Insertion Reactions of Neutral Phosphidozirconocene Complexes as a Convenient Entry into Frustrated Lewis Pair Territory
International audience; Neutral phosphidozirconocene complexes [Cp2Zr(PR2)Me] (Cp=cyclopentadienyl; 1a: R=cyclohexyl (Cy); 1b: R=mesityl (Mes); 1c: R=tBu) undergo insertion into the Zr-P bond by non-enolisable carbonyl building blocks (O=CRR), such as benzophenone, aldehydes, paraformaldehyde or CO2, to give [Cp2Zr(OCRRPR2)Me] (3-7). Depending on the steric bulk around P, complexes 3-7 react with B(C6F5)(3) to give O-bridged cationic zirconocene dimers that display typical frustrated Lewis pair (FLP)/ambiphilic ligand behaviour. Thus, the reaction of {[Cp2Zr(-OCHPhPCy2)][MeB(C6F5)(3)]}(2) (10a) with chalcone results in 1,4 addition of the Zr+/P FLP, whereas the reaction of {[Cp2Zr(-OCHFcPCy…
Phosphido- and Amidozirconocene Cation-Based Frustrated Lewis Pair Chemistry
Methyl abstraction from neutral [Cp2ZrMe(ERR')] complexes 1 (E = N, P; R, R' = alkyl, aryl) with either B(C6F5)3 or [Ph3C][B(C6F5)4] results in the formation of [Cp2Zr(ERR')][X] complexes 2 (X(-) = MeB(C6F5)3(-), B(C6F5)4(-)). The X-ray structure of amido complexes [Cp2Zr(NPh2)][MeB(C6F5)3] (2d) and [Cp2Zr(N(t)BuAr)][B(C6F5)4] (2e', Ar = 3,5-C6H3(CH3)2) is reported, showing a sterically dependent Zr/N-π interaction. Complexes 2 catalyze the hydrogenation of electron-rich olefins and alkynes under mild conditions (room temperature, 1.5 bar H2). Complex 2e binds CO2, giving [Cp2Zr(CO2)(N(t)BuAr)]2[MeB(C6F5)3]2 (3e). Amido complex 2d reacts with benzaldehyde yielding [Cp2Zr(OCH2Ph)((OC)PhNPh2)…
Mesogens with Aggregation-Induced Emission Formed by Hydrogen Bonding
In this contribution, we report a supramolecular approach toward mesogens showing aggregation-induced emission (AIE). AIE-active aromatic thioethers, acting as hydrogen-bond donors, were combined with alkoxystilbazoles as hydrogen-bond acceptors. Upon self-assembly, hydrogen-bonded complexes with monotropic liquid crystalline behavior were obtained. In addition, it was found that the introduction of a chiral citronellyl side chain leads to drastic bathochromic shift of the emission, which was not observed for linear alkyl chains. The mesomorphic behavior, as well as the photophysical properties as a solid and in the mesophase of the liquid crystalline assemblies, were studied in detail.
Improving the mesomorphic behaviour of supramolecular liquid crystals by resonance-assisted hydrogen bonding
A systematic structure-property relationship study on hydrogen-bonded liquid crystals was performed, revealing the impact of resonance-assisted hydrogen bonds (RAHBs) on the self-assembling behavior of the supramolecular architecture. The creation of a six-membered intramolecular hydrogen-bonded ring acts as a counterpart to the self-organization between hydrogen bond donators and acceptors and determines thus the suprastructure. Variation of the hydrogen-bonding pattern allowed us to significantly improve the temperature range of the reported liquid crystalline assemblies.
Naturally occurring polyphenols as building blocks for supramolecular liquid crystals – substitution pattern dominates mesomorphism
A modular supramolecular approach towards hydrogen-bonded liquid crystalline assemblies based on naturally occurring polyphenols is reported. The combination of experimental observations, crystallographic studies and semi-empirical analyses of the assemblies provides insight into the structure–property relationships of these materials. Here a direct correlation of the number of donor OH-groups as well as their orientation with the mesomorphic behavior is reported. We discovered that the number and orientation of the OH-groups have a stronger influence on the mesomorphic behavior of the supramolecular assemblies than the connectivity (e.g. stilbenoid or chalconoid) of the hydrogen bond donor…
ChemInform Abstract: Phosphido- and Amidozirconocene Cation-Based Frustrated Lewis Pair Chemistry.
