Kinetic Studies of the Alkylation of Metal Cyanide Complexes: M(CO)x(L)5-xCN (M = Mn, Re) and CpM‘(CO)x(L)2-xCN (M‘ = Fe, Ru)

Abstract

Reaction rates for the alkylation of Mn(CO)(dppm)(2)CN (dppm = PPh(2)CH(2)PPh(2)), Mn(CO)(2)(tripod)CN [tripod = (PPh(2)CH(2))(3)CCH(3)], Re(CO)(3)(dppm)CN, (eta(6)-C(6)Me(6))Mn(CO)(2)CN, CpFe(dppe)CN (dppe = PPh(2)CH(2)CH(2)PPh(2)), CpRu(dppe)CN, and CpRu(CO)(PPh(3))CN with methyl 4-nitrobenzenesulfonate (MeONs) to produce complexes of the type [L(n)()M-CNMe](+) (-)ONs were investigated in 1,2-dichloroethane (DCE) at 30.0 degrees C. The reactions are first order in both the complex and the alkylating agent, which is consistent with a mechanism that involves nucleophilic attack of the cyanide nitrogen on the methyl of the MeONs. The second-order rate constants (k(2)) correlate approximately with the stretching frequency of the cyanide ligand nu(CN) in the complexes. There is a somewhat better correlation between nu(CN) of the CNCH(3) ligands in the products and k(2). There is also a good correlation between the rate constant (k(2)) and the calculated force constant (k(CO)) for the nu(CO) vibrational mode of the analogous [L(n)()M-CO](+) complex. These correlations appear to be useful for predicting nucleophilicities of metal cyanide complexes of different metals, in different oxidation states, and with ligands exhibiting a range of electronic and steric properties.