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

Reaction of mercury(II) halides with 1'-(diphenylphosphino)ferrocenecarboxy lic acid (Hdpf) affords [HgX2(Hdpf-P)(2)] or [HgX(mu-X)(Hdpf-P)](2) complex es (X = Cl, Br, I) depending on the stoichiometry of the educts. The comple xes have been studied by IR, Mossbauer and solution NMR spectroscopy. In di methyl sulfoxide-d(6) solution, H-1- and P-31{H-1}-NMR spectra indicate sol volytic cleavage of the mercury(II)-phosphine bond resulting in a partial d ecomplexation of the phosphine ligand. Electrochemical measurements in dono r solvents also confirm the presence of the non-coordinated ligand since th e electrochemical behavior is the superposition of that of the product of s olvolysis and of the ligand. X-ray structural analysis, of the representati ves 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 ) Angstrom; beta = 114.953(7)degrees; Z = 4) and [HgBr(mu-Br)(Hdpf-P)](2). 2CH(3)CO(2)H ([C54H54Br4Fe2Hg2O12P2], triclinic; space group P (1) over bar , a = 9.442(1), b = 11.7101(9), c = 14.806(1) Angstrom; alpha = 109.692(7), beta = 92.494(9), gamma = 101.883(7)degrees; Z = 1). The P-monodentate coo rdination of the phosphinocarboxylic ligand was confirmed in both cases, th e carboxyl group being involved in hydrogen bonding to carboxyl groups of e ither neighboring ligand or solvating acetic acid. The expected Br2P2 and B r3P tetrahedral donor sets around Hg(II) are the subject of different degre es of deformation due to steric effects. Fe-57 Mossbauer spectra of the com plexes also point to the simple P-coordination of the ferrocenylphosphino l igand, as follows from the decrease of the quadrupole splitting and only a slight variation of the isomer shift on going from ligand to complex. (C) 1 999 Elsevier Science S.A. All rights reserved.