The carbene-C,N chelate tetracarbonyl tungsten complex [(CO)4WC(Ph)NHC5H4N-o] (4), obtained from [(CO)5WC(Ph)OMe] (3) and o-aminopyridine, reacts with iodine by oxidative decarbonylation to give a single isomer of the carbene-C,N chelate tricarbonyl dihalogeno tungsten(II) complex [(CO)3I2WC(Ph)NHC5H4N-o] (5). The analogous reaction of 4 with bromine affords two interconverting isomers of [(CO)3Br2WC(Ph)NHC5H4N-o] (6). The oxidative decarbonylation of the carbene-C,O chelate tetracarbonyl tungsten complex [(CO)4WC(OMe)C6H4OMe-o] (1) with tetrachloro-o-benzochinone yields the first carbene-C,O chelate tricarbonyl-o-benzochinone tungsten(II) complex 8. The structures of 5 and of [(CO)4I2WC(OMe)C6H4OMe-o] (2c) were established by X-ray structural analyses.