Ab initioquantum-chemical calculations of interactions of ions and hydrides of alkali metals with C3H6and C4H8molecules

摘要

Calculations of the C3H6· LiH, C4H8· M+, and C4H8· MH systems and of C2H2· MH complexes (M = Li or Na) were carried out by the unrestricted Hartree-Fock-Roothaan (UHF) method with partial optimization of the geometry using fixed geometric parameters of the C3H6and C4H8molecules. The standard 3-21G and 6-31G* basis sets were used. Unlike the C3H6· LiH structure, the C4H8· M+and C4H8· MH systems are typical complexes. It was found that the C4H8· M+, C4H8· MH, and C2H2· MH complexes are similar in coordination of M+ions and MH molecules by carbon atoms in spite of considerable differences in the interatomic distances (−1 A) between these atoms in the C4H8and C2H2molecules. The heats of formation (Q), which were calculated in the UHF/6-31G* approximation and using second- and fourth-order Möller-Plesset perturbation theory taking into account the electron correlation energy in the MP2/6-31G*. MP4(SDQ)/6-31G*, and MP4(SDTQ)/6-31G* approximations, satisfy the following relationships: Q(C2H3· MH)