NUCLEAR-QUADRUPOLE RESONANCE AND CRYSTALLOGRAPHIC STUDIES OF 3-CO-ORDINATED COPPER(I) CATIONS WITH ALKYLPYRIDINE LIGANDS

The preparation and Cu-63, Cu-65 NQR resonance frequencies of fourteen three-co-ordinated complex cations of copper(I) with alkylpyridine ligands are reported. Crystal structures of seven of these have also been determined. The complexes show a wide variety of symmetries but in none does the copper atom lie on an ideal three-fold axis. In most the copper lies in an essentially trigonal-planar environment but with at least two of the pyridine ligands twisted well out of the plane containing the copper and the three nitrogen atoms. In most cases one of the N-Cu-N bond angles is significantly greater than 120-degrees while the length of the opposing bond is significantly greater than that of the two bonds that form this angle. All the NQR frequencies at 77 K are in the neighbourhood of 45 MHz, with the exception of that of the complex with 3,5-dimethylpyridine, the only ligand without at least one alkyl substituent ortho to the nitrogen atom, where the frequency at 77 K is 40.471 MHz. This difference results from the axial co-ordination of both the PF6 anions to the copper cation.