Monomeric pyridyl-2-selenolate complexes of cadmium and mercury: Synthesis, characterization and their conversion to metal selenide nanoparticles

Reactions of [MCl2(tmeda)] (M = Cd or Hg; tmeda = N,N,N′,N′-tetramethylethylenediamine) with M′SeC5H3(R-3)N (R = H or Me) gave selenolate complexes of the general formula [M{SeC5H3(R-3)N}2(tmeda)n] (M/R/n = Cd/H/1 (1); Cd/Me/1 (2); Hg/H/1 (3) and Hg/Me/0 (4)). The complexes were characterized by elemental analysis, UV–Vis and NMR (1H, 13C, 77Se, 113Cd and 199Hg) spectroscopy. The crystal structures of {SeC5H3(Me-3)N}2, [M(SeC5H4N)2(tmeda)] (M = Cd or Hg) and [Hg{SeC5H3(Me-3)N}2] were established by single crystal X-ray diffraction. The complex, [Cd(SeC5H4N)2(tmeda)] comprises of an octahedral cadmium atom containing three chelating, two SeC5H4N and one tmeda, ligands. The corresponding mercury complex adopts a severely distorted tetrahedral configuration defined by the two-monodentate selenolate and chelating tmeda. The complex, [Hg{SeC5H3(Me-3)N}2] has a linear structure with monodentate selenolate ligand. The cadmium complexes undergo a two-step decomposition (TGA) leading to the formation of CdSe. Thermolysis of [Cd{SeC5H3(R-3)N}2(tmeda)n] in hexadecylamine (HDA)/tri-n-octylphosphineoxide (TOPO) yields CdSe nanoparticles, which were characterized by UV–Vis, XRD, SEM and TEM (in part).