The room‐temperature, ambient‐pressure reactions of CO2 with two species containing boron–boron multiple bonds led to the incorporation of either one or two CO2 molecules. The structural ...characterization of a thermally unstable intermediate in one case indicates that an initial 2+2 cycloaddition is the key step in the reaction mechanism.
B active: The reaction of CO2 at room temperature and ambient pressure with two species containing boron–boron multiple bonds has led to the incorporation of either one or two CO2 molecules.
Lewis‐Base‐Induced Disproportionation of a Dialane Hofmann, Alexander; Lamprecht, Anna; Jiménez‐Halla, J. Oscar C. ...
Chemistry : a European journal,
August 9, 2018, Volume:
24, Issue:
45
Journal Article
Peer reviewed
The reaction of a pentamethylcyclopentadienyl‐substituted dialane with a variety of Lewis bases results in unexpected disproportionation of the dialane into AlI and AlIII species. Use of a ...transition‐metal Lewis base allows for the formation of metal‐only Lewis pairs. Furthermore, the synthesis of a Lewis base bis‐adduct was successful with the Lewis base 4‐dimethylaminopyridine.
Aluminum chemistry: The reaction of a pentamethylcyclopentadienyl‐substituted dialane with a variety of Lewis bases is presented, resulting in unexpected disproportionation of the dialane into AlI and AlIII species, formation of a metal‐only Lewis pair, and simple base addition.
B₁₉ ⁻: An Aromatic Wankel Motor Jiménez-Halla, J. Oscar C; Islas, Rafael; Heine, Thomas ...
Angewandte Chemie (International ed.),
August 2, 2010, Volume:
49, Issue:
33
Journal Article
Peer reviewed
The magic roundabout: The B19− cluster behaves like a molecular Wankel engine (see picture) in which the two concentric boron rings rotate in opposite directions. During the rotation the cluster ...remains planar owing to a marginal rotational energy barrier.
The transfer hydrogenation of N‐heterocyclic carbene (NHC)‐supported diborenes with dimethylamine borane proceeds with high selectivity for the trans‐1,2‐dihydrodiboranes. DFT calculations, supported ...by kinetic studies and deuteration experiments, suggest a stepwise proton‐first‐hydride‐second reaction mechanism via an intermediate μ‐hydrodiboronium dimethylaminoborate ion pair.
Game of borons: The transfer hydrogenation of apolar cis‐ and trans‐diborenes with dimethylamine borane as the hydrogen source proceeds with high selectivity for the corresponding trans‐1,2‐dihydrodiboranes. DFT calculations, supported by kinetic data, reveal a new reaction mechanism proceeding via a proton‐first‐hydride‐second pathway through an intermediate μ‐hydrodiboronium aminoborate ion pair.
We have quantum chemically investigated the boron‐boron bonds in B2, diborynes B2L2, and diborenes B2H2L2 (L=none, OH2, NH3) using dispersion‐corrected relativistic density functional theory at ...ZORA‐BLYP‐D3(BJ)/TZ2P. B2 has effectively a single B−B bond provided by two half π bonds, whereas B2H2 has effectively a double B=B bond provided by two half π bonds and one σ 2p–2p bond. This different electronic structure causes B2 and B2H2 to react differently to the addition of ligands. Thus, in B2L2, electron‐donating ligands shorten and strengthen the boron‐boron bond whereas, in B2H2L2, they lengthen and weaken the boron‐boron bond. The aforementioned variations in boron‐boron bond length and strength become more pronounced as the Lewis basicity of the ligands L increases.
The different electronic structure of B2 and B2H2 makes them to react differently to the addition of ligands. Hence, in B2L2, electron‐donating ligands shorten and strengthen the boron‐boron bond whereas, in B2H2L2, they elongate and weaken the boron‐boron bond.
Carbene‐stabilized diborynes of the form LBBL (L=N‐heterocyclic carbene (NHC) or cyclic alkyl(amino)carbene (CAAC)) induce rapid, high yielding, intermolecular ortho‐C−H borylation at N‐heterocycles ...at room temperature. A simple pyridyldiborene is formed when an NHC‐stabilized diboryne is combined with pyridine, while a CAAC‐stabilized diboryne leads to activation of two pyridine molecules to give a tricyclic alkylideneborane, which can be forced to undergo a further H‐shift resulting in a zwitterionic, doubly benzo‐fused 1,3,2,5‐diazadiborinine by heating. Use of the extended N‐heteroaromatic quinoline leads to a borylmethyleneborane under mild conditions via an unprecedented boron‐carbon exchange process.
