Zdeňka Padělková

The Dominant Role of Chalcogen Bonding in the Crystal Packing of 2D/3D Aromatics

The chalcogen bond is a nonclassical σ-hole-based noncovalent interaction with emerging applications in medicinal chemistry and material science. It is found in organic compounds, including 2D aromatics, but has so far never been observed in 3D aromatic inorganic boron hydrides. Thiaboranes, harboring a sulfur heteroatom in the icosahedral cage, are candidates for the formation of chalcogen bonds. The phenyl-substituted thiaborane, synthesized and crystalized in this study, forms sulfur⋅⋅⋅π type chalcogen bonds. Quantum chemical analysis revealed that these interactions are considerably stronger than both in their organic counterparts and in the known halogen bond. The reason is the existence of a highly positive σ-hole on the positively charged sulfur atom. This discovery expands the possibilities of applying substituted boron clusters in crystal engineering and drug design.

Intramolecularly Coordinated Organotin Tellurides: Stable or Unstable?

The step-wise oxidation of an organotin(I) compound with elemental tellurium gave a variety of unprecedented organotin tellurides containing tin atoms in the oxidation states +II and +IV.

N,N′-Dibutylbarbituric acid as an acceptor moiety in push–pull chromophores

Twelve novel D–π–A chromophores with the N,N′-dibutylbarbituric acid acceptor, the N,N-dimethylamino donor and a systematically extended π-linker were synthesized. The extent of intramolecular charge-transfer, structure–property relationships and nonlinear optical properties were further investigated by X-ray analysis, electrochemistry, UV/Vis absorption spectra, calculations and EFISH experiments.

Tetrylenes chelated by hybrid amido-amino ligand: derivatives of 2-[(N,N-dimethylamino)methyl]aniline.

Reaction of 2-[(dimethylamino)methyl]aniline with butyllithium, followed by conversion with trimethylsilyl, triphenylsilyl, triphenylgermyl, trimethylstannyl, or tri-n-butylstannyl chloride, gives the corresponding substituted aniline. These compounds were further deprotonated by butyllithium and reacted with germanium, tin, and lead dichlorides, respectively, in both stoichiometric ratios 2:1 and 1:1, providing the target homo- ([2-(Me(2)NCH(2))C(6)H(4)(YR(3))N](2)M) and heteroleptic ([2-(Me(2)NCH(2))C(6)H(4)(YR(3))N]MCl) germylenes and stannylenes, where M = Ge, Sn, Y = Si, Ge, and R = Me, Ph. Unlike all of these cases, the heteroleptic plumbylene can only be obtained with this reaction when the amide is substituted by a trimethylsilyl moiety. Anilines substituted by trimethyltin or tri-n-butyltin moieties gave transmetalation products after the second deprotonation by butyllithium. The trimethyltin-substituted stannylenes could likewise not be obtained by hexamethyldisilazane elimination of (trimethylstannyl)-2-[(dimethylamino)methyl]aniline with 0.5 mol equiv of either bis[bis(trimethylsilyl)amido]tin or {bis[bis(trimethylsilyl)amido]tin chloride}. Products of these reactions are heterocubanes with compositions {[2-(Me(2)NCH(2))C(6)H(4)N]Sn}(4) and [2-(Me(2)NCH(2))C(6)H(4)N](2)(μ(2)-SnMe(2))(2), respectively, and Me(4)Sn or Me(3)SnCl. The structures of trimethylsilyl- and triphenylgermyl-substituted germylenes, stannylenes, and plumbylenes, as well as a number of their precursors, in the crystalline state, were investigated by X-ray diffraction and NMR spectroscopy in solution. Density functional theory methods were used for evaluation of the structures of several compounds.

Skeletal Alkylcarbonation (SAC) Reactions as a Simple Design for Cluster–Carbon Insertion and Cross‐Coupling: High‐Yield Access to Substituted Tricarbollides from 6,9‐Dicarba‐arachno‐decaborane(14)

The works by Brellochs and others on degradative insertion of the aldehyde carbon into the structure of the [6-HOarachno-B10H13] 2 dianion and some metal–carbonyl C-insertion reactions suggested that C=O carbon incorporation procedures might be, in principle, applicable to other cluster systems. To show that this synthetic approach is indeed viable, we report, herein, our preliminary results on a simple and convenient synthesis of the carbon-substituted elevenvertex nido tricarbaboranes (tricarbollides). The reactions are characterized by net inclusion of the C R vertex into the cluster of arachno-6,9-C2B8H14 through the acyl chloride C=O group, which results in an effective cross-coupling between R and the tricarbollide cage. Scheme 1 (path A) shows that reactions involving the arachno-6,9-C2B8H14 (1) dicarbaborane, [3] two equivalents of Et3N (in situ generator of [arachno-6,9-C2B8H13] (1 ) and HCl scavenger), NaH (H2O scavenger), and acyl chlorides RCOCl (exemplified by R=Me, Ph, and Naph (1-Naphthyl)), followed by treatment with aqueous NaOH, and precipitation with R4NCl (R=Me or Et) led to the isolation of a series of the monoanionic [8-R-nido-7,8,9-C3B8H10] compounds (2 ) (2 a : R=Me; 2 b : R= Ph; 2 c : R=Naph), which were isolated in yields up to 85 % (unoptimized, Table 1). The reactions of path A are in accord with the simplified stoichiometry of Equation (1), comprising the deprotonation of 1 along with Cl and H2O elimination.

Straightforward synthesis of novel cyclic metallasiloxanes supported by an N,C,N-chelating ligand

The reaction of an N,C,N-intramolecularly coordinated tin(IV) carbonate LSn(Ph)(CO3) (1) and antimony(III) and bismuth(III) oxides (LMO)2 (where M = Sb (2), Bi (3) and L = C6H3-2,6-(CH2NMe2)2) with (HO)SiPh2(O)SiPh2(OH) in 1 : 1 (in the case of 1) or 1 : 2 molar ratio (in the cases of 2 and 3) gave the metallasiloxanes cyclo-LSn(Ph)(OSiPh2)2O (4) and cyclo-LM(OSiPh2)2O (where M = Sb (6) and Bi (7)) containing six-membered MSi2O3 rings. Alternatively, the compounds 4, 6 and 7 can be also prepared reacting Ph2Si(OH)2 and compounds 1, 2 and 3, respectively, in the molar ratio of either 2 : 1 (for 4) or 4 : 1 (for 6 and 7). The reaction of Ph2Si(OH)2 with 1 in 1 : 1 molar ratio gave cyclo-Ph2Si(OSnL(Ph)O)2SiPh2 (5) containing an eight-membered Sn2Si2O4 stannasiloxane ring. The analogous eight-membered stibasiloxane derivative cyclo-Ph2Si(OSbLO)2SiPh2 (8) was obtained as well, while attempts to synthesize the bismuth analogue failed. Compounds 1-3 react with the siloxane cyclo-(Me2SiO)3 providing either eight-membered metallasiloxanes cyclo-LSn(Ph)(OSiMe2O)2SiMe2 (9) and cyclo-LSb(OSiMe2O)2SiMe2 (10) or the six-membered bismutasiloxane cyclo-LBi(OSiMe2)2O (11). All compounds were characterized with the help of elemental analysis, (1)H, (13)C, (29)Si and (119)Sn NMR spectroscopy, and single crystal X-ray diffraction analyses (except 9 and 10).

Self-assembled hydrogen-bonded coordination networks in two copper(II) carboxylates with 4-pyridylmethanol

The crystal and molecular structure of [Cu(nif)2(4-PM)2]·CH3OH (1) and [Cu(2-Clbz)2(4-PM)2(H2O)] (2), (where nif = niflumate anion, 2-Clbz = 2-chlorobenzoate anion and 4-PM is the 4-pyridylmethanol), have been determinated by X-ray crystallography. The Cu2+ cation in (1), is coordinated by two pairs of oxygen atoms from asymmetric bidentate niflumate anions and by a pair of pyridine nitrogen atoms from monodentate 4-pyridylmethanol ligands in trans position forming an extremely elongated bipyramid. The Cu2+ cation in (2), is coordinated by a pair of oxygen atoms from monodentate 2-chlorobenzoate anions, further by a pair of pyridine nitrogen atoms from monodentate 4-pyridylmethanol ligands and finally by a water oxygen atom forming a tetragonal-pyramidal coordination polyhedron. The molecules of both complexes in crystal structures are linked by O-H…O hydrogen bonds, which created a three-dimensional hydrogen-bonding networks. The Π-Π stacking interactions are also observed in crystal structures of complex 2. The spectral properties (IR and electronic spectra) of both complexes were also investigated.

Aryl ethyl ethers prepared by ethylation using diethyl carbonate

Abstract An environmentally more convenient reaction for the production of industrially important aryl ethyl ethers (ArOEts) is described. ArOEts were selectively obtained in essentially quantitative yields by the reaction of corresponding (hetero)aromatic alcohols (ArOHs) with diethyl carbonate as the environmentally friendly alkylating reagent in the presence of N,N-dimethylacetamide used as polar aprotic cosolvent, and sodium ethoxide as the base. The reactions were carried out in the air under atmospheric pressure at 137°C. Reaction equilibrium was shifted by distilling the ethanol from the reaction mixture. All ArOEts were isolated by evaporation of the reaction mixture, and subsequent extraction with water and diethoxymethane. The ethylation agent and used solvents were non-toxic, recyclable and biologically degradable. Wastewater from the extraction was successfully treated by Fenton oxidation and returned to the next work-up process.

Structure of β-diketiminates and β-aminoketones made from anisidines or chloroanilines: tin and lithium complexes

Abstract Three series of methoxyphenyl substituted β-diketiminate and β-enaminoketonate and chlorophenyl β-enaminoketonate ligands were prepared and studied by IR, 1H and 13C NMR spectroscopy in solution and X-ray diffraction techniques in solid state. The crystal structures of [2-(MeO)C6H4]N=(H)-CCH(H)C[2-(MeO)C6H4]NH.HCl,[2-(MeO)C6H4]N=(H)CCH(H)C[2-(MeO)C6H4]NH, [4-(MeO)C6H4]N=(H)CCH-(H)C[4-(MeO)C6H4]NH, [4-ClC6H4]N(H)(Me)CCH(Me)C=O, [2-(MeO)C6H4]N=(Me)CCH(Me)C[2-(MeO)C6H4]NH and 7-methoxy-2,4-dimethylquinoline-toluenesulfonylacid adduct as ligands, their precursors and a byproduct isolated during the synthesis of [3-(MeO)C6H4]N(H)(Me)CCH(Me)C=O were determined. One of the ligands the meta-methoxyphenyl substituted β-enaminone has been treated with n-butyllithium to give {[3-ClC6H4]N(Me)CCH(Me)C=O}Li which reveals tetrameric structure in the solid state. Further reactions of this lithium complex with tri- and diorganotin(IV) chlorides and hydride give appropriate organotin(IV) complexes with five coordinated tin atom. The direct reaction of bis(para-methoxyphenyl) substituted β-diketimine with Sn[N(SiMe3)2]2 gives [4-(MeO)C6H4]N=(H)CCH(H)C[4-(MeO)C6H4]NSnN(SiMe3)2. Structure of these complexes was evaluated by 1H, 7Li and 119Sn NMR spectroscopy and X-ray diffraction analysis for two examples.

Synthesis of All Configurational Isomers of 1,6-Anhydro-2,3,4-trideoxy-2,3-epimino-4-fluoro-β-d-hexopyranoses

We have prepared a full series of 1,6-anhydro-2,3,4-trideoxy-4-fluoro-2,3-epimino-beta-d-hexopyranoses. The key step was the reaction of azido sulfonates possessing a free C-4 hydroxyl with DAST and subsequent LiAlH(4) reduction. Nucleophilic displacement of the hydroxyl activated by DAST proceeded without rearrangement and with moderate to good yields. A convenient synthesis of d-mannoepimine from a readily available 3-benzylamino derivative was also developed.