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The ditriflato‐diborane B2(μ‐hpp)2(OTf)2 (hpp=1,3,4,6,7,8‐hexahydro‐2H‐pyrimido[1,2‐a]pyrimidinate) acts as a stable surrogate of the elusive dication [B2(hpp)2]2+, being both electrophilic (vacant boron p orbitals) and nucleophilic (filled B−B bond orbital). This combination of seemingly contrasting behaviors could be used to develop a metallomimetic diborane chemistry, with Lewis σ‐basic and π‐acidic substrates being bound and reduced at the diborane. Here, we report on a novel reaction type within this general theme, in which double electron transfer from the diboron unit to the boron–bound organic substrate is coupled with halide transfer in the other direction. Novel diborylated dienamines are synthesized in this way. The scope of this unprecedented reaction motif and the reaction pathways are elucidated. [ABSTRACT FROM AUTHOR]

The synthesis of the first terminal mono‐boryl complexes of nickel, which are not stabilized by a pincer ligand, is reported. The reaction of the nickel bis‐boryl complex cis‐[Ni(iPr2ImMe)2(Bcat)2] 1 (cat=1,2‐O2C6H4) with the small donor ligand PMe3 led to a complete ligand exchange at nickel with reductive elimination of B2cat2 and formation of the bis‐NHC adduct [B2cat2 ⋅ (iPr2ImMe)2] 3 and [Ni(PMe3)4] 2 as the metal‐containing species. Electrophilic attack of MeI on complex 1 or ligand dismutation of 1 with trans‐[Ni(iPr2ImMe)2Br2] led to loss of only one boryl ligand of 1 and afforded the nickel mono‐boryl complexes trans‐[Ni(iPr2ImMe)2(Bcat)Br] 4 a and trans‐[Ni(iPr2ImMe)2(Bcat)I] 4 b. [ABSTRACT FROM AUTHOR]

The reaction of tetra(o‐tolyl)diborane(4) with organic azides afforded three different compounds, diborylamines, diboryltriazenes, and B2‐hexazenes having a bicyclic B2N6 ring system. The reaction with aryl azides gave diborylamines, while the reaction with 1 equiv. of alkyl azides furnished diboryltriazenes. In the case of the reaction with an excess amount of primary alkyl azide, a new heterocyclic B2‐hexazenes were obtained. The formation of the B2N6 structure could be explained by one general reaction mechanism via the diboryltriazene intermediate according to the control experiments and DFT calculations. The B2‐hexazenes exhibited a strong fluorescence with a remarkably high fluorescent quantum yield of up to 96 %. [ABSTRACT FROM AUTHOR]

The mechanisms of direct deoxygenative borylation of acetone and benzaldehyde with bis(catecholato)diborane (B2cat2) in the solvent N,N‐dimethylacetamide (DMA) are investigated through detailed density functional theory calculations. These calculations show that the isomer 1,2‐B2cat2 in situ generated from 1,1‐B2cat2 induced by DMA is the reactive boron intermediate for the reactions. The addition of the B−B bond of 1,2‐B2cat2 to the C=O bond of acetone or benzaldehyde via a concerted [2σ+2π]‐cycloaddition‐like transition state is the rate‐limiting step for both the triboration reaction of acetone and the monoboration reaction of benzaldehyde. DMA not only acts as the solvent but also promotes the structural isomerization of B2cat2, the deoxygenation of acetone to form the vinyl boronate intermediate and subsequent diboration of vinyl boronate with 1,2‐B2cat2, as well as the protodeboronation of the gem‐diboronate intermediate in the deoxygenative borylation of benzaldehyde. The presented computational results can explain the observed experimental facts and provide insight into the roles of the isomeric 1,2‐B2cat2 and the solvent DMA in related reactions. [ABSTRACT FROM AUTHOR]

