A definitive example of aluminum-27 chemical shielding anisotropy

Solid-state 27Al NMR spectra have been obtained for a crystalline 1:1 complex of AlCl3 and OPCl3. Aluminum chloride phosphoryl chloride, AlCl3 . OPCl3 (1), is unusual in that the Al-O-P bond angle is close to 180 degrees. From analysis of the 27Al MAS NMR spectra, it was determined that the 27Al nuclear quadrupole coupling constant is 6.0(1) MHz, the asymmetry in the electric field gradient (efg) tensor is 0.15(2), and the isotropic chemical shift, deltaiso(27Al), is 88(1) ppm. Solid-state 27Al NMR of a stationary sample reveals a line shape affected by a combination of anisotropic chemical shielding and second-order quadrupolar interactions. Analysis of this spectrum yields a chemical shift anisotropy of 60(1) ppm and orientations of the chemical shift and electric field gradient tensors in the molecular frame. Experimental results are compared with those calculated using ab initio Hartree-Fock and density functional theory. Copyright 1998 Academic Press.