PC‐Activated Bimetallic Rhodium Xantphos Complexes: Formation and Catalytic Dehydrocoupling of Amine–Boranes

Johnson, Heather C.; Weller, Andrew S.

doi:10.1002/anie.201504073

Cited by 43 publications

(19 citation statements)

References 49 publications

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“…That dimeric 12 is an active catalyst or precatalyst for amine–borane dehydrogenation has resonance with previous reports of dimeric {Rh(L 2 )} 2 being implicated in dehydrocoupling of acyclic amine–boranes, [19, 58, 70, 71] although in some systems dimers have been discounted on the basis of computational analysis. [49] The likely involvement of potential dimer/monomer equilibira during catalysis using 12 as a precursor was probed using the method of initial rates, monitoring over the first 5% of turnover in the pseudo zero–order regime of catalysis (Figure 5).…”

Section: Resultssupporting

confidence: 53%

The Synthesis, Characterization and Dehydrogenation of Sigma‐Complexes of BN‐Cyclohexanes

Kumar

Ishibashi

Hooper

et al. 2015

Chemistry A European J

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The coordination chemistry of the 1,2‐BN‐cyclohexanes 2,2‐R2‐1,2‐B,N‐C4H10 (R2=HH, MeH, Me2) with Ir and Rh metal fragments has been studied. This led to the solution (NMR spectroscopy) and solid‐state (X‐ray diffraction) characterization of [Ir(PCy3)2(H)2(η2η2‐H2BNR2C4H8)][BArF 4] (NR2=NH2, NMeH) and [Rh(iPr2PCH2CH2CH2PiPr2)(η2η2‐H2BNR2C4H8)][BArF 4] (NR2=NH2, NMeH, NMe2). For NR2=NH2 subsequent metal‐promoted, dehydrocoupling shows the eventual formation of the cyclic tricyclic borazine [BNC4H8]3, via amino‐borane and, tentatively characterized using DFT/GIAO chemical shift calculations, cycloborazane intermediates. For NR2=NMeH the final product is the cyclic amino‐borane HBNMeC4H8. The mechanism of dehydrogenation of 2,2‐H,Me‐1,2‐B,N‐C4H10 using the {Rh(iPr2PCH2CH2CH2PiPr2)}+ catalyst has been probed. Catalytic experiments indicate the rapid formation of a dimeric species, [Rh2(iPr2PCH2CH2CH2PiPr2)2H5][BArF 4]. Using the initial rate method starting from this dimer, a first‐order relationship to [amine‐borane], but half‐order to [Rh] is established, which is suggested to be due to a rapid dimer–monomer equilibrium operating.

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Section: Resultssupporting

confidence: 53%

The Synthesis, Characterization and Dehydrogenation of Sigma‐Complexes of BN‐Cyclohexanes

Kumar

Ishibashi

Hooper

et al. 2015

Chemistry A European J

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“…We provide mechanistic evidence for formation of the complex from a monometallic precursor, and show that such dimeric amino‐borane species may be important in dehydropolymerization pathways. This report builds upon previous observations that indirectly implicate bimetallic motifs during catalysis …”

Section: Methodssupporting

confidence: 73%

“…Thus, it is likely that similar active species are present in THF or 1,2‐F 2 C 6 H 4 . The lack of induction period is in direct contrast to xantphos‐based rhodium catalysts, which show induction periods for H 3 B⋅NMeH 2 dehydrocoupling in C 6 H 5 F, suggesting that a different kinetics regime or mechanism is in operation.…”

Section: Methodsmentioning

confidence: 77%

The Simplest Amino‐borane H₂B=NH₂ Trapped on a Rhodium Dimer: Pre‐Catalysts for Amine–Borane Dehydropolymerization

et al. 2016

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Abstract:The ]. DFT calculations demonstrate that the amino-borane interacts with the Rh centers through strong Rh-H and Rh-B interactions.Mechanistic investigations show that these dimers can form by ab oronium-mediated route,and are pre-catalysts for amine-borane dehydropolymerization, suggesting ap ossible role for bimetallic motifs in catalysis. Polyamino-boranes ([H2BNRH] n )a re potentially exciting new materials that are isoelectronic with technologically pervasive polyolefins,b ut are chemically distinct because of (dÀ)HBÀNH(d +)p olarization. They are formed by the dehydropolymerization of amine-boranes (H 3 B·NRH 2 ;R= Ho rM e, for example;S cheme 1A), [1] and metal-catalyzed routes to polyamino-boranes offer the potential for fine control over molecular weight and polymer stereochemistry.There is recent evidence that these processes occur at ametal center in which the catalyst needs to perform two roles: 1) formal dehydrogenation of amine-borane to form al atent source of amino-borane (H 2 B=NRH), and 2) subsequent B À Nb ond formation.[2-6] Fors ome systems ac oordination/ insertion mechanism is proposed, although the precise structure of the propagating species is currently unresolved (Scheme 1B). [3,5,6] This is in contrast to olefin polymerization, in which the feedstock (for example,e thene or propene) is already unsaturated, and the active species and propagating mechanisms are well-defined.[7] Ac learer understanding of how the catalyst dehydrogenates amine-borane,t raps intermediate amino-boranes,and promotes B À Nbond-formation, is central to harnessing the full potential of systems that ultimately deliver new well-defined BÀNpolymeric materials on au seful scale.Unlike ethene (H 2 C=CH 2 ), which is stable under ambient conditions,t he isoelectronic amino-borane (H 2 B = NH 2 )h as only been prepared in low temperature matrices and oligomerizes above À150 8 8C. [2,8] Adding steric bulk to the nitrogen atom increases stability,s ot hat, for example,H 2 B=NMeH [9] or H 2 B=N t BuH [10] can be observed as transient species using in situ NMR spectroscopy before they also oligomerize.There are two examples where unstable H 2 B = NH 2 can be trapped by coordination to asingle metal center.These originate after dehydrogenation of aputative s-ammonia borane [11] complex, forming Ru(PCy 3 ) 2 (H) 2 (h 2 -H 2 B=NH 2 ) A [12] and (Cy-PSiP)-Ru(H)(h 2 -H 2 B=NH 2 ) B,Cy-PSiP = k 3 -(Cy 2 PC 6 H 4 ) 2 SiMe).[13]We now report that H 2 B=NH 2 can be trapped by ab imetallic [Rh 2 (R 2 PCH 2 CH 2 CH 2 PR 2 ) 2 ] 2+ fragment to give an ovel bridging amino-borane bonding motif.W ep rovide mechanistic evidence for formation of the complex from amonometallic precursor,and show that such dimeric aminoborane species may be important in dehydropolymerization pathways.T his report builds upon previous observations that indirectly implicate bimetallic motifs during catalysis. [14][15][16]

