Complexation of tris(2-pyridyl)phosphine chalcogenides with copper(I) halides: The selective formation of scorpionate complexes, [Cu(N,N′,N″-2-Py3PX)Hal] (X=O, S and Se)

A series of copper(I) scorpionates, [Cu(N,N′,N″-2-Py3PX)Hal] (X = O, S and Se; Hal = Cl, I), has been synthesized in 67–88% yields by the reaction of tris(2-pyridyl)phosphine chalcogenides with Cu(I) halides (CH2Cl2, r.t., 10 min). These complexes were characterized by X-ray crystallography, NMR and UV–Vis techniques to reveal that the ligand coordinates with Cu(I) ion via three pyridine nitrogen atoms to form near-C3-symmetrical [Cu(N–C)3PX] cage. The halogen atoms are bonded with metal so that the latter adopts a distorted trigonal pyramidal geometry. The DFT computations confirm that the observable κ3-N,N′,N″-binding of the ligands is energetically more favorable than the alternative coordination modes, i.e. κ1-X-monodentate, κ2-N,N′- or κ2-N,X-bidentate and κ3-N,N′,X-tridentate.