A tunable coordination response of the phosphorus-based hexadentate ligand (S)P[N(Me)N=CHC₆H₄-o-OH]₃ (LH₃): synthesis and structure of LM (M = Sc, Cr, Mn, Fe, Co, Ga)

Abstract

The multidentate ligand (S)P[N(Me)N=CHC₆H₄-o-OH]₃ (LH₃) reacts with a number of M^III salts to afford the neutral mononuclear complexes LM (M = Sc, Cr, Mn, Fe, Co and Ga). The coordination behaviour of the ligand is hexadentate in all of these complexes, where it encapsulates the metal ion in a facial 3N,3O coordination mode. All the metal complexes have been characterised by spectroscopic and X-ray crystallographic methods. The metal atoms in the complexes LSc, LMn, LFe and LGa adopt a distorted octahedral geometry, whereas the geometries of LCr and LCo are more ideal. The electrochemical behaviour of LMn shows that it can be reversibly reduced (E_½ = -0.13 V) in a single electron process. The achiral ligand LH₃ induces chirality in the metal complexes LM upon coordination with the metal ion. All the complexes crystallise as racemic compounds where both the clockwise (Δ) and anticlockwise (Λ) enantiomorphs are present in the crystal structure in an ordered arrangement. Furthermore, all complexes show supramolecular chiral recognition in their crystal structures; the Δ form recognizes the Λ form by means of intermolecular C-H···O and C-H···S interactions.