Nuclear spin coupling effects in phosphorus-31 MAS NMR spectra of solid bis(triphenylphosphine)(phenylcyanamido)copper(I) complexes

Abstract

Solid-state 31P cross polarization (CP) magic angle spinning (MAS) NMR data have been obtained on three solid bis-(triphenylphosphine)(phenylcyanamido)copper(I) complexes, [(Cu(PPh3),(4-RC6H4NCN)},]( R = H, Me, Cl), at magnetic fields of 2.1 1, 7.05,9 .40, and 11.74 T. The highly structured, complex spectra exhibit both heteronuclear 1J(31P,63Cuan) d1J(31P,65Cuan) d homonuclear 2J(31P,31Pis)o tropic spin-spin coupling, in addition to some residual coupling d(31P,63C~) and d(31P,65Ce~m) emanating from second rank interactions. The spectral analyses and subsequent structural implications are aided by studying the magnetic field variation of both 1D 31P CP-MAS and 2D IIP CP-MAS COSY NMR experiments and by simulation of 1D spectra through diagonalizing the nuclear spin Hamiltonian which includes a quadrupolar perturbation from the copper spin states. The asymmetry induced in the J-split multiplets from quadrupole effects in this P2CuN2 system is much smaller than is usually encountered in P2CuX2 (X = halogen) and PzCu02 systems. This may be attributable to an unusually small electric field gradient at the copper site despite marked deviation of the copper coordination sphere from tetrahedral point symmetry.