22 Organometallic Chemistry of Bi- and Polynuclear Complexes By G. HOGARTH Department of Chemistry University College London London WCl OAJ 1 Introduction This report follows in much the same vein as last year’s contribution. No attempt will be made to present a comprehensive review of the literature since this is documented elsewhere.’ Instead the most significant publications and areas of interest will be highlighted. Special topics covered this year include allenyl complexes compounds in which metal centres are linked together imido complexes and those with related n-donor groups and the metal-mediated synthesis of sulfur-containing macrocycles. 2 Theoretical and Physical Studies In a publication entitled ‘Is there a direct iron-iron bond in [Fe,(CO),]?’ Mealli and coworkers give details of a reinvestigation of this question by means of ab initio calculations.While the situation is quite complicated there appears to be a small direct attraction between the two iron centres which however is hidden by a relatively large effective iron-iron repulsion.2 These results accord with earlier studies which also concluded that the net direct metal-metal interaction is anti-bonding in nature. Fenske-Hall calculations have been used to describe the rhenium-rhenium interac- tions in both high- and low-valent doubly bonded dirhenium complexes. Thus for d2-d2 [(Re(OH),(=CH)),] the electronic configuration is best described as a2n2 while for d6-d6 [{Re(CO),Cp),] 027t4626*27c*2 is an accurate de~cription.~ In somewhat related work ab initio Hartee-Fock calculations on triply bonded [V,(p-dmp),] (dmp = dimethoxyphenyl) reveal that the metal-metal interaction comprises 6-,n- and &components; the electronic configuration is best considered as 02n2d2 and not 02n4as previously ass~rned.~ The bonding in the prototypical high-nuclearity arene clusters [RUs(co),2(c6H6)(,Us-c)]and [RU6(CO) l(c6H6)2(&j-c)] has been investigated using extended Huckel calculations attention being focused on the relationship between the apical ($) and facial (p3)bonding modes of the arene.Most interestingly G. Hogarth ‘Organometallic Chemistry’ Specialist Periodical Reports Vol 23 Chapter 8 p 171. ’J. Reinhold E. Hunstock and C. Mealli New J. Chem. 1994 18 465. T. A. Barckholtz B.E. Bursten G. P. Niccolai and C. P. Casey J. Oryanomet. Chem. 1994,478 153. C.N. Poumbga M. Benard and I. Hyla-Kryspin J. Am. Chem. SOC. 1994 116 8259. 397 398 G. Hogarth the calculations reveal that while the apical isomers are the most stable the local benzene-ruthenium interaction is stronger in the facial isomers.' The effect of temperature on the solid-state structure of [Fe,(CO),,] has been investigated by analysing crystallographic data at 100 160 250 and 300K. As the temperature is decreased the asymmetrically bridging carbonyl ligands become progressively more symmetric the bridged iron-iron vector shortens and at the lowest temperature approximate C, symmetry is observed. These changes are associated with a decrease in atomic motions which allow the atoms within the same molecule to move closer together while the decrease in molecular motion also increases the interpenetration of molecules within the crystal.6 Correlation of geometry with the stretching frequency of metal-bound carbonyls has been attempted for a series of carbonyl clusters.Somewhat surprisingly the positions of the terminal carbonyls are quite independent of cluster geometry. However there is more variation in the lower frequency absorptions associated with the bridging carbonyl~.~ Eisenberg and coworkers have successfully correlated the force constants associated with the metal-metal bond (obtained from Raman spectroscopy) with internuclear separation for a number of binuclear rhodium complexes and have predicted the latter in complexes for which crystallographic data are not available.8 From the results of solid-state NMR spectroscopic studies on tetranuclear [Ru,(,u-H),(CO) ,] it is concluded that either the tetrahedral metal core rotates as a whole or the hydride ligands move over its surface through a series of concerted jumps.' The 70-electron cluster [(1r(,~~-S)Cp},]~ (1)is prepared upon addition of + bis(trimethylsily1)sulfide to [TrCI,Cp*] followed by chromatography on an ion-exchange column.The structure consists of a distorted cubane framework with one short Ir(rv)-Ir(1v) bond (2.764A) four long Ir(Iv)-Ir(III) contacts (av. 3.5 A) and one long Ir(III)-Ir(m) vector (3.683A). Interestingly at higher temperatures all four cyclopentadienyl ligands become equivalent by a fluxional process attributed to the migration of the iridium-iridium bond around the cluster;" the free energy of activation is estimated at 57 kJ mol- Flash photolysis of [{Fe(CO)(p-CO)Cp),] at 98 K in 3-methylpentane initially results in carbonyl loss yielding the triply bridged complex [Fez@-CO),Cp,] .However further irradiation leads to loss of a second carbonyl to afford [{Fe(CO)Cp),] (2) postulated as the first complex to contain an unsupported iron-iron triple bond. In order to understand the nature of the latter in more detail Fenske-Hall calculations have been carried out which support both the proposed C structure and the presence of an iron-iron triple bond." Photolysis of the datively bonded heterobimetallic complex [(CO),(PMe,)Os + W(CO),] results in heterolytic rather than homolytic cleavage of the metal-metal bond.I2 D.Braga P. J. Dyson F. Grepioni B. F.G. Johnson and M. J. Calhorda Inorg. Chem. 1994,33 3218. D. Braga F. Grepconi L. J. Farrugia and B. FG. Johnson J. Chem. SOC.,Dalton Trans. 