STEPWISE PRODUCTION OF A TUNGSTEN(0)-DIETHYLAMINOCARBINE COMPLEX FROM ETHYLISOCYANIDE PRECURSORS

An effective route to the W0-diethylaminocarbyne complex Cp(CO)(EtNC)W = CNEt2 (5) (Cp = eta-5-C5H5) is reported starting from the easily accessible, isomeric mixture of the W(II)-isocyanide compounds cis- and trans-CpW(CO)2(EtNC)I (1a, 1b). Thus oxidative decarbonylation of 1a/1b with one equivalent of I2 results in the quantitative formation of the W(IV) complex CpW(CO)(EtNC)(I)3 (2). Subsequent reductive elimination of two iodide ligands in 2 with Na/Hg leads in the presence of EtNC to an isomeric mixture of the W(II)-compounds cis- and trans-CpW(CO)(EtNC)2I (3a, 3b), the formal carbonyl substitution products of 1a and 1b, in high yield, Further reduction of 3a/3b is achieved with Na powder and yields the electron-rich W0-metallate Na[CpW(CO)(EtNC)2] (4) in quantitative yield. Finally ethylation of 4 with Et3OBF4 occurs exclusively at the isocyanide-nitrogen and affords the desired complex 5.