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Morris Srebnik - One of the best experts on this subject based on the ideXlab platform.

  • Chapter 1 – Chemistry of the diboron compounds
    Contemporary Aspects of Boron: Chemistry and Biological Applications, 2005
    Co-Authors: H. Abu Ali, Valery M. Dembitsky, Morris Srebnik
    Abstract:

    This chapter discusses the chemistry of the diboron compounds. Diborane reagents of the general formula B 2 (OR) 4 have been utilized recently as reagents for a series of transition metal-catalyzed reactions. Synthesis of diboron compounds may involve either reductive coupling reactions of monoboron derivatives to form the boron-boron bond, or reactions of compounds possessing preformed B 2 fragments. Two aspects of the boron chemistry of this class of compounds are particularly relevant: (1) First, synthesis and properties of organodiboron derivatives and authentic synthetic failure in this area are of interest in comparison with the rich organic chemistry of monoboron derivatives. (2) Second, the chemistry of subvalent boron compounds and their interactions with organic and organometallic systems can lead to novel reactions that make organoboron derivatives accessible. BisDiborane derivatives are an important class of compounds in boron chemistry. The addition of Diboranes (X 2 B–BX 2 ) to unsaturated hydrocarbons is an attractive and straightforward method to introduce two boryl units into organic molecules. Diborane itself, B 2 H 4 , is stable only when complexed by Lewis base ligands such as amines or phosphines.

  • Tetra(pyrrolidino)Diborane(4), [(C4H8N)2B]2, as a New Improved Alternative Synthetic Route to Bis(pinacolato)Diborane(4) − Crystal Structures of the Intermediates
    European Journal of Inorganic Chemistry, 2002
    Co-Authors: Hijazi Abu Ali, Israel Goldberg, Morris Srebnik
    Abstract:

    The compound tetra(pyrrolidino)Diborane(4) (3) is an important new and alternative precursor for the preparation and synthesis of bis(pinacolato)Diborane(4). The latter is the major intermediate among the Diborane derivatives used for many addition and insertion reactions into multiple bonds. The crystal structure of 3 and its precursor, tris(pyrrolidino)borane, 1, were determined. In addition the solvolysis reactions and solution behavior of 3 with alcohols were examined.

  • tetra pyrrolidino Diborane 4 c4h8n 2b 2 as a new improved alternative synthetic route to bis pinacolato Diborane 4 crystal structures of the intermediates
    European Journal of Inorganic Chemistry, 2002
    Co-Authors: Hijazi Abu Ali, Israel Goldberg, Morris Srebnik
    Abstract:

    The compound tetra(pyrrolidino)Diborane(4) (3) is an important new and alternative precursor for the preparation and synthesis of bis(pinacolato)Diborane(4). The latter is the major intermediate among the Diborane derivatives used for many addition and insertion reactions into multiple bonds. The crystal structure of 3 and its precursor, tris(pyrrolidino)borane, 1, were determined. In addition the solvolysis reactions and solution behavior of 3 with alcohols were examined.

Sundargopal Ghosh - One of the best experts on this subject based on the ideXlab platform.

  • Diborane(6) and Its Analogues Stabilized by Mono-, Bi-, and Trinuclear Group 7 Templates Combined Experimental and Theoretical Studies
    Inorganic Chemistry, 2020
    Co-Authors: Rini Prakash, Alaka Nanda Pradhan, Madhuri Jash, Samia Kahlal, Marie Cordier, Thierry Roisnel, Jean-françois Halet, Sundargopal Ghosh
    Abstract:

