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Öğe Air and moisture stable para- and ortho-quinodimethane derivatives derived from bis-N-Heterocyclic olefins(American Chemical Society, 2023) Jana, Subhadip; Elvers, Benedict J.; Patsch, Sebastian; Sarkar, Pallavi; Krummenacher, Ivo; Nayak, Mithilesh Kumar; Maiti, Avijit; Chrysochos, Nicolas; Pati, Swapan K.; Schulzke, Carola; Braunschweig, Holger; Yıldız, Cem BuralHerein we report the development of a new methodology for the synthesis of various quinodimethane derivatives under two-electron oxidation of bis-Nheterocyclic olefins linked by different pi-conjugated aromatic spacers. In case of paraand ortho-phenylene bridge, we obtained air and moisture stable diimidazolium paraand ortho-quinodimethane derivatives. Analogues of the para-phenylene spacer such as tetrafluoro-p-phenylene and p-anthracene also led to the corresponding air and moisture stable quinodimethane derivatives. This emphasizes the influence of imidazolium substituents which facilitate the air and moisture stability of the quinodimethane derivatives. Differences were observed for the electron transfer processes: two one-electron vs one two-electron redox transitions between bis-N-heterocyclic olefins and diimidazolium-quinodimethanes depending on the employed pi-conjugated aromatic spacer. The formation of the pi-conjugated radical-cations, transient redox intermediates between bis-N-heterocyclic olefins and diimidazolium-quinodimethanes, was addressed by an EPR investigation.Öğe Assembly of NHC-stabilized 2-hydrophosphasilenes from Si(iv) precursors: a Lewis acid-base complex(Royal Society of Chemistry, 2016) Dhara, Debebrata; Mandal, Debdeep; Maiti, Avijit; Yıldız, Cem Burak; Kalita, Pankaj; Chrysochos, Nicolas; Schulzke, Carola; Chandrasekhar, Vadapalli; Jana, AnukulNHC-stabilized 2-hydrophosphasilenes are obtained from 1,2-dihydro-2-chlorophosphasilanes as Si(iv) precursors by a NHC-assisted 1,2-elimination of HCl. The NHC-exchange of these compounds is demonstrated as a proof of donor acceptor bonding between NHC and the silicon centre of the “P” moiety. We have also explored the possibility of similar exchanges in NHC-stabilized Si2 and P2 compounds. Theoretical DFT calculations were performed to address the nature of Si-P bonding in the NHC-stabilized 2-hydrophosphasilenes. © The Royal Society of Chemistry.Öğe Dianionic and Neutral Diboron-Centered Classical Diradicaloids(American Chemical Society, 2024) Elvers, Benedict J.; Das, Ayan; Chrysochos, Nicolas; Uddin, Sk Imraj; Gangber, Tejaswinee; Gangber, TejaswineeHerein, we report the syntheses and electronic structures of crystalline dianionic as well as neutral diboron-centered classical diradicaloids as boron analogues of classical Thiele, Chichibabin, and Müller (this only for dianionic diradicaloids!) hydrocarbons. These are based on borane radical anion and NHC-stabilized boryl radical spin carriers, respectively. All these dianionic diboron-centered diradicaloids exhibit triplet population at room temperature regardless of the ?-conjugated spacer: p-phenylene, p,p?-biphenylene, or p,p?-terphenylene. In the case of neutral diboron-centered diradicaloids, the employed ?-conjugated spacer plays a crucial role for the triplet population at room temperature: EPR inactive for p-phenylene vs EPR active for p,p?-biphenylene. The findings emphasize the importance of the spin carriers for the resulting ground-state: borane radical anion vs NHC-stabilized boryl radical along with the pivotal role of the ?-conjugated spacer as spin-coupler between two spins. Notably, 100 years (a century) after the first report by Krause of the triphenyl borane radical-anion, being isoelectronic to the triphenylmethyl radical, we convey borane radical anion-based diradicaloids. Furthermore, while donor-stabilized boryl radicals were introduced in the 1980s by Giles and Roberts, said concept is herewith being extended to NHC-stabilized boryl radical-based diradicaloids.Öğe NHC-stabilized 1-hydrosilaimine: Synthesis, structure and reactivity(Royal Society of Chemistry, 2017) Dhara, Debabrata; Vijayakanth, Thangavel; Barman, Milan Kr; Naik, Khevath Praveen Kumar; Chrysochos, Nicolas; Yıldız, Cem Burak; Boomishankar, Ramamoorthy; Schulzke, CarolaA facile, straightforward synthesis of N-heterocyclic carbene (NHC)-stabilized 1-hydrosilaimine starting from a silicon(iv)-precursor is reported. It has been employed for the addition of an O-H bond of water under ambient conditions without any additional catalyst. © 2017 The Royal Society of Chemistry.Öğe Realizing 1,1-Dehydration of secondary alcohols to carbenes: pyrrolidin-2-ols as a source of cyclic (Alkyl)(Amino)carbenes(Wiley-VCH Verlag, 2022) Daş, Ayan; Elvers, Benedict J.; Nayak, Mithilesh Kumar; Chrysochos, Nicolas; Anga, Srinivas; Kumar, Amar; Rao, D. Krishna; Narayanan, Tharangattu N.; Schulzke, Carola; Yıldız, Cem Burak; Jana, AnukulHerein we report secondary pyrrolidin-2-ols as a source of cyclic (alkyl)(amino)carbenes (CAAC) for the synthesis of CAAC-Cu-I-complexes and cyclic thiones when reacted with Cu-I-salts and elemental sulfur, respectively, under reductive elimination of water from the carbon(IV)-center. This result demonstrates a convenient and facile access to CAAC-based Cu-I-salts, which are well known catalysts for different organic transformations. It further establishes secondary alcohols to be a viable source of carbenes-realizing after 185 years Dumas' dream who tried to prepare the parent carbene (CH2) by 1,1-dehydration of methanol. Addressed is also the reactivity of water towards CAACs, which proceeds through an oxidative addition of the O-H bond to the carbon(II)-center. This emphasizes the ability of carbon-compounds to mimic the reactivity of transition-metal complexes: reversible oxidative addition and reductive elimination of the O-H bond to/from the C(II)/C(IV)-centre.