1994 2911 ' S. F. A. Kettle E. Diana R. Rosetti P. L. Stranghellini R. D. Pergola and L. Garlaschelli Inorg. Chem. Acta. 1994 227 241. ' P.D. Harvey F. Shafiq and R. Eisenberg Inorg. Chem. 1994,33 3424. ' S. Aime R. Gobetto A. Orlandi C.J. Groombridge G.E. Hawkes M.D. Mantle and K.D. Sales Organometallics 1994 13 2375. lo A. Venturelli and T.B. Rauchfuss J. Am. Chem. SOC.,1994 116 4824. F.A. Kvietok and B.E. Bursten J. Am. Chem. SOC.,1994 116,9807. J.L. Male H.B. Davis R.K.Pomeroy and D.R. Tyler J. Am. Chem. SOC.,1994 116 9353. Organometallic Chemistry of Bi- and Polynuclear Complexes 12+ OC\ Fe Fe 3 Multiple Bonds Two publications detail the synthesis and reactivity of quadruply bonded chromium (11) complexes. The chloro-bridged dimer [{ Cr(p-Cl)Cp*},] is an excellent precursor for the synthesis of alkyl and aryl substituted complexes. Thus addition of organolithium reagents affords [(Cr(p-R)Cp*),] (R = Me Et Bu CH,SiMe, or Ph) all of which have a short chromiumshromium contact low magnetic moments and attenuated reactivity properties consistent with the presence of a strong metal-metal bond. Reaction of the diethyl complex with benzene results in carbon-hydrogen bond activation and the formation of the mixed alkyl-aryl compound [Cr,(p-Et)(p-Ph)Cp;].The dimethyl analogue is oxidized to give the non metal-metal bonded 0x0-bridged chromium(v) complex [Cr,Me,(O),(p-O)CpS] while hydrogenation affords the 48-electron cubane cluster [(Cr(p,-H)Cp”)),] (Cp” = C,Me4Et).I3 Girolami and coworkers give details of the preparation of [Cr,(CH,SiMe,),(p- CH,SiMe3),12-(3) which is proposed to have a ‘bent’ chromiumshromium bond (based on the relative geometries of the substituents) bridged by two agostic alkyl moieties.14 The triply bonded dimolybdenum complex [{ Mo(CO),(y5-cyclo-Bu\C,H,P)},] containing 2,5-di-butyl phospholyl ligands has been prepared while reactivity studies reveal that it bears a close likeness to the analogous cyclopentadienyl complex. Chisholm et al.have synthesized a number of unbridged tungsten-tungsten triply bonded complexes containing the di-t-butyl acetylacetenato ligand for example [(WR(0’Pr)(Bu\a~ac)}~] (R = Ph Et).I6 Two publications give details of the synthesis17 and electrochemistry’ of the doubly bonded phosphido-bridged diiron complexes [Fe,(CO),(p-PBu\)(p-PR,)] (R = Ph Cy) and [Fe,(CO),(p-PBu\)(p- PCy,)(p-dppm)] (4). The former show two well-defined one-electron reduction processes and the EPR spectra of the radical anions have been recorded.18 The unsaturated phosphido-bridged diruthenium complex [Ru (p-H)(CO),(PBu\H),(p-PBu:)l is one of the products of the reaction of triruthenium dodecacarbonyl with the secondary phosphine PBu\H. It reacts with carbon monoxide to give the saturated bis(phosphid0) derivative [Ru2(p-H)(CO),(PBu\H)(p-PBu‘,)l a process which is reversed upon addition of more of the l3 R.A. Heintz R. L. Ostrander A. L. Rheingold and K. H. Theopold J. Am. Chem. Soc. 1994 116 11 387. l4 P. M. Morse M. D. Spencer S.R. Wilson and G. S. Girolami Organometalh 1994 13 1646. ‘’ D. Carmichael L. Ricard and F. Mathey J. Chem. SOC.,Chem. Commun. 1994 2459. l6 M.H. Chisholm E. F. Putilina K. Folting and W. E. Streib J. Cluster Sci. 1994 5 67. B. Walther H. Hartung S. Bambirra A. Krug and H.-C. Bottcher Organometnllics 1994 13 172. l8 J.G. M. Van der Linden J. Heck B. Walther and H.-C. Bottcher Inorg. Chem. Acta. 1994 217 29. 400 G. Hoyarth (3) R = SiMe3 I -3 (5) (7) secondary phosphine.” Addition of the Grignard reagent Mg(CH,SiMe,) to [(Ru(p,-Cl)Cp*},] yields a second complex containing a ruthenium-ruthenium double bond namely [Ru,(SiMe,)(p-CH,)(p-Cl)Cpz] (5),the reaction of which with trifluoroacetic acid is temperature dependent.Hence at low temperatures trimethyl- silane is eliminated to yield [Ru2(p-CH2)(p-C1)(p-O2CCF,)Cp~] room (6); at temperature the reaction takes a different course affording [Ru (p-CHSiMe,)(p- Cl)(p-O,CCF,)Cp~] (7) a result of carbon-silicon bond formation.,O Reaction of [(Ru(p,-Cl)Cp*},] with enones and enals results in the formation of unsaturated alkyne-bridged complexes [Ru,(p-CO)(p-RC,R’)Cp;] (R = H R’ = Me Et; R = R’ = Me),,’ while Knox and coworkers have shown that the analogous cyclopentadienyl complexes [Ru,(p-CO)(p-RC,R)Cp,] (R = Ph CF,) are good precursors to cluster complexes.22 With [Ru(C0),(q2-C,H,)] trinuclear results as a mixture of two isomers, [RU~(CO),(~-CO)(~,-CO)(~,-RC~R)C~~] differing in terms of the metal to which the alkyne is n-bound which are interconverted in solution at higher temperatures.Reaction with dicobalt octacarbonyl yields tetranuclear [Ru,Co,(CO),(p3-CO)(p4-PhC2Ph)Cp2]. The doubly bonded dicobalt complex [{Co(CO),L),] (L = C,Me,CH,CH,CH=CH,) reacts readily with the phosphaalkyne PECBu’ to give [CO~(~-CO)(~-~~-~~-~~-PCBU~C(O))L], where car- bon monoxide and the phosphaalkyne are coupled at the binuclear centre., 4 Organic Ligands Addition of diiron nonacarbonyl to the fluorinated ketene (CF,),C=C=O affords the l9 H.-C.Bottcher G. Rheinwald H. Stoeckli-Evans G. Suss-Fink and B. Walther J. Organomet. Chem. 1994,469 163. 2n W. Lin S. R. Wilson and G.S. Girolami Organometallics 1994 13 2309. W. Trakarnpruk A.M. Arif and R.D. Ernst Organometallics 1994 13 2423. 22 K. J. Adams J. J. Barker J. P. H. Charmant C. Canter G. Klatt S. A. R. Knox A. G. Orpen and S. Ruile J. Chem. SOC. Dalton Trans. 1994 477. 23 R. M. Matos J. F. Nixon and J. Okuda Inorg. Chem. Acta. 1994 222 13. Organometallic Chemistry of Bi- and Polynuclear Complexes 401 alkylidene complex [Fe,(CO),{ p-C(CF3),}] which contains only terminal carbonyl ligands as does the PPh substituted derivative., Chaudret and coworkers have prepared the highly reactive mononuclear fragment [RuCp*] in situ via the addition of CF,SO,H to [(Ru(p-OMe)Cp*},].It reacts with the solvent in which it is generated. Thus in dichloromethane methylidyne clusters [Ru3(p-C13)(p3-CH)Cpj] and + [R~,(p-Cl),(p-C0)(p~-CH)Cpj]~ + result while in chlorocyclohexane the chloroal- kylidyne derivative of the latter is formed.,’ A further methylidyne cluster [Mo,(CO),(p,-CH)Cp,] results from the photochemically induced reduction of one of the carbonyls in [{Mo(CO),Cp},] upon reaction with the silane SiHMe,Ph.26 Reactions of the ethylene-bridged diosmium complex [Os,(CO),(p-C,H,)] with activated alkynes results in cycloreversion affording dimetallacyclobutenes [Os (CO) (p-RC=CR)] . ’ Addition of bis (diet hy1amino)acetylene to [(M(CO),Cp},] (M = Mo W) at high temperatures leads to the formation of the alkyne complexes [M,(CO),(p-RC2R)Cp,] (R = NEt,) (8).Crystallographic data reveal however that rather than the anticipated dimetallatetrahedrane-type struc-ture the complexes contain the unexpected 1,2-dimetallacyclodicarbeneunit as the central core., Rauchfuss and coworkers have reported details of the photochemical reaction of [Fe,(CO),(p-S,)] with buckminsterfullerene; FAB mass spectrometry shows a range of products C6o[Fe,(Co)6(p-s,)] (n = 1-6) in which the disulfur units link the diiron centre to the carbon frame~ork.,~ Photolysis of the alkylidene complex [Fe,(CO),(p-CO)(p-CHBu)Cp,] results in dehydrogenation affording the vinyl alkylidene [Fe,(CO)(p-CO)(p-HCCH=CHEt)Cp,] in which the carbon-carbon double bond is metal bound;30 reaction of allylbromide with [R~,(CO),~(p-dppm)] affords [Ru2(C0),(p-C3HS)(p-Br)(p-dppm)] as a result of oxidative addition of the carbon-bromine bond to the metal centre.31 P The cyclopropenyl complex [Ru3(p3-CO)(p3-cycEo-C3H,Me)Cp~] (9) is isolated from the reaction of [{Ru(p3-Cl)Cp*},] with trans-3-methyl-2-butenal.Crystallo-graphic studies reveal that the cyclopropenyl ligand sits on a face of the trimetallic 24 M. Wiederhold and U. Behrens J. Organornet Chem. 1994 476 101. 