A phosphorus-31 NMR study of solid carbonylhydridotris(triphenylphosphine)rhodium(I). Unusual MAS sideband intensities in second-order NMR spin systems
1992; NRC Research Press; Volume: 70; Issue: 3 Linguagem: Inglês
10.1139/v92-114
ISSN1480-3291
AutoresGang Wu, Roderick E. Wasylishen, Ronald D. Curtis,
Tópico(s)Molecular spectroscopy and chirality
ResumoThe CP/MAS 31 P NMR spectrum of carbonylhydridotris(triphenylphosphine)rhodium(I), RhH(CO)(PPh 3 ) 3 (1), can be described as a tightly coupled ABMX spin system (X = 103 Rh). In contrast to the solution 31 P NMR spectrum, the three equatorial phosphorus nuclei are nonequivalent in the solid state and this structural feature allows us to measure the two-bond spin–spin couplings, 2 J( 31 P, 31 P). A new method is proposed for extracting the principal components of the chemical shift tensor from slow MAS NMR spectra in a tightly J-coupled two-spin system. For compound 1, the principal components of the 31 P chemical shift tensors calculated using this method are in good agreement with those obtained from NMR spectra of a static sample. The principal components of the 31 P chemical shift tensors determined for 1 are compared with those reported previously for Wilkinson's catalyst, RhCl(PPh 3 ) 3 . The δ 22 component of the 31 P chemical shift tensors in 1 shows the largest variation with structure. This is ascribed to differences in the orientation of the P—C ipso bond about the equatorial plane of the trigonal bipyramidal structure. Keywords: rhodium–phosphine compounds, AB spin system, 31 P chemical shift tensor, magic-angle spinning, molecular structure.
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