Dry Chemistry of Ferrate(VI): A Solvent‐Free Mechanochemical Way for Versatile Green Oxidation

Abstract

The +6 oxidation state of iron generally exists in the form of ferrate(VI) with high redox potential and environmentally friendly nature. Although ferrate(VI) has been known for over a century, its chemistry is still limited to the solvent-based reactions that suffers from the insolubility/instability of this oxidant and the environmental issues caused by hazardous solvents. Herein, we explore the solvent-free reactivity of ferrate(VI) under mechanical milling, revealing that its strong oxidizing power is accessible in the "dry" solid state towards a broad variety of substrates, for example, aromatic alcohols/aldehydes and carbon nanotubes. More significantly, solvent-free mechanochemistry also reshapes the oxidizing ability of ferrate(VI) due to the underlying solvent-free effect and the promotive mechanical actions. This study opens up a new chemistry of ferrate(VI) with promising application in green oxidative transformation of both organic and inorganic substrates.

Mechanosynthesis of Odd‐Numbered Tetraaryl[n]cumulenes

“…[20,21,23] Next, using the established ball milling conditions for the mechanochemical Favorskii alkynylation-type reaction, as eries of ketones 1a-j,c alcium carbide,a nd KOHw ere reacted (Scheme 4). Immediate analysis of the crude reaction mixture by solution NMR spectroscopy confirmed the formation of [5]cumulene 6a upon milling. Similarly,u nsymmetrical ketones such as phenyl 2-pyridyl ketone (1h), 4-fluorobenzophenone (1i), and tert-butyl phenyl ketone (1j)also underwent the mechanochemical alkynylation reactions affording the correspond- With al ibrary of mechanochemically synthesized 2butyne-1,4-diols 2 at our disposal, we selected afew additional representative examples to test the mechanochemical SnCl 2mediated reductive elimination.…”

“…[1] One of the most distinct benefits of mechanochemical syntheses by ball milling is the possibility to generate unique product compositions compared to solution-based protocols. [3,4] Thus,new avenues to react chemicals that differ in their solubility profiles were opened, [5] forw hich finding ac ommon reaction medium would be otherwise problematic.S uch advantages by mechanochemistry have proven particularly valuable in areas of research focused on the synthesis and functionalization of poorly soluble two-and three-dimensional carbon-based materials.Examples include the iconic mechanochemical dimerization of C 60 , [6] thedevelopment of mechanically based procedures for the delamination of graphite, [7] them echanochemical functionalization of graphene nanosheets, [8] and the recent mechanosynthesis of nanographenes, [9] to name just af ew. [3,4] Thus,new avenues to react chemicals that differ in their solubility profiles were opened, [5] forw hich finding ac ommon reaction medium would be otherwise problematic.S uch advantages by mechanochemistry have proven particularly valuable in areas of research focused on the synthesis and functionalization of poorly soluble two-and three-dimensional carbon-based materials.Examples include the iconic mechanochemical dimerization of C 60 , [6] thedevelopment of mechanically based procedures for the delamination of graphite, [7] them echanochemical functionalization of graphene nanosheets, [8] and the recent mechanosynthesis of nanographenes, [9] to name just af ew.…”

“…Mechanosynthesis of [5]cumulene 6a.a)CuCl (1.0 equiv), TMEDA (1.0 equiv),8 00 rpm, 120 min. Mechanosynthesis of [5]cumulene 6a.a)CuCl (1.0 equiv), TMEDA (1.0 equiv),8 00 rpm, 120 min.…”

“…Additionally,t he mechanochemical approach was successfully extended to the synthesis of the illustrative tetraphenyl [5]cumulene (6a)after am echanochemical copper-mediated oxidative coupling of propargylic alcohol 3a followed by reductive elimination of diyne diol 5a with SnCl 2 ·2 H 2 O. Additionally,t he mechanochemical approach was successfully extended to the synthesis of the illustrative tetraphenyl [5]cumulene (6a)after am echanochemical copper-mediated oxidative coupling of propargylic alcohol 3a followed by reductive elimination of diyne diol 5a with SnCl 2 ·2 H 2 O.…”

Mechanochemie gasförmiger Reaktanten

“…In diesem Zusammenhang hat die mechanochemische Synthese die Aufwertung von schwer lçslichen Reagenzien oder Verbindungen, die nur eine bedingte Sta-bilitätinLçsung aufweisen, ermçglicht. [20] Des Weiteren kann die mechanische Behandlung selbst zu einem Aufbrechen von kristallinen Festkçrpern führen, wodurch die Partikelgrçße reduziert, die Morphologie verändert und das Material amorphisiert wird. Außerdem fçrdert die konstante,m echa-nische Belastung eine kontinuierliche Bildung von aufgebrochenen, reaktiven Lagen und Kristalldefekten.…”