25 D. Rondon J. Delbeau X.-D. He S. Sabo-Etienne and B. Chaudret J. Chern. SOC. Dalton Trans. 1994 1895. 26 M. Akita K. Noda and Y. Moro-oka Organometallics 1994 13 4145. M. R. Burke F. Seils and J. Takats Organometallics 1994 13 1445. 28 J. Heck K.-A.Kriebisch W. Massa and S. Wocadlo J. Organornet. Chern. 1994 482 81. 29 M. D. Westmeyer C. P. Galloway and T. B. Rauchfuss Inorg. Chem. 1994 33 4615. ’O C. P. Casey and G. P. Niccolai Organornetallics 1994 13 2527. ’’ M. I. Bruce P. A. Humphrey R. J. Surynt and E. R.T. Tiekink Aust. J. Chem. 1994 47 477. 402 G. Hogarth centre adopting a relative staggered arrangement.,' Protonation of fulvalene-bridged alkyne complexes [Mo,(CO),(p-RC,CR,OMe)(p-Fv)] (Fv = H,CSCsH,) results in loss of methanol and the formation of stable fluxional carbenium complexes [Mo2(CO),(p-q2,q3-RC=CCR',)(p-Fv)] + .32 In a similar manner the metal-stabil- ized dicarbenium ions [Mo,(CO),(~-H,CC=CH,)C~,]~ + (10) and [Co,(CO),(p- dppm),(p-H,CC-CCH,)]2 result from the addition of two equivalents of tetraf- + luoroboric acid to the respective dipropargylalcohol c~mplexes.~~~~~ H2C' \ /CH2+ Molecular orbital calculations on the crystallographically characterized dimolyb- denum complex reveal that the positive charge is transferred to the metal centre; both complexes undergo double addition of donor ligands such as amines phosphines thiols and pyridine to the methylene centres.Addition of cyclopentadiene to the triruthenium hydride [RU~(,U-H)~(~~-H),C~:] leads to the formation of the metalla- cyclopentadiene complex [Ru,(~~-CM~=CHCH=CH)(~-H)~C~:] as a result of an unprecedented C(sp2)-C(sp3) bond cleavage of the cyclic diene.3s Heating [{IrH,Cp*),] in neat thiophene results in a double sulfur-carbon bond cleavage reaction and the formation of [Ir,(p-S)(p-H,C=CHCH=CH,)Cp?], the extruded sulfur being captured by the metal centre.When the reaction was carried out using thiophene-d4 a ,H product was formed with deuterium scrambled over all positions of the bridging butadiene ligand. The latter can easily be removed upon carbonylation giving [Ir,(CO),(p-S)Cp;]. However the sulfur is firmly bound to the binuclear centre.36 Demetallation of trinuclear [Ru3(CO),(p3-C,,H,,)] by Me3N0 affords the binuclear paracyclophane complex [RU,(C0)6(p-r3,r3-C,,H16)] the organic ligand being bound to the metal centre by two enyl interaction^.^' Johnson and coworkers also report that abstraction of H- from the cyclohexadienyl ligand in [OS,(CO)&~- q5-cyclo-C6H6Ph)]-(1 1) by [CPh,][BF,] affords carbene [oS3(co)9(~3-r',~2,~2- C6H5Ph)] (12) and ketone [OS3(CO)9(p3-q1,q2,r2-0=CC6HsPh)] (13) complexes; the latter is probably formed via carbonyl coupling with the carbene ligand in the former.38 Two independent groups give details of the reaction of 1,2,4,5-tetrabromodurene 32 H.El Amouri Y. Besace J. Vaissermann G. Jaouen and M. J. McGlinchey Organometallics 1994 13 4426. 33 M. D. McClain M. S. Hay M. D. Curtis and J. W. Kampf Organometallics 1994 13 4377. 34 S.C. Bennett M.A. Phipps and M.J. Went J. Chem. SOC. Chem. Commun. 1994 225. 35 H. Suzuki Y. Takaya T. Takemori and M. Tanaka J. Am. Chem. Soc. 1994 116 10779. 36 W.D. Jones and R. M. Chin J. Am. Chem. SOC. 1994 116 198. 31 A. J. Blake P. J. Dyson B. F.G.Johnson and C. M. Martin J. Chem. Soc. Chem. Commun. 1994 1471. 3R A. J. Edwards M. A. Gallop B. F. G. Johnson J. U. Kohler J. Lewis and P. R. Raithby Angew. Chem. Int. Ed. Engl. 1994 33 1093. Organometallic Chemistry of Bi-and Polynuclear Complexes with [Fe2(Co),12-and [Fe,(CO),] .39940 In the first instance formation of [{Fe,(CO),},{p-(CH,)4C6H2)] (14) is postulated in which diiron centres are linked via o-interactions with the methylene groups on the aryl ring. In the second a quite different product [Fe3(C0)9{p-(CH,)4C6H2]] (15) results; a diiron hexacarbonyl fragment is linked in a bis(ally1) fashion and an iron tricarbonyl moiety is bound in an exocyclic diene-type manner. Ph G Ph + (14) (15) 5 Allenyl Complexes The chemistry of the allenyl ligand when bound to bi- and trinuclear centres has been the focus of four publications in 1994.Carty and coworkers report that the diruthenium and diosmium allenyl complexes [M,(Co),(p-PhC=C=CH,)(p-PPh,)] formed from the selective attack of diazomethane at the a-carbon of the acetylide complexes [M,(Co),(p-C~CPh)(p-PPh,)] are in fact bound to the second metal centre via the C,-C double bond and not C,-C as previously Addition CNBu' to the ruthenium complex (16) results in regiospecific attack at C yielding [Ru,(CO),{p- q1,~'-P~C=C(CNBU')CH,](~-PP~,)],~~ while thermolysis in the presence of dppm affords [R~,(CO)~{p-q~,r~,yl~,r~-Ph~PC(O)C(Ph)CCH~}(p-dppm)] (17) a result of coupling of the allenyl fragment carbon monoxide and the phosphido m~iety.~' Wojcicki and coworkers give details of the synthesis of trinuclear allenyl complexes from the mononuclear precursor [Ru(CO),(CH,C=CPh)Cp].Reaction with tri- ruthenium dodecacarbonyl then affords [Ru3(C0),(p3-q1 ,q2,q2-PhC=C=CH,)Cp] while with iron carbonyls analogous mixed iron-ruthenium complexes are pre- 39 F. R. Alam K. A. Azam S.E. Kabir and S.S. Ullah Indian J. Chem. Sect. A 1994 33,420. 40 L. Girard A. Decken A. Blecking and M.J. McGlinchey J. Am. Chem. SOC.,1994 116 6427. 41 N. Carleton,J. F. Corrigan S. Doherty R. Pixner Y. Sun N. J. Taylor and A. J. Carty Organometdics 1994,13,4179. 42 S. M. Breckenridge,A. J. Carty M. A. Pellinghelli,A. Tiripicchio and E. Sappa,J. Organomet. Chem. 1994 471 211. 