Reactions between [MoCl(CO)3(cp)] (cp = ?5-C5H5) and Tl(SC6F5) afford the fully characterised complexes [TlMo(SC6F5)2L2(cp)] [L = CO (1) or SC6F5(2)]. Complex (2) is formed by an oxidative substitution process and can also be obtained by reactions of Tl(SC6F5) with other molybdenum- (II), -(III), or -(IV) precursors. Molecular structures of crystalline complexes (1) and (2) have been determined by X-ray diffraction. Complex (1) contains units of [(cp) (OC)2Mo(µ-SC6F5)2Tl] in which TlI is co-ordinated by two S atoms (mean Tl-S 3.015 Å) and is close to one ortho-F atom of each C6F5ring (mean Tl ? F 3.095 Å); intermolecular Tl ? S interactions between individual units of (1) give this material an extended-chain structure in the solid state. Crystalline (2) contains discrete molecular units of [(cp) Mo(µ-SC6F5)4Tl] in which TlI is co-ordinated by four S atoms (mean Tl-S 3.272 Å); these four S atoms, four closely associated o-F atoms, one from each C6F5ring (mean Tl ? F 3.062 Å), and the Mo atom [Mo ? Tl 3.402(3) Å] define a cavity in which the TlI is situated. The anion [Mo(SC6F5)4(cp)]- in (2) is acting as a polydentate ligand to Tl+. Variable-temperature 19F n.m.r. studies on complexes (1) and (2) in toluene, dichloromethane, and acetone solutions establish the occurrence both of restricted rotation of the C6F5 groups and of solvent-dependent ionic dissociation into Tl+ and [Mo(SC6F5)2L2(cp)]-. Significant ionisation occurs in the polar solvent acetone, and this is supported by conductivity measurements. Reactions of complex (1) with tertiary phosphines give products [Mo(SC6F5)(CO)2L(cp)] [L = PMe2Ph (3), PMePh2 (4), or PPh3 (5)] with 'four-legged piano-stool' geometry; these complexes are principally cis isomers although minor amounts of trans isomers were detected by 1H n.m.r. spectroscopy in solutions of (3) and (5). Reaction of complex (2) with PPh3 affords a species [TlMo(SC6F5)4(PPh3)2(cp)] which variable-temperature 1H, 19F, and 31P n.m.r. studies show to exist as a mixture of two interchanging forms in solution.
|Number of pages||11|
|Journal||Journal of the Chemical Society, Dalton Transactions|
|Publication status||Published - 1989|