Center for Magnetic Resonance

E.S. Yandanova, D.M. Ivanov, M.L. Kuznetsov, A.G. Starikov, G.L. Starova, V.Yu. Kukushkin

“Recognition of S···Cl Chalcogen Bonding in Metal-Bound Alkylthiocyanates”

Chem. Commun., 2016, 52, 5565
DOI:10.1021/acs.cgd.6b00346

Reaction of K₂[PtCl₄] with excess AlkSCN in water gives the alkylthiocyanate complexes trans-[PtCl₂(AlkSCN)₂] (Alk = Et 1, nPr 2; 80–85%). These species were studied, in particular, by X-ray crystallography. In the solid state, both 1 and 2 exhibit the previously unreported S···Cl chalcogen bonding, which consolidates the complexes into networks and leads to layered structures. Theoretical density functional theory calculations and Bader’s atoms in molecules analysis demonstrated two types of intermolecular interactions in tetramer (1)4, viz. the S···Cl chalcogen and the H···Cl hydrogen bonds. Despite that each particular S···Cl or H···Cl bonding is weak with the estimated energy of 1–2 kcal/mol, altogether they play a crucial role in the stabilization of the S₂Cl₂ fragment in (1)4, the basis set of superposition error corrected interaction energy being −12.8 kcal/mol per monomer complex molecule. The chalcogen bonding and the rhomboidal structure of the S₂Cl₂ fragment can be interpreted in terms of electrostatic arguments as a result of the interaction between the belt of negative electrostatic potential around the Cl atoms and the sulfur σ-holes. The natural bond orbital analysis revealed that both LP(S) → LP*(Pt)/σ*(Pt–N)/σ*(Pt–Cl) and LP(Cl) → σ*(S–C) types of hyperconjugative charge transfers are important in the chalcogen bonding.

D.M. Ivanov, A.S. Novikov, I.V. Ananyev, Y.V. Kirina, V.Yu. Kukushkin

“Halogen bonding between metal centers and halocarbons”

Chem. Commun., 2016, 52, 5565
DOI:10.1039/c6cc01107a

Metal-involving halogen bonding was detected in a series of associates of CHI₃ with trans-[PtX₂(NCNAlk₂)₂] (X = Cl, Br). The HI₂C–I⋯η¹(Pt) halogen bonding and the bifurcated HI₂C–I⋯η²(Pt–Cl) halogen bonding – the latter undergoes the thermally induced reversible HI₂C–I⋯η²(Pt–Cl) ⇄ HI₂C–I⋯η¹(Pt) transformation – were observed and confirmed theoretically.

D.M. Ivanov, P.V. Gushchin, A.S. Novikov, M.S. Avdontceva, A.A. Zolotarev, G.L. Starova, Y.-T. Chen, S.-H. Liu, P.-T. Chou, V.Yu. Kukushkin

“Platinum(II)-Mediated Double Coupling of 2,3-Diphenylmaleimidine with Nitrile Functionalities To Give Annulated Pentaazanonatetraenate (PANT) Systems”

Eur. J. Inorg. Chem., 2016, 1480–1487
DOI:10.1002/ejic.201501398

Treatment of trans-[PtCl2(NCR)2] [R = Et 1, nPr 2, tBu 3, CH2Ph 4, Ph 5, p-CF3C6H4 6, NMe2 7, NEt2 8, N(CH2)5 9] with 2.5 equiv. of 2,3-diphenylmaleimidine in CH2Cl2 at room temperature for 5 min [for R = p-CF3C6H4 6, NMe2 7, NEt2 8, N(CH2)5 9] or 14 h (for R = Et 1, nPr 2, tBu 3, CH2Ph 4, Ph 5) furnishes (1,3,5,7,9-pentaazanona-1,3,6,8-tetraenato) platinum(II) [(PANT)PtII; PtCl{HN=C(R)N=CN[C(Ph)=C(Ph)]C=NC(R)=NH}] complexes 10–18. These species are formed by platinum(II)-mediated double coupling of 2,3-diphenylmaleimidine with both nitrile ligands. The formulation of the complexes was supported by satisfactory C, H, and N elemental analyses, which were in agreement with HRESI-MS, IR, and 1H and 13C{1H} NMR spectra. The structures of 10, 11·1/8nC6H14, 15, 16·CCl4, and 17·CHCl3 were determined by single-crystal X-ray diffraction. Absorption and emission studies were performed on representative complexes 10, 15, and 18, and the results show weak phosphorescence maxima at around 730–750 and 770–820 nm in CH2Cl2 and in the solid state, respectively. Further insight into the photophysical properties was gained by time-dependent density functional theory (TD–DFT) with detailed analysis of the corresponding frontier molecular orbitals for the lower-lying transition. The calculated energies of the T1 state (in terms of wavelength) are 715.8 nm for 10, 764.6 nm for 15, and 697.7 nm for 18, and these values are in good agreement with the trend of the first vibronic peaks of their phosphorescence spectra.

M.A. Smirnov, M.P. Sokolova, N.V. Bobrova, I.A. Kasatkin, E. Lahderanta, G.K. Elyashevich

“Capacitance properties and structure of electroconducting hydrogels based on copoly(aniline e p-phenylenediamine) and polyacrylamide”

Journal of Power Sources, 2016, 304, 102-110
DOI:10.1016/j.jpowsour.2015.11.035

Electroconducting hydrogels (EH) based on copoly(aniline – p-phenylenediamine) grafted to the polyacrylamide for the application as pseudo-supercapacitor’s electrodes have been prepared. The influence of preparation conditions on the structure and capacitance properties of the systems were investigated: we determined the optimal amount of p-phenylenediamine to obtain the network of swollen interconnected nanofibrils inside the hydrogel which provides the formation of continuous conducting phase. Structure and morphology of the prepared samples were investigated with UVeVIS spectroscopy, scanning electron microscopy (SEM) and wide-angle X-ray diffraction (WAXD). The maximal value of capacitance was 364 F g^-1 at 0.2 A g^-1. It was shown that the EH samples demonstrate the retention of 50% of their capacity at high current density 16 A g^-1. Cycle-life measurements show evidence that capacitance of EH electrodes after 1000 cycles is higher than its initial value for all prepared samples. Changes of the copolymer structure during swelling in water have been studied with WAXD.

Y.S. Panova, A.S. Kashin, M.G. Vorobev, E.S. Degtyareva, V.P. Ananikov

“Nature of the Copper-Oxide-Mediated C−S Cross-Coupling Reaction: Leaching of Catalytically Active Species from the Metal Oxide Surface”

ACS Catal., 2016, 6, 3637−3643
DOI:10.1021/acscatal.6b00337

Copper-oxide-catalyzed cross-coupling reaction is a well-known strategy in heterogeneous catalysis. A large number of applications have been developed, and catalytic cycles have been proposed based on the involvement of the copper oxide surface. In the present work, we have demonstrated that copper(I) and copper(II) oxides served as precursors in the coupling reaction between thiols and aryl halides, while catalytically active species were formed upon unusual leaching from the oxide surface. A powerful cryo-SEM technique has been utilized to characterize the solution-state catalytic system by electron microscopy. A series of different experimental methods were used to reveal the key role of copper thiolate intermediates in the studied catalytic reaction. The present study shows an example of leaching from a metal oxide surface, where the leaching process involved the formation of a metal thiolate and the release of water. A new synthetic approach was developed, and many functionalized sulfides were synthesized with yields of up to 96%, using the copper thiolate catalyst. The study suggests that metal oxides may not act as an innocent material under reaction conditions; rather, they may represent a source of reactive species for solution-state homogeneous catalysis.