Characterizing complexes with F-Li+-F lithium bonds: structures, binding energies, and spin-spin coupling constants

Ab initio MP2/aug-cc-pVTZ calculations have been performed to determine the structures and binding energies of complexes with F-Li(+)-F bonds formed from the fluorine bases LiF, CH(3)F, HF, ClF, and FF. There is only a single minimum across the Li(+) transfer coordinate, and in each series, the lithiated homodimer is stabilized by a symmetric F...Li(+)...F bond. Complexes having LiF, CH(3)F, and HF as the base have similar structures, with linear F-Li(+)-F bonds and a head-to-tail alignment of the F-Li(+) bond dipole with the dipole moment vector of the base. In each series with a given acid, the binding energy decreases as the difference between the lithium ion affinities increases. EOM-CCSD coupling constants (1)J(F-Li), (1li)J(Li-F), and (2li)J(F-F) have also been evaluated. In complexes with essentially linear bonds, (2li)J(F-F) values are small and positive and increase quadratically as the F-F distance decreases. (1li)J(Li-F) and (1)J(F-Li) also vary systematically with distance. Comparisons are made between structural, energetic, and coupling constant properties of these complexes and corresponding complexes stabilized by F-H(+)-F hydrogen bonds.