The structure and chemical bonding in the N2CuX and N2···XCu (X = F, Cl, Br) systems studied by means of the molecular orbital and Quantum Chemical Topology methods

✍ Scribed by Karolina Kisowska; Slawomir Berski; Zdzislaw Latajka

• Publisher: John Wiley and Sons
• Year: 2008
• Tongue: English
• Weight: 549 KB
• Volume: 29
• Category: Article
• ISSN: 0192-8651
• DOI: 10.1002/jcc.21010

✦ Synopsis

Abstract

Ab initio studies carried out at the MP2(full)/6‐311+G(2df) and MP2(full)/aug‐cc‐pVTZ‐PP computational levels reveals that dinitrogen (N~2~) and cuprous halides (CuX, X = F, Cl, Br) form three types of systems with the side‐on and end‐on coordination of N~2~: NNCuX (C~∞v~), N~2~CuX (C~2v~) stabilized by the donor–acceptor bonds and weak van der Waals complexes N~2~···XCu (C~2v~) with dominant dispersive forces. An electron density transfer between the N~2~ and CuX depends on type of the N~2~ coordination and a comparison of the NPA charges yields the [NN]^δ+^‐[CuX]^δ−^ and [N~2~]^δ−^‐[CuX]^δ+^ formula. According to the NBO analysis, the CuN coordinate bonds are governed by predominant LP~N2~→σ*(CuX) “2e‐delocalization” in the most stable NNCuX systems, meanwhile back donation LP~Cu~→π*(NN) prevails in less stable N~2~CuX molecules. A topological analysis of the electron density (AIM) presents single BCP between the Cu and N nuclei in the NNCuX, two BCPs corresponding to two donor‐acceptor CuN bonds in the N~2~CuX and single BCP between electron density maximum of the NN bond and halogen nucleus in the van der Waals complexes N~2~···XCu. In all systems values of the Laplacian ∇^2^ρ(r)(r~BCP~) are positive and they decrease following a trend of the complex stability i.e. NNCuX (C~∞v~) > N~2~CuX (C~2v~) > N~2~···XCu (C~2v~). A topological analysis of the electron localization function (ELF) reveals strongly ionic bond in isolated CuF and a contribution of covalent character in the CuCl and CuBr bonds. The donor–acceptor bonds CuN are characterized by bonding disynaptic basins V(Cu,N) with attractors localized at positions corresponding to slightly distorted lone pairs V(N) in isolated N~2~. In the NNCuX systems, there were no creation of any new bonding attractors in regions where classically the donor–acceptor bonds are expected and there is no sign of typical covalent bond CuN with the bonding pair. Calculations carried out for the NNCuX reveal small polarization of the electron density in the NN bond, which is reflected by the bond polarity index being in range of 0.14 (F) to 0.11 (Cl). © 2008 Wiley Periodicals, Inc. J Comput Chem 2008