Synthesis, characterisation and study of mercury(II) bromide complexes with triphenylphosphine and heterocyclic thiones. The crystal structures of [bis(triphenylphosphine) dibromo mercury(II)] and [dibromo (pyrimidine-2-thionato) (triphenylphosphine) mercury(II)]. Extended intra-molecular linkages via NH⋯Br and CH⋯Br interactions

Abstract

Fractional crystallisation of the mixture, resulting from the direct reaction of mercury(II) bromide with triphenylphosphine (PPh3) and pyrimidine-2-thione (pmtH), gives crystals of [HgBr2(PPh3)2] (1) and [HgBr2(PPh3)(pmtH)] (2). The complexes have been characterised by their elemental analyses, melting points and their FT-IR, far-IR, and UV–Vis spectroscopic data. The crystal structures of both [bis(triphenylphosphine) dibromo mercury(II)] (1) and [dibromo (pyrimidine-2-thionato)(triphenylphosphine) mercury(II)] (2) complexes have been established by single crystal X-ray crystallography at room temperature. Molecule 1 is monomeric with tetrahedral geometry around the metal ion. Two bromide atoms are co-ordinated to the mercury(II) ion [Hg(1)Br(1)=2.627(2) and Hg(1)Br(2)=2.6368(14) Å] while two triphenylphosphine molecules are also co-ordinated to the metal ion via their phosphorus atoms with Hg(1)P(1) and Hg(1)P(2) bond distances of 2.550(4) and 2.491(5) Å, respectively. The complex is covalent in the solid state. The unit cell of 2 consists of a molecule with tetrahedral geometry around the mercury(II) ion. A triphenylphosphine ligand and a pyrimidine-2-thione molecule are co-ordinated to the metal ion through their phosphorus and sulfur atoms with Hg(1)P(1) and Hg(1)S(2) bond lengths of 2.450(2) and 2.4795(19) Å, respectively. Two bromide atoms are also co-ordinated to the mercury ion [Hg(1)Br(1)=2.7065(10) and Hg(1)Br(2)=2.6997(11) Å]. The entire complex is covalent in the solid state. Extended intra-molecular linkages via NH⋯Br interactions lead to a polymeric structure. Extended CH⋯Br contacts link the alternate parallel chains forming a supramolecular assembly.