Proton magnetic resonance spectra of tri-2-pyridylphosphine and the corresponding phosphine oxide and sulphide

Abstract

The 100 MHz spectra of the title compounds are described, and the chemical shifts and coupling constants are obtained by analysis and refined by an iterative computer programme. Double-resonance techniques have established the relative signs of the ³¹P–¹H coupling constants; the two four-bond couplings have opposite signs whereas the three- and five-bond couplings have the same sign, implying a negative sign for ⁴J_HP through nitrogen. The effect of the valence of the phosphorus atom on the parameters is discussed.