Studies on (SCN)2M(NCS)2Hg2(p-tolyl)2 and (SCN)2M(NCS)2Hg2(α-naphthyl)2 and their complexes

p-Tolyl mercury thiocyanate and α-naphthyl mercury thiocyanate react with Co(NCS)₂2py and form a bimetallic pink compound of formula (py)₂(SCN)₂Co(NCS)₂Hg₂R₂ (R = p-tolyl and α-naphthyl group). On heating this compound in vacuum a blue compound (SCN)₂Co(NCS)₂Hg₂R₂ is formed. Nickel analogues (SCN)₂Ni(NCS)₂Hg₂R₂ are formed by direct reaction of p-tolyl or α-naphthyl mercury thiocyanate with nickel thiocyanate. (SCN)₂Co(NCS)₂Hg₂R₂ and (SCN)₂Ni(NCS)₂Hg₂R₂ act as Lewis acids and form complexes with bases. The Lewis acids and their complexes with various bases have been characterized by elemental analyses, molar conductance, molecular weight, magnetic moment, infrared and electronic spectral studies. These studies reveal that both the Lewis acids are monomers. In (SCN)₂Co(NCS)₂Hg₂R₂ the CO(II) has tetrahedral geometry, where as in (SCN)₂Ni(NCS)₂Hg₂R₂ the Ni(II) has octahedral geometry through elongated axial bondings with SCN-groups of other molecules. Thiocyanate bridging of the type R-Hg-SCN-M M = Co(II), Ni(II)] is present in the compounds. Pyridine and dimethylsulphoxide form adducts with these compounds by coordinating at Co(II) or Ni(II). The thiocyanate bridge is retained in these complexes. 2-2′bipyridyl ruptures the thiocyanate bridging in both the Lewis acids and forms cationic-anionic complexes of the type M(L-L)₃]RHg(SCN)₂]₂. In both the type of complexes Co(II) and Ni(II) possess octahedral environment. The “softness” values have been used in a novel manner in proposing the structure of the complexes.