Complexes of the platinum metals. Part III. Arylazo and aryldi-imine derivatives

Abstract

Arylazo derivatives RuX₃(N₂Ar)(PPh₃)₂, OsBr₃(N₂Ar)(PPh₃)₂, and RhX₂(N₂Ar)(PPh₃)₂ have been prepared by reacting diazonium tetrafluoroborates with the preformed metal phosphine complexes RuX₂(PPh₃)₃, OsBr₂(PPh₃)₃, and RhX(PPh₃)₃ respectively then adding the appropriate lithium halide to the reaction mixture. The ruthenium and rhodium arylazo complexes are also conveniently prepared by a single step procedure involving addition of the appropriate metal trihalide and 1,3-diaryltriazene to an ethanolic solution of a triarylphosphine. These latter reactions are thought to involve diazonium cations generated in situ by acidolysis of 1,3-diaryltriazene. Products obtained on reacting RhHCl₂(PPh₃)₃ with diazonium tetrafluoroborates and lithium chloride, and previously formulated by other workers as solvated arylazo derivatives RhCl₂(N₂Ar)(PPh₃)₂(sol)_x(x=½–1; sol = CH₂Cl₂ or CHCl₃), are reformulated as aryldi-imine derivatives RhCl₃(NHNAr)(PPh₃)₂. Similar reactions of the hydrides MHCl(CO)(PPh₃)₃ and MH₂(CO)(PPh₃)₃(M = Ru or Os) with diazonium salts afford new aryldi-imine derivatives of ruthenium and osmium. The interconversion of arylazo and aryldi-imine complexes is reported and the carbonylation and hydrogenation of some of these products are described. The structure of the aryldi-imine ligands is confirmed by ¹H n.m.r. spectroscopy using ¹⁵N labelled ligands. Structural and spectroscopic analogies between isoelectronic arylazo and nitrosyl complexes are discussed.