MEASUREMENT OF INDIRECT SPIN-SPIN COUPLING-CONSTANTS BETWEEN CRYSTALLOGRAPHICALLY EQUIVALENT NUCLEI - DETERMINATION OF (2)J(P-31, P-31) IN SOLID AG[P(M-TOLYL)(3)]2NO3

Solid-state P-31 magic angle spinning (MAS) NMR spectra of Ag[P(m-toly l)(3)]2NO3 were investigated as a function of the magic angle spinning frequency. Examination of the P-31 MAS NMR spectra obtained at 4.70 a nd 9.40 T indicates that the two phosphorus nuclei have identical isot ropic chemical shirts, that is, they are crystallographically equivale nt, delta = 11.2 ppm. However, since tbe orientation of their respecti ve chemical shift tensors is not coincident, the two phosphorus nuclei are magnetically non-equivalent and exhibit spinning-frequency depend ent P-31 NMR lineshapes. Analysis of the spinning-frequency dependent P-31 MAS NMR spectra at 4.70 and 9.40 T indicates that (2)J(P-31, P-31 )= 140 Hz. This value was confirmed by 2D J-resolved spectroscopy, The determination of an indirect spin-spin coupling constant between two nuclei which constitute an 'isolated' spin pair with identical isotrop ic chemical shifts is not possible in conventional solution-state NMR studies unless a third spin is introduced. The P-31 MAS MMR spectra of Ag[P(m-tolyl)(3)]2NO3 also exhibit resolvable splittings due to Ag-10 9 and Ag-107; (1)J(Ag-109, P-31) = 517 +/- 5 Hz and (1)J(Ag-107, P-31) = 453 +/- 5 Hz. In solution NMR studies these couplings are not alway s observed because of rapid metal-ligand exchange.