An experimental and DFT analysis of coupling constants in [31P(CH3)nH(4−n)]+ systems where n = 0–4 with a note on [14N(C2H5)4]+ and [31P(C2H5)4]+

The experimentally determined coupling constants of phosphonium cations of general formula [P(CH3)nH(4−n)]+ where n = 0–4 have been gathered and those corresponding to P(CH3)4+ measured again. They have been compared with the coupling constants computed at the B3LYP/6-311++G(d,p)//B3LYP//6-311++G(d,p) level. The agreement is highly satisfactory save for 1JPC and for 1JPH. The last problem is probably related to specific solvation through hydrogen bonds. The cases of P(C2H5)4+ and N(C2H5)4+ were also examined to provide a basis for the fact that β protons show a large coupling constant with 14N than α protons.