    Irradiation of [Re(CO)] in the presence of BH·thf resulted in the formation of several rhenium Diborane(6) species, for example, [{(OC)Re}{Re(CO)}(μ-η:η:η-BH)(μ-H)], ; [{(OC)Re}{Re(CO)}(μ-η:η:η-BH)(μ-H)], ; and [{(OC)Re}(μ-η:η-BH)], , comprising diverse coordination modes of the [BH] ligand. Compound contains a tris(bidentate) [BH] unit, whereas consists of an unsymmetrically bound [μ-η:η:η-BH] ligand. In contrast, the irradiation of [Mn(CO)] with BH·thf yielded only the Mn analogue of , [{(OC)Mn}{Mn(CO)}(μ-η:η:η-BH)(μ-H)], . In an attempt to generate the bimetallic Mn-Diborane(6), we have carried out the reaction of with PCy under photolytic conditions. The reaction led to the formation of two single base stabilized unsymmetrical Diborane(5) species, [{Mn(CO)}{Mn(CO)PCy}(μ-η:η-BH·PCy)(μ-H)], , and [{Mn(CO)PCy}(η-BH·PCy)], . As [BH] and [BH·PCy] are isoelectronic, the bondings in and are analogous to that of Diborane(6) species -. All the new species have been characterized spectroscopically, and their structures were further confirmed by single-crystal X-ray diffraction studies. DFT-type quantum chemical calculations were carried out that provided insight into the bonding interaction of [BH] and [BH·PCy] with the M(CO) fragments.

  • Recent advances in transition metal Diborane(6), Diborane(4) and diborene(2) chemistry
    Coordination Chemistry Reviews, 2019
    Co-Authors: Rosmita Borthakur, Koushik Saha, Sourav Kar, Sundargopal Ghosh
    Abstract:

    Abstract Diborane(4) and Diborane(6) molecules are demanding renewed interest due to their varied reactivity towards diverse substrates. The chemistry of molecules comprising electron-precise B-B bonds has witnessed swift developments in the recent years. In spite of the continuous interest and extensive efforts in the synthesis of Diborane compounds, the formation of boron-boron bonds is still difficult and uncontrolled. On the other hand, the diborene molecules (R-B B-R′; R, R′ = H, phosphine, amine, NHC etc), are also of significant interest owing to their ability to regulate the property of biradicals by changing the substituents of the parent diborene(2), HB BH. In addition, transition metal diborene species exhibit fascinating photo-physical properties. In this review, we have delivered a background of B-B bond formation and a synopsis of the latest developments in the synthesis of boron-boron single and multiple bonds. The reactivity of Diborane/diborene complexes towards various transition metals has also been discussed in detail.

Holger Braunschweig - One of the best experts on this subject based on the ideXlab platform.

  • Diborane(4) Azides: Surprisingly Stable Sources of Transient Iminoboranes.
    Angewandte Chemie (International ed. in English), 2020
    Co-Authors: Torsten Thiess, Guillaume Bélanger-chabot, Felipe Fantuzzi, Maximilian Michel, Moritz Ernst, Bernd Engels, Holger Braunschweig
    Abstract:

    Herein we describe the first examples of isolable electron-precise Diboranes(4) that bear azide moieties: the acyclic 1,2-diazido-1,2-bis(dimethylamino)Diborane(4) and the cyclic 1,4-diaryl-2,3-diazido-1,4-diaza-2,3-diborinines (aryl=mesityl, 2,6-xylyl, 4-tolyl). The reported examples are not only stable enough to be observed and isolated (putative transient Diborane(4) azides previously reported by our group spontaneously decompose even below room temperature), but some of them are even robust enough to undergo controlled pyrolysis without explosive decomposition at temperatures well above 100 °C. In two cases, the controlled pyrolysis allows the isolation of complex diazaboretidines, which are the apparent dimerization products of endocyclic boryl-iminoboranes.

  • Hydrophosphination of boron–boron multiple bonds
    Chemical Science, 2020
    Co-Authors: Tom E. Stennett, Arumugam Jayaraman, Tobias Brückner, Lea Schneider, Holger Braunschweig
    Abstract:

    Five compounds containing boron–boron multiple bonds are shown to undergo hydrophosphination reactions with diphenylphosphine in the absence of a catalyst. With diborenes, the products obtained are highly dependent on the substitution pattern at the boron atoms, with both 1,1- and 1,2-hydrophosphinations observed. With a symmetrical diboryne, 1,2-hydrophosphination yields a hydro(phosphino)diborene. The different mechanistic pathways for the hydrophosphination of diborenes are rationalised with the aid of density functional theory calculations.

