Activation of CO Using a 1,2‐Disilylene: Facile Synthesis of an Abnormal N‐Heterocyclic Silylene

Abstract

Reaction of the 1,2‐disilylene, [{ArC(NDip)2}Si]2 1 (Dip=2,6‐diisopropylphenyl, Ar=4‐C6H4But), with CO proceeds via insertion of CO into one Si−N bond, and Si−Si bond cleavage, to cleanly give the bis(silylene), {ArC(NDip)2}Si(:)OnormalCnormalSnormali(:)(normalNnormalDnormalinormalp)​2normalC‾ Ar 2, under ambient conditions. The reaction can be partially reversed when solutions of 2 are subjected to UV irradiation. The five‐membered heterocyclic fragment of 2 represents the first silicon analogue of an “abnormal” N‐heterocyclic carbene (aNHC), a view which is substantiated by a computational analysis of the compound. Reaction of 2 with [Mo(CO)6] under UV light affords the chelate complex, [Mo(CO)4(κ2‐Si,Si‐2)] 3, while reaction with [Fe(CO)5] gives the unusual silyleneyl bridged complex, [{Fe2(CO)6}{μ‐Si[(NDip)2CAr]}2] 4. The same coordination complexes can be accessed by reaction of 1 with [Mo(CO)6] or [Fe(CO)5] under UV light. As is the case for aNHCs, d‐block metal complexes of bis(silylene) 2 could prove useful as bespoke catalysts for organic transformations.

Stabilization and One Electron Reduction of a Silicon Analogue of a Carboxylic Acid Anhydride

“…After reaction work-up the sila-acid anhydride compounds 2a and 2b were isolated as colorless crystalline materials in yields of approximately 50 % (Scheme 1). Compounds 2a and 2b were alternatively prepared in moderate isolated yields by exposing deep orange toluene solutions of the abnormal N-heterocyclic silylenes ( DipAr Am)SiOCSi{(NDip)2CAr} (Ar = Ar' 3a [9] or Ph 3b) to N2O gas at room temperature. These reactions were seemingly complete within a matter of seconds, as determined by the rapid change in color of the reaction solutions to pale yellow.…”

“…Melting points were determined in sealed glass capillaries under dinitrogen and are uncorrected. The starting materials, {( DipAr' Am)Si}2, [7] ( DipAr' Am)SiOCSi{(NDip)2CAr'}, [9] DipPh AmH [18] and [{( Mes Nacnac)Mg}2] [13] were prepared by literature procedures. N2O and CO gas were dried over P2O5 prior use.…”

“…Here we show that treatment of {( DipAr' Am)Si}2, and a new 1,2-disilylene, with N2O yield the first examples of Lewis base free sila-acid anhydrides, which are readily hydrolyzed to corresponding sila-acids. Similarly, abnormal N-heterocyclic silylenes, recently developed in our group, [9] have been oxidized to give the same sila-acid anhydrides. Reaction of one of these with a dimagnesium(I) compound leads to oneelectron reduction of the sila-acid anhydride, affording a -diketiminate magnesium complex of its https://doi.org/10.26434/chemrxiv-2023-zxbzz ORCID: https://orcid.org/0000-0002-7269-1045 Content not peer-reviewed by ChemRxiv.…”