SYNTHESES AND REACTIONS OF ETA-2-VINYL COMPLEXES OF MOLYBDENUM AND TUNGSTEN [M(SC6F5)(ETA-2-C(CF3)C(CF3)(PR3))-(CF3C=CCF3)(CP)] AND [MO(ETA-3-C(CF3)C(CF3)(SPRI))-(CF3C=CCF3)(CP)] (CP=ETA-C5H5)

Reactions of bis(hexafluorobut-2-yne) complexes [M(SC6F5)(CF3C = CCF3)2(cp)] (M = Mo, 1a; or W, 1b with tertiary phosphines and phosphites (L) give eta-2-vinyl complexes [M(SC6F5){eta-2-C(CF3)C(CF3)L}(CF3C = CCF3)(cp)] 3 [(M = Mo or W; L = PEt3, PMe2Ph or PMePh2; M = W, L = P(OMe)3] as a result of attack at an alkyne carbon. Several isomeric forms of complexes 3 have been detected by NMR spectroscopy. Reactions of phosphines with the eta-2-C,C vinyl complex [Mo{eta-3-C(CF3)C(CF3)SPr(i)}(CF3C = CCF3)(cp)] 2 in contrast give eta-4-butadienyl derivatives [Mo{C(CF3) = C(CF3)C(CF3) = C(CF3)(SPr(i))}L(cp)] 4 (L = PEt3, PMe2Ph, or MeC = CPPH2) apparently as a result of insertion of the alkyne into the M = C bond of the eta-2-C,C vinyl. A similar complex 4 is obtained when 3 (M = Mo, L = PMe2Ph) is allowed to isomerise in diethyl ether at room temperature. In contrast 3 (M = Mo, L = PMe2Ph) isomerises in refluxing hexane to the tetrakis (trifluoromethyl) cyclobutadiene complex [Mo(SC6F5)-(PMe2Ph){eta-4-C4(CF3)4}(cp)] 9. An alternative isomerisation process is observed in diethyl ether at 18-degrees-C where the product [MoF{eta-3-C(CF2)C(CF3) = C(CF3)C(CF3)(SC6F5)}L(cp)] 8 (L = PEt3 or PMe2Ph) results from linking of two CF3C = CCF3 ligands and a C6F5S group and fluorine transfer from a CF3 to the metal. Fluxional behaviour in complexes 3, 8 and 9 has been studied by F-19 NMR spectroscopy.