Theoretical Evidence of Persistent Chirality in D3 Homoleptic Hexacoordinate Complexes with Monodentate Ligands

Abstract
A theoretical study of the enantiomer interconversion pathway relevant to racemization reactions of hexacoordinate transition‐metal complexes is presented based on density functional calculations. The potential‐energy surface for the trigonal twist pathway of the [Zr(SH)6]2− model compound has been explored. The optimum structure reproduces, to a very good approximation, the experimental geometry of the analogous compound in which the thiolato groups have C6H4‐4‐OMe substituents instead of H atoms. A barrier of about 19 kcal mol−1 is estimated for the racemization of [Zr(SH)6]2− and exploratory calculations for [Zr(SC6H4‐4‐OMe)6]2− indicate that a larger barrier should be expected. For the chiral homoleptic organometallic complexes [ZrMe6]2− and [RhMe6]3− no significant racemization barrier is expected.