' over a pH and ionic strength range has been found to follow equilibria (3),(4) and (5). At pH 1-3 the solution contains the five-co-ordinate high-spin complex but at pH 10-12 the low-spin six-co-ordinate p-0x0-dimer is the major species [FeP(H2O)I5'+ H20 2 [FeP(OH)(H20)l4+ (31 [FeP(OH)(H20)l4++ [FeP(OH>2l3' (4) 2[FeP(OH)*j3+ S [{FeP(OH)}20]"+ (P = TNPP 4-) Other n.m.r.and related examinations of iron porphyrin complexes have been made. The 'H n.m.r. data yield a highly anisotropic magnetic moment (pi= 4.9B.M. and pll= 2.2 B.M.) for [Fe(TPP)] and the observed contact shifts confirm the intermediate spin ground-state configuration [S = 1;(dxy)2 for (dz2)2,(d,, ~d,,)~] the complex.32 The porphyrin 'H n.m.r. shifts of a variety of high-spin five-co- ordinate axial adducts of [Fe(TPP)] and related complexes with pyridine or methyl-substituted imidazoles are relatively insensitive to the axial base and therefore unlikely to be useful probes of biological The axial imidazole shifts however are consistent with primarily o-spin transfer to the metal and may provide a probe for this interaction in other specie^.'^ The zero-field splitting parameter for high-spin [FeCl(TPP)] (D= 5.9* 0.1 cm-') obtained from its single- crystal anisotropy is less than earlier values but close to the value (6.95 cm-') for chlorohaem and [FeCl{PP(IX)DME}].34 Cobalt and Rhodium.Dinuclear cobalt complexes of cofacial porphyrin ligands have been synthesized in two separate laboratories. Kang35 has synthesized the ligand (9) and prepared a dicobalt(I1) adduct. In toluene-dichloromethane solution kc / LN?YN 0'1 Y H"-/ \ -I R (9) R = n-hexyl 29 W. R. Scheidt A. C. Brinegar E. B. Ferro and J. F. Kirner J. Amer. Chem. SOC.,1977,99 7315. 3" J. H. Espenson and R. J. Christensen Znorg. Chem. 1977 16,2561. '' R. F. Pasternack H. Lee P. Malek and C. Spencer J.Znorg. Nuclear Chem.. 1977 39 1865. '' H. Goff,G. M. LaMar and C. A. Reed J. Amer. Chem. SOC.,1977,99 3641. 33 H. Goff and G. N. LaMar J. Amer. Chem. Soc. 1977,99,6599. 34 D. V. Behere V. R. Marathe and S. Mitra J. Amer. Chem. Soc. 1977 99 4149. 35 C. K. Kang J.C.S. Chem. Comm. 1977,800. 176 J. R. Dilworth G. J. Leigh R. L. Richards and K. W.Bagnall the dinuclear cobalt complex reacts with air and 1-triphenylmethylimidazole (Ph,CIm) to give a diamagnetic pperoxo-complex which can be converted into a p-superoxo-complex by oxidation with di-iodine. The e.p.r. spectrum of the latter paramagnetic complex is consistent with the unpaired electron being mainly on oxygen i.e. the bonding description [(Ph~CIm)Co"1P-02-Co'1'P(ImCPh3)].35 Related dinuclear porphyrin ligands have been prepared by Collman and co- worker~.~~ Their bis-Co" derivative (with 1-methylimidazole as the axial base) has on the basis of e.p.r.data 'face-to-face' interacting metal atoms separated by about 650-680 pm. A copper derivative has also been prepared (see beIo~).~~ Rever-sible binding of dioxygen to the complexes [Co(TPPR)] where R=H O(CH2)4C(0)NHC5H4Nor O(CH2)3C5H4N occurs at low temperature and its dependence upon the nitrogen-base substituents has been determined by U.V. spectroscopy. The pyridine-analogue substituents at the phenyl ring of TPP are able to bind axially to the metal but have little effect on the strength of binding of dioxygen.37 The X-ray structure of [CoCl(TPPNMe)] (TPPNMe = N-methyl apy8-tetra- phenylporphyrin) reveals that the complex is a distorted square pyramid with an axial chloride.The methylated nitrogen is a greater distance (238.1 pm) from cobalt than are the other nitrogen atoms (201.6 pm) and its associated pyrrole ring is distorted out of the porphyrin plane so as to block the sixth co-ordination position of the metal. The high-spin cobalt atom is displaced towards the ~hloride.~~ Free-energy data for the substitution of water in [Co(TNMPP4-) (H20)2]5+ by anionic ligands such as NCS- to give [CO(TNMPP~-)(H,O)(CNS)]~+ have been determined.39 The first hydride complex of a rhodium porphyrin derivative [RhH(OEP)] has been prepared by treatment of [RhCl(OEP)] with dihydrogen in methan01.~' In benzene solution it loses dihydrogen to give the violet diamagnetic dimer [{Rh(OEP)},] (see Chapter 9).Copper. Dinuclear cofacial copper(I1) analogues of the above cobalt complexes prepared by Collman also show a metal-metal intera~tion.~~ Copper-substituted cytochrome c has been synthesized by dialysis of freshly prepared solutions of cyctochrome c against copper(I1) acetate at 4 0C.41It has the same electrophoretic and ion-exchange behaviour as the native enzyme and its e.p.r. and U.V. properties at pH 4-1 1show it to contain six-co-ordinate copper. This behaviour is unique to the natural protein because copper porphyrins normally do not take on two axial ligands. The new technique of X-a multiple scattering has been used to derive the electronic structure and spectral parameters of square-planar copper porphyrins.The values obtained are reasonably consistent with those derived from more established methods except for the values concerned with electronic excited 36 J. P. Collman C. M. Elliot T. R. Halbert and B. S. Tovrog Proc. Nu?. Acad. Sci. U.S.A.,1977,74 18. 37 F. S. Molinaro R. G. Little and J. A. Ibers J. Amer. Chem. Soc. 1977 99 5628. '* 0.P. Anderson and D. K. Lavallee J. Amer. Chem. Soc. 1977.99 1404. 39 K. R. Ashley J. Inorg. Nuclear Chem. 1977 39 357. 40 H. Ogoshi J. Setsune and Z. Yoshida J. Amer. Chem. SOC.,1977 99 3869. M. C. Findlay L. C. Dickinson and J. C. W. Chien J. Amer. Chem. Soc. 1977 99 5168. 42 D. A. Case and M. Karplus J. Amer. Chem. SOC.,1977.99 6182. 177 Chemistry of the d-and f-Block Metals Complexes of Dinucleating Ligands.-The complexing of two metal ions by the same ligand has intrigued chemists for a long time because of the possibility of studying metal-metal interactions and of using a combination of catalytic prop- erties to effect complicated transformations of substrates.Ligands which can combine two metal ions are termed 'dinucleating' and transition-metal complexes with dinucleating ligands have been reviewed Complexes of dinucleating ligands are different from dinuclear complexes although the differences are often rather small. Thus in a recent example taken at random,44 in complex (10) the square-pyramidal copper atoms are in a dinuclear 2+ (10) complex. Nevertheless this complex is of interest since it is diamagnetic.The spin-pairing is indicative of a strong metal-metal interaction which is not always observed in such systems. On the other hand the complex (11; R = H) has a genuine dinucleating ligand,4s prepared from 5-methyl-2-hydroxy-isophthalaldehyde and 1,3-diaminopropane in the presence of CU(C~O~)~,~H~O. It can be reduced electrochemically to a CU'~-CU~ species which (as deduced from the four-line e.p.r. spectrum at liquid-nitrogen temperature) contains distinct Cur' and Cu'. This spectrum for unknown reasons is temperature-dependent. The reduced homologue (11;R =Me) also contains Cut' and Cur but the e.p.r. spectrum is not dependent on temperature. These species may contain five-co-ordinate Cu'. M e RwR \ (11) However there is also an intermediate stage between dinuclear and dinucleate represented by (12) in which one of the metal ions is not completely enclosed.Complex (12) is diamagnetic and therefore may contain Vv+Cu' rather than 43 V. Casellato M. Vidali and P. A. Vigato Coordination Chem. Rev. 1977 23 31. 44 J. S. DeCourcy T. N. Waters and N. F. Curtis J.C.S. Chem. Comm. 1977 572. 45 R. R. GagnC C. A. Koval and T. J. Smith J. Amer. Chem. Soc. 1977,99 8368. J. R. Dilworth G. J. Leigh R. L. Richards and K. W. Bagnall r R' (12) X=C1 or Br V'" +Cur' which might be expected to yield overall pararnagneti~m.~~ This kind of interaction may have very significant consequences. For instance the complex [Eu(fod),] (fod = heptafluorodimethyloctanedionate) is a widely used n.m.r.shift reagent and has now been shown to be efficacious with complexes with which it is proposed to interact in the manner shown (13).47 Generally when two complexing sites are available in a dinucleating ligand then both may be occupied by metal atoms of the same kind. Examples include the ligand (14) (LH,). LH3 forms a (13) (14) complex containing Fe [Fe2C12(0H2)L] in which the co-ordination number of one iron atom is made up by the water A related system (without the central phenolic OH) binds Ni and Co using subsidiary ligands to make up co-ordination numbers.49 The ligand (15) with two similar sites binds 2 atoms of types such as Cu Ni and CO.~'However when the two sites in a dinucleating ligand are not identical then the possibility arises that a given metal atom might prefer one site to the other.Thus o -acetoacetylphenol condenses with ethylenediamine in EtOH to yield (16).51 Reaction with nickel(1r) acetate in dichloromethane-ethanol results in the nickel ion being complexed by the four oxygen atoms. Subsequent treatment with 46 K. Okawa and S. Kida Inorg. Chim. Acta 1977 23 253. 47 L. F. Lindoy and W. E. Moody J. Amer. Chem. SOC.,1977.99 5863. 4R N. A. Bailey E. D. McKenzie J. M. Worthington M. McPartlin and P. A. Tasker Inorg. Chim. Acta 1977.25 L137. 49 R. Robson and D. G. Vince Inorg. Chim. Actu 1977 25 191. D. E. Fenton and S. E. Gayda J.C.S. Dalton 1977 2095. D. E. Fenton S. E. Gayda U. Casellato M. Vidali and P. A. Vigato Inorg. Chim. Actu 1977 21 L29. Chemistry of the d-and f-Block Metals M c m M e 0 .o..H" ."'"'1 NH 0 HN H... ..H /0' 0 N NH 0 HN M e w M e (15) (16) uranyl(v1) acetate produces a new complex in which U02 is bound by the N202 donor set the nickel still being bound by the O4donor set. An extensive series of researches has been reported concerning the ligand (17).52 For R= (CH& and R'=R2=Me the reaction with one equivalent of copper(I1) acetate results in the N202donor set being occupied by Cu; two equivalents give a mixture of 3 complexes one with a copper atom bound by both N202and O4donor sets and the other two in which each set is taken up individually. Uranyl and vanadyl prefer the O4set whereas nickel prefers N202.52This is however subject to change if minor variations are made in the ligand.Thus copper prefers the N202 set in the ligand (17; R' = R2= alkyl). In (17; R' = alkyl R2=phenyl) copper apparently prefers the O4set. In (17; R1 = R2=Me) either set can be R'yyy fNH OH O R 'NH 0 OH R ,UR2 (17) By suitable choice of ligand and conditions a variety of mixed complexes has been prepared Ni[ N202] /Cu[ 04]; Ni [N202] /VO[04] ; Cu[N202]/U02[04]; and Cu[N202]/Zn[04]. One awaits with interest the reports of the mutual influence of one of these metal ions on the properties and reactivity of the other. Aspects of the Chemistry of Complexes with Macrocyclic Ligands.-Macrocyclic ligands have received a lot of attention lately often because of some supposed value for the understanding of biological systems.The properties of the complex metal ions are affected by factors such as the size of the macrocyclic ring ring unsaturation and ring substitution. A considerable amount of effort has been put into determining the influence of ring size and the study of saturated systems has been rewarding. These ligands are usually denoted by a trivial nomenclature '* D. E. Fenton and S. E. Gayda J.C.S. Dalton 1977 2101. J3 D. E. Fenton and S. E. Gayda J.C.S. Dalton 1977 2109. 180 J. R. Dilworth G.J. Leigh R. L. Richards and K. W.Bagnall [ 13]aneN4 is a thirteen-membered saturated ring containing 4 nitrogen atoms generally symmetrically arranged. A thermodynamic study has been made of the complexing of Cu2' with [9]aneN3 and with H2N(CH2)2NH(CH2)2NH2.54 The respective equilibrium constants are very similar but the [9]aneN3 presumably takes up the constrained facial positions so that its enthalpy contribution is less than for the open-chain ligand.The entropy contribution almost exactly compensates for the deficiency in the enthalpy contri- bution. By contrast [14]aneN4 forms much more stable complexes with Cu2+ than does the open-chain analogue.55 A direct comparison has been made of the compounds [12]- [13]- [14]- and [15]-aneN as complexing agents for Cu". AHe is always greater than for the corresponding open-chain ligand and is a maximum at [14]aneN4. The enthalpy contribution to the extra macrocyclic stability is in fact less for Cu2' than for Ni2' but is still significant even for [12]aneN4.56 However it has also been suggested that the factor having the major influence on the value of the Dq's produced by macrocyclic ligands is the distance between metal and donor atoms whether the ligand is open-chain or cyclic being in~idental.