Derived from structurally similar precursors, two different azidodiboranes went through distinct aryl migration reactions triggered by different boron‐boron separation distances. Biphenylene based diborane with a shorter boron‐boron distance underwent heterolateral aryl migration to form a seven‐membered azadiborepin, while xanthrene based diborane with a longer boron‐boron distance afforded a stable bis‐azidoborane scaffold. The pyrolysis of such a bis‐azidoborane led to eight‐membered oxazadiborocine through homolateral aryl migration and subsequent [3+2] cycloaddition. Density functional theory (DFT) calculations unveiled that the boron‐boron separation distances were the intrinsic factors for the distinct migrations. [ABSTRACT FROM AUTHOR]

The B‐nucleophilic 9H‐9‐borafluorene dianion reacts with 9‐chloro‐9‐silafluorene to afford air‐ and moisture‐stable silylborate salts M[Ar2(H)B−Si(H)Ar2] (M[HBSiH], M=Li, Na). Li[HBSiH] and Me3SiCl give the B−pyridine adduct Ar2(py)B−Si(H)Ar2 ((py)BSiH) or the chlorosilane Li[Ar2(H)B−Si(Cl)Ar2] (Li[HBSiCl]) in C6H6‐pyridine or THF. In both cases, the first step is H− abstraction at the B center. The resulting free borane subsequently binds a py or thf ligand. While the py adduct is stable at room temperature, the thf adduct undergoes a 1,2‐H shift via the cyclic B(μ‐H)Si intermediate BHSi, which is afterwards attacked at the Si atom by a Cl− ion to give Li[HBSiCl]. DFT calculations were employed to support the proposed reaction mechanism and to characterize the electronic structure of BHSi. Treatment of Li[HBSiCl] with the N‐heterocyclic carbene IMe introduces the neutral donor at the Si atom and leads to Ar2(H)B−Si(IMe)Ar2 (HBSi(IMe)), a donor‐acceptor‐stabilized silylene. [ABSTRACT FROM AUTHOR]

In this work we report the first cycloaddition reactions between a diazido diborane(4) and terminal alkynes, providing unique access to bis‐1,2,3‐triazoles connected by a B−B bridge. The catalyst‐free reactions are highly selective, yielding exclusively the thermodynamically disfavored bis‐1,4‐triazoles. The reactions are enabled by the high thermal stability of the diazido‐diborane [B(hpp)(N3)]2 (hpp=1,3,4,6,7,8‐hexahydro‐2H‐pyrimido[1,2‐α]pyrimidinate). Due to the tetra‐coordinate boron atoms in this reagent, the reactions are tolerant with respect to the introduction of Lewis‐basic groups at the alkyne. The scope and limitations of the new reactions are discussed. [ABSTRACT FROM AUTHOR]

The chemistry of dicationic diboranes with two BII atoms that are engaged in direct B−B bonding is by enlarge unexplored, although these molecules have intriguing properties due to their combined Lewis acidic and electron‐donor properties. Unsymmetric dicationic diboranes are extremely rare, but especially attractive due to their polarized B−B bond. In this work we report the directed synthesis of several stable unsymmetric dicationic diboranes by reaction between the electron‐rich ditriflato‐diborane B2(hpp)2(OTf)2 (hpp=1,3,4,6,7,8‐hexahydro‐2H‐pyrimido[1,2‐α]pyrimidinate) and phosphino‐pyridines, establishing B−N and B−P bonds with the diborane concomitant with triflate elimination. In the case of 2‐((ditertbutylphosphino)methyl)pyridine, the B−N bond is formed instantly, but the B−P bond formation requires (due to steric constraints) several days at ambient conditions for completion, creating an intermediate that could be used for frustrated Lewis pair (FLP)‐like chemistry. Here we test its reaction with an aldehyde, and propose a new type of FLP‐like chemistry. [ABSTRACT FROM AUTHOR]