404 G. Hogarth pared.43 In a somewhat different approach the triosmium allenyl complex [Os (CO),(p-H)(p,-Me,SiC=C=CH,)I is prepared upon thermolysis of [Os,(CO),(p-CO)(p,-Me,SiC2Me)] proton loss from the methyl group of the alkyne affording the new allenyl ligand., 6 Metal-mediated Transformations of Organic Ligands Several interesting isomerizations of organic ligands have been reported.The flyover carbene complex [Co2(p-q3,q2-C3H3CH=CHMe)Cp2] (18) rearranges to [Co2(p- q3,q2-MeC3H2CH=CH2)Cp2] (19) via a metal-mediated 1,5-hydrogen shift,45 while the kinetic product of the addition of [co2(co)g] to [MoCl(q2-MeC=CPh),Cp] namely [MoCo(CO),(p-PhC=CMeCPh=CMe)Cp] rearranges to the ther-modynamically more stable isomer [MoCo(CO),(p-MeC=CPhCPh=CMe)Cp] upon therm~lysis.~~ Insertion of dimethylacetylene dicarboxylate into [Fe,(CO),(p-H)(p-CO)(p-PPh,)(p-dppm)] affords the cis product [Fe,(CO),(p-RC=CRH)(p-PPh)(p-dppm)] (20)(R = C0,Me).This rearranges to the trans isomer (21) upon photolysis a process which is reversed when left at room temperature. Interestingly thermolysis of either isomer results in the irreversible formation of a third metallacyclic isomer [Fe2(CO),(q2-RC=CHC(OMe)=O)(p-PPh2)(p-dppm)] (22) which also has a trans arrangement of substituents on the vinyl moiety.47 Stoichiometric alkyne metathesis has been achieved at a tetranuclear centre. Thus heating the alkyne-alkylidyne complex [Os3W(CO),,(p3-CMe)(p3-tolC=CMe)Cp] (to1 = p-MeC,H,) affords the dimetallaallyl complex [Os,W(CO),(p,-tol-CCMeCMe)Cp] as a result of carbon-carbon bond formation.However loss of a second carbonyl gives the new alkyne-alkylidyne complex [Os3W(CO)g(p3-Ctol)(p3- MeC=CMe)Cp].48 Closely related to the latter thermolysis of [Os,W(CO),,(p,- tolCCtolCto1)Cpl at 50 "C also results in carbonsarbon bond cleavage to afford the butterfly cluster [Os W(CO),(p,-Ctol)(p,-tolC=Ctol)Cp] (23). At slightly higher temperatures (55 "C),however a second very slow cleavage reaction occurs to give the tris(alky1idyne) complex [Os,W(CO)g(p,-Ctol)3cp] (24) which again has a butterfly 43 C. E. Shuchart A. Wojcicki M. Calligaris P. Faleschini and G. Nardin Organometallics 1994 13 1999. 44 A. A. Koridze N. M. Astakhova P.V. Petrovskii F. M. Dolgushin A. I. Yanovsky and Yu. T. Struchkov J. Organomet.Chem. 1994 481 247. 45 J. A. King Jr. and K. P. C. Vollhardt J. Organomet. Chem. 1994 470 207. 46 W. Hirpo M. D. Curtis and J. W. Karnpf Organometallics 1994 13 3360. 47 G. Hogarth and M.H. Lavender J. Chem. SOC.,Dalton Trans. 1994 3389. 48 M.T. Kuo D.-K. Hwang C.-S. Lin Y. Chi S.-M. Peng and G.-H. Lee Organometallics 1994,13,2142. Organometallic Chemistry of Bi-and Polynuclear Complexes H H H R To1 structure; two alkylidyne ligands cap triangular faces while the third bridges wing-tip osmium atoms and a tungsten in a hinge site.49 Loss of carbon monoxide from the mononuclear cyclopropenyl complex [Ir(CO),(q3-C,Bu\)] initially gives [Ir,(CO),(q3-C3Bu~),(p-CO)].Loss of another carbonyl results in formation of [Ir,(CO),(~2-C3Bu\)(p-q2,~3-C3Bu\)], in which both rings are ruptured.Quite remarkably however carbonylation of the latter results in reformation of the mononuclear tricarbonyl complex.50 One-electron oxidation of [Mo,(p-C,Me,)Cp,] gives the radical cation which on the basis of geometric changes upon electron loss is postulated to contain a three-electron metal-alkene interaction. Upon further oxidation proton loss gives [Mo,(p-C,Me,CH,)Cp,] which contains + a molybdenum-molybdenum double bond. 51 A number of interesting carbon-carbon bond formation processes has been 49 J. T. Park B. W. Woo J.-H. Chung S.C. Shim J.-H. Lee S.4. Lim and I.-H. Suh Organometallics 1994 13 3384. 50 R. P. Hughes D. S. Tucker and A. L. Rheingold Organometallics 1994 13 4664. 51 N.G. Connelly B.Metz and A.G. Orpen J. Chem. Soc. Chem. Commun. 1994 2109. 406 G. Hogarth reported. Reaction of ethoxyacetylene EtOC-CH with [Fe,(CO),(p-CO)(p-SR)] -affords the vinyl carbene complexes [Fe2(Co),(p-EtCo=CHc(Co2R'))(p-SR)] (25) (R' = Me Ph) after quenching with benzoyl or acetyl chloride.' Allene couples readily to carbon monoxide and to itself at the diiron centre. Hence photolysis of [Fe,(CO),(p-CO)(p-dppm)] and allene affords [Fe,(CO),(p-H,CCCH,)(p-dppm)l 7 [Fe2(C0)5 {p-c(0)c(cH2)2} (p-dppm)l (26) and [1Fe2(C0)4(p-(H,C),CC(CH,),}(p-dppm)] ;in the reaction with [Fe,(CO),(p-PPh,)(p-CH,PPh,)] it couples with the phosphido bridge to give [Fe,(CO),(p-Ph,PC(CH,),}(p-CH,PPh,)] (27).53 Protonation of the unsaturated vinylidene complex [Re,(CO),{p-C=CHC(Me)=CH,}Cp,] (28) affords the alkylidyne compound [Re,(CO),(p- CCH=CMe2)Cp2]+ which in turn reacts with methyllithium to yield the new saturated vinylidene [Re,(CO),(p-C=CHBu')Cp,] resulting from regioselective attack at the y-~arbon.~ The nature of the reaction of primary alkynes with [Ru,(p-Cl)(p-SPr'),Cp,*l'is strongly dependent upon the substituent.Thus with HCrCCR,OH water is lost to afford [Ru,(=C=C=CR,)(p-Cl)(p-SPr'),Cp~]* while with phenyl ethyne coupling occurs to give the carbene complex [Ru2(p- SP~'),(~-P~C=C(C~C~O-~,~~~~,)C)C~~] + (29) during which a proton is transferr- ed from a phenyl ring to the carbon it is bound to." Both carbonyl and isonitrile insertion into a (r-TCvinyl ligand is observed at a triruthenium centre.Thus reaction of [Ru,(CO),(p-CO),(p-PhC=CHPh)(p,-PhNR)](R = C,H,N) with PPh and PhCH,NEC affords [Ru3(CO),(PPh3),(p-0=CPhC=CHPh)(p3-PhNR)]and [Ru3(C0),(p-CO),{p-(PhCH2)N=CPhC=CHPh)),-PhNR)] re~pectively.~~ The coupling of both phospha- and arsabenzenes has been achieved at the triosmium centre. Reaction of [Os,(p-H),(CO),,] with the 2-trimethylsilyl substituted rings initially affords [Os,(p-H),(CO),(p,-ql ,q2-cyclo-EC,H,R)] (30) (E = P As; R = SiMe,) while further reaction results in a [4 + 21 Diels-Alder coupling of the rings yielding [Os3(p-H)(C0)9(p-q',~2-E,C,,H7R,)] (31).57 7 Linking Metal Centres A large number of publications has appeared this year concerning the synthesis and 52 D. Seyferth J. B. Hoke J. C. Dewan P. Hofmann and M. Schellbach Organometallics 1994 13 3452.53 S. A. R. Knox D. A.V. Morton A.G. Orpen and M. L. Turner Inorg. Chim. Acta. 1994 220 201. 