23884-11-9

Upstream product

• 19624-22-7 pentaborane⁽⁹⁾ 
• 124-40-3 dimethyl amine 
• 26601-80-9 sodium (N,N-dimethylamino)diboranate 
• 60934-33-0 bis(trimethylamine)alane 
• 1630-79-1 tetrakis(dimethylamido)diborane 
• 26602-45-9 {((CH₃)2NH)(C₅H₅N)BH₂}⁽¹⁺⁾*PF₆^(1-)={((CH₃)2NH)(C₅H₅N)BH₂}PF₆ 
• 1073349-09-3 [Rh(P(i-Bu)3)2][B(3,5-C₆H₃(CF₃)2)4] 
• 74-94-2 dimethylamine borane 
• 1073349-19-5 [Rh(P(i-Bu)3)2(η2-(H2BNMe2)2)][B(3,5-C6H3(CF3)2)4] 
• 1333-74-0 hydrogen 
• 21793-61-3 dimethylamine-dimethylaminoborane-borane 
• 68725-14-4 tributylstannyl trifluoromethanesulfonate 
• 21793-62-4 μ-(CH3)N-B2H5*N(CH3)3 
• 23273-02-1 (μ-dimethylamino)diborane 

Downstream Products

• 1838-13-7 dimethylamine borane 
• 593-90-8 trimethylborane 
• 1073349-19-5 [Rh(P(i-Bu)3)2(η2-(H2BNMe2)2)][B(3,5-C6H3(CF3)2)4] 
• 1207163-92-5 [Rh(η2-H2BNMe3)2(PiPr3)2][B(3,5-(CF3)2C6H3)4] 
• 74-94-2 dimethylamine borane 
• 22092-92-8 diisopropopylaminoborane 
• 1456812-37-5 C₂₈H₄₂BN₃ 

Relevant academic research and scientific papers

Mechanistic insights into dehydrocoupling of amine boranes using dinuclear zirconocene complexes

Catalytic dehydrocoupling of H3B·NMe2H using the in situ system Cp2Zr(Cl)(μ-Me3SiC3SiMe3)Zr(Cl)Cp2 (1)/MeLi was studied as a model for previously reported dehydropolymerisation of H3B·NMeH2. NMR and UV-vis spectroscopic monitoring of the precatalyst activation sequence as well as a series of stoichiometric experiments showed that formation of a zirconocene dimethyl complex (2) is not relevant for activation of the precatalyst. Instead, deprotonation of H3B·NMe2H and reaction of thus formed Li[NMe2BH3] is proposed to result in the formation of Zr amidoborane and hydride species. DFT analysis using such complexes as active species showed a pathway for formation of H2 and H2BNMe2. 1H NMR spectroscopic monitoring and stoichiometric control experiments revealed the formation of unusual diamagnetic dinuclear complexes Cp2Zr(C2SiMe3)(μ-R)ZrCp2 (R = CH2SiMe3, 7; R = H, 9) formed by activation of the allenediide unit of the precatalyst 1. Such species can be regarded as rare single-component catalysts for the dehydrocoupling of amine boranes. This journal is

Metal-ligand cooperative κ1-N-pyrazolate Cp*RhIII-catalysts for dehydrogenation of dimethylamine-borane at room temperature

3,5-Dimethylpyrazole (Pz*H) in well-defined Cp*RhIII(Cp* = 1,2,3,4,5-pentamethylcyclopentadienyl) complexes, or as an additive to [Cp*RhCl2]2enhances catalytic activity in the dehydrogenation of dimethylamine-borane (DMAB) at room-temperature. Mechanistic studies indicate that the Lewis acidic RhIII-centre and dangling N-atom of the Pz* fragment operate cooperatively in accepting a hydride and proton from DMAB, respectively, leading directly to dimethylamino-borane and a RhIII-H complex. The rate limiting step involves protonation of the RhIII-H by the proximal NH fragment of the Pz*H moiety.

Impact of the novel Z-acceptor ligand bis{(ortho-diphenylphosphino)phenyl}zinc (ZnPhos) on the formation and reactivity of low-coordinate Ru(0) centers

