Turning a Transition State into a Minimum—The Nature of the Bonding in Diplumbylene Compounds RPbPbR (R=H, Ar)

Chen, Yu; Hartmann, Michael; Diedenhofen, Michael; Frenking, Gernot

doi:10.1002/1521-3773(20010601)40:11<2051::aid-anie2051>3.0.co;2-d

Cited by 59 publications

(79 citation statements)

References 28 publications

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“…Although the size of the bulky terphenyl ligands precluded frequency analysis of the DFT-optimized structure of [Ar'CrCrAr'], we believe that the sterically bulky terphenyl ligands can stabilize the trans-bent geometry, and turn a transition point into a minimum in a fashion analogous to that observed in [Ar*PbPbAr*] (Ar* = 2,6-Ph 2 C 6 H 3 ). [18] In summary, the number of singly occupied orbitals available for CrÀCr bonding determines uniquely the formal bond order: six in the chromium dimer, five in the present Cr I compound, and four in Cr II compounds such as [Cr 2 (O 2 CMe) 4 ] (CrÀCr = 1.97 , [19] calculated bond length = 1.94 ). [20] Experimental Section…”

mentioning

confidence: 90%

A Quantum Chemical Study of the Quintuple Bond between Two Chromium Centers in [PhCrCrPh]: trans‐Bent versus Linear Geometry

Brynda

Gagliardi

Widmark³

et al. 2006

Angew Chem Int Ed

318

180

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The recent report of a stable, crystalline compound with a quintuply bonded chromium-chromium core [1] may reopen the debate on the nature of the multiple bonds between transition metals [2] that was initiated by the discovery of a stable, quadruple bond by Cotton et al. in 1964. [3] Although a recent study of a quintuple bond in the uranium dimer [4] U 2 provided strong support for the existence of such bonds, the isolation of the stable [Ar'CrCrAr'] species (Ar' = 2,6-(2,6-iPr 2 -C 6 H 3 ) 2 -C 6 H 3 ), which has a planar, trans-bent rather than a linear C ipso CrÀCrC ipso core and weak temperature-independent paramagnetism, has raised new questions about multiple bonding. Such a trans-bent structure was recently predicted for the simple [HCrCrH] dimer by Weinhold and Landis on the basis of DFT calculations and a natural-bond analysis. [5] The simplest molecule containing a CrÀCr bond is Cr 2 . Its experimental bond length, obtained from laser-induced fluorescence spectroscopy, is 1.679 , and this extremely short CrÀCr bond has a formal bond order of six, although its significance was questioned [6] because of its low dissociation energy (1.53 AE 0.06 eV). According to different theoretical studies, the description of the CrCr interaction in Cr 2 ranges from a sextuple bond, [7][8][9][10] through a single bond, [11] to a complete absence of bonding between the chromium atoms. [6] It is now well established that a proper description of the bonding in this species requires a multiconfigurational treatment. A description of the bonding in Cr 2 that is in full agreement with the experimental data was obtained in a recent study.[12] Formally, a sextuple bond is formed, but the effective bond order is only about four because of mixing of excited, less-bonding states into the ground state. Similar behavior was also observed for [Re 2 Cl 8 ] 2À , in which a formal quadruple bond was found to have a bond order of only about three for similar reasons. [13,14] The bonding scheme in the [Ar'CrCrAr'] complex resembles that found in the Cr 2 dimer: The interaction of two Cr I centers with d 5 electron configurations leads to five, rather than six, metal-metal bonding molecular orbitals, along with their antibonding counterparts. The questions that arise are: which electronic configurations dominate the ground-state wave function, and how important is the contribution of the bonding (s g ) 2 (p u ) 4 (d g ) 4 configuration? The main difference between the bonding in Cr 2 and [Ar'CrCrAr'] lies in the fact that two additional metal-ligand orbital combinations involving the participation of mainly 4 s orbitals in the metalcarbon(ligand) bond are present in [Ar'CrCrAr']. Despite this apparent similarity, the situation in the real complex is more complicated because of the size of the ligands, and also because of the presence of the "indirect" metal-ligand interactions. Because of the presence of the flanking aryl groups in the vicinity of the chromium centers, a weak, but non-negligible interaction occurs.[1] This interaction, ...

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mentioning

confidence: 90%

A Quantum Chemical Study of the Quintuple Bond between Two Chromium Centers in [PhCrCrPh]: trans‐Bent versus Linear Geometry

Brynda

Gagliardi

Widmark³

et al. 2006

Angew Chem Int Ed

318

180

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“…We note in passing that the effects of phenyl substitution to the lead system (PhPbPbPh) have been studied previously. 13 There, both the steric and electronic effects of 2,6-Ph 2 C 6 H 3 substituents were seen to play a role in stabilizing and making the singly bonded lead isomer a true energy minimum as in experiments.…”

Section: Effect Of Electron-withdrawal and Electron-donationmentioning

confidence: 93%

“…Electronic structure calculations that predate the experiments support this possibility. 11- 13 Bulky substituents can protect a reactive core, and provide electronic stabilization as well, but may impose steric requirements. They can also probe what happens in the absence of such substituents.…”

Section: Introductionmentioning

confidence: 99%

Dalton Discussion 11: The renaissance of main group chemistry

Arnold¹

2008

Dalton Trans.

