Reactions of ruthenium formyl and related complexes with nitroxide spin traps

Abstract

Reactions of the complexes trans-[Ru(CHO)(CO)(dppe)₂][SbF₆](dppe = Ph₂PCH₂CH₂PPh₂), cis-[Ru(CHO)(CO)(dppm)₂][SbF₆](dppm = Ph₂PCH₂PPh₂), or trans-[Os(CHO)(CO)(dppe)₂][SbF₆] with Bu^tNO give Bu^t₂NO˙ and trans-[M(Bu^tNO)(CO)(P–P)₂]˙⁺(M = Ru, P–P = dppe or dppm; M = Os, P–P = dppe), the structures of which have been elucidated by e.s.r. and labelling (¹³C, ²H) studies. cis- or trans-[RuH(CO)(dppe)₂]⁺ gives only Bu^t₂NO˙ whilst trans-[Ru(CO)₂(dppe)₂]²⁺ gives a mixture of trans-[Ru(CO)₂(dppe){Ph₂PCH₂CH(Bu^tNO)PPh₂}]˙²⁺ and a radical with the trap bound to a carbonyl carbon atom. The decomposition products of cis-[Ru(CHO)(CO)(dppm)₂]⁺ give a radical with the trap bound to the back-bone carbon atom of a chelating dppm ligand, whilst dppe and dppm both give radicals where the Bu^tNO group is bound to a phosphorus atom. The mechanisms of some of these reactions are discussed.