Molar conductance, viscosity and isentropic compressibility of some cobalt (III) complexes in organic solvents

Molar conductance, viscosity and isentropic compressibility of Bu4NBPh4, KX, (CH3)4NX, (C2H5)4NX, (C3H7)4NX, (C4H9)4NX, (C6H5)4PX, C21H38NX and C19H42NX (X = [trans-Co(NH3)2(NO2)4]−) have been measured in acetonitrile (AN), n-butyronitrile (n-BTN), propylene carbonate (PC) and N,N-dimethylacetamide (DMA). The conductance data have been analyzed by the Shedlovsky method to evaluate Λ0 and KA, the viscosity data by Jones-Dole equation to evaluate viscosity B coefficients and the ultrasonic velocity data by suitable equations to get limiting apparent molal isentropic compressibility (Ks,ϕ0) of the electrolytes. Most of these electrolytes show ion association in n-BTN and PC while they are completely dissociated in AN and DMA. The derived limiting parameters have been split into the ionic contributions using which radii (ri) in solution, viscosity B± coefficients and limiting ionic isentropic compressibility (Ks,ϕ0)± of various ions have been evaluated. The results of the present study show that (CH3)4N+, (C2H5)4N+ and K+ are solvated in all these solvents by electrostatic interactions. (C3H7)4N+, (C4H9)4N+, (C6H5)4B−,(C6H5)4P+, C21H38N+, C19H42N+ and [trans-Co(NH3)2(NO2)4]− have large but almost constant respective ionic radii in each solvent except in PC which indicates no solvation of these ions by electrostatic interactions. Isentropic compressibility results on the other hand show that all these ions possess some special type of weak interaction with different solvents involving dispersive interactions. The extent of special interaction is larger in n-BTN and DMA as compared to that in AN and PC. Viscosity B± coefficients also confirm the existence of some special type of interaction of the complex ions with the solvent molecules.