Reactions of Alkenes and Alkynes with an Acyclic Silylene and Heavier Tetrylenes under Ambient Conditions

Lips, Felicitas; Mansikkamäki, Akseli; Fettinger, James C.; Tuononen, Heikki M.; Power, Philip P.

doi:10.1021/om500947x

Cited by 42 publications

(20 citation statements)

References 64 publications

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“…In line with the calculated singlet‐triplet and HOMO‐LUMO gaps, the stannylenes showed the highest barriers between 190 (for Ph YSnB 2 ) and 312 kJ/mol (for Tos YSnHMDS ) for the single‐site activation (Pathway A), the silylenes the lowest (77.6–174.5 kJ/mol). This corroborates with previous studies on other tetrylenes [35] . In general, the use of an electron‐donating second substituent is detrimental for facile H 2 activation, whereas the use of electron withdrawing groups, especially boryl substituents, results in lower barriers.…”

Section: Resultssupporting

confidence: 91%

Single‐Site and Cooperative Bond Activation Reactions with Ylide‐Functionalized Tetrylenes: A Computational Study

2021

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Due to their transition metal‐like behavior divalent group 14 compounds bear huge potential for their application in bond activation reactions and catalysis. Here we report on detailed computational studies on the use of ylide‐substituted tetrylenes in the activation of dihydrogen and phenol. A series of acyclic and cyclic ylidyltetrylenes featuring various α‐substituents with different σ‐ and π‐donating capabilities have been investigated which demonstrate that particularly π‐accepting boryl groups lead to beneficial properties and low barriers for single‐site activation reactions, above all in the case of silylenes. In contrast, for the thermodynamically more stable germylenes and stannylenes an alternative mechanism involving the active participation of the ylide ligand in the E−H bond (E=H or PhO) activation process by addition across the element carbon linkage was found to be energetically favored. Furthermore, the boryl substituted tetrylenes allowed for a further activation pathway involving the active participation of the boron element bond. These cooperative mechanisms are especially attractive for the heavier cyclic ylidyltetrylenes in which the loss of the protonated ylide group is prevented due to the cyclic framework. Overall, the present studies suggest that cyclic ylide‐substituted germylenes and stannylenes bear huge potential for cooperative bond activations at mild conditions which should be experimentally addressed in the future.

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Section: Resultssupporting

confidence: 91%

Single‐Site and Cooperative Bond Activation Reactions with Ylide‐Functionalized Tetrylenes: A Computational Study

2021

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“…The ca. 30-fold lower rate constant for reaction of Si t Bu 2 with TME compared to those with cis -cyclooctene or 1-hexene can be ascribed to steric destabilization of the transition state for the reaction, in which the initial bonding interaction is between the nonbonded p-orbital on silicon (perpendicular to the 3-atom bonding plane of the silylene) and the π-MO of the alkene, and the silylene is oriented with its substituents approximately bisecting the alkene CC bond . The rate constants for reaction of the series of alkenes with SiMes 2 are systematically 20–100× smaller than those for Si t Bu 2 , but the spread in reactivity throughout the series is similar.…”

Section: Resultssupporting

confidence: 90%

Photochemical Generation and Characterization of Di-tert-butylsilylene (Si^tBu₂) in Solution

Duffy

Leigh

2019

Organometallics

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Di-tert-butylsilylene (Si t Bu 2 ) has been detected directly in solution and its reactivity characterized by laser flash photolysis methods. Laser photolysis of 7,7-di-tert-butyl-7-silabicyclo[4.1.0]heptane (5) affords a transient product that exhibits λ max ≈ 520 nm and decays on the microsecond time scale, concurrent with the growth of a second, much longer-lived species exhibiting λ max = 290, 430 nm. The two species are assigned to di-tert-butylsilylene (Si t Bu 2 ) and its disilene dimer, tetratert-butyldisilene ( t Bu 2 SiSi t Bu 2 , 8), respectively. Transient absorption spectra recorded by laser photolysis of hexa-tert-butylcyclotrisilane ( 7) are consistent with the prompt formation of both Si t Bu 2 and 8, the former appearing as a weak shoulder absorption on the red edge of the intense absorption band due to the disilene. Absolute rate constants were determined for the reactions of Si t Bu 2 with a variety of representative silylene substrates in hexanes at 25 °C, including methanol, triethylsilane, acetic acid, acetone, molecular oxygen, and four aliphatic alkenes (1-hexene, cyclohexene, cis-cyclooctene, and 2,3-dimethyl-2-butene). Rate and(or) equilibrium constants for Lewis acid−base complexation of the silylene with diethyl ether, tetrahydrofuran, tetrahydrothiophene, and diethyl-and triethylamine were also determined, along with the UV−vis absorption spectra of the corresponding Lewis acid−base complexes. Rate constants for the reactions of dimethylsilylene (SiMe 2 ) and dimesitylsilylene (SiMes 2 ) with cis-cyclooctene, 2,3-dimethyl-2-butene, and 1hexene are also reported, enabling a comprehensive assessment to be made of steric effects on the reactivities of simple (transient) dialkyl-and diarylsilylene derivatives in solution. The kinetic data show the reactivity of Si t Bu 2 to be intermediate between that of SiMe 2 and SiMes 2 under similar conditions, with the (2 + 1)-cycloaddition reactions with alkenes exhibiting the largest variations in rate constant as a function of substitution at Si. Absolute rate constants for the reactions of tetra-tertbutyldisilene (8) with O 2 and acetone are also reported.