Reaction of the Ga(I) compound NacNacGa (9) with the diazo compound N2CHSiMe3 affords the nitrilimine compound NacNacGa(N‐NCSiMe3)(CH2SiMe3) (10). Carrying out this reaction in the presence of pyridine does not lead to C−H activation on the transient alkylidene NacNacGa=CHSiMe3 but generates a metallated diazo species NacNacGa(NHN=CHSiMe3)(CN2SiMe3) (13) that further rearranges into the isonitrile compound NacNacGa(NHN=CHSiMe3)(N(NC)SiMe3) (15). Reactions of 10 with the silane H3SiPh and the borane HBcat furnished products of 1,3 addition to the nitrilimine moiety NacNacGa{N(ERn)NCSiMe3}(CH2SiMe3), whereas reaction with the diborane B2cat2 gave the product of formal nitrene insertion into the B−B bond. DFT calculations suggest that the interaction of 9 with N2CHSiMe3 proceeds through intermediate formation of an alkylidene compound that undergoes CH activation with a second molecule of N2CHSiMe3. Insertion into the B−B bond likely proceeds through an initial 1,3‐addition of the diborane, followed by boryl migration to the former nitrene center. [ABSTRACT FROM AUTHOR]

A number of novel alkynyl‐functionalized diarylbis(dimethylamino)diboranes(4) are prepared by salt metathesis, and the appended alkynyl groups are subjected to hydroboration. Their reactions with monohydroboranes lead to discrete boryl‐appended diborane(4) species, while dihydroboranes induce their catenation to oligomeric species, the first known examples of well‐characterized macromolecular species with B−B bonds. The oligomeric species were found to comprise up to ten repeat units and are soluble in common organic solvents. Some of the oligomeric species have good air stability and all were characterized by NMR and vibrational spectroscopy and size‐exclusion chromatography techniques. [ABSTRACT FROM AUTHOR]

A 1,8‐naphthyridine diphosphine (NDP) reacts with boron‐containing Lewis acids to generate complexes featuring a number of different naphthyridine bonding modes. When exposed to diborane B2Br4, NDP underwent self‐deprotonation to afford [NDP‐B2Br3]Br, an unsymmetrical diborane comprised of four fused rings. The reaction of two equivalents of monoborane BBr3 and NDP in a non‐polar solvent provided the simple phosphine‐borane adduct [NDP(BBr3)2], which then underwent intramolecular halide abstraction to furnish the salt [NDP‐BBr2][BBr4], featuring a different coordination mode from that of [NDP‐B2Br3]Br. Direct deprotonation of NDP by KHMDS or PhCH2K generates mono‐ and dipotassium reagents, respectively. The monopotassium reagent reacts with one or half an equivalent of B2(NMe2)2Cl2 to afford NDP‐based diboranes with three or four amino substituents. [ABSTRACT FROM AUTHOR]

Cationic cyclophanes are widely used in a variety of applications in supramolecular chemistry and materials science. In this work the authors systematically study the integration of electron‐rich diboron units with BII atoms into polycationic cyclophanes with viologen‐like electron‐acceptor units. They also report a first hexacationic cage‐compound in which three diboron units connect two tris(4‐pyridyl)triazine acceptor units. Moreover, di‐ and tetracationic open‐structure compounds, in which one diboron unit connects two bispyridyl groups, were synthesized and the properties compared to those of the corresponding closed structures (cyclophanes). The combination of diboron electron‐donor units and bi‐ or oligopyridyl electron‐acceptor units leads to intriguing optical and redox properties. [ABSTRACT FROM AUTHOR]

Diplatinum A‐frame complexes with a bridging (di)boron unit in the apex position were synthesized in a single step by the double oxidative addition of dihalo(di)borane precursors at a bis(diphosphine)‐bridged Pt02 complex. While structurally analogous to well‐known μ‐borylene complexes, in which delocalized dative three‐center‐two‐electron M‐B‐M bonding prevails, theoretical investigations into the nature of Pt−B bonding in these A‐frame complexes show them to be rare dimetalla(di)boranes displaying two electron‐sharing Pt−B σ‐bonds. This is experimentally reflected in the low kinetic stability of these compounds, which are prone to loss of the (di)boron bridgehead unit. [ABSTRACT FROM AUTHOR]

