Fischer-type tungsten acyl (carbeniate), carbene and carbyne complexes bearing C5-attached thiazolyl substituents: interaction with gold(i) fragments

Abstract

2-(1-Piperidinyl)thiazole and 2-phenylthiazole were deprotonated at C5 of the thiazole rings and both reacted with [W(CO)₆] to form Fischer-type tungsten carbeniate complexes 1a and 1b of the type [(CO₅)WC(O){}] (R = 1-piperidinyl for 1a and phenyl for 1b). Reaction of carbeniate 1b with [(Ph₃P)AuCl] afforded by acyl ligand transfer a tungstenoxycarbene complex of gold(I), [(Ph₃P)AuC{OW(CO)₅}{}] (2), in which the W(CO)₅ fragment remains coordinated to the acyl oxygen atom. Alkylation of 1a and 1b with [Me₃O][BF₄] afforded the carbene complexes [(CO)₅WC(OMe){}], 3a and 3b. A rare example of a hydroxycarbene complex of 1a stabilised by a hydrogen bond to 1a, [NMe₄][{}C{W(CO)₅}OH...(O)C{W(CO)₅}{}], 4, (R = 1-piperidinyl) was crystallised while attempting to prepare 3a by a different route. Reaction of 3b with [ClAu(tht)] (tht = tetrahydrothiophene) furnished the corresponding alkoxycarbene gold(I) complex [ClAuC(OMe){}], 5. Subsequent reaction of 1a and 1b with bis(trichloromethyl)carbonate and pyridine yielded the carbyne complexes [Cl(CO)₂(py)₂WC{}], 6a and 6b. Reaction of 6a with [ClAu(tht)] afforded an unstable addition compound, 7, in which the gold atom is coordinated to the formal carbyne triple bond. Interaction between gold and the proton of the thiazole ring in this complex was observed by variable temperature NMR. The crystal and molecular structures of complexes 1a, 1b, 2, 3b, 4, 5, 6a and 6b were all determined by single crystal X-ray diffraction.