~' For complexes of [ 14]aneN4 and of the open-chain tetramines H2N(CH2)2- NH(CH2)3NH(CH2)2NH2 (1 9) with (18) and H2N(CH2)3NH(CH2)2NH(CH2)3NH2 Ni2+ the equilibrium (6) has been observed (L is one of the three ligands just [NiL(H20)2]2+$ [NiL]*++ 2H20 (6) blue yellow cited).The respective equilibrium constants are in the order [14]aneN4 > (18)> (19) but it is claimed that there are no special cyclic factors involved and that the origin of these different equilibrium constants lies in steric repulsions.It has been suggested on the basis of spectral data that the [12]aneN4 forms stronger bonds to Ni2+ than either [14]- or [15]-aneN4 and that this is primarily a size That being so then a different ion of different size should fit another macrocycle better than it fits [12]aneN4. A series of complexes [C~L(anion)~]' has been prepared (L= [13]aneN4-[16]aneN4 inclu~ive).~~ Values of Dq due to the macrocycles are in the order [14] > [13]> [15]> [16]. It has been suggested that Co3' fits [14]aneN4 best and that [13]aneN4 is too small whereas [15]- and [16]-aneN4 are too big. This is also reflected in the chemistry. Thus for [CoLCl,]' (L=[13]aneN4-[16]aneN4 inclusive) the rate constants for the aquation of the first chloride in 0.1MHN03 vary from 2.6-1.1~10-~s-~ in the order [16]>[15]>[13]>[14].60 It has been found that for the unusual ion Mn3+ [14]aneN4 is a better ligand than [ 15]aneN4.61 " L.Fabbrizzi and L. J. Stompa Znorg. Nuclear Chem. Letters 1977,13 287. '5 M. Kodama and E. Kimura J.C.S.Dalton 1977 1473. 56 A. Anichini L. Fabbrizzi P. Paoletti and R. M. Clay Znorg. Chim. Actu 1977 22 L25. '' D. Gattesschi and A. Scozzafava Znorg. Chim. Acta 1977 21 223. '* A. Anichini L. Fabbrizzi P. Paoletti and R. M. Clay Znorg. Chim. Acru 1977 24 L21; L. Fabbrizzi Znorg. Chem. 1977 16 2667. 59 Y. Hung L. Y. Martin S. C. Jackels A. M. Tait and D. H. Busch J. Amer. Chem. SOC.,1977 99 4029. 6o Y. Hung and D. H. Busch J. Amer. Chem. SOC.,1977,99,4977. 6' P. S. Bryan and J. M. Calvert Znorg.Nuclear Chem. Letters. 1977 12 615. Chemistry of the d- and f-Block Metals Extension to substituted ligands62 introduces possibilities of isomer formation which are not entirely absent with the unsubstituted rings.60 If the ring is unsaturated that introduces further complications. A comparison has been made of the ligands [14]aneN4 (L') Me6[14]-4,11-dieneN4 (L') [141-4,7,11,14-tetraeneN (L3) and [ 141-4,7-dieneN4 with C02+.63 Complexes isolated include [CoL'I2+ [COL~(H~O)~]~+ All three have low-spin cobalt and [COL~(H~O)~]~+. but [COL'(H~O)~]~+ could not be synthesized. Evidently axial interactions increase with the degree of unsaturation of the ring. Hydrolysis of rneso-[CoLC12] (L = Me6[ 141-4,ll-dieneN,) by base has been shown to proceed in two steps both dissociative in character The replacement of the first chloride is nine times as fast for the complex of 5,12-Me2[14]-4,ll-dieneN,and between lo2 and lo3 times as fast as for the complex of the saturated ligand.Evidently ring unsaturation tends to stabilize the intermediate of low co-ordination number (in this case 5).64 The degree of unsaturation has been shown to affect the specific rates of hydrolysis reactions in similar A very extensive study of Co complexes with various [14]N4 rings suggests that the Co2'/Co' redox couple is much affected by ring unsaturation; the greater the degree of unsaturation the more stable is the lower oxidation state.66 This is also so in more complex systems. Thus the quinqueden- tate macrocyclic ligand (20) and Mn2' form pentagonal-bipyramidal complexes [Mn(20)(NCS)2] for 1 = rn = 3 and n = 2 and anion = NCS,67" with 5 nitrogen atoms in the pentagonal plane.Such a structure also seems to hold for 1= rn = n = 2 and for 1 = rn = 2 and n = 3. Such complexes can be oxidized to Mn3' species but oxidation does not occur so easily if the ligand is uncharged or the ring is unsaturated. Oxidation to Mn3' does not occur if the macrocyclic ligand (21) fN (14-membered ring) is in the complex. Oxidation of the complex of (20; 1= rn = n = 2; 15-membered ring) is easier than for the complexes of (20; 1 = rn = 2 n = 3; 16-membered ring) and (20; 1= rn = 3 n = 2; 17-membered ring).676 Perhaps not 62 R. W. Hay and D. P. Piplani J.C.S. Dalton 1977 1956; R.W. Hay D. P. Piplani and B. Jeragh J.C.S. Dalton; 1977 1951; T. J. Lotz and T. A. Kaden J.C.S. Chem. Comm. 1977 15. 63 J. F. Endicott J. Lilie J. M. Kuszaj B. S. Ramaswamy W. G. Schmonsees M. G. Simic M. D. Glick and D. P. Rillema J. Amer. Chem. Soc. 1977,99,429. 64 P. L. Kendall and G. A. Lawrence Austral. J. Chem. 1977,30 1841. 65 C.-K. Poon and C.-L. Wong J.C.S. Dalton 1977 523. 66 A. M. Tait F. V. Lovecchio and D. H. Busch Inorg. Chem. 1977,16,2206. 67 (a)M. G. B. Drew A. J. bin Othman S. G. McFall P. D. A. McIlroy and S. M. Nelson J.C.S.Dalton 1977,438; (b)J. C. Dabrowiak L. A. Nafie P. S. Bryan and A. T. Torkelson Inorg. Chem. 1977,16 540. 182 J. R.Dilworth G. J. Leigh R. L. Richards and K. W.Bagnall surprisingly redox potentials also vary between diastereoisomers,68 but a considerable amount of work remains to be done before all the influences on the redox potential and mechanism69 can be disentangled and understood.3 Small Multiply- bonding Nitrogen Ligands The chemistry of the nitrosyl ligand has continued to be a major source of interest. This stems in part from the bent-straight (1-electron-donor-3-electron-donor) problem and in part from problems associated with the reactivity of NO and with its occurrence in exhaust fumes. There have also been several ingenious attempts to overcome the problems associated with the oxidizing power of NO when it encounters complexes that contain transition metals in low oxidation states. The bent-straight nitrosyl transition has been discussed in terms of the stereo- chemical control of valence.This is the phenomenon whereby a closed-shell complex can take on an extra ligand the ligand electrons being accommodated by passing an electron pair from the metal to a three-electron donor such as NO which consequently becomes a one-electron donor. The oxidation state of the metal changes accordingly. The complex [Fe(NO)(Me2AsC6H4-2-AsMe2)2]2+ has a square-pyramidal configuration with a straight NO ligand at the apex LFeNO = 172.8(7)" N-0 = 141.1(27) pm. Its reaction with NCS-produces [Fe(NCS)- (NO)(Me2AsC6H4-2-AsMe2)]+, in which LFeNO is now 158.6(9)0 and N-0 = 109.6(10)pm.70 In the former case the oxidation state of the iron is taken to be (I) and in the latter (111).Another series of iron nitrosyl complexes has been reported namely ~~~~s-[F~(NO)(S~CNM~~)~M~CN]' and cis- and trans-[Fe(NO)- (S2CNMe2)2X] (X=Br NO C1 Br I efc.). The first compound is made by the action of NO[BF,] on [Fe(S2CNMe2)2].71 The compound [Fe(NO)-(S2CNMe2)2(N02)] has a linear iron-nitrosyl system [ 174.9(5)"] with N-0 = 113.6(6) pm.71 There is however a problem of definition of oxidation state particularly where the configuration of the NO is not known. I.U.P.A.C. n~menclature'~ avoids this by the device of regarding NO as a neutral ligand in which no attention is paid to formalisms such as NO' or NO-. Thus the complexes [Mo(NO)ClSI2- and [Mo(NO)C14]- which by I.U.P.A.C. nomenclature would be designated as containing Mo'" have ;(NO) in the range 1675-1695cm-' and are claimed to contain M011,73a whereas the remarkable water-soluble species [Mo(NO)CI,(H,O)]~- [F(NO) = 1624 cm-'1 is said to contain Mo' predicated on NO+.736 However the NO is formulated the stability to water is unexpected.The iron nitrosyl species [Fe(CO),NO]- has been reportedly characterized by its i.r. spectrum and shown to have C3"symmetry. It now appears74 that in THF solution the i.r. spectrum is essentially doubled and this has been attributed to a J. Hanzlik A. Puxeddu and G. Costa J.C.S.Dalton 1977 542. 69 N. Al-Shatti M. G. Segal and A. G. Sykes J.C.S.Dalton 1977 1766. 70 J. H. Enemark R. D. Feltham €3. T. Hine P. L. Johnson and K. B. Swedo J. Amer. Chem. Soc. 1977 99 3285. " 0.A. Ileperuma and R. D.Feltham Inorg. Chem. 1977.16 1876. 72 'Nomenclature of Inorganic Chemistry Second Edition Definitive Rules 1970' I.U.P.A.C. Butter- worths London 1971. 73 S. Sarkar and A. Miiller (a)Angew. Chem. Internat. Edn. 1977 16,183; (6) ibid. p. 468. 74 K. H. Pannell Y.-S. Chen and K. L. Belknap. J.C.S.Chem. Comm. 1977 362. Chemistry of the d- and f-Block Metals 183 dissociation equilibrium involving a tight ion-pair based on a cation-nitrosyl inter-action the first of its kind to be recognized. Resolution of another spectroscopic conundrum has been achieved. The complex [Mn(C0)4(NO)] has been shown by X-ray analysis to have a trigonal- bipyramidal structure with NO in an equatorial position whereas the solution i.r. spectrum has been interpreted in terms of a trigonal bipyramid with axial NO.The spectrum of the complex in a matrix of N2 has now been shown to be in accord with the X-ray structure.75 Matrix (argon and methane) i.r. studies of [Fe(CO)2(NO)2] have demonstrated its dissociation to [Fe(CO)(N0)2]; in a dinitrogen matrix (at 20 K) N2 can be incorporated yielding the novel species [Fe(CO)(N,)(NO),] and [Fe(N2)2(N0)2].76 Similarly [CO(CO)~(NO)] yields [CO(CO)~(NO)] upon irradia- tion at 20 K and [Co(CO),(N,)(NO)] and possibly [Co(CO)(N,),(NO)] can be formed.77 NO is not labile under these conditions. The reduction of NO complexes if it is sufficiently extreme can lead to hyponi- trite (02N22-) complexes. The reduction of [Mn(CN)S(NO)]3- by sodium in liquid ammonia yields [Mn(CN)=,(NO)]"-; that of [Fe(CN),(NO)]-yields [Fe(CN)3(NO)]5- and [CI-(CN)~(NO)]~- yields in turn [Cr(CN)5(N0)]4- [ti(N0) = 1510cm-'1 [Cr2(CN)7(N0)2]7- [:(NO) = 1490 cm-'1 and [Cr2(CN)6(NO)2]'-[:(NO) = 1460 ~m-'].~' The structures of these remarkable species may contain bridging NO rather than hyponitrite but this has not been properly established.However [Pt(PPh,),(NO),] which reacts with carbon monoxide to yield CO + N20 has been shown to be a square-planar Pt" complex (22) with a planar five-membered ring.79 (22) Distances/pm Other bis(nitrogen) ligands have also been mentioned during the year. In the past for example the trioxodinitrate(2 -) ion has been characterized as its sodium salt and a few complexes have been identified in solution. It has now been shown that the reaction of [CO(NH,)~]~+ with MC12,6H20 (M=Mn Fe Co or Ni) in the presence of sodium trioxodinitrate yields crystalline materials [CO(NH,)~]~[M(N~~~)~],,~H~O.'~ These complexes have a characteristic i.r.spec- trum with bands at 1370-95 1240-60 1050-80 and 940-60 cm-' assigned to ti(N=N) and Y(N-0). The compound with M = Co rearranges in water to give [co(NH3)6]2[co2(N203)s], of unknown structure and all the compounds decom- pose slowly when heated yielding nitrosyl species. It has been suggested that the N20 in [Ru(NH,)~(N~O)]*+ is N-bonded to the ruthenium despite an earlier analysis of the i.r. spectrum which had been taken to indicate O-bonding.81 75 A. J. Rest and D. J. Taylor J.C.S. Chem. Comm. 1977 717. 76 0.Crichton and A.J. Rest J.C.S. Dalton 1977 656. 77 0.Crichton and A. J. Rest J.C.S. Dalton 1977 536. 78 J. Schmidt 2.anorg. Chem. 1977 431 284. '' S. Bhaduri B. F. G. Johnson A. Pickard P. R. Raithby G. M. Sheldrick and C. I. Zuccaro J.C.S. Chem. Comm. 1977 354. C. A. Lutz A Lomax and L. Toh J.C.S. Chem. Comm. 1977 247. F. Bottomley and W. V. F. Brooks Znorg. Chem. 1977,16,501. 184 J. R. Dilworth G.J.Leigh R. L. Richards and K. W.Bagnall The catalysis of the reaction (7) does not necessarily require the formation of a dinitrosyl or a hyponitrite as an intermediate though they may be involved. Thus C0+2NO -+ CO,+N,O (7) [RhC12(CO)J gives rise to a catalyst in ethanol solution but only under a mixture of CO and NO. Once generated the catalyst regenerates the starting material if exposed to CO alon'e and under NO alone it forms a red nitrosyl probably [RhClz(NO)z]-.The catalyst solution shows F(C0) at 2095 and F(N0) at 1715 and 1780 cm-' and a formulation for the catalytic species that has been suggested is the five-co-ordinate [RhClz(CO)(NO)2]- which contains Rh"' if one allows the formu- lation to contain NO'.82 A related series of complexes [M(NO)z(PPh3)z]' (M = Co Rh or Ir) has been shown to undergo exchange of phosphine on the basis of a 31P n.m.r. study but the mechanism is dissociative for M=Co and associative for M=Rh or Ir.83 The complexes [M(N0)2(PPh3)2] (M = Ru or 0s) react with CO to form N20 and CO and tricarbonyl species. It has been proposed that the key to this is the trans- formation @) with NO' and NO- then coupling to give N20.The Co and Fe analogues more prone to dissociative mechanisms do not produce N,0.83 [M"'(N0')2] 2 [M"2''(NO')(NO-)L] (8) Other interesting rhodium species mentioned during the year include [Rh(NO)- (PPh3),S02] which has a five-co-ordinate structure that is not easily described in ideal terms. The NO is 'bent'; LRhNO = 140.6(6)0 and N-0 = 19537) pm.84 The complex [Rh(cycl~-octadiene)~]' reacts with nitrosonium salts in MeCN to generate [Rh(MeCN)4(N0)]2'.85 This can be converted into [Rh(NO)-(S2CNMe2)3]+ which is fluxional down to -95 "C in solution has a low i(NO) and must be either octahedral with a straight NO or seven-co-ordinate with a bent NO.s5 A complex related to the precursor [Rh(MeCN)3(NO)(PPh3)2Jz+, has a bent NO; LRhNO = 118.4(6)" N-0 = 115.9(10) A rather unusual rhodium nitrosyl [Rh(NO)(N03)(PPh3)2] [;(NO) = 1655 cm-'1 has been obtained by con- verting [Rh(CO)CI(PPh,),] into [Rh(CO)(NO)(PPh,),Cl,] using sodium nitrite and hydrogen chloride and treating the latter [?