Dinuclear formamidino and triazenido compounds [{2,6-(Me 2NCH 2) 2C 6H 3} ( p-tolylNYNR)PtHgBrCl] (Y  CH, N) containing a platinum-to-mercury donor bond

Abstract

Complexes [{2,6-(Me 2NCH 2) 2C 6H 3} ( p-tolylNYNR)PtHgBrCl] (Y  CH, N; R  Me, Et, i-Pr) have been prepared by the reaction of [{2,6-(Me 2NCH 2) 2C 6H 3}-PtBr] with [Hg( p-tolylNYNR)Cl]. Similar complexes were obtained, although in lower yields, from exchange reactions of [{2,6-(Me 2NCH 2) 2C 6H 3} (RCO 2)-PtHg(O 2CR)Br] with p-tolylNNN(H)- p-tolyl and p-tolylNC(H)N(H)Et. The proposed structure for these heterodinuclear compounds involves a Pt-to-Hg donor bond which is bridged by a triazenido (Y  N) or a formamidino (Y  CH) group, the five-membered ring thus formed acting as a stabilizing factor. The absence of a subsequent electron transfer reaction is ascribed to the constraints of the terdentate 2,6-(Me 2NCH 2) 2C 6H 3 ligand, which fixes the N-donor atoms in mutual trans-positions. The use of p-tolylNYNR, where R is an alkyl group, results in the formation of two isomers of [{2,6-(Me 2NCH 2) 2C 6H 3} ( p-tolylNYNR)PtHgBrCl] with p-tolyl-N and alkyl-N sites bonded either to Pt or Hg. The relative abundance of these isomers varies systematically with the nature of the group R. It is suggested that the ratio is determined during the formation of the complexes and that both steric and electronic factors are important.