Relationship between Softness Parameters and Physicochemical Studies of Bimetallic Compounds

Chemistry Department, M. L. K. College, Balrampur-271 201
Manuscript received 12 April 1985, revised 21 March 1986, accepted 25 June 1986

Pyridine, nicotinamide and bipyridyl have been reacted with (SCN)₂M(NCSHgR)₂, where M=Mn^II, Co^II, Ni^II, Cu^II and Zn^II ; and R=m-CH₂C₅H₄ and NO₂C₆H₄. Pyridine and nicotinamide form bridged complexes of general formula L₂(SCN)₂- M(SCNHgR)₂, whereas bipyridyl forms cationic-anionic complexes [M(L—L)₃] [RHg(SCN)₂]₂. The structure of the complexes and their stability constant (log K) have been established by various physicochemical methods. Quantitative softness parameters, such as effective softness values $E_{n_{(}eff)}^{‡}$of M, $E_{m_{(}eff)}^{‡}$ of nitrogen-end of RHgSCN, coordinating sites of the ligands, matching $\Delta E_{nm}^{‡}$ and matching constant values have been calculated by the recently developed techniques. The stability cons­tant (log K) and matching constant data are consistent with each other. The coordi­nating sites in the ligand have been determined by infrared measurements. The sites of linkage are in conformity with the results obtained from matching values. The stabi­lity of the thiocyanate and selenocyanate bridge between M and Hg, the formation of cationic-anionic complexes by bipyridyl and formation of bridged complexes by other ligands have been explained with the help of softness parameters.