SINGLE-CRYSTAL P-31 NMR AND X-RAY-DIFFRACTION STUDY OF A MOLYBDENUM PHOSPHINE COMPLEX - -METHYLDIBENZOPHOSPHOLE)PENTACARBONYLMOLYBDENUM(0)

The molecular structure of methyldibenzophosphole)pentacarbonylmolybde num(0), 1, has been determined by X-ray crystallography. The crystal i s monoclinic C2/c, Z = 8, with unit dimensions of: a = 31.113(2) Angst rom, b = 7.7917(5) Angstrom, c = 17.9522(12) Angstrom, and beta = 122. 135(4)degrees. Least-squares refinement coverged to R(F) = 0.0245 for 2407 independent reflections. The molecular structure is typical of ph osphine-substituted metal carbonyls. It contains an approximate mirror plane which bisects the dibenzophosphole framework. Phosphorus-31 NMR spectra of powder and single-crystal samples of 1 have been obtained with cross-polarization and H-1 high-power decoupling. The P-31 CP/MAS NMR spectra exhibit exceptionally well-resolved satellites due to spi n-spin coupling interactions with Mo-95,Mo-97 (I = 5/2). Using first-o rder perturbation theory, the multiplets have been analyzed to yield ( 1)J(Mo-95,Mo-97, (31)p) = 123(2) Hz and estimates of the molybdenum nu clear quadrupolar coupling constants, chi(Mo-95) = -0.87 MHz and chi(M o-97) = 10.1 MHz. Phosphorus-31 NMR spectra of a large single crystal of 1 have been investigated as a function of orientation about three o rthogonal axes in the applied magnetic field. Analysis of the data yie lds the three principal components of the phosphorus chemical shift te nsor, delta(11) = 112 ppm, delta(22) = -23 ppm, and delta(33) = -40 pp m; delta(22) lies close to the Mo-P bond (8 degrees), while delta(11) lies in the approximate mirror plane. The phosphorus chemical shift te nsor determined for 1 is compared with the limited anisotropic phospho rus shift data available in the literature.