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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 Contrasting reactivity of (boryl)(aryl)lithium-amide with electrophiles: N- vs. p-aryl-C-nucleophilic substitution(Royal Society of Chemistry, 2018) Dhara, Debabrata; Vijayakanth, Thangavel; Nayak, Mithilesh Kumar; Kalita, Pankaj; Boomishankar, Ramamoorthy; Yıldız, Cem Burak; Chandrasekhar, Vadapalli; Jana, AnukulHerein we report two different reactivity modes of lithium(aryl)(boryl)amide, 4, when it is reacted with chlorosilanes such as SiCl4 and MeSiHCl2, and chlorophosphine, Ph2PCl. Thus, the reaction of lithium(aryl)(boryl)amide, 4, with MeSiHCl2 leads exclusively to an N-substitution product, 6. On the other hand, the reaction of 4 with SiCl4 and Ph2PCl proceeds completely differently affording exclusively p-aryl-C-substitution products, 5 and 7, respectively. © 2018 The Royal Society of Chemistry.Öğe ?,??-Diamino-p-quinodimethanes with three stable oxidation states(American Chemical Society, 2020) Mahata, Alok; Chandra, Shubhadeep; Maiti, Avijit; Rao, D. Krishna; Yıldız, Cem Burak; Sarkar, Biprajit; Jana, AnukulHerein, we report the rational design, synthesis, and characterization of ?,??-diamino-substituted-p-quinodimethanes, which are a group of partially substituted p-quinodimethanes. These exhibit two reversible one-electron redox steps and electrochromism in the ultraviolet, visible, and near-infrared regions. We were able to isolate the crystalline compounds of all three oxidation states: neutral, radical cation, and dication. The obtained results not only create the bridge between p-quinodimethane and ?,?,??,??-tetrasubstituted-p-quinodimethane, but also demonstrate the straightforward modular approach for the synthesis of ?-conjugated open-shell compounds.Öğe Dimerization of a marginally stable disilenyl germylene to tricyclic systems: evidence for reversible NHC-coordination(Royal Soc Chemistry, 2016) Nieder, David; Yıldız, Cem Burak; Jana, Anukul; Zimmer, Michael; Huch, Volker; Scheschkewitz, DavidTetrasiladigermatricyclohexanes in two isomeric forms (chair and doubly-bridged tetrahedron) are obtained by the reaction of MeLi with an alpha-chlorosilyl functionalized NHC-stabilized silagermenylidene. Si-29 NMR at low temperature proves the initial formation of a monomeric NHC-adduct of a disilenyl germylene followed by cyclisation to the isomeric heavy cyclopropene. Addition of an excess of NHC stabilizes the both intermediates and demonstrates the reversibility of rate-determining initial equilibria involving NHC dissociation. Finally, a mixture of two isomeric tricyclic Si4Ge2 species is obtained: at elevated temperature the chair isomer converts to the doubly edge-bridged tetrahedron.Öğe Disclosing Cyclic(Alkyl)(Amino)Carbenes as a One-Electron Reductant: Synthesis of Acyclic(Amino)(Aryl)Carbene-Based Kekulé Diradicaloids(Wiley, 2023) Maiti, Avijit; Elver, Benedict J.; Bera, Sachinath; Lindl, Felix; I-Krummenacher, Ivo; Krummenacher, Ivo; Ghosh, Prasanta; Yıldız, Cem Burak; Braunschweig, Holger; Schulzke, Carola; Jana, AnukulHerein we disclose cyclic(alkyl)(amino)carbenes (CAACs) as a one-electron reductant under the formation of a transient radical cation as indicated by EPR spectroscopy. Subsequently, the disclosed CAAC reducing reactivity was utilized for the synthesis of acyclic(amino)(aryl)carbene-based Thiele and Chichibabin hydrocarbons, a new class of Kekulé diradicaloids. The results demonstrate the CAAC to be a potent organic reductant. Notably, the acyclic(amino)(aryl)carbene-based Chichibabin's hydrocarbon shows an appreciable population of the triplet state at room temperature, as evidenced by both variable temperature NMR and EPR spectroscopy.