The kinetics of the reactions of [superscript]•C[subscript]2H[subscript]5 with Co(NH[subscript]3)[subscript]5X[superscript]2+, Ru(NH[subscript]3)[subscript]5X[superscript]2+, and Co(dmgH)[subscript]2(X) (Y) (X = Br, Cl, N[subscript]3, SCN; Y = H[subscript]2O, CH[subscript]3CN) complexes were studied using laser flash photolysis of ethylcobalt complexes. The kinetics were obtained by the kinetic probe method using ABTS[superscript]• - and IrCl[subscript]6[superscript]2-. Some relative rate constants were also determined by a competition method based on ethyl halide product ratios. The products of these reactions are largely (>90%) the ethyl halide and ethyl thiocyanate, substantiating an inner-sphere mechanism. Minor but regular yields of C[subscript]2H[subscript]4 are also found (<10%), suggesting a small contribution from the outer-sphere oxidation of [superscript]•C[subscript]2H[subscript]5;The kinetics of colligation reactions of a series of alkyl radicals with [beta]-Ni(cyclam)[superscript]2+ were studied using laser flash photolysis of alkylcobalt complexes. The kinetics were obtained by employing the kinetic probe competition method (with ABTS[superscript]• - or MV[superscript]• +);The kinetics of the unimolecular homolysis of a series of RNi(cyclam)H[subscript]2O[superscript]2+ were studied using ABTS[superscript]• -, MV[superscript]• + or oxygen as radical scavenging agents. Activation parameters were obtained for the unimolecular homolysis of C[subscript]2H[subscript]5Ni(cyclam)H[subscript]2O[superscript]2+;The colligation and homolysis rate constants are strongly influenced by steric and electronic factors. Kinetic and thermodynamic data obtained from these reactions were compared with those for other [sigma]-bonded organometallic complexes;The kinetics of the unimolecular homolysis of a series of RNi(cyclam)H[subscript]2O[superscript]2+ complexes were studied by monitoring the formation of the oxygen insertion product RO[subscript]2Ni(cyclam)H[subscript]2O[superscript]2+. The rate constants for the reactions of alkyl radicals with oxygen, k[subscript] O, were obtained from the analysis of the homolysis rate equation which contains the known rate constants for the colligation of R[superscript]• with [beta]-Ni(cyclam)[superscript]2+, k[subscript] col, and for the homolysis of RNi(cyclam)H[subscript]2O[superscript]2+, k[subscript] hom. The higher rate constants for the reactions of alkyl radicals with oxygen in solution, as compared with those measured in the gas phase, were discussed.