Chemistry of polynuclear metal complexes with bridging carbene or carbyne ligands. Part 103. Carbaborane molybdenum and tungsten dimetal complexes

Abstract

Treatment of the complex [Mo(CO)₂(NCMe)₂(η⁵-C₉H₇)][BF₄](C₉H₇= indenyl) with the salts [NEt₄][W(CCCBu^t)(CO)₂(η⁵-C₂B₉H₉Me₂)]and [NEt₄][Mo(CC₆H₄Me-4)(CO){P(OMe)₃}(η⁵-C₂B₉H₉Me₂)] in CH₂Cl₂ affords, respectively, the dimetal compounds [MoW(µ-CCCBu^t)(CO)₃(η⁵-C₉H₇)(η⁵-C₂B₉H₉Me₂)]and[Mo₂(µ-CC₆H₄Me-4)(CO)₂{P(OMe)₃}(η⁵-C₉H₇(η⁵-C₂B₉H₉Me₂)]. Similarly, reactions between the salts [NEt₄][M(CR)(CO)₂(η⁵-C₂B₉H₉R′₂)](M = Mo or W, R = C₆H₄Me-4, R′= H; M = W, R = C₆H₄Me-4 or C₆H₄Me-2, R′= Me; M = W, R = CCBu^t, R′= Me) and [Mo(CO)₂(NCMe)(η⁷-C₇H₇)][BF₄] yield the dimetal complexes [MMo(µ-CR)(CO)₂(η⁷-C₇H₇)(η⁵-C₂B₉H₉R′₂)](M = W, R = C₆H₄Me-4, C₆H₄Me-2, or CCBu^t, R′= Me; M = Mo or W, R = C₆H₄Me-4, R′= H). The compounds [MoW(µ-CC₆H₄Me-4)(CO)₂(η⁷-C₇H₇)(η⁵-C₂B₉H₁₀Me)] and [MoW(µ-CC₆H₄Me-4)(CO)₂(η⁷-C₇H₇)(η⁶-C₂B₁₀H₁₀Me₂)] have also been prepared using the reagents [NEt₄][W(CC₆H₄Me-4)(CO)₂(η⁵-C₂B₉H₁₀Me)] and [NEt₄][W(CC₆H₄Me-4)(CO)₂(η⁶C₂B₁₀H₁₀Me₂)]. All the dimetal compounds have structures in which the metal–metal bonds are bridged by an alkylidyne group and by a B–H⇀Mo three-centre two-electron bond. The latter involves a boron atom lying in the face of the nido-carbaborane fragment which is co-ordinated to the other metal centre in the η⁵(for C₂B₉H₉R′₂) or η⁶(for C₂B₁₀H₁₀Me₂) bonding mode. The n.m.r. data (¹H, ¹³C-{¹H}, ¹¹B-{¹H}, ¹¹B, and ³¹P-{¹H}) for the new compounds are reported and discussed in the context of the structures proposed.