Squeezing Bi: PNP and P<sub>2</sub>N<sub>3</sub> pincer complexes of bismuth

Kindervater, Marcus B.; Hynes, Toren; Marczenko, Katherine; Chitnis, Saurabh S.

doi:10.1039/d0dt01413c

Cited by 17 publications

(16 citation statements)

References 64 publications

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“…There has been an increased interest in the chemistry of compounds containing the heavy pnictogen elements (Sb and Bi) due to the development of redox-active or Lewis acidic molecules that mediate key organic transformations. − However, Sb and Bi exhibit stark differences in bonding compared to the lighter group 15 elements (P and As), and thus, structurally analogous compounds tend to be substantially more reactive. These differences in reactivity can be attributed to several factors: the increase in covalent and van der Waals radii moving from N to Bi, , a change in the radial extension between the s and p orbitals moving down the group, and the increase in the one-electron ionization energies .…”

Section: Introductionmentioning

confidence: 99%

Lewis Superacidic Heavy Pnictaalkene Cations: Comparative Assessment of Carbodicarbene-Stibenium and Carbodicarbene-Bismuthenium Ions

et al. 2022

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We report a comprehensive assessment of Lewis acidity for a series of carbone-stibenium and -bismuthenium ions using the Gutmann–Beckett (GB) method. These new antimony and bismuth cations have been synthesized by halide abstractions from (CDC)PnBr3 and [(pyCDC)PnBr2][Br] (CDC = carbodicarbene; Pn = Sb or Bi; py = pyridyl). The reaction of (CDC)SbBr3 (1) with one or two equivalents of AgNTf2 (NTf2 = bis(trifluoromethanesulfonyl)imide) or AgSbF6 gives stibaalkene mono- and dications of the form [(CDC)SbBr3–n ][A] n (2–4; n = 1,2; A = NTf2 or SbF6). The stibaalkene trication [(CDC)2Sb][NTf2]3 (5) was also isolated and collectively these molecules fill the gap among the series of cationic pnictaalkenes. The Sb cations are compared to the related CDC-bismaalkene complexes 6–9. With the goal of preparing highly Lewis acidic compounds, a tridentate bis(pyridine)carbodicarbene (pyCDC) was used as a ligand to access [(pyCDC)PnBr2][Br] (10, 12) and trications [(pyCDC)Pn][NTf2]3 (Pn = Sb (11), Bi (13)), forgoing the need for a second CDC as used in the synthesis of 5. The bonding situation in these complexes is elucidated through electron density and energy decomposition analyses in combination with natural orbital for chemical valence theory. In each complex, there exists a CDC–Pn double bonding interaction, consisting of a strong σ-bond and a weaker π-bond, whereby the π-bond gradually strengthens with the increase in cationic charge in the complex. Notably, [(CDC)SbBr][NTf2]2 (4) has an acceptor number (AN) (84) that is comparable to quintessential Lewis acids such as BF3, and tricationic pnictaalkene complexes 11 and 13 exhibit strong Lewis acidity with ANs of 109 (Pn = Sb) and 84 (Pn = Bi), respectively, which are among the highest values reported for any antimony or bismuth cation. Moreover, the calculated fluoride ion affinities (FIAs) for 11 and 13 are 99.8 and 94.3 kcal/mol, respectively, which are larger than that of SbF5 (85.1 kcal/mol), which suggest that these cations are Lewis superacids.

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Section: Introductionmentioning

confidence: 99%

Lewis Superacidic Heavy Pnictaalkene Cations: Comparative Assessment of Carbodicarbene-Stibenium and Carbodicarbene-Bismuthenium Ions

et al. 2022

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“…One of the Me groups in the ketimines converted into a CH 2 , resulting in a reduction of the C–C length in C7–C8 [1.3552(16) Å], consistent with a double bond . The longer C7–N1 and Bi1–N2 distances [1.3832(15) and 2.6117(9) Å] compared to C9–N2 and Bi1–N1 [1.2848(14) and 2.2319(9) Å] also manifest the presence of an amido bond in one of the arms of the pincer . Interestingly, the OH points to a phenyl group of a m -Tp with a short H–phenyl centroid distance of 2.622 Å, indicative of a weak OH···π interaction .…”

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confidence: 99%

Catalytic Activation of N₂O at a Low-Valent Bismuth Redox Platform

et al. 2020

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Herein we present the catalytic activation of N 2 O at a Bi I ⇄Bi III redox platform. The activation of such a kinetically inert molecule was achieved by the use of bismuthinidene catalysts, aided by HBpin as reducing agent. The protocol features remarkably mild conditions (25 °C, 1 bar N 2 O), together with high turnover numbers (TON, up to 6700) and turnover frequencies (TOF). Analysis of the elementary steps enabled structural characterization of catalytically relevant intermediates after O-insertion, namely a rare arylbismuth oxo dimer and a unique monomeric arylbismuth hydroxide. This protocol represents a distinctive example of a main-group redox cycling for the catalytic activation of N 2 O.

