Tungsten complexes dinuclear

Bis[iV,iV -di(2-pyridyl)-imidazol-2-ylidene]aurate(I) tetrafluoroborates, preparation, 2, 292-293 Bis[iV,iV -di(2-pyridyl-methyl)-imidazol-2-ylidene]aurate(I) tetrafluoroborates, preparation, 2, 292-293 Bis(diselenolate) complexes, dinuclear iron compounds, 6, 242 Bis(dithiolene) compounds, in tungsten carbonyl and isocyanide complexes, 5, 644 Bis(enolato) complexes, with bis-Cp Ti(IV), 4, 589 Bis(enones), in reductive cyclizations, 10, 502 Bis(ethanethiolato) complexes, with bis-Cp Ti(IV), 4, 601 Bis(ethene)iridium complexes, preparation, 7, 328-329 -Bis(fluorenyl)zirconocene dichlorides, preparation,... 

For edge-sharing bioctahedral, face-sharing bioctahedral, and ethane-like molecules, ditung-sten(m chemistry parallels the dimolybdenum 111 chemistry outlined previously. One of the drawbacks to low-oxidation-state dinuclear tungsten complexes is their susceptibility to oxidation.140 415"420 However, W2(/i-Cl)2Cl4(P(CH3)2(C6H5))4 (2.6950(9) A),421 W 2(jjr... 

Most complexes of trivalent tungsten are dinuclear such as, for example, in the [W2Cl9]g ion with some of them having a triple bond between the two tungsten atoms. 

Chisholm, M.H. Foiling. K. Streib. W.E. Wu, D.-D. Preparation and characterization of the kinetic and thermodynamic isomers of dinuclear molybdenum and 26. tungsten complexes with metal-metal triple bonds supported by p-tert-butylcalix[4]arene anions. Chem. Commun. 1998, 379-380. 

Usually the COOH functional groups act both as hydrogen-bond donors and acceptors. The dinuclear tungsten complex [(C5H4COOH)W(CO)3]2, 52 [118], is not a supramolecular compound but it is shown here as an example of hydrogenbonding between carboxylic acid functions and THE. 

The dinuclear tungsten complex W2(OBu )6 reacts with acetylenes and cyanides to give metathesis products of W = W, C = C, and CsN bonds/ " ... 

Tricarbonyl(6,6-diphenylfulvene)chromium(0) (52) was obtained by reaction of 6,6-diphenylfulvene with hexacarbonylchromium in 64% yield [56]. Later it was shown that almost quantitative yields can be obtained under photochemical reaction conditions starting from (benzene)Cr(CO)3 or from (mesitylene)Cr(CO)3 as the complexation reagent [63]. The corresponding molybdenum and tungsten complexes were prepared by treatment of the ligands with tris(acetonitrile)M(CO)3 (M = Mo, W) [64]. Olefin complex 53 was obtained by Wilkinson and Altman in 51% yield from 6,6-diphenylfulvene and bis(dicarbonylchlororhodium). Similar complexes were prepared with other rhodium reagents [58]. Hiibel and Weiss [59] prepared the diene tri-carbonyliron complex 54 (11-30%) in addition to the dinuclear complex, in which either one of the endocyclic double bonds is coordinated at Fe(CO)4 (49-66%). 

Reaction of [S(CCPh)2] with [Co2(CO)g] afforded 2 jhe crystallographically characterised adduct [(PhCC)S Co2(CO)6(Ti2-CCPh) ] which, on treatment with further [Co2(CO)g] afforded [S Co2(CO)6(Tl2-CCPh) 2l. The reaction of pentacarbonyl allyloxy((4-methylphenyl)ethynyl)carbene) chromium and tungsten complexes with dicobalt octacarbonyl afforded 63 tpe alkyne complexes (62) (M = Cr, W), which failed to undergo intramolecular Pauson-Khand reactions instead, at room temperature, a 1,2-elimination occurs, regenerating the metal hexacarbonyl with predominant formation of dinuclear cobalt complexes (63) - (65). 

In 1979, Rudler ef al. reported another example of the presence of a vinylidene complex during the reaction of pentacarbonyl[methoxy(methyl)carbene] tungsten 5 with MeLi followed by acidification with TFA [4]. It was proposed that the vinylidene complex 7 was generated by deprotonation of the a-proton of the carbene complex followed by elimination of methoxide and reaction with the dimethylcarbene complex 8, the addition-elimination product of MeLi with the starting carbene complex, to give the dinuclear complex 6 (Scheme 5.2). 

The distorted pentagonal-pyramidal coordination has been identified also in Mo and W oxo diperoxo siloxane complexes64 (14-17). Crystal structures for species 14, 15 and 16 have been solved, while for the tungsten dinuclear compound, structural identification was suggested on the basis of similar IR and Raman spectra obtained for complexes 16 and 1764. 

The iron-molybdenum and iron-tungsten analogs are prepared in precisely the same manner with comparative yields of pure product. Well-formed crystals of [PPN]+ salts of the dinuclear dianion may be obtained by layering diethyl ether onto a concentrated CH3CN solution of dianion complex. 

Among the more interesting metal-metal multiple bonded complexes are the hexaalkoxo dinuclear tungsten and molybdenum complexes, fM,(OR),J [Pg.418]

The striking advance since 1973 has been the synthesis of homoleptic isocyanides for vanadium and almost all of the post-group-VIA metals up to group IB (see Table I), and this has been helped in some respects by synthetic rationale. For example, the discovery of the simple reductive or nonreduc-tive cleavage of multiple metal-metal bonds in suitable dinuclear complexes of molybdenum and tungsten has provided a high yield route to W(CNPh)6 and [M(CNR)7]2+ (M = Mo, W) and related complexes (5-14). During these studies the series [M(CNR)7]2+ was completed with the isola-... 

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