P-31 DIFFERENTIAL LINE BROADENING IN THE PRESENCE OF THE CO-59 QUADRUPOLAU-CSA INTERFERENCE IN TETRAHEDRAL CLUSTERS

The first investigation and analysis of the effects, theoretically pre dicted by Werbelow et al. [J, Chem, Soc. Faraday Trans. 83, 871 (1987) ], of interference terms on the lineshape of a spin coupled to a high- spin nucleus undergoing quadrupolar and chemical-shift anisotropy (CSA ) relaxations are reported for three tetrahedral clusters HFeCo3(CO)(1 1)L with L = PPh(2)H (1), L = PCy(2)H (2), and L = PPh(3) (3) (Cy = cy clohexyl), For these clusters in solution, an unusual asymmetric broad NMR multiplet of the SIP nucleus scalar-coupled to a Co-59 nucleus is observed, It is shown that the Co-59 CSA-quadrupolar interference ter m is the origin of the asymmetry of the P-31 spectra, The analysis of the lineshape of the H-1-decoupled spectra gives the spin-coupling con stants (1)J(P-31-(CO)-C-59) and the CSA contribution to the Co-59 rela xation. Experimental measurements of T-1 and of the linewidths for cob alt-59 are reported and support these findings. (C) 1995 Academic Pres s, Inc.