Group 6 Metal–Metal Bonds

Chisholm, Malcolm H.; Patmore, Nathan J.

doi:10.1002/9783527673353.ch6

Cited by 10 publications

(19 citation statements)

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“…A review by Chisholm and Patmore deals with more recent developments. 150 The chemistry of metal−metal multiply bonded compounds actually dates back to 1844, long before any understanding of chemical bonding whatsoever, when Peligot reported the synthesis of a hydrated chromium carboxylate complex, now believed to have been Cr 2 (O 2 CCH 3 ) 4 •2H 2 O containing a Cr−Cr quadruple bond. 6 The dark red color of this binuclear chromium(II) acetate is striking in view of the light blue aqueous Cr(II) solution from which it is precipitated by addition of acetate.…”

Section: Chromium−chromium Bondsmentioning

confidence: 99%

“…Binuclear chromium complexes with multiple bonds have been amply reviewed by Cotton, chiefly with regard to tetragonal paddlewheel complexes. A review by Chisholm and Patmore deals with more recent developments . The chemistry of metal–metal multiply bonded compounds actually dates back to 1844, long before any understanding of chemical bonding whatsoever, when Peligot reported the synthesis of a hydrated chromium carboxylate complex, now believed to have been Cr 2 (O 2 CCH 3 ) 4 ·2H 2 O containing a Cr–Cr quadruple bond .…”

Section: Chromium–chromium Bondsmentioning

confidence: 99%

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Metal–Metal (MM) Bond Distances and Bond Orders in Binuclear Metal Complexes of the First Row Transition Metals Titanium Through Zinc

2018

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This survey of metal–metal (MM) bond distances in binuclear complexes of the first row 3d-block elements reviews experimental and computational research on a wide range of such systems. The metals surveyed are titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, and zinc, representing the only comprehensive presentation of such results to date. Factors impacting MM bond lengths that are discussed here include (a) the formal MM bond order, (b) size of the metal ion present in the bimetallic core (M2) n+, (c) the metal oxidation state, (d) effects of ligand basicity, coordination mode and number, and (e) steric effects of bulky ligands. Correlations between experimental and computational findings are examined wherever possible, often yielding good agreement for MM bond lengths. The formal bond order provides a key basis for assessing experimental and computationally derived MM bond lengths. The effects of change in the metal upon MM bond length ranges in binuclear complexes suggest trends for single, double, triple, and quadruple MM bonds which are related to the available information on metal atomic radii. It emerges that while specific factors for a limited range of complexes are found to have their expected impact in many cases, the assessment of the net effect of these factors is challenging. The combination of experimental and computational results leads us to propose for the first time the ranges and “best” estimates for MM bond distances of all types (Ti–Ti through Zn–Zn, single through quintuple).

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Section: Chromium−chromium Bondsmentioning

confidence: 99%

Section: Chromium–chromium Bondsmentioning

confidence: 99%

Metal–Metal (MM) Bond Distances and Bond Orders in Binuclear Metal Complexes of the First Row Transition Metals Titanium Through Zinc

2018

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“…Recent activity in the field of binuclear transition metal compounds that feature metal–metal multiple bonds, sparked by the already cited synthesis of Cr 2 Ar′ 2 compounds, led us to study the utility of the well-known precursor [Mo 2 (O 2 CMe) 4 ] for the synthesis of Mo–Mo quadruple bonds . With the use of bridging aminopyridinate , and amidinate ,, ligands that possess bulky aryl substituents, we have recently prepared some multiply bonded dimolybdenum species. , Combining the alluring prospects of this area of research − with the enticements of the study of M–C σ bonds, we have investigated a series of methyl complexes of the Mo≣Mo core, stabilized by coordination of the aminopyridinate and amidinate ligands ( 1a – 1c ) represented in Figure . The new compounds comprise some lithium di- and trimethyl dimolybdenum(II) ate complexes ( 3a – 3c and 4c ) that are the subject of this paper.…”

