Heteronuclear magnetic triple resonance. Signs of the B—H and B—P spin-spin coupling constants

Heteronuclear triple resonance experiments are used to lift the degeneracy in the proton spectrum of trimethylphosphite borane arising from the effectively zero value of 4J(11B…H) and to show that 1J(11B—31P) is positive. Double resonance experiments are used to give the signs of 1J(11B—H) +ve, 2J(31P…H) –ve, and 2J(13C…31P) –ve. The electronic environments of boron and carbon in BH3 and CH3 groups appear to be very similar