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.