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

Treatment of [PtCl2(SEt2)(2)] or [RhCl3(SEt2)(3)] with 2-LiC6H4PPh2 gives four-membered ring chelate arylplatinum(II) or arylrhodium(III) complexes [Pt{C6H4(PPh2)-2}(2)] and [Rh{C6H4(PPh2)-2}(3)], respectively, whereas the corresponding reaction of [IrCl3(SEt2)(3)] gives IrCl{C6H4(PPh2)-2}(2)(PPh3)] 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}{eta(1)-C6H4(PPh2)-2}(L)] [L = PPh3, P(OPh)(3), P(OMe)(3) or (BuNC)-N-t] and [Pt{eta(1)-C6H4(PPh2)-2}(2)(R2PCH2CH2PR2)] (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 cis-[PtI(Me){C6H4(PPh2)-2}(2)] have been determined by X-ray crystallography.