Two Photon Excitation Spectrum of a Twisted Quadruple Bond Metal−Metal Complex

Engebretson, Daniel; Graj, Evan M.; Leroi, G. E.; Nocera, Daniel G.

doi:10.1021/ja983295d

Cited by 25 publications

(19 citation statements)

References 19 publications

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“…However, the 1 A 1g 1 A 1g * transition is allowed in the two-photon absorption spectrum. 193,194 Here, two electrons are promoted to the * level by the simultaneous absorption of two photons whose energies sum to the energy required. Because we can estimate the 1 A 2u, it follows that the two exciting photons must be in the near-infrared frequency range.…”

Section: Details Of the Manifold Of Statesmentioning

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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Section: Details Of the Manifold Of Statesmentioning

confidence: 99%

Physical, Spectroscopic and Theoretical Results

Cotton

2005

Multiple Bonds Between Metal Atoms

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“…[35] The complex d manifold of a (d ± d) 8 metal ± metal bond ( Figure 4) has been remarkably well studied in the Mo 2 4 core. [12,75,76] In contrast, only the 1 (d 2 ) ± 1 (dd*) gap (determined from UV/Vis spectra of [MoWCl 4 (PR 3 ) 4 ] compounds, [35] Table 3, entry 14) and the low limit on the 1 (d 2 ) ± 1 (d xy d xy ) energy difference (d barrier [77,78] ) are known for a heteronuclear bond. The d barrier and the (partially off- [64] [e] For Mo 2 6 , the average of four compounds; the W 2 congener has not been studied crystallographically; the value is the average W ± W separation in two [W 2 (m-Cl) 3 Cl 6 ] 3À ions, [65,66] which is likely to be longer than the WÀW bond in [W 2 (m-Cl) 2 (m-H)Cl 6 ] 3À based on comparison of the corresponding Mo 2 derivatives.…”

Section: Physicochemical Propertiesmentioning

confidence: 99%

“…[35,36] The ionic ( 1 (d* 2 ), 1 (dd*)) states of the Mo 2 4 core have been studied by two photon spectroscopy (Figure 4). [76] Induced fluorescence from the 1 (dd*) state is observed upon twophoton 1 (d 2 3d* 2 ) excitation followed by rapid nonradiative decay to the 1 (dd*) state. The 1 (dd*) ± 1 (d* 2 ) gap (4800 cm À1 ), estimated from the difference in the 1 (d 2 3dd*) and 1 (d 2 3d* 2 ) transition maxima, is comparable to the 1 (d 2 ) ± 3 (dd*) gap (4840 cm À1 ) measured by VT 31 P NMR spectroscopy.…”

Section: Physicochemical Propertiesmentioning

confidence: 99%

Heterodinuclear Transition-Metal Complexes with Multiple Metal–Metal Bonds

Collman¹,

Boulatov²

2002

Angew. Chem. Int. Ed.

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Interactions between a pair of transition-metals can range from weak antiferromagnetic coupling to bonds of the highest multiplicity known in chemistry, for example, quadruple in isolatable compounds. Tremendous effort has been invested in studying homodinuclear transition-metal-metal bonds. In contrast, relatively little attention has been devoted to heterodinuclear analogues, as it is substantially more challenging to prepare and handle such entities. Yet, in this largely unexplored area of transition-metal chemistry, novel chemical interactions with unprecedented reactivities are likely to be found. Heterodinuclear analogues of diatomic transition-metal dimers being yet inaccessible, dinuclear complexes with Werner-type ligands provide examples of high-multiplicity bonds between different d elements in their least-perturbed form. Such compounds provide an opportunity to probe fundamental issues of chemical bonding between transition-metals, by revealing how and to what extent such bonds are affected by differences in the two metals. Complexes wherein electronically unsaturated heterodinuclear cores are stabilized by pi-acidic ligands (such as CO) hold the potential of new chemical reactions (including catalytic) that capitalize on the synergetic effect of two transition-metal centers.

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“…Die komplexe Mannigfaltigkeit der δ‐Orbitale einer (d‐d) 8 ‐Übergangsmetall‐Übergangsmetall‐Bindung (Abbildung 4) ist für den Mo 2 4+ ‐Rumpf bemerkenswert gut erforscht 12, 75, 76. Für den heteronuclearen Fall ist lediglich die Größe einer 1 (δ 2 )‐ 1 (δδ*)‐Lücke bekannt (aus UV/Vis‐Spektren von [MoWCl 4 (PR 3 ) 4 ]‐Verbindungen,35 Tabelle 3, Eintrag 14) sowie die untere Grenze der 1 (δ 2 )‐ 1 (d xy d xy )‐Energiedifferenz (δ‐Barriere) 77, 78.…”

Section: Heterodinucleare Komplexe Ohne π‐Acide Ligandenunclassified

Heterodinucleare Übergangsmetallkomplexe mit Metall-Metall-Mehrfachbindungen

Collman

Boulatov

2002

Angew. Chem.

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Die Bandbreite der möglichen Wechselwirkungen zwischen zwei Übergangsmetallen erstreckt sich von schwachen antiferromagnetischen Kopplungen bis hin zu Vierfachbindungen, den Bindungen höchster bekannter Multiplizität. Während homonucleare Metall‐Metall‐Bindungen von Übergangsmetallen intensiv untersucht wurden, sind die heteronuclearen Analoga bislang weitgehend unerforscht, eine Tatsache, die sicher auf die schwierige Synthese und Handhabung solcher Verbindungen zurückzuführen ist. In diesem noch weitgehend unerschlossenen Gebiet der Übergangsmetallchemie finden sich neue chemische Wechselwirkungen mit ungewöhnlichen Reaktivitäten. Da Heteroanaloga zweiatomiger Übergangsmetalldimere bislang nicht zugänglich sind, greift man auf zweikernige Komplexe mit Liganden vom Werner‐Typ als weitgehend ungestörte Prototypen für Metallrümpfe mit Bindungen hoher Multiplizität zwischen unterschiedlichen d‐Elementen zurück. Solche Verbindungen liefern die Möglichkeit, die Grundlagen der chemischen Bindung zwischen Übergangsmetallen zu untersuchen, indem man betrachtet, wie und zu welchem Ausmaß solche Bindungen von den Unterschieden zwischen den beiden Metallen beeinflusst werden. Komplexe, in denen elektronisch ungesättigte Rümpfe durch π‐acide Liganden wie CO stabilisiert werden, können neue chemische Reaktionen (auch katalytische) eingehen, die den synergetischen Effekt zweier Übergangsmetallzentren nutzen.

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Two Photon Excitation Spectrum of a Twisted Quadruple Bond Metal−Metal Complex

Cited by 25 publications

References 19 publications

Physical, Spectroscopic and Theoretical Results

Physical, Spectroscopic and Theoretical Results

Heterodinuclear Transition-Metal Complexes with Multiple Metal–Metal Bonds

Heterodinucleare Übergangsmetallkomplexe mit Metall-Metall-Mehrfachbindungen

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