Steric and electronic factors influencing the structures of bridged (.beta.-type) M2Cl4(LL)2 (M = Mo, Re) compounds: a refined correlation of bond length with torsion angle

Campbell, Fred L.; Cotton, F. Albert; Powell, Gregory L.

doi:10.1021/ic00219a037

Cited by 36 publications

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“…It is likely that, because of constraints in the solid state (often referred to as packing forces), variations of up to 0.02 Å cannot be taken too seriously. On the other hand, the existence of an approximate dependence of MoMo distance on internal twist angle was established some time ago …”

Section: Resultsmentioning

confidence: 99%

The Lengths of Molybdenum to Molybdenum Quadruple Bonds: Correlations, Explanations, and Corrections

et al. 2002

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A systematic search of the Cambridge Crystallographic Database has yielded structures of 467 molecules containing, or reported to contain, a molybdenum to molybdenum quadruple bond, Mo[quadruple bond]Mo. We have arranged these data as a histogram, in order to determine the "normal" range of Mo[quadruple bond]Mo lengths, 2.06-2.17 A, as well as to examine molecules in which the Mo[quadruple bond]Mo length deviates from the norm. We discuss 24 molecules with exceptionally long Mo[quadruple bond]Mo lengths. Another molecule, Mo(2)(pyNC(O)CH(3))(4), was previously reported to have an unusually short Mo[quadruple bond]Mo bond. However, the structure is highly disordered (probably twinned); thus we have prepared and determined the structure of an analogous molecule, Mo(2)(pyNC(O)CH(2)CH(3))(4), which displays a completely normal Mo[quadruple bond]Mo bond length of over 2.08 A.

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Section: Resultsmentioning

confidence: 99%

The Lengths of Molybdenum to Molybdenum Quadruple Bonds: Correlations, Explanations, and Corrections

et al. 2002

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“…Atomic positional parameters and selected bond lengths and angles for 2 are presented in Tables V-VII, respectively. The coordination geometry about each Rh atom is planar if one considers the midpoints of each olefinic bond Cll-Rhl-CCl 1 165.8 (6) in the cyclooctadiene ligands and the P and Cl atoms.14 Molecules of 2 are therefore similar to those of 1 in the fact that they contain planar Rh(I) atoms bridged by two groups. However, there are two key structural differences between them.…”

Section: Resultsmentioning

confidence: 99%

Rhodium-rhodium bonds of order 0, 1, and 2 in dinuclear rhodium(I) phosphido and arsenido complexes: x-ray crystal structures of [Rh(CO)(tert-Bu2PH)]2(.mu.-tert-Bu2P)(.mu.-H) (Rh-Rh), [Rh(COD)]2(.mu.-tert-Bu2P)(.mu.-Cl) (COD = 1,5-cyclooctadiene), and [Rh(.mu.-tert-Bu2As)(CO)2]2

Arif¹,

Jones²,

Seeberger³

et al. 1986

Inorg. Chem.

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“…Compounds of the type -Mo 2 X 4 (PP) 2 , where X = Cl or Br and PP is a diphosphine, are a series that can be used to test this proposal. 8,9 The results are shown in Fig. 16.3.…”

Section: Internal Rotationmentioning

confidence: 97%

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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Steric and electronic factors influencing the structures of bridged (.beta.-type) M2Cl4(LL)2 (M = Mo, Re) compounds: a refined correlation of bond length with torsion angle

Cited by 36 publications

References 0 publications

The Lengths of Molybdenum to Molybdenum Quadruple Bonds: Correlations, Explanations, and Corrections

The Lengths of Molybdenum to Molybdenum Quadruple Bonds: Correlations, Explanations, and Corrections

Rhodium-rhodium bonds of order 0, 1, and 2 in dinuclear rhodium(I) phosphido and arsenido complexes: x-ray crystal structures of [Rh(CO)(tert-Bu2PH)]2(.mu.-tert-Bu2P)(.mu.-H) (Rh-Rh), [Rh(COD)]2(.mu.-tert-Bu2P)(.mu.-Cl) (COD = 1,5-cyclooctadiene), and [Rh(.mu.-tert-Bu2As)(CO)2]2

Physical, Spectroscopic and Theoretical Results

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