Structural and spectroscopic studies on mercury(ii) tribenzylphosphine complexes

Abstract

The tribenzylphosphine (PBz3) complexes of mercury(II), [Hg(PBz3)2](BF4)2, [Hg(PBz3)2(NO3)2] and [HgX(NO3)(PBz3)](X = Cl, Br, I and SCN), have been synthesised and their structures determined by single-crystal X-ray crystallography. [Hg(PBz3)2](BF4)2 contains [Hg(PBz3)2]2+ cations with linear P-Hg-P coordination, the first example of a truly two-coordinate [Hg(PR3)2]2+ complex. The mercury coordination in [Hg(PBz3)2(NO3)2] can be described as distorted tetrahedral, with a significant deviation of the P-Hg-P angle from linearity as a result of coordination of the nitrate groups. Nitrate coordination is also observed in [HgX(NO3)(PBz3)](X = Cl, Br, I), resulting in significantly non-linear P-Hg-X coordination. The thiocyanate complex is a centrosymmetric thiocyanate-bridged dimer with distorted trigonal-pyramidal mercury coordination to the P atom of PBz3, to the S and N atoms of two bridging thiocyanate groups, and to the O atom of one nitrate group. For all the nitrato complexes, secondary mercury-nitrate interactions (Hg-O 2.7-3.1 A) effectively raise the coordination number of the Hg(II) centres to six. High-resolution 31P solid-state NMR spectra of the six tribenzylphosphine mercury(II)-complexes, obtained by combining magic-angle spinning, proton dipolar decoupling and proton-phosphorus cross-polarization (CP-MAS), have been recorded. The spectra of [Hg(PBz3)2](BF4)2 and [HgX(NO3)(PBz3)](X = Cl, Br, I and SCN) exhibit a single line, due to species that contain non-magnetic isotopes of mercury, and satellite lines, due to 1J(31P-199Hg) coupling. The asymmetric unit of [Hg(PBz3)2(NO3)2] contains two molecules with four phosphorus environments, resulting in two AB spectra with 2J(31P-31P) coupling, due to species that contain non-magnetic isotopes of mercury, and satellite lines consisting of two ABX spectra, due to 1J(31P-199Hg) coupling. These spectra have been analysed to yield all of the chemical shifts and coupling constants involved. A remarkable increase in 1J(31P-199Hg) is observed from [Hg(PBz3)2](BF4)2 to [Hg(PBz3)2(NO3)2] as a consequence of the incorporation of the nitrate group into the Hg coordination sphere in the latter case. Several of the spectra also exhibit broader satellites due to the presence of scalar spin-spin coupling between 31P and the quadrupolar 201Hg nucleus. Slow-spinning methods have been used to analyze the spinning-sideband intensities of the NMR spectra, in order to obtain the 31P shielding anisotropy and asymmetry parameters Deltasigma and eta. The 199Hg and 31P NMR shielding tensors of PMe3 models of the above six compounds have been calculated using relativistic density functional theory. The 31P results are in good agreement with experiment and assist in the assignment of some of the signals.

Quantifying the Orbital Contribution in the “Spodium Bond” via Natural Orbital for Chemical Valence-Charge Displacement Analysis

“…An interesting case is that of BEJGOM, where an oxygen atom of the NO3anion undergoes both HB with a C-H of the ligand and charge transfer to the cationic Hg center. As the Hg-O distance is 5.0 Å, this is compatible with SpB (a coordinated nitrate would be expected at a distance of about 2.6-3.0 Å 19 ).…”

Hybrid structures formed by homo- and heteroleptic aliphatic dicarboxylates of lead with 2-D inorganic connectivity

“…Unlike the nitrate anion, oxy-anions such as phosphate, sulfate, sulfite and selenate are known to form organically templated inorganic framework compounds [42,43]. There are, however few organic inorganic hybrid compounds, wherein the nitrate anion is involved in the network formation [44][45][46][47][48][49][50][51][52][53][54]. Most of these compounds are with low-dimensional inorganic connectivity, I m (mo2).…”

Structural and Spectroscopic Characterisation of Linearly Coordinated Gold(I) Tribenzylphosphane Complexes

“…[4] Similarly, with mercury(II) 2+ cations with linear P-Hg-P coordination, the first example of a truly two-coordinate [Hg(PR 3 ) 2 ] 2+ complex. [5] The driving force for the formation of ionic adducts with PBn 3 has been ascribed to interligand "embraces" within the linear two-coordinate cation, [2,3] such an embrace presumably preventing secondary coordination of the mercury to the BF 4 -counterions. Recently, the structure of the complex [Au(PAd 2 Bn) 2 ][AuCl 2 ] (Ad = 1-adamantyl) has been reported as the first example of an ionic form of a 1:1 chlorophosphanegold(I) complex.…”