Abstract
Local energy decomposition (LED) analysis decomposes the interaction energy between two fragments calculated at the domain-based local pair natural orbital CCSD(T) (DLPNO-CCSD(T)) level of theory into a number of chemically meaningful contributions. Herein, this scheme is applied to the interaction between the transition metal (TM) and the alkane in σ-complexes. It is demonstrated that the often-neglected London dispersion (LD) energy is a fundamental component of the TM-alkane interaction for a wide range of experimentally characterized σ-complexes. LD effects determine the structure and the thermodynamic stability of σ-complexes and influence the selectivity of CH activation reactions. The magnitude of the LD energy can be modulated by increasing the size of the alkane and of the ancillary ligands on the TM. These results provide further evidence on the fundamental role that London dispersion plays in organometallic chemistry.
Highlights
The London dispersion (LD) energy constitutes the attractive part of the van der Waals potential and it is omnipresent in chemistry
Recently,[28,29,30] we proposed a new strategy called Local Energy Decomposition (LED) analysis, which provides a decomposition of interaction energies computed at the domain-based local pair natural orbital coupled cluster DLPNO-CCSD(T)[31,32,33] level into various terms representing the most important chemical components of the interaction
The ReÁ Á ÁCH4 binding energy profile as a function of the ReÁ Á ÁC distance calculated at the DLPNO-CCSD(T) level of theory is shown in the upper panel of Fig. 1
Summary
The London dispersion (LD) energy constitutes the attractive part of the van der Waals potential and it is omnipresent in chemistry. In the Symmetry Adapted Perturbation Theory (SAPT) framework,[2] the leading dipole–dipole term of the LD energy grows with the polarizabilities of the interacting fragments and decays asymptotically as RÀ6, with R being the interfragment distance.[3] as the molecular system size increases, the magnitude of the LD energy increases, often making it stronger than covalent or electrostatic interactions.[4] Due to its size dependence, LD is responsible for the stability of seemingly too crowded molecules, such as diamantyl,[5] all-meta tBu-triphenylmethane,[6] and all-meta tBu-hexaphenylethane dimers.[7] its importance has been widely recognized in biochemistry,[8] material science,[9] and organic chemistry.[10]. The interaction between a transition metal (TM) and a ligand (L) is still often described as a simple donor–acceptor interaction and the structure, the catalytic behaviour and the spectroscopic properties of TM complexes are in most cases discussed using orbital models such as the popular Dewar–Chatt–Duncanson (DCD) bonding model.[23,24]
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