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

Abstract

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.