Section: Introductionmentioning

confidence: 99%

Lithium Di- and Trimethyl Dimolybdenum(II) Complexes with Mo–Mo Quadruple Bonds and Bridging Methyl Groups

et al. 2015

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New dimolybdenum complexes of composition [Mo2{μ-Me}2Li(S)}(μ-X)(μ-N^N)2] (3a-3c), where S = THF or Et2O and N^N represents a bidentate aminopyridinate or amidinate ligand that bridges the quadruply bonded molybdenum atoms, were prepared from the reaction of the appropriate [Mo2{μ-O2CMe}2(μ-N^N)2] precursors and LiMe. For complex 3a, X = MeCO2, while in 3b and 3c, X = Me. Solution NMR studies in C6D6 solvent support formulation of the complexes as contact ion pairs with weak agostic Mo-CH3···Li interactions, which were also evidenced by X-ray crystallography in the solid-state structures of the molecules of 3a and 3b. Samples of 3c enriched in (13)C (99%) at the metal-bonded methyl sites were also prepared and investigated by NMR spectroscopy employing C6D6 and THF-d8 solvents. Crystallization of 3c from toluene:tetrahydrofuran mixtures provided single crystals of the solvent separated ion pair complex [Li(THF)4] [Mo2(Me)2(μ-Me){μ-HC(NDipp)2}2] (4c), where Dipp stands for 2,6-iPr2C6H3. A computational analysis of the Mo2(μ-Me)2Li core of complexes 3a and 3b has been developed, which is consistent with a small but non-negligible electron-density sharing between the C and Li atoms of the mainly ionic CH3···Li interactions.

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“…The concept of multiple bonding between metals dates back to the late 1920s with the first structural confirmation in 1964 . Over the last 60 years, multiple bonds between a wide variety of transition metals have been assigned bond orders ranging from single to sextuple. − Nowadays, synthetic chemists seek out new metal–metal bonds for as catalysts, building blocks in metal–organic frameworks, photosensitizers, and molecular conductors. ,− Group 6 metal–metal bonds have been broadly studied for their interesting bonding and unique photophysical properties. , Of these, Cr–Cr multiple bonds are notable because of their rich electronic structure and unique spectroscopic properties. Starting with Cotton’s work in the 1970s, a variety of dichromium complexes have been synthesized; characterization by diffraction has shown that the bond distances range from 1.7 to 2.3 Å. ,− Although in the early days formal bond orders were estimated based on distances, computational work using multiconfigurational methods has established that the electronic structure of these complexes is multiconfigurational due to the small energy splitting between the σ, π, and δ orbitals.…”

Section: Introductionmentioning

confidence: 99%

Computational Spectroscopy of the Cr–Cr Bond in Coordination Complexes

Shiozaki

Vlaisavljevich

2021

Inorg. Chem.

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We report the accurate computational vibrational analysis of the Cr–Cr bond in dichromium complexes using second-order multireference complete active space methods (CASPT2), allowing direct comparison with experimental spectroscopic data both to facilitate interpreting the low-energy region of the spectra and to provide insights into the nature of the bonds themselves. Recent technological development by the authors has realized such computation for the first time. Accurate simulation of the vibrational structure of these compounds has been hampered by their notorious multiconfigurational electronic structure that yields bond distances that do not correlate with bond order. Some measured Cr–Cr vibrational stretching modes, ν(Cr2), have suggested weaker bonding, even for so-called ultrashort Cr–Cr bonds, while others are in line with the bond distance. Here, we optimize geometries and compute ν(Cr2) with CASPT2 for three well-characterized complexes, Cr2(O2CCH3)4(H2O)2, Cr2(mhp)4, and Cr2(dmp)4. We obtain CASPT2 harmonic ν(Cr2) modes in good agreement with experiment at 282 cm–1 for Cr2(mhp)4 and 353 cm–1 for Cr2(dmp)4, compute 50Cr and 54Cr isotope shifts, and demonstrate that the use of the so-called IPEA shift leads to improved Cr–Cr distances. Additionally, normal mode sampling was used to estimate anharmonicity along ν(Cr2), leading to an anharmonic mode of 272 cm–1 for Cr2(mhp)4 and 333 cm–1 for Cr2(dmp)4.

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Group 6 Metal–Metal Bonds

Cited by 10 publications

References 110 publications

Metal–Metal (MM) Bond Distances and Bond Orders in Binuclear Metal Complexes of the First Row Transition Metals Titanium Through Zinc

Metal–Metal (MM) Bond Distances and Bond Orders in Binuclear Metal Complexes of the First Row Transition Metals Titanium Through Zinc

Lithium Di- and Trimethyl Dimolybdenum(II) Complexes with Mo–Mo Quadruple Bonds and Bridging Methyl Groups

Computational Spectroscopy of the Cr–Cr Bond in Coordination Complexes

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