Intercepting the Disilene‐Silylsilylene Equilibrium

Abstract

The equilibrium between disilenes (R2Si=SiR2) and their silylsilylene (R3Si−SiR) isomers has previously been inferred but not directly observed, except in the case of the parent system H2Si=SiH2. Here, we report a new method to prepare base‐coordinated disilenes with hydride substituents. By varying the bulk of the coordinating base and other silicon substituents, we have been able to control the rearrangement of disilene adducts to their silylsilylene tautomers. Remarkably, 1,2 migration of a trimethylsilyl group is preferred over hydrogen migration. A DFT study of the reaction mechanism provides a rationale for the observed reactivity and detailed information on the bonding situation in base‐stabilized disilenes.

Main Group Multiple Bonds for Bond Activations and Catalysis

“…4-pyrollidinopyridine( 4-PPy) allowed for isolation of disilene 74.4 -PPy was found to be labile and in the presence of excess NHCl igand, isomerisation to silylsilene 76 was achieved (Scheme 16). [104] This observation of 74 and 76 serves as direct evidencef or the transient nature of 75 and 75',w hich is also supported by computational studies. [104] The ability to control this equilibrium provides anew route to access to the more reactive silylsilylenes pecies.…”

“…[104] This observation of 74 and 76 serves as direct evidencef or the transient nature of 75 and 75',w hich is also supported by computational studies. [104] The ability to control this equilibrium provides anew route to access to the more reactive silylsilylenes pecies. Two-coordinate acyclic silylenes are highly reactives pecies as they contain av acant coordination site and al one pair,a nd as such have shown facile bond activations towards small molecules and av ariety of substrates.…”

“…In the case of SiMe 3 substituents (101)a1,3-silyl migration was observedt of orm an intermediate disilene complex (103), analogous to keto-enol isomerisation. However,u se of as uper silyl supporting ligand (tBu 3 Si, Compound 102)r esultsi nformation of at wo-coordinate N,O-silylene (104). The differing reactivity of the two complexes wass hown on reaction with ethylene (Scheme22).…”

An NHC‐Mediated Metal‐Free Approach towards an NHC‐Coordinated Endocyclic Disilene

“…When solutions of 2 were placed under atmospheres of H 2 , CO or ethylene, no reaction was observed under standard conditions. However, when those solutions were irradiated with blue light (λ = 456 nm) overnight, the major, and only identifiable products, as determined by NMR spectroscopy, were 3 and 6), Si(1)À Si(5) 2.3751(4), Si(1)À Si(2) 2.3516(4), Si(2)À Si(3) 2.3512(4), Si(3)À Si(4) 2.3540(5), Si(5)À Si(5#) 2.3700 (6).…”

New Strategies towards Bulky Bis(alkyl)‐ and Bis(silyl)‐ Substituted Polysilanes as Precursor Molecules for Desilylation and Dechlorination Experiments

“…[13] Simultaneously the groups of Scheschkewitz [14] and Lips [15] reported cyclotrisilane NHC adducts V. Holthausen and Cowley isolated a bis(silyl)silyene VI via a disilene-silylsilylene equilibrium. [16] Holthausen and Schneider also obtained the first the bis(trichlorosilyl)silylene VII, which is stabilized by a amphiphilic dichlorosilylene group. [17] Inoue pioneered the first synthetically accessible bis(silyl)silylene VIII, which is in a dynamic equilibrium with its corresponding tetrasilyldisilene (Scheme 2).…”