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“…In a Coulombic approach, cationic charge was used to boost electrophilicity by using a bisphosphinimino-amide ligand instead of a triamide ligand. 35 Analogous bismuth cations and polycations have been reported to be strong Lewis acids with applications in catalysis. [36][37][38][39][40][41][42] In a mesomeric tuning approach, one of the adjacent π-donor groups was removed to boost the metal-centred electrophilicity by precluding one of the three N(lp)→Bi(6p) interactions.…”

Section: Introductionmentioning

confidence: 99%

Planar Bismuth Triamides: A Tunable Platform for Main Group Lewis Acidity and Polymerization Catalysis

Hannah

McCarvell

Kirsch

et al. 2022

Preprint

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Geometric deformation in main group compounds can be used to elicit unique properties including strong Lewis acidity. Here we report on a family of planar bismuth (III) complexes (c.f. typically pyramidal structure for such compounds), which show a geometric Lewis acidity that can be further tuned by varying the steric and electronic features of the triamide ligand employed. The structural dynamism of the planar bismuth complexes was probed in both the solid and solution phase, revealing at least three distinct modes of intermolecular association. A modified Gutmann-Beckett method was used to assess their electrophilicity by employing trimethylphosphine sulfide in addition to triethylphosphine oxide as probes, providing insights into the preference for binding hard or soft substrates. Experimental binding studies were complemented by a computational assessment of the affinities and dissection of the latter into their intrinsic bond strength and deformation energy components. The results show comparable Lewis acidity to triarylboranes, with the added ability to bind two bases simultaneously and reduced discrimination against soft substrates. We also study the catalytic efficacy of these complexes in the ring opening polymerization of cyclic esters ε-caprolactone and rac-lactide. The polymers obtained are in the ultra-high molecular weight regime and show excellent dispersity values. The complexes retain their performance under industrially relevant conditions suggesting they may be useful as less toxic alternatives to tin catalysts in the production of medical grade materials. Collectively, these results establish planar bismuth complexes as not only a novel neutral platform for main group Lewis acidity, but also a potentially valuable one for catalysis.

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Squeezing Bi: PNP and P₂N₃ pincer complexes of bismuth

Abstract: Stable neutral and highly-reactive cationic Bi complexes featuring NNN and PNP pincer ligands are debuted.

Cited by 17 publications

References 64 publications

Lewis Superacidic Heavy Pnictaalkene Cations: Comparative Assessment of Carbodicarbene-Stibenium and Carbodicarbene-Bismuthenium Ions

Lewis Superacidic Heavy Pnictaalkene Cations: Comparative Assessment of Carbodicarbene-Stibenium and Carbodicarbene-Bismuthenium Ions

Catalytic Activation of N₂O at a Low-Valent Bismuth Redox Platform

Planar Bismuth Triamides: A Tunable Platform for Main Group Lewis Acidity and Polymerization Catalysis

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Squeezing Bi: PNP and P2N3 pincer complexes of bismuth

Abstract: Stable neutral and highly-reactive cationic Bi complexes featuring NNN and PNP pincer ligands are debuted.

Cited by 17 publications

References 64 publications

Lewis Superacidic Heavy Pnictaalkene Cations: Comparative Assessment of Carbodicarbene-Stibenium and Carbodicarbene-Bismuthenium Ions

Lewis Superacidic Heavy Pnictaalkene Cations: Comparative Assessment of Carbodicarbene-Stibenium and Carbodicarbene-Bismuthenium Ions

Catalytic Activation of N2O at a Low-Valent Bismuth Redox Platform

Planar Bismuth Triamides: A Tunable Platform for Main Group Lewis Acidity and Polymerization Catalysis

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Squeezing Bi: PNP and P₂N₃ pincer complexes of bismuth

Catalytic Activation of N₂O at a Low-Valent Bismuth Redox Platform