Trans and Cis Influences in Hypervalent lodine(III) Complexes: A DFT Study

Trans and cis influences of various X ligands in two isomeric structures of acyclic hypervalent compound Ph[XI(OH)] and heterocyclic lambda(3)-iodane Ph[(heterocycle)I(OH)] have been investigated on the basis of I OH bond distance (d), electron density at I OH bond critical point (rho), I-OH stretching frequency (upsilon), and molecular electrostatic potential minimum (V-min) at the OH lone pair. d, rho, upsilon, and V-min are found to be good parameters for quantifying trans and cis influences, and among them, V, is the most sensitive parameter. Heterocyclic A3-iodanes showed a smaller trans influence than acyclic lambda(3)-iodanes. All systems showed higher trans influence than cis influence while relative order of both is in accordance with the inductive nature of the ligands. Among the heterocyclic A3-iodanes, strong trans/cis influence is observed with N or B in the ring while P gave moderate and S gave weak trans/cis influence. Among the substituents on the cis-positioned phenyl ring in heterocyclic lambda(3)-iodanes, electron withdrawing ortho substitution significantly strengthened the hypervalent I OH bond. The stability of a product resulting from the nucleophilic attack of Cl- on a lambda(3)-iodane is directly correlated with the trans/cis influence of the ligands. This relationship is helpful to make good prediction on the interaction energy of a nucleophile in trivalent hypervalent iodine complex and hence useful in designing stable acyclic and heterocydic hypervalent complexes..