Cobalt(II) Mercury Tetrathiocyanate Complexes with Lewis Bases

Abstract

A new series of octahedral cobalt(II) complexes are formed when CoX2(X = Cl, Br, I, SCN) reacts with Hg(SCN)2 in the presence of Lewis bases. These complexes of stoichiometry CoHg(SCN)4•2L (L = THF, dioxane, pyridine, aniline) are pink to violet solids which slowly decompose to the blue crystalline solid, CoHg(SCN)4, the stable magnetic susceptibility standard. On further reaction of CoHg(SCN)4•2THF with mono-, bi-, and polydentate ligands in dry ethanol, complexes of the following types are obtained: CoHg(SCN)4•2L (L = PΦ3), CoHg(SCN)4•2LL (LL = trien), CoHg(SCN)4•3LL (LL = en, bipy), and CoHg(SCN)4•4LL (LL = phen). The stoichiometry of these were determined by elemental analysis. Possible structures of these are discussed with the help of mid and far infrared, visible, and ultraviolet spectroscopy, magnetic susceptibility, and X-ray powder diffraction. Some new i.r. bands like Co—P, Co—N, and Hg—S are assigned in the low region.

Structure of Ni[Ag(SCN)2]2•2diox and its derivatives

“…This difference supports linkage through S in thiourea and through N in ethylene thiourea. The X-sensitive absorption bands at 1092, 705, and 437 cm-I are typical of coordinated triphenylphosphine (1).…”

“…Both bipyridine and phenanthroline act as bidentate donors. The nitrogen of NH is the donor site in aniline, p-toludine, and ethylene thiourea, and sulphur in thiourea as indicated by the negative shifts in v,, and v,, modes respectively (1,16,17). The 10 Dq of the S-bonded thiourea complex is greater by 1900 cm-I than the N-bonded ethylene thiourea (Table 2).…”

“…The positions of the bands in these diagnostic regions are indicative of S-bonded thiocyanates (1)(2)(3)6). …”

“…On the basis of its similarity in other data with this class of compounds, it is thought that all the complexes are 1 : 1 electrolytes. (v) The pyridine derivative ligands show features of coordination through their ring nitrogen as evidenced by the positive shift in the bands due to ring vibrations (1,5). Both bipyridine and phenanthroline act as bidentate donors.…”

“…In MMf(NCS),, both M[Co(II), Ni(II), Cu(II)] and Mf[Zn(I1), Cd(II), Hg(I1)I are in their preferred coordination geometry, and the compounds are energetically quite stable (1)(2)(3)(4)(5)(6)(7). Bimetallic tetrathiocyanate, in which one metal prefers octahedral coordination geometry and the other a linear, viz., Ag(I), Cu(I), Au(I), has not been reported previously.…”