P. Manikandan et al., LIGAND DYNAMICS IN TETRACOORDINATE COPPER(I) COMPLEXES OF BIS(PYRAZOLYL)PYRIDINE LIGANDS, Journal of the Chemical Society. Dalton transactions (Print), (19), 1998, pp. 3219-3225
Several mononuclear and a binuclear copper(I)-phosphine complex with a
tridentate ligand, L [2,6-bis(3,5-dimethylpyrazol-1-ylmethyl)pyridine
] or L' [2,6-bis(pyrazol-1-ylmethyl)pyridine], have been prepared and
characterized. The crystal structure of [LCu(PPh2CH2CH2PPh2)CuL][ClO4]
(2) has been solved. All complexes exhibit interesting molecular dynam
ics which could be monitored by H-1 NMR spectral characteristics arisi
ng from the methylene group of the ligand and also from the protons of
the pyrazole part of the ligand in some cases. The complexes with uns
ymmetric phosphine ligands such as PPhnBu3-n with n = 1 or 2 revealed
the presence of two conformations with differing populations as eviden
ced by temperature dependent H-1 NMR spectral data. The thermodynamics
of these transformations due to the fluxional character of the ligand
, L, has been studied by computer simulations of the experimental spec
tra. The NMR spectral characteristics revealed that the methylene prot
ons are diastereotropic.