ETHOXYCARBONYL-METHYL, CYANO-METHYL AND METHOXY-METHYL COMPLEXES OF NICKEL(II) AND THEIR CARBONYLATION REACTIONS

The oxidative addition of ClCH2CO2Et, ClCH2CN and BrCH2OMe to [Ni(cod)2] (cod = cycloocta-1,5-diene), in the presence of 2 equivalents of PMe3, affords the beta-functionalized nickel(II) methyl derivatives trans-[Ni(CH2R)X(PMe3)2] (R = CO2Et, X = Cl 1; R = CN, X = Cl 2; R = OMe, X = Br 3). The interaction of these complexes with carbon monoxide has been studied. The methoxymethyl derivative 3 forms a stable acyl of composition trans-[Ni{C(O)CH2OMe}Br(PMe3)2] 7, but for the ethoxycarbonylmethyl complex 1 the corresponding acyl 8 forms reversibly and, although stable as a solid, only exists in solution under an atmosphere of carbon monoxide. No stable acyl has been observed from the reaction of 2 with CO; only decomposition occurs. Stable 18-electron alkyl and acyl cyclopentadienyl derivatives of composition [Ni(CH2R)(eta-C5H5)(PMe3)] (R = CO2Et 4; CN 5, or OMe 6) and [Ni{C(O)CH2R}(eta-C5H5)(PMe3)] (R = OMe 9 or CO2Et 10) are easily obtained upon reaction of the above 16-electron complexes with Na(C5H5). The new compounds have been fully characterized by analytical and spectroscopic (IR and H-1, C-13 and P-13 NMR) methods.