The preparation and reactivity with H2 of two Ru complexes of the novel ZnPhos ligand (ZnPhos = Zn(o-C6H4PPh2)2) are described. Ru(ZnPhos)(CO)3 (2) and Ru(ZnPhos)(IMe4)2 (4; IMe4 = 1,3,4,5-tetramethylimidazol-2-ylidene) are formed directly from the reaction of Ru(PPh3)(C6H4PPh2)2(ZnMe)2 (1) or Ru(PPh3)3HCl/LiCH2TMS/ZnMe2 with CO and IMe4, respectively. Structural and electronic structure analyses characterize both 2 and 4 as Ru(0) species in which Ru donates to the Z-type Zn center of the ZnPhos ligand; in 2, Ru adopts an octahedral coordination, while 4 displays square-pyramidal coordination with Zn in the axial position. Under photolytic conditions, 2 loses CO to give Ru(ZnPhos)(CO)2 that then adds H2 over the Ru-Zn bond to form Ru(ZnPhos)(CO)2(μ-H)2 (3). In contrast, 4 reacts directly with H2 to set up an equilibrium with Ru(ZnPhos)(IMe4)2H2 (5), the product of oxidative addition at the Ru center. DFT calculations rationalize these different outcomes in terms of the energies of the square-pyramidal Ru(ZnPhos)L2 intermediates in which Zn sits in a basal site: for L = CO, this is readily accessed and allows H2 to add across the Ru-Zn bond, but for L = IMe4, this species is kinetically inaccessible and reaction can only occur at the Ru center. This difference is related to the strong π-acceptor ability of CO compared to IMe4. Steric effects associated with the larger IMe4 ligands are not significant. Species 4 can be considered as a Ru(0)L4 species that is stabilized by the Ru→Zn interaction. As such, it is a rare example of a stable Ru(0)L4 species devoid of strong π-acceptor ligands.

Dehydropolymerisation of Methylamine Borane and an N-Substituted Primary Amine Borane Using a PNP Fe Catalyst

Dehydropolymerisation of methylamine borane (H3B?NMeH2) using the well-known iron amido complex [(PNP)Fe(H)(CO)] (PNP=N(CH2CH2PiPr2)2) (1) gives poly(aminoborane)s by a chain-growth mechanism. In toluene, rapid dehydrogenation of H3B?NMeH2 following first-order behaviour as a limiting case of a more general underlying Michaelis–Menten kinetics is observed, forming aminoborane H2B=NMeH, which selectively couples to give high-molecular-weight poly(aminoborane)s (H2BNMeH)n and only traces of borazine (HBNMe)3 by depolymerisation after full conversion. Based on a series of comparative experiments using structurally related Fe catalysts and dimethylamine borane (H3B?NMe2H) polymer formation is proposed to occur by nucleophilic chain growth as reported earlier computationally and experimentally. A silyl functionalised primary borane H3B?N(CH2SiMe3)H2 was studied in homo- and co-dehydropolymerisation reactions to give the first examples for Si containing poly(aminoborane)s.

Stable BH3adducts to rhodium amide bonds

Rh(I) diolefin amides, [Rh(trop2N)(L)] (trop2N?=?bis(5H-dibenzo[a,d]cyclohepten-5-yl)amide), form the corresponding hydrido amine species, [RhH(trop2NH)(L)], by reaction with Me2HN-BH3(DMAB). Both amide and amine complexes are active dehydrocoupling catalysts, forming the monomer [Me2N?=?BH2], the linear [Me2NHBH2NMe2BH3] and the cyclic dimer [Me2BNH2]2. Good catalytic activity was observed especially for complexes which contain a metal hydride unit, Rh–H, in a co-planar cis-arrangement with respect to the N-H unit and for those bearing an N-heterocyclic carbene ligand (IMe) in trans-position to the active basic site of the ligand. Four-membered Rh–N–B–H metallacycles [Rh{(μ-H)BH2}(Ntrop2)(L)] (L?=?PPh3, IMe) were isolated by direct reaction of the amide complex with BH3(THF). These stable species are not active in the dehydrogenation of DMAB. Their isolation and lack of reactivity gives some indication for a possible catalyst deactivation. This observation is consistent with a mechanism in which the unprotected amine or amide ligand is essential for N–H and B–H bond cleavage.

Catalytic Dehydrocoupling of Amine-Boranes using Cationic Zirconium(IV)-Phosphine Frustrated Lewis Pairs

A series of novel, intramolecular Zr(IV)/P frustrated Lewis pairs (FLPs) based on cationic zirconocene fragments with a variety of ancillary cyclopentadienyl and 2-phosphinoaryloxide (-O(C6H4)PR2, R = tBu and 3,5-CF3-(C6H3)) ligands are reported and their activity as catalysts for the dehydrocoupling of dimethylamine-borane (Me2NH·BH3) assessed. The FLP system [(C9H7)2ZrO(C6H4)PtBu2][B(C6F5)4] is shown to give unprecedented turnover frequencies (TOF) for a catalyst based on a group 4 metal (TOF ≥ 600 h-1), while also proving to be the most efficient FLP catalyst reported to date. The mechanism of this reaction has been probed using analogous intermolecular Zr(IV)/P FLPs, permitting deconvolution of the reactions taking place at both the Lewis acidic and basic sites. Elucidation of this mechanism revealed an interesting cooperative two-cycle process where one cycle is FLP mediated and the other, a redistribution of a linear diborazane intermediate, relies solely on the presence of a Zr(IV) Lewis acid.

