NUCLEOPHILIC ACTIVATION OF COORDINATED CARBON-MONOXIDE - REACTION OF TUNGSTEN HEXACARBONYL WITH METHOXIDE SALTS

Kinetics studies of the reactions of [Na+] [OCH3-] and [((C6H5)3P)2N+] [OCH3-] with W(CO)6 are reported. The preparation of acetonitrile sol utions Of ((C6H5)3P)2NOCH3, a convenient source of solubilized methoxi de ion in aprotic media, is described. Second-order rate constants (73 0 +/- 130 M-1 s-1 and 743 +/- 61 M-1 s-1) and equilibrium constants (3 200 +/- 300 M-1 and 1400 +/- 200 M-1) for the formation of the methoxy carbonyl complexes [M+] [W(CO)5CO2CH3-] (M+ = Na+ and ((C6H5)3P)2N+, r espectively) at 25-degrees-C are several orders of magnitude lower tha n those reported for the formation of group VIII methoxycarbonyl compl exes. Addition of trace quantities of water to THF/CH30H solutions of [Na+] [W(CO)5CO2CH3-] suprisingly resulted in the formation Of W(CO)6 and not the expected metal hydride HW(CO)5-. These observations are co nsistent with the previously reported variation in catalytic activity of group VI and VIII metal carbonyl compounds for the water gas shift reaction.