Carbene‐stabilized diborynes of the form LBBL (L=N‐heterocyclic carbene or cyclic alkyl(amino)carbene) induce rapid, high yielding, intermolecular ortho‐C−H borylation at N‐heterocycles at room temperature. The reaction initially provides the simple hydroarylated diborene, but in some cases proceeds further, providing unusual 1,3,2,5‐diazadiborinine and base‐stabilized alkylidene products.
The reductive coupling of a N-heterocyclic carbene (NHC)-stabilized aryldibromoborane yields a mixture of trans- and cis-diborenes in which the aryl groups are coplanar with the diborene core. Under ...dilute reduction conditions two diastereomers of a borirane–borane intermediate are isolated, which upon further reduction give rise to the aforementioned diborene mixture. DFT calculations suggest a mechanism proceeding via nucleophilic attack of a dicoordinate borylene intermediate on the aryl ring and subsequent intramolecular B–B bond formation.
Magnesium‐based catalysts are becoming popular for hydroelementation reactions specially using p‐block reagents. Based on the seminal report from Schäfer's group (ChemCatChem 2022, 14, e202201007), ...our study demonstrates that the reaction mechanisms exhibit a far greater degree of complexity than originally presumed. Magnesium has a variety of coordination modes (and access to different hybridizations) which allows this electron‐deficient centre to modulate its catalytic power depending on the σ‐donor properties of the reagent. DFT calculations demonstrate several reaction channels closely operating in these versatile catalysts. In addition, variations in limiting energy barriers resulting from catalyst modifications were examined as a function of the Hammett constant, thereby predicting enhanced efficiency in reaction conversions.
Show me how many ligands you accept, and I will tell you how you react: depending on the number of ligands that the ansa‐half‐sandwich magnesium catalyst can bind, our DFT calculations show that the mechanism proceeds differently with competitive reaction channels.
Doubly N-heterocyclic-carbene-stabilized diborenes undergo facile reactions with CO2, initially providing dibora-β-lactones. These lactones convert over time to their 2,4-diboraoxetan-3-one isomers ...through a presumed dissociative pathway and hypovalent boron species borylene carbonyls (LHBCO) and base-stabilized oxoboranes (LHBO). Repeating these reactions with doubly cyclic(alkyl)(amino)carbene-stabilized diborenes allowed the isolation of a borylene carbonyl intermediate, whereas a base-stabilized oxoborane could be inferred by the isolation of a boroxine from the reaction mixture. These results, supported by calculations, confirm the presumed mechanism of the diboralactone-to-diboraoxetanone isomerization while also establishing a surprising level of stability for three unknown or very rare hypovalent boron species: base-stabilized derivatives of the parent borylene carbonyl (LHBCO) and parent oxoborane (LHBO) as well as base-free oxoboranes (RBO).
Transition‐Metal π‐Ligation of a Tetrahalodiborane Braunschweig, Holger; Dewhurst, Rian D.; Jiménez‐Halla, J. Oscar C. ...
Angewandte Chemie International Edition,
January 8, 2018, Volume:
57, Issue:
2
Journal Article
Peer reviewed
The reaction of tetraiododiborane (B2I4) with trans‐Pt(BI2)I(PCy3)2 gives rise to the diplatinum(II) complex {(Cy3P)(I2B)Pt}2(μ2:η3:η3‐B2I4), which is supported by a bridging diboranyl dianion ligand ...B2I42−. This complex is the first transition‐metal complex of a diboranyl dianion, as well as the first example of intact coordination of a B2X4 (X=halide) unit of any type to a metal center.
Million dollar BB: The reaction of tetraiododiborane with trans‐Pt(BI2)I(PCy3)2 gives rise to a diplatinum(II) complex supported by a bridging B2I4 unit. This complex is the first transition‐metal complex of a diboranyl dianion, as well as the first example of intact coordination of a B2X4 (X=halide) unit of any type to a metal center.
PDF
