A new tetraamidodimolybdenum complex with a quadruple<i>M</i>–<i>M</i>bond

Lichtenberger, Dennis L.; Kristofzski, J.G.; Bruck, Michael A.

doi:10.1107/s0108270188005025

Cited by 5 publications

(3 citation statements)

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“…The bond length of Mo1-Mo1A of 5 is 2.0612(4) , which is longer than those (2.02 ) of the only reported type II quintuply bonded dimolybdenum compounds [Mo 2 {m-h 2 -RC(N-2,6-iPr 2 C 6 H 3 ) 2 } 2 ] (R= H, Ph), [7c] but slightly shorter than the shortest MoÀMo quadruple bonds (2.063(1) ) in the tetrakisamidato dimolybdenum species [Mo 2 {tBuNC(Me)O} 4 ]. [19] To achieve the preparation of anionic complex 4 and then determine the MoÀMo bond length, efforts to remove Li + ion from 5 by the addition of two equiv of [12]crown-4 ether were not successful. In fact, the lack of oxygen donors at the Li atom implies that it is wellprotected by the four neighboring ethyl groups of the supporting amidinates.…”

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An Electron‐Rich Molybdenum–Molybdenum Quintuple Bond Spanned by One Lithium Atom

Liu

et al. 2012

Angew Chem Int Ed

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An Electron‐Rich Molybdenum–Molybdenum Quintuple Bond Spanned by One Lithium Atom

Liu

et al. 2012

Angew Chem Int Ed

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“…DFT calculations on the Li-spanned dimolybdenum trisamidinate complex 18 revealed the type IV quintuple bond with a Mo-Mo bond length of 2.0612(4) Å with a BO-NBO of 3.67, which is longer than those of 13 and 14, but slightly shorter than the shortest Mo-Mo quadruple bond length of 2.063(1) Å in the tetrakisamidato dimolybdenum species [Mo 2 {t-BuNC(Me)-O} 4 ]. 73 The quintuple bonded Mo 2+ moiety in 18 is electron rich, so it strongly binds a Li + cation, which spans the Mo-Mo quintuple bond with the Mo-Li bond order of 0.57.…”

Section: The Type III Configurationmentioning

confidence: 99%

Theory, synthesis and reactivity of quintuple bonded complexes

2014

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This perspective reviews recent advances in the newly discovered metal-to-metal quintuple bonded complexes. The idea of the structures of the metal-metal quintuple bonded complexes was initiated by theoreticians in 1979 and 2001 based on two types of model compounds, the D3h M2L6 and trans-bent M2H2, respectively. This theoretical hypothesis was put into practice in 2005 with the preparation of the first isolable quintuple bonded chromium terphenyl dimer Cr2Ar'2 (Ar' = 2,6-(2,6-i-Pr2C6H3)2C6H3). After this landmark discovery, many N-based donor-stabilized dinuclear group 6 quintuple bonded complexes with very short metal-metal separations have been identified by X-ray crystallography, and their quintuple bonding was corroborated by magnetic measurements and theoretical calculations. Unlike the quadruple bonded bimetallic units uniformly supported in a tetragonal environment, the configuration of the characterized quintuple bonded dinuclear complexes varies with the ligands and metals. Three types of quintuple bonded complexes have been identified to date. In addition to their geometry variation and interesting bonding schemes, these low-valent and low-coordinate quintuple bonded complexes are highly reducing and have been shown to be reactive towards small inorganic molecules and unsaturated organics.

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“…The formulation of 5 indicates its formation is also by a complicated ligand redistribution process, which explains its low yield. [19] To achieve the preparation of anionic complex 4 and then determine the MoÀMo bond length, efforts to remove Li + ion from 5 by the addition of two equiv of [12]crown-4 ether were not successful. In the 1 H NMR spectrum, two ligand environments in a ratio of 2:1 were observed.…”

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An Electron‐Rich Molybdenum–Molybdenum Quintuple Bond Spanned by One Lithium Atom

Liu

et al. 2012

Angewandte Chemie

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In the field of metal-metal multiple bonding, there are many factors that affect the metal-metal bond lengths. The most determinant cause is the structural configuration of complexes, [1] and this has been illustrated by the Group 6 metalmetal quadruple bonds. In the large number of tetragonal quadruply bonded complexes [M 2 X 8 ], [1] the increase in the internal twist angle between two MX 4 fragments leads to elongation of the metal-metal quadruple bond. [1,2] For example, those quadruply bonded dimolybdenum complexes with the torsion angles about the MoÀMo bond of 26-408 possess long MoÀMo bonds in the range of 2.18-2.19 , which is because a major part of the d bonding has been abolished.In contrast to the relatively mature metal-metal tripleand quadruple-bond chemistry, [1, 3] quintuple bonding is in its infancy. In contrast to the trigonal triply bonded and tetragonal quadruply bonded dinuclear complexes, the geometry of a quintuply bonded compound has been controversial. Theoretically, the most accepted configuration of a quintuple bonded complex is the type I trans-bent geometry (Scheme 1). [4] On the experimental side, the first quintuple bond, in [Cr 2 Ar' 2 ] (Ar' = 2,6-[2,6-(iPr 2 ) 2 C 6 H 3 ] 2 C 6 H 3 ) [5a] and derivatives, [5b] was reported by Power et al. It is worthy noting these remarkable complexes in fact adopt the type II geometry, although the central Cr 2 unit is stabilized by two monoanionic terphenyl ligands. Since then, many efforts have been dedicated to isolating dinuclear species featuring quintuple-bond character. For example, the groups of Theopold, [6] Tsai, [7] and Kempe [8] reported several type II quintuply bonded Cr 2 and Mo 2 complexes with extremely short metal-metal quintuple bonds spanned by two bidentate nitrogen-based ligands. The existence of the CrÀCr quintuple bond of the type II complex was recently corroborated by charge-density studies. [9] Preliminary reactivity studies on the type II complexes indicate these univalent and low-coordinate dinuclear species are reactive towards unsaturated organic functionalities and small molecules. [10,11] Compared to the many type II complexes, only one example of the type III complex, [Cr 2 {m-HC(N-2,6-Me 2 C 6 H 3 ) 2 } 3 ] À (1), was recently reported, although such type of species was proposed by Hoffmann et al. in 1979. [12] Unexpectedly, compound 1 possesses an ultrashort CrÀCr quintuple bond (1.74 ), [7a] which has also been supported by theoretical calculations. [7a, 13] The quintuply bonded Group 6 M 2 (M = Cr, Mo) complexes reported to date have very short M À M bond distances. Theoretical analysis on the type II Cr 2 complexes [6][7][8] implied that these short CrÀCr distances are associated with the steric bulk of the ligands. [13] Furthermore, computations on the quintuply bonded Group 6 model compounds M 2 X 2 (M = Cr, Mo, W; X = H, F, Cl, Br, CN, Me) revealed the MÀM bond distances vary with the structural conformation. [4f] Since the recognition of the structure of 1, we became interested in characterizin...

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A new tetraamidodimolybdenum complex with a quadrupleM–Mbond

Cited by 5 publications

References 4 publications

An Electron‐Rich Molybdenum–Molybdenum Quintuple Bond Spanned by One Lithium Atom

An Electron‐Rich Molybdenum–Molybdenum Quintuple Bond Spanned by One Lithium Atom

Theory, synthesis and reactivity of quintuple bonded complexes

An Electron‐Rich Molybdenum–Molybdenum Quintuple Bond Spanned by One Lithium Atom

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