Boron-carbon coupling constants. III. Determination and calculation of JBC in some simple organoboranes

Reaction of pentaarylboroles with carbon monoxide: an isolable organoboron carbonyl complex

“…The lack of observable 11 B- 13 C coupling in these resonances argues against this assignment, but may be due to partial decoupling by boron quadrupolar relaxation effects. 28 The more downfield resonance at 145.9 ppm may be due to the trapping of acyl borane A by borole 2 rather than dimerization to form adduct B.…”

Reactions of Cyanoboranes with a Palladium−PMe3 Complex: Mechanism for the Catalytic Cyanoboration of Alkynes

“…The cyanoborane 1d - 13 C was prepared by reaction of the corresponding chloroborane with TMS- 13 CN . The 11 B NMR spectrum showed a doublet at 15.9 ppm ( J B - C = 108 Hz), while the corresponding coupled signal was observed at 119.7 ppm ( J B - C = 100−110 Hz) as a broad quartet in the 13 C NMR spectrum . On reacting 1d - 13 C with “Pd(PMe 3 ) 2 ”, gradual conversion of 1d - 13 C into a new palladium complex was observed until ca.…”

13C NMR of the Tetrakis(phenylethynyl)borate Anion and of Some Phenylethynyl Boranes

“…Indirect nuclear spin-spin coupling between sphybridized carbon and boron (sp 3 ) has been observed for H3B-C-O (30.2 Hz) and for H3B-C=N~ (53.0 Hz) [1], Although a considerable number of other coupling constants 1 J( 13 C U B) with various states of hybridisation of carbon and boron are known [2] data for alkynyl borates are still missing. Considering the quadrupole moment of the n B nucleus tetrakis(alkynvl)borates [(R-C =C)4B]-should be most suitable to obtain accurate values J( 13 C U B) by natural abundance 13 C NMR spectra.…”