Ab initio calculations of 31P NMR chemical shielding tensors in alkyl phosphorus compounds and comparison with experimental values

Abstract

Ab initio calculations of 31P nuclear shielding were performed as a function of the number of carbon atoms in twelve alkyl phosphorus compounds: PH 3, PH 2(CH 3), PH(CH 3) 2, P(CH 3) 3, P(C 2H 5)(CH 3) 2, P(C 2H 5) 2(CH 3), P(C 2H 5) 2(CHC 2H 6), P(C 2H 5)(CHC 2H 6) 2, P(CHC 2H 6) 3, P(CHC 2H 6) 2(C(CH 3) 3), P(CHC 2H 6)(C(CH 3) 3) 2 and P(C(CH 3) 3) 3. The calculation of the 31P shielding tensors employed the GAUSSIAN 98 implementation of the gauge-including atomic orbital (GIAO) and continuous set of gauge transformations (CSGT) by using 6-311++G(2d,2p) basis set methods at both the Hartree–Fock (HF) and density functional levels of theories (DFT). A good linear correlation between the calculated chemical shielding at gas-phase and experimental shift values was obtained.