Synthesis and rearrangement reactions of dihalogenotris- and dihalogenotetrakis-(tertiary phosphine)ruthenium(II) compounds

Abstract

The reactions of [RuCl₂(PPh₃)₄] with several tertiary phosphine ligands in various solvents have been examined. Whereas prolonged reaction in ethanol or dichloromethane leads to the well known ionic dimers [Ru₂Cl₃L₆]Cl(L = PEtPh₂, PEt₂Ph, or PMe₂Ph), reaction in non-polar solvents such as hexane or light petroleum (b.p. 60–80 °C) produces neutral complexes. For L = PEtPh₂, [RuCl₂(PEtPh₂)₃] has been isolated although this readily converts to the triple chloride-bridged dimer [(Ph₂EtP)₃RuCl₃RuCl(PEtPh₂)₂] in non-polar and [Ru₂Cl₃(PEtPh₂)₃]Cl in polar media. For L = PEt₂Ph and PClPh₂, only [L₃RuCl₃RuClL₂] can be isolated although ³¹P n.m.r. studies indicate the presence of [RuCl₂(PEt₂Ph)₃] in the reaction mixture. For L = PMe₂Ph, cis-[RuCl₂2(PMe₂Ph)₄] is formed although this very readily rearranges to [Ru₂Cl₃(PMe₂Ph)₆]Cl. Preliminary studies indicate that similar compounds are formed from [RuBr₂(PPh₃)₄]. All these compounds {including [RuCl₂(PPh₃)_{3 and 4}]} have been extensively studied by variable-temperature ³¹P n.m.r. spectroscopy and an overall mechanism for the rearrangement reactions of all tertiary phosphine complexes of type [RuX₂L_{3 or 4}] is proposed.