Yukihiro Yokoyama

AB INITIO MO CALCULATIONS OF 31P-7Li COUPLING CONSTANTS IN LITHIUM PHOSPHIDES

The NMR 3 1P —TLi spin—spin coupling constants, 1Jpi j , in LiPH2 and LiP(CH 3 ) 2 monomers and LiPH2 oligomers were calculated by the ab initio self-consistent perturbation method. The calculated 1 J P L i values of the monomers depend largely on hybridization of the Ρ atom; pyramidal forms have much smaller 1 J P L j values than planar forms. The 1JpLi value also depends on solvation. Both the planar and pyramidal structures are suggested for lithium phosphide monomers in solution. The 1 J P L i value of the cyclic dimer also depends on solvation and is reduced by 40 % when two H 2 0 molecules Eire coordinated at each lithium atom. The cyclic trimer is predicted to have a 1 J P L i value similar to that of the cyclic dimer, although the 2 J P P values in the cyclic dimer and trimer are largely different from each other.