(NO) = 1630 cm-'1 with silver nitrate." Finally the compounds [M(NO)(MeCN),(PPh,),]' (M = Rh or Ir) [?(NO) = ca.1540cm-'] react with catechol to form compounds (23) with a bent NO [i=ca. 1590 cm-'1 which in another manifestation of the stereochemical control of valence can lose a molecule of phosphine to give (24) in which NO is straight [Y(N0)=1850~m-'].~~ Bridging nitrosyls are not yet very common. New examples during the past year include [cL-(C~)-~-(N~)-{C~(C~HS))~I and [(ML),(NO)I' [{CL-(NO>CO(C,H,)}~I,~~ where M = Co or Fe and L = S(CH2)2NMe(CH2)2NMe(CH2)zS.90 Occasionally '* D.E. Hendrikson C. D. Meyer and R. Eisenberg Znorg. Chem. 1977.16 970. 83 S. Bhaduri K. Grundy and B. F. G. Johnson J.C.S.Dalton 1977 2085. 84 D. C. Moody and R. R. Ryan Inorg. Chem. 1977,16,2473. N. G. Connelly P. T. Draggett M. Green and T. A. Kuc J.C.S. Dalton 1977 70. 86 B. A. Kelly A. J. Welch and P. Woodward J.C.S. Dalton 1977 2237. A. Dowera and M. M. Singh Transition Metal Chem. 1977 2 74. M. Ghedini G. Dolcetti B. Giovanitti and G. Denti Inorg. Chem. 1977 16 1725. 89 W. A. Herrmann and I. Bernal Agnew. Chem. Internat. Edn. 1977,16 172. 90 H. N. Rabinowitz K. D. Karlin and S. J. Lippard J. Amer. Chem. SOC., 1977.99 1420.Chemistry of the d- and f-Block Metals (23) (24) cluster nitrosyls have been reported. Thus [Os3(CO),2] reacts with NO in octane at 126 "C to yield [OS,(CO),(NO)~] (two 3-electron donors replacing three 2-electron donors) which can react with CO to yield [OS,(CO)~,(NO)~] and with P(OMe)3 to give [Os3(CO),(NO)2{P(OMe)3}].91 The complex [Fe(CO)(N0)2(PMe2H)] reacts with [CO(C,H~)(CO)~] to produce (25) as one product of several.,' L Me2 J (25) Nickel nitrosyls are of interest because of the way they can change co-ordination number and stereochemistry. Thus [Ni(C0)2L2] reacts with NO[PFs] to form [Ni(NO)L,]' (n =2 or 3 for L=PPh3; n = 3 for L=PMe2Ph)., The compound [Ni(NO)(PPh,),]'[ G(N0) = 1755 cm-'1 has a C3"stereochemistry and dissociates in solution to yield [Ni(NO)(PPh,),]'.At -85 "C in solution it slowly reaches equilibrium with a square-planar form. It reacts with NaS2CNet2 to yield [Ni(NO)(PPh,),(S,CNEt,),] which is a single species and apparently fl~xional.,~ Cobalt nitrosyls of the type [CO(NO)~L~]Y = RCN ROH Me2C0 etc.; Y = (L PF6 BF, etc.) are readily available from the reaction of [{CO(NO)~C~},] with silver ion in the presence of L. They have ;(NO) at ca. 1800 1900 cm-.' with two linear NO The complexes [Co(WS,),]'- and [Fe(MS4)2]2- (M = Mo or W) react with NO to form 1 1adducts in which NO is bound to Co or Fe and has a stretching frequency of ca. 1700 ~m-'.,~ Ruthenium nitrosyls have long attracted attention and this is not changing. The complex [Ru(NO)(P~~PCH~CH~CH~PP~~)~]+ [N-0 = 120(1)pm _LRuNO = ca.174"] is very similar to its Ph2PCH2CH2PPh2 analogue in although its 1-electron-reduction product disproportionates more readily than that of the ethylene derivative. The novel nitrosyls [Ru(LL)~(NO)X] [fi(NO) = ca. 1910 cm-'1 (LL = violurate) have been rep~rted.~' The complexes [Ru(NO)(bipy),X]"+ (bipy = bipyridyl; X = CI N3 or NOz n = 2; X =NH3 py or MeCN n = 3) (py = 91 S. Bhaduri B. F. G. Johnson J. Lewis D. J. Watson and C. Zuccharo J.C.S. Chem. Comm. 1977 477. 92 E. Keller and H. Vahrenkamp Angew Chem. Internat. Edn. 1977 16 541. 93 S. Bhaduri B. F. G. Johnson and T. W. Matheson J.C.S. Dalton 1977 561. 94 D. Ballivet and I. Tkatchenko Inorg. Chem. 1977 16,945. 95 A. Miiller and S.Sarkar Angew. Chem. Internat. Edn. 1977 16 705. 96 G. Bombieri E. Forsellini R. Graziani and G. Zotti Transition Metal Chem. 1977 2 264. 97 C. Bremard M. Muller G. Nowogrocki and S. Sueur J.C.S. Dalton 1977 2307. 186 J. R. Dilworth G. J. Leigh R. L. Richards and K. W. Bagnall pyridine) undergo reversible 1-electron reduction and [Ru(NO)(bipy),Cl]' has been isolated. It was found that P(N0) correlates linearly with Ei and shows a drop of ca. 300 cm-' upon redu~tion.~~ For this and other reasons it is believed that the site of reduction is the NO (characterized as strongly 'NO+') rather than the ruthenium. The complex [R~(bipy)~(NO)Cl]~' reacts with aryldiazonium ions ArN2' to yield [R~(bipy)~(N~Ar)Cl]" which have high fi(N=N) (>1980 cm-') and hence probably contain 'ArN2+'.These compounds undergo irreversible 1-elec-tron reduction losing N2.99 However parallels between N2Ar and NO can be misleading if only because the chemical reactions open to N2Ar are so much greater. Thus [Ir(CO)Cl(PPh3)2] reacts with diazonium salts to give varieties of products depending upon the conditions. Amongst those described are a dinuclear bis(aryldiazenidoj-complex,'oo ortho-metallated species,1oo diazene and hydrazine and compounds [Ir(CO)C1(N2Ar)(PPh3)2X](X = anionic ligand) which possess doubly bent N2Ar groups ('N2Ar-').'02 The nitrosyls of Group VI elements have also elicited considerable interest. New synthetic routes to molybdenum nitrosyls have been described.lo3 The novel [Cr(N02),(NO)( py)],py has octahedral co-ordination LCrNO = 180.0" N-O(nitrosy1) = 115.0(1) pm and 0-bonded nitrito-gro~ps.~~~ Parenthetically a further mode of binding for NO2 has been suggested in a reformulation of the structure of Vkzes Red Salt as (26).lo5 Other chromium complexes that have been reported include [Cr(CN),-x(H20)x(N0)]'x-3'-(x = 3,4 or 5) which have been studied electrochemically,'06 and (27) which has a linear NO system in which N-0 = 119.3(6) pm.'" 2 Finally molybdenum and tungsten complexes of the type [M(CO),(LL)] (LL = bidentate neutral ligandj have been used to synthesize new nitrosyls and aryldiazenido-complexes.Thus [W(C0),(Me2PCH2CH2PMe2)] reacts with NO[PF6] to give fUC(?)-[W(CO)3(NO)(LL)][PF6]and with an excess of NO[PF,] 98 R.W. Callahan and T. J. Meyer Inorg. Chem. 1977,16,574. 99 W. L. Bowden G. M. Brown E. M. Gupton W. F. Little and T. J. Meyer Inorg. Chem. 1977 16 213. ''' N. Farrell and D. Sutton J.C.S. Dalton 1977 2124. lo' A. B. Gilchrist and D. Sutton J.C.S. Dalton 1977 677. R. E. Cobbledick F. W. B. Einstein N. Farrell A. B. Gilchrist and D. Sutton J.C.S. Dalton 1977 373. F. King and G. J. Leigh J.C.S. Dalton 1977 423. C. M. Lukehart and J. M. Troup Inorg. Chim. Acta 1977 22 81. lo5 A. E. Underhill and D. M. Watkins J.C.S. Dalton 1977 5. J. MocBk D. Bustin and M. Ziakova. Inorg. Chim. Acta 1977 22 185. lo' D.Webster R. C. Edwards and D. H. Busch Inorg. Chem. 1977 16 1055. 187 Chemistry of the d-and f-Block Metals to produce a further complex postulated to be [(CO)3(NO)W(LL)W(CO)3-(N0)I2'.The bipyridyl complex [M~(CO)~(bipy)] reacts with Z[PF6] (Z = NO or ArN2) to produce fa~-[Mo(CO)~(bipy)Z]' and oxidation of the diazenido-complex with bromine yields {M~Br~(bipy)(N~Ph))~ which has V(N=N) = 1390 cm-'. Now [(MO(CO),(N,P~)}~] has V(N=N)= 1479 cm-' so the value of 1390 cm-' is taken to indicate either doubly bent or doubly bridging N2Ph.'09 Nitrogen fixation has continued to receive a great deal of attention. Amongst new dinitrogen complexes reported are [M(N2)6] (M=Ti V or Cr). These were generally made by reactions of the metal atoms in a nitrogen matrix at 10-15 ~.110.111The titanium complex has V(NEN) at 2131 2100 and 2095 cm".llo From an analysis of the crystal-field and charge-transfer spectra of these complexes and of the analogous [M(CO),] it was concluded (again) that N2 is a poorer 0-donor and n-acceptor than CO."' The complexes [HgX2N2] (X = C1 Br or I) have been observed in Ar matrices."2 The first stable chromium derivative containing a tertiary phosphine ci~-[Cr(N,),(PMe,)~l has been reported.It has V(N=N) = 1990 1918cm-' and decomposes at room temperat~re.''~ The osmium com- plex [OS(M~~ASC~H~-~-ASM~~)~C~(N~)]+, which has v(NZN) = ca. 2080 cm-' depending on the counter anion,'' has been prepared from its nitrosyl analogue [V(N-0) also high at ca. 1860 cm-'1 by its reaction first with hydrazine and then with acid. The X.p.e. spectra of [OS(NH~)~(N~)~]CI~ and [OsC1(NH3)4(N2)OsCl(NH3)4]C13 have been measured. The latter contains both 0s" and Osrrl,and not 'averaged' o~miums.''~ However the most unusual dini- trogen complex reported during the year is [RhCl(N2)(PPri3)2]."6 This has been shown by X-ray analysis to possess N2 that is sideways bonded to a single rhodium V(NGN) = 2100 cm-' N-N = 83(2) pm the first of its kind.This astoundingly short N-N distance is paralleled by similar short distances in the O2[103(l)pm] and ethylene [131.0(4) pm] analogues. This is the shortest C-C separation yet observed for complexed ethylene. However these extra-short separations may be an artefact of crystal disorder. These results are even more unexpected when it is realized that the rhodium N2-complex [RhH(N2)(PBut2Ph)2] has normal end-on co-ordination of N2. The reactivity of co-ordinated N2 has received considerable attention both theoretically and empirically.The bonding of diatomic molecules in general to transition metals has been discussed. It has again been suggested that CO may be a better .rr-acceptor than N2.' '' A MO description of diazenido- dinitrogen- and related complexes has been used to discuss the successive protonations of co-ordinated Nz to produce NH3.'18 The analysis of alkylation of co-ordinated N2 J. A. Connor P.1. Riley and C. J. Rix J.C.S. Dalton 1977 1317. '09 D. Condon M. E. Deane F. J. Lalor N. G. Connelly and A. C. Lewis J.C.S.Dalton 1977 925. R. Busby W. Klotzbiicher and G. A. Ozin Inorg. Chem. 1977,16,822. "' A. B. P. Lever and G. A. Ozin Inorg. Chem. 1977,16 2012. ''* D. Trevault D. P.Strommen and K. Nakamoto J. Amer. Chern. SOC.,1977 99 2997. H. H. Karsch Angew. Chem. Internat. Edn. 1977 16 56. F. Bottomley and E. M. R. Kiremire J.C.S. Dalton 1977 1125. C. Battistoni C. Furlani G. Mattogno and G. Tom Inorg. Chim. Acta 1977 21 L25. 'I6 C. Busetto A. D'Alfonso F. Maspero G. Perego and A. Zazzetta J.C.S. Dalton 1977 1828. 'I7 R. Hofmann M. M.-L. Chem and D. L. Thorn Inorg. Chem. 1977,16 503. 'I8 D. L. Dubois and R. Hofmann Nouueau J. de Chimie 1977 1,479. J. R. Dilworth G.J. Leigh R. L. Richards and K. W.Bagnall suffers from being based upon a hypothetical reaction path which is different from that which has now been shown to be foll~wed."~ The general reactions of the complexes [M(N2)2(dppe)2] [M =Mo or W; dppe = 1,2-bis(diphenylpho~phino)ethane]with alkyl acyl or aroyl halides RX (X = C1 Br or I) to form [M(N2R)X(dppe)2] have been described in some detail.12' These reactions have been shown to involve a predissociation of the bis(dinitrogen) complex and the generation of radicals from the halides as shown in Scheme 1.In Scheme 1 inert solvents R attacks the remaining N2 to form [M(N2R)X(dppe),]."' Where then after protonation a diazobutanol derivative e.g. [MoBr{N2CH(CH2)30H}-formed and a solvent radical produced; in the case cited this is the b(CH2)sCH. radical. This then attacks the dinitrogen yielding first a diazenido-complex and then after protonation a diazobutanol derivative e.g. [MOB~(N~CH(CH~)~OH} (d~pe)~]+.l~l The diazenido-complexes can give rise to amines but only after rather severe treatment.'22 A very unusual reaction of co-ordinated dinitrogen in [Mn(C,HS)(CO),(N2)] has been With phenyl-lithium it generates [Mn(CsHs)(C02{N(Ph)=N}]- which with acid yields [Mn(CSHS)(CO),-{N(Ph)=NH}].These products are not very stable and the suggested structures are somewhat speculative. The conversion of N2 into ammonia has been observed with novel Haber cata- lysts (for example K-lamellar graphite-Fe -Ru or -0s) as well as with N2 complexes. In the graphitic catalyst cited the reactivity for ammonia production correlates with the rate of isotope scrambling in a mixture of 14N2 and 15N2.124 Presumably dissociation of dinitrogen is rate-determining. A much more unusual system with far-reaching implications uses H2 that has been produced by the photolysis of water chemisorbed on iron-doped Ti02.125 The photolysis of water by iron-doped TiO under Ar produces 2 moles of H2 and 1mole of 0,.The same photolysis in the presence of N2 at atmospheric pressure produces O2 in the same amount but the evolution of H2 is completely inhibited. Traces of NH3 and N2H4 were detected and the relevance of these observations to the reaction of N2 has been confirmed by using I5N2. Sunlight was found to be a sufficient activator. Yields of ammonia are still very small (0.2 g of TiO doped with 0.2% Fe,O, when irradiated with mercury light and equilibrated with water vapour produced 0.2 pmol of H2 1.05 pmol of 02,1.39pmol of NH3 and 0.15 pmol of N2H4 after 2 h) but the consumption of HZ by N2 is quantitative.It is assumed that N2H2 J. Chatt R. A. Head G. J. Leigh and C. J. Pickett J.C.S. Chem. Comm. 1977 299. J. Chatt A. A. Diamantis G. A. Heath N. E. Hooper and G. J. Leigh J.C.S. Dalton 1977 688. ''I P. C. Bevan J. Chatt A. A. Diamantis R. A. Head G. A. Heath and G. J. Leigh J.C.S. Dalton 1977 1711. I" P. C. Bevan J. Chatt G. J. Leigh and E. G. Leelamani J. Organometallic Chem. 1977,139 C59. 