Facile Conversion of Bis-Silylene to Cyclic Silylene Isomers: Unexpected C–N and C–H Bond Cleavage

Abstract

Reaction of thiolate 1 with carbene-stabilized diiodo-bis-silylene (2) (in a 2:1 ratio) in THF unexpectedly gives both the first five-membered, sulfur-containing, zwitterionic silylene ring (3) via insertion of the "Si" unit of 2 into the olefinic C-H bond of the imidazole ring of 1 and four-membered cyclic silylene (4) via insertion of a silicon(I) atom of 2 into the C-N bond of the carbene ligand. The parallel reaction in toluene only gives 3 as the major product. The nature of the bonding in isomeric 3 and 4 was probed by experimental and theoretical methods.

Reduction and Rearrangement of a Boron(I) Carbonyl Complex

“…[49] To our knowledge the radical transfer of a nitrogen-bound aryl group to CO has never been observed in TM carbonyl chemistry. In low-valent main group chemistry, however, the cleavage of N-Caryl bonds by the insertion of borylene or silylene fragments has been observed at N-heterocyclic olefin [50] or carbene ligands, [51] respectively. The cyclic voltammogram of 3 in THF showed several irreversible oxidation waves as well as a reduction wave at −2.66 V (relative to the Fc/Fc + couple), suggesting the possibility of further chemical reduction (see Figure S36 in the SI).…”

“…[49] To our knowledge the radical transfer of a nitrogen-bound aryl group to CO has never been observed in TM carbonyl chemistry. In low-valent main group chemistry, however, the cleavage of N À C aryl bonds by the insertion of borylene or silylene fragments has been observed at N-heterocyclic olefin [50] or carbene ligands, [51] respectively.…”

Reactions of diborenes with terminal alkynes: mechanisms of ligand-controlled anti-selective hydroalkynylation, cycloaddition and CC triple bond scission

“…A similar exocyclic C-N bond activation at an NHC ligand has been observed in the reaction of a doubly NHC-stabilised diiododisilene with a thiolate. 49 The 11 B NMR spectrum of 5-Fc shows two broad resonances at À7.7 and À14.7 ppm, the former corresponding to the iPr-bearing B1 and the latter to the N-bound B2. The proton of the bridging alkene moiety appears in the 1 H NMR spectrum as a deshielded 1H singlet at 8.02 ppm.…”

Reduktion und Umlagerung eines Bor(I)‐Carbonylkomplexes

“…Jedoch konnte in der Chemie niedervalenter Hauptgruppenverbindungen die Spaltung von N‐C Aryl ‐Bindungen, über die Insertion eines Borylen‐ oder Silylenfragments an einem N‐heterocylcischen Olefin [50] bzw. eins Carbenliganden, [51] erzielt werden.…”