Preparation of a Silanone through Oxygen Atom Transfer to a Stable Cyclic Silylene

Abstract

We report the evaporation of a stable cyclic silylene and its oxidation (with ozone or N2 O) through oxygen atom transfer to form the corresponding silanone under matrix isolation conditions. As uncomplexed silanones are rare owing to their very high reactivity, this method provides an alternative route to these sought-after molecules. The silanone, as well as a novel bicyclic silane with a bridgehead silicon atom derived from an intramolecular silylene CH bond insertion, were characterized by comparison of high-resolution infrared spectra with density functional theory (DFT) computations at the M06-2X/cc-pVDZ level of theory.

From an Isolable Acyclic Phosphinosilylene Adduct to Donor‐Stabilized SiE Compounds (E=O, S, Se)

“…The n Si=S and n Si=Se stretching vibrations (3b: n Si=S = 665 cm À1 , 3a: n Si=Se = 578 cm À1 and 4a: n Si=Se = 577 cm À1 )a re shifted1 8a nd 37 cm À1 , respectively,t os maller wavenumbers in comparison to the analogous stretching vibrations in LSi(NHC)=E( L = CH[(C= CH 2 )CMe(NAr) 2 ], Ar = 2,6-iPr 2 C 6 H 3 )( n Si=S = 683 cm À1 , n Si=Se = 614 cm À1 ) [40] but are still larger than the corresponding values observedf or SiÀEs ingle-bond species( i.e.,f or (MeH 2 Si) 2 E, E = S, Se). [46] The n Si=O stretching vibrations of 4c (n Si=O = 1080 cm À1 )a re significantly bathochromically shifted relative to the corresponding wavenumbers of typical silanones (n Si=O = 1150-1300 cm À1 ) [47][48][49] and are almost similar to the n SiÀO stretching vibrations in (Me 2 HSi) 2 O( n SiÀO = 1074 cm À1 ). [46] These suggest the presence of az witterionic Si + ÀO À single bond instead of Si=Oi n4c.T his has been confirmed by density functional theory (DFT) studies at the B97-D/6-31G(d) level.…”

An Isolable Silicon Analogue of a Ketone that Contains an Unperturbed Si=O Double Bond

“…Theoretical calculations have predicted a substantial polarization of the Si=O bond (Si δ+ −O δ− ) due to the large difference in electronegativity between Si and O [Si: 1.7; O: 3.5 on the Allred–Rochow scale] and a remarkably weak π(Si−O) bond (58.5 kJ mol −1 ) compared to the σ(Si−O) bond (119.7 kJ mol −1 ) . Indeed, compounds with a Si=O double bond are intrinsically susceptible to auto‐oligomerization, and compounds with an Si=O double bond have so far only been postulated as fleeting intermediates during the formation of the corresponding oligomers (polysiloxanes, silicones), and detected as short‐lived species in low‐temperature matrices …”

“…Although the large protecting groups substantially increase the thermal stability of IIIA compared to that of other silanones that have only been observed in low‐temperature argon matrices (e.g. IIIB ), IIIA readily undergoes isomerization via 1,3‐migration of the i ‐PrMe 2 Si group from the carbon to the oxygen atom at room temperature. To further improve the thermal stability of the silanones, we designed a more robust substituent that contains bulky carbon‐based protecting groups with diminished migratory propensity relative to that of the i ‐PrMe 2 Si group.…”

Formation of 1-ethynyl-1H-silole from the reaction of silicon atoms with benzene: matrix infrared spectroscopy and quantum chemical calculations

“…24 A novel uncomplexed cyclic silanone has also been prepared by oxygen atom transfer from O 3 or N 2 O to stable silylene and the photochemical reaction of silylene in the inert matrix has been identified. 25 Meanwhile several silicon-containing heterocyclic compounds have been synthesized in the reactions of silicon atoms with conjugated p-systems through the matrix isolation method and they have been characterized by their IR or UV-vis spectra. [26][27][28][29] Although the thermally generated silicon atoms could insert into the C-C bond of benzene to form a seven-membered ring 1-silacycloheptatrienylidene as the final product via a Z 2 -p adduct intermediate upon irradiation in solid argon, no silole derivatives were observed in the reaction of silicon atoms with benzene (as shown in Scheme 1).…”