123 D. Sellmann and W. Weiss Angew. Chem. Internat. Edn. 1977 16,880. lZ4 M. E. Volpin Yu. N. Novikov V. A. Postnikov V. B. Shur B. Bayerl L. Kaden M. Wahren L. M. Dmitrienko R. A. Stukan and A. V. Nefedev 2.anorg. Chem. 1977 428 231. 12' G. N. Schrauzer and D. T. Guth J. Amer. Chem. Soc. 1977 99 7189. Chemistry of the d- and f-BlockMetals 189 is an intermediate in the reduction but direct evidence is as yet lacking.More conventional aqueous fixing systems that have been described during the year include molybdate-cysteine plus reductant'26 and [MoOC~(CNCH,)~]' plus reduc- tant.12' In both these cases the yields of ammonia are small but N2H2 and sideways-bound NZ are claimed to be involved and some supposed parallels with the rather poorly understood enzyme system nitrogenase are drawn. The degradation of complexed N2 to give ammonia has received considerable attention. The conversion of [Mo(N~)~(PM~~P~)~] into [MOC~~(N~H~)(PM~~P~)~] and thence by the action of sulphuric acid into NH3 (0.68 mol per atom of Mo) is believed to involve step-wise protonation of co-ordinated N2 and possibly MoEN or Mo=NH groups as intermediate^.'^^"^^ The compounds [W(N2)2(PMe2Ph)4] and [M(N2)2(PMePh2)4] (M=Mo or W)129 can also be protonated in methanol by sulphuric acid to yield ammonia.For M = W the yields of ammonia approach 2 mol per atom of meta1,13' and methanol is itself a sufficiently strong acid to produce NH3 from N2. The postulated reaction sequence supported in part by the inter- mediates actually isolated is shown in Scheme 2. The implications of this kind of H+ H+ H+ MO-NGN + M-N=NH -+ M=N-NH2 M-NHNH2 H+ H+ MV'+NH3 + M-NH2 + M=NH+NH Scheme 2 process for the functioning of nitrogenase have been presented."' An attempt to adapt this scheme to an electrochemical reduction of N2 by constructing an elec- trode that bears groupings such as (28) failed because direct discharge of protons from the solution is preferred to reduction of N2.I3l n 3 Ety Ph,P ,PPh ,Sn-0-Si-( CH 2)3C N MoN2 E~)J Ph2P' 'PPh, u Alkylimido-complexes are the nitrogen analogues of carbene complexes but are not generally graced with the sophisticated name 'nitrene complexes'.The reaction of Os04with Bu'N=PPh3 gives rise to [Os(NBu)03] and the poly(nitrene) species [Os(NBu),02] and [Os(NBu),O]. These have strong bands in the i.r. spectrum in the range 1160-1200cm-' assigned to i;(Os=N) at a higher frequency than 126 P. R. Robinson E. L. Moorhead B. J. Weathers E. A. Ufkes T. M. Vickrey and G.N. Schrauzer J. Amer. Chem. SOC.,1977,99 3657. 127 E. L. Moorehead B. J. Weathers E. A.Ufkes P. R. Robinson and G. N. Schrauzer J. Amer. Chem. SOC.,1977,99 6089. 128 J. Chatt and R. L. Richards J. Less-Common Metals 1977 54 477. 129 J. Chatt A. J. Pearman and R. L. Richards J.C.S. Dalton 1977 2139. 130 J. Chatt A. J. Pearman and R. L. Richards J.C.S. Dalton 1977 1852. 131 G.J. Leigh and C. J. Pickett J.C.S.Dalton 1977 1797. J. R. Dilworth G.J. Leigh R. L. Richards and K. W.Bagnall bands assigned in other compounds to fi(0s~N). A similar situation has been noted in rhenium cherni~try.'~' Nitrene-(alkylimido-)complexes also arise from reactions of WC16 and organo-nitriles RCN. On the basis of i.r. and 'Hn.m.r. spectra these are believed to have the structure (29).133 They react with donors L such as Et20 THF and SEt2 to yield complexes [WCI,(NCCI,R)L] which have fi(W=N) at ca.1280 4 Dithiocarbamato- and Related Complexes As promised in last year's Report a more detailed account of the recent literature on dithiocarbamate and related 1,l-dithioacid ligands follows. The last compre- hensive account of the topic appeared in 1970,13' but a more recent review details the preparation and properties of dithiocarbamato-complexes with metals in unusual oxidation The iron(II1) dithiocarbamato-(hereafter abbreviated to dtc) complexes [Fe(dtc),] continue to be studied primarily because they exhibit spin-state cross- over between 6A (high-spin) and 'T2 (low-spin) states. When crystallized from benzene or nitrobenzene [Fe(S2CNB~n2)3] occludes solvent and the magnetic moment at room temperature (3.6B.M.) is markedly lower than in the unsolvated complex (5.3 B.M.).The solvent molecules are too well separated from each other and the dtc ligands for interaction but they do affect the average Fe-S distances. These variations of bond length appear to correlate well with the observed moments the highest moments corresponding to the longest Fe-S distances. 13' The analogous Se2CNR2 complexes also show spin-state equilibria which lie more towards the 2T2state. It had previously been reported that the diselenocarbamato- complexes were exclusively low-spin but the observations that led to this conclusion are now attributed to contamination with [Fe(Se2CNR2)2].138 The preparation of the mixed dtc complexes [Fe(S2CNR2)(S2CNR'2)2] has enabled more reliable calculations of ligand-field parameters to be made on the basis of the observed spectroscopic and magnetic properties.139 The iron(II1) dtc complexes [FeX(dt~)~] also have unusual magnetic properties in possessing an S =$ ground state and this has prompted the preparation of new complexes with X = NCO- NCS- NCSe- from [Fe(dtc),] and the appropriate silver ~a1t.l~' The complex with X=CF3C02- was obtained by dissolution of [Fe(dtc),] in trifluoroacetic acid. The complexes with X = C1 can also be prepared 13* A. 0.Chang K. Oshima and K. B. Sharpless J. Amer. Chem. Soc. 1977.99 3420. 133 G. W. A. Fowles D. A. Rice and K. J. Shanton J.C.S. Dalton 1977 1212. 134 G. W. A. Fowles D. A. Rice and K. J. Shanton J.C.S. Dalton 1977 2129.13' D. Coucouvanis Progr. Inorg. Chem. 1970 11,233. J. Willemse J. A. Cras J. J. Steggerda and C. P. Keijpers Structure and Bonding,1976 28 84. 13' E. J. Bukouskas B. S. Deaver and E. Sinn Inorg. Nuclear Chem. Letters 1977,13 282. 13' D. de Fillipo P. Depalano A. Diaz S. Steffe and E. F. Trogin J.C.S.Dalton 1977 1566. 139 C. A. Tsipis C. C. Hadjikostas and G. E. Manoussakis Inorg. Chim. Acta 1977 23 163. 140 E. A. Pasek and D. K. Straub Inorg. Chim. Acta 1977 21,29. Chemistry of the d- and f-Block Metals 191 by irradiation of [Fe(dtc),] in a halogenated solvent. This reaction is free-radical in character and has been studied in detail for dtc = S2CN(CH2Ph)2. It is believed to proceed via excited-state weakening of the bonding of one dtc ligand followed by interaction with the halogenated s01vent.l~~ Analogous irradiation of the ruthenium complex [Ru(S2CNEt2),] in CHCI or CH2C12 at 265 nm produces both [RuC1(S2CNEt2),] and [Ru~(S~CNE~~)~]C~.142 The latter complex can also be prepared by oxidation of [Ru(S2CNEt2),] with dichlorine and its structure was included in last year's Report. If di-iodine is employed as oxidant for [Ru(S2CNMe2),] a complex of stoicheiometry [Ru13(S2CNMe2),] (30) results and an X-ray structure revealed pentagonal-bi- (30) pyramidal [RuI(S~CNM~~)~] units linked into infinite chains by I2 molecules. The central 1-1 distance of 283.4(5)pm is some 13pm longer than in 12 and indi- cative of donor-acceptor interaction with the ligating iodide. 143 The reactions of [Fe(S2CNR2),] with di-iodine give complex mixtures of products in-cluding [Fe12(S2CNR2)2] [Fe(S2CNR2),]13 [R2 =Me2 Et2 or (CH2),] and for R2= Et2 [Fe13(S2CNR2)2].The structure of the [Fe12(S2CNR2)2] complexes may well be analogous to (30) with I2 molecules linking [FeI(S,CNR,),] units.'44 If higher oxidation states of the metal are not readily accessible treatment with dihalogen results in oxidation of the dithiocarbamate ligands. This is illus- trated by the oxidation of [Zn(S2CNBun2),] with di-iodine to give [Zn12(Bun2NCSS2CSNBun2)], containing ligating tetra-n-butylthiuram disulphide. A stopped-flow study of the reaction kinetics suggests that the reaction involves initial formation of the adduct [Zn(S2CNBu"2)2]12; the I2 interacts with a sulphur atom of the dithiocarbamate ligand.',' One of the dtc ligands of [Fe(S2CNEt2),] can also be displaced by neutral molecules L to give [Fe(S2CNEt2)2L2]+ (L = p-ClC6H4NC or iPh2PCH2CH2PPh2).Cyclic voltammetric studies at a platinum electrode show that these can be reversibly reduced to the neutral species [Fe(S2CNEt2)2L2]. The complex [Fe(S2CNEt2)2(p-C1C6H4NC)2] reacts with zinc iodide and the structure of the product which is shown in Figure 1,is such that zinc is bonded to the sulphur atoms 14' P.-H. Lin and J. I. Zink J. Amer. Chem. Soc. 1977 99 2155. 14* K. W. Given B. M. Mattson M. F. McGuiggan G. L. Miessler and L. H. Pignolet J. Amer. Chem. SOC.,1977,99,4855. 143 B. M. Mattson and L. H. Pignolet Inorg. Chem. 1977 16 488. 144 E.A. Pasek and D. K. Straub Znorg. Chim. Actu 1977 21 23. 145 H. Kita K. Tanaka and T. Tanaka Znorg. Chim. Actu 1977 21,229. J. R. Dilworth G. J. Leigh R. L. Richards and K. W.Bagnall Figure 1 The strucfure of [Fe{CN( p-CIC6H4)}~(S2CNEt2)2Zn12] (Reproduced from J.C.S. Dalton 1977 359) of the dithiocarbamate ligand.'46 The complex [Cr(S2CNEt2)3] is isostructural with its iron and ruthenium analogues (discussed above) and it has an average Cr-S distance of 239(6) pm.147 An interesting related complex is prepared by the reac- tion of K2[Cr207] with sodium diethyldithiocarbamate in aqueous solution. The structure shown in Figure 2 was confirmed by X-ray crystallography and provides the first example of insertion of oxygen into a dtc ligand 148 although analogous insertion of sulphur was reported some years A systematic study of the mass spectra of dtc complexes of Cr Fe Co Ru and Rh showed molecular ions for all the complexes,15o but at widely different relative abundances.The major decombosition pathways involve loss of the dithiocarbamate ligand radical and loss of S Sz and SCNRz groups. For the dithiolen-substituted complex [Fe{SzCz(CF3)2}(S2CNRz)z], the dithiolen ligand is lost preferentially to the dtc ligands. A caveat for the mass spectral analysis of dtc complexes is provided by the presence of peaks due to [FeH(dtc)]' and [Fe(dtc),]' in the spectra of even carefully purified Na(dtc). The iron is evidently being chelated from the spectrometer by the dtc ligand. Another physical technique applied to dtc complexes has been U.V.He(1) photoelectron spectroscopy. The tris(dtc) complexes of Cr Fe and Co show distinct bands corresponding to d-orbital ionization and bands in the region 7.5-9.5 eV are believed to arise from orbitals principally derived from sulphur 3p ~rbitals.'~~.~~~ The first reported examples of osmium dtc complexes without tertiary phosphine ligands are provided by the preparation of [OS(S~CNE~~)~] (31)from [NH4]2[OsC16] 146 J. A. McCleverty S. McLuckie N. J. Morrison N. A. Bailey and N. W. Walker J.C.S. Dalron 1977 359. 147 C. L. Raston and A. H. White Ausrral. J. Chem. 1977 30 2091. 148 J. M. Hope R. L. Martin D. Taylor and A. H. White J.C.S. Chem. Comm. 1977 99. 149 D. Coucouvanis and J. P. Fackler J.Amer. Chem. SOC.,1967,89 1346. 150 K. W. Given B. M. Mattson G. L. Miessler and L. H. Pignolet J. Inorg. Nuclear Chem. 1977 39 1309. 151 C. Cauletti and C. Furlani J.C.S. Dalton 1977 1068. 152 C. Cauletti and C. Furlani Inorg. Chim. Am 1977 23 181. Chemistry of the d- and f-Block Metals Figure 2 The molecular structure of [Cr(S2CNEt2)2(02SCNEt2)], showing the ellipsoids of 50% probability (Reproduced from J.C.S. Chem. Comm. 1977 99) and excess Na(dtc). The i.r. spectrum of (31)suggests the presence of a unidentate dtc ligand and on heating under reflux in THF [OS(S~CNE~~)~] (32) is formed. The cyclic voltammetric behaviour of (31) at a platinum electrode is very complex whereas that of (32) is more straightforward showing two oxidation waves and one reduction wave all being reversible.153 Surprisingly the reaction of OsC13,xH20 with Na[S2CNR2] (R=Me or Et) in acetonitrile under reflux gives the p-nitrido- complexes [Os2N(S2CNR2),] in 70% yield. An X-ray crystal structure of the complex (33) showed the presence of both symmetrically bridging nitride and dtc Me Me \I N (33) 153 A. H. Dix J. W. Diesveld and J. G. M. van der Linden Znorg. Chirn. Actu 1977 24 L51. J. R. Dilworth G. J. Leigh R. L. Richards and K. W. Bagnall ligand~.’