Öğe Reactivity of NHC/diphosphene-coordinated Au(i)-hydride(Royal Society of Chemistry, 2021) Dhara, Debabrata; Scheschkewitz, David; Chandrasekhar, Vadapalli; Yıldız, Cem B.; Jana, AnukulWe report the reactivity of isolable Au(i)-hydride stabilized by an NHC-coordinated diphosphene towards substrates containing C-C and N-N multiple bonds (NHC = N-heterocyclcic carbene). Reactions with dimethyl acetylenedicarboxylate and azobenzene lead to a trans-addition of the Au(i)-H across the C-C triple bond and the N-N double bond, respectively. In contrast, the reaction with ethyl diazoacetate affords a gold(i)-hydrazonide as the 1,1-addition product to the terminal nitrogen atom. With phenyl acetylene, the corresponding Au(i)-alkynyl complex is obtained under the elimination of dihydrogen. Strikingly, diphosphene-containing Au(i)-hydride is more reactive-affording different products in some cases-than a related NHC-stabilized Au(i)-hydride without the mediating diphosphene moiety.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.Öğe Reduction of 2-H-substituted pyrrolinium cations: the carbon-carbon single bond in air stable 2,2?-bipyrrolidines as a two-electron-source(Royal Society of Chemistry, 2023) Nayak, Mithilesh Kumar; Elvers, Benedict J.; Mandal, Debdeep; Das, Ayan; Ramakrishnan, Raghunathan; Mote, Kaustubh R.; Schulzke, Carola; Yıldız, Cem Burak; Jana, AnukulReduction of 2-H-substituted pyrrolinium cations via initially formed secondary radicals results in either dimerisation or H-abstracted products, while the outcome depends on the N-substituents. The resultant central carbon-carbon single bond in the dimerised 2,2?-bipyrrolidine derivatives can be oxidised chemically and electrochemically. The notably air and moisture-stable dimers were subsequently utilised as a source of two electrons in various chemical transformations.Öğe Reply to the ‘Comment on “The oxidation state in low-valent beryllium and magnesium compounds”’ by S. Pan and G. Frenking, Chem. Sci., 2022, 13, DOI: 10.1039/D2SC04231B(Royal Society of Chemistry, 2023) Gimferrer, Martí; Danés, Sergi; Vos, Eva; Yıldız, Cem Burak; Corral, Inés; Jana, Anukul; Salvador, Pedro; Andrada, Diego M.A recent article by Pan and Frenking challenges our assignment of the oxidation state of low valent group 2 compounds. With this reply, we show that our assignment of Be(+2) and Mg(+2) oxidation states in Be(cAACDip)2 and Mg(cAACDip)2 is fully consistent with our data. Some of the arguments exposed by Pan and Frenking were based on visual inspection of our figures, rather than a thorough numerical analysis. We discuss with numerical proof that some of the statements made by the authors concerning our reported data are erroneous. In addition, we provide further evidence that the criterion of the lowest orbital interaction energy in the energy decomposition analysis (EDA) method is unsuitable as a general tool to assess the valence state of the fragments. Other indicators based on natural orbitals for chemical valence (NOCV) deliver a more reliable bonding picture. We also emphasize the importance of using stable wavefunctions for any kind of analysis, including EDA.Öğe The oxidation state in low-valent beryllium and magnesium compounds(The Royal Society of Chemistry, 2022) Gimferrer, Marti; Danes, Sergi; Vos, Eva; Yıldız, Cem Burak; Corral, Ines; Jana, Anukul; Salvador, Pedro; Andrada, Diego M.Low-valent group 2 (E = Be and Mg) stabilized compounds have been long synthetically pursued. Here we discuss the electronic structure of a series of Lewis base-stabilized Be and Mg compounds. Despite the accepted zero(0) oxidation state nature of the group 2 elements of some recent experimentally accomplished species, the analysis of multireference wavefunctions provides compelling evidence for a strong diradical character with an oxidation state of +2. Thus, we elaborate on the distinction between a description as a donor-acceptor interaction L(0) ? E(0) reversible arrow L(0) and the internally oxidized situation, better interpreted as a diradical L(-1) -> E(+2) <- L(-1) species. The experimentally accomplished examples rely on the strengthened bonds by increasing the pi-acidity of the ligand; avoiding this interaction could lead to an unprecedented low-oxidation state.
