title: Distinct stepwise reduction of a nickel-nickel-bonded compound containing an α-diimine ligand: from perpendicular to coaxial structures.
abstract: A nickel-nickel-bonded complex, [{Ni(μ-L(.-))}2] (1; L=[(2,6-iPr2C6H3)NC(Me)]2), was synthesized from reduction of the LNiBr2 precursor by sodium metal. Further controllable reduction of 1 with 1.0, 2.0 and 3.0 equiv of Na, respectively, afforded the singly, doubly, and triply reduced compounds [Na(DME)3]·[{Ni(μ-L(.-))}2] (2; DME=1,2-dimethoxyethane), [Na(Et2O)]Na[(L(.-))Ni-NiL(2-)] (3), and [Na(Et2O)]2Na[L(2-)Ni-NiL(2-)] (4). Here L represents the neutral ligand, L(.-) denotes its radical monoanion, and L(2-) is the dianion. All of the four compounds feature a short Ni-Ni bond from 2.2957(6) to 2.4649(8) Å. Interestingly, they display two different structures: the perpendicular (1 and 2) and the coaxial (3 and 4) structure, in which the metal-metal bond axis is perpendicular to or collinear with the axes of the α-diimine ligands, respectively. The electronic structures, Ni-Ni bonding nature, and energetic comparisons of the two structure types were investigated by DFT computations.
authors.affiliation: State Key Laboratory for Oxo Synthesis and Selective Oxidation, Lanzhou Institute of Chemical Physics, CAS, Lanzhou 730000 (P.R. China).
authors.forename: Qingsong
authors.initials: Q
authors.lastname: Dong
authors.forename: Xiao-Juan
authors.initials: XJ
authors.lastname: Yang
authors.forename: Shida
authors.initials: S
authors.lastname: Gong
authors.forename: Qiong
authors.initials: Q
authors.lastname: Luo
authors.forename: Qian-Shu
authors.initials: QS
authors.lastname: Li
authors.forename: Ji-Hu
authors.initials: JH
authors.lastname: Su
authors.forename: Yanxia
authors.initials: Y
authors.lastname: Zhao
authors.forename: Biao
authors.initials: B
authors.lastname: Wu
keywords: low oxidation state; metalmetal bonding; nickel; reduction