54 C. P. Casey Y. Ha and D. R. Powell J. Am. Chem. SOC. 1994 116 3424. " H. Matauzaka Y. Takagi and M. Hidai Organometallics 1994 13 13. 56 P. Nombel N. Lugan F. Mulla and G. Lavigne Organometallics 1994 13 4673. '' A. J. Arce A. J. Deeming Y. De Sanctis A. M. Garcia J. Manzur and E. Spodine Organometallics 1994 13 3381. Organometallic Chemistry of Bi-and Polynuclear Complexes 407 properties of compounds in which metal centres (not directly bonded to one another) are linked by bidentate ligands. Such ligands may or may not be unsaturated the former potentially allowing strong communication between the metal centres.The electroactive ligand dppf has been used to link triiron-bis(su1fido) and tricobalt- ethylidyne centres in [{ Fe3(co)8(p3-S)2) ,(p-dppf)] 58359 and [{ c03(c0)8(p3-CMe)} (p-dppf)I6' respectively; a moderate electronic interaction has been found in the latter. Diphosphines with saturated backbones have been used to link Fe3Au fragments reaction of [Fe,(CO) ,I2-with [Au,Cl,(p-L-L)] (L-L = dppm dppe) affording [{Fe,Au(CO) i}2(p-L-L)]2- ;the diphosphine links the butterfly clusters through coordination to the wing-tip gold centres.61 Somewhat related is the complex [{Fe,(CO),(p,-PMe)} 2(p3,p3-PA~P)] (32) in -which a gold atom links the two triiron centres via coordination to the capping phosphide moieties.62 Tricobalt centres have also been linked by alkylidyne groups.Thus both [{c03(CO),} 2(p3,P3-CCH=CHC)I and C(c03 (CO) } 2 (p37P3-CC6H4C)I (33 )60 have been prepared the latter showing strong communication between the metal centres via the aryl ring. Related to these is [{CO,(CO),}~(~~,~,-CS~M~~OS~M~,C)] where the link consists of a siloxane moiety.64 Shriver and coworkers have reported a very novel example in which triiron centres are linked by a C ligand. Reaction of the ketenylidene complex [Fe3(CO),(p3- C=C=0)l2 -with triflic anhydride yields [{Fe3(CO),)2(p,,p,-C~CC~C)]2-, the 58 Z.-G. Fang Y.S. Wen K. L. R. Wong S.-C. Ng L.K. Liu and T.S.A. Hor J. Cluster Sci. 1994,5 327. 59 Z.-G. Fang P. M. N. Low S.-C. Ng and T. S. A. Hor J. Organomet. Chem. 1994,483 17. S. Onaka M. Otsuka A. Mizuno S.Takugi K. Sako and M. Otomo Chem. Lett. 1994 45. 61 0.Rossell M. Seco R. Riena M. Font-Bardia and X. Solans Organometallics 1994 13 2127. 62 M.T. Bautista P.S. White and C.K. Schauer J. Am. Chem. SOC. 1994 116 2143. 63 M. Akita M. Terada N. Ishii H. Hirakawa and Y. Moro-oka J. Organomet. Chem. 1994 473 175. 64 J. Borgdorff N. W. Duffy B.H. Robinson and J. Simpson Inorg. Chim. Acta. 1994 224 73. 408 G. Hogarth (32) Fe = Fe(C0)3 (33) co = Co(C0)3 2+ (34) (35) tetracarbon unit consisting of two linked acetylide moieties being formed by oxygen ab~traction.~’ Binuclear centres carrying alkyne ligands have been linked by the substituent on the alkyne. Reaction of [Co,(CO),] with Me,SiC-CSiMe,H affords the siloxane- bridged complex [{C~,(CO)~(p-Me,SiC~)}~(p-Me~Si-~-si~e,)],~~ which has been crystallographically characterized while reduction of alkyne complexes [Mo~(C~)~(~-HC~CCH=CHR)C~,] (R = H Me) by sodium amalgam affords [(Mo~(CO),(~-HC,)},(~-CH~CHRCHRCH~)] as a result of carbon-carbon bond f~rmation.~~ While the last two examples may be considered as diyne complexes novel tetrayne dicobalt complexes [{ Co,(CO),(p-dppm)(p-RC,)} ,(p-C_CC=C)] can be synthesized by oxidative coupling of [Co (CO),(p-dppm)(p-RC,C~CH)] or by .* lithiation and subsequent coupling of [Co (CO ), (p-dppm)(p-RC,CH=CHCl)] Other symmetrically coupled products include [{ Rh,(p-CH2)2Cp~},(p-S,)]2 (34) + in which the dirhodium centres are linked by a rectangular S unit69 and [(Fe2(CO),(p-CO)Cp,}2{p-C=N(CH,),N=C}] (n = 2,3) which act as bidentate chelating agents via the nitrogen atoms towards a range of Lewis acidic metal halides.70 In [{Co,(CO) ,}{p-Al(thf),} {Co,(CO) 0]] tri- and tetracobalt moieties are linked by a quasi-octahedral aluminium centre being bound through the oxygens of triply bridging ~arbonyls;~~ in [{Rh,(p-RC=CHR)Cp,},(p-cyclo-C,H,Me)] (35) 6s D.M. Norton C. L. Stern and D.F. Shriver Inorg. Chem. 1994 33 2701. 66 R. Ruffolo A. Decken L. Girard H. K. Gupta M. A. Brook and M. J. McGlinchey Organometallics 1994 13 4328. h7 J. F. Capon S. Cornen N. Le Berre-Cosquer R. Pichon R. Kergoat and P. L’Haridon J. Organomet. Chem. 1994 470 137. 68 J. Lewis M. S. Khan M. R. A. Al-Mandhary and P. R. Raithby J. Organomet. Chem. 1994 484 161.6y K. Isobe Y. Ozawa A. Vazquezde de Miguel T.-W. Zhu K.-M. Zao T. Nishioka T. Ogura and T. Kitagawa Angew. Chem. Int. Ed. Engl. 1994 33 1882. ’O S. Schroelkamp W. Sperber D. Lentz and W. P. Fehlhammer Chem. Ber. 1994 127 621. ’’ J. J. Schneider U. Denninger and C. Kriiger 2.Nuturforsch. TeiI B. Chern. Sci. 1994 49 1549. Organometallic Chemistry of Bi- and Polynuclear Complexes 409 (R = CF,) equivalent dirhodium centres are linked by the asymmetric pentadienyl ligand both being bound in a 0-.n vinyl fashion.72 8 0x0 and Imido Complexes A whole range of bi- and trinuclear imido complexes has been prepared by simple metathesis reactions of chloroimido complexes such as [MCl,(NR),] (M = Mo W),73,74 [MCl,(NR)Cp] (M = Nb Ta),73 [NbCl(NR)Cp,],73 and [ReCI(NR),]74 with the carbonyl anions [M(CO),Cp]-(M = Mo W) [Fe(CO),Cp]- [Mn(CO),] - and [Co(CO),] -.For example addition of [Mo(CO),Cp] to [ReCl(NBu') affords binuclear [(NBU'),R~MO(CO),C~],~~ while reaction of two equivalents of the same anion with [MoCl,(NBu'),] gives trinuclear [Cp(CO),MoMo(NBu'),Mo(CO),Cp].74 The same workers also report that one- electron reduction of [MCl,(NBu')Cp] (M = Nb Ta) or [NbCl(NBu')Cp,] affords spin-spin coupled d'-d' imido-bridged binuclear complexes [{ MCl(p-NBu')Cp) ,] and [(Nb(p-NBu')Cp,} 2] respectively.7 While the bis(su1fido) complex [{ Mo(NBu')(p-S)Cp},] has the expected trans- planar core geometry,76 the related fluorinated imido complex [{ MoO(p-NC,F,)Cp') ,]quite unexpectedly possesses a cis-puckered central core previously only observed for the analogous tetraoxo species.77 The sulfido complex displays some interesting reactivity.Addition of AgOTf affords a one-dimensional polymer in which dimolybdenum units are linked by repeating SAg,S rings while iodine gives the crystallographically characterized charge-transfer adduct [MO(NBU')(~-SI,)C~],.