Study of comparative Lewis -base behaviour of p -tolyl mercury selenocyanate and α-naphthylmercury selenocyanate

p-Tolylmercury selenocyanate and α-naphthylmercury selenocyanate act asLewis-bases towards Co(NCS)2·2C2H5N and form a pink compound of the formula (CH5N)2(SCN)2Co(NCSeHgR)2 (R=p-tolyl or α-naphthyl). On heating this compounds in vacuum, a blue compound (SCN)2Co(NCSeHgR)2 was formed,RHgSeCN gives a similar compound on reaction with Ni(NCS)2. The compounds (SCN)2 M(NCSeHgR)2;M=Co(II), Ni(II) again act asLewis-acids. In theseLewis-acids Co(II) has a tetrahedral geometry whereas nickel(II) has an octahedral environment through elongated axial bondings ofXCN-groups (X=S or Se). The selenocyanate bridging of the typeR-Hg-SeCN-M is present in these monomer compounds which were characterized by elemental analyses, molar conductance, molecular weight, magnetic moment, stability constant (logK) infrared and electronic spectral studies. These physico-chemical studies indicate that thep-tolylmercury selenocyanate is a better donor than the α-naphthylmercury selenocyanate and Ni(NCX)2 is a better acceptor than Co(NCX)2. It has also been observed thatRHgSCN is a better donor thanRHgSeCN. These results are supported by the derivations made from softness parameters.