Multinuclear NMR spectroscopic studies of aryltrimethylsilanes and aryldimethylphosphaneboranes
Journal of Organometallic Chemistry
Proton, boron-11, carbon-13, silicon-29, and phosphorus-31 NMR chemical shifts and coupling constants are reported for nine ortho- and 2,6-disubstituted aryltrimethylsilanes and five similarly substituted aryldimethylphosphaneboranes. Resonances in the natural-abundance carbon-13 NMR spectra for both sets of derivatives are assigned on the basis of additivity relationships, proton-coupled spectra, and relative magnitudes of | J(31P13C) | coupling constants. Carbon-13 chemical shifts and |1J(13C1H) | coupling constants indicate that the P(BH3)(CH3)2 group is electron-withdrawing. The 13C chemical shifts of aryl C(5) carbons can be attributed to steric inhibition of resonance of about the same magnitude as that produced by ortho-Si(CH3)3. Chemical shift and coupling constant data from previous work are expanded in terms of Taft's dual substituent constants σ1 and σR0. Least squares solutions of these equations for aryldimethylphosphaneborane derivatives provide values of 0.41 for σ1 and 0.04 for σR0 for the P(BH3)(CH3)2 group. These constants produce reasonable agreement with observed 13C chemical shifts and coupling constants in the ortho derivatives. © 1989.
Albanese, Joseph A.; Gingrich, Diane E.; Schaeffer, Charles D.; Coley, Suzanne M.; Otter, Julie C.; Samples, Marjorie S.; and Yoder, Claude H., "Multinuclear NMR spectroscopic studies of aryltrimethylsilanes and aryldimethylphosphaneboranes" (1989). Faculty Publications. 1563.