Catalysis and Mechanism of H2 Release from Amine-Boranes by Diiron Complexes

Studies focused on the dehydrogenation of amine-borane by diiron complexes that serve as well-characterized rudimentary models of the diiron subsite in [FeFe]-hydrogenase are reported. Complexes of formulation (μ-SCH2XCH2S)[Fe(CO)su

Titanocene(iii) complexes with 2-phosphinoaryloxide ligands for the catalytic dehydrogenation of dimethylamine borane

A study of the dehydrogenation of dimethylamine borane using different titanocene(iii) complexes with 2-phosphinoaryloxide ligands is presented. Complexes Cp2Ti(κ2-O, P-O-C6H4-PR2) (3a: R = i-Pr, 3b: R = Ph) (Cp = η5-cyclopentadienyl) and Cp?2Ti(κ1-O-O-C6H4-PR2) (5a: R = i-Pr, 5b: R = Ph) (Cp? = η5-pentamethylcyclopentadienyl) were prepared by reactions of the 2-phosphinophenol ligand with different titanocene sources and fully characterised. Their catalytic activity depends on the steric influence of the cyclopentadienyl ligand, the coordination mode of the 2-phosphinoaryloxide ligand and on the used solvent. Complex 3a showed a turnover number of 43.2 in the neat substrate after 24 hours. EPR investigations were used to elucidate the fate of the Ti(iii) catalyst.

B-Methylated Amine-Boranes: Substituent Redistribution, Catalytic Dehydrogenation, and Facile Metal-Free Hydrogen Transfer Reactions

Although the dehydrogenation chemistry of amine-boranes substituted at nitrogen has attracted considerable attention, much less is known about the reactivity of their B-substituted analogues. When the B-methylated amine-borane adducts, RR'NH·BH2Me (1a: R = R' = H; 1b: R = Me, R' = H; 1c: R = R' = Me; 1d: R = R' = iPr), were heated to 70 °C in solution (THF or toluene), redistribution reactions were observed involving the apparent scrambling of the methyl and hydrogen substituents on boron to afford a mixture of the species RR'NH·BH3-xMex (x = 0-3). These reactions were postulated to arise via amine-borane dissociation followed by the reversible formation of diborane intermediates and adduct reformation. Dehydrocoupling of 1a-1d with Rh(I), Ir(III), and Ni(0) precatalysts in THF at 20 °C resulted in an array of products, including aminoborane RR'N=BHMe, cyclic diborazane [RR'N-BHMe]2, and borazine [RN-BMe]3 based on analysis by in situ 11B NMR spectroscopy, with peak assignments further supported by density functional theory (DFT) calculations. Significantly, very rapid, metal-free hydrogen transfer between 1a and the monomeric aminoborane, iPr2N=BH2, to yield iPr2NH·BH3 (together with dehydrogenation products derived from 1a) was complete within only 10 min at 20 °C in THF, substantially faster than for the N-substituted analogue MeNH2·BH3. DFT calculations revealed that the hydrogen transfer proceeded via a concerted mechanism through a cyclic six-membered transition state analogous to that previously reported for the reaction of the N-dimethyl species Me2NH·BH3 and iPr2N=BH2. However, as a result of the presence of an electron donating methyl substituent on boron rather than on nitrogen, the process was more thermodynamically favorable and the activation energy barrier was reduced.

Iron-catalyzed dehydrocoupling/dehydrogenation of amine-boranes

The readily available iron carbonyl complexes, [CpFe(CO)2] 2 (1) and CpFe(CO)2I (2) (Cp = η-C5H 5), were found to be efficient precatalysts for the dehydrocoupling/dehydrogenation of the amine-borane Me2NH· BH3 (3) to afford the cyclodiborazane [Me2N-BH 2]2 (4), upon UV photoirradiation at ambient temperature. In situ analysis of the reaction mixtures by 11B NMR spectroscopy indicated that different two-step mechanisms operate in each case. Thus, precatalyst 1 dehydrocoupled 3 via the aminoborane Me2N=BH 2 (5) which then cyclodimerized to give 4 via an off-metal process. In contrast, the reaction with precatalyst 2 proceeded via Me 2NH-BH2-NMe2-BH3 (6) as the key intermediate, affording 4 as the final product after a second metal-mediated step. The related complex Cp2Fe2(CO)3(MeCN) (7), formed by photoirradiation of 1 in MeCN, was found to be a substantially more active dehydrocoupling catalyst and not to require photoactivation, but otherwise operated via a two-step mechanism analogous to that for 1. Significantly, detailed mechanistic studies indicated that the active catalyst generated from precatalyst 7 was heterogeneous in nature and consisted of small iron nanoparticles (≤10 nm). Although more difficult to study, a similar process is highly likely to operate for precatalyst 1 under photoirradiation conditions. In contrast to the cases of 7 and 1, analogous experimental studies for the case of photoactivated Fe precatalyst 2 suggested that the active catalyst formed in this case was homogeneous. Experimental and computational DFT studies were used to explore the catalytic cycle which appears to involve amine-borane ligated [CpFe(CO)]+ as a key intermediate.