Nucleophilic activation of coordinated carbon monoxide. Reaction of tungsten hexacarbonyl with methoxide salts

Kinetics studies of the reactions of [Na[sup +]][OCH[sub 3][minus]] and [((C[sub 6]H[sub 5])[sub 3]P)[sub 2]N[sup +]][OCH[sub 3][minus]] with W(CO)[sub 6] are reported. The preparation of acetonitrile solutions of ((C[sub 6]H[sub 5])[sub 3]P)[sub 2]NOCH[sub 3], a convenient source of solubilized methoxide ion in aprotic media, is described. Second-order rate constants (730 [plus minus] 130 M[sup [minus]1] and 743 [plus minus] 61 M[sup [minus]1] s[sup [minus]1]) and equilibrium constants (3200 [plus minus] 300 M[sup [minus]1] and 1400 [plus minus] 200 M[sup [minus]1]) for the formation of the methoxycarbonyl complexes [M[sup +]][W(CO)[sub 5]CO[sub 2]CH[sub 3][minus]] (M[sup +] = Na[sup +] and ((C[sub 6]H[sub 5])[sub 3]P)[sub 2]N[sup +], respectively) at 25[degrees]C are several orders of magnitude lower than those reported for the formation of group VIII methoxycarbonyl complexes. Addition of trace quantities of water to THF/CH[sub 3]OH solutions of [Na[sup +]][W(CO)[sub 5]CO[sub 2]CH[sub 3][minus]] surprisingly resulted in the formation of W(CO)[sub 6] and not the expected metal hydride HW(CO)[sub 5][minus]. These observations are consistent with the previously reported variation in catalytic activity of group VI and VIII metal carbonyl compounds for the water gas shift reaction.