CRYSTALLOGRAPHIC AND COPPER-63,65 NUCLEAR-QUADRUPOLE RESONANCE STUDY OF 2-CO-ORDINATED COPPER(I) CATIONS WITH HINDERED SUBSTITUTED PYRIDINE LIGANDS

The crystal structures and Cu-63, Cu-65 NQR spectra are reported of the two-co-ordinated complex cations formed between Cu1 and hindered pyridine homologues, [CuL2]X [L = 2,6-dimethylpyridine, X = BF4- 1, PF6- 2 or ClO4- (alpha-phase) 3, (beta-phase) 4, (gamma-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-degrees respectively, 3, 5 and 7 have essentially planar structures with dihedral angles of 0, 3.0 and 0-degrees 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 Cu-63, Cu-65 NQR resonance frequencies are less.