~~ The bridging dtc ligand imposes a distortion on the 0s-N-0s system to an 0s-N-0s angle of 165(2)”. The 0s-0s separation of 349 pm provides the longest reported span for 1’1-dithiolate ligands. The origin of the nitride nitrogen has not yet been determined but it may arise from the excess dtc present in the preparative reaction.The chemistry of complexes of molybdenum with dtc continues to be an active area the emphasis being on dimeric complexes with a variety of bridging groups. The reaction of [Mo,O,(S,CNEt,)J with thiphenol produces a red-orange diamagnetic complex [Mo,O~(SP~)~(S,CNE~~)~], which has been shown by X-ray crystallography to have structure (34). One SPh group is trans to a terminal 0x0-groups whereas the other is cis and the two Mo-S bridging distances differ by about 20~m.l~~ Trace amounts of water cause (34) to revert to the starting I / Et Et 0x0-complex and halogenated solvents react to give [Mo2(p2-C1)(p2-SPh)2(S2CNEt2)][MoOC14(H20)], the structure of which was discussed in last year’s Report.The asymmetric dinuclear complex shown in Figure 3 is formed on reaction of [MoO~(S,CNE~~)~] with the hydrazines PhCYNHNH (Y = 0 or S) in methanol. The structure shows one molybdenum atom to have distorted square-pyramidal co-ordination with an apical oxygen whereas the geometry about the other is approximately trigonal-prismatic. The dimers undergo a reversible one-electron reduction at a potential about 0.3 V more positive for the derivative with Y = S than that with Y = O.Is6The synthesis of [Mo(S,CNR,)~(CO)~(PP~,),] was report- ed sometime ago’” and now the tungsten analogues have also been ~repared.’~’ Both are derived from the reaction of [MC12(C0)2(PPh3b](M= Mo or W) with excess Na(dtc) an improved synthesis of the tungsten dichlorobis(carbony1) complex also being reported.The ability of dithiocarbamate ligands to stabilize high oxidation states has been attributed to their ability to delocalize positive charge oia the resonance structure Is4 K. W. Given and L. H. Pignolet Znorg. Chem. 1977,16 2982. K. Yamanouchi J. H. Enemark J. W. McDonald and W. E. Newton J. Amer. Chem. Soc. 1977.99 3529. lS6 M. W. Bishop J. Chatt J. R. Dilworth G. Kaufman S. Kim and J. Zubieta J.C.S. Chem. Comm. 1977 70. 15’ R Colton and B. Tomkins Austral. J. Chem. 1970 23 lill. lS8 C. J. Chen R. 0.Yelton and J. W. McDonald Inorg. Chim. Ada 1977 22 249. Chemistry of the d-and f-BlockMetals Figure 3 The structure of [(MO(S~CNE~~)(P~CON~)}~O], which is obtuinedfrorn the reuction of [MoO~(S~CNE~~)~] with PhCONHNH2 (Reproduced from J.C.S.Chern.Cornm. 1977 70) (35). The presence of i.r. bands in the 1500-1600 cm-' region suggests that such structures are important for most dtc complexes. Two apparently independent studie~~~~.'~' of the pyrrolyldithiocarbamate ligand (36) indicate that there is very little contribution of resonance forms such as (35) with C-N multiple bonding R S-\+ / N=C / \s-R because this would require disruption of the aromatic character of the pyrrole ring. Cyclic voltammetric studies of [Fe(S2CNC4H4)3] show that it is easier to reduce and harder to oxidize than its counterparts with other dtc's indicating its enhanced stabilization of lower oxidation states.159 An e.p.r. study of [Cu(S2CNC4H4)2] produced spectral parameters consistent with a very covalent u and w metal-sulphur bond. 160 As the copper atom in copper dithiocarbamate complexes can have oxidation states of 1 2 or 3 and polynuclear derivatives with mixed oxidation states are also known,136 the chemistry in this area is extensive and continues to be studied. can The complex [{CUCI(S~CNE~~))~] be prepared either by the reaction or from of [Cu(S2CNEt2)2] with CUC~~,~H~O'~~anhydrous CuC12 and PhCOS2CNEt2.162 The benzoylated dtc represents a convenient source of anhy-drous dithiocarbamate because the sodium dtc salts are extremely difficult to A. G. El A'rnrna and R. S. Drago Inorg. Chem. 1977,16 2975. I6O R. D. Berernan and D.Nalewajek Inorg. Chem. 1977 16 2687. '" A. R. Hendrickson R. L. Martin and D. Taylor J.C.S. Chem. Comm. 1975 843. ''* C. G. R. Nair and K. K. M. Yusuff J. Znorg. Nuclear Chem. 1977,39 281. 196 J. R. Dilworth G. J. Leigh R. L. Richards and K. W. Bagnall dehydrate. An X-ray structure161 of the dimer shows that in the solid state weak association into tetramers uia intermolecular Cu-S and Cu-Cl interactions occurs. The magnetic properties have been studied from 4.2 to 300 K and inter- preted in terms of an isotropic exchange interaction between each of the four copper An e.p.r. study of the redistribution reaction between and shows [CU(S~CNR~~)~][CU(S~CNR~~)~] that a statistical distribution of products results. However the analogous equilibrium of [Cu(S2CNR2),] and [CU{S~C~(CF~)~}~]~-gives exclusively the mixed product [Cu(S2CNR2)- {S2C2(CF3)2)1-.164 The phosphorodithioate (R2PS2-; R = alkyl aryl or alkoxy) xanthate (ROCS2-) or thioxanthate (Etrithiocarbonate) (RSCS2-) ligands are analogous to dithiocar- bamate.However as in the case of pyrrolyl-dtc they cannot delocalize positive charge by forming exocyclic multiple bonds and they tend to be stronger reducing agents than dithiocarbamates and to stabilize lower oxidation states. 31P n.m.r. spectroscopy has been applied to the determination of the bonding modes (37) (38) (39) and (40) of phosphorodithioate ligands for a range of substituents on phosphorus and for several The observed "P chemical-shift (relative to H3PO4) regions are >107p.p.m.for (39) <82p.p.m. for (40) and 87 and 101 p.p.m. for (39) and (40) which cannot be distinguished. The phosphorus atom is also a potential ligating atom and a structure of (Ni(S,P(chex),)J S S S-M \pH \P' \M \P/ / \s/ /\S-M / \S-M (37) (38) (39) (40) (chex = cyclohexyl) shows P,S-bonded phosphorodithioate ligands. The complex is prepared by direct reaction between the metal halide CS2 [PH(chex),] and base.166 Chelated bis( 1,l-dithioacid) ligands if bound to platinum or palladium are relatively labile and they can be forced into unidentate bonding or displaced altogether by the reaction of the complex with neutral donors such as tertiary phosphines. Prolonged reaction of [Pd(S2PMe2)2]with excess PPh20R (R = Me or Et) in benzene gives [Pd(S2PMe2)(PPh20)(PPh20H)](41) which has been shown by X-ray structure analysis to contain the symmetric hydrogen-bonded Ph2P0-* * H * * * OPPh2 ligand.An analogous complex with dtc can be prepared Ph2 Ph2 (41) 163 P. D. W. Boyd and R. L. Martin J.C.S. Dalton 1977 105. 164 W. Dietzsch J. Reinhold K. Kirmse E. Hoyer and I. N. Marov J. Znorg. Nuclear Chem. 1977 39 1377. C. Glidewell Znorg. Chim. Actu 1977 25 159. 166 E. G. Moers D. H. M. W. Thewissen and J. J. Steggerda J. Znorg. Nuclear Chem. 1977 39 1321. Chemistry of the d- and f-Block Metals and the mechanism is believed to involve attack by displaced 1,l-dithioate ligand on the alkoxy-group of a co-ordinated diphenylphosphinite ligand with the formation of a dithioacid The OR group of co-ordinated xanthate can undergo similar nucleophilic attack as in the reaction of [Pt(S2COR)2] with K[S2COR].Here the product is dependent on R; when R=Me or CHZPh [Pt(S2COR),(S2CO>]- and [Pt(S2CO)2]2- are formed whereas with R =Pr’ or Et [Pt(S2COR),] is the main species generated. The last complex has a structure consisting of two unidentate and one bidentate xanthate ligands as shown in Figure 4,168 whereas the analogous nickel complex on the basis of spectroscopic analysis is believed to contain three bidentate dithioacid ligand~.’~~ Figure 4 The structure of the anion [Pt(S2COEth]-(Reproduced from J.C.S. Dalton 1977,496) 5 Iron-Sulphur Cluster Complexes Much of the research in this area has originated from the laboratory of R.H. Holm and his recent review”’ makes a detailed comparison of the synthetic iron-sulphur clusters with those extant in non-haem iron proteins. This topic was last reported in 1975 and the following describes developments that have been made since then. The iron(II1) complex [Fe(S2-o-xyl)2]- (S2-0-xyl =o-xylyl-a,a-dithiolate) is a viable model for the oxidized rubredoxin (Rd,,) isolated from C. pasteurianum at 167 M. C. Cornock R. 0.Gould C. L. Jones andT. A. Stephenson J.C.S. Dalton 1977,1307. 168 M. C. Cornock R. 0.Gould C. L. Jones J. D. Owen D. F. Steele and T. A. Stephenson J.C.S. Dalton 1977,496. 169 D. Coucouvanis and J. P. Fackler Znorg. Chem. 1967,16,2047. 170 R. H. Holm in ‘Biological Aspects of Inorganic Chemistry’ ed. A. W.Addison W. R. Cullen D. Dolphin and B. R. James John Wiley and Sons New York London Sydney and Ontario 1977 p. 71. 198 J. R. Dilworth G.J. Leigh R. L. Richards and K. W. Bagnall least in terms of spectroscopic and magnetic properties. Although the X-ray structure shows that the iron sites in the synthetic and biological systems are related the Rd, site (42) appears to be more distorted with a very short Fe-S bond. However the structure of the protein is not yet highly refined making precise comparison difficult. The structure of the iron(”) complex [Fe(S2-o-xyl)2]2- has also been determined and shows that the average Fe-S distance increases by about 10 pm on reduction.I7’ Ab initio MO calculations on the hypothetical [Fe(SH)4]- produce the S = and S = 2 ground states found by magnetic measure- ments for the oxidized and reduced forms respectively of r~bredoxin.’~~ The structure of the biological counterpart of (Fe2S2(S2-o-~y1)2]2- has still not been determined but the close resemblance of magnetic and spectroscopic properties indicates that the synthetic cluster is a good model for the two-iron ferredoxins [2Fe-Fd,,] (43).The conditions required for interconversions of FeS, Fe2S2 and Fe4S4 clusters have now been delineated and are summarized in Scheme 3 which illustrates the S2-0-xyl 02 [FeCl4I2-(Fe(S2-o-xyl)21* -[Fe(S2-o-xyl)2]--1 02 v Rdred 3 NaHS. Rdox NaOMe [Fe2S2(S2-o-~y1)2]4-___L [Fe2S2(S2-o-xyl)2]3-[F~~S~(S~-O-XYI)~]~-173 v -1 49v 2 Fe -Fdred 2Fe- Fd, (1)PhSH (II)~MSO-H~O I [Fe4S,(SPh),l4‘-W [Fe4S4(SPh),13-[Fe4S,(SPh),l2--1 75v -1 04 v 4Fe-Fdred 4 Fe -Fd, Scheme 3 systematic build-up of Fe4S4 clusters from tetrachloroferrate(~~).” The equivalent biological systems where they exist are indicated.Mononuclear [Fe(S2-o-xyl)2]- is smoothly converted (in yield) into the dinuclear derivative by treatment with NaHS and NaOMe in methanol. Ligand exchange to the thiophenolate derivative [Fe2S2(SPh),I2-’ is necessary prior to dimerization to the [Fe4S4(SPh),I2- cluster in aqueous DMS0.’73 The (S2-o-xyl)-ligated dimer cannot be converted into the tetramer because the bidentate ligands cannot span the faces of the Fe4S4 cubane structure. The ready interconversion of the three Fe-S cores of the ferredoxins (42) (43) and (44) is illustrated by the reaction of iron(II1) chloride and base in DMSO with the tetracysteinyl peptide AcGlyCys(Gly2Cys),G1y2NH2.The spectrum of the 171 R. W. Lane J. A. hers R. B. Frankel G. C. Papaefthymiou and R. H. Holm. J. Amer. Chem. Soc.. 1977.99.84. R. A. Blair and W. A. Goddard. J. Amer. Chem. SOC.. 1977 99. 3505. ”’ J. Cambray. R. W. Lane A. G. Wedd R. W. Johnson. and R. H. Holm Inorg. Chem. 1977,16,2585. 199 Chemistry of the d -and f -Block Metals initial red-violet solution is very similar to that of [Fe(Sz-o-xyl)zJ- and Rd,,. The colour fades rapidly and the spectrum after 5 min is similar to that of [Ee2S2(S2-o- ~yl),]~-and 2Fe-Fd0,. Subsequent addition of sodium sulphide gives a solution with a spectrum characteristic of the [Fe,S,(SR),]’- clusters and the addition of excess thiophenol gives [Fe4S4(SPh),]’- in a yield corresponding to 48% conversion of the original iron(II1) ~hloride.”~ This represents the first direct synthesis of peptide analogues of the ferredoxins as these were previously prepared by exchange reactions of the pre-formed clusters.175 One of the most useful applications of the work on synthetic clusters is the core-extrusion technique for the identification of iron sites within proteins by treatment of the protein with excess thiophenol in a 4:1 HMPA-HzO medium. Any possibility of dinuclear-tetranuclear conversion during extrusion is suppressed by using a 500 molar excess of thiophenol and an aqueous component of pH b8. The use of this quantitative technique for the hydrogenase from C.pasteurianum suggests the presence of three Fe4S4-type iron sites in the ~r0tein.l~~ The presence of interfering chromophores in proteins such as succinate dehydrogenase will require the development of alternatives to thiophenol as the extrusion agent. In non-aqueous media the redox potentials of the analogue Fe4S4 clusters are substantially more negative than the equivalent ferredoxins. However if the [Fe,S,(SR),]*-clusters are rendered water-soluble by introducing the R groups CH2C00-,‘77 CHzCHzOH or Cys(Ac)NHMe the potentials become very similar to those of the ferredoxins. The effect of solvent medium on the redox properties of the water-soluble clusters has now been studied over the range 80% DMSO-HzO to pure Between these limits the El values (relative to the SCE) for the reduction of [Fe4S4(SR),IZ- to [Fe4S4(SR),I3- range from -1.05 to -0.75 V (R = CHzCHzOH) and -0.91 to -0.73 V [R =Cys(Ac)NHMe].The corresponding couple for the ferredoxin from C.pasteurianum decreases from -0.93 to -0.70 V down to 40% DMSO content whence it remains invariant. At this stage of 40% DMSO the protein becomes re-folded and the Fe sites are shielded from solvent effects. The variations of potential in both are attributed to progressive solvation by water as the content of water is As well as undergoing easy exchange with other thiols the RS-ligands of the Fez& and Fe4S4 cores can be replaced by chloride by reaction with benzoyl ~hloride.