Chemistry of polynuclear metal complexes with bridging carbene or carbyne ligands. Part 52. Synthesis and reactions of the compounds [RuW(µ-CR)(CO)3(η-C5H5)(η5-C2B9H9Me2)](R = C6H4Me-4 or Me); crystal structures of [RuW(µ-CC6H4Me-4)(CO)3(η-C5H5)(η5-C2B9H9Me2)] and [N(PPh3)2][RuW(µ-CC6H4Me-4)(µ-σ,η5-C2B9H8Me2)(CO)3(η-C5H5)]

Treatment of the compounds [N( PPh3)2[W(CR)(CO)2(η5-C2B9H9Me2)](R = C6H4Me-4 or Me) with [Ru(CO)(NCMe)2(η-C5H5)][BF4] in CH2Cl2 affords the dimetal complexes [RuW(µ-CR)-(CO)3(η-C5H5)(η5-C2B9H9Me2)]. The structure of the product with R = C6H4Me-4 has been established by a single-crystal X-ray diffraction study. The Ru–W bond [2.803(2)A] is spanned by the p-tolymethylidyne group [Ru–µ-C 2.20(7); W–µ-C, 1.890(6)A]. The tungsten atom carries two CO ligands and the η5-C2B9H9Me2 cage. The ruthenium atom is ligated by a CO group and the cyclopentadienyl anion, and also by the unique B–H bond of the open pentagonal face of the icosahedral η5C2B9H9Me2 fragment [B–Ru, 2.400(7); B–H, 1.33; Ru–H, 1.67 A]. Deprotonation of [RuW(µ-CC6H4Me-4)(CO)3(η-C5H5)(η5-C2B9H9Me2)], on basic alumina or by n-butyl-lithium, in the presence of [N( PPh3)2] Cl gives the salt [N( PPh3)2][RuW(µ-CC6H4Me-4)(µ-σ,η5-C2B9H8Me2)-(CO)3(η-C5H5)] which was structurally characterised by X-ray diffraction. The structure of the anion [Ru–W, 2.748(l); Ru–µ-C, 2.100(6); W–µ-C,1.941(5)A] is very similar to that of its neutral precursor, the major difference being replacement of the B–H⇀Ru three-centre two-electron bond by a direct B–Ru linkage [2.155(6)A]. The C2B9H8Me2 cage thus adopts an unusual µ-σ,η5 bonding mode at the WRu centre. Some reactions of the ruthenium–tungsten dimetal species are described, and spectroscopic data are reported and discussed.