Polyphosphinoborane Block Copolymer Synthesis Using Catalytic Reversible Chain‐Transfer Dehydropolymerization

Race, James J.; Heyam, Alex; Wiebe, Matthew A.; Hernandez, J Diego-Garcia; Ellis, Charlotte; Lei, Shixing; Manners, Ian; Weller, Andrew S.

doi:10.1002/anie.202216106

Cited by 5 publications

(1 citation statement)

References 58 publications

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“…The reasons behind the remarkable selectivity for the eee isomer of N,N,N ‐trimethylcyclotriborazane remain unresolved, especially as the stereochemistry (i. e. tacticity) of the parent polyaminoboranes currently remains opaque – although they are likely atactic, similar to that observed for closely related polyphosphinoboranes. [ 68 , 69 ] Our tentative proposal is that deprotonation of an end‐chain ammonium group [28] forms a reactive amido−boryl unit, that then undergoes main‐chain back‐biting in the atactic polymer to form a mixture of eee and eea isomers of [H 2 BNMeH] 3 (Scheme 6 ). A rapid isomerization then occurs.…”

Section: Resultsmentioning

confidence: 99%

Dehydropolymerization of Amine−Boranes using Bis(imino)pyridine Rhodium Pre‐Catalysis: σ‐Amine−Borane Complexes, Nanoparticles, and Low Residual‐Metal BN−Polymers that can be Chemically Repurposed

Cross,

Brodie,

Crivoi

et al. 2023

Chemistry A European J

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The sigma amine‐borane complexes [Rh(L1)(h2:h2H3B·NRH2)][OTf] (L1 = 2,6‐bis‐[1‐(2,6‐diisopropylphenylimino)ethyl]pyridine, R = Me, Et, nPr) are described, alongside [Rh(L1)(NMeH2)][OTf]. Using R = Me as the pre‐catalyst (1 mol%) the dehydropolymerization of H3B·NMeH2 gives [H2BNMeH]n selectively. Added NMeH2, or the direct use of [Rh(L1)(NMeH2)][OTf], is required for initiation of catalysis, which is suggested to operate through formation of a neutral hydride complex, Rh(L1)H. The formation of small (1‐5 nm) nanoparticles is observed during catalysis, but studies are ambiguous as to whether the catalysis is solely nanoparticle promoted or if there is a molecular homogeneous component. [Rh(L1)(NMeH2)][OTf] is shown to operate at 0.025 mol% loadings on a 2 g scale to give polyaminoborane [H2BNMeH]n [Mn = 30,900 g/mol, Ð = 1.8] that can be purified to a low residual [Rh] (6 µg/g). Addition of Na[N(SiMe3)2] to [H2BNMeH]n results in selective depolymerization to form the eee‐isomer of N,N,N‐trimethylborazane [H2BNMeH]3: the chemical repurposing of a main‐group polymer.

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Section: Resultsmentioning

confidence: 99%

Dehydropolymerization of Amine−Boranes using Bis(imino)pyridine Rhodium Pre‐Catalysis: σ‐Amine−Borane Complexes, Nanoparticles, and Low Residual‐Metal BN−Polymers that can be Chemically Repurposed

Cross,

Brodie,

Crivoi

et al. 2023

Chemistry A European J

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Polyphosphinoborane Block Copolymer Synthesis Using Catalytic Reversible Chain‐Transfer Dehydropolymerization

et al. 2022

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An amphiphilic block copolymer of polyphosphinoborane has been prepared by a mechanism-led strategy of the sequential catalytic dehydropolymerization of precursor monomers, H 3 B • PRH 2 (R = Ph, nhexyl), using the simple pre-catalyst [Rh-(Ph 2 PCH 2 CH 2 PPh 2 ) 2 ]Cl. Speciation, mechanism and polymer chain growth studies support a step-growth process where reversible chain transfer occurs, i.e. H 3 B • PRH 2 / oligomer/polymer can all coordinate with, and be activated by, the catalyst. Block copolymer [H 2 BPPhH] 110 -b-[H 2 BP(n-hexyl)H] 11 can be synthesized and self-assembles in solution to form either rod-like micelles or vesicles depending on solvent polarity.

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B‐P Coupling: Metal Stabilized Phosphinoborate Complexes

Gayen,

Shyamal,

Mohapatra

et al. 2023

Chemistry A European J

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In an effort to establish B‐P coupling reactions without the use of phosphine‐borane dehydrocoupling agent, we have developed a new synthetic methodology employing group 8 metal σ‐borate complex [{κ3‐H,S,S′‐BH2L2}Ru{κ3‐H,H,S‐BH3L}] (L=NC5H4S), 1. Treatment of 1 with chlorodiphenyl phosphine (PPh2Cl) yielded 1,5‐P,S chelated Ru‐dihydridoborate species [PPh2H{κ3‐H,H,S‐BH(OH)L}Ru{κ2‐P,S‐(Ph2P)BH2L}], 2. The insertion of phosphine moiety (PPh2) by the cleavage of 3c–2e σ(Ru…H‐B) bonding interaction led to the formation of B‐P bond. The κ2‐P,S chelated six‐membered ring adopted a boat conformation in complex 2. The heterocycle is made of all different atoms, which is one of the rarest examples of heteroatomic ring systems. Theoretical outcomes demonstrated the electronic insight of B‐P coupling and stabilization through transition metal. In order to explore an alternate route of B‐P bond formation, we have further explored the reaction of 1 and Ru‐bis(dihydridoborate) complex, 5 with secondary phosphine oxide (SPO). Although, thermolysis of 1 with diphenylphosphine oxide yielded analogous σ‐borate complex 3, the similar reaction of 5 at room temperature led to the formation of novel phosphinous(III) acid incorporated Ru(σ‐borate)(dihydridoborate) complex, 6. In a similar fashion, the reaction of 5 with phosphite ligand generated Ru(σ‐borate)(dihydridoborate) complex, 7, which is analogous to 6.

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Polyphosphinoborane Block Copolymer Synthesis Using Catalytic Reversible Chain‐Transfer Dehydropolymerization

Cited by 5 publications

References 58 publications

Dehydropolymerization of Amine−Boranes using Bis(imino)pyridine Rhodium Pre‐Catalysis: σ‐Amine−Borane Complexes, Nanoparticles, and Low Residual‐Metal BN−Polymers that can be Chemically Repurposed

Dehydropolymerization of Amine−Boranes using Bis(imino)pyridine Rhodium Pre‐Catalysis: σ‐Amine−Borane Complexes, Nanoparticles, and Low Residual‐Metal BN−Polymers that can be Chemically Repurposed

Polyphosphinoborane Block Copolymer Synthesis Using Catalytic Reversible Chain‐Transfer Dehydropolymerization

B‐P Coupling: Metal Stabilized Phosphinoborate Complexes

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