Reactions of the molybdenum bis(alkyne) complex [Mo(SC6F5)(F3CCCCF3)2(η5-C5H5)] with alkynes leading to isomeric and fluxional η4-butadienyl complexes
Abstract
Reactions of the bis(hexafluorobut-2-yne) complex [Mo(SC6F5)(F3CCCCF3)2(η5-C5H5)]1 with alkynes RCCR′ give the novel η4-butadienyl complex prone-[Mo{η4-C(CF3)C(CF3)CRCR(SC6F5)}(F3CCCCF3)(η5-C5H5)]2(R = R′= Me; R = H, R′= Me or Ph; R = Me, R′= CO2Me) which undergoes isomerisation via an η2-C,C vinyl intermediate [Mo{η3-C(CF3)C(CF3)CRCR′(SC6F5)}(F3CCCCF3)(η5-C5H5)]3(R = R′= Me, Et or Ph; R = Me, R′= Co2Me or Ph; R = H, R′= Ph) to the supine isomer 4(R = R′= Me or Et; R = Me, R′= CO2Me or Ph; R = H, R′= Me or Ph) followed by a novel 1,4 thiolate migration to give supine-[Mo{η4-CR′CRC(CF3)C(CF3)(SC6F5)}(F3CCCCF3)(η5-C5H5)]5(R = R′= Ph; R = Me, R′= Ph). Fluorine-19 NMR studies established that with PhCCPh 3 and 5 exist in solution as an equilibrium mixture. With PhCCMe exchange between 3, 4 and 5 is faster which allowed study by dynamic 19F NMR and spin-saturation-transfer experiments.