Chemistry of polynuclear metal complexes with bridging carbene or carbyne ligands. Part 107. Reactions of diphenylphosphine with molybdenumtungsten dimetal complexes; crystal structures of [MoW(µ-PPh2){µ-C(OH)C(C6H4Me-4)}-(CO)(η7-C7H7)(η5-C2B9H11)]and[MoW(µ-PPh2)(CO)3(η5-C9H7){η5-C2B9H8(CH2C6-H4Me-4)Me2}]

Abstract

Treatment of the compounds [MoW(µ-CC₆H₄Me-4)(CO)₂(η⁷-C₇H₇)(η⁵-C₂B₉H₁₀R)](R = H or Me) in CH₂Cl₂with PHPh₂ affords the complexes [MoW(µ-PPh₂){µ-C(OH)C(C₆H₄Me-4)}(CO)(η⁷-C₇H₇)-(η⁵-C₂B₉H₁₀R)]. The structure of the species with R = H was established by X-ray diffraction. The Mo–W bond [2.713(1)Å] is spanned by the PPh₂ group [Mo–P 2.439(3), W–P 2.360(3)Å], and in a transverse manner by the alkyne. However, the latter is twisted so that the C(OH) atom lies appreciably closer to the tungsten [µ-C–W 2.067(8)Å] than the molybdenum [µ-C–Mo 2.352(8)Å], whereas the C(C₆H₄Me-4) atom is essentially symmetrically bridging [µ-C–Mo 2.224(9), µ-C–W 2.251(8)Å]. The molybdenum atom carries the η⁷-C₇H₇ group (C–Mo av. 2.27 Å), and the tungsten atom is η⁵ co-ordinated by the C₂B₉H₁₁ cage and a CO group. The reaction between [MoW(µ-CC₆H₄Me-4)(CO)₃(η⁵-C₉H₇)(η⁵-C₂B₉H₉Me₂)] and PHPh₂in CH₂Cl₂ gives the complex [MoW(µ-CC₆H₄Me-4)(CO)₂(PHPh₂)(η⁵-C₉H₇)(η⁵-C₂B₉H₉Me₂)]. The latter on heating in toluene at 70 °C yields the compound [MoW(µ-PPh₂)(CO)₃(η⁵-C₉H₇){η⁵-C₂B₉H₈(CH₂C₆H₄Me-4)Me₂}], the structure of which was established by X-ray diffraction. The Mo–W bond [2.708(1)Å] is bridged by the PPh₂ group [Mo–P 2.357(2), W–P 2.456(2)Å]. The tungsten atom is ligated by two CO groups, and η⁵ co-ordinated by the C₂B₉ cage. In the open face of the latter a BH group in the α position to a CMe fragment forms a B–H⇀Mo exopolyhedral bond, while the boron atom β to the CMe groups in the pentagonal ring carries a CH₂C₆H₄Me-4 substituent. The molybdenum atom is ligated by a CO molecule and the indenyl group. The n.m.r. data (¹H, ¹³C-{¹H}, ¹¹B-{¹H}, and ³¹P-{¹H}) for the new compounds are reported and discussed.