Tp. Hamilton et al., HP4- - THE MONOCONJUGATE BASE FROM TETRAPHOSPHABICYCLOBUTANE - EVIDENCE FOR AN EXO GROUND-STATE CONFORMATION IN THE GAS-PHASE, Chemical physics letters, 208(1-2), 1993, pp. 106-110
Ab initio theoretical studies reconsider recent experimental findings
concerning the ground state conformation of the HP4-anion. Basis sets
as large as triple zeta plus double polarization plus f functions plus
diffuse functions (TZ2Pf+diffuse) were used in connection with method
s that explicitly include the effects of electron correlation. At the
highest level of theory, the exo structure is predicted to lie about t
wo kcal/mol below the endo structure, in apparent disagreement with ex
periment. The Li+HP4-system has also been examined to approximate more
closely the system synthesized in the laboratory. The energetics are
significantly shifted by the appendage of the Li+ cation, and the agre
ement between theory and experiment deteriorates further.