The chemistry of cycloheptatrienyl complexes of molybdenum and tungsten: synthesis and redox chemistry of some phosphine- and phosphite-substituted halide and acetonitrile derivatives

Abstract

Reaction of [Mo(η-C 6H 5Me)(η-C 7H 7)][PF 6] (C 6H 5Me = toluene) with two equivalents of P(OMe) 3 in refluxing acetonitrile affords [Mo(NCMe){P(OMe) 3} 2(η-C 7H 7)][PF 6], which is a precursor for the neutral complex [MoI{P(OMe) 3} 2(η-C 7H 7)] ( 2) and the radical cation [MoCl{P(OMe) 3} 2(η-C 7H 7)][PF 6] ( 3). Treatment of [WI(CO) 2(η-C 7H 7)] with PPh 3 gives [WI(CO)(PPh 3)(η-C 7H 7)] ( 6), which is a starting material for the synthesis of [W(CO)(dppe)(η-C 7H 7)][PF 6] (dppe = Ph 2PCH 2CH 2PPh 2) and hence [W(NCMe)(dppe)(η-C 7H 7)][PF 6] ( 9). Reaction of 9 with LiCl gives a mixture of [WCl(dppe)(η-C 7H 7)][PF 6] ( 14) and [WCl(dppe)(η-C 7H 7)]. Cyclic voltammetric studies on 2, 3, 6, 9, [Mo(NMe)(dppe)(η-C 7H 7)][PF 6] ( 10), and 14 reveal reversible one-electron transfer processes, and [MoI{P(OMe) 3} 2(η-C 7H 7)][BF 4] ( 4), [MoCl{P(OMe) 3} 2(η-C 7H 7)] ( 5) and [M(NCMe)(dppe)(η-C 7H 7)][PF 6] 2 ( 11, M = W; 12, M = Mo) have been isolated by use of chemical redox reagents. The radicals 3, 4, 11, 12 and 14 have been studied by ESR spectroscopy.