Synthesis and Structural Characterisation of Palladium and Group‐12 Metal Complexes with a Hybrid Phosphanylphosphonate Ferrocene Ligand

Abstract

AbstractDiethyl [1′‐(diphenylphosphanyl)ferrocenyl]phosphonate (1) was synthesised by stepwise metallation/functionalisation of 1,1′‐dibromoferrocene and studied as a ligand for palladium(II) and group‐12 metals. Treatment of [PdCl2(cod)] (cod = η2:η2‐cycloocta‐1,5‐diene) with 1 in 1:1 or 1:2 molar ratios gave, respectively, the dinuclear, chloride‐bridged complex [{Pd(μ‐Cl)Cl(1‐κP2)}2] (2) and the mononuclear complex trans‐[PdCl2(1‐κP2)2] (3), where 1 coordinates exclusively through the phosphane function. The reactions between 1 and group‐12 metal bromides MBr2 in a 1:1 molar ratio gave the adducts [MBr2(1)] [M = Zn (4), Cd (5), and Hg (6)], whose crystal structures change considerably with the metal ion. Thus, whereas 4 is a molecular complex with 1 coordinating as an O1,P2‐chelate, its cadmium(II) analogue is a polymer built up from symmetric {CdBr(μ‐Br)}2 units interconnected by pairs of O1,P2‐bridging phosphanylphosphonate ligands. Finally, the mercury(II) complex 6 is a halide‐bridged dimer, [{Hg(μ‐Br)Br(1‐κP2)}2]. However, this compound is structurally fluxional in solution (NMR spectra) and, in the crystal, it attains a structure similar to 5 owing to weak interactions between mercury and phosphonate‐O1 atoms from adjacent molecules. An isomer to 6, [{HgBr2(1‐κ2O1,P2)}2] (7), was isolated from attempted alkylation of 6 and structurally characterised as a dimer, where ligands 1 bridge two {HgBr2} units. All compounds were studied by spectroscopic methods (IR, NMR, mass) and the solid‐state structures of 1, 2·${1 \over 2}$ H2O, 3·4 CHCl3, 4, 5, 6·5 C6H6, and 7 have been determined by single‐crystal X‐ray diffraction. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)