Chemistry of polynuclear metal complexes with bridging carbene or carbyne ligands. Part 101. Synthesis of the compounds [WPt(µ-CC6H4Me-4)(µ-σ:ηx-C2BnHn–1Me2)(CO)2(PMe2Ph)2](x= 5, n= 9; x= 6, n= 10); crystal structures of an isomer of each complex

Abstract

In acetone at ambient temperatures, the reagents [PtCl(Me)(PMe₂Ph)₂], TIBF₄, and [NEt₄][W(CC₆H₄Me-4)(CO)₂(η⁵-C₂B₉H₉Me₂)] afforded [WPt(µ-CC₆H₄Me-4)(µ-σ:η⁵-C₂B₉H₈Me₂)(CO)₂(PMe₂Ph)₂](two isomers), and a small amount of a salt formulated as [PtMe(PMe₂Ph)₃][W₂Pt(µ-CC₆H₄Me-4)₂(µ-σ:η⁵-C₂B₉H₈Me₂)(CO)₄(η⁵-C₂B₉H₉Me₂)]. The structure of one isomer of the dimetal compound was determined by X-ray diffraction. The W–Pt bond [2.720(1)Å] is spanned by the p-tolylmethylidyne group [W–µ-C 1.89(1), Pt–µ-C 2.14(1)Å] and by a C₂B₉ fragment. The latter is co-ordinated to the W atom via the open pentagonal face of the nido-icosahedral cage, and bridges to the Pt atom through an exopolyhedral B–Pt σ bond [2.17(1)Å]. This boron atom is in the β site with respect to the carbon atoms in the [graphic omitted] ring. In the other isomer it is the boron α to a carbon atom which forms the B–Pt bond. The reaction between the compounds [PtCl(Me)(PMe₂Ph)₂],TIBF₄, and [NEt₄][W(CC₆H₄Me-4)(CO)₂(η⁶-C₂B₁₀H₁₀Me₂)] in thf (tetrahydrofuran) also yields two isomers of a dimetal species [WPt(µ-CC₆H₄Me-4)(µ-σ:η⁶-C₂B₁₀H₉Me₂)(CO)₂(PMe₂Ph)₂]. The structure of the isomer formed in greatest yield (ca. 70%) was established by X-ray diffraction. The W–Pt bond [2.738(1)Å] is bridged by the alkylidyne group [W–µ-C 1.92(1), Pt–µ-C 2.14(1)Å] and by a C₂B₁₀ fragment. The non-planar [graphic omitted] face of the latter is η⁶ co-ordinated to the tungsten, but the cage also forms a B–Pt σ bond [2.15(1)Å]. This linkage involves a boron atom of the B₃ group α to a carbon, and correspondingly the other isomer is assigned a structure in which it is the [graphic omitted] atom of the hexagonal ring which bonds to platinum. The n.m.r. data (¹H, ¹³C-{¹H}, ¹¹B-{¹H}, and ³¹P-{¹H}) for the new compounds are reported, and are in agreement with the structures proposed.