Investigation of the differences in stability of the OC⋅⋅⋅HF and CO⋅⋅⋅HF complexes

Abstract

The structure and energetics of the isomeric H-bonded complexes OC⋅⋅⋅HF and CO⋅⋅⋅HF have been investigated by ab initio molecular orbital theory and by natural bond orbital analysis. Only with the inclusion of electron correlation is a significant preference for the experimentally observed OC⋅⋅⋅HF isomer found. The large effect of correlation upon the relative stability of the two isomers is apparently entirely an electrostatic effect caused by the correlation-induced sign reversal of the dipole moment of CO. Nevertheless, a molecular multipole expansion is found inadequate to account for the principal features of these H-bonded complexes and their relative stability. Contrary to a recent study, we find that ‘‘charge transfer’’ effects are highly significant contributions to the binding in these complexes. The differences in stability of OC⋅⋅⋅HF and CO⋅⋅⋅HF are attributed primarily to differences in the interaction of carbon and oxygen lone pairs of CO donating into the unfilled antibond on HF, i.e., to differences in nC→σHF* and nO→σHF* matrix elements.

On the Relation between π Bonding, Electronegativity, and Bond Angles in High-Valent Transition Metal Complexes

“…The bonding analyses presented in this work are based mostly on the NBO/NLMO procedure of Weinhold et al [26,27] The data do thus of course contain some degree of arbitrariness, as is true for any type of population analysis or density-matrix partitioning scheme. Complications arise also from the inherently ill-defined nature of in-plane p and s bonding for nonlinear molecules.…”

“…Natural population analyses (NPA), natural bond orbital (NBO), and natural localized molecular orbital (NLMO) analyses [26,27] have been carried out with the built-in NBO subroutines of the Gaussian94 program. [21] Desired Lewis structures based on a representation of the one-particle density matrix in the basis of strictly localized NBOs have been selected by the $CHOOSE keyword of the NBO code if necessary.…”

The crystal and molecular structure of N2H5[M(N2H3COO)3]·H2O (M∈{Co, Zn}) isomorphic compounds—an X-ray crystallographic, vibrational spectroscopic and quantum-chemical study

“…Obviously, the magnitude of transferred charge within the cluster is quite relevant from the stabilization aspect, especially having in mind that it has been emphasized that even seemingly small values of transferred charge (0.001-0.01e) lead to chemically significant stabilization energies [31][32][33][34][35][36].…”

“…The ''best'' such hybrid orbitals for a given molecular system may be related to the molecular geometry, as has been thoroughly discussed [31][32][33][34][35][36]. Since the hydrazidocarbonate anion coordinates to the metal cation through the NH 2 group nitrogen atom, the NH bonds are formed from the sp l hybrids with more pronounced p character compared to the NH bonds of the NH 2 group within the NH 2 NH 3 + species, which ''contains'' a lone pair on nitrogen.…”

“…On the basis of the natural hybrid orbital concept [31][32][33][34][35][36], one can attribute such geometric features to the basic type of hybridization on the neighboring C1, C2, C3 and N2, N4, N6 atoms (almost sp 2 and sp 3 , respectively). M II -O distances are shorter than M II -N. In the case of the Zn(II) complex, this is due to the much more pronounced charge-transfer interaction from carboxyl group oxygen atom to the central Zn 2+ cation, than from the NH 2 group nitrogen atom to the cation.…”