Anisotropy in the 31P, 63/65Cu indirect spin-spin coupling and 31P nuclear shielding tensors of linear copper(I) phosphines.

Phosphorus-31 CP/MAS NMR spectra of two linear bis(tribenzylphosphine)cuprate(I) salts reveal significant anisotropy in the one-bond 31P, 63,65Cu J tensors. The parallel and perpendicular components of 1J(31P, 63Cu), for example, are +2.0 and +1.3 kHz, respectively. The well-characterized space group and point symmetry in one of these compounds greatly simplifies the 31P lineshape analysis, thus dispensing with the need to make assumptions about the interaction tensors involved. This offers an unique opportunity to study DeltaJ by calculating dipolar coupling constants from known internuclear distances, and by using zero-field nuclear quadrupole resonance spectroscopy to obtain the magnitudes of the 63/65Cu nuclear quadrupole coupling constants, CQ. Copper-63 CQ values in these complexes exceed 80 MHz, proving to be the largest reported for copper(I) phosphines. Phosphorus-31 NMR spectra of non-spinning samples at three applied magnetic fields are also presented, along with lineshape calculations based on full-matrix Zeeman-quadrupolar Hamiltonian diagonalization. It is shown that exact 31P lineshape calculations provide the relative signs of CQ, the isotropic J-coupling, and the effective dipolar coupling constant. This appears to be the first unambiguous determination of Delta1J(31P, 63/65Cu).