~~ Bergman and coworkers have reported the synthesis of the diiridium imido complexes [Ir2(PR,Me)(p-NR')Cp;] (R = Ph R' = But; R = Me R' = Ph),78 and also heterobimetallic [Cp,Zr(p-NBu')IrCp*] (36).79The latter is highly reactive undergoing addition of both polar (NH OH SH) and non-polar (H, SiH CH) bonds across the metal-metal vector. A very unusual transformation occurs upon addition of diethylphosphine oxidative addition of the phosphorus-hydrogen bond being fol- lowed by insertion of the phosphido moiety into the imido ligand to yield [Cp,Zr(p- Bu'NPEt,)IrHCp*] (37).79 Reaction of [{ReO(p-O)Cp*),] with [W(CO),(CGCPh)Cp] at 100"C affords the bridged acetylide complex [Cp*Re(O)(p-C=CPh)W(CO),Cp] (38) which reacts further with oxygen at 100°C to give the isomer [Cp*Re(CO)(p-CO)(p-C-CPh)W(O)Cp] (39) as a result of intermetal 0x0 transfer.When the reaction was carried out with 170-labelled oxygen the label was incorporated suggesting that a peroxo complex may be an intermediate in the transformation.80 Publications from three different groups are concerned with mixed os-mium-tungsten 0x0-containing clusters. Hydrogenation of [Os,W(CO) (p3-72 R.S.Dickson M. J. Liddell B. W. Skelton and A.H. White Aust. J. Chem. 1994 47 1613. 73 J. Sundermeyer and D. Runge Angew. Chern. Int. Ed. Engl. 1994 33 1255. 74 J. Sundermeyer D. Runge and J.S. Field Angew. Chem. Int. Ed. Engl. 1994 33 678. 75 S. Simone and J. Sundermeyer J. Organomet. Chem. 1994 472 127. 76 J. Allshouse R. C. Haltiwanger V. Allured and M. Rakowski Du Bois Inorg. Chem. 1994 33 2505. 77 J. Fawcett J. H. Holloway E. G. Hope D. R. Russell G. C. Saunders and M. J. Atherton J. Organomet. Chem. 1994 464 C20. 78 D. A. Dobbs and R. G. Bergman Organometallics 1994 13,4594. 79 A.M. Baranger and R.G. Bergman J. Am. Chem. Soc. 1994 116 3822. N.3. Lai W.-C. Tu Y. Chi S.-M. Peng and G.-H. Lee Organometallics 1994 13 4652. 410 G. Hogarth Ctol)Cp] results in reduction of a carbonyl ligand and formation of [Os,W(p- H)(CO),(~-O)(~-CH~O~)C~],~~ while thermolysis of [Os,W(CO) {p3-q2-C(O)CH,tol}Cp] affords [Os,W(CO),(p-O)(p3-CCH,tol)Cp],again by car-bon-xygen bond cleavage.82 The latter shows an extensive reactivity centring around the alkylidyne moiety while the 0x0 ligand acts as an innocent spectator.82 A further example of the formation of an oxide upon carbon-oxygen bond cleavage is found in the synthesis of square-based pyramidal [Os,W,(p-H)(CO),(p-O)(p3-CMe)Cp2] and trigonal bipyramidal [Os,W(CO) ,,(p-O)(p3-CMe)Cp] when [Os (p-H)(CO),{p-O=CCH,W(CO),Cp}] is pyr~lysed.~~ In the Os,W complex the 0x0 ligand asymmetrically bridges a tungsten-osmium vector lying closer to the former.Dissolution in dichloromethane however leads to the isolation of isomeric [Os,W(CO) ,(p,-O)(p,-CMe)Cp] in which the 0x0 ligand is three-coordinate and a metal-metal bond is cleaved.Surprisingly heating the latter at 190"C in the solid state regenerates the initial isomer.83 Puddephatt and coworkers give details of the reactivity of [Pt,(p-dppm),(p,- ReO,)]' addition of neutral (CO) and charged (Cl- Br- I-) two-electron donor ligands occurring to the triplatinum face on the cluster.84 Two 0x0-capped tri- ruthenium arene clusters namely [Ru3(p-H),(p-X)(p3-0)(q6-arene),] '(X = H Cl) contain closed (X = H) and open (X = C1) trinuclear centre^.^' 9 Oxygen-and Sulfurcontaining Macrocycles Went and coworkers have used a dicobalt framework in order to prepare oxygen86 and containing macrocycles with carbon-carbon triple bonds.For example protonation of [Co,(CO),(p-dppm)(p-HOCHRC-CCHROH)I results in the forma- J. T. Park J.-H. Chung H.-K. Kim W. K. Yoon I.-H. Suh and J.-H. Lee Bull. Korean Chem. SOC.,1994 15 599. 82 J.T. Park Y. Chi J. R. Shapley M. R. Churchill and J. W. Ziller Organometallics 1994 13 813. 83 J.-H. Gong D.-K. Hwang C.-W. Tsay Y. Chi S.-M. Peng and G.-H. Lee Organometallics 1994,13 1720. 84 J. Xiao L. Hao R. J. Puddephatt L. Manojlovic-Muir K. W. Muir and A. A. Torabi J. Chem. SOC.,Chem. Commun. 1994 2221. *' G. Meister G. Rheinwald H. Stoeckli-Evans and G. Suss-Fink J. Chem. Soc. Dalton Trans. 1994,3215. 86 S.C. Bennett J.C. Jeffery and M.J. Went J. Chem. SOC.,Dalton Trans. 1994 3171. F.G.Mohmand K. Thiele and M. J. Went J. Organomet. Chem. 1994 471 241. Organometallic Chemistry of Bi- and Polynuclear Complexes 411 tion of metal-stabilized dicarbenium complexes which react further with diols HO(CH,),OH (n = 4-6) to give tetraoxacyclodiyne complexes [Co,(CO),(p- dppm){p-C-CCHRO(CH,),OCHR)I, in which the dicobalt centres are incorpor- ated into the macrocycle. A similar synthetic methodology has been used to prepare the sulfur-containing complexes [Co,(CO),{p-C,(CH,SCH2CH~),S]](40) and [CO,(CO),(~-C~CCH,S~~~~~~~~~~~~~~)]~ which lose the metal fragment(s) upon addition of Me,NO to afford the free macrocycles 1,4,7-trithiacycloundec-9-yne and 1,4,7,12,15,18-hexathiacyclodocosa-9,20-diyne respectively. Adams et al. report that thermolysis of 1,5,9-trithiacyclododecane(12-S-3) with pentanuclear [Ru,(CO),,(p5-C)] initially results in the formation of [RU,(CO)~~(~~- C)(p-q1-12-S-3)] in which only a single sulfur atom is metal bound.However under more forcing conditions further carbonyl loss gives [Ru,(CO) (p5-C)(p-q3-12-S-3)] in which all three sulfurs are coordinated to the cluster.88 The same workers also give details of the ring-opening oligomerization reactions of thietane (4-S- 1).89 The previously reported complex [Re3(p-H)3(CO),,(p-4-S-l)]reacts with an excess of thietane resulting in ring-opening and oligomerization to give [Re,@-H),(CO),,{p- S(CH,),},] (n = 4,5,7). Treatment with pyridines release the free macrocycles 12-S-4 16-S-4 and 24-S-6 respectively. The crystal structures of [{(q5-C,H,SCH2CH,)},SFePd]2+ (41)and an acetonitrile adduct have been reported in which the 1,l'-disubstituted ferrocene fragment is part of the macrocycle the palladium being bound within." 1*+ 10 Medium and High Nuclearity Clusters Thermolysis of [Ru5(CO),,(p5-C)] with cyclopentadiene gives [Ru,(CO),,(p,- C)CP,],~~ while reaction of the related dianion [RU~(CO),,(~,-C)]~-with [Pd(a~etone),(q~-C,Ph,)]~ + results in both oxidation of the cluster and transfer of the organic ligand to yield [Ru,(CO) ,(p5-C)(q4-C,Ph,)].The cyclobutadiene ring is bound to one basal ruthenium of the square-based pyramidal cluster.92 Thermolysis of [Ru,(CO),,] with the cyclic phosphine P,Buk affords a number of phosphinidene clusters including [RU~(C~)~,(~~-PBU')~(~~-PBU~)~, [Ru,(CO),,(p,-PBu'),(p4- 88 R.D.Adams S. B. Falloon and K. T. McBride Organometallics 1994 13 4870. 