Theoretical study on interaction of different coordination modes of BH4 ligand with transition metal in [TM(BH4)(CO)4]− (TM=Cr, Mo)

Ariafard, Alireza; Amini, Mostafa M.

doi:10.1016/j.jorganchem.2004.08.034

Cited by 8 publications

(4 citation statements)

References 29 publications

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“…Therefore, the calculated binding energies of Inter_4 are much smaller than that of Inter_2 . For the isolated complexes such as Ti(BH 4 ) 3 , ab initio calculations have shown that η 2 and η 3 structures are not much different in binding energy for some transition metals. ,− Obviously, there is a large difference of stability related to η 2 and η 3 ligands between the isolated complexes Ti(BH 4 ) 3 and TiB 2 H 8 − n BH 4 − in a solid-state environment.…”

Section: Resultsmentioning

confidence: 99%

Hydrogen Interaction in Ti-Doped LiBH₄ for Hydrogen Storage: A Density Functional Analysis

2009

J. Chem. Theory Comput.

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Density functional theory studies have been carried out to investigate the energetics and structures of Ti-doped LiBH4 (001), (100), and (010) surfaces. The possibilities of Ti occupying various positions at these surfaces leading to substitution, surface adsorption, and interstitial insertion are examined. Among all possible structures, a Ti atom energetically prefers to occupy interstitial positions involving three or four BH4(-) hydrides and to stay above the top layer of B atoms. The most stable species on the three surfaces have a similar local structure, described as TiB2H8-nBH4 (n = 1, 2), with varying spin states. Molecular orbital analysis for the local structures showed that the structural stability could be attributed to the symmetry-adapted orbital overlap between Ti and "inside" B-H bonds. Furthermore, the hydrogen desorption energies from many positions in these local complex structures were reduced significantly with respect to that from the clean surface. The most favorable hydrogen desorption pathways are found to lead to triplet dehydrogenation products. Therefore, the triplet TiB2H8-BH4 in (001) and TiB2H8-2BH4 in (010) can desorb hydrogen in molecular form, while the quintet TiB2H8-BH4 in (100) must first desorb hydrogen atoms, followed by the formation of a hydrogen molecule in the gas phase. The catalytic effect of Ti doped in LiBH4 has been compared with that in NaAlH4.

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Section: Resultsmentioning

confidence: 99%

Hydrogen Interaction in Ti-Doped LiBH₄ for Hydrogen Storage: A Density Functional Analysis

2009

J. Chem. Theory Comput.

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“…Complexes containing the borohydride anion BH 4 – are known for almost all transition metals and are the focus of much research over the last decades . They exhibit an extensive and diverse coordination chemistry where, in the case of mononuclear complexes, the BH 4 – ligand is coordinated in η 1 -, η 2 -, or η 3 -fashion featuring thus one, two, or three M-H-B bridges, respectively.…”

Section: Introductionmentioning

confidence: 99%

Synthesis, Structure, and Reactivity of Co(II) and Ni(II) PCP Pincer Borohydride Complexes

et al. 2015

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The 15e square-planar complexes [Co(PCPMe-iPr)Cl] (2a) and [Co(PCP-tBu)Cl] (2b), respectively, react readily with NaBH4 to afford complexes [Co(PCPMe-iPr)(η2-BH4)] (4a) and [Co(PCP-tBu)(η2-BH4)] (4b) in high yields, as confirmed by IR spectroscopy, X-ray crystallography, and elemental analysis. The borohydride ligand is symmetrically bound to the cobalt center in η2-fashion. These compounds are paramagnetic with effective magnetic moments of 2.0(1) and 2.1(1) μB consistent with a d7 low-spin system corresponding to one unpaired electron. None of these complexes reacted with CO2 to give formate complexes. For structural and reactivity comparisons, we prepared the analogous Ni(II) borohydride complex [Ni(PCPMe-iPr)(η2-BH4)] (5) via two different synthetic routes. One utilizes [Ni(PCPMe-iPr)Cl] (3) and NaBH4, the second one makes use of the hydride complex [Ni(PCPMe-iPr)H] (6) and BH3·THF. In both cases, 5 is obtained in high yields. In contrast to 4a and 4b, the borohydride ligand is asymmetrically bound to the nickel center but still in an η2-mode. [Ni(PCPMe-iPr)(η2-BH4)] (5) loses readily BH3 at elevated temperatures in the presence of NEt3 to form 6. Complexes 5 and 6 are both diamagnetic and were characterized by a combination of 1H, 13C{1H}, and 31P{1H} NMR, IR spectroscopy, and elemental analysis. Additionally, the structure of these compounds was established by X-ray crystallography. Complexes 5 and 6 react with CO2 to give the formate complex [Ni(PCPMe-iPr)(OC(C=O)H] (7). The extrusion of BH3 from [Co(PCPMe-iPr)(η2-BH4)] (4a) and [Ni(PCPMe-iPr)(η2-BH4)] (5) with the aid of NH3 to yield the respective hydride complexes [Co(PCPMe-iPr)H] and [Ni(PCPMe-iPr)H] (6) and BH3NH3 was investigated by DFT calculations showing that formation of the Ni hydride is thermodynamically favorable, whereas the formation of the Co(II) hydride, in agreement with the experiment, is unfavorable. The electronic structures and the bonding of the borohydride ligand in [Co(PCPMe-iPr)(η2-BH4)] (4a) and [Ni(PCPMe-iPr)(η2-BH4)] (5) were established by DFT computations.

