Search

The reaction of the bicyclic silicon(I) ring compound Si4{N(SiMe3)Mes}41 with strong zwitterionic character and moderate sterical demand of the amido substituents with two equivalents of KC8 was investigated. This resulted in the unexpected abstraction of two amido substituents from 1 and additionally in dimerization to a dianionic Si8 cluster compound 2 with four unsubstituted silicon atoms and two [K([18]crown‐6)]+ counter cations. Performing this reaction in the absence of [18]crown‐6 results in release of only one amido substituent from 1 and dimerization to a dianionic Si8 cluster 3 with only two unsubstituted silicon atoms. This reaction with KC8 was repeated and trapping agents such as SiMe3Cl and tBuCl were added in‐situ whereupon the second isolated homocyclic silylene 4 and a monoanionic hydride and tBu substituted Si8 cluster 5 with one unsubstituted silicon atom were isolated. Furthermore, 1 was reacted with KOtBu which resulted in the selective abstraction of one SiMe3 group and formation of the tetrahedral silanide 6 with one imido substituent bridging an edge of the tetrahedron. [ABSTRACT FROM AUTHOR]

The bicyclic silicon(I) ring compound Si4{N(SiMe3)Mes}4 (2) was used as starting material in reactions with chalcogens and chalcogen transfer agents at low temperatures. This resulted in the selective formation of new cage compounds. With Me3NO, a silicon oxide with adamantane‐type cage 3 was isolated that represents the first isolated T4 silsesquioxane. Reactions with propylenesulfide and red selenium gave direct access to defect heterocubane‐type cages 4 and 5 with three Si−Si bonds wherein the silicon atoms adopt different low oxidation states of +I and +III. A reaction with elemental tellurium even occurs below room temperature to provide ditelluro−tetrasila−tricyclohexane 6. [ABSTRACT FROM AUTHOR]

The reaction of the six-vertex amido-substituted silicon cluster Si6{N(SiMe3)Ph}6 1 with two equiv. of KC8 results in the abstraction of K{N(SiMe3)Ph} and leads to the contact ion pair 2 including an anionic silicon cluster with two unsubstituted pyramidal vertices. Facile functionalization of 2 was achieved with MeI, SiCl4 and SiBr4 and results in neutral two-fold functionalized silicon clusters. [ABSTRACT FROM AUTHOR]

The synthesis of mixed silicon and germanium clusters SixGe6−x{N(SiMe3)Dipp}41–3 (x = 3.7, 3.1, 2.1) with amido-substituents and two unsubstituted germanium atoms was achieved in co-reductions using the tribromosilane {N(SiMe3)Dipp}SiBr3 and the tribromogermane {N(SiMe3)Dipp}GeBr3 in three different ratios. The ratio of Si and Ge used for the synthesis of 1–3 approximately corresponds to that in the final products. All compounds were characterized by single crystal X-ray diffraction and EI mass spectrometry. In addition, 1 and 2 were characterized by solid-state 29Si{1H} CP/MAS NMR spectroscopy and multinuclear NMR spectroscopy in solution. [ABSTRACT FROM AUTHOR]

In‐situ generated amido‐substituted disilynes (SiMe3)2N−Si≡Si−N(SiMe3)21 and (SiMe3)DippN−Si≡Si−N(SiMe3)Dipp 2 were observed examined upon the reductive dehalogenation of the tribromosilanes {N(SiMe3)2}SiBr33 and {N(SiMe3)Dipp}SiBr34 with Rieke magnesium (Mg*). Both disilynes were trapped with ethylene to yield the double [2+1] and [2+2] cycloaddition products 5 and 6, respectively. The transient disilynes 1 and 2 were investigated with DFT calculations that revealed 1 to feature more triple bond character than 2. The in‐situ generated disilyne 2 was further quenched with 1,5‐cyclooctadiene to yield the double [2+2] cycloaddition product 7. In the presence of cyclooctatetraene, the reductive debromination of 4 with Mg* generates the bromo‐substituted silacyclopentene 8. This species was also isolated with 2,3‐dimethyl‐1,3‐butadiene used as trapping reagent as the major product 9, besides the side product 10, that comprises two cyclotrisilene rings linked via a butene unit. The formation of 10 shows that a cyclotrisilene can occur as a side product during the reductive debromination of 4 in the presence of the alkene. [ABSTRACT FROM AUTHOR]

Copyright of Angewandte Chemie is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Isolation of the neutral homocyclic silylene 2 is possible via amine ligand abstraction with potassium graphite (KC8) and subsequent reaction with SiMe3Cl from a bicyclic silicon(I) amide J. This reaction proceeds via an anionic homoaromatic silicon ring compound 1 as an intermediate. The twofold‐coordinated silicon atom in the homocyclic silylene 2 is stabilized by an allyl‐type π‐electron delocalization. 2 reacts in an oxidative addition with two equivalents of MeOH and in cycloadditions with ethene, phenylacetylene, diphenylacetylene and with 2,3‐dimethyl‐1,3‐butadiene to afford novel functionalized ring compounds. [ABSTRACT FROM AUTHOR]

The bicyclic amido‐substituted silicon(I) ring compound Si4{N(SiMe3)Mes}42 (Mes=Mesityl=2,4,6‐Me3C6H2) features enhanced zwitterionic character and different reactivity from the analogous compound Si4{N(SiMe3)Dipp}41 (Dipp=2,6‐iPr2C6H3) due to the smaller mesityl substituents. In a reaction with the N‐heterocyclic carbene NHCMe4 (1,3,4,5‐tetramethyl‐imidazol‐2‐ylidene), we observe adduct formation to give Si4{N(SiMe3)Mes}4 ⋅ NHCMe4 (3). This adduct reacts further with the Lewis acid BH3 to yield the Lewis acid–base complex Si4{N(SiMe3)Mes}4 ⋅ NHCMe4 ⋅ BH3 (4). Coordination of AlBr3 to 2 leads to the adduct 5. Calculated proton affinities and fluoride ion affinities reveal highly Lewis basic and very weak Lewis acidic character of the low‐valent silicon atoms in 1 and 2. This is confirmed by protonation of 1 and 2 with Brookharts acid yielding 6 and 7. Reaction with diphenylacetylene only occurs at 111 °C with 2 in toluene and is accompanied by fragmentation of 2 to afford the silacyclopropene 8 and the trisilanorbornadiene species 9. [ABSTRACT FROM AUTHOR]

The synthesis of several different one-size adjustable-gap quaternary cluster anions by the reactions of defined mixtures of ternary salts and transition-metal ions is discussed. The approach has shown to be extremely useful for controlling the electron excitation energies of the water-soluble chalcogenidometalate compounds.

Copyright of Angewandte Chemie is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)