  • unprecedented borane Diborane 3 diborene and borylene ligands via pt mediated borane dehydrogenation
    Journal of the American Chemical Society, 2016
    Co-Authors: Nicole Arnold, Holger Braunschweig, Rian D Dewhurst, William C. Ewing
    Abstract:

    Reactions of an aryldihydroborane with a Pt0 complex lead to a range of novel products, including complexes with bridging diborene and Diborane(3) ligands and a complex with both borylene and borane (M → B) ligands. The products imply varying degrees of dehydrogenation of the boron centers with concomitant formation of boron–boron bonds, which in one case is later broken. These reactions show that although the dehydrocoupling of dihydroboranes is not a straightforward process in this case, the reactions are capable of connecting boron atoms in unusual ways, leading to unprecedented bonding motifs.

  • Reductive Insertion of Elemental Chalcogens into Boron–Boron Multiple Bonds
    Angewandte Chemie, 2015
    Co-Authors: Holger Braunschweig, Thomas Kramer, Theresa Dellermann, William C. Ewing, Christoph Schneider, Stefan Ullrich
    Abstract:

    The syntheses of sulfur- and selenium-bridged cyclic compounds containing boron stabilized by N-heterocyclic carbenes (NHCs) have been achieved by the reductive insertion of elemental chalcogens into boron-boron multiple bonds. The three pairs of bonding electrons between the boron atoms in the triply bonded diboryne enabled six-electron reduction reactions, resulting in the formation of [2.2.1]-bicyclic systems wherein bridgehead boron atoms are spanned by three chalcogen bridges. A similar reaction using a diborene (boron-boron double bond) resulted in the reductive transfer of both pairs of bonding electrons to three sulfur atoms, yielding a NHC-stabilized trisulfidodiborolane. The demonstration of these six- and four-electron reductions lends support to the presence of three and two pairs of bonding electrons between the boron atoms of the diboryne and diborene, respectively, a fact that may be useful in future discussions on bond order.

  • Quaternizing Diboranes(4): highly divergent outcomes and an inorganic Wagner-Meerwein rearrangement.
    Journal of the American Chemical Society, 2013
    Co-Authors: Holger Braunschweig, Rian D Dewhurst, Krzysztof Radacki, Alexander Damme, Thomas Kramer, Thomas Kupfer, Eva Siedler, Alexandra Trumpp, Katharina Wagner, Christine Werner
    Abstract:

    Apart from a few compounds under heavy use in organic chemistry, Diboranes are relatively exotic and poorly understood. Recently, interest in these molecules has intensified with the advent of so-called “sp2–sp3” Diboranes which exhibit useful reactivity toward organic substrates. In our hands, addition of Lewis bases to dihalodiorganyl Diboranes(4) has previously shown some very surprising reactivity, including a substituent exchange between the boron atoms, and Diboranes in which halide atoms bridge the B–B bond. Herein we have expanded the range of Diborane(4) and Lewis base reaction partners, in the process uncovering three new reactivity patterns as well as some cases where mixtures are obtained. Trends are established for the preferential formation of certain products which rationalize the results based on electronic and steric effects. The substituent exchange, clearly based on an inorganic version of the well-known Wagner–Meerwein rearrangement, was also found to be an equilibrium reaction with th...

Israel Goldberg - One of the best experts on this subject based on the ideXlab platform.

Horst Hahn - One of the best experts on this subject based on the ideXlab platform.

  • Diborane release from libh4 silica gel mixtures and the effect of additives
    Journal of Physical Chemistry C, 2007
    Co-Authors: J Kostka, Wiebke Lohstroh, Maximilian Fichtner, Horst Hahn
    Abstract:

    LiBH4 that has been ball-milled with different additives and subsequently mixed with mesoporous silica-gel has been investigated using thermal desorption spectroscopy and thermogravimetry. Mixtures of LiBH4 and mesoporous silica-gel (composition 50:50 wt %) release hydrogen at ∼260 °C. Samples, where LiBH4 was ball-milled prior to mixing with silica-gel with 5 mol % PdCl2, NiCl2, LaCl3 or TiCl3, have similar decomposition temperatures. Mass spectrometry data of the emitted gas streams show that almost all hydrogen desorption events are accompanied by the evolution of gaseous Diborane, B2H6. The relative Diborane concentration above 350 °C is considerably lowered by LaCl3 and TiCl3, whereas the other additives investigated have little influence on the amount of released Diborane.