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“…All hydrogen atoms omitted for clarity (bond length in Å, angles in deg). Ge(1)-P(1) 2.380(3), Ge(1)-Si(1) 2.489(3), Ge(1)-Ge(2) 2.5210 (18), Ge(2)-Cl(2) 2.208(4), Ge(2)-Cl(1) 2.253(3), Ge(2)-Si(6) 2.428(3), Si(1)-Si(2) 2.361(4), Si(2)-C(1) 1.864 (14), P(1)-C(11) 1.807 (13), P(1)-Ge(1)-Si(1) 99.69 (11), P(1)-Ge(1)-Ge(2) 93.80 (9), Si(1)-Ge(1)-Ge(2) 105.64 (9), Cl(2)-Ge(2)-Cl(1) 99.49 (17), Cl(2-Ge(2)-Si(6) 102.67 (14), Cl(1)-Ge(2)-Si(6) 101.21 (12), Cl(2)-Ge(2)-Ge(1) 108.28 (12), Cl(1)-Ge(2)-Ge(1) 116.19 (10), Si(6)-Ge(2)-Ge(1) 125.38(10).…”

Section: Resultsmentioning

confidence: 99%

“…A most unusual reaction of this compound, we observed the regioselective 1,2-migratory insertion of phenylacetylene into one or two of the Ge-Si bonds of 1 (Scheme 1) [5]. While, typically, reactions of silylenes and germylenes with alkynes lead to oxidation and the formation of tetravalent sila-and germacyclopropenes [6][7][8][9][10][11][12], the observed phenylacetylene insertion case benefits from the fact that formation of the vinylgermylene PMe 3 adduct (2) is thermodynamically favored compared to the respective germacyclopropene, which exists as an intermediate on the reaction pathway [13].…”

Section: Introductionmentioning

confidence: 91%

1,2- and 1,1-Migratory Insertion Reactions of Silylated Germylene Adducts

2020

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The reactions of the PMe3 adduct of the silylated germylene [(Me3Si)3Si]2Ge: with GeCl2·dioxane were found to yield 1,1-migratory insertion products of GeCl2 into one or two Ge–Si bonds. In a related reaction, a germylene was inserted with tris(trimethylsilyl)silyl and vinyl substituents into a Ge–Cl bond of GeCl2. This was followed by intramolecular trimethylsilyl chloride elimination to another cyclic germylene PMe3 adduct. The reaction of the GeCl2 mono-insertion product (Me3Si)3SiGe:GeCl2Si(SiMe3)3 with Me3SiC≡CH gave a mixture of alkyne mono- and diinsertion products. While the reaction of a divinylgermylene with GeCl2·dioxane only results in the exchange of the dioxane of GeCl2 against the divinylgermylene as base, the reaction of [(Me3Si)3Si]2Ge: with one GeCl2·dioxane and three phenylacetylenes gives a trivinylated germane with a chlorogermylene attached to one of the vinyl units.

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Reactions of Alkenes and Alkynes with an Acyclic Silylene and Heavier Tetrylenes under Ambient Conditions

Abstract: ABSTRACT. Cycloaddition reactions of the acyclic silylene Si(SAr iPr 4 )2 with a variety of alkenes and alkynes were investigated. Its reactions with the alkynes phenylacetylene, diphenylacetylene, and the diene 2,3-dimethyl-1,3-butadiene yielded silacycles

Cited by 42 publications

References 64 publications

Single‐Site and Cooperative Bond Activation Reactions with Ylide‐Functionalized Tetrylenes: A Computational Study

Single‐Site and Cooperative Bond Activation Reactions with Ylide‐Functionalized Tetrylenes: A Computational Study

Photochemical Generation and Characterization of Di-tert-butylsilylene (Si^tBu₂) in Solution

1,2- and 1,1-Migratory Insertion Reactions of Silylated Germylene Adducts

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Reactions of Alkenes and Alkynes with an Acyclic Silylene and Heavier Tetrylenes under Ambient Conditions

Abstract: ABSTRACT. Cycloaddition reactions of the acyclic silylene Si(SAr iPr 4 )2 with a variety of alkenes and alkynes were investigated. Its reactions with the alkynes phenylacetylene, diphenylacetylene, and the diene 2,3-dimethyl-1,3-butadiene yielded silacycles

Cited by 42 publications

References 64 publications

Single‐Site and Cooperative Bond Activation Reactions with Ylide‐Functionalized Tetrylenes: A Computational Study

Single‐Site and Cooperative Bond Activation Reactions with Ylide‐Functionalized Tetrylenes: A Computational Study

Photochemical Generation and Characterization of Di-tert-butylsilylene (SitBu2) in Solution

1,2- and 1,1-Migratory Insertion Reactions of Silylated Germylene Adducts

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Photochemical Generation and Characterization of Di-tert-butylsilylene (Si^tBu₂) in Solution