Silicon–Halogen Bond Activation in Mixed Si/Al Compounds and an Approach to Intramolecular Stabilized Silylium Ions

Abstract

Alkenylchlorosilanes functionalized by coordinatively unsaturated Al atoms, R′′(R′)Si(Cl)C(AltBu 2 )=C(H)R 5 [R = tBu, cHex, 1-Ad, Ph, 3,5-(F 3 C) 2 C 6 H 3 ; R′ = Mes, Ph, 4-tBuC 6 H 4 , 4-tBuOC 6 H 4 , 4-Et 2 NC 6 H 4 , tBu; R′′ = Mes, CH(SiMe 3 ) 2 , tBu], were obtained in good yields by hydroalumination of the respective alkynylchlorosilanes R′′(R′)Si(Cl)C≡C-R 3 with t Bu 2 Al-H. They feature four-membered, close to planar SiCAlCl heterocycles by intramolecular Al-Cl interactions. The activation of the Si-Cl bonds results in bond lengthening from about 209 pm in 3 to 220 to 225 pm in compounds 5. The 29 Si NMR resonances show an increasing shift to a lower field and range from δ = 24.0 for 5a [R = tBu, R′ = R′′ = Mes] to δ = 68.1 for 5j [R = R′ = R′′ = [a]

MCl2Molecules (M = Zn, Cd, Hg) Coordinated by Trifunctional E/P2-Based FLPs (E = Ga, In): Chelating Coordination of the Metal Atoms and Activation of M–Cl Bonds by E–Cl Interactions

“…The increasing approach to a planar surrounding is also reflected by the sum of the angles in these planes (MP 2 Cl): 353.8, 351.5, 356.4, and 359.4°, respectively. These observations may indicate the strongest weakening of the M–Cl br bond in the case of the soft Hg atom and the increasing cationic character of the M atoms . The M–P distances are the longest for the Cd compound 9 (M = Zn, 2.463­(av) Å; M = Cd, 2.587­(av) Å; M = Hg, 2.495­(av) Å).…”

Hydroboration of alkynylchlorosilanes as an efficient route for the synthesis of SiNNB heterocycles

“…[ 15 ] The 11 B NMR spectra showed broad resonances with chemical shifts of around 80 ppm, which is within the characteristic range of three‐coordinate boron atoms. [ 24,25 ] In contrast to strongly related aluminum compounds, [ 26,27 ] this observation excludes significant interactions between the Lewis acids and the chlorine atoms. This constitution was confirmed in this study by crystal structure determination with 3 (see below).…”

“…Such MÁÁÁCl bridges have been reported in the literature for analogous compounds with M = B, Al, Ga. [27,31,36] With the heavier congeners of boron (M = Al, Ga) such interactions are relatively strong and result in a considerable activation of Si-Cl bonds. [26,27,37] The different behavior may be caused by the stronger charge separation in bonds including electropositive aluminum or gallium atoms and a strong electrostatic contribution to the interaction between Cl and Al or Ga atoms. Other bond lengths and angles are unexceptional and resemble data reported in the literature.…”

Solution Phase Reactivity of Dibenzo[c,e][1,2]azaborinine: Activation and Insertion into Si‐E Single Bonds (E=H, OSi(CH3)3, F, Cl) by a BN‐Aryne

“…[7a] The single bonds of silicon with fluorine, chlorine, and oxygen (SiÀ E, E = F, Cl, O) are remarkably strong (142, 106, and 95 kcal mol À 1 , respectively), [13] but can react with strong electrophiles. [14] While abstraction of fluoride from SiÀ F has been reported, [15] insertion into SiÀ F bonds is rare [16] and was studied computationally. [17] On the other hand, insertion reactions were reported for the weaker SiÀ Cl and SiÀ O bonds, in particular with transient and stable silylenes.…”