H2BH3 as an intermediate in tetrahydridoborate hydrolysis

Kreevoy, Maurice M.; Hutchins, J. E. C.

doi:10.1021/ja00773a020

Cited by 103 publications

(80 citation statements)

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“…This effect has less relevance for analytical CHG than that discussed for strongly acidic conditions, but it has a remarkable relevance for the clarification of the mechanism of hydrolysis of [BH 4 ] -. The existence of the BH 3 (H 2 ) intermediate, proposed by several workers, was supported by indirect experimental evidence by Kreevoy and Hutchins [65]. They found that kinetic models based on general acid catalysis failed to correlate the measured rate of hydrolysis of [BH 4 ] -under strongly basic solutions (0.1 < [NaOH] < 2.3 mol L -1 ).…”

Section: Deviations From Second-order Kinetics Under Strongly Alkalinmentioning

confidence: 81%

“…9 have also been reported under strongly alkaline conditions [65]. This effect has less relevance for analytical CHG than that discussed for strongly acidic conditions, but it has a remarkable relevance for the clarification of the mechanism of hydrolysis of [BH 4 ] -.…”

Section: Deviations From Second-order Kinetics Under Strongly Alkalinmentioning

confidence: 87%

“…Deviations from the kinetic law described by eq. 9 take place under both strongly acidic [17,37] and strongly alkaline conditions [65]. Equation 9 reduces to eq.…”

Section: Acid-catalyzed Hydrolysis Of Borane Complexesmentioning

confidence: 99%

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Mechanisms of chemical generation of volatile hydrides for trace element determination (IUPAC Technical Report)

D’Ulivo

Dědina

Mester

et al. 2011

Pure and Applied Chemistry

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Aqueous-phase chemical generation of volatile hydrides (CHG) by derivatization with borane complexes is one of the most powerful and widely employed methods for determination and speciation analysis of trace and ultratrace elements (viz. Ge, Sn, Pb, As, Sb, Bi, Se, Te, Hg, Cd, and, more recently, several transition and noble metals) when coupled with atomic and mass spectrometric detection techniques. Analytical CHG is still dominated by erroneous concepts, which have been disseminated and consolidated within the analytical scientific community over the course of many years. The overall approach to CHG has thus remained completely empirical, which hinders possibilities for further development. This report is focused on the rationalization and clarification of fundamental aspects related to CHG: (i) mechanism of hydrolysis of borane complexes; (ii) mechanism of hydrogen transfer from the borane complex to the analytical substrate; (iii) mechanisms through which the different chemical reaction conditions control the CHG process; and (iv) mechanism of action of chemical additives and foreign species. Enhanced comprehension of these different mechanisms and their mutual influence can be achieved in light of the present state of knowledge. This provides the tools to explain the reactivity of a CHG system and contributes to the clarification of several controversial aspects and the elimination of erroneous concepts in CHG.

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Section: Deviations From Second-order Kinetics Under Strongly Alkalinmentioning

confidence: 81%

Section: Deviations From Second-order Kinetics Under Strongly Alkalinmentioning

confidence: 87%

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Mechanisms of chemical generation of volatile hydrides for trace element determination (IUPAC Technical Report)

D’Ulivo

Dědina

Mester

et al. 2011

Pure and Applied Chemistry

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“…. When BH4D is produced by reaction (4) .of BE4 with D30 below pH 12, about 95% of the hydrogen loss occurs as ED. This interesting observation implies either (a) that the D+ becomes equivalent to only one resident H atom, or (b) that the D remains unique and is lost when BH4D decomposes (A candidate for this second possibility is that D remains at the apex of tetragonal pyramidal BH4D).…”