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“…This provides an invaluable "handle" both for the characterization of reaction products as well as for in situ monitoring of experiments in order to identify intermediates and elucidate reaction mechanisms. Although the groundstate bonding and other properties of transition-metal-borohydride compounds have been widely studied by computational methods, [7,8] there are no studies of lanthanide analogues, and none concerning their reactivity in general and in particular in comparison with their [(L x )Ln(H)] hydride analogues.…”

Section: Introductionmentioning

confidence: 99%

A DFT Study of the Mechanism of Polymerization of ε‐Caprolactone Initiated by Organolanthanide Borohydride Complexes

Barros

Mountford

Guillaume

et al. 2008

Chemistry A European J

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The mechanisms of polymerization of epsilon-caprolactone (CL) initiated by either the rare-earth hydride [Cp2Eu(H)] or the borohydrides [Cp2Eu(BH4)] or [(N2NN')Eu(BH4)] were studied at the DFT level (Cp=eta5-C5H5; N2NN'=(2-C5H4N)CH2(CH2CH2NMe)2). For all compounds the reaction proceeds in two steps: a hydride transfer from the rare earth initiator to the carbonyl carbon of the lactone, followed by ring-opening of the monomer. In the last step a difference is observed between the hydride and borohydride complexes, because for the latter the ring-opening is induced by an additional B-H bond cleavage leading to a terminal--CH2OBH2 group. This corresponds to the reduction by BH3 of the carbonyl group of CL. Upon reaction of [Cp2Eu(H)] with CL, the alkoxy-aldehyde complex produced, [Cp2Eu(O(CH2)5C(O)H)], is the first-formed initiating species. In contrast, for the reaction of CL with the borohydride complexes [(Lx)Eu(BH4)] (Lx=Cp2 or N2NN'), an aliphatic alkoxide with a terminal--CH2OBH2 group, [(Lx)Eu(O(CH2)6OBH2)] is formed and subsequently propagates the polymerization. The present DFT investigations are fully compatible with previously reported mechanistic studies of experimental systems.

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Theoretical study on interaction of different coordination modes of BH4 ligand with transition metal in [TM(BH4)(CO)4]− (TM=Cr, Mo)

Cited by 8 publications

References 29 publications

Hydrogen Interaction in Ti-Doped LiBH₄ for Hydrogen Storage: A Density Functional Analysis

Hydrogen Interaction in Ti-Doped LiBH₄ for Hydrogen Storage: A Density Functional Analysis

Synthesis, Structure, and Reactivity of Co(II) and Ni(II) PCP Pincer Borohydride Complexes

A DFT Study of the Mechanism of Polymerization of ε‐Caprolactone Initiated by Organolanthanide Borohydride Complexes

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Theoretical study on interaction of different coordination modes of BH4 ligand with transition metal in [TM(BH4)(CO)4]− (TM=Cr, Mo)

Cited by 8 publications

References 29 publications

Hydrogen Interaction in Ti-Doped LiBH4 for Hydrogen Storage: A Density Functional Analysis

Hydrogen Interaction in Ti-Doped LiBH4 for Hydrogen Storage: A Density Functional Analysis

Synthesis, Structure, and Reactivity of Co(II) and Ni(II) PCP Pincer Borohydride Complexes

A DFT Study of the Mechanism of Polymerization of ε‐Caprolactone Initiated by Organolanthanide Borohydride Complexes

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Hydrogen Interaction in Ti-Doped LiBH₄ for Hydrogen Storage: A Density Functional Analysis

Hydrogen Interaction in Ti-Doped LiBH₄ for Hydrogen Storage: A Density Functional Analysis