Photochemical reactions between [Mn 2(CO) 8L 2] (L = CO, PBu 3, PEt 3, P(OMe) 3, P(OPh) 3, PPh 3) and alkyl halides (RX) yield both alkyl and halo complexes, [MnR(CO) 4L] and [MnX(CO) 4L], in equimolar quantities. Kinetic and quantum yield studies suggest that these reactions proceed by a radical chain pathway involving CO dissociation from the dinuclear complex and metal—metal bond homolysis of the coordinatively unsaturated dinuclear intermediate.