Chemistry of polynuclear metal complexes with bridging carbene or carbyne ligands. Part 58. Some reactions of the compounds [MW(µ-CC6H4Me-4)(CO)3(η5-C9H7)(η5-C2B9H9Me2)](M = Mo or W); crystal structures of the complexes [W2(µ-CC6H4Me-4)(CO)2(L)(η5-C9H7)(η5-C2B9H9Me2)][L = N2C(C6H4Me-4)2 or O]

Abstract

The compounds [MW(µ-CC₆H₄Me-4)(CO)₃(η⁵-C₉H₇)(η⁵-C₂B₉H₉Me₂)](M = Mo or W) react with the diazoalkanes N₂CR₂(R = C₆H₄Me-4 or Ph) in diethyl ether at room temperature to afford the dimetal complexes [MW(µ-CC₆H₄Me-4)(CO)₂(N₂CR₂)(η⁵-C₉H₇)(η⁵-C₂B₉H₉Me₂)]. The molecular structure of the compound with M = W and R = C₆H₄Me-4 has been established by X-ray diffraction. The tungsten–tungsten bond [2.777(1)Å] is bridged by the p-tolylmethylidyne ligand [µ-C–W 1.975(5) and 2.081(5)Å] and by a three-centre two-electron B–H ⇀ W bond formed by one tungsten atom and a BH fragment in the pentagonal face of the η⁵-C₂B₉H₉Me₂ group attached to the other tungsten centre. The latter also carries two terminally bound CO ligands. The tungsten atom which is part of the B–H ⇀ W system is bonded by the indenyl ligand and a monodentate N₂C(C₆H₄Me-4)₂ group [W–N 1.768(5)Å, W–N–N 166.8(4)°]. The compounds [W₂(µ-CC₆H₄Me-4)(CO)₂(L)(η⁵-C₉H₇)(η⁵-C₂B₉H₉Me₂)][L = O or NC₆H₄Me-4] have been prepared by treating [W₂(µ-CC₆H₄Me-4)(CO)₃(η⁵-C₉H₇)(η⁵-C₂B₉H₉Me₂)] with aqueous H₂O₂ and N₃C₆H₄Me-4, respectively. The n.m.r. spectra [¹H, ¹³C-{¹H}, and ¹¹B-{¹H}] of all the new compounds are reported, and display features indicative of the presence of µ-CC₆H₄Me-4 groups end three-centre two-electron B–H ⇀ M (M = Mo or W) bonds.