~’ The X-ray structures of the products [Fe2SZCl4] (45) and [Fe4S4CI4] G.Christou B. Ridge and H. N. Rydon,J.C.S. Chem. Cornm. 1977 908. 175 B. V. de Pamphilis B. A. Averill T. Herskovitz L. Que and R. H. Holm J. Arner. Chem. Soc. 1974 96 6042. 176 W. 0.Gillum L. E. Mortensen J.-S. Chen and R. H. Holm J. Amer. Chem. Sac. 1977 99 584. 177 H. L. Carrell J. P. Glusker R. Job andT. C. Bruice J. Amer. Chem. Soc. 1’977,99 3683. 178 C. L. Hill J. Renaud R. H. Holm and L. E. Mortensen J. Amer. Chern. Soc. 1977,99 2549. 200 J. R. Dilworth G. J. Leigh R. L. Richards and K. W.Bagnall have been determined and the unequal Fe-Cl distances observed in (45) were attributed to Van der Waals interaction^."^ The first example of an iron-sulphur cluster functioning as a catalyst is in the reaction of EtSH with isocyanides mediated by [Fe,S4(SEt),l4- to give ethylthio-formimidates in essentially quan- titative yields.The postulated mechanism involves the attack of isocyanide at iron followed by migration of SEt from iron to carbon. Reaction with further EtSH liberates the organic product.'" An X-ray structure of [(q5-CsH5),Fe4S4]Br shows that oxidation from the neu- tral species is accompanied by a shortening of two of the four long non-bonding Fe-Fe distances within the cluster from 336 to 319pm the others remaining approximately constant.lgl The effect is attributed to removal of an electron from a cluster antibonding orbital with a subsequent orthorhombic Jahn-Teller dis-tortion. The structure of the dication'" shows that further oxidation produces a geometry with four short Fe-Fe distances of 283.4(3) pm and two of 330.4(5) pm.These structural results have been used as the basis of a qualitative molecular cluster model which rationalizes the observed geometries and predicts a further shortening of the four short Fe-Fe distances of the dication on oxidation to the as yet unisolated trication. Because to date only dianionic [Fe4S4(SR)4]Z-type clus- ters have been structurally characterized it remains to be seen if analogous geometric changes occur on reduction to [Fe,S,(SR),]'- clusters which can be isolated after reduction of the [Fe,S4(SR),JZ- clusters with sodium a~enaphthide.'~' 6 Models for Copper Proteins Among copper-containing biological systems the best characterized are the so-called blue copper which manifest typical intense u.~.bands at about 600 nm (E =5000) and their e.p.r. spectra have small copper hyperfine splitting constants all of 30-100 G. Such copper sites occur in electron-transfer proteins such as plastocyanins and azurin and in conjunction with other copper sites in the blue oxidases such as laccase. Detailed spectroscopic studies of the proteins themselves and investigations of a number of model cornple~es'~~ have led to a wide variety of proposals for the structure of the copper site. There appears to be a consensus of opinion on the presence of RS- originating from a cysteinyl group but other proposed co-ligands include inter alia imidazole methionine sulphur and phenolate. Structure (46) was proposed on the basis of spectroscopic studies of an extensive series of copper complexes of different geometries with various combinations of nitrogen sulphur and oxygen donor ligands.Ig5 It was not reported if the e.p.r.spectra of these models showed the same small hyperfine splittings as the protein. Several model complexes have been able to reproduce U.V. spectral characteristics of the proteins 179 M. 0.Bobrik K. 0.Hodgson and R. H. Holm Inorg. Chem. 1977.16 1851. A. Schwartz and E. E. van Tarnelen J. Amer. Chem. Soc. 1977,99 3189. T. Toan W. P. Fehlhammer and L. F. Dahl J. Amer. Chem. SOC.,1977,99 402. 18* T. Toan B. K. Teo J. A. Ferguson T. J. Meyer and L. F. Dahl J. Amer. Chem. Soc. 1977 99 408. 183 R. W. Lane A. G. Wedd W. 0. Gillum E.J. Loskowski R. H. Holm R. B. Frankel and G. C. Papaefthymiou J. Amer. Chem. SOC., 1977,99 2350. 184 H. Beinert Co-ordination Chem. Rev. 1977 23 119. A. R. Amudsen J. Whelan and B. Bosnich J. Amer. Chem. SOC.,1977 99 6730 and references therein. Chemistry of the d-and f-Block Metals but as in the case of [CU(HB~Z,}(SC~H,~-N~,)~'~~ (pz =pyrazole) they fail simul- taneously to give appropriate e.p.r. parameters. However complex (47),prepared R S/ H L m (47) L=H200r NvNH on the premise that the blue copper site contains imidazole and cysteinyl sulphur shows both an intense U.V. band at about 600 nm and a small all hyperfine splitting constant of 93 G.lS7 The analysis of the amino-acid sequences of azurin and plastocyanin reveals comparable spacings between cysteine histidine and methionine and on this basis a tetrahedral copper ligated by those three amino- acids has been proposed.188 However the absence of any methionine in the sequence of the blue copper protein stellacyanin would appear to rule it out of the copper site.7 Polynuclear Metal-Sulphur Cluster Complexes Copper(1) forms a prolific number of cluster complexes with sulphur ligands and recent studies have confirmed the following stoicheiometries and geometries Cussl2 (Cu cube) cuss6 (Cu trigonal bipyramid) Cu4Ss and cu4s6 (Cu tetra- hedron). The structure of [CU,(SP~)~]~-, shown in Figure 5 is quite different from the cu& type and can be visualized as arising by removal of an SPh moiety from a tetrahedral Cu4(SPh) unit and replacement by a linear (p 2-SPh)-Cu( p2-SPh) unit.Further examples of Cussl2 clusters were reported this year in [C~~(dts)~]~- where dts = (48),and in [Cu8(ded),]"- in which ded = (49).19'Their structures are analogous to that of [C~~(mnt)~]"-(mnt = [S2CNC(CN)2]2-) and comparison with the c&&cluster structure suggests that the Cu-Cu distances in the cubic array are optimal for maximum attractive and minimal repulsive interaction. When co- ordinated the ded type of ligand can undergo protonation at the dithiolate carbon and addition of four equivalents of acid to [C~~(Bu'ded)~]~- where Bu'ded = (49; But in place of Et gives [C~~~(Bu'ded)~(Bu'dedH)~], the first example of an aggregate that contains 10 copper atoms.191 The reaction of CuC12 with tetra- phenyldithioimidodiphosphinate [L (50)] gives the purple mixed-valence complex Cu3L4 which dissociates in solution to Cu13L3 and is oxidized by halogenated lR6 J.S. Thompson T. J. Marks and J. A. Ibers Proc. Nut. Acad. Sci. U.S.A.,1977,74 3114. Y. Sugiura and Y. Hirayama J. Amer. Chem. SOC.,1977 99 1581. G. McLandon and A. E. Martell J. Inorg. Nuclear Chem. 1977.39 191. lS9 I. G.Dance J.C.S. Chem. Comm. 1976 103. 190 F. J. Hollander and D. Coucouvanis J. Amer. Chem. Soc. 1977 99 6268. D. Coucouvanis D. Swenson N. C. Baenziger R. Redelty and M. L. Caffery J. Amer. Chem. SOC. 1977,99,8096. J. R. Dilworth G. J. Leigh R. L. Richards and K. W.Bagnall n Figure 5 The structure of [Cu,(SPh),]’-(Reproduced from J.C.S.Chem. Comm. 1976 103) -S 0 \/ S COZEt c-c \/ II I c=c -S /c-c\o S / ‘CO,Et dts ded solvents toCur4L3. The structure of the last complex was shown by an X-ray structural analysis to belong to the Cu4S6 category and provides the first example of such a structure with a bidentate ligand.19’ The 1,8-dithiolate hexachloronaphtho[ 1,8-cd]- 1,2-dithiole reacts with [Ni(cyclo- octadiene),] in the presence of triphenylphosphine to give complex (5 l) which is a ,Ni -S-1 Ph,P \J 0.Siiman C. P. Huber and M.L. Post Inorg. Chim. Acta 1977 25 Lll. Chemistry of the d -and f-Block Metals rare example of a trinuclear nickel-sulphur ~1uster.l~~ There are few rhenium- sulphur clusters and only the second example of a Re,S cluster is provided by [Re4S4(CN),,l4- prepared by the reaction of [Re(CN),]-with molten KSCN.An X-ray structure of its tetraphenylphosphonium salt showed a cubane-like arrange- ment of the Re,S4 core with three CN groups bound to each Re. The selenium analogue is prepared using a KSeCN melt and is structurally isomorphous. The average Re-Re distances of about 280 pm indicate that there is a high degree of Re-Re bonding.’94 In an attempt to prepare the manganese complex [Mn2( ,u2-s)2(co)8], [Mn2(p-SSnMe3)2(C0)8](52) was oxidized with di-iodine. The analysis and the mass spectrum of the red crystalline product suggested the formula [Mn4S4(CO)15] and the X-ray structure revealed an unexpected linking of three manganese atoms by disulphide as shown in Figure 6.The initial product of oxidation of (52) is MnCO) MnKO) Mn(C0)S Figure 6 The sfrucfure of [Mn4S4(C0)15) (Reproduced from J.C.S. Chem. Comm. 1977,782) probably (53) which relieves the steric strain imposed by its unusual co-ordination at sulphur by dimerization with simultaneous transfer and elimination of co.lg5 193 W. P. Bosman and H. G. M. van der Linden J.C.S. Chem. Comm. 1977 714. M. Laing P. M. Kiernan and W. P. Griffith J.C.S. Chem. Comm. 1977 221. ”’ V. Kiillmer E. Rottinger and H. Vahrenkamp J.C.S. Chem. Comm. 1977 782. J. R. Dilworth G. J. Leigh R. L. Richards and K. W. Bagnall 8 Complexes of Sulphur Dioxide and Related Ligands Sulphur dioxide can either co-ordinate as a Lewis acid in which case the geometry of the M-S02 system is pyramidal or as a cr-donor and r-acceptor the M-SO geometry being planar.Recent structurally confirmed examples of these two co-ordination modes are given by [Pt(S0,),(PPh3)2]'96 (54)(both S02's pyramidal) 19' Rh(q5-C5H5)(q '-C2H4)(S02)] [ calculations on nitrosyl and sulphur dioxide complexes produce similar diagrams for the two formally analogous ligands and permit predictions of the geometry adopted by ligating SO,. Comparisons of tetrahedral SO and NO complexes suggest that SO has a greater tendency to bend owing to the smaller energy separation between the cr* and T* 0rbita1s.l~~ Complex (54) loses SO in toluene solution to form [Pt3(S02)3(PPh3)3] (56) which contains three bridging SO2group the sulphur and phosphorus atoms being nearly coplanar with the triangle of Pt atoms.199 That there is a third mode of bonding for SO2,via sulphur and oxygen has been established with the determination of the structure of [Rh(NO)(SOZ)(PPh3)2] (57).84 Its reactions with 1802 to give a sulphato-complex have been studied and 0 YPh3 0 Ph,P \ /oI Rh Ph3P ,Pt- \s/pt\PPh Ph,P /IN '\o I 0/\ 0 0 (56) (57) the distribution of products that has been established by i.r.spectroscopy could only be rationalized in terms of the unusual square-pyramidal intermediate (58).84 This is in contrast to the oxygenation of [RuC1(NO)(S0,)(PPh3h] with 1802(S-bonded SO,) and the reaction of SO with [IrC1('802)(PPh3)2] where the labelling distribution is consistent with the peroxysulphite intermediate (59).and (55) (SOz planar). Extended Huckel MO 196 D. C. Moody and R. R. Ryan Inorg. Chem. 1976,15 1823. 19' 19' R. R. Ryan P. G. Eller and G. J. Kubas Inorg. Chem. 1976 15,797. R. R. Ryan and P. G. Eller Znorg. Chem. 1976 15 494. 199 D. C. Moody and R. R. Ryan Znorg. Chem. 1977.16 1052. 205 Chemistry of the d- and f-Block Metals 0 \I \ Ru-S / +O 4 "'0-0 ,s-0 /I \o (59) The dependence of the stability and reactivity of co-ordinated SO on other ligands present is illustrated by the series of complexes [Rh(X)(ttp)(SO,)] where X = C1- N3- or CN- and ttp = MeC(CH,PPh,), and [Rh(ttp)L(S02)]' (L = CO PR3 or MeCN). In all the complexes the i.r. spectra suggest pyramidal SOzligands but there is a marked variation in reactivity towards 02,[RhCl(ttp)(S02)] not reacting in solution at 25 "C whereas [Rh(ttp)(MeCN)(SO,)] [AsF,] reacts almost instantaneously."' Co-ordinated SO can undergo nucleophilic attack at sulphur as in the complexes [ML(S020Et)]' [M=Co or Ni L=N(CH2PPh2)3 or P(CH2PPh2)3] prepared by treatment of the hydrated metal salts with L and SO in ethanol.An X-ray structure of the anion (60) of [Ni{N(CH2PPh2)3}(S0,0Et)] [BF,] showed fairly regular trigonal-bipyramidal geometry for the nickel with the S03Et ligand in an apical site.201 When functioning as a Lewis acid SO can attack at sites other than a metal as in the complexes [CU~I~(PP~~M~)~(SO~)]~'~ and [Cu(PMe2Ph),(SPh)(SOz)],zo3where X-ray structures showed the SOz to be attached to bridging iodide and mercaptide sulphur respectively.Both 0-and S-bonding of the thiosulphate ligand in [CO(S~O~)(NH~)~]' have been proposed but an X-ray structure has now shown it to be S-b~nded.~' Reduction of the complex by Cr" is then envisaged as proceeding via attack of Cr" at oxygen. Another reported reaction involving thiosulphate is with [C~(bipy)~]Cl~ which unexpectedly produces a trithionato-complex. An X-ray structure deter- mination revealed an infinite structure (Figure 7) with S3062-ions linking [Cu(bipy),]'+ units.205 An oxosulphur anion is also formed in the reaction of [Pt(O2)(PPh3),] with PhNSO in the presence of 02,PPh3 and moisture. The reaction yields [Pt2(0H)(PPh3),][S,O8] and aniline sulphate the persulphate anion being identified by its characteristic i.r.bands. The dimer is degraded to [Pt(S04)- (PPh3)*] in polar solvents,206 but the mechanisms operative in these and the pre- ceding reaction are far from clear. 