Synthesis and reactions of tungsten(II) norbornadiene (nbd) complexes. The crystal and molecular structure of [WBr(SC6F5)(CO)2(nbd)]

Abstract

The reaction of [WBr₂(CO)₂(nbd)]1(nbd norbornadiene) with TI(C₅H₅) gave a monocarbonyl derivative [WBr(CO)(nbd)(η⁵-C₅H₅)]2. With TI(O₂CMe) and TI[O(S)CMe]. complex 1 gave monosubstituted derivatives[WBr(O₂CMe)(CO)₂(nbd)]3a and [WBr{O(S)CMe}(CO)₂(nbd)]3b which appear to be seven-co-ordinate according to IR data. In contrast 1 and TI(SC₆F₅)(1:1 molar ratio) gave the six-co-ordinate complex [WBr(SC₆F₅)(CO)₂(nbd)]4. An X-ray diffraction study of 4 established that it has a distorted-octahedral structure with trans W–CO bonds approximately perpendicular to a plane containing the W. Br and S atoms and the midpoints of the nbd CC bonds. Simple electronic arguments provide a rationalisation of many of the structural features of 4. Reaction of 1 with 2 molar equivalents of TI(SC₆F₅) gave the bis(thiolate) derivative [W(SC₆F₅)₂(CO)₂(nbd)]5 again with a trans arrangement of CO ligands. The reactions of 5 with L =PEt₃. PMe₂Ph or P(OMe)₃ gave the six-co-ordinate complexes [W(SC₆F₅)₂(CO)₂L₂]6 which exist in two isomeric forms, red or green. Dynamic NMR studies have been used to characterise the isomeric behaviour and fluxional processes in the complexes.