Interplay of ligand chirality and metal configuration in mononuclear complexes and in a coordination polymer of Cr(iii)

Abstract

In order to investigate the influence of ligand chirality on the configuration of the coordinated metal, five pseudooctahedral Cr(III) complexes with one or two chelating R,R-1,2-diaminocyclohexane ligands have been synthesized. The mononuclear complexes [Cr(R,R-chxn)₂Cl(DMSO)]Cl₂, [Cr(R,R-chxn)₂Cl₂]Cl, [Cr(acacCN)(R,R-chxn)₂](NO₃)₂, [Cr(acacCN)₂(R,R-chxn)]NO₃, [Cr(acacCN)₂(R,R-chxn)]PF₆. (R,R-chxn = R,R-1,2-diaminocyclohexane; acacCN = deprotonated 3-cyanoacetylacetone and DMSO = dimethyl sulfoxide) have been obtained as crystalline solids, mostly solvates, and the potential chirality transfer from the enantiopure ligand to the configuration at the Cr(III) center has been investigated. The cationic complex [Cr(acacCN)₂(R,R-chxn)]⁺ has been synthesized as exclusively Λ configured at the metal. In this complex, the dangling nitrile groups of the ditopic acacCN ligands may coordinate to Ag(I): the chiral-at-metal building block has thus been converted to the 2D network Ag[Cr(acacCN)₂(R,R-chxn)]₂(PF₆)₃ under retention of the stereochemistry at Cr(III). With respect to topology, the polycations in this mixed-metal coordination polymer correspond to two interpenetrated {4,4} nets.