Quantitative values of softness and structure of dimetallic tetrathiocyanate complexes

Abstract

Bimetallic tetrathiocyanate complexes of the type MM′ (SCN) 4·xL [M = Ni(II), Co(II), Zn(II); M′ = Cd(II), Hg(II) and L = thiazolidinethione (tzt), thiohydantoin (thn), ethylenethiourea (etu); x = 2, 4, 6] have been prepared and their structures have been proposed by elemental analysis molar conductance, magnetic moment, infrared spectral, electronic spectral studies quantitative values of softness. These studies indicate that the complexes are of two types: cationic-anionic, viz. [ML x] ++[Cd(SCN) 4] − −[M = Co(II), Ni(II); L = tzt, thn, etu; x = 4, 6] and monomeric thiocyanate bridged viz.L 2M(NCS) 2Hg(SCN) 2 [M = Zn, Co, Ni; L = tzt, etu, thn] and L 4′Ni(NCS) 2Hg(SCN) 2 (L′ = etu, thn). Thiocarbonyl sulphur is the donor site in cationic-anionic complexes and imino nitrogen in bridged thiocyanate complexes in all three ligands. The relative strength of thiocyanate bridges have been correlated with the total softness difference ΔTE n‡ (MM′) which was calculated using Klopman's equation. Symmetry and group theoretical calculations have also been made to support the proposed structures.