Laser flash photolysis of [CpM(CO) 3 ] 2 (M = W, Mo, and Cr) provides a convenient source of CpM(CO) 3 [ b u l l ] , an organometallic free radical with 17 valence electrons. It is a transient and highly reactive species. Depending on the circumstances and the other reagents present, the radical will dimerize, undergo halogen and hydrogen atom abstraction reactions, and electron transfer reactions. With tetramethyl-phenylenediamine, there is a cyclic process of electron transfer steps, the net result of which is the catalyzed disproportionation of the metal radical.