2oo P. C. Blum and D. W. Meek fnorg. Chim. Acta 1977,24 675. 201 R. J. Restivo G.Ferguson and R. J. Balahura fnorg. Chem. 1977 16,167. 202 P.G. Eller G. J. Kubas and R. R. Ryan fnorg.Chem. 1977 16,2454. 203 P. G. Eller and G.J. Kubas J. Amer. Chem. Soc. 1977 99 4346. 204 R. J. Restivo G. Ferguson and R. J. Balahura fnorg. Chem. 1977 16,167. *OS M.B. Ferrari G. G. Fava and C. Pelizzi J.C.S. Chem. Comm. 1977 8. *06 C. La Monica and S. Cenini fnorg. Chim. Acta 1977 24 L17. J. R. Dilworth G. J. Leigh R. L. Richards and K. W.Bagnall Figure 7 The structure of [C~(bipy)~(S~O~)~].projected on to the (010)plane. (Reproduced from J.C.S. Chem. Comm. 1977,8) Chemistry of the d-and f-BlockMetals 9 Hydrosulphido-complexes Hydrosulphido-(SH) complexes are few and far between; attempts to synthesize them have frequently led to polymeric sulphide-bridged materials or to binary metal sulphides. One of the earliest prepared was [Cr(SH)(H20)5][S04],'07 and its formulation as a monomer has now been confirmed by solution Raman studies and by the determination of the oxidation state of the metal.2os Oxidation with [Fe(H20)6]3' gives both [(H20)5CrS2Fe(H20)5]3'(61) and [(H20)5CrS2Cr(H20)5]4+ (62) the relative amounts depending on the pH. At acid concentrations >0.1 mol l-' [(H20)5CrS2HFe(H20)514f (63) is the major prod- uct.The further reaction of (61) with [Fe(H20),I2' to give (63) is also found and is surprising in view of the usual resistance of Cr"' to substitution.209 The synthesis of both mono- and bis-hydrosulphido-complexes of rhodium has now been described.210 The macrocyclic rhodium complex (64) undergoes an BF 0' '0 y;,i\J \ /Rh\ / u (641 oxidative addition reaction with one equivalent of H2S to give [RhH(SH)L] (L =macrocyclic ligand). The Rh-H stretching frequency appears in the i.r. as a strong band at 1910cm-' but v(S-H) is too weak to detect. The bis(hydro- su1phido)-complex [Rh(SH),L] (65) was formed by the reaction of [RhC12L] with Na[SGeEt3] in acetonitrile. The presumed intermediate [Rh(SGeEt,),L] under-goes hydrolysis to the final product.210 Complex (65) is surprisingly resistant to aerial oxidation both in the solid state and in solution.These Rh hydrosulphido- complexes may well find use as synthetic intermediates for a range of rhodium- sulphur derivatives. The stability of the above rhodium SH-complexes is attributable to the stability and steric requirements of the macrocyclic ligand and the full utilization of the metal orbitals in bonding preventing degradation by ligand dissociation and the formation of additional metal-sulphur bonds. The quadridentate ligands N(CH2CH2PPh2),(=np,) and P(CH2PPh2) (=pp3) function similarly and permit the preparation of ['M(SH)(pp3)][BPh4] (66) (M = Fe Co or Ni) and [M(SH) (pp3)] (67) (M = Co or Ni) by the reaction of H2Swith hydrated metal salts in DMF in the presence of np or pp3."' Attempts to prepare [Fe(SH)(np,)][BPh,] only gave iron sulphide.In the absence of H2S [M(H2O)LI2' are formed initially and depro- tonated by excess ligand to [M(OH)L]'. The SH complexes are probably formed analogously via [M(H2S)LI2' followed by deprotonation. Complexes (66) and (67) 207 M. Ardon and H. Taube J. Amer. Chem. SOC.,1967 89 3661. 208 T. Ramasami and A. G. Sykes Znorg. Chem. 1976 15 1010. 209 T. Ramasami R. S. Taylor and A. G. Sykes Znorg. Chem. 1977,16 1931. 'lo J. P. Collrnan R. K. Rothrock and R. A. Stark Znorg. Chem. 1977 16 437. 211 M. Di Voira. S. Midollini and L. Sacconi Znorg. Chem. 1977 16 1519. J. R. Dilworth G.J. Leigh R. L. Richards and K. W.Bagnall showed no i.r.bands due to V(S-H) but an X-ray structure of [Ni(SH)(pp3)] [BPh4] confirmed the presence of the SH group.211 The co-ordination of nickel is approximately trigonal bipyramidal with the metal displaced 19.6 pm below the equatorial plane towards the sulphur atom. 10 Photolytic Properties of [Ru(2,2'-bipyridyl),l2' and Related Complexes The photoredox properties of [Ru(bipy),I2' are of high current interest because of the ability of its lowest energy transfer exited state [Ru(bipy),12+* to act as a donor or acceptor of electrons in redox reactions. It is hoped to combine this property with the oxidizing ability of [R~(bipy)~]~+ effect the solar conversion of to water into dihydrogen and dioxygen. Last year [see Annual Reports (A),Vol. 73 19761 monolayer assemblies of the related complexes [Ru(bipy),{4,4'-bis(C02Cl,H,,)-2,2-bipyridyl),] deposited on glass slides were reported to catalyse the photodecomposition of water.212 Unfortunately it appears that the 4',4'- dicarboxy ligand used contained quantities of impurities their concentration and nature not being reproducible but these were essential for the photolytic reaction.Attempts to repeat this reaction in the original213 and other214 laboratories with pure materials were unsuccessful. Nevertheless examination of the quenching of the [Ru(bipy),I2+* complex with a variety of substrates which are themselves excited reduced or oxidized has been actively pursued with the aim of eventually producing a storage system for solar energy that is based on the decomposition of water.Thus [Ru(bipy),12+* is quenched by dioxygen which is converted into its singlet excited The complexes [N4Co( p-02)(p-NH2)CoN4I4+ (N = NH3 or iH2NCH2CH2NH2) quench [Ru(bipy),I2'* and are reduced by one electron which is transferred to the superoxide bridging group rather than to the metal centre.'16 Quenching is rapid by [Fe(H20)6I3+ to give217 [Fe(H2o)6l2+ and by low concentrations of cu" ions in the presence of poly(viny1 sulphate).218 Reductive quenching of [Ru(bipy),I2+* can also occur to give [Ru(bipyX]' which is a reducing agent capable of releasing dihydrogen from water. Thus the photolysis of hydrophobic analogues of [Ru(bipy),I2' in dry acetonitrile has allowed the isolation of [Ru(bipyR),]' (R = various carboxylate s~bstituents).~~~ The complex [Ru(bipy),]+ has been independently prepared and characterized by electrolytic reduction of [Ru(bipy),I2+ in acetonitrile.It was then observed to be generated during the photolysis of [Ru(bipy),I2+in acetonitrile and to produce 02-by interaction with dioxygen in the presence of dimethylaniline.220 Thus in prin-'I2 G. Sprintschnik H. W. Sprintschnik P. P. Kirsh and D. G. Whitten J. Amer. Chem. Soc. 1976 98 2337. '13 G. Sprintschnik H. W. Sprintschnik P. P. Kirsch and D. G. Whitten J. Amer. Chem. Soc. 1977.99 4947. 'I4 S. Valenty and G. L. Gaines J. Amer. Chem. Soc. 1977,99 1285; A. Harrirnan J.C.S. Chem. Comm. 1977 777. *15 J. N. Demas E. W. Harris and R. P. McBride J. Amer. Chem. SOC.,1977,99 3547. 'I6 K. Chandrasekaran and P.Natarajan J.C.S. Chem. Comm. 1977 774. *" R. C. Young R. F. Kasne and T. J. Meyer J. Amer. Chem. SOC.,1977 99 2468. '"D. Meisel and D. S. Matheson J. Amer. Chem. SOC.,1977,99 6577. 'I9 P. J. Delaive J. T. Lee H. W. Sprintschnik H. Abruna T. J. Meyer and D. G. Whitten J. Amer. Chem. SOC.,1977.99 7094. "" C. P. Anderson D. J. Salmon T. J. Meyer and R. C. Young J. Amer. Chem. SOC.,1977,99 1180. Chemistry of the d-and f-Block Metals 209 ciple the component parts of a ruthenium-catalysed photolytic decomposition of water appear to be available but their combination in the required manner has not yet been realized. PART 11 Scandium Yttrium the Lanthanides and the Actinides By K. W. Bagnall A further volume of the Gmelin series covering scandium yttrium lanthanum and the lanthanides has appeared;’ this volume deals with the separation of the ele- ments from each other the preparation of the mctals and their applications as well as the toxicology of the elements.An extensive review of recent advances in the chemistry of the lanthanides in their less common oxidation states has also appeared .2 1 Scandium The structure of ScCl prepared by reaction of metallic scandium with the ScCll.’ phase .or better with ScC13 at 800”C has been determined. This is a sheet structure consisting of close-packed homoatomic layers (Cl-Sc-Sc-Cl along [OOl]) with antiprismatic co-ordination of the metal atoms; the short Sc-Sc distances indicate strong Sc-Sc bonding between the layers and less strong Sc-Sc bonding within the layer.3 The chloride of composition Sc7ClIo is transported to the hot zone when metallic scandium is heated with ScC13 under a temperature gradient (800-900°C); the infinite-chain structure is made up of two parallel chains of scandium octahedra which share a common edge and chlorine atoms cap all outward-facing metal triangular faces bridging to and between isolated Sc”’ ions; the compound can then be described as [(SCC~~~~C~~~~),(SC~C~~C~~~~)~] .In the structure’ of the THF (tetrahydrofuran) solvate of the tetrahydroborate SC(BH,)~,~THF the metal atom co-ordination is trigonal bipyramidal with the three BH groups in the equatorial plane and the two bonded THF molecules occupying axial positions. A structural study6 of the hydroxoacetate SC(HOCH~CO~)~,~H~O has shown that the compound is more correctly formulated as [SC(HOCH~CO~)~(OH~)~]+ [Sc(HOCH,CO),),]-; in both ions the metal atom is eight-co-ordinate in a distorted dodecahedra1 arrangement.2 Yttrium and the Lanthanides Hydrothermal ageing of the gel obtained by treating a lanthanide nitrate with aqueous ammonia (mole ratio 1 2) at pH 7.0 in the mother liquor yields crystalline products; in the erbium compound of composition Er402(OH)8,HN03 the unit ’ ‘Gmelin Handbuch der Anorganischen Chemie’ System-Nr. 39 ‘Seltenerdelemente’ Teil B ‘Die Elemente’ Lief. 2 Springer Verlag Berlin 1976. ’ D. A. Johnson Adv. Inorg. Chem. Radiochem. 1977,20 1. K. P. Poeppelmeier and J. D. Corbett Inorg. Chem. 1977 16 294. K.P. Poeppelmeier and J. D. Corbett ibid. 1977 16 1107. E. B. Lobkovskii S. E. Kravchenko and N. N. Semenenko Zhur. srrukt. Khim. 1977,18,389. A. S. Antsyshkina L. M. Dikareva and M. A. Porai-Koshits Tezisy Doklady Vses. Chugaevskoe Soveshch. Khim. Kompleksn. Soedinenii 12th. 1975 Vol. 2 241 (Chem. Abs. 1977,86 10 871). J. R. Dilworth G.J. Leigh R. L. Richards and K. W.Bagnall cell contains eight erbium atoms (two formula units) two of which are each bonded to nine OH groups in a tricapped trigonal-prismatic arrangement with the metal atom approximately central and the others bonded to five OH groups and two oxygen atoms in a singly capped trigonal-prismatic array with the metal atom displaced towards the cap. The Y Dy Ho Tm Yb and Lu analogues are i~omorphous.~ The previously described HoC12 14 phase has now been structurally identified' as Ho5Clll isostructural with Dy5CI11.The arrangement is best understood as a one-dimensional superstructure of the fluorite type built from five basic fluorite units with four additional anions per unit cell. In order to accommodate the latter half of the primitive cubic anion packing is transformed into closest packing.' In the enneahydrates [M(H20)9X3] [M =Pr or Yb X = Br03or EtSO,] the metal atoms are at the centre of a tricapped trigonal-prismatic arrangement of water 0 atoms with D3,,symmetry in the case of the bromates and C3hsymmetry in the ethyl ~ulphates.~ A number of hydrated lanthanide perrhenates M(Ke04)3,4H20 (M=Ho Er Tm Yb Lu or Y) have been reported and in the ytterbium compound the metal atom is eight-co-ordinate in a distorted tetragonal antiprism bridged by Re04 tetrahedra; the compounds are therefore more correctly written as [Yb2(Re04)6(H20)6],,2nH20.10 In the structure of the oxodiacetato-complex Na3[Ce{O(CH2C02)2}3],2NaC104,-6H20the metal atom in the cerate(Ir1) anion is surrounded by nine carboxylate and ether 0 atoms in a slightly distorted tricapped trigonal-prismatic array," an arrangement found also in the erbate(II1) anion in Er[Er{O(CH2C02)2}3],6H20 ['Er2{0(CH2C02)2}3,6H20']; the other erbium atom is eight-co-ordinate sur-rounded by a distorted square antiprism of 0 atoms made up by four atoms from the outer carboxylate groups of the four nearest erbate(II1) anions together with the 0 atoms of four water molecules.'2 The hydrated NN'-dimethylurea complex [Er{oC(NHMe)2}6(oH2)](C104)3 provides an example of seven-co-ordination for erbium(II1); this is apparently only the second example to be reported the geometry being a deformed pentagonal bipyramid.13 In the 1,%naphthyridine [napy (l)] complex [Pr(napy)6](C104)3 all six ligands are bidentate the twelve atoms forming a distorted icosahedron about the metal atom.14 Complexes with 2,7-dimethyl-1,8-naphthyridine(dmnapy) of composition [M(pd),(dmnapy)] (M = Pr-Yb pd = pentane-2,4-dionate) have been ' H.A. Wolcott W. 0.Milligan and G. W. Beall J. Inorg. Nuclear Chem. 1977,39,59. U. Lochner H. Barnighausen and J. D. Corbett Inorg. Chem. 1977.16 2134. J. Albertsson and I.Elding Acta Crysr. 