Synthesis and nuclear magnetic resonance studies of co-ordinatively unsaturated alkyne complexes of tungsten(II)

Abstract

[{WBr₂(CO)₄}₂] reacts with alkynes RCCR′(R = R′= Me, Et, or Ph) and PhCCMe to give dimeric complexes [{WBr₂(CO)(RCCR′)₂}₂]. These react with nucleophiles (L) to give monoalkyne complexes [WBr₂(CO)L₂(RCCR′)][L = CNBu^t, P(OMe)₃, or PPh₃; R = R′= Me or Ph; R = Me, R′= Ph) which exist in cis and/or trans isomeric forms and which exhibit alkyne ‘propeller rotation’ according to ¹H and ³¹P n.m.r. studies. The isolation of [WBr₂(CO)(CNBu^t)(MeCCMe)₂] indicates that the reactions proceed via monomeric bis-alkyne intermediates.