Trapping a silicon(I) radical with carbenes: a cationic cAAC-silicon(I) radical and an NHC-parent-silyliumylidene cation

The trapping of a silicon(I) radical with N-heterocyclic carbenes is described. The reaction of the cyclic (alkyl)(amino) carbene [cAACMe] (cAACMe=:C(CMe2)2(CH2)NAr, Ar=2,6-iPr2C6H3) with H2SiI2 in a 3:1 molar ratio in DME afforded a mixture of the separated ion pair [(cAACMe)2Si:.]+I− (1), which features a cationic cAAC–silicon(I) radical, and [cAACMe−H]+I−. In addition, the reaction of the NHC–iodosilicon(I) dimer [IAr(I)Si:]2 (IAr=:C{N(Ar)CH}2) with 4 equiv of IMe (:C{N(Me)CMe}2), which proceeded through the formation of a silicon(I) radical intermediate, afforded [(IMe)2SiH]+I− (2) comprising the first NHC–parent-silyliumylidene cation. Its further reaction with fluorobenzene afforded the CAr−H bond activation product [1-F-2-IMe-C6H4]+I− (3). The isolation of 2 and 3 confirmed the reaction mechanism for the formation of 1. Compounds 1–3 were analyzed by EPR and NMR spectroscopy, DFT calculations, and X-ray crystallography

MTV - Magdeburg Tool for Videoconferences

MTV is a software tool (citeware) for economic experiments facilitating researchers to gather video data from communication-based experiments in a way that these can be later used for automatic analysis through machine learning techniques. The browser-based tool comes with an easy user interface and can be easily integrated in z-Tree or oTree. It provides the experimenters control about several communication parameters (e.g., number of participants, duration), produces high-quality video data, and circumvents the Cocktail Party Problem by producing separate audio files. Using some of the recommended Voice-to-Text AI, the experimenters can transcribe individual audio files. MTV can merge these individual transcriptions to one conversation. This paper describes the underlying principles of the tool, technical requirements, possible areas of application, and current limitations

Direct functionalization of white phosphorus with anionic dicarbenes and mesoionic carbenes: facile access to 1,2,3-triphosphol-2-ides

Rottschäfer D, Blomeyer S, Neumann B, Stammler H-G, Ghadwal R. Direct functionalization of white phosphorus with anionic dicarbenes and mesoionic carbenes: facile access to 1,2,3-triphosphol-2-ides. CHEMICAL SCIENCE. 2019;10(48):11078-11085.A series of unique C2P3-ring compounds [(ADC(Ar))P-3] (ADC(Ar) = ArC{(DippN)C}(2); Dipp = 2,6-iPr(2)C(6)H(3); Ar = Ph 4a, 3-MeC(6)H(4)4b, 4-MeC(6)H(4)4c, and 4-Me(2)NC(6)H(4)4d) are readily accessible in an almost quantitative yield by the direct functionalization of white phosphorus (P-4) with appropriate anionic dicarbenes [Li(ADC(Ar))]. The formation of 1,2,3-triphosphol-2-ides (4a-4d) suggests unprecedented [3 + 1] fragmentation of P-4 into P-3(+) and P-. The P-3(+) cation is trapped by the (ADC(Ar))(-) to give 4, while the putative P- anion reacts with additional P-4 to yield the Li3P7 species, a useful reagent in the synthesis of organophosphorus compounds. Remarkably, the P-4 fragmentation is also viable with the related mesoionic carbenes (iMICs(Ar)) (iMIC(Ar) = ArC{(DippN)(2)CCH}, i stands for imidazole-based) giving rise to 4. DFT calculations reveal that both the C3N2 and C2P3-rings of 4 are 6 pi-electron aromatic systems. The natural bonding orbital (NBO) analyses indicate that compounds 4 are mesoionic species featuring a negatively polarized C2P3-ring. The HOMO-3 of 4 is mainly the lone-pair at the central phosphorus atom that undergoes sigma-bond formation with a variety of metal-electrophiles to yield complexes [{(ADC(Ar))P-3}M(CO)(n)] (M = Fe, n = 4, Ar = Ph 5a or 4-Me-C(6)H(4)5b; M = Mo, n = 5, Ar = Ph 6; M = W, n = 5, Ar = 4-Me(2)NC(6)H(4)7)

Isolation of singlet carbene derived 2-phospha-1,3-butadienes and their sequential one-electron oxidation to radical cations and dications

