Crystallographic and copper-63,65 nuclear quadrupole resonance study of two-co-ordinated copper(I) cations with hindered substituted pyridine ligands

Abstract

The crystal structures and ^63,65Cu NQR spectra are reported of the two-co-ordinated complex cations formed between Cu^I and hindered pyridine homologues, [CuL₂]X [L = 2,6-dimethylpyridine, X = BF₄^–1, PF₆^–2 or ClO₄^–(α phase)3, (β phase)4(γ phase)5; L = 2,4,6-trimethylpyridine, X = BF₄^–6 or CuCl₂^–7]. All complexes have essentially linear N–Cu–N fragments, but whereas for 1, 2, 4 and 6 the copper atom is located on a two-fold axis and the two pyridine rings have dihedral angles of 60.4, 56.0, 58.1 and 51.3° respectively, 3, 5 and 7 have essentially planar structures with dihedral angles of 0, 3.0 and 0° respectively. In agreement with a previous study of the planar complex 3, the Cu–N bond is significantly longer than in the non-planar conformation, and the corresponding ^63,65Cu NQR resonance frequencies are less.