Solid-state Mo-95 NMR studies of some prototypal molybdenum compounds: Sodium molybdate dihydrate, hexacarbonylmolybdenum, and pentacarbonyl phosphine molybdenum(0) complexes

Molybdenum-95 nuclear quadrupolar coupling constants, chi(Mo-95), and quadrupolar asymmetry parameters, eta, for sodium molybdate dihydrate, hexacarbonylmolybdenum(0), pentacarbonyl-5-methyldibenzophospholemolybdenum(0), and pentacarbonylbis(diphenylphosphino)methanemolybdenum(0) were obtained from solid-state Mo-95 NMR measurements at 26 MHz (9.4 T). The first direct measurements of (1)J(Mo-95, C-13) and (1)J(Mo-95, P-31) from solid-state Mo-95 NMR spectra are reported. Also, the first example of a C-13/C-12 isotope effect on Mo-95 shielding is reported for solid Mo(CO)(6): (1) Delta Mo(C-13/12) = -0.316 ppm. Direct-dipolar spin-spin interactions involving protons and molybdenum (i.e., H-1-Mo-95) are relatively weak and do not appear to make significant contributions to Mo-95 NMR line shapes when spectra are acquired with magic-angle spinning. Hexacarbonylmolybdenum is proposed as a useful setup sample for solid-state Mo-95 NMR studies. Our results for the pentacarbonyl phosphine molybdenum complexes indicate that solid-state Mo-95 NMR studies should be feasible for a range of molybdenum(0) octahedral complexes. These studies will be facilitated by using applied magnetic fields well above 10 T.