A set of N-coordinated tellurium(II) compounds containing either C,N-chelating ligands CNR (where CN = 2-(RNCH)C6H4, R = tBu or Dipp; Dipp = 2,6-iPr2C6H3) or N,C,N pincer ligands NCNR (where NCN = 2,6-(RNCH)2C6H4, R = tBu or Dipp) were synthesized. In the case of C,N-chelated compounds, the reaction of CNDippLi with Te(dtc)2 (where dtc = Et2NCS2) in a 1 : 1 molar ratio smoothly provided the carbamate CNDippTe(dtc) which upon treatment with 2 eq. of HCl provided the chloride CNDippTeCl. In contrast, the analogous conversion of NCNRLi with Te(dtc)2 surprisingly furnished ionic bromides [NCNRTe]Br as a result of the exchange of dtc by Br coming from nBuBr present in the reaction mixture. Furthermore, the reaction of CNDippTeCl or [NCNRTe]Br with silver salts AgX (X = OTf or SbF6) provided the expected tellurenium cations [CNDippTe]SbF6 and [NCNRTe]X. To further increase the Lewis acidity of the central atom, the oxidation of selected compounds with 1 eq. of SO2Cl2 was examined yielding stable compounds [CNtBuTeCl2]X and [NCNtBuTeCl2]X. The oxidation of the Dipp substituted compounds proved to be more challenging and an excess of SO2Cl2 was necessary to obtain the oxidized products [CNDippTeCl2]SbF6 and [NCNDippTeCl2]SbF6, which could solely be characterized in solution. Compounds [CNtBuTeCl2]OTf and [NCNtBuTeCl2]OTf were shown to undergo a controlled hydrolysis to the corresponding telluroxanes. All compounds were studied by multinuclear NMR spectroscopy in solution and for selected compounds solid state 125Te NMR spectroscopy and single-crystal X-ray diffraction analysis were performed. The Lewis acidity of the studied cations was examined by the Gutmann-Beckett method using Et3PO as the probing agent. The Te-N chalcogen bonding situation of selected compounds has also been examined computationally by a set of real-space bonding indicators.

• Publikační typ
• časopisecké články MeSH

The oxidative addition of CF3SO3CH2Si(CH3)3 (NpSiOTf) toward organopnictogen(I) N,C,N-pincer compounds, i.e. [2,6-(DippNCH)2C6H3]E (1-E, where E = Sb, Bi; Dipp = 2,6-iPr2C6H3) produced compounds [2,6-(DippNCH)2C6H3]E(NpSi)(OTf) (2-E, where E = Sb, Bi). By analogy, the in situ reduction of [2,6-(Me2NCH2)2C6H3]ECl2 (3-E, where E = Sb, Bi) followed by treatment with NpSiOTf or MeI gave compounds [2,6-(Me2NCH2)2C6H3]E(R)(X) (R/X = NpSi/OTf 4-E, where E = Sb, Bi; R/X = Me/I 5-Sb). The reactivity of these compounds toward 1 eq. of K[BEt3H] was examined showing remarkable differences depending both on the ligand backbone and the pnictogen used. Thus in the case of 2-E, the addition of the hydride across the imino-function was achieved thereby yielding azapnicta-heterocyclic compounds [2-(DippNCH2)-6-(DippNCH)C6H3]E(NpSi) (6-E, where E = Sb, Bi). The same reaction of 4-Bi produced dibismuthine {[2,6-(Me2NCH2)2C6H3]Bi(NpSi)}2 (7-Bi), but in the case of 4/5-Sb the analogous distibines {[2,6-(Me2NCH2)2C6H3]Sb(R)}2 (R = NpSi7-Sb, Me 8-Sb) were not formed directly and hydrides [2,6-(Me2NCH2)2C6H3]Sb(R)H (R = NpSi9-Sb, Me 10-Sb) could be isolated instead. Nevertheless, heating of both 9-Sb and 10-Sb led to an activation of a labile Sb-H bond and the formation of distibines 7/8-Sb.

• MeSH
• antimon chemie   MeSH
• bismut chemie   MeSH
• heterocyklické sloučeniny * MeSH
• organokovové sloučeniny * chemie   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• antimon MeSH
• bismut MeSH
• heterocyklické sloučeniny * MeSH
• organokovové sloučeniny * MeSH

The reactivity of two types of organopnictogen(I) N,C,N-pincer ligand coordinated compound, i.e. [2,6-(DippNCH)2C6H3]E (1-E, where E = As, Sb, Bi; Dipp = 2,6-iPrC6H3) and [2-(DippNCH)-6-(DippNHCH2)C6H3]E (6-E, where E = As or Sb), toward an electron-deficient alkyne, i.e. dimethyl acetylenedicarboxylate (DMAD), is reported. All reactions represent remarkable examples of element-ligand cooperation (ELC). In the first step, all compounds react via dearomatization of a latent heteropnictole ring producing rare examples of hetero Diels-Alder (DA) adducts. These compounds then smoothly convert to 1-arsanaphthalenes via hydrogen migration, thereby recovering the aromatic 10π-electron system. Furthermore, in the case of bis(imino) derivatives of 1-E, heating of DA adducts in pyridine led to a hydrogenation of the triple bond of DMAD with the concomitant recovery of the univalent pnictinidene centre, which is in turn able to activate the second molecule of DMAD. In contrast, the non-symmetric derivative of 6-As upon heating in pyridine produced bicyclic trivalent arsenic compounds as a result of an attack of the pendant secondary NH group into the arsa-heterocyclic system. For 6-Sb, a remarkable stoichiometric hydrogenation of the DMAD molecule was observed by NMR spectroscopy involving the reductive elimination of dimethylfumarate in the final step of the reaction sequence. The whole study is accompanied by a theoretical survey that describes the main thermodynamic parameters of the reported reactions and explains the reaction pathways observed in the experiments.

• Publikační typ
• časopisecké články MeSH

Lappert's stannylene (Sn[N(SiMe3)2]2) has been reacted with various nitriles, dinitriles and trinitriles with the formation of heteroleptic amidotin(II) amidinates of the general formulae [RC(NSiMe3)2]SnN(SiMe3)2, R'{[C(NSiMe3)2]SnN(SiMe3)2}2 and R''{[C(NSiMe3)2]SnN(SiMe3)2}3, where R = Ph (1), 2-(CN)-C6H4 (2), 3-(CN)-C6H4 (3); R' = 1,3-C6H4 (4), 1,4-C6H4 (5) and R'' = 1,3,5-C6H3 (6). The reactions of amidotin(II) benzamidinate 1 with an excess of benzonitrile proceed to homoleptic tin(II) bis(benzamidinate) [PhC(NSiMe3)2]2Sn, which reversibly eliminates benzonitrile and 1 when warmed. The premise of reversibility has been supported by a multinuclear time-dependent NMR study and a theoretical (DFT) description. On the other hand, magnesium(II) bis(benzamidinate) [PhC(NSiMe3)2]2Mg (8) and lanthanum(II) tris(benzamidinate) [PhC(NSiMe3)2]3La (7) have been synthesised from appropriate metal hexamethyldisilazides and benzonitrile.

• Publikační typ
• časopisecké články MeSH

2-Benzhydryl-4-methyl-6-(1,1'-diphenyl-2-phenyl-ethyl)aniline was prepared by a three-step process. 2,6-Bis(benzhydryl)-4-methyl-aniline was protected by Schiff coupling, then benzylated and finally dealkylated by using hydrochloric acid and methanol. The resulting compound exhibits one of the highest buried volumes around the nitrogen atom of anilines prepared so far, but it reacts with phosphorus trichloride and triethylamine to give a monomeric chloro(imino)phosphine.

• Publikační typ
• časopisecké články MeSH

The reactivity of two lithium amides derived from bis-(2-pyridyl)amine (dpa)H or its methyl-substituted congener bis-(6-methyl-2-pyridyl)amine (Me-dpa)H, i.e. (dpa)Li (1) and (Me-dpa)Li (2), toward ECl2 (where E = Ge (dioxane complex) and Sn) is reported. This study produced both heteroleptic complexes (dpa)GeCl (3), [(dpa)SnCl]2 (4), and (Me-dpa)GeCl (5) and homoleptic complexes (dpa)2E (E = Ge (6) or Sn (7)) and (Me-dpa)2E (E = Ge (8) or Sn (9)). The structures of all complexes were established by single-crystal X-ray diffraction analysis showing significant differences depending on the E atom and ligand used. By contrast, in solution, the majority of compounds showed a fluxional behaviour as demonstrated by the NMR study. Finally, it turned out that the Me-dpa ligand, unlike dpa, is able to form ate complexes [(Me-dpa)3E]Li (E = Ge (10), Sn (11) or Pb (12)), whose structures were determined by single-crystal X-ray diffraction analysis. This study revealed the formation of two isomers for Ge and Sn complexes depending on the coordination preference of the lithium atom being coordinated either by nitrogen donors (10-12) or solely by the Ge or Sn electron lone pair (10a and 11a). Furthermore, the NMR experiments proved that the germanium complex 10 exhibits only limited stability in solution and decomposes to germylene 8 and lithium amide 2.

• Publikační typ
• časopisecké články MeSH

Stannylenes of L2Sn type bearing either C,N-chelating (1, L = LCN = 2-(N,N-dimethylaminomethyl)phenyl) or bulky amido (2, L = LN = N(SiMe3)2) ligands react with cyanogen bromide (Br-C[triple bond, length as m-dash]N) via an oxidative-addition reaction to give monomeric six-coordinate (LCN)2Sn(Br)CN (1a) and four-coordinate (LN)2Sn(Br)CN (2a) stannanes in moderate yields. In solution, both 1a and 2a undergo instantaneous bromido-cyanido ligand redistribution reactions, leading to mixtures containing 1a, (LCN)2SnBr2 (1b) and (LCN)2Sn(CN)2 (1c) or 2a, (LN)2SnBr2 (2b) and (LN)2Sn(CN)2 (2c), respectively. The prepared species were characterised by multinuclear NMR spectroscopy in solution (1a-c and 2a-c) and in the solid state (1a-c). The crystal structures of 1a/b/c, 2a/b/c and sole 2b were determined by XRD analyses. DFT calculations and QTAIM analysis were also carried out to corroborate the experimental results.

• Publikační typ
• časopisecké články MeSH

Comparative studies of the synthesis of lithium guanidinates via nucleophilic addition of lithium amides to carbodiimides were performed. Four combinations of small or sterically crowded carbodiimide and sterically crowded lithium amide or lithium amide containing an adjacent amino donor group give ten different types of complexes. In particular, 2,6-[(CH3)2CH]2C6H3NHLi (DipNHLi, 1) reacts with (CH3)2CHN═C═NCH(CH3)2 upon the formation of the dissymmetric dimeric complex 2 with four-coordinate Li atoms. In contrast, 1 with DipN═C═NDip gives the mononuclear lithium guanidinate 3 with two-coordinate lithium by κ1-guanidinate, solvent molecule, and additional interaction with a π-electron cloud of one of the Dip groups. Analogous reactions of 2-[(CH3)2NCH2]C6H4NHLi (7) yield complexes 8 and 9, where the adjacent amino donors are always coordinated. Further deprotonation of 2, 3, 8, and 9 leads to dilithium guanidinates(2-)-4, 5, 10, and 11, among which only 5, containing three Dip groups, is monomeric with contacts to two π-electron systems of Dip groups. The rest of the complexes are tetranuclear with different structural patterns. In the central parts of molecules, toward which the nitrogen atoms of the guanidinates are oriented, lithium atoms are usually pseudotetrahedral, but trigonal in peripheral parts. Adjacent solvent molecules, chelating amino groups, and π-electron systems of Dip groups are coordinated in order to complete coordination polyhedra. Complexes 4 and 5 deoligomerize in solution upon the formation of fluxional monomeric dilithium species. Conversely, 11 is a dimer in solution due to the strong donation of an amino group. The silylated lithium amide {2-[(CH3)2NCH2]C6H4}[(Si(CH3)3]NLi (12) reacts with both carbodiimides to give dinuclear 13 obtained from diisopropylcarbodiimide and monomeric 14 from the second carbodiimide. Complexes 13 and 14 structurally resemble 8 and 9, with the highest degree of the localization of π-electron density within the N3C guanidinate system, η3-contact to the Dip ring, and a lack of the solvent molecule in 14.

• Publikační typ
• časopisecké články MeSH

The reactions of two equivalents of germylene [(i-Pr)2NB(N-2,6-Me2C6H3)2]Ge (1) with carbonyl compounds RC(O)R' resulted in carbonyl functionality activation and the formation of 4-(R,R')-1,2-digerma-3-oxa-cyclobutanes (R/R' = Ph/CF3 (2) or C6F5/H (3)). Surprisingly, the analogous reaction of 1 with C6F5C(O)Me led to the insertion of the germanium atom into the C-F bond of the perfluorophenyl group, thus producing a spiro compound (4) with a germanium atom sharing 1,2-digerma-3,5-diaza-4-bora-cyclopentane and 1-germa-2,4-diaza-3-boracyclobutane rings. Furthermore, the reaction of 1 with 2e- donors was investigated. In the case of 4-dimethylaminopyridine (DMAP), an expected complex [(i-Pr)2NB(N-2,6-Me2C6H3)2]Ge(DMAP) (5) was isolated, but using t-BuNC resulted in the formation of germanium(iv) cyanide [(i-Pr)2NB(N-2,6-Me2C6H3)2]Ge(CN)(t-Bu) (6) as a result of C-N bond activation in the starting isocyanide. In contrast, mixing other isocyanides RNC (R = Cy or Ad) with 1 in solution led only to an equilibrium between the starting compounds and most probably the corresponding complexes [(i-Pr)2NB(N-2,6-Me2C6H3)2]Ge(CNR) (R = Cy (7a) or Ad (8a)) based on NMR studies. From these equilibrium mixtures, fortuitously, single crystals of digerma-spiro-complexes (7 and 8) containing two germanium atoms (one of them coordinated to a particular isocyanide) were obtained and structurally authenticated by the X-ray diffraction technique.

• Publikační typ
• časopisecké články MeSH

Variously substituted 2,6-bis(1,1-diarylethyl)anilines and 2,6-bis(trityl)anilines were prepared by a three-step high-yield process. Dimethyl-2-aminoisophtalate was modified by reaction with arylmagnesium bromides, and the hydroxy-derivatives obtained were etherified. Under the non-catalysed C-C coupling protocol, the formed bis[methyl(methoxy)diaryl]anilines react with various Grignard reagents to give highly substituted products. The buried volumes around the central nitrogen atom of the prepared compounds exceed the parameters for the known most sterically hindered anilines by about 20%.

• Publikační typ
• časopisecké články MeSH