Properties of complexes with cobalt-carbon bonds formed by reactions of aliphatic free radicals with nitrilotriacetate-cobalt(II) in aqueous solution. A pulse radiolysis study

The reactions of the aliphatic free radicals ^.R [^.R = ^.CH₃, ^.CH₂OH, ^.CH(CH₃)OH, ^.C(CH₃)₂OH, ^.CH(CH₃)OC₂H₅, ^.CH₂CO₂^- and CO₂^.-] with Co^II(nta)(H₂O)₂^- in aqueous solutions yield the unstable transients (nta)Co^III-R(H₂O)^- with cobalt-carbon σ bonds. The complexes with ^.R = ^.CH₃, ^.CH₂OH, ^.CH(CH₃)OH, ^.C(CH₃)²OH and ^.CH(CH₃)OC₂H₅ decompose via homolytic cleavage of the cobalt-carbon bond. The kinetics of reaction of these free radicals with (nta)Co^III-R(H₂O)^- are reported. The only organic products of the latter reactions are the dimers R-R for ^.R = ^.CH₃ and ^.CH₂OH, whereas a mixture of disproportionation products and dimers is formed for ^.R = ^.CH(CH₃)OH and ^.C(CH₃)₂OH. For ^.R = ^.CH₂OH, ^.CH(CH₃)OH and ^.C(CH₃)₂OH the pK_a values for the acidic dissociation of the alcoholic group in the complexes are reported. For ^.R = ^.CH₂OH the activation parameters for the homolytic dissociation of the cobalt-carbon bond and the acidic dissociation are reported. The ultraviolet-visible spectra of all the transients are reported.