Chemistry of polynuclear metal complexes with bridging carbene or carbyne ligands. Part 74. Salts of the anions [W(CR)(CO)2(η5-C2B9H9Me2)]–(R = C6H4Me-2 or C6H3Me2-2,6) as reagents for the synthesis of compounds with heteronuclear metal–metal bonds: crystal structure of [NEt4][FeW(µ-CC6H3Me2-2,6)(CO)5(η5-C2B9H9Me2)]

Abstract

The salts [X][W(CR)(CO)₂(η⁵-C₂B₉H₉Me₂)](X = NEt₄, R = C₆H₄Me-2 or C₆H₃Me₂-2,6; X = PPh₄, R = C₆H₃Me₂-2,6) have been prepared, and used to synthesise a variety of compounds containing heteronuclear metal–metal bonds. Thus treatment of [NEt₄][W(CR)(CO)₂(η⁵-C₂B₉H₉Me₂)] with [AuCl(PPh₃)] in thf (tetrahydrofuran), in the presence of KPF₆, affords the dimetal compounds [AuW(µ-CR)(CO)₂(PPh₃)(η⁵-C₂B₉H₉Me₂)]. The reaction between [Pt(cod)₂](cod = cyclo-octa-1,5-diene) and [PPh₄][W(CC₆H₃Me₂-2,6)(CO)₂(η⁵-C₂B₉H₉Me₂)] affords the salt [PPh₄][PtW(µ-CC₆H₃Me₂-2,6)(CO)₂(cod)(η⁵-C₂B₉H₉Me₂)]. The latter with [AuCl(PPh₃)] in thf, in the presence of TIPF₆, yields the trimetal compound [AuPtW(µ-CC₆H₃Me₂-2,6)(CO)₂(PPh₃)(cod)(η⁵-C₂B₉H₉Me₂)]. Treatment of [NEt₄][W(CR)(CO)₂(η⁵-C₂B₉H₉Me₂)](R = C₆H₄Me-2) with [Fe₃(CO)₁₂] in thf affords a mixture of the compounds [NEt₄][FeW(µ-CR)(CO)₅(η⁵-C₂B₉H₉Me₂)], [NEt₄][FeW{µ-CH(R)}(µ-σ:η⁵-C₂B₉H₈Me₂)(µ-CO)(CO)₅], and [NEt₄][Fe₂W(µ₃-CR)(µ₃-σ:σ′:η⁵-C₂B₉H₇Me₂)(CO)₈]. A similar reaction with [NEt₄][W(CC₆H₃Me₂-2,6)(CO)₂(η⁵-C₂B₉H₉Me₂)] gives [NEt₄][FeW(µ-CC₆H₃Me₂-2,6)(CO)₅(η⁵-C₂B₉H₉Me₂)] as the only iron–tungsten compound. The structure of the latter has been established by X-ray diffraction. The Fe–W bond [2.600(1)Å] is spanned by the CC₆H₃Me₂-2,6 group [µ-C–Fe 1.891(5) and µ-C–W 1.976(6)Å]. The iron atom is ligated by three essentially orthogonal CO groups. The tungsten atom is co-ordinated by the pentagonal face of the nido-icosahedral fragment C₂B₉H₉Me₂, and by two CO groups, one of which semi-bridges the metal–metal bond [W–C–O 165.4(6)°]. The reaction between [PPh₄][W(CR)(CO)₂(η⁵-C₂B₉H₉Me₂)](R = C₆H₃Me₂-2,6) and [Ru(CO)(NCMe)₂(η-C₅H₅)][BF₄] in CH₂Cl₂ gives the dimetal compound [RuW(µ-CR)(CO)₃(η-C₅H₅)(η⁵-C₂B₉H₉Me₂)] which has an exopolyhedral B–H⇀Ru three-centre bond. The n.m.r. spectra (¹H, ¹³C-{¹H}, ¹¹B-{¹H}, and ³¹P-{¹H}) of the new compounds are discussed in relation to their structures.