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

Abstract

Trans and cis influences of various X ligands in two isomeric structures of acyclic hypervalent compound Ph[XI(OH)] and heterocyclic λ3-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 (ρ), I–OH stretching frequency (ν), and molecular electrostatic potential minimum (Vmin) at the OH lone pair. d, ρ, ν, and Vmin are found to be good parameters for quantifying trans and cis influences, and among them, Vmin is the most sensitive parameter. Heterocyclic λ3-iodanes showed a smaller trans influence than acyclic λ3-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 λ3-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 λ3-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 λ3-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 heterocyclic hypervalent complexes.