NUCLEAR-SPIN COUPLING EFFECTS IN P-31 MAS NMR-SPECTRA OF SOLID BIS(TRIPHENYLPHOSPHINE)(PHENYLCYANAMIDO)COPPER(I) COMPLEXES

Solid-state P-31 cross polarization (CP) magic angle spinning (MAS) NMR data have been obtained on three solid bis(triphenylphosphine)(phenylcyanamido)copper(I) complexes, [{Cu(PPh3)2(4-RC6H4NCN)}2] (R = H, Me, Cl), at magnetic fields of 2.11, 7.05, 9.40, and 11.74 T. The highly structured, complex spectra exhibit both heteronuclear 1J(P-31,Cu-62) and 1J(P-31,Cu-65) and homonuclear 2J(P-31,P-31) isotropic spin-spin coupling, in addition to some residual coupling d(P-31,Cu-63) and d(P-31,Cu-65) emanating from second rank interactions. The spectral analyses and subsequent structural implications are aided by studying the magnetic field variation of both ID P-31 CP-MAS and 2D P-31 CP-MAS COSY NMR experiments and by simulation of ID spectra through diagonalizing the P-31 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 P2CuO2 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.