The synthesis of the tripodal phosphine CH3C{CH2P(m-CF3C6H4) 2}3 and its rhodium coordination chemistry

Article abstract of DOI:10.1016/s0020-1693(97)06115-x

The new tripodal phosphine CH₃C{CH₂P(m-CF₃C₆H₄) ₂}₃, CF₃PPP, was prepared by reacting CH₃C(CH₂Br)₃ with Li⁺P(m-CF₃C₆H₄)₂ ^-, the latter being best obtained by adding Li⁺NⁱPr₂^- to PH(m-CF₃C₆H₄)₂. The rhodium complexes [RhCl(CO)(CF₃PPP)], [Rh(LL)(CF₃PPP)](CF₃SO₃) (LL=2 CO or NBD), [RhX₃(CF₃PPP)], [RhX(MeCN)₂(CF₃PPP)](CF₃SO₃) ₂ (X=H and Cl), [RhCl₂(MeCN)(CF₃PPP)](CF₃SO₃) and [Rh(MeCN)₃(CF₃PPP)](CF₃SO₃) ₃ were prepared and characterized. The X-ray crystal structure of [Rh(NBD)(CF₃PPP)](CF₃SO₃) is reported. The lower oxygen sensitivity of the CF₃PPP rhodium(I) complexes, relative to the corresponding species with the parent ligand CH₃C(CH₂PPh₂)₃, is attributed to the higher effective nuclear charge on the metal centers caused by the presence of the six CF₃ substituents on the terdentate phosphine. A similar effect may be responsible for the easier hydrolysis of the CF₃PPP-containing, cationic rhodium(III) complexes relative to the corresponding compounds of the parent ligand.