Section: Be3mentioning

confidence: 99%

Effects of Orbital Vacancies in Boron Compounds

Lipscomb¹

1977

Boron Chemistry–3

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-Addition of H2to BH3 yields BE5, which is shown to be of Cq symmetry. Rearrangement mechanisms and hydrogen loss have been examined.Intermediates such as B3H7 and B4H8 have been predicted to have vacant orbital structures in which the stability gained by filling that orbital is balanced by strain in converting a terminal hydrogen to a bridge hydrogen. I. VACANT ORBITALS IN TRANSIENT SPECIES BEA prototype of the BE units in polyhedral itolecules, the diatomic BE molecule has all of its electrons paired (-E+). Nevertheless, it is paramagnetic. The magnetic susceptibility, x = 18.7 ppm (1), is the temperature-independent type, and arises largely from excitations from the filled 3a level. This unusual property is a forewarning that magnetic shielding in the boron hydrides and carboranes have large, sometimes dominating, contributions from the paramagnetic term. The chemistry of this unstable species has not been studied, but would probably be very interesting. BE3iiwn as a reaction intermediate in diborane pyrolysis and other reactions, this molecule has a vacant orbital which cannot be filled by a molecular distortion. Adducts to Lewis bases have stabilities correlating with bond distance (2). It has been isolated in a matrix (3) atlow temperatures, from pyrolysis of BH3CO. Theoretical studies are consistent with the planar D3h structure. We now turn to a very weak adduct between BH3 and H2. . When BH4D is produced by reaction (4) .of BE4 with D30 below pH 12, about 95% of the hydrogen loss occurs as ED. This interesting observation implies either (a) that the D+ becomes equivalent to only one resident H atom, or (b) that the D remains unique and is lost when BH4D decomposes (A candidate for this second possibility is that D remains at the apex of tetragonal 701

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“…In basic D2O, the unreacted BH4 − turned into, first BH3D − , then BH2D2 − , etc. 2 Pitzer et al have reported that B2D6 was obtained by shaking B2H6 with D2 at room temperature. 3 The possible mechanism is as following.…”

Section: Introductionmentioning

confidence: 99%

The Potential Energy Surface of BH₅and the Rate of the Hydrogen Scrambling

2003

Bulletin of the Korean Chemical Society

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The BH 5 molecule, which is suggested as an intermediate of the acidolysis of BH 4 − , contains a weak twoelectron-three-center bond and it requires extremely high-level of theories to calculate the energy and structure correctly. The structures and energies of BH 5 and the transition state for the hydrogen scrambling have been studied using recently developed multi-coefficient correlated quantum mechanical methods (MCCMs). The dissociation energies and the barrier heights agree very well with the previous results at the CCSD(T)/ TZ(3d1f1g, 2p1d) level. We have also calculated the potential energy curves for the dissociation of BH 5 to BH 3 and H 2 . The lower levels of theory were unable to plot correct potential curves, whereas the MCCM methods give very good potential energy curves and requires much less computing resources than the CCSD(T)/ TZ(3d1f1g, 2p1d) level. The potential energy of the BH 5 scrambling has been obtained by the multiconfiguration molecular mechanics algorithm (MCMM), and the rates are calculated using the variational transition state theory including multidimensional tunneling approximation. The rate constant at 300 K is 2.1 × 10 9 s −1, and tunneling is very important.

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H2BH3 as an intermediate in tetrahydridoborate hydrolysis

Cited by 103 publications

References 1 publication

Mechanisms of chemical generation of volatile hydrides for trace element determination (IUPAC Technical Report)

Mechanisms of chemical generation of volatile hydrides for trace element determination (IUPAC Technical Report)

Effects of Orbital Vacancies in Boron Compounds

The Potential Energy Surface of BH₅and the Rate of the Hydrogen Scrambling

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H2BH3 as an intermediate in tetrahydridoborate hydrolysis

Cited by 103 publications

References 1 publication

Mechanisms of chemical generation of volatile hydrides for trace element determination (IUPAC Technical Report)

Mechanisms of chemical generation of volatile hydrides for trace element determination (IUPAC Technical Report)

Effects of Orbital Vacancies in Boron Compounds

The Potential Energy Surface of BH5and the Rate of the Hydrogen Scrambling

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Product

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The Potential Energy Surface of BH₅and the Rate of the Hydrogen Scrambling