A synthetic strategy for the 2-phospha-1,3-butadiene derivatives [{(IPr)C(Ph)}P(cAAC$^{Me}$)] (3a) and [{(IPr)C(Ph)}P(cAAC$^{Cy}$)] (3b) (IPr = C{(NDipp)CH}$_{2}$, Dipp = 2,6-iPr$_{2}$C$_{6}$H$_{3}$; cAAC$^{Me}$ = C{(NDipp)CMe$_{2}$CH$_{2}$CMe$_{2}$}; cAAC$^{Cy}$ = C{(NDipp)CMe$_{2}$CH$_{2}$C(Cy)}, Cy = cyclohexyl) containing a C=C–P=C framework has been established. Compounds 3a and 3b have a remarkably small HOMO–LUMO energy gap (3a: 5.09; 3b: 5.05 eV) with a very high-lying HOMO (-4.95 eV for each). Consequently, 3a and 3b readily undergo one-electron oxidation with the mild oxidizing agent GaCl$_{3}$ to afford radical cations [{(IPr)C(Ph)}P(cAAC$^{R}$)]GaCl$_{4}$ (R = Me 4a, Cy 4b) as crystalline solids. The main UV-vis absorption band for 4a and 4b is red-shifted with respect to that of 3a and 3b, which is associated with the SOMO related transitions. The EPR spectra of compounds 4a and 4b each exhibit a doublet due to coupling of the unpaired electron with the $^{31}$P nucleus. Further oneelectron removal from the radical cations 4a and 4b is also feasible with GaCl$_{3}$, affording the dications [{(IPr)C(Ph)}P(cAAC$^{R}$)](GaCl$_{4}$)$_{2}$ (R = Me 5a, Cy 5b) as yellow crystals. The molecular structures of compounds 3–5 have been determined by X-ray diffraction and analyzed by DFT calculations

Alkali-metal-mediated zincation (AMMZn) meets N-heterocyclic carbene (NHC) chemistry : Zn–H exchange reactions and structural authentication of a dinuclear Au(I) complex with a NHC anion

Merging two evolving areas in synthesis, namely cooperative bimetallics and N-heterocyclic carbenes (NHCs), this study reports the isolation of the first intermediates of alkali-metal-mediated zincation (AMMZn) of a free NHC and a Zn–NHC complex using sodium zincate [(TMEDA)NaZn(TMP)(tBu)2] (1) as a metallating reagent. The structural authentication of (THF)3Na[:C{[N(2,6-iPr2C6H3)]2CHCZn(tBu2)}] (2) and [Na(THF)6]+[tBu2Zn:C{[N(2,6-iPr2C6H3)]2CHCZn(tBu2)}]− (4), resulting from the reactions of 1 with unsaturated free NHC IPr (IPr = 1,3-bis(2,6-di-isopropylphenylimidazole-2-ylidene) and NHC complex ZntBu2IPr (3) respectively demonstrates that in both cases, this mixed-metal approach can easily facilitate the selective C4 zincation of the unsaturated backbone of the NHC ligand. Furthermore, the generation of anionic NHC fragments enables dual coordination through their normal (C2) and abnormal (C4) positions to the bimetallic system, stabilising the kinetic AMMZn intermediates which normally go undetected and provides new mechanistic insights in to how these mixed-metal reagents operate. In stark contrast to this bimetallic approach when NHC-complex 3 is reacted with a more conventional single-metal base such as tBuLi, the deprotonation of the coordinated carbene is inhibited, favouring instead, co-complexation to give NHC-stabilised [IPr·LiZntBu3] (5). Showing the potential of 2 to act as a transfer agent of its anionic NHC unit to transition metal complexes, this intermediate reacts with two molar equivalents of [ClAu(PPh3)] to afford the novel digold species [ClAu:C{[N(2,6-iPr2C6H3)]2CHCAu(PPh3)}] (6) resulting from an unprecedented double transmetallation reaction which involves the simultaneous exchange of both cationic (Na+) and neutral (ZntBu2) entities on the NHC framework

Expanding the scope of Cu(I) Catalyzed “Click Chemistry” with abnormal NHCs: three-fold click to Tris-Triazoles

Ho NKT, Reichmann SO, Rottschäfer D, Herbst-Irmer R, Ghadwal R. Expanding the scope of Cu(I) Catalyzed “Click Chemistry” with abnormal NHCs: three-fold click to Tris-Triazoles. Catalysts. 2017;7(9): 262.Cationic copper(I) complexes [Cu(aIPrPh)(IPr)]I (3) and [Cu(aIPrPh)2]I (4) featuring an abnormal N-heterocyclic carbene (aNHC) (aIPrPh = 1,3-bis(2,6-diisopropylphenyl)-2-phenyl- imidazol-4-ylidene) and/or an NHC (IPr = 1,3-Bis(2,6-diisopropylphenyl)imidazol-2-ylidene) ligand(s) are reported. Treatment of Cu(aIPrPh)I (2) with IPr affords complex 3. Reaction of (IPrPh)I (1) (IPrPh = 1,3-bis(2,6-diisopropylphenyl)-2-phenyl-imidazolium) with CuI in the presence of K{N(SiMe3)2} leads to the formation of 4. Complexes 3 and 4 represent rare examples of mixed aNHC-NHC and bis-aNHC metal complexes, respectively. They are characterized by elemental analysis, NMR spectroscopic, and mass spectrometric studies. The solid-state molecular structures of 3 and 4 have been determined by single crystal X-ray diffraction analyses. The catalytic activity of 2, 3, and 4 has been investigated in the [3+2] cycloaddition of alkynes and organic azides, affording triazole derivatives in an almost quantitative yield. Notably, complexes 2, 3, and 4 are excellent catalysts for the three-fold cycloaddition of a tris-azide with various alkynes. This catalytic protocol offers a high yield access to tris-triazoles in a shorter reaction time and considerably reduces the experimental work-up compared to the classical synthetic method