Herein reported are the reactions of an electron‐rich, Lewis acidic diborane with N‐heterocyclic aromatics to give first members of an unprecedented family of highly charged cationic cyclophanes with diboranyl units. Tetracationic cyclophanes with 4,4'‐bipyridine/ 1,2‐bis(4‐pyridyl)ethylene and diboranyl units were synthesized and their redox chemistry was studied. Cyclisation of two diboranyl and two pyrazine units is accompanied by electron transfer from the diboranyl unit to the pyrazine. Our results pave the way for the integration of redox‐active diboranyl units into cyclophanes and supramolecular structures. [ABSTRACT FROM AUTHOR]

A cyclic (alkyl)(amino)carbene (CAAC) has been shown to react with a covalent azide similar to the Staudinger reaction. The reaction of MeCAAC with trimethylsilyl azide afforded the N‐silylated 2‐iminopyrrolidine (MeCAAC=NSiMe3), which was fully characterized. This compound undergoes hydrolysis to afford the 2‐iminopyrrolidine and trimethylsiloxane which co‐crystallize as a hydrogen‐bonded adduct. The N‐silylated 2‐iminopyrrolidine was used to transfer the novel pyrrolidine‐2‐iminato ligand onto both main‐group and transition‐metal centers. The reaction of the tetrabromodiborane bis(dimethyl sulfide) adduct with two equivalents of MeCAAC=NSiMe3 afforded the disubstituted diborane. The reaction of MeCAAC=NSiMe3 with TiCl4 and CpTiCl3 afforded MeCAAC=NTiCl3 and MeCAAC=NTiCl2Cp, respectively. [ABSTRACT FROM AUTHOR]

A series of 22 new bis(phosphine), bis(carbene), and bis(isonitrile) tetrahalodiborane adducts has been synthesized, either by direct adduct formation with highly sensitive B2X4 precursors (X=Cl, Br, I) or by ligand exchange at stable B2X4(SMe2)2 precursors (X=Cl, Br) with labile dimethylsulfide ligands. The isolated compounds have been fully characterized using NMR spectroscopy, elemental analysis, and, for 20 of these compounds, single‐crystal X‐ray diffraction, revealing an unexpected variation in the bonding motifs. In addition to the classical B2X4L2 diborane(4) bis‐adducts, certain more sterically demanding carbene ligands induce a halide displacement which led to the first halide‐bridged monocationic diboron species, [B2X3L2]A (A=BCl4, Br, I). Furthermore, low‐temperature 1:1 reactions of B2Cl4 with sterically demanding N‐heterocyclic carbenes led to the formation of kinetically unstable mono‐adducts, one of which was structurally characterized. A comparison of the NMR spectra and structural data of new and literature‐known bis‐adducts shows several trends pertaining to the nature of the halides and the stereoelectronic properties of the Lewis bases employed. [ABSTRACT FROM AUTHOR]

A new boron–boron dehydrocoupling strategy was established, providing convenient access to some diborane(4) compounds starting from simple borane adducts under mild conditions. In contrast to the traditional pathway using a reducing reagent, the reduction from BIII to BII was paradoxically initiated by the addition of the oxidation‐reagent iodine. A reaction pathway for this unusual reaction was proposed based on quantum‐chemical calculations. [ABSTRACT FROM AUTHOR]

Hydroboration generally requires the presence of a catalyst to lower the barrier for hydride transfer. This work reports on the first catalyst‐free CO2 hydroboration with a neutral boron compound, the nucleophilic diborane [HB(hpp)]2, 1 (hpp=1,3,4,6,7,8‐hexahydro‐2H‐pyrimido[1,2‐a]pyrimidinate). Further hydroboration reactions to bis(boryl)acetals are possible. In acetonitrile, but not in dichloromethane solutions, hydroboration of a first CO2 is followed by hydroboration of a second CO2 molecule. Detailed kinetic measurements for both hydroboration steps were carried out and the influence of the solvent and the addition of a Lewis base on the rate constants analyzed. In contrast to catalyst‐free hydroboration of CO2, hydroboration of the less electrophilic acetone requires the presence of an activating Lewis acid. Nucleophilic diboranes enable the hydroboration of electron‐poor substrates, including the first catalyst‐free CO2 hydroboration by a neutral boron compound. Their scope is complimentary to the traditionally applied electrophilic boranes. [ABSTRACT FROM AUTHOR]

