CO bond activation in carbene-C,O chelate tungsten(II) complexes — MeX elimination in the reaction of [X2(CO)3WC(C6H4OMe-o)OMe] with L2 (L2=dppe, 2 PMe3)

The heptacoordinated dihalogeno carbene-C,O chelate carbonyl complexes [X2(CO)3Me-o)OMe] (3a–c, X=Cl (a), Br (b), I (c)) react with Ph2PCH2CH2PPh2 (dppe) via CO and MeX elimination to give the aryloxycarbene-C,O chelate complexes [X(CO)2(dppe))OMe)OMe] (7a–c). The analogous reactions of 3a–c with two equivalents of PMe3 and that of the monophosphine complexes [X2(CO)2(PMe3)Me-o)OMe] (9a–c) with one equivalent of PMe3 likewise afford aryloxycarbene-C,O chelate complexes [X(CO)2(PMe3)2)OMe] (8a–c). In contrast to 8a and 8b the structure of 8c is dynamic.