CO-loss and geometric isomerization in the frozen matrix photochemistry of cis-Fe(CO)4X2, where X=Br and I, cis-[Et4N][Mn(CO)4Br2], cis-Mn(CO)4(PBu3)Br, and Mn(CO)3(PBu3)2Br

Photolysis of cis-Fe(CO)4X2, where X=Br and I, results in low energy, facile rearrangement to the trans isomer with no evidence of CO-loss. In contrast, the isoelectronic cis-Mn(CO)4Br2 anion exhibits CO-loss upon photolysis with only weak evidence for the trans isomer. The photolysis of Mn(CO)5Br, Mn(CO)4Br(PBu3) and Mn(CO)3Br(PBu3)2 have also been examined in frozen matrices.