Vibrational Spectrum of Borine Carbonyl

Bethke, George W.; Wilson, Matthew W.

doi:10.1063/1.1743481

Cited by 71 publications

(16 citation statements)

References 15 publications

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“…. On the fully relaxed surface, the obtained C−B and C−O bond distances and the shifts in ν CO are in reasonable agreement with the previous theoretical studies and experimental values 16,[70][71][72]. The non-CT binding forces (frozen interaction and polarization) yield only a weakly bound adduct with the C−B distance, r(CB), being over 3 Å, and r(CB) is only shortened by ∼0.2 Å upon moving from the Frz to Pol surface.…”

supporting

confidence: 90%

Variational Forward–Backward Charge Transfer Analysis Based on Absolutely Localized Molecular Orbitals: Energetics and Molecular Properties

Loipersberger

Mao

Head‐Gordon

2020

J. Chem. Theory Comput.

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To facilitate the understanding of charge transfer (CT) effects in dative complexes, we propose a variational forward-backward (VFB) approach to decompose the overall CT stabilization energy into contributions from forward and backward donation in the framework of energy decomposition analysis based on absolutely localized molecular orbitals (ALMO-EDA). Such a decomposition is achieved by introducing two additional constrained intermediate states in which only one direction of CT is permitted. These two "one-way" CT states are variationally relaxed such that the associated nuclear forces can be readily obtained. This allows for a facile integration into the previously developed adiabatic EDA scheme so that the molecular property changes arising from 1 forward and back donation can be separately assigned. Using ALMO-EDA augmented by this VFB model, we investigate the energetic, geometric, and vibrational features of complexes composed of CO and main group Lewis acids (BH 3 , BeO/BeCO 3), and complexes of the N 2 , CO, and BF isoelectronic series with [Ru(II)(NH 3) 5 ] 2+. We identify that the shift in the stretching frequency of a diatomic π-acidic ligand (XY), such as CO, results from a superposition of the shifts induced by permanent electrostatics and backward CT: permanent electrostatics can cause an either red or blue shift depending on the alignment of the XY dipole in the dative complex, and this effect becomes more pronounced with a more polar XY ligand; the back-donation to the antibonding π orbital of XY always lowers the X−Y bond order and thus red-shifts its stretching frequency, and the strength of this interaction decays rapidly with the intermolecular distance. We also reveal that while σ forward donation contributes significantly to energetic stabilization, it affects the vibrational feature of XY mainly by shortening the intermolecular distance, which enhances both the electrostatic interaction and backward CT but in different rates. The synergistic effect of the forward and backward donations appears to be more significant in the transition metal complexes, where the forward CT plays an essential role in overcoming the strong Pauli repulsion. These findings highlight that the shift in the XY stretching frequency is not a reliable metric for the strength of π back-donation. Overall, the VFB-augmented EDA scheme that we propose and apply in this work provides a useful tool to characterize the role played by each physical component that all together lead to the frequency shift observed.

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supporting

confidence: 90%

Variational Forward–Backward Charge Transfer Analysis Based on Absolutely Localized Molecular Orbitals: Energetics and Molecular Properties

Loipersberger

Mao

Head‐Gordon

2020

J. Chem. Theory Comput.

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“…[2][3][4][5][6][7] In general, the carbonylation of free [B] À H-containing boranes seems not to lead to the formation of the respective borane carbaldehydes because of the endothermicity of this reaction. [2][3][4][5][6][7] We recently prepared a small series of annulated formylborane-like compounds [8] by the treatment of CO with HB(C 6 F 5 ) 2 at frustrated Lewis pair (FLP) templates. [9][10][11][12] We have now carried out reactions of these FLP-stabilized formylborane derivatives with some remarkable outcomes.…”

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confidence: 99%

Formylborane Formation with Frustrated Lewis Pair Templates

et al. 2013

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Boranes R2 BH react with carbon monoxide by forming the respective borane carbonyl compounds R2 BH(CO). The formation of (C6 F5 )2 BH(CO) derived from the Piers borane, HB(C6 F5 )2 , is a typical example. Subsequent CO-hydroboration does not take place, since the formation of the formylborane is usually endothermic. However, an "η(2) -formylborane" was formed by CO-hydroboration with the Piers borane at vicinal phosphane/borane frustrated Lewis pair (FLP) templates. Subsequent treatment with pyridine liberated the intact formylborane from the FLP framework, and (pyridine)(C6 F5 )2 BCHO was then isolated as a stable compound. This product underwent typical reactions of carbonyl compounds, such as Wittig olefination.

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“…Figure 1C shows IR spectra for two different reactiont imes from which the contributions of CO, H 2 O, and CO 2 have been subtracted in order to better visualize these other IR bands.T hese vibrational signals can be clearly identified as those of H 3 BCO by comparison with literature spectra ( Figure 1B). [21] The vibrational band of H 3 BCO around2 165 cm À1 can be assigned to the rotationally resolved carbonyl stretching vibration, and the band between 2400 and 2525 cm À1 to BH 3 stretching vibrations.S ince H 3 BCO decays after its generation and CO is an end product, borane is formed during the reactionand may further react to form diborane. Thus, borane and diborane may contribute to the IR spectra of the gas phase.…”

Section: Qualitative Analysis Of Corm-a1 Decaymentioning

confidence: 99%

“…The CO 2 concentrationint he IR cuvettea nd Figure 1. A) Baseline-corrected gas-phase IR spectrarecorded above adecaying CORM-A1 solution at different reaction times and for two different pH values.B)Literature gas-phase IR spectraofH 3 BCO [21] and B 2 H 6 . [22] C) IR spectraa fter subtracting the contributions of CO, CO 2 ,a nd H 2 Ogas.…”

Section: Qualitative Analysis Of Corm-a1 Decaymentioning

confidence: 99%

Elucidation of the CO‐Release Kinetics of CORM‐A1 by Means of Vibrational Spectroscopy

et al. 2016

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CO-releasing molecules (CORMs) are developed for investigations of the interaction between the signaling molecule carbon monoxide (CO) and cells or tissue. Prior to their application these molecules must be fully characterized with respect to their CO-release mechanism. One widely used CORM for biological application is sodium boranocarbonate (CORM-A1), which shows pH-dependent CO liberation. The complete reaction mechanism of CORM-A1 is not fully understood yet. Therefore, in this contribution time-resolved gas-phase IR spectroscopy is used to monitor the headspace above decaying CORM-A1 solutions at four different pH values (5.8 to 7.4). Borane carbonyl is found as an intermediate in the gas phase, which is formed during CORM degradation and further decays to CO. Concentration profiles of a pseudoconsecutive first-order reaction are successfully fitted to specific band areas of the measured gas-phase spectra, and the rate constants are obtained. The production of borane carbonyl is strongly pH dependent (half-lives between 5 and 106 min), whereas the decay of borane carbonyl in the gas phase is nearly constant with a half-life of about 33 min. The ratio of liberated CO molecules per CORM-A1 is determined to be 0.91±0.09, and boric acid is identified as further end product.

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Vibrational Spectrum of Borine Carbonyl

Cited by 71 publications

References 15 publications

Variational Forward–Backward Charge Transfer Analysis Based on Absolutely Localized Molecular Orbitals: Energetics and Molecular Properties

Variational Forward–Backward Charge Transfer Analysis Based on Absolutely Localized Molecular Orbitals: Energetics and Molecular Properties

Formylborane Formation with Frustrated Lewis Pair Templates

Elucidation of the CO‐Release Kinetics of CORM‐A1 by Means of Vibrational Spectroscopy

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