Mononuclear η6-p-cymeneosmium(II) complexes and their reactions with Al2Me6 and other methylating reagents

Abstract

An improved-yield synthesis of the η⁶-p-cymeneosmium(II) chloride complex [(p-MeC₆H₄CHMe₂)₂Os₂Cl₄](1) has allowed the development of the chemistry of the mononuclear complexes, [(p-MeC₆H₄CHMe₂)OsLCl₂](2)[L = CO, CNCMe₃, Me₂SO, PMe₃, PPh₃, or P(OPh)₃]. These gave [(p-MeC₆H₄CHMe₂)OsL(Me)Cl](3)(L = CO, CNCMe₃, Me₂SO, or PMe₃) with Al₂Me₆. Reaction of [(p-MeC₆H₄CHMe₂)Os(Me₂SO)(Me)Cl] with L′[PPh₃ or P(OPh)₃] gave the complex [(p-MeC₆H₄CHMe₂)OsL′(Me)Cl]. Al₂Me₆ reacted with [(p-MeC₆H₄CHMe₂)OsL′Cl₂] to give chiefly the ortho-metallated complexes [(p-MeC₆H₄CHMe₂)Os{PPh₂(o-C₆H₄)}X](5)(X = Cl), (6)(X = Me), and [(p-MeC₆H₄CHMe₂)Os{P(OPh)(OC₆H₄-o)₂}](8); however, the triphenylphosphine complex also gave the mono- and the di-methyl complexes [(p-MeC₆H₄CHMe₂)Os(PPh₃)(Me)X](X = Cl or Me). The complexes have been characterised by their i.r., ¹H, ¹³C, and ³¹P n.m.r. spectra and their e.i. mass spectra. The p-cymene ring remains η⁶-bonded throughout these reactions and appears quite difficult to displace.