89 R.D. Adams and S. B. Falloon J. Am. Chem. SOC. 1994 116 10540. 90 M. Sato K. Suzuki H. Asano M. Sekino Y. Kawata Y. Habata and S. Akabori J. Organomet. Chem. 1994,470 263. 91 A. J. Blake P. J. Dyson R. C. Gash B. F.G. Johnson and P. Trickey J. Chem. SOC.,Dalton Trans. 1994 1105. 92 P. J. Bailey A. J. Blake P. J. Dyson S. L. Ingham and B. F. G. Johnson J. Chem. SOC.,Chem. Commun. 1994,2233. 412 G. Hogarth PBu'),] and [Ru9(p-H),(CO),,](p3-PBu'),(p7-P)].The last contains an interstitial phosphide resulting from phosphorussarbon bond cleavage.93 Reaction of dicobalt octacarbonyl with Na,Te and [PPh,]Cl in methanol under solvothermal conditions affords [Co 1(Co),,(p4-Te)5(p6-Te)2]2 which has D,, -symmetry and consists of an elongated pentagonal prismatic array of cobalt atoms with a single cobalt in the centre.Each of the five square faces is capped by tellurium the remaining two telluriums capping the pentagonal faces while also being bound to the interstitial cobalt.94 Vacuum pyrolysis of [Os,(CO),,(NCMe),] at 260 "C affords the largest osmium carbonyl clusters yet isolated namely [os17(co)36]2- and [OS,,(CO),,]~-. The former consists of a trigonal pyramidal core of fourteen osmium atoms with a further three capping; the latter has a cubic close packed arrangement of metal centres and is the first example of a totally symmetrical array of metal atoms of this nuclear it^.^^ The hex-3-yne complex [Pt2Ru,(CO),,(p,-EtC,Et),(p,-EtC2Et)] has been pre- pared and crystallographically characterized.It consists of an Ru,Pt dodecahedron capped by the remaining two ruthenium atoms. Interestingly the complex does not obey the polyhedral electron skeletal pair theory but its structure can be rationalized in terms of the 18-electron rule.96 The nonanuclear cluster [Ru6Pt3(p-H)(p3-H)(CO),,(p3-PhC,Ph)] prepared from diphenylacetylene and [Ru,Pt,(p-H),(p,- H)(CO),,],97 is shown to be an effective catalyst for the hydrogenation of the acetylene to (2)-~tilbene.~' At higher temperatures however the catalyst is transformed into new species with low catalytic ability as a result of further alkyne addition to the cluster.98 A further mixed-metal nonanuclear cluster namely [Ru,Rh,(CO),,(p,-B)(p7-B)] -(42),is located from the reaction of [Ru,(CO),(BH,)]- with [(RhCl(CO),f,].It has a complex structure based on a trigonal prismatic Ru,Rh unit with an open-triangular array of the three further metal centres capping a square face.99 The twelve-atom cluster [Pd,RU,(CO),2(p-CO),(p3-co)6]2 consists of a trigonally distorted octa- -hedron of palladium atoms capped by ruthenium centres.'" [Pd,Mn,(CO),,(p,-q2,q2,q2-cyclo-PC,Ph2H2),] (43) has a highly unusual structure based on an 'I' shaped array of metal centres. The 2,5-diphenylphospholyl ligand bridges the palladium atoms through phosphorus while coordinating to the manganese in a diene-like fashion."' Several larger heterometallic clusters include coinage metals.Reaction of [OS,(CO),,]~-with [Au,Cl,(p-L-L)] [L-L = Ph,P(CH,),PPh, n = 1,2,4] in the presence of TlPF affords [Os,(CO),,(p-Au,(p-L-L)}] which consists of a bicapped octahedron of osmium atoms; one gold atom is in a capping site while the second bridges a metal-metal edge.lo2 The triiron-gold cluster [Fe,(CO),{p3-93 E. Charalambous L. Heuer B. F. G. Johnson J. Lewis W.-S. Li M. McPartlin and A. D. Massey J. Organomet. Chern. 1994 468 C9. 94 R. Seidel R. Kliss S. Weissgraber and G. Henkel J. Chem. SOC. Chem. Commun. 1994 2791. '' B. F. G. Johnson J. Lewis M. McPartlin H. R. Powell P. R. Raithby and W.T. Wong J. Chem. SOC. Dalton Truns. 1994 521. 9b R. D. Adams T.S. Barnard Z. Li W. Wu and J. Yamamoto J. Cluster Sci. 1994 5 551.97 R. D. Adams T. S. Barnard 2.Li W. Wu and J. Yamamoto Organometallics 1994 13 2357. 98 R. D. Adams T.S. Barnard Z. Li W. Wu and J. Yamamoto J. Am. Chem. SOC. 1994 116 9103 99 J. A. Galsworthy C. E. Housecroft and A. L. Rheingold J. Chem. SOC. Dalton Trans. 1994 2359. loo E. Brivio A. Ceriotti R. D. Pergola L. Garlashelli F. Demartin M. Manassero M. Sansoni P. Zanello and F. Laschi J. Chem. Soc. Dalton Trans. 1994 3237. lo' L. Brunet F. Mercier L. Richard and F. Mathey Angew. Chem. Int. Ed. Engl. 1994 33 142. Io2 Z. Akhter S. I. Ingham J. Lewis and P. R. Raithby J. Orgunomet. Chem. 1994,474 165. Organometallic Chemistry of Bi-and Polynuclear Complexes 2-{Au(PPh,)),)] has a square-planar arrangement of gold centres'03 while related + + cobalt clusters [Co(CO),{Au(PPh,)),] and [Co(CO),{Au(PPh,),)]+ consist re- spectively of a bicapped trigonal bypyramid of metal atoms with the cobalt in an equatorial site and a fragment of an icosahedron formed by the gold atoms with the cobalt in the centre.lo4 In a novel reaction addition of [Ni6(CO),,]2- to [AuCI(PPh,)] leads to complete loss of phosphine.The products [Ni12AU6(CO),2(p-CO)12]2-, is best considered as containing a gold octahedron with alternate faces capped in a trigonal prismatic fashion by four Ni,(CO) moieties.lo5 Of the two novel silver-containing clusters [Ag4{p- Fe(C0),},I4-(44)and [Ag5(p-Fe(CO)4),(p3-Fe(CO)4}2]3-(45),the smaller con- sists of a square-planar array of silvers with all four edges bridged by iron carbonyl moieties while the larger comprises a bow-tie arrangement of the coinage metal atoms with iron tetracarbonyl units bridging both ends the top and the bottom.lo6 (44) Fe = Fe(C0)4 (45) Fe = Fe(C0)4 I1 Assorted Complexes Reaction of Cp*H with [OSH2Br6] yields [(OsBr,Cp*},] which provides a conveni-ent entry into diosmium chemistry.For example reduction with lithium aluminium hydride affords the tetrahydro-bridged complex [{ OS(~-H),C~*),].~~~ The diiron mesityl complex [{ Fe(mes)(p-mes)},] exhibits some interesting reactivity. Thus CNBu' inserts into both bridging and terminal sites to give the homoleptic iminoacyl complex [(Fe(~2-mesC=NBu')(p-mesC=NBu')),l while insertion of CNPh occurs only into the bridging sites."' Reduction of [Mn2(p-H)2(C0)6(p-dppm)]by sodium D.L. Sunick P. S. White and C.K. Schauer Angew. Chem. Int. Ed. Enyl. 1994 33 75. Io4 M. Holzer J. Straehle G. Baum and D. Fenske Z. Anorg. AUg. Chem. 1994 620 192. lo' A. J. Whoolery Johnson B. Spencer and L. F. Dahl Inorg. Chem. Acta. 1994 227 269. V. G. Albano F. Azzaroni M. C. Iapalucci G. Longoni M. Monari S. Mulley D. M. Proserpio and A. Sironi Inorg. Chem. 1994 33 5320. lo' C. L. Gross S. R. Wilson and G.S. Girolami J. Am. Chem. SOC.,1994 116 10294. 