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Image reproduced with permission of Manfred ScheerPapers published in this issue include:The coordination chemistry of group 15 element ligand complexes-a developing area Manfred Scheer, Dalton Trans., 2008 DOI: 10.1039 Recent experimental and theoretical evidence has shown that distannynes, RSnSnR, can adopt either a singly bonded or a multiply bonded structure. Within calculations on small models, such as MeSnSnMe, apparently dramatic differences in conformational preference have been reported. We show that these differences arise due to the treatment of spin-polarization in density functional theory (DFT), and review stability analysis; a diagnostic for the need to include spin-polarization. The low-energy singly bonded structure can only be reached when spin-polarization is allowed. Additional DFT calculations on PhSnSnPh show that the singly bonded structure is the global minimum, leading to a flat torsional potential. The role of electronic effects is further probed by changing the donor-acceptor properties of R. Implications for the structural preference of experimentally synthesized species are discussed.

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“… Allerdings sprechen die Strukturdaten dafür, dass die Bindungsordnung in den Molekülen 3 und 4 etwa 2 beträgt. Die entsprechende Diblei‐Verbindung 5 ist wegen der langen Pb‐Pb‐Bindung, die deutlich länger ist als die einer Pb‐Pb‐Einfachbindung, sowie der trans ‐Abwinkelung der Substituenten von 94.26° eher als ein Diplumbylen mit einer Pb‐Pb‐Einfachbindung und einem freien Elektronenpaar an jedem der beiden Bleiatome zu betrachten 9. Die experimentellen Beobachtungen werden gestützt durch quantenchemische Rechnungen, die eindeutig die Diplumbylen‐Form 5 als Energieminimum belegen.…”

Section: Methodsunclassified

Moleküle mit einer echten Si‐Si‐Dreifachbindung und ein stabiles Derivat von [SiH]⁺

Weidenbruch

2005

Angewandte Chemie

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Lange Zeit galt in der Molekülchemie der Hauptgruppenelemente die Mehrfachbindungsregel, die oft vereinfacht als Doppelbindungsregel bezeichnet wurde. Gemäß dieser Regel sollten die Elemente der 1. Achterperiode, nicht jedoch die der höheren Perioden zu Mehrfachbindungen befähigt sein. Der Ursprung der Regel liegt im Dunkeln, vermutlich liegen Arbeiten von Pitzer [1] und von Mulliken [2] zugrunde, die vor mehr als 50 Jahren der Frage nachgingen, warum beispielsweise N 2 eine außerordentlich hohe Bindungsdissoziationsenergie hat, das gruppenhomologe P 2 -Molekül hingegen nur als Hochtemperaturspezies existiert und beim Abkühlen das P 4 -Molekül mit P-P-Einfachbindungen ergibt. Als ein Grund für die sehr unterschiedlichen Stabilitäten der Dreifachbindungen in N 2 und P 2 wurden die repulsiven Kräfte zwischen vollbesetzten inneren Elektronenschalen angeführt. Während bei N 2 nur die abstoßenden Kräfte der jeweils mit zwei Elektronen besetzten ersten Schale wirksam werden, kommen beim P 2 -Molekül zusätzlich die jeweils acht Elektronen der zweiten Schale hinzu, die die P-P-Dreifachbindung bei Raumtemperatur instabil werden lassen.Aufgeweicht wurde diese fast zum Dogma erhobene Regel unter anderem durch die Synthese und strukturelle Charakterisierung des Distannens 1,

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Turning a Transition State into a Minimum—The Nature of the Bonding in Diplumbylene Compounds RPbPbR (R=H, Ar)

Cited by 59 publications

References 28 publications

A Quantum Chemical Study of the Quintuple Bond between Two Chromium Centers in [PhCrCrPh]: trans‐Bent versus Linear Geometry

A Quantum Chemical Study of the Quintuple Bond between Two Chromium Centers in [PhCrCrPh]: trans‐Bent versus Linear Geometry

Dalton Discussion 11: The renaissance of main group chemistry

Moleküle mit einer echten Si‐Si‐Dreifachbindung und ein stabiles Derivat von [SiH]⁺

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Turning a Transition State into a Minimum—The Nature of the Bonding in Diplumbylene Compounds RPbPbR (R=H, Ar)

Cited by 59 publications

References 28 publications

A Quantum Chemical Study of the Quintuple Bond between Two Chromium Centers in [PhCrCrPh]: trans‐Bent versus Linear Geometry

A Quantum Chemical Study of the Quintuple Bond between Two Chromium Centers in [PhCrCrPh]: trans‐Bent versus Linear Geometry

Dalton Discussion 11: The renaissance of main group chemistry

Moleküle mit einer echten Si‐Si‐Dreifachbindung und ein stabiles Derivat von [SiH]+

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Moleküle mit einer echten Si‐Si‐Dreifachbindung und ein stabiles Derivat von [SiH]⁺