Metal complexes of hybrid oxygen-arsenic ligands—III : Complexes of 2-tertiary arsinobenzoic acids with zinc(II), cadmium(II) and mercury(II). Discovery of a novel chelating system

This paper describes the preparation of the halogeno complexes, HgX₂(o-R₂AsC₆H₄CO₂H) (X = Cl, Br, I, and R = Et; X = Br, I, and R-C₆H₁₁) and the carboxylate complexes, M(o-R₂-AsC₆H₄CO₂)₂nL(M = Cd, R = Et, C₆H₁₁ and n = O; M = Zn; R = Et; nL = H₂O; M = Zn, R = C₆H₁₁, nL = 3H₂O; M = Hg, R = p-tolyl, nL = 2H₂O; M = Hg, R = Me, Ph; C₆H₁₁ and nL = EtOH). The structures already reported for the halogeno complexes with R = Ph, Me, p-tolyl and X = Cl, Br, I, have been revised on the basis of detailed scrutiny of the IR spectral data and all these complexes have been divided into four structural types out of which three retain the acid dimer unit of the free ligand. In the carboxylate complexes the lowering of ν_s, CO₂ band and the marginal change in the ν_as CO₂ band with respect to those of the corresponding ligand sodium salts have been attributed to the existence of a novel resonating chelating system with the possibility of having a ring current.