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)(n)H(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 (1)J(PC) and for (1)J(PH). 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 P protons show a large coupling constant with N-14 than alpha protons. (c) 2006 Elsevier B.V. All rights reserved.