Abstract: The electron‐rich, double‐base stabilized dihydrido‐diborane(4) [HB(hpp)]2 (hpp=1,3,4,6,7,8‐hexahydro‐2H‐pyrimido[1,2‐a]pyrimidinate) combines two different, easily accessible reactive sites: the B−B and B−H bond. Herein, we report two basically similar reactions of [HB(hpp)]2 with catecholborane and B‐chlorocatecholborane unsuspectedly resulting in two different reactivities. While reaction of the diborane with two equivalents of HB(cat) proceeded with formation of a cationic triborane with a (3c2e) bond, [{HB(μ‐hpp)}2(μ‐BH2)]+, reaction with ClB(cat) led to hydride–chloride substitution yielding [ClB(hpp)]2. The cationic triborane was also obtained by the addition of BH3 to the in situ generated [HB(hpp)2B]+. Proceeding from the new compound [ClB(hpp)]2, we investigated its reactivity towards chloride abstraction with AlCl3 and GaCl3. Irrespectively of the salt chosen, the reaction led to formation of a radical tricationic tetraborane [{B(hpp)}4].3+ with a (4c,5e) bond. Moreover, the dichloro‐diborane proves as a versatile reagent for further substitution cleanly reacting with the strong nucleophile nBuLi to a new dibutyl‐diborane [nBuB(hpp)]2. [ABSTRACT FROM AUTHOR]

The first heptacoordinate cobalt catalyst for light-driven hydrogen production in water has been synthesized and characterized. Photochemical experiments using [Ru(bpy)3]2+ as photosensitizer gave a turnover number (TON) of 16300 mol H2 (mol cat.)−1 achieved in 2 hours of irradiation with visible (475 nm) light. This promising result provides a path forward in the development of new structures to improve the efficiency of the catalysis. [ABSTRACT FROM AUTHOR]

Two new diboranes, 2,6-bis(BMes2)mesitylene ( 1) and 3,3′-bis(BMes2)bimesitylene ( 3), were synthesized. Two-electron reduction of 1 with elemental potassium afforded the C−H activation product [(18-c-6)K(THF)2]2+⋅ 22− bearing a BC3 four-membered ring as colorless crystals, whereas the reduction of 3 with potassium led to the isolation of [(18-c-6)K(THF)2]2+⋅ 32−.. as dark blue crystals. Both reduction products were characterized by structural and spectroscopic methods. Electron paramagnetic resonance (EPR) spectroscopy and theoretical calculations revealed that the electron spin density of 32−.. mainly resides on the two boron nuclei and features a triplet ground state, which was confirmed by superconducting quantum interference device (SQUID) measurements as well as theoretical calculations. 32−.. represents the first structurally characterized boron-centered diradical with a triplet ground state. In addition, the reactivity of [(18-c-6)K(THF)2]2+⋅ 32−.. toward PhSeSePh and nBu3SnH was investigated, which is consistent with its radical character. [ABSTRACT FROM AUTHOR]

A comprehensive study of the reactivity of Lewis bases with dihalodiboranes(4) is presented. Diaryldihalodiboranes provide rearranged monoadducts when treated with cyclic (alkyl)(amino)carbenes, but halide-bridged adducts when treated with a range of pyridyl bases. Alternatively, the combination of diaminodihalodiboranes with strong carbene donors leads to boraborenium salts. The reduction and halide-abstraction reactivity of these adducts was also explored, leading to intramolecular C-H activation and the first 1,2-bis(borenium) dication. [ABSTRACT FROM AUTHOR]

