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649 results on '"Dostál, Libor"'

201. Homolytic, Heterolytic, Mesolytic - As You Like It: Steering the Cleavage of a HC(sp3)−C(sp3)H Bond in Bis(1 H-2,1-benzazaborole) Derivatives.

Author

Hejda, Martin, Lyčka, Antonín, Mikysek, Tomáš, Jambor, Roman, Růžička, Aleš, Vinklárek, Jaromír, Wilfer, Claudia, Hoffmann, Alexander, Herres‐Pawlis, Sonja, and Dostál, Libor

Subjects
CARBON-hydrogen bonds, NUCLEAR magnetic resonance, X-ray diffraction, ALKALI metal compounds, BORATES
Abstract

A set of (3,3′)-bis(1-Ph-2-R-1 H-2,1-benzazaborole) compounds, in which R= tBu (Bab- tBu)2, R=Dipp (Bab-Dipp)2 or R= tBu and Dipp (Bab-Dipp)(Bab- tBu), was synthesized and fully characterized using 1H, 11B, 13C, and 15N NMR spectroscopy as well as single-crystal X-ray diffraction analysis. The central HC(sp3)−C(sp3)H bond with restricted rotation at the junction of both 1 H-2,1-benzazaborole rings displayed an intriguing reactivity. It was demonstrated that this bond is easily mesolytically cleaved using alkali metals to form the respective aromatic 1Ph-2R-1 H-2,1-benzazaborolyl anions M+(THF) n (Bab- tBu)− (M=Li, Na, K) and K+(THF) n (Bab-Dipp)−. Furthermore, the central HC(sp3)−C(sp3)H bond of bis(1 H-2,1-benzazaborole)s is also homolytically cleaved either by heating or photochemical means, giving corresponding 1Ph-2R-1 H-2,1-benzazaborolyl radicals (Bab- tBu). and (Bab-Dipp)., which rapidly self-terminate. Nevertheless, their formation was unambiguously established by NMR analysis of the reaction mixtures containing products of the self-termination of the radicals after heating or irradiation. (Bab-Dipp). radical was also characterized using EPR spectroscopy. Importantly, it turned out that the essentially non-polarized HC(sp3)−C(sp3)H bond in (Bab- tBu)2 is also cleaved heterolytically with 2 equiv of MeLi, giving the mixture of Li+(SOL) n (Bab- tBu)− (SOL=THF or Et2O) and lithium methyl-substituted borate complex Li+(SOL) n (Bab- tBu-Me)− in a diastereoselective fashion. [ABSTRACT FROM AUTHOR]

Published
2016
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202. Synthesis and Structure of ( N,) C, N-chelated Organoantimony(III) and Bismuth(III) Cations and Isolation of Their Adducts with Ag[CB11H12].

Author

Vránová, Iva, Erben, Milan, Jambor, Roman, Růžička, Aleš, Jirásko, Robert, and Dostál, Libor

Subjects
AGOSTIC interaction, ORGANOANTIMONY compounds, BISMUTH compounds, CHEMICAL synthesis, ANTIMONY compound synthesis, CATIONS, CARBORANE synthesis
Abstract

The treatment of N,C,N-chelated antimony(III) and bismuth(III) chlorides [C6H3-2,6-(CH=N R)2] MCl2 [ R = tBu and M = Sb ( 1) or Bi ( 2); R = Dmp and M = Sb ( 3) or Bi ( 4)] (Dmp = 2,6-Me2C6H3) with one molar equivalent of Ag[CB11H12] led to a smooth formation of corresponding ionic pairs {[C6H3-2,6-(CH=N R)2] MCl}+[CB11H12]- [ R = tBu and M = Sb ( 7) or Bi ( 8), R = Dmp and M = Sb ( 9) or Bi ( 10)]. Similarly, the reaction of C,N-chelated analogues [C6H2-2-(CH=NDip)-4,6-( tBu)2] MCl2 [ M = Sb ( 5) or Bi ( 6), Dip = 2′,6′- iPr2C6H3] gave compounds {[C6H2-2-(CH=NDip)-4,6-( tBu)2]MCl}+[CB11H12]- [ M = Sb ( 11) or Bi ( 12)]. All compounds 7- 12 were characterized with 1H, 11B and 13C{1H} NMR spectroscopy, ESI-mass spectrometry, IR spectroscopy, and molecular structures of 7- 9 and 12 were determined by the help of single-crystal X-ray diffraction analysis. In contrast, all attempts to cleave also the second M-Cl bond in 7- 12 using another molar equivalent Ag[CB11H12] remained unsuccessful. Nevertheless, the reaction between 7 (or 8) and Ag[CB11H12] produced unprecedented adducts of both reagents namely {[C6H3-2,6-(CH=N tBu)2]SbCl}22+[Ag2(CB11H12)4]2- ( 13) and {[C6H3-2,6-(CH=N tBu)2]BiCl}+[Ag(CB11H12)2]- ( 14) in a reproducible manner. The molecular structures of these sparingly soluble compounds were determined by single-crystal X-ray diffraction analysis. [ABSTRACT FROM AUTHOR]

