Complexes of platinum(II), platinum(IV), rhodium(III) and iridium(III) containing orthometallated triphenylphosphine

Abstract

Treatment of [PtCl2(SEt2)2] or [RhCl3(SEt2)3] with 2-LiC6H4PPh2 gives four-membered ring chelate arylplatinum(n) or arylrhodium(m) complexes [Pt{C6H4(PPh2)-2}3 and [Rh {C6H4(PPh2)-2}3], respectively, whereas the corresponding reaction of [IrCl3(SEt2)3] gives JrCl{C6H4(PPh2)-2}2(PPh 3)] arising from cleavage of an Ir-C6H4(PPh2) bond. The chemistry of [Pt{C6H4(PPh2)-2}2] is dominated by the lability of the Pt-P bonds, which are displaced sequentially by ligands at room temperature to give complexes containing monodentate C6H4(PPh2), i.e. [Pt{C6H4(PPh2)-2} {n-C6-H4(PPh2)-2}(L)] [L = PPh2, P(OPh)3, P(OMe)3 or Bu'NC] and [Pt{n'-C6H4(PPh2)-2}2(R 2PCH2CH2PR2)] (R = Ph, Me or Cy). In the cases of Me2PCH2CH2PMe2 and Cy2PCH2CH2PCy2, binuclear intermediates can be detected in which these ligands bridge two platinum atoms. Oxidative addition of methyl iodide or iodine to [Pt{C6H4(PPh2)-2}2] gives initially platinum(iv) complexes [PtI(R){C6H4(PPh2)-2}2] (R = Me or I) in which the added groups are mutually trans; in the final, stable products the added groups and the phosphorus atoms are, separately, mutually cis. Oxidative addition of bromine to [Pt{C6H4(PPh2)-2}2] gives initially trans-[PtBr2{C6H4(PPh2)-2} 2] but subsequent oxidation and hydrolysis at the phosphorus atoms gives chelate tertiary phosphine oxide complexes of platinum(iv). The molecular structures of [Rh{C6H4(PPh2)-2}3] and rö-[PtI(Me){C6H4(PPh2)-2}2] have been determined by X-ray crystallography.