414 G. Hogarth amalgam affords the dianion [Mn,(CO)6(p-dppm)]2- which displays an extensive chemistry. Acid chlorides afford acyl complexes while oxidation by two equivalents of ferrocenium ion in the presence of primary alkynes affords side-bound vinylidene complexes [Mn2(CO)6(p-q1 ,q2-C=CHR)(p-dppm)] .log Silylene diiron complexes [Fe,(CO),(p-Simes,)]' lo and [Fe,(CO),(p-CO)(p-SiBu'X)Cp,] (X = C1 Br I),' '' have been prepared one of the latter (X = I) reacting with strong Lewis bases"' to give donor-stabilized cationic p-silylyne complexes [Fe,(CO),(p-CO)(p-%But-base)Cp,]+.The diruthenium bis(sily1ene) complex [{ Ru(p-H)(p-SiPh,)Cp*}J reacts with acetylene to give [Ru,(p-H),(p-Ph,SiCH=CHSiPPh,)CpT] (46),which when hydro- genated at 80 "C yields the agostic silyl complex [Ru,H(p-SiPh,H)(p-Ph,SiCH=CH,)Cp;] (47) as a result of silicon-carbon bond cleavage.' l2 The nature of the substituent on the bridging thiolate ligands in [Mo,(CO)(CN)(p-SR),Cp,l -has a profound effect upon the site of methylation being directed at the lone pair on sulfur with electron-releasing substituents and to the cyanide with electron-withdrawing groups.' ' Oxidation of the bridging sulfido ligand in [Re,X,(CS)(CO)(p-S)(p-X)(p-dppm),] + by an NOPF6/02 mixture affords a bridging sulfur dioxide complex stable one- and two-electron reduction products of which have also been prepared.' l4 Two publications give details of ring-opening reactions of thiophenes.Addition of thiophene itself to [{W(OBu') 3} ,] affords [W ,(OBu'),(p-OBu')(q'-C 5H 3S)(p-q2,ql-CCH,CH=CHS)] in which one ring (which has lost a hydrogen) is a-bound through carbon while the second is opened and bridges the ditungsten centre.'I5 Deeming and coworkers have reported on reactions of 2,2'-bithiophene and 2,2',5',2"-trithiophene by Group 8 metal carbonyls.Thus oxidative addition of carbon-hydrogen bonds to the triosmium centre occurs with [Os3(CO),,(NCMe),]. Sulfur-carbon bond cleav- age is however not noted. In contrast reactions with [RU~(CO)~,] or [Fe,(CO),] yield ferrole complexes [M,(Co),(p-HC=CHCH=cR)] (48)(R = thiophene bi- thiophene) as a result of a double carbon-sulfur bond cleavage and extrusion of the latter. In the case of iron an intermediate product [Fe,(CO),(p-q2,q'-A. Klose E. Solari C. Floriani A. Chiesi-Villa C. Rizzoli and N. Re J. Am. Chem. Soc. 1994,116,9123. lo9 X.-Y. Liu V. Riera and M. A. Ruiz Organometallics 1994 13 2925. H. Tobita I. Shinagawa S. Ohnuki M. Abe H. Izumi and H. Ogino J. Organomet. Chem. 1994,473,187. Y. Kawano H. Tobita M. Shimoi and H.Ogino .I.Am. Chem. Soc. 1994 116 8575. T. Takao H. Suzuki and M. Tanaka Organometallics 1994 13 2554. M.-L. Absasq F.Y. Petillin and J. Talarmin J. Chem. Soc. Chem. Commun. 1994 2191. l4 K. J. Kolodsick P.W. Schrier and R. A. Walton Polyhedron 1994 13 457. M. H. Chisholm S.T. Haubrich J. D. Martin and W. E. Streib,.I. Chem. Soc. Chem. Comrnun. 1994,683. 415 Organometallic Chemistry of Bi-and Polynuclear Complexes SCH=CHCHCR)] (49),is also observed; ring-opening has occurred but the sulfur has not been extruded.' ' The tetramethylfulvene-bridged diiron complex [Fe,(CO),(p-q2,q5-cH,CsMe4)] (50)reacts with carbon disulfide to give the dithiocarboxylato complex [Fe,(CO),(p,- S2CCH,CsMe,)] (51) resulting from insertion into the iron-methylene bond.' l7 Photolysis of [Co(CO),Cp] leads to the isolation of a third isomeric form of [(Co(p-CO)Cp),] containing only doubly bridging carbonyls as opposed to previous- ly prepared isomers which have terminal or triply bridging ligands.' l8 Heating the methylene complex [Co,Ir(p-CO),(p-CH,)Cp,Cp*] at 120"C results in carbonyl loss and oxidative addition of a carbon-hydrogen bond yielding [Co,Ir (p-H)(&-Co)(p3- CH)Cp,Cp*] ;the transformation is reversed upon carbonylation." Crystallographi-cally characterized [Re3(p-H),(CO)9(p3-FBF3)]2is a rare example of the tetra- -fluoroborate anion capping a metal triangle through a single fluorine atom.'20 The mechanism of carbonyl substitution in the butterfly clusters [MO,CO,(CO),-~L,(~~-S)~(~~-S)C~!J (n = 1,2; L = PR,) has been studied in some detail.The process is associative and involves formation of an adduct in a pre-equilibrium step; the incoming ligand binds to a wing-tip cobalt centre and the sulfido moiety sitting in the butterfly cage becomes three-coordinate.'21 Reaction of other butterfly clusters [Ru,(CO),~(~~-PR)] (R = Ph NPr') with Ph,P(O)C-CBu' affords the tetrahedral complexes [Ru,(CO),(p-CO)(p3-C,Bu')(p3-Ph,POPR)] re-sulting from a novel phosphorus-oxygen bond formation process.' ,* Thermolysis of [Os,(p-H)(CO),,Cp*] at 50 "C results in simple carbonyl loss and metal-metal bond formation. However further heating above 90°C leads to the stepwise car-bon-hydrogen bond cleavage of two of the methyl groups on the cyclopentadienyl A.J. Arce P.Arrojo Y. De Sanctis M. Marquez and A.J. Deeming J.Organomet. Chem. 1994,479,159. H. Hashimoto H. Tobita and H. Ogino Organometallics 1994 13 1055. M. P. Robben W.E. Geiger and A. L. Rheingold Inorg. Chem. 1994 33 5615. l9 F. H. Forsterling and C. E. Barnes Organometallics 1994 13 3770. C. S. Yang H.C. Hornig F. L. Liao and C. P. Cheng J. Chem. SOC. Chem. Commun. 1994 1657. 121 0.J. Curnow J. W. Kampf M. D. Curtis J.-K. Shen and F. Basolo J. Am. Chem. Soc. 1994,116,224. lZ2 J. F. Corrigan N. J. Taylor and A. J. Carty J. Chem. SOC. Chem. Commun. 1994 1769. 416 G. Hogarth moiety giving [Os4(p-H),(CO),,(p-q1,q5-C5Me4CH2)] (52) and [Os4(p-H)3(C0)9{p3-q1,ql ,q5-C5Me,(CH,),}] respecti~ely.'~~ Ru .Ru Polymeric films with the formula [{ Ru(CO),(bipy)},] (53) formed upon elec- trochemical reduction of [Ru(CO),(bipy),],+ are believed to contain chains of ruthenium atoms.' 24 lZ3 W.Wang H. B. Davis F. W. B. Einstein and R. K. Pomeroy Orgunometullics 1994 13 5113. lZ4 S. Chardon-Noblat M.-N. Collomb-Dunand-Sauthier A. Deronzier R. Ziessel and D. Zsoldes Inorg. Chem. 1994 33 4410.