1977 B33 1460. lo E. D. Bakhareva M. B. Varfolomeev V. P. Mashonkin and V. V. Ilyukhin Koord. Khim. 1976,2 1135. J. Albertsson and I. Elding Acta Chem. Scand. 1977 A31 21. I. Elding Acfa Chem. Scand. 1977 A31 75. M. C.Mattos E. Surcouf and J.-P. Mornon Acta Cryst.,1977 B33 1855. l4 A. Clearfield R. Gopal and R. W. Olsen Inorg. Chem. 1977 16 911. Chemistry of the d- and f-Block Metals 211 reported and dodecahedra1 co-ordination geometry has been suggested for them." A study of the thermal decomposition of the hydrazine complexes of the (n lanthanide oxalates M2(C204)3,4N2H4,nH20 = 2-6 M =Tb Dy Ho or Y) and M2(C204)3,3N2H4,nH20 (n= 2-5 M = Yb or Lu) has appeared.16 The results of this work weie taken to indicate that in the first group the NZH4 molecules occupied seven co-ordination sites whereas in the second group they occupied four sites;16 it would certainly be interesting to have crystallographic confirmation of these conclusions.Structural information for a number of sulphur donor complexes of the lanthanides is now available; in the complex anion of the salt [PPh,] [PI-(S~PM~~)~] the metal atom is co-ordinated to eight S atoms in a distorted tetragonal-antipris- matic arrangement;17 in the complexes [La{SzP(OEt),}3(PPh30)2] and [Sm{SzP(OEt)2}3(PPh30)3] the metal atom in the La complex is eight co-ordinate with square-antiprismatic geometry whereas the samarium complex is cationic [Sm{S2P(OEt)2}2(PPh30)3]+ [SzP(OEt)z]- and the samarium atom is seven-co-ordinate (four S and three 0 atoms) with pentagonal-bipyramidal geometry (four S and one 0 atom in the pentagonal plane)." In the tris-complexes [M{(C6H11)2PS2}3] (M = Pr or Sm) the metal atoms are co-ordinated to six S atoms at the corners of a distorted trigonal prism.'' The electronic spectra of a series of 00'-diethyldithiophosphato (ddtp) complexes [NEt4] [M(ddtp),] (M = La-Eu Tb or Ho) have also been reported.*' 3 The Actinides A spectrophotometric study of the hydrolytic behaviour of Npv" over the pH range 1-14 has shown that between pH 1 and pH 3-4 the neptunium is present as a cation (NpO,') while at pH 4-5 the hydroxide is formed and above pH 5 further hydrolysis to an anionic species occurs.21 It has also been established that oxidation of Npv' to Npv" by ozonized air occurs at pH 8.2 or above.22 Solutions containing s 8 g Np"" 1-' can be obtained by ozone oxidation of Npv' in 2-3 M-KOH and even higher concentrations of Npv" can be achieved by oxidation in 2-3 M-LiOH.23 The oxidation is a diffusion-controlled zero-order reaction and neptunium (also plutonium) is oxidized by the decomposition products of ozone most probably O-.23 The preparation of AmrV,CmrV,and CfIV in solution by oxidation of the tri- positive ions with K2[S208] in the presence of a tungstophosphate (K1~P2W17061) has been reported;24 AmIV was also prepared by electrochemical oxidation in this medium and the Am'V/Aml*' potential at 25 "C in this solution is reported to be l5 M.Ng See H. W. Latz and D. G. Hendricker J.Inorg. Nuclear Chem. 1977 39 71. 16 V. A. Sharov G. V. Bezdenezhnykh E. A. Nikonenko and E. I. Krylov Russ. J. Inorg. Chem. 1977 22 356. " A. A. Pinkerton and D. Schwarzenbach J.C.S. Dalton 1976 2464. l8 A. A. Pinkerton and D. Schwarzenbach J.C.S. Dalton 1976 2466. '9 Y. Meseri A. A. Pinkerton and G. Chapuis J.C.S. Dalton 1977 725. 2o M. Ciampolini and N. Nardi J.C.S. Dalton 1977 2121. 21 V. P. Shilov E. S. Stepanov and N. N. Krot Soviet Radiochem. 1977 19 59. 22 V. P. Shilov E. S. Stepanov and N. N. Krot Souier Radiochern. 1977,19 64. 23 M. P. Mefod'eva N. N. Krot and T. V. Afanas'eva Radiokhimiya 1977 19 245. 24 V. N. Kosyakov G. A. Timofeev E. A. Erin V. I. Andreev V. V. Kopytov and G. A. Simakin Radiokhirniya 1977 19 511. 212 J.R.Dilworth G. J. Leigh R. L. Richards and K. W.Bagnall 1.52k0.01 V. Reduction of AmrV to Am'" in this medium occurs only under radiolysis but CmIV and CfIV are reduced by water.24 The redox behaviour of Am Cm Bk Cf Es and Fm in aqueous media has been investigated by radiopolaro- graphic and radiocoulometric techniques. Electrochemical reduction at a mercury cathode appears to involve Fm" [Fm& +2e-+Hg S Fm(Hg)] whereas for the other actinides it is the tripositive ion which is reduced to the element.*' The Frn:,',)/Fm& potential has been found to be very close to that of the Yb&/Yb& system by means of a cocrystallization technique [254Fm& with SrC12 in the presence of Yb& (not Y2+ as stated)].26 The uranium atom in &UF5 is not seven-co-ordinate as previously believed but eight-co-ordinate the geometry being intermediate between dodecahedra1 and square antiprismatic; the terminal U-F(1) bond length [196(2) pm] is the shortest so far reported for a uranium(V) c~mplex.~' The co-ordination geometry about the uranium atom in U02Br is pentagonal bipyramidal (three 0 and two Br atoms in the equatorial plane) and the structure consists of (U02/203/3Br2/2) layers perpen- dicular to [OlO].The compound is prepared by the thermal decomposition of anhydrous U02Br2 at 650°C in uucuo in a sealed tube.28 The plutonium(v1) oxofluoride PuOF4 has been obtained by the controlled hydrolysis of PuF6 in anhydrous HF both by water and by using the calculated quantity of quartz wool to generate water.Although it is stable at room temperature it disproportionates in anhydrous HF to yield a mixture of PuF6 and Pu02F2 in contrast to UOF and NPOF which are stable in this respect. The compound is isostructural with a-UOF4 and NPOF,.~~ The uranium(v) fluorosulphonate UF2(S03F)3 is obtained by reaction of UF6 with SO in the gas phase or in CFCl3 solution a reaction in which S206F2 is also formed. The compound is stable to 120 "C and its vibrational spectrum indicates that there are two different types of S03F group; two of the groups are probably bridging bidentate and the other may be non-bridging bidentate or unidentate. The two fluorine atoms are terminal.30 Uranium(II1) complexes are uncommon because of the ease of oxidation to uranium(IV) but a number of complexes with A""'-tetramethyldicarboxylic acid amides of the type [UL4][BPh4I3 have now been obtained as precipitates by the addition of an ethanolic solution of Na[BPh,] to a solution of NH4UC14,5H20 and the amide in the same solvent.31 A theoretical treatment of the magnetic behaviour of a variety of six-co-ordinate uranium(1V) complexes of the type [UX4L2](X = C1 or Br L = PR30 or AsR30) of D4, or CZ0symmetry has been published; the calculations fit the experimental results over the temperature range 70-320 K.32 The u.v.-visible spectra of the hexakis(arsine oxide) complex UCl4,6AsMe3O indicate that it is of the form [UC1L6I3' 3C1- like UC14,6PMe30 *' F.David K. Samhoun and R. Guillaumont Rev. Chim. minkrule 1977 14 199. 26 N.B. Mikheev V. I. Spitsyn A. N. Kamenskaya N. A. Konovalova I. A. Rumer L. N. Aueman and A. M. Podorozhnyi Inorg. Nuclear Chem. Letters 1977.13 651. *' R. R. Ryan R. A. Penneman L. B. Asprey and R. T. Paine Acta Cryst. 1976 B32 3311. 28 J.-C. Levet M. Potel and J.-Y. le Marouille Actu Cryst. 1977 B33 2542. 29 R. C. Burns and T. A. O'Donnell Inorg. Nuclear Chem. Letters 1977,13 657. 30 W. W. Wilson C. Naulin and R. Bougon Inorg. Chem. 1977 16 2252. 31 J. I. Bullock and A. E. Storey J.C.S. Chem. Comm. 1977 507. 32 J. W. Gonsalves P. J. Steenkamp and J. G. H. du Preez Inorg. Chim. Acta 1977 21 167. Chemistry of the d-and f-BlockMetals 213 reported last year whereas the corresponding phosphine and arsine oxide XR30 complexes of the bromide and iodide are of the form [UL6I4"4Y- (X=P or As R = Me or Et).The pale (off-white to very pale green) colours of these last are also indicative of a centrosymmetric environment of the uranium atom.33 Three poly- morphs of [UO2(hfpd),{0P(OMe),}] (hfpd = 1,1,1,5,5,5-hexafluoropropane-2,4-dionate) have been detected in the course of thermal studies with this complex34 and the structures of the and p-f~rms~~ have been determined. In both of them the uranium atom adopts seven-co-ordinate pentagonal-bipyramidal geometry but whereas the (hfpd) planes are tilted by 22.5" to the plane of the pentagon in a boat formation in the a-form there is only a slight tilt in the 6-form. A number of papers describing crown ether solvates of uranium compounds have appeared.In crystals of the composition {[U(NCS)4(H20)4],(18-crown-6)1.5,3H20,MeCOBui},neither the crown ether nor the ketone is bonded to the uranium atom which is co-ordinated to four NCS groups via the N atom and to four 0 atoms of water molecules in a square antipri~m.~' Similarly 'Hn.m.r. evidence shows that in the hydrated U02(N03)2 and Th(N03)4 crown ether solvates (15-crown-5 benzo-15-crown-5 18-crown-6 dicyclohexyl-18-crown-6 dibenzo-24-crown-8) the crown ether is outer-~phere.~~ A report of the structure of [(12-~rown-4)UO~(OH~)~](NO~)~, in which the UO group is said to be sur- rounded equatorially by a near-planar hexagon consisting of four 0atoms from the ether and two from the water seems unlikely to be correct. Of the other crown ether species the high melting point 169-172 "C (decomp.) of the 15-crown-5 solvate of UO,(NO,) may indicate a possible bonding intera~tion;~" although the i.r.spectra of a number of hydrated 1 1solvates of U02C12 with various crown ethers are said to be consistent with co-ordination of the ether to the the shift in the C-0-C stretching frequency couId equally well be due to other causes. In the structure of NaU02(HC02),,H20 the metal atom is surrounded by a pentagonal bipyramid of oxygen atoms42 whereas in the neptunium(v) complex BaNp02(MeC02)3 the co-ordination geometry is hexagonal bi~yramidal.~~ Further examples of heteronuclear Schiff-base complexes have been reported in which the d transition-metal ion (Ni" or Cu2') is held in the (N2,02)site and the UOf' ion is held in the (02,02) ~ite.~~.~~ A number of uranium(1V) amido-complex structures have been reported; [U(NPh2)4] is a rare example of four-co-ordinate uranium(IV) the co-ordination 33 J.G. H. du Preez B. J. Gellatly and M. L. Gibson J.C.S. Dalton 1977 1062. 34 J. H. Levy and A. B. Waugh J.C.S. Dalton 1977 1628. 35 J. C. Taylor and A. B. Waugh J.C.S. Dalton 1977 1630. 36 J. C. Taylor and A. B. Waugh J.C.S. Dalton 1977 1636. 37 P. Charpin R. M. Costes G. Folcher P. Plurien A. Navaza and C. de Rango Inorg. Nuclear Chem. Letters 1977 13,341. 38 J. Klimes A. Knochel and G. Rudolph Inorg. Nuclear Chem. Letters 1977. 13,45. 39 N. Armggan Acta Cryst. 1977 B33 2281. 40 D. L. Williams and L. E. Deacon J. Inorg. Nuclear Chem. 1977 39 1079.41 D. L. Tomaja Inorg. Chim. Actu 1977 21 L31. 42 B. F. Mentzen Acta Cryst. 1977 B33 2546. 43 J. H. Burns and C. Musikas Inorg. Chem. 1977,16 1619. 44 D. E. Fenton S. E. Gayda U. Casellato M. Vidali and P. A. Vigato Inorg. Chim. Acta 1977,21 L29. 45 M. Vidali U. Casellato P. A. Vigato L. Doretti and F. Madalosso J. Inorg. Nuclear Chem. 1977 39 1985. J. R. Dilworth G.J. Leigh R. L. Richards and K. W. Bagnall geometry being a highly distorted tetrahedron whereas in [UO{NPhz)3Li(OEt2)]z the uranium atoms in the oxygen-bridged dimer are five-co-ordinate in an approx- imately trigonal-bipyramidal arrangement (three N two 0 atoms). Both compounds are very sensitive to oxygen; the first is prepared by transamination of U(NEtZ) with PhNH2 or by reaction of UCl with LiNPhz in ether while the second is obtained from the filtrate from the latter and evidently results from reaction with air.46 Transamination of the diethylamide with NN’-dimethyldi- aminoethane in pentane yields the trimeric molecule [U3(MeNCHzCH2NMe)6] in which the three U atoms form a linear chain; the central one which is on a centre of symmetry is linked by a triple nitrogen bridge to each of the terminal U atoms and is in an octahedral environment of N atoms.The terminal U atoms are at the centres of distorted trigonal prisms of N atoms the whole presenting a very unusual A closed tetramer [U4(MeNCH2CEizNMe)8] is formed as a minor product of the above reaction; in this the four U atoms are 360pm apart at the corners of a twisted square and each U atom is bonded to six N atoms at the corners of a highly distorted trigonal prism.48 A preliminary communication reports the formation of a black penta-aza-complex UOzL{[2,6-diacetylpyridine-bis-(2’-pyridylhydrazonato)-~~~~~]-dioxouranium(vI) (2)obtained by deprotonating the product of the reaction in ethyl acetate of U02(N03)2,6H20with 2,6-diacetylpyridine-bis-(2’-pyridylhydrazone) by means of 1,8-bis(dimethylarnino)naphthalene (proton sponge).This reacts with anhydrous methanol to yield a polymeric species of composition [H,L(Uo,)2(oMe),(MeoH)I~.49 46 J. G. Reynolds A. Zalkin D. H. Templeton and N. M. Edelstein Znorg. Chem. 1977 16 1090. 47 J. G. Reynolds A. Zalkin D. H. Templeton and N. M. Edelstein Znorg. Chem.1977 16 599. 48 J. G. Reynolds A. Zalkin D. H. Templeton and N. M. Edelstein Znorg. Chem. 1977 16 1858. 49 G. Paolucci and G. Marangoni Znorg. Chim. Acta 1977,24 L5.