Synthesis, characterization and X-ray structural, electrochemical and Mössbauer study of mercury(II) complexes with 1′-(diphenylphosphino)ferrocenecarboxylic acid

Abstract

Abstract Reaction of mercury(II) halides with 1′-(diphenylphosphino)ferrocenecarboxylic acid (Hdpf) affords [HgX2(Hdpf-P)2] or [HgX(μ-X)(Hdpf-P)]2 complexes (X=Cl, Br, I) depending on the stoichiometry of the educts. The complexes have been studied by IR, Mossbauer and solution NMR spectroscopy. In dimethyl sulfoxide-d6 solution, 1H- and 31P{1H}-NMR spectra indicate solvolytic cleavage of the mercury(II)–phosphine bond resulting in partial decomplexation of the phosphine ligand. Electrochemical measurements in donor solvents also confirm the presence of a non-coordinated ligand since the electrochemical behavior is the superposition of that of the product of solvolysis and of the ligand. X-ray structural analysis, of the representatives of both types, was carried out: [HgBr2(Hdpf-P)2] ([C46H38Br2Fe2HgO4P2], monoclinic; space group C2/c, a=19.453(1), b=13.704(1), c=17.929(2) A; β=114.953(7)°; Z=4) and [HgBr(μ-Br)(Hdpf-P)]2·2CH3CO2H ([C54H54Br4Fe2Hg2O12P2], triclinic; space group P, a=9.442(1), b=11.7101(9), c=14.806(1) A; α=109.692(7), β=92.494(9), γ=101.883(7)°; Z=1). The P-monodentate coordination of the phosphinocarboxylic ligand was confirmed in both cases, the carboxyl group being involved in hydrogen bonding to carboxyl groups of either neighboring ligand or solvating acetic acid. The expected Br2P2 and Br3P tetrahedral donor sets around Hg(II) are the subject of different degrees of deformation due to steric effects. 57Fe Mossbauer spectra of the complexes also point to the P-coordination of the ferrocenylphosphino ligand, as follows from the decrease of the quadrupole splitting and only a slight variation of the isomer shift on going from ligand to complex.