title: Terminal U≡E (E = N, P, As, Sb, and Bi) bonds in uranium complexes: a theoretical perspective.
abstract: The compound L-U-N [L = [N(CH2CH2NSiPr(i)3)3](3-), Pr(i) = CH(CH3)2] containing a terminal U-N triple bond has been synthesized and isolated successfully in experiments. To investigate the trend in the bonding nature of its pnictogen analogues, we have studied the L-U-E (E = N, P, As, Sb, and Bi) complexes using the scalar relativistic density functional theory. The terminal U-E multiple bond length increases in the order of U-N ≪ U-P < U-As < U-Sb < U-Bi, which can be supported by the hard and soft acids and bases (HSAB) theory. The U-E bond length, molecular orbital (MO), and natural bond orbital (NBO) reveal that the terminal U-E bonds should be genuine triple bonds containing one σ- and two π-bonding orbitals. Quantum theory of atoms in molecules (QTAIM) topological analysis and the electron localization function (ELF) suggest that the terminal U-E bond possesses covalent character and the covalency of U-E bonds decrease sharply when the terminal atom becomes heavier. This work presents a comparison about the bonding characteristic between the terminal U≡N bond and its heavier pnictogen (P, As, Sb, and Bi) analogues. It is expected that this work would shed light on the evaluation of the amount of 5f orbital participation in multiple bonds and further facilitate our deeper understanding of f-block elements.
authors.affiliation: Key Laboratory of Nuclear Radiation and Nuclear Energy Technology and Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety, Institute of High Energy Physics, Chinese Academy of Sciences , Beijing 100049, China.
authors.forename: Qun-Yan
authors.initials: QY
authors.lastname: Wu
authors.forename: Jian-Hui
authors.initials: JH
authors.lastname: Lan
authors.forename: Cong-Zhi
authors.initials: CZ
authors.lastname: Wang
authors.forename: Yu-Liang
authors.initials: YL
authors.lastname: Zhao
authors.forename: Zhi-Fang
authors.initials: ZF
authors.lastname: Chai
authors.forename: Wei-Qun
authors.initials: WQ
authors.lastname: Shi
mesh_terms: D000965:Antimony / Q000737:chemistry; D001151:Arsenic / Q000737:chemistry; D001729:Bismuth / Q000737:chemistry; D008968:Molecular Conformation; D009584:Nitrogen / Q000737:chemistry; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D010758:Phosphorus / Q000737:chemistry; D011789:Quantum Theory; D014501:Uranium / Q000737:chemistry*
chemical_list: D009942:Organometallic Compounds; D010758:Phosphorus; D014501:Uranium; D000965:Antimony; D001151:Arsenic; D009584:Nitrogen; D001729:Bismuth