Insensitivity of the molybdenum-to-molybdenum quadruple bond in the dimolybdenum tetracarboxylates to axial coordination and changes in inductive effects

Cotton, F. Albert; Extine, M. W.; Gage, Larry D.

doi:10.1021/ic50179a033

Cited by 82 publications

(48 citation statements)

References 18 publications

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“…This last study will provide a very useful comparison with the present work, performed on a complex which could be expected to be very similar to Cr2(CH3CO2)4.2H20 (same ligand, same electronic environment of the metal, same type of bonding expected), but which displays surprising differences that were never completely rationalized: difference of sensitivity of the metal-metal bond length to physical or chemical perturbations (Cotton, Extine & Gage, 1978;Cotton, Extine & Rice, 1978), difference in the strength of the quadruple bond and in the weight of the © 1981 International Union of Crystallography antibonding orbitals in the expansion of the wavefunction (B~nard, 1978a, 1979b). The study of the charge densities in the region of the Mo-Mo bond of the title compound may provide some additional information on these pending problems.…”

Section: Introductionmentioning

confidence: 78%

“…This could be correlated with the difference in sensitivity to axial coordination of Cr and Mo tetracarboxylates, extensively documented by Cotton et al These authors have demonstrated that tetracarboxylates of Cr are extremely sensitive to axial coordination. Most of them either are associated with axial ligands or display strong intermolecular interactions in axial positions (Cotton, Extine & Gage, 1978). On the other hand, tetracarboxylates of Mo are almost completely insensitive to axial coordination (Cotton, Extine & Rice, 1978).…”

Section: Resultsmentioning

confidence: 99%

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Electron-density distribution in crystals of tetra-μ-acetato-dimolybdenum(Mo–Mo)

Hino¹,

Saito²,

Bénard³

1981

Acta Crystallogr Sect B

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The electron-density distribution in crystals of Moz(CH3COz) 4 has been determined by single-crystal X-ray diffractometry at 293 K [crystal data: Moz(CzH3Oz)4, space group PI, a = 8.4084 (6) In general terms, a section of the deformation-density map perpendicular to and through the midpoint of the Mo--Mo bond shows diffuse residual density surrounding the bond in the form of a torus, the maximum being 0.2 (1)e/~, -3. On both sides of the Mo-Mo bond, there are disc-shaped peaks of 0.3 (1) e/~-3 each 0.42 A, from the Mo atom. The valenceelectron populations of the atoms were refined and the net charges of Mo, O and C atoms were estimated to be +1.16 (8), -0-29 (4) and +0.00 (4) respectively. These and other features of the deformation density around the Mo atoms can be reasonably accounted for in terms of a classical picture of a quadruple Mo-Mo bond and also agree with the result of ab initio CI (configuration interaction) calculations for analogous Moz(HCOz)4.

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Section: Introductionmentioning

confidence: 78%

Section: Resultsmentioning

confidence: 99%

Electron-density distribution in crystals of tetra-μ-acetato-dimolybdenum(Mo–Mo)

Hino¹,

Saito²,

Bénard³

1981

Acta Crystallogr Sect B

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“…Consider, for example, the marked contrast between dichromium and dimolybdenum species. For the molybdenum compounds, 17,18 even when axial ligands are attached, they are very weakly bound and the Mo-Mo distance is lengthened by only a few hundredths of an Angstrom.…”

Section: Axial Ligandsmentioning

confidence: 99%

Physical, Spectroscopic and Theoretical Results

Cotton

2005

Multiple Bonds Between Metal Atoms

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Structural Correlations Bond orders and bond lengthsThroughout the preceding chapters of this book we have reported and in some cases discussed the lengths of the multiple bonds between metal atoms. We have reported in tabular form most of the M-M distances that have been determined crystallographically. It is now time to make some general comments on these distances in relation to our understanding of the M-M bonds.It is a general qualitative rule in chemistry that bond lengths and bond orders are inversely related. In some limited areas, particularly with the fi rst-row elements carbon, nitrogen, and oxygen, quantitative relationships expressing bond length as a single-valued function of bond order are well known. However, these quantitative relationships are based heavily on faith, as well as fact. Bond lengths are facts; bond orders are not. In the process of inferring a bond order from a bond length one is often getting out no more than what was put in to begin with.We shall not further digress into a discussion of the philosophical ambiguities of these quantitative bond order-bond length correlations because they have proven to be useful, within their own sphere of application. However, there is no a priori reason to expect that similar procedures will (or will not!) work in the very different realm of metal-to-metal bonds. Experience is the only test, and experience thus far has shown that M-M bonds cannot usefully be treated in such a way.In the realm of M-M bonds it is best to invoke only a qualitative inverse relationship between bond order and bond length and to defi ne bond order only in a qualitative or ordinal way. In this book we have used the term M-M bond order only to indicate how many electron pairs are believed, on the basis of essentially qualitative considerations, to play a signifi cant part in holding the pair of metal atoms together. We condemn as foolish and hopeless any effort to associate a unique, precise, quantitative bond order with each and every M-M internuclear distance.In principle, M-M bond lengths, like others, should be amenable to treatment by the method of molecular mechanics, and some efforts [1][2][3][4] (hampered by a dearth of necessary experimental data) to do this have been reported. In general the results are encouraging and can account for

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“…The structure is shown in Fig. 1 molybdenum oxides, while even stronger Mo--Mo bondings such as the triple bond (Chisholm, Cotton, Extine & Murillo, 1978) and the quadruple bond (Cotton, Extine & Gage, 1978) have been known in some non-oxide compounds. The Mo--Mo bonding concerned forms the triangular atom groups of Mo3013 in the MoO 6 layer (Fig.…”

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confidence: 99%

Structure of kamiokite

Kanazawa¹,

Sasaki²

1986

Acta Crystallogr C

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Fig. 4 shows the DTA curve recorded between 240 and 130K. A small endothermic peak occurs at 168 (2)K. The peak is completely reversible with a slight hysteresis of about 5 K. Because the base line is not completely linear an exact value for the change in free enthalpy and consequently in the entropy should not be estimated. The peak in the DTA curve lies in the same temperature range as observed in the magnetic susceptibility curve (Fig. 3).The structure of the title compound shows an unusual connection scheme with edge-and face-sharing octahedra. This leads to distorted V(S,Se) 6 octahedra with short metal-metal bonds in the structure. The partial itinerant character of this compound is supported by the magnetic measurements. The discontinuity in the magnetic-susceptibility curve and the endothermic peak in the DTA curve are a clear indication for a phase transition at around 170K. Further investigations are in progress to clarify the nature of this phase transition.

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Insensitivity of the molybdenum-to-molybdenum quadruple bond in the dimolybdenum tetracarboxylates to axial coordination and changes in inductive effects

Cited by 82 publications

References 18 publications

Electron-density distribution in crystals of tetra-μ-acetato-dimolybdenum(Mo–Mo)

Electron-density distribution in crystals of tetra-μ-acetato-dimolybdenum(Mo–Mo)

Physical, Spectroscopic and Theoretical Results

Structure of kamiokite

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