Abstract A chlorine-free catalyst, prepared in situ from Cu (II) acetate and 2, 2'-bipyrimidine, can be used for the oxidative carbonylation of methanol to dimethyl carbonate. In situ high pressure IR and NMR spectroscopic studies suggest the formation of [Cu (2, 2'- bipyrimidine)(CO)-(OMe)] as one of the key intermediates. The catalytic performance of the 2, 2'-bipyrimidine-modified Cu-catalyst is similar to the CuCl-based system. The chlorine ...