Methyl abstraction from neutral [Cp2ZrMe(ERR′)] complexes 1 (E = N, P; R, R′ = alkyl, aryl) with either B(C6F5)3 or [Ph3C][B(C6F5)4] results in the formation of [Cp2Zr(ERR′)][X] complexes 2 (X– = MeB(C6F5)3–, B(C6F5)4–). The X-ray structure of amido complexes [Cp2Zr(NPh2)][MeB(C6F5)3] (2d) and [Cp2Zr(NtBuAr)][B(C6F5)4] (2e′, Ar = 3,5-C6H3(CH3)2) is reported, showing a sterically dependent Zr/N−π interaction. Complexes 2 catalyze the hydrogenation of electron-rich olefins and alkynes under mild conditions (room temperature, 1.5 bar H2). Complex 2e binds CO2, giving [Cp2Zr(CO2)(NtBuAr)]2[MeB(C6F5)3]2 (3e). Amido complex 2d reacts with benzaldehyde yielding [Cp2Zr(OCH2Ph)((OC)PhNPh2)][MeB(C6F5…
Direct P-functionalization of azobenzene by a cationic phosphidozirconocene complex.
International audience; We report that the cationic phosphidozirconocene complex [(eta(5)-C5H5)(2)Zr(PCy2)][CH3B(C6F5)(3)] (II) reacts with azobenzene, resulting in the expedient formation of Zr complex (2) bound to a tridentate PNN ligand. This reaction proceeds by a mechanism of cooperative nucleophilic substitution of hydrogen. The intermediate sigma(H) adduct (1) has been characterized by NMR spectroscopy.
Synthetic Endeavors toward Titanium Based Frustrated Lewis Pairs with Controlled Electronic and Steric Properties
A new family of cationic Ti complexes 4′ with a pendant phosphine of general formula [CpCpPTiOAr][BPh4] (Cp = η5-C5H5; CpP = η5-C5H4(CMe2)PR2) has been prepared in four steps from 6,6-dimethylfulvene. These complexes were designed to behave as Ti based frustrated Lewis pairs (FLPs). The key synthetic step is a reduction–oxidation sequence from [CpCpPTiClOAr] complexes 3 using lithium phosphide salts as the reductants and ferricinium tetraphenylborate as the oxidant. Four complexes have been structurally characterized by X-ray diffraction and show elongated Ti–P bonds, above 2.60 A. One complex (4b′: OAr = 2,6-Me2C6H3; PR2 = PCy2) reacted with benzaldehyde to form a typical FLP activation pr…
Structure-property relationships in aromatic thioethers featuring aggregation-induced emission : Solid-state structures and theoretical analysis
We describe in this paper a structure–property relationship study of aromatic thioethers with aggregation-induced emission (AIE) properties. We combine a structural analysis based on geometrical consideration with an in-depth analysis of the crystalline packing supported by quantum mechanical calculations. Our results allow us to correlate the enhanced fluorescence quantum yields with the significant increase of C–H⋯π and the decrease of π⋯π interactions in the solid state – a result which supports the well-accepted AIE mechanism quantitatively.
Desymmetrization of Prochiral Cyclobutanones via Nitrogen Insertion: A Concise Route to Chiral γ‐Lactams
Abstract Asymmetric access to γ‐lactams is achieved via a cyclobutanone ring expansion using widely available (1S,2R)‐1‐amino‐2‐indanol for chiral induction. Mechanistic analysis of the key N,O‐ketal rearrangement reveals a Curtin–Hammett scenario, which enables a downstream stereoinduction (up to 88:12 dr) and is corroborated by spectroscopic, crystallographic, and computational studies. In combination with an easy deprotection protocol, this operationally simple sequence allows the synthesis of a range of optically pure γ‐lactams, including those bearing all‐carbon quaternary stereocenters. In addition, the formal synthesis of drug molecules baclofen, brivaracetam, and pregabalin further …
Desymmetrisierung von prochiralen Cyclobutanonen via Stickstoffinsertion: Ein einfacher Zugang zu chiralen γ‐Lactamen
CCDC 1421130: Experimental Crystal Structure Determination
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CCDC 1424182: Experimental Crystal Structure Determination
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CCDC 1894901: Experimental Crystal Structure Determination
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CCDC 1053357: Experimental Crystal Structure Determination
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CCDC 1424183: Experimental Crystal Structure Determination
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CCDC 1893331: Experimental Crystal Structure Determination
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CCDC 1424177: Experimental Crystal Structure Determination
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CCDC 1895359: Experimental Crystal Structure Determination
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CCDC 1052598: Experimental Crystal Structure Determination
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CCDC 1421134: Experimental Crystal Structure Determination
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CCDC 1052596: Experimental Crystal Structure Determination
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CCDC 1895424: Experimental Crystal Structure Determination
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CCDC 1421135: Experimental Crystal Structure Determination
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CCDC 1052597: Experimental Crystal Structure Determination
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CCDC 1052593: Experimental Crystal Structure Determination
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CCDC 1942435: Experimental Crystal Structure Determination
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CCDC 1421138: Experimental Crystal Structure Determination
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CCDC 1053358: Experimental Crystal Structure Determination
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CCDC 2051971: Experimental Crystal Structure Determination
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CCDC 1421133: Experimental Crystal Structure Determination
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CCDC 1945777: Experimental Crystal Structure Determination
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CCDC 1424181: Experimental Crystal Structure Determination
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CCDC 1052592: Experimental Crystal Structure Determination
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CCDC 1421131: Experimental Crystal Structure Determination
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CCDC 1052595: Experimental Crystal Structure Determination
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CCDC 1938656: Experimental Crystal Structure Determination
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CCDC 1052594: Experimental Crystal Structure Determination
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CCDC 2051973: Experimental Crystal Structure Determination
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CCDC 1421128: Experimental Crystal Structure Determination
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CCDC 1421129: Experimental Crystal Structure Determination
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CCDC 1421132: Experimental Crystal Structure Determination
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CCDC 1424178: Experimental Crystal Structure Determination
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CCDC 1440373: Experimental Crystal Structure Determination
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CCDC 2051972: Experimental Crystal Structure Determination
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CCDC 1424179: Experimental Crystal Structure Determination
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CCDC 1895360: Experimental Crystal Structure Determination
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CCDC 1440372: Experimental Crystal Structure Determination
Related Article: Adrien T. Normand, Constantin G. Daniliuc, Gerald Kehr, Pierre Le Gendre, Gerhard Erker|2016|Dalton Trans.|45|3711|doi:10.1039/C6DT00416D
CCDC 2051970: Experimental Crystal Structure Determination
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CCDC 1421136: Experimental Crystal Structure Determination
Related Article: Adrien T. Normand, Constantin G. Daniliuc, Birgit Wibbeling, Gerald Kehr, Pierre Le Gendre, and Gerhard Erker|2015|J.Am.Chem.Soc.|137|10796|doi:10.1021/jacs.5b06551
CCDC 1424180: Experimental Crystal Structure Determination
Related Article: Adrien T. Normand, Constantin G. Daniliuc, Birgit Wibbeling, Gerald Kehr, Pierre Le Gendre, Gerhard Erker|2016|Chem.-Eur.J.|22|4285|doi:10.1002/chem.201504792
CCDC 1424184: Experimental Crystal Structure Determination
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CCDC 1421137: Experimental Crystal Structure Determination
Related Article: Adrien T. Normand, Constantin G. Daniliuc, Birgit Wibbeling, Gerald Kehr, Pierre Le Gendre, and Gerhard Erker|2015|J.Am.Chem.Soc.|137|10796|doi:10.1021/jacs.5b06551