title: Pentagonal five-center four-electron π bond in ternary B3N2H5cluster: an extension of the concept of three-center four-electron ω bond.
abstract: Boron-based heteroatomic rings can have exotic chemical bonding, in which the p lone-pairs of heteroatoms manage to participate in delocalized π bonding, compensating for boron's electron-deficiency. We explore herein the bonding properties of ternary B-N-H systems with a pentagonal ring, using the B3N2H50/-/2-clusters as examples. Computational structural searches lead to perfectly planar C2vB3N2H5(1,1A1) and C2vB3N2H5-(2,2B1) as global minima for the neutral species and monoanion, which feature a pentagonal B3N2ring. The corresponding dianion C2vB3N2H52-(3,1A1) is a local minimum, whose global minimum adopts a chain-like open structure. Bonding analyses reveal a five-center four-electron (5c-4e) π system in 1, dubbed the 5c-4e o-bond. It is a 4π system in the bonding/nonbonding combination, originating from two N 2p lone-pairs, which can be considered as an extension of the concept of 3c-4e ω-bond. The extra electrons in 2 and 3 occupy a markedly destabilized π orbital. Thus, a 4π configuration, rather than a π sextet according to the (4n + 2) Hückel rule, is electronically robust for the B3N2H50/-/2-system. Infrared and photoelectron spectra are predicted for 1 and 2, respectively. Structural evolution of ring-like and chain-like isomers with charge-state in B3N2H50/-/2-is elucidated. B3N2H5-(2) is used as ligand for sandwich-type complexes: C2h[(B3N2H5)2Fe]2-and C2h[(B3N2H5)2Fe]Li2.
authors.affiliation: Binzhou Key Laboratory of Materials Chemistry, Department of Chemical Engineering, Binzhou University, Binzhou 256603, P. R. China. ldz005@126.com.
authors.forename: Da-Zhi
authors.identifier: http://orcid.org/0000-0002-7338-7790
authors.initials: DZ
authors.lastname: Li
authors.affiliation: Nanocluster Laboratory, Institute of Molecular Science, Shanxi University, Taiyuan 030006, P. R. China. hj.zhai@sxu.edu.cn.
authors.forename: Lin-Yan
authors.initials: LY
authors.lastname: Feng
authors.affiliation: Binzhou Key Laboratory of Materials Chemistry, Department of Chemical Engineering, Binzhou University, Binzhou 256603, P. R. China. ldz005@126.com.
authors.forename: Ling
authors.initials: L
authors.lastname: Pei
authors.affiliation: Binzhou Key Laboratory of Materials Chemistry, Department of Chemical Engineering, Binzhou University, Binzhou 256603, P. R. China. ldz005@126.com.
authors.forename: Li-Juan
authors.initials: LJ
authors.lastname: Zhang
authors.affiliation: Binzhou Key Laboratory of Materials Chemistry, Department of Chemical Engineering, Binzhou University, Binzhou 256603, P. R. China. ldz005@126.com.
authors.forename: Shu-Guo
authors.initials: SG
authors.lastname: Wu
authors.affiliation: Nanocluster Laboratory, Institute of Molecular Science, Shanxi University, Taiyuan 030006, P. R. China. hj.zhai@sxu.edu.cn and State Key Laboratory of Quantum Optics and Quantum Optics Devices, Shanxi University, Taiyuan 030006, P. R. China.
authors.forename: Hua-Jin
authors.initials: HJ
authors.lastname: Zhai