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.

EPR Spectroscopy of catalytic systems based on nickel complexes of 1,4-diaza-1,3-butadiene (α-diimine) ligands in hydrogenation and polymerization reactions

“…The broadening of the signal is caused by the nickel center. 13 The signals from the nickel (I) complex become isotropic at room temperature.…”

Metal–Organic Frameworks (MOFs) of a Cubic Metal Cluster with Multicentered MnIMnI Bonds

“…[1, 2] In construction and design of MOFs with characteristic properties and functions,m etal ions play ac rucial role. [14] These compounds all contained dinuclear metals (except In) and were obtained by using sterically demanding ligands.M ost of them are unstable in air.S of ar multicentered Mn I À Mn I bonded polyatomic clusters have not yet been reported, although dinuclear Mn I À Mn I bonded compounds are known. [3] In more than 25 000 MOF-related publications,c luster-based MOFs with low-oxidation-state (LOS) metals and multicentered metal-metal bonding were unknown until recently when aZ n 8 cluster was synthesized.…”

“…[3] In more than 25 000 MOF-related publications,c luster-based MOFs with low-oxidation-state (LOS) metals and multicentered metal-metal bonding were unknown until recently when aZ n 8 cluster was synthesized. [14] These compounds all contained dinuclear metals (except In) and were obtained by using sterically demanding ligands.M ost of them are unstable in air.S of ar multicentered Mn I À Mn I bonded polyatomic clusters have not yet been reported, although dinuclear Mn I À Mn I bonded compounds are known. Among all the elements in the periodic table,t he lowest oxidation state is À4f or carbon, [5a] and the highest oxidation state is + 9f or iridium.…”

“…[5b] Due to their low electronegativity,m etals tend to have high oxidation states,w hereas LOS of metals are rare and often offer opportunity for unique electronic structures and properties.R ecently,t he number of LOS metal-metal bonded compounds have rapidly increased since Carmonas report of the singly bonded zinc(I) dimer [Cp*ZnZnCp*] (Cp* = C 5 Me 5 ). [14] These compounds all contained dinuclear metals (except In) and were obtained by using sterically demanding ligands.M ost of them are unstable in air.S of ar multicentered Mn I À Mn I bonded polyatomic clusters have not yet been reported, although dinuclear Mn I À Mn I bonded compounds are known. [14] These compounds all contained dinuclear metals (except In) and were obtained by using sterically demanding ligands.M ost of them are unstable in air.S of ar multicentered Mn I À Mn I bonded polyatomic clusters have not yet been reported, although dinuclear Mn I À Mn I bonded compounds are known.…”

“…[6] An umber of M I À M I bonded compounds have been synthesized, including M = Cd, [7,12d] Cr, [8] In, [9] Mg, [10] Fe, [11, 12e] Mn, [12] Co, [13] and Ni. [14] These compounds all contained dinuclear metals (except In) and were obtained by using sterically demanding ligands.M ost of them are unstable in air.S of ar multicentered Mn I À Mn I bonded polyatomic clusters have not yet been reported, although dinuclear Mn I À Mn I bonded compounds are known. [12] In this work, we report the synthesis of the first polyatomic Mn I compound {[Mn I 8 Mn II 3 (H 2 O) 6 (HL) 12 ]-(OH) 2 ·17 H 2 O} n (1)( L = tetrazole dianion), which features + 1o xidation state,m ulticenter Mn I À Mn I bonding, and the shortest Mn I À Mn I distance.T he chemical stability,m agnetic properties,e lectronic structure,a nd bonding character are also investigated.Air-a nd moisture-stable crystals of 1 were prepared by in situ [2+ +3] cycloaddition reaction of NaN 3 ,K C(CN) 3 ,a nd MnCl 2 in amixture of H 2 Oand EtOH (v/v = 4:1) at 145 8 8Cfor 72 h. Single-crystal X-ray diffraction (SCXRD) analyses reveal that 1 crystallizes in the cubic system with space group Pm3m.T wo crystallographically independent Mn centers exist in each asymmetric unit (Figure 1and Figure S1 in the Supporting Information, SI).…”