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“…Inorganic polymers basedo nm ain-group elements other than carbon are of current research interest, [1,2,3] due to their various applications.P olymers consistingo fa lternating elements of groups 13 and 15 are accessible by metal-catalyzed polycon-densation reactions and dehydrocoupling processes. Both pathways are established for poly(aminoborane)s [(RHNBH 2 ) n , R = alkyl, H] and poly(phosphinoborane)s [(RHPBH 2 ) n ,R = aryl].…”

mentioning

confidence: 99%

“…Interestingly,a rsine oxides [14] are wellinvestigated, but there are only af ew examples for arsine sulfides [15] and only one structurally characterized arsine selenide. [16] To gain furtheri nsight into the stabilityo ft he AsÀB bond, we targeted the oxidation of Ph 2 AsBH 2 NMe 3 (2).…”

mentioning

confidence: 99%

The Lewis‐Base‐Stabilized Diphenyl‐Substituted Arsanylborane: A Versatile Building Block for Arsanylborane Oligomers

Hegen

Вировец

Timoshkin

et al. 2018

Chemistry A European J

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The synthesis and properties of the diphenyl-substituted arsanylborane Ph AsBH SMe (1) and Ph AsBH NMe (2) stabilized by a Lewis base (LB) were reported. These compounds were obtained by reaction of KAsPh with IBH -LB (LB=SMe , NMe ). Compounds 1 and 2 were used as starting materials for oligomeric/ polymeric arsinoboranes. The neutral species, H B-Ph AsBH NMe (3) and Br B-Ph AsBH NMe (4), were synthesized by reaction with H B and Br B, respectively. Upon reaction with IBH -LB (LB=SMe , NMe ), the cationic oligomeric group-13/15-based compounds [(Me NBH AsPh BH NMe )]I (5) and [H B(Ph AsBH NMe ) ]I (6) were obtained. All compounds were completely characterized. In addition, the oxidation of Ph AsBH NMe with chalcogens was studied. The sulfur Ph As(S)BH NMe (7 b) and selenium Ph As(Se)BH NMe (7 c) oxidation products were both isolated and fully characterized, whereas the bis(trimethylsilyl)peroxide oxidated arsinoborane Ph As(O)BH NMe (7 a) was not stable enough and could only be characterized in solution. DFT computations supported the decomposition pathway of this compound.

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PC‐Activated Bimetallic Rhodium Xantphos Complexes: Formation and Catalytic Dehydrocoupling of Amine–Boranes

Cited by 43 publications

References 49 publications

The Synthesis, Characterization and Dehydrogenation of Sigma‐Complexes of BN‐Cyclohexanes

The Synthesis, Characterization and Dehydrogenation of Sigma‐Complexes of BN‐Cyclohexanes

The Simplest Amino‐borane H₂B=NH₂ Trapped on a Rhodium Dimer: Pre‐Catalysts for Amine–Borane Dehydropolymerization

The Lewis‐Base‐Stabilized Diphenyl‐Substituted Arsanylborane: A Versatile Building Block for Arsanylborane Oligomers

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PC‐Activated Bimetallic Rhodium Xantphos Complexes: Formation and Catalytic Dehydrocoupling of Amine–Boranes

Cited by 43 publications

References 49 publications

The Synthesis, Characterization and Dehydrogenation of Sigma‐Complexes of BN‐Cyclohexanes

The Synthesis, Characterization and Dehydrogenation of Sigma‐Complexes of BN‐Cyclohexanes

The Simplest Amino‐borane H2B=NH2 Trapped on a Rhodium Dimer: Pre‐Catalysts for Amine–Borane Dehydropolymerization

The Lewis‐Base‐Stabilized Diphenyl‐Substituted Arsanylborane: A Versatile Building Block for Arsanylborane Oligomers

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The Simplest Amino‐borane H₂B=NH₂ Trapped on a Rhodium Dimer: Pre‐Catalysts for Amine–Borane Dehydropolymerization