The reaction of tert-butylisonitrile ( tBuNC) with 1,2-dihalo-1,2-diduryldiborane leads initially to the formation of the mono-base adduct of the symmetrical diborane(4), which then undergoes an intramolecular cyclization resulting in the formation of a 1-boraindane. This result is in contrast to a previously reported cyclization of a mono-isonitrile adduct of an unsymmetrical 1,1-pinacol-2,2-diaryldiborane(4), which results in the formation of a 1-boraindane. This latter result is herein confirmed by the reaction of 1,1-difluoro-2,2-dimesityldiborane(4) with tBuNC, which yielded the 2-boraindane compound. The mechanism of the former reaction has been computationally elucidated, and the differences between this route and the pathway to 1-boraindanes is discussed. These reactions further the understanding of the chemistry of the increasingly popular mono-base adducts of diborane(4), demonstrate the versatility of isonitriles in comparison to standard two-electron donors, and elucidate selective routes to boron-containing polycyclics, such as those being proposed as analogues for conventional organic pharmaceuticals. [ABSTRACT FROM AUTHOR]

Pure nanoparticle ammonia borane (NH3BH3, AB) was first prepared through a solvent-free, ambient-temperature gas-phase combination of B2H6 with NH3. The prepared AB nanoparticle exhibits improved dehydrogenation behavior giving 13.6 wt. % H2 at the temperature range of 80-175 °C without severe foaming. Ammonia diborane (NH3BH2(μ-H)BH3, AaDB) is proposed as the intermediate in the reaction of B2H6 with NH3 based on theoretical studies. This method can also be used to prepare pure diammoniate of diborane ([H2B(NH3)2][BH4], DADB) by adjusting the ratio and concentration of B2H6 to NH3. [ABSTRACT FROM AUTHOR]

A combined experimental and quantum chemical study of Group 7 borane, trimetallic triply bridged borylene and boride complexes has been undertaken. Treatment of [{Cp*CoCl}2] (Cp*=1,2,3,4,5-pentamethylcyclopentadienyl) with LiBH4 ⋅thf at −78 °C, followed by room-temperature reaction with three equivalents of [Mn2(CO)10] yielded a manganese hexahydridodiborate compound [{(OC)4Mn}(η6-B2H6){Mn(CO)3}2(μ-H)] ( 1) and a triply bridged borylene complex [(μ3-BH)(Cp*Co)2(μ-CO)(μ-H)2MnH(CO)3] ( 2). In a similar fashion, [Re2(CO)10] generated [(μ3-BH)(Cp*Co)2(μ-CO)(μ-H)2ReH(CO)3] ( 3) and [(μ3-BH)(Cp*Co)2(μ-CO)2(μ-H)Co(CO)3] ( 4) in modest yields. In contrast, [Ru3(CO)12] under similar reaction conditions yielded a heterometallic semi-interstitial boride cluster [(Cp*Co)(μ-H)3Ru3(CO)9B] ( 5). The solid-state X-ray structure of compound 1 shows a significantly shorter boron-boron bond length. The detailed spectroscopic data of 1 and the unusual structural and bonding features have been described. All the complexes have been characterized by using 1H, 11B, 13C NMR spectroscopy, mass spectrometry, and X-ray diffraction analysis. The DFT computations were used to shed light on the bonding and electronic structures of these new compounds. The study reveals a dominant BHMn, a weak BBMn interaction, and an enhanced BB bonding in 1. [ABSTRACT FROM AUTHOR]

Herein, we analyse the catalytic boron-boron dehydrocoupling reaction that leads from the base-stabilised diborane(6) [H2B(hpp)]2 (hpp=1,3,4,6,7,8-hexahydro-2 H-pyrimido[1,2- a]pyrimidinate) to the base-stabilised diborane(4) [H2B(hpp)]2. A number of potential transition-metal precatalysts was studied, including transition-metal complexes of the product diborane(4). The synthesis and structural characterisation of two further examples of such complexes is presented. The best results for the dehydrocoupling reactions were obtained with precatalysts of Group 9 metals in the oxidation state of +I. The active catalyst is formed in situ through a multistep process that involves reduction of the precatalyst by the substrate [H2B(hpp)]2, and mechanistic investigations indicate that both heterogeneous and (slower) homogeneous reaction pathways play a role in the dehydrocoupling reaction. In addition, hydride abstraction from [H2B(hpp)]2 and related diboranes is analysed and the possibility for subsequent deprotonation is discussed by probing the protic character of the cationic boron-hydrogen compounds with NMR spectroscopic analysis. [ABSTRACT FROM AUTHOR]

