Oxidative carbonylation of primary amines to ureas using tungsten carbonyl catalysts

The iodo-bridged tungsten(IV) dimer [(CO)(2)W(NPh)I-2](2) (1) has been demonstrated to be a catalyst for the oxidative carbonylation of primary amines to 1,3-disubstituted ureas. The amine complexes (CO)(2)I2W(NPh)(NH2R) [R = n-Bu (2a), R = n-Pr (2b), R = t-Bu (2c)] and [(CO)(2)IW(NPh)(NH2R)(2)](+) [R = n-Bu (4a), R = n-Pr (4b)] have been isolated from reactions of 1 with primary amines. Complexes 2a-c and 4a-b have been shown to lie along the pathway to the catalytically active species. In addition, it has been determined that primary amines can be oxidatively carbonylated to 1,3-disubstituted ureas using W(CO)(6) as catalyst and I-2 as the oxidant.