Abstract:The donor-stabilized sila--lactone 1 reacts with CO 2 via a remarkable reversible [2+2]-cycloaddition reaction to form the spiro-cyclic silicon carbonate derivative 2. Furthermore, photolysis of 2 under pressure of CO 2 affords the first persistent SiO 2-CO 2cycloadduct 3, presenting a Si 2 O 4-like structure, which is stabilized by a Lewis donor-acceptor type ligand. As predicted by theoretical calculations, in marked contrast to the thermodynamically stable SiO 2-dimer, the SiO 2-CO 2 mixed cycloadduct 3 is… Show more
“…In this context, Scheschkewitz and co-workers recently isolated the asymmetric disilene IIb in which the induced polarization of the Si = Si bond, resulting from the replacement of one Tipp ligand of IIa with a2 ,4,6-trimethoxyphenyl (TMOP) group,r e-enabled the quantitative and regioselective formation of Tipp 2 HSiÀSiNH 2 (Tipp)TMOP IIb' ' with ammonia. [8] Another attractive molecule for the metal-free fixation by main group compounds is carbon dioxide.Inthe last couple of years diverse CO 2 activations involving low-valent silicon complexes have been reported; [9] however, its reactivity toward multiply bonded silicon compounds has been explored to af ar lesser extent. Notably,i th as been demonstrated by Robinson et al that N-heterocyclic carbene (NHC)-supported Si 0 complex (IPr)Si = Si(IPr) could be oxidized by CO 2 to NHC-stabilized silicon-carbon mixed oxide III.…”
The activation of NH and CO is still an ambitious target for multiply bonded sub-valent silicon compounds. Now, the precise splitting of the N-H bond of ammonia by (Z)-imino(silyl)disilene 1 to give trans-1,2-adduct 2 a at low temperatures (-78 °C) is presented. According to DFT calculations, the stereospecific hydroamination follows a similar mechanism as the recently reported anti-addition of H to the Si=Si bond of 1. The aminosilane 2 b could also be obtained as the formal silylene addition product under thermodynamic reaction control. By applying low temperatures, the activation of CO with 1 selectively afforded the cis-oxadisilacyclobutanone 7-c as [2+2] cycloadduct. By performing the reaction directly at ambient temperatures, a mixture of three different-sized silacycles (4-6) was observed. Their formation was investigated theoretically and their structures were revealed with separate experiments using 1 and the oxygenation agents N O and O .
“…In this context, Scheschkewitz and co-workers recently isolated the asymmetric disilene IIb in which the induced polarization of the Si = Si bond, resulting from the replacement of one Tipp ligand of IIa with a2 ,4,6-trimethoxyphenyl (TMOP) group,r e-enabled the quantitative and regioselective formation of Tipp 2 HSiÀSiNH 2 (Tipp)TMOP IIb' ' with ammonia. [8] Another attractive molecule for the metal-free fixation by main group compounds is carbon dioxide.Inthe last couple of years diverse CO 2 activations involving low-valent silicon complexes have been reported; [9] however, its reactivity toward multiply bonded silicon compounds has been explored to af ar lesser extent. Notably,i th as been demonstrated by Robinson et al that N-heterocyclic carbene (NHC)-supported Si 0 complex (IPr)Si = Si(IPr) could be oxidized by CO 2 to NHC-stabilized silicon-carbon mixed oxide III.…”
The activation of NH and CO is still an ambitious target for multiply bonded sub-valent silicon compounds. Now, the precise splitting of the N-H bond of ammonia by (Z)-imino(silyl)disilene 1 to give trans-1,2-adduct 2 a at low temperatures (-78 °C) is presented. According to DFT calculations, the stereospecific hydroamination follows a similar mechanism as the recently reported anti-addition of H to the Si=Si bond of 1. The aminosilane 2 b could also be obtained as the formal silylene addition product under thermodynamic reaction control. By applying low temperatures, the activation of CO with 1 selectively afforded the cis-oxadisilacyclobutanone 7-c as [2+2] cycloadduct. By performing the reaction directly at ambient temperatures, a mixture of three different-sized silacycles (4-6) was observed. Their formation was investigated theoretically and their structures were revealed with separate experiments using 1 and the oxygenation agents N O and O .
“…Stable acceptor structures that form OH-Si-O-Si-OH or OH-Si-O-Ca 2+ /Ba 2+ -Si-OH species are more likely to accept protons from the intermediate OH*, resulting in a 10-fold enhancement in the overall OER performance (Fig. 3a ) 20 . Fig.…”
Transition metal oxides are promising electrocatalysts for zinc-air batteries, yet surface reconstruction caused by the adsorbate evolution mechanism, which induces zinc-ion battery behavior in the oxygen evolution reaction, leads to poor cycling performance. In this study, we propose a lattice oxygen mechanism involving proton acceptors to overcome the poor performance of the battery in the OER process. We introduce a stable solid base, hydroxy BaCaSiO4, onto the surfaces of PrBa0.5Ca0.5Co2O5+δ perovskite nanofibers with a one-step exsolution strategy. The HO-Si sites on the hydroxy BaCaSiO4 significantly accelerate proton transfer from the OH* adsorbed on PrBa0.5Ca0.5Co2O5+δ during the OER process. As a proof of concept, a rechargeable zinc-air battery assembled with this composite electrocatalyst is stable in an alkaline environment for over 150 hours at 5 mA cm–2 during galvanostatic charge/discharge tests. Our findings open new avenues for designing efficient OER electrocatalysts for rechargeable zinc-air batteries.
The activation of NH3 and CO2 is still an ambitious target for multiply bonded sub‐valent silicon compounds. Now, the precise splitting of the N−H bond of ammonia by (Z)‐imino(silyl)disilene 1 to give trans‐1,2‐adduct 2 a at low temperatures (−78 °C) is presented. According to DFT calculations, the stereospecific hydroamination follows a similar mechanism as the recently reported anti‐addition of H2 to the Si=Si bond of 1. The aminosilane 2 b could also be obtained as the formal silylene addition product under thermodynamic reaction control. By applying low temperatures, the activation of CO2 with 1 selectively afforded the cis‐oxadisilacyclobutanone 7‐c as [2+2] cycloadduct. By performing the reaction directly at ambient temperatures, a mixture of three different‐sized silacycles (4–6) was observed. Their formation was investigated theoretically and their structures were revealed with separate experiments using 1 and the oxygenation agents N2O and O2.
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