Kinetics of axial ligand exchange in ruthenium(II) tetraphenylporphyrin complexes

Abstract

Variable-temperature 1H n.m.r. lineshape analysis has been used to determine the kinetics of axial ligand exchange in 1-methylimidazole and 4-t-butylpyridine complexes of benzyl isocyanide(tetraphenylporphyrinato)ruthenium(II). The results are compared with those for other ruthenium(II) porphyrins and for ruthenium(II) complexes of simple amine ligands, and discussed in terms of π bonding and anti-symbiotic effects. The cis effect of tetraphenylporphyrin is much less in ruthenium(II) complexes than in their iron(II) analogues. This is considered as definite evidence for the formation of a high-spin intermediate in the latter case.