The diboran(4)yl trans-[( iPr3P)2Pt(Br){B(NMe2)B(NMe2)Br}] ( 1) is readily converted into its cis-bisboryl analogues 2 and 3 by reaction with the chelating bisphosphines 1,2-bis(dicyclohexylphosphino)ethane (dcpe) and 1,1-bis(dicyclohexylphosphino)methane (dcpm), respectively. A plausible mechanism of this transformation consists of a sequence of reductive diborane(4) elimination and subsequent reoxidative addition of its BB bond to the low-valent platinum centers. Thus, the forced cis configuration of the phosphine ligands induces a change in the preferred reaction site of the diborane(4) with respect to oxidative addition. The reactions proceed with high selectivities, and the cis-bisboryl complexes 2 and 3 were isolated in moderate yields (55 and 46 %). Moreover, their identity was clearly verified by NMR spectroscopy and X-ray diffraction studies. [ABSTRACT FROM AUTHOR]

The coordination chemistry of the doubly base-stabilised diborane(4), [HB(hpp)]2 (hpp=1,3,4,6,7,8-hexahydro-2 H-pyrimido-[1,2- a]pyrimidinate), was extended by the synthesis of new late transition-metal complexes containing CuI and RhI fragments. A detailed experimental study was conducted and quantum-chemical calculations on the metal-ligand bonding interactions for [HB(hpp)]2 complexes of Group 6, 9, 11 and 12 metals revealed the dominant BHM interactions in the case of early transition-metal fragments, whereas the BBM bonding prevails in the case of the late d-block compounds. These findings support the experimental results as reflected by the IR and NMR spectroscopic parameters of the investigated compounds. DFT calculations on [MeB(hpp)]2 and model reactions between [B2H4 ⋅2NMe3] and [Rh(μ-Cl)(C2H4)2] showed that the bicyclic guanidinate allows in principle for an oxidative addition of the BB bond. However, the formation of σ-complexes is thermodynamically favoured. The results point to the selective BH or BB bond-activation of diborane compounds by complexation, depending on the chosen transition-metal fragment. [ABSTRACT FROM AUTHOR]

Ammonium aminodiboranate ([NH4][BH3NH2BH3]) is a long-sought isomer of diammoniate of diborane ([NH3BH2NH3][BH4]) and ammonia borane (NH3BH3) dimer. Our results show that [NH4][BH3NH2BH3] is stable in tetrahydrofuran at -18 °C and decomposes rapidly to NH3BH2NH2BH3 and H2 at elevated temperatures. The decomposition pathway is dictated by the dihydrogen bonding between Hδ+ on NH4+ and Hδ- on BH3, as confirmed by theoretical calculations. This is in contrast to the interconversion between [NH3BH2NH3][BH4] and (NH3BH3)2, although all three have dihydrogen bonds and the same stoichiometry. [ABSTRACT FROM AUTHOR]

Ammonium aminodiboranate ([NH4][BH3NH2BH3]) is a long-sought isomer of diammoniate of diborane ([NH3BH2NH3][BH4]) and ammonia borane (NH3BH3) dimer. Our results show that [NH4][BH3NH2BH3] is stable in tetrahydrofuran at −18 °C and decomposes rapidly to NH3BH2NH2BH3 and H2 at elevated temperatures. The decomposition pathway is dictated by the dihydrogen bonding between Hδ+ on NH4+ and Hδ− on BH3, as confirmed by theoretical calculations. This is in contrast to the interconversion between [NH3BH2NH3][BH4] and (NH3BH3)2, although all three have dihydrogen bonds and the same stoichiometry. [ABSTRACT FROM AUTHOR]