Charge-displacement analysis via natural orbitals for chemical valence: Charge transfer effects in coordination chemistry

Abstract

We recently devised a simple scheme for analyzing on quantitative grounds the Dewar-Chatt-Duncanson donation and back-donation in symmetric coordination complexes. Our approach is based on a symmetry decomposition of the so called Charge-Displacement (CD) function quantifying the charge flow, upon formation of a metal (M)-substrate (S) bond, along the M-S interaction axis and provides clear-cut measures of donation and back-donation charges in correlation with experimental observables [G. Bistoni et al., Angew. Chem., Int. Ed. 52, 11599 (2013)]. The symmetry constraints exclude of course from the analysis most systems of interest in coordination chemistry. In this paper, we show how to entirely overcome this limitation by taking advantage of the properties of the natural orbitals for chemical valence [M. Mitoraj and A. Michalak, J. Mol. Model. 13, 347 (2007)]. A general scheme for disentangling donation and back-donation in the CD function of both symmetric and non-symmetric systems is presented and illustrated through applications to M-ethyne (M = Au, Ni and W) coordination bonds, including an explicative study on substrate activation in a model reaction mechanism.

Perspective: Found in translation: Quantum chemical tools for grasping non-covalent interactions

“…Owing to the numerous levels of accuracy possible, including multireference variants, 41,74 it is also possible to treat strongly correlated systems 75 and molecules having elongated bonds. Owing to an unambiguous definition of CT, EDAs are often used to identify and quantify charge transfer interactions, 22,27,48,76 frequently in conjunction with ALMO-CTA, 77,78 which is complementary to ALMO-EDA.…”

On the relation between carbonyl stretching frequencies and the donor power of chelating diphosphines in nickel dicarbonyl complexes

“…31 While such scheme has been described in detail in ref. 31, we briefly review here its foundations for a clearer reading of the forthcoming discussion.…”

“…Whereas, in fact, the NOCV eigenvalues provide a measure of the charge flowing between NOCV orbital pairs, this can hardly be taken as an estimation of the charge transfer between fragments as NOCV eigenvalues also include intra-fragment charge rearrangement. 31 That's where charge-displacement (CD) analysis comes into play.…”

“…31 The NOCV analysis was performed by interfacing G09 with an ad hoc written program‡ ‡S. Rampino, The WAVERLEY program package, see (accessed 4 January 2017).…”

“…Then, based on density functional theory (DFT) calculations, we carry out a thorough theoretical analysis (Section 3.2) of the metal–ligand chemical bond by means of a powerful, recently proposed analysis scheme, namely the natural orbitals for chemical valence/charge displacement (NOCV/CD) method. 31 Through the NOCV/CD analysis we give a quantitative, spatially detailed description of the several charge fluxes following the metal–ligand bond formation and show that the carbonyl stretching frequencies in the considered complexes selectively respond to the σ-donation charge flow from the phosphorus lone pairs of the ligands, with the frequency shift being in quantitative correlation with the ligand-to-metal transferred charge. We draw conclusions and outline perspectives for future work in the last section (Section 4).…”