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Hans Pritzkow - One of the best experts on this subject based on the ideXlab platform.
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c h bond activation of simple alkenes with c5h5 co fragments preparation molecular structure and dynamical behaviour of tri and tetranuclear cyclopentadienylcobalt cluster complexes with μ Cycloalkyne ligands
Chemische Berichte, 1997Co-Authors: Hubert Wadepohl, Till Borchert, Hans PritzkowAbstract:Vicinal C–H bonds of the cycloalkenes CnH2n (n = 5–8) were activated upon treatment under mild conditions with reactive sources of the (C5H5)CO fragment. With [C5H5)CO(C2H4)2] (2a), the trinuclear cluster complexes [H2((C5H5)CO)3(μ3-C2(CH2)n-2)] (5a: n = 5; 5c: n = 5d: n = 8) were formed. Using the more reactive [(C5H5)2Co]/K, 5a–5dwere obtained, along with small amounts of the tetranuclear [{(C5H5)CO}4r{μ4-C2(CH2)n-2}] (8a–c: n = 5–7). X-ray structure analyses of 5c, d and 8b, c were performed. A μ-‖ (orμ3-η1:η2:η1) coordination of the Cycloalkyne ligands was found in the trinuclear cluster complexes. The tetranuclear 8b, c had the Cycloalkynes quadruply bridging (μ4-η1:η2:η2:η1_ a butterfly arrangement of the metal atoms. The acetylenic carbon–carbon bonds are considerably lengthened upon coordination [1.392(4), 1.398(3) a in 5c d; 1.464(8), 1.499(5) A in 8b, c]. Three dynamic processes – alkyne “walk” on top of the CO3 triangle, μ2-hydride migration, and μ2/μ3-hydride exchange – are operational in the trinuclear 5a–d. Dynamic NMR data for 5a are consistent with a “windshield-wiper” mechanism for the alkyne migration. Hydride exchange is associated with a higher energy barrier, and is probably and independent dynamic process.
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C–H Bond Activation of Simple Alkenes with (C5H5)CO Fragments: Preparation, Molecular Structure, and Dynamical Behaviour of Tri- and Tetranuclear Cyclopentadienylcobalt Cluster complexes with μ-Cycloalkyne Ligands
Chemische Berichte, 1997Co-Authors: Hubert Wadepohl, Till Borchert, Hans PritzkowAbstract:Vicinal C–H bonds of the cycloalkenes CnH2n (n = 5–8) were activated upon treatment under mild conditions with reactive sources of the (C5H5)CO fragment. With [C5H5)CO(C2H4)2] (2a), the trinuclear cluster complexes [H2((C5H5)CO)3(μ3-C2(CH2)n-2)] (5a: n = 5; 5c: n = 5d: n = 8) were formed. Using the more reactive [(C5H5)2Co]/K, 5a–5dwere obtained, along with small amounts of the tetranuclear [{(C5H5)CO}4r{μ4-C2(CH2)n-2}] (8a–c: n = 5–7). X-ray structure analyses of 5c, d and 8b, c were performed. A μ-‖ (orμ3-η1:η2:η1) coordination of the Cycloalkyne ligands was found in the trinuclear cluster complexes. The tetranuclear 8b, c had the Cycloalkynes quadruply bridging (μ4-η1:η2:η2:η1_ a butterfly arrangement of the metal atoms. The acetylenic carbon–carbon bonds are considerably lengthened upon coordination [1.392(4), 1.398(3) a in 5c d; 1.464(8), 1.499(5) A in 8b, c]. Three dynamic processes – alkyne “walk” on top of the CO3 triangle, μ2-hydride migration, and μ2/μ3-hydride exchange – are operational in the trinuclear 5a–d. Dynamic NMR data for 5a are consistent with a “windshield-wiper” mechanism for the alkyne migration. Hydride exchange is associated with a higher energy barrier, and is probably and independent dynamic process.
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C–H bond activation of simple alkenes with cyclopentadienylcobalt fragments: preparation and structure of tri- and tetra-cobalt µ-Cycloalkyne cluster complexes
J. Chem. Soc. Chem. Commun., 1995Co-Authors: Hubert Wadepohl, Till Borchert, Hans PritzkowAbstract:Twofold C–H bond activation of cycloalkenes resulting in the formation of tri- and tetra-nuclear Cycloalkyne bridged cluster complexes takes place on reaction with reactive sources of (η5-C5C5)Co fragments.
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c h bond activation of simple alkenes with cyclopentadienylcobalt fragments preparation and structure of tri and tetra cobalt µ Cycloalkyne cluster complexes
Journal of The Chemical Society Chemical Communications, 1995Co-Authors: Hubert Wadepohl, Till Borchert, Hans PritzkowAbstract:Twofold C–H bond activation of cycloalkenes resulting in the formation of tri- and tetra-nuclear Cycloalkyne bridged cluster complexes takes place on reaction with reactive sources of (η5-C5C5)Co fragments.
Masahiko Yamaguchi - One of the best experts on this subject based on the ideXlab platform.
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Synthesis and ring size effect of macrocyclic ethynylhelicene oligomers.
The Journal of organic chemistry, 2006Co-Authors: Yusuke Takahira, Hiroki Sugiura, Masahiko YamaguchiAbstract:The cyclization of acyclic ethynylhelicene oligomers with decyl 3,5-diiodobenzoate under optimized conditions gave the corresponding optically active [n+n]Cycloalkynes (n = 4−8) in high yields. Their structures were compared in terms of ring size by using 1H NMR, UV−vis, and CD spectroscopies and vapor pressure osmometry (VPO). The UV−vis spectra exhibited an increase in absorbance in proportion to n. In contrast, the CD spectra of the macrocycles exhibited a large ring size effect, comparable Δe values despite the increase in n and temperature-dependent properties of the [8+8]Cycloalkyne. It was concluded that [4+4]Cycloalkyne, [5+5]Cycloalkyne, [6+6]Cycloalkyne, and [7+7]Cycloalkyne have rigