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Inorg Chem ; 59(23): 17565-17572, 2020 Dec 07.
Artigo em Inglês | MEDLINE | ID: mdl-33197182


The syntheses and XRD molecular structures of a complete series of silylsulfido metalates Cat[M(SSiMe3)2] (M = Cu, Ag, Au) and corresponding silylselenido metalates Cat[M(SeSiMe3)2] (M = Cu, Ag, Au) comprising lattice stabilizing organic cations (Cat = Ph4P+ or PPN+) are reported. Much to our surprise these homoleptic cuprates, argentates, and aurates are stable enough to be isolated even in the absence of any strongly binding phosphines or N-heterocyclic carbenes as coligands. Their metal atoms are coordinated by two silylchalcogenido ligands in a linear fashion. The silyl moieties of all anions show an unexpected gauche conformation of the silyl substituents with respect to the central axis Si-[E-M-E]-Si in the solid state. The energetic preference for the gauche conformation is confirmed by quantum chemical calculations and amounts to about 2-6 kJ/mol, thus revealing a rather shallow potential mainly depending on electronic effects of the metal. Furthermore, 2D HMQC methods were applied to detect the otherwise nonobservable NMR shifts of the 29Si and 77Se nuclei of the silylselenido compounds. Preliminary investigations reveal that these thermally and protolytically labile chalcogenido metalates are valuable precursors for the precipitation of binary coinage metal chalcogenide nanoparticles from organic solution and for coinage metal cluster syntheses.

Dalton Trans ; 49(8): 2517-2526, 2020 Feb 25.
Artigo em Inglês | MEDLINE | ID: mdl-32022066


Organic cation salts with homoleptic zincate and stannanide anions, Ph4P [Zn(ESiMe3)3] (E = S (1a), Se (1b)) and Cat [Sn(ESiMe3)3] (Cat = Ph4P+ (E = S (2a-Ph4P); Cat = PPN+ (E = S 2a-Ph4P, Se (2a)) are presented and structurally characterized. Efforts to isolate neutral thermally metastable stannane precursors [Sn(ESiMe3)4] (E = S (3), Se(4)) are reported as well. The thermal decomposition of the presented precursors to yield binary sulfides and selenides of zinc and tin is investigated. Furthermore, the potential of using the title anions as precursors in solution-based low-temperature synthesis of Cu2ZnSnS4 (CZTS) by coprecipitation with [Cu(tmtu)3]PF6 and subsequent annealing is discussed.

Inorg Chem ; 59(6): 3428-3436, 2020 Mar 16.
Artigo em Inglês | MEDLINE | ID: mdl-31967797


Phase-pure crystalline Bi2Se3 and Bi2Te3 nanoparticles are formed in reactions of [C4C1Im]3[Bi3I12] (C4C1Im = 1-butyl-3-methylimidazolium) with [C4C1Pyr][ESiMe3] (E = Se or Te; C4C1Pyr = 1-butyl-1-methylpyrrolidinium) in the ionic liquid (IL) [C4C1Im]I. The resulting crystalline tetradymite-type nanoparticles exhibit stoichiometric Bi:E (E = Se or Te) molar ratios (2:3). Because all synthetic steps were performed under strict inert gas conditions, the surfaces of the Bi2Se3 and Bi2Te3 nanoparticles are free of metal oxide species. As proven by infrared and X-ray photoelectron spectroscopy analyses, the nanoparticle surfaces reveal only minor organic contamination from solvent residues ([C4C1Im]I). The nanomaterials show high Seebeck coefficients of -124 µV K-1 (Bi2Se3) and -155 µV K-1 (Bi2Te3) and feature high electrical conductivities (328 and 946 S cm-1, respectively) at the highest tested temperature (240 °C). The corresponding thermal conductivities (0.8 and 2.3 W m-1 K-1, respectively, at 30 °C) are comparable to those of single crystals and recently reported ab initio calculations, which is in remarkable contrast to typical findings of nanograined bulk materials obtained from compacted nanoparticles. These findings emphasize the low level of impurities, surface contamination, and, in general, defects produced by the synthetic approach reported here. The figure of merit in the in-plane direction of the compacted pellets reached peak values 0.45 for Bi2Se3 and 0.4 for Bi2Te3.

Inorg Chem ; 58(22): 15385-15392, 2019 Nov 18.
Artigo em Inglês | MEDLINE | ID: mdl-31687815


We communicate the synthesis and full characterization of so far unknown tetrakis(trimethylsilylsulfido) and -(trimethylsilylselenido) gallates and indates in form of their organic salts Cat+[M(ESiMe3)4]- (M = Ga, In; E = S, Se; Cat = dimethylpyrrolidinium (DMPyr+), Ph4P+, (dppe)2Cu+, (dmpe)2Cu+). These thermally metastable silylchalcogenolatometalates can act as modular precursors for an ionic-liquid- or organic-solution-based low-temperature synthesis of multinary metal chalcogenide materials such as the CIGS species Cu(InxGa1-x)(SySe1-y)2.

Dalton Trans ; 48(29): 10971-10978, 2019 Aug 07.
Artigo em Inglês | MEDLINE | ID: mdl-31210231


We present convenient syntheses of so far inaccessible, crystalline and highly pure 1,3-dialkylimidazolium salts with extremely nucleophilic thiolate and selenolate anions [ER]- (R = H, tBu, SiMe3). While non existent for E = O, the title compounds exist as slightly less basic E = S and Se homologues. The anion cation H-bond interactions in the crystalline state have been studied systematically in six related ionic compounds of varying anion basicity and steric bulk, namely MMIm [SH] (1), MMIm [StBu] (2), and MMIm [SSiMe3] (3), as well as MMIm [SeH] (4), MMIm [SetBu] (5) and MMIm [SeSiMe3] (6). The chalcogenolate title compounds 3, 5, and 6 are prepared by the newly introduced method of desilylation of Me3Si-ER (E = S, Se) by the super-nucleophile MMIm [StBu] (2), which is easily accessible via deprotonation of HStBu with in situ generated NHC 1,3-dimethylimidazolidin-2-ylidene. Focus is put on the role of the most acidic imidazolium proton C2-H as structural director and as 1H NMR shift indicator. These salts show an unusually high volatility and tendency to sublime under vacuum without irreversible decay.

Chemistry ; 22(45): 16292-16303, 2016 Nov 02.
Artigo em Inglês | MEDLINE | ID: mdl-27717038


Depending on the amount of methanol present in solution, CO2 adducts of N-heterocyclic carbenes (NHCs) and N-heterocyclic olefins (NHOs) have been found to be in fully reversible equilibrium with the corresponding methyl carbonate salts [EMIm][OCO2 Me] and [EMMIm][OCO2 Me]. The reactivity pattern of representative 1-ethyl-3-methyl-NHO-CO2 adduct 4 has been investigated and compared with the corresponding NHC-CO2 zwitterion: The protonation of 4 with HX led to the imidazolium salts [NHO-CO2 H][X], which underwent decarboxylation to [EMMIm][X] in the presence of nucleophilic catalysts. NHO-CO2 zwitterion 4 can act as an efficient carboxylating agent towards CH acids such as acetonitrile. The [EMMIm] cyanoacetate and [EMMIm]2 cyanomalonate salts formed exemplify the first C-C bond-forming carboxylation reactions with NHO-activated CO2 . The reaction of the free NHO with dimethyl carbonate selectively led to methoxycarbonylated NHO, which is a perfect precursor for the synthesis of functionalized ILs [NHO-CO2 Me][X]. The first NHO-SO2 adduct was synthesized and structurally characterized; it showed a similar reactivity pattern, which allowed the synthesis of imidazolium methyl sulfites upon reaction with methanol.