New dithiophosphonate complexes of nickel, cadmium, mercury and lead.
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This study was primarily focused on the synthesis and structural X-ray crystallographic analyses of new complexes. The work undertaken investigated the reactivity of the diphosphetane disulfide dimer, [P(4-C6H4OEt)S(S)]2, which is the phenetole analogue of the popular Lawesson's Reagent (LR), towards the primary and secondary alcohols methanol, 2- propanol, 1-propanol and 2-butanol. The phenetole LR dimer undergoes nucleophilic attack when reacted with primary or secondary alcohol species, cleaving it symmetrically and forming the respective dithiophosphonic acid, which is then readily deprotonated by ammonia, yielding ammonium dithiophosphonato ligand salts of the type NH4[S2PR(OR’)] (R=4-C6H4OEt) used directly in complexing metals centres. The dithiophosphonato ligands are all bidentate and mono-anionic. New late transition-metal complexes were formed from the reaction between [S2PR(OR’)]- with the halide or nitrate salts of Cadmium(II), Nickel(II), Lead(II) and Mercury(II), affording both mononuclear and dinuclear complexes. Suitable crystals of nine complexes were eventually found and subjected to X-ray crystallographic analyses: four distorted square planar Ni(II) complexes (1A, 2A, 3A, 4A), two dinuclear Hg(II) complexes (1B, 2B), one dinuclear Cd(II) complex (1C) and one distorted pyramidal dimeric Pb(II) complex (2D) and an octahedral Ni(II) complex (4Ai). Additionally, all new complexes were fully characterized by means of 31P and 1H and 13C NMR, FTIR, elemental analysis and, as stated, single crystal X-Ray diffraction. This study initially set out to determine if small changes in starting materials could lead to significant changes in structure (as it often does, through unexpected hydrogen bonding, for example), but it turned out in this study that most of the complexes prepared, although new, did not deviate significantly from the structural details of related complexes previously prepared, which is a result in itself.