The Addition of a Cyclopropyl Alkyne to an Asymmetrically-Substituted Disilene: A Mechanistic Study

Henry, Andrew T.; Bourque, Jeremy L.; Vacirca, Isabell; Scheschkewitz, David; Baines, Kim M.

doi:10.1021/acs.organomet.9b00054

Cited by 9 publications

(3 citation statements)

References 38 publications

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“…With Int1 Y , TS2 Y , and Int2 Y all showing significant singlet biradical character, the mechanism of formation of Int3 Y differs from that computed for the cycloaddition of terminal alkynes to doubly NHC- or phosphine-stabilized diborenes, which proceeds via a zwitterionic closed-shell intermediate. In the present case the biradical intermediates and transition states are stabilized by the presence of the π-accepting CAAC ligands. , A similar radical mechanism has been confirmed experimentally for the [2 + 2] cycloaddition of alkynes to disilenes and digermenes. ,,− …”

Section: Resultssupporting

confidence: 79%

Hybrid Inorganic–Organic Cross-Metathesis between Diborenes and Acetylene

et al. 2021

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The ruthenium-catalyzed cross-metathesis of alkenes and alkynes, which splits the alkene CC double bond and couples one-half to each carbon of the alkyne CC triple bond, is one of the most efficient tools for the synthesis of 1,3-dienes, with wide-ranging applications, including pharmaceutical and polymer chemistry. In contrast, inorganic main-group metathesis reactions are restricted to a handful of examples of heavier p-block multiple bonds (PP, GeGe, and EE, E = Ge, Sn, Pb). We now report the first examples of thermally induced, transition-metal-free cross-metathesis between an organic alkyne and inorganic cyclic alkyl(amino)carbene (CAAC)-stabilized BB double bonds, which yield fully planar, π-delocalized 1,8-diaza-3,6-diboraoctatetraenes. Density functional theory studies show that these compounds have an open-shell singlet biradical ground state with a thermally accessible closed-shell state. In-depth computational mechanistic analyses show that they are formed via a biradical cycloaddition–cycloreversion mechanism. Finally, unlike their organic counterparts, these B,N-analogues of octatetraene can undergo two-electron chemical reduction to form diamagnetic dianions.

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Section: Resultssupporting

confidence: 79%

Hybrid Inorganic–Organic Cross-Metathesis between Diborenes and Acetylene

et al. 2021

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“…A certain resemblance to the “buckled dimer” of the reconstructed Si(100) surface is obvious for an amido-substituted Si 6 R 4 derivative, although the recently reported Si 9 R 3 – and Si 9 R 2 2– derivatives obviously feature even more “naked” vertices some of which are adjacent to one another. In neither of these cases, however, surface-like reactivity has been reported yet and a real functional model for the “buckled dimer” is still elusive despite the undoubted relevance of molecular disilenes and their reactivity for the Si(100) surface chemistry. − …”

Section: Discussionmentioning

confidence: 99%

Molecular Silicon Clusters

Heider

Scheschkewitz

2021

Chem. Rev.

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The continuously decreasing size of device features in microelectronics draws growing attention to the structuring of silicon at the molecular level with powerful tools provided by synthetic chemistry. Silicon clusters are of particular importance in this regard not only as potential precursors for silicon deposition but also as well-defined model systems for bulk and surfaces of silicon at the nanoscale as well as possible starting points for future construction of molecularly precise device structures. This review aims to give a comprehensive overview about the state of the art in the synthesis of molecular silicon clusters, which are grouped into (1) electron-precise saturated clusters, (2) soluble polyhedral Zintl anions, and (3) unsaturated silicon clusters, the so-called siliconoids. Particular attention is paid to functionalization as it is generally considered a necessary prerequisite for the design and construction of more extended systems. The interrelations between the three different classes of molecular silicon clusters, e.g., arising from the introduction of negatively charged functional groups, are highlighted on grounds of NMR properties and computed electronic structures.

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“…[9,10] In a recent collaborative effort with the Baines group, however, the diradical pathway gained significant support from experiments with the above-mentioned mechanistic probe. [11] In collaboration with the Manners group, we had reported the application of the [2 + 2] cycloaddition of disilenes to alkynes for the step growth polymerization of para-phenylenebridged tetrasiladienes with 1,4-diethynylbenzene to σ,π-conjugated hybridpolymers. [5] In these reactions, the two sterically less demanding ends of both substrates always ended up being adjacent to one another in the 1,2-disilacyclobutene units of the products as shown in an exemplary manner for II a in Chart 1.…”

Section: Introductionmentioning

confidence: 99%

Reactivity of Phenylacetylene toward Unsymmetrical Disilenes: Regiodivergent [2+2] Cycloaddition vs. CH Addition

Kell

Obeid

Bag

et al. 2021

Zeitschrift anorg allge chemie

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We report the regiodivergent reaction of phenylacetylene with a selection of disilenes Tip 2 Si=SiTipR as well as bridged tetrasiladienes Tip 2 Si=SiTipÀ LUÀ SiTip=SiTip 2 (Tip = 2,4,6-i Pr 3 C 6 H 2 , R = aryl groups; LU = arylene linkers). The regioselectivity of the [2 + 2] cycloaddition as determined by NMR spectroscopy and X-ray crystallography is shown to strongly depend on the nature of the substituent R. The small size of the substituents compared to the Tip groups in both cases suggests a change in mechanism between the substrates with only hydrogen in the ortho-positions of R and LU and those with either ortho-methyl groups or condensed aromatic rings. In contrast, the presence of catalytic quantities of base completely suppresses cycloaddtion in favor of the formal CH addition of phenylacetylene. Quenching reactions with either MeI or MeOH after the stoichiometric application of deprotonated phenylacetylene as well as NMR studies at low temperature prove the intermediacy of an alkynyl-substituted disilanyl lithium and thus suggest a carbolithiation pathway for the net CH addition.

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The Addition of a Cyclopropyl Alkyne to an Asymmetrically-Substituted Disilene: A Mechanistic Study

Cited by 9 publications

References 38 publications

Hybrid Inorganic–Organic Cross-Metathesis between Diborenes and Acetylene

Hybrid Inorganic–Organic Cross-Metathesis between Diborenes and Acetylene

Molecular Silicon Clusters

Reactivity of Phenylacetylene toward Unsymmetrical Disilenes: Regiodivergent [2+2] Cycloaddition vs. CH Addition

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