Complexes of functional phosphines. Part 11. β-Ketophosphine complexes of nickel, palladium, and platinum. Crystal structures of trans-[NiX2(HL)2][X = Cl or I, HL = Ph2PCH2C(O)Ph]

The synthesis and spectroscopic properties (1H and 31P n.m.r., i.r.) of complexes containing the β-ketophosphine Ph2PCH2C(O)Ph (HL) are described. In [NiX2(HL)2][X = Cl (1), Br, or I (3)], [PdCl2(HL)2](4), [PtCl2(HL)2](5), and [{PdCl(µ-Cl)(HL)}2](6), HL behaves as a P-bonded monodentate ligand whereas in the cationic complexes [Pd(HL)2][BF4]2 and [{Pd(µ-Cl)(HL)}2][CF3SO3]2 it acts as a P,O chelate. The crystal structures of (1) and (3) have been determined using single-crystal X-ray diffraction methods. Compounds (1) crystallises in space group P21/n, with a= 10.079(3), b= 11.510(3), c= 15.411(3)A, β= 93.42(2)°, and Z= 2. Compound (3) crystallises in space group P21/c, with a= 9.283(1), b= 10.261(1), c= 19.318(1)A, β= 96.20(1)°, and Z= 2. The structures have been refined to R 0.050 (R′ 0.060) for (1) and to R 0.032 (R′ 0.041) for (3). The geometries of these complexes are essentially identical although the ν(CO) frequencies of these complexes are significantly different [1 662 cm–1 for (1) and 1 620 cm–1 for (3)]; the nickel atom occupies a centre of symmetry and has thus a square-planar environment. Although the ketone group is bent towards the nickel atom, no significant Ni–O bonding interaction occurs, as deduced from the Ni–O distances [3.230(4)A in (1) and 3.231(1)A in (3)]. In refluxing toluene (1), (4), or (5) lead to the phosphine–phosphinite complexes cis-[[graphic omitted]Ph2}](M = Ni, Pd, or Pt). Treatment of (1), (4), or (5) with base gives the enolato-complexes cis-[[graphic omitted]Ph}2](M = Ni, Pd, or Pt). Reaction of (6) with NaH affords the binuclear complex [{P[graphic omitted]Ph]}2]. The latter reacts with PPh3 to give cis-[P[graphic omitted]Ph}(PPh3)], and with Ph2PCH2CH2PPh2–TlPF6 to give [P[graphic omitted]Ph}(Ph2PCH2CH2PPh2)]PF6. The P–O coupling products [N[graphic omitted]R}](R = Cl or Ph) are obtained by reaction of the complex [N[graphic omitted]Ph}2] with PCl3 and PPhCl2 respectively, and shown to have a five-co-ordinate structure. The square-planar P,P,P complex [N[graphic omitted]Ph}]PF6 results from reaction of [N[graphic omitted]Ph}] with TIPF6.