Theoretical QTAIM, ELI-D, and Hirshfeld Surface Analysis of the Cu–(H)B Interaction in [Cu₂(bipy)₂B₁₀H₁₀]

Abstract

Interaction of [Cu2B10H10] with 2,2'-bipyridine (bipy) afforded a novel binuclear discrete complex of the [Cu2(bipy)2B10H10] composition. Two copper(I) atoms coordinate a bridge boron cage through an apical edge and a triangular BBB face situated at its opposite apical vertices to form four 3c2e (CuHB) and one 2c2e Cu-B bonds. The charge density model was obtained by density functional theory calculations of isolated molecule and crystal. The resultant densities were analyzed using the quantum theory of atoms in molecules (QTAIM) and electron localizability indicator (ELI-D). The geometry and the topological parameters of copper(I) coordination environment were found to be sensitive to crystal-field effect. An annulus of flat electron density ρ(r) and small ∇(2)ρ(r) is formed at dianion faces. As a result, some of the expected B-B, Cu-B, or Cu-H bond critical points are absent. The topological instability in the region of multicentered bonds is observed. The Cu-B bonding was found to be presumably electrostatic in nature, which could be the reason of topological isomerism for copper(I) decaborates. The results show that an unambiguous real-space criterion for multicentered bonding between transition metals and polyhedral boron anions is not yet given. The molecular graph for this class of compounds does not provide a definitive picture of the chemical boding and can be complemented with other descriptors, such as virial graphs and the ELI-D distribution.

Studies of Multicenter and Intermolecular Dihydrogen B–H···H–C Bonding in [4,8,8′‐exo‐{PPh3Cu}‐4,8,8′‐(μ‐H)3‐commo‐3,3′‐Co(1,2‐C2B9H9)(1′,2′‐C2B9H10)]

“…", respectively). In contrast with the previously reported [Cu 2 bipy 2 B 10 H 10 ] [30] both covalent and coordination Cu-P, Cu-H, Co-C, and Co-B bonds are similar for both models. For these models we succeeded in finding all expected bond, ring, and cage critical points (bcp, rcp, and ccp) in the Cobdc -anion and the [CuPPh 3 ] + cation (Figure 1, b), although the numbers of Cu···H bcps differ.…”

“…Vice versa, on the basis of ρ(r) values at Cu-H bcps (0.28-0.48 e Å -3 , in comparison with 0.59 e Å -3 ), the B-H···Cu bonds between Cu + and Cobdc -are expected to be weaker than those between Cu + and B 10 H 10 2-(ref. [30] ). The Cu-P1 bond is the only one out of the coordination bonds that has small ellipticity (e.g., cylindrical symmetry); ellipticities of Cu-H, Co-B, and Co-C bonds exceed 0.3; thus, topological instability and low curvature of the ED in the region of these bonds are expected.…”

“…In this method, topological analysis of the three-dimensional ED is carried out to divide space into atomic basins with surfaces of zero electronic flux. The presence of a bond is associated with the appearance of the bond critical point (bcp), the saddle point in the scalar field of the ED, but one should take into account that QTAIM topology may show ambiguities in bonding scenarios of molecular species with delocalized charge density, such as sandwich or half-sandwich transition-metal complexes [28] and polyhedral boranes [29,30] that are recognized having delocalized charge density. Moreover, the resulting atomic connectivity for such compounds can depend on the quality of experimental data or the DFT functional in theoretical calculations.…”

“…The ELI-D domains are regions with the same amount of same-spin electron pairs; these are given on an absolute scale and can thus be com-pared for different molecular systems and allow polar and nonpolar contributions to the bonding to be distinguished. [34] Application of the ELI-D has been found to be helpful in investigation of deltahedral boranes, [29] metallaboranes, [30] zincocenes, [35,36] and metal-metal bonding. [37,38] Previously, one of our research group has reported that the anionic Cobdc cluster, on treatment with a source of [Cu(PPh 3 [39] According to the X-ray diffraction study of 1, [39] the exopolyhedral {Cu(PPh 3 )} moiety is bound to the commo-metallacarborane framework through three unique (B-H) 3 ···Cu agostic bonds involving one and two B-H vertices in the pentagonal faces of both {C 2 B 9 }-ligands.…”

Silver and Copper Complexes with closo-Polyhedral Borane, Carborane and Metallacarborane Anions: Synthesis and X-ray Structure

“…However, a few examples of the facial coordination of the closo-decaborate anion were revealed. The reactions of Cu 2 [B 10 H 10 ] with chelate ligands 2,2 1 -bipyridine (2,2 1 -Bipy) and 1,10-phenanthroline (Phen) in acetonitrile result in formation of copper(I) complexes {((L)Cu) 2 [B 10 H 10 ]} with facial and mixed edge-facial coordination mode of metal atoms by the closo-decaborate anion [42]. In the complex {((2,2 1 -Bipy)Cu) 2 The metal coordination mode in the closo-decaborate complexes depends on steric effects of ligands and their basicity, whereas the formation of specific positional isomers is strongly governed by the reaction conditions.…”