Activation of C-H/H-H bonds by rhodium(II) porphyrin bimetalloradicals

Reactivity, kinetic and thermodynamic studies for reactions of a rhodium(II) bimetalloradical with H2, and with the methyl C-H bonds for a series of methyl substrates CH(sub 3)R (R=H, CH(sub 3), OH, C00(sub 6)H(sub 5)) using an m-xylyl diether tethered diporphyrin ligand is reported. The results reveal that bimolecular reactions involving the intramolecular use of two metalloradical centers and preorganisation of the four-centered transition state, result in large rate enhancements.