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

Ab initio calculations of 31 P 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 2 H 5 )(CH 3 ) 2 , P(C 2 H 5 ) 2 (CH 3 ), P(C 2 H 5 ) 2 (CHC 2 H 6 ), P(C 2 H 5 )(CHC 2 H 6 ) 2 , P(CHC 2 H 6 ) 3 , P(CHC 2 H 6 ) 2 (C(CH 3 ) 3 ), P(CHC 2 H 6 )(C(CH 3 ) 3 ) 2 and P(C(CH 3 ) 3 ) 3 . The calculation of the 31 P 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.