Published
2016
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203. Germylenes and stannylenes stabilized within N2PE rings (E = Ge or Sn): combined experimental and theoretical study.

Author

Vrána, Jan, Ketkov, Sergey, Jambor, Roman, Růžička, Aleš, Lyčka, Antonín, and Dostál, Libor

Subjects
PROTON transfer reactions, PHOSPHINES, GERMYLENES, STOICHIOMETRY, LITHIUM compounds
Abstract

The deprotonation of aminophosphanes PhP(NHR)2 (R = t-Bu or Dip; Dip = 2,6-i-Pr2C6H3) and t-BuP(NHDip)2 using n-BuLi gave, depending on the stoichiometry, both the dilithium compounds {[PhP(Nt-Bu)2]Li2}2 (1), [PhP(Nt-Bu)(NDip)]Li2·(Et2O) (3), [t-BuP(NDip)2]Li2·(Et2O)2 (5) and [t-BuP(NDip)2]Li2·(tmeda)2 (5a), and the monolithium compounds [PhP(NHt-Bu)(NR)]Li·(tmeda) (R = t-Bu 2, Dip 4) and [t-BuP(NHDip)(NDip)]Li·(tmeda) (6). Treatment of 1, 3 and 5 with GeCl2·dioxane or SnCl2 in a 1 : 1 stoichiometric ratio gave the corresponding tetrylenes [PhP(Nt-Bu)2]E (E = Ge 7, Sn 10), [PhP(Nt-Bu)(NDip)]Ge (8) and [t-BuP(NDip)2]E (E = Ge 9, Sn 11). The heteroleptic germylene [Ph(H)P(Nt-Bu)2]GeCl (12) was obtained by the reaction of the monolithium compound [PhP(NHt-Bu)(Nt-Bu)]Li·(tmeda) (2) with GeCl2·dioxane in a 1 : 1 stoichiometric ratio, as a result of a spontaneous NH → PH tautomeric shift in the ligand backbone. In contrast, an analogous reaction with SnCl2 produced only stannylene 10 along with the PhP(NHt-Bu)2 starting material, suggesting scrambling of the ligands rather than a NH → PH tautomeric shift. Finally, heating 5a in solution led to P–C bond cleavage and formation of the bis(imino)phosphide [DipNPNDip]Li·(tmeda) (13). The reaction of 13 with GeCl2·dioxane, SnCl2 or PbCl2 in a 2 : 1 stoichiometric ratio yielded the unprecedented tetrylenes [DipNPNDip]2E (E = Ge 14, Sn 15 and Pb 16), in which the tetrylene center is incorporated within two N2PE rings. Treatment of the monolithium compound 2 with n-BuLi and K (or KC8) gave [t-BuNPNt-Bu]Li·(tmeda) (17) and{[t-BuNPNt-Bu]K(tmeda)}2 (18), respectively. In contrast to the reaction with 13, similar reactions of 17 with GeCl2·dioxane and SnCl2 resulted in the known compounds cis-[P(μ-Nt-Bu)2P(t-BuN)2]E (E = Ge, Sn); evidently the t-Bu groups do not provide sufficient steric shielding to protect the bis(imino)phosphide backbone as in the case of 14–16. The bonding situation in a set of selected compounds (8, 12–16) has been subjected to a theoretical survey with particular emphasis on the nature of the bonding between the ligand and the central metal and the bonding within the NPN core of the ligand, showing significant differences among the studied complexes. [ABSTRACT FROM AUTHOR]

Published
2016
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