Alkylidyne(carbaborane) Complexes of the Group 6 Metals. Part 1. Proton-induced Alkylidyne Ligand Migration

Article abstract of DOI:10.1039/DT9920000393

Treatment of carbon monoxide-saturated solutions of the salts 5-C2B9H9Me2)> (R = C6H4Me-4 or Me) at ca. -78 deg C with HBF4*Et2O affords the complexes 5-C2B9H8(CH2R)Me2>>.If these protonation reactions are carried out in the presence of PhCCPh, the alkynetungsten complexes 5-C2B9H8(CH2R)Me2>> are formed via the intermediacy of dicarbonyl species 5-C2B9H8(CH2R)Me2>>.The latter (R = C6H4Me-4) with PMe3 yields the compound 5-C2B9H8(CH2C6H4Me-4)Me2>>.Treatment of 5-C2B9H9Me2)> with HBF4*Et2O in the presence of CNBu^t yields t)2<η⁵-C2B9H8(CH2C6H4Me-4)Me2>>, whereas if PPh3 is used instead of CNBu^t a tricarbonyl species 5-C2B9H8(CH2C6H4Me-4)Me2>> is isolated.However, the latter disproportionates in solution to afford the bis(triphenylphosphine) complex 5-C2B9H8(CH2C6H4Me-4)Me2>>, crystals of which have been analysed by X-ray crystallography.The tungsten atom is η⁵ co-ordinated by the C2B9H8(CH2C6H4Me-4)Me2 ligand and is ligated by two CO and two PPh3 groups, having transoid arrangements.The CH2C6H4Me-4 substituent on the cage is bonded to the boron atom which is in the β site with respect to the two carbons in the open pentagonal CCBBB face of the nido-icosahedral C2B9 fragment.This geometry accounts for the NMR data (1H, 13C-<1H> and 11B-<1H> for all the new complexes reported containing the C2B9H8(CH2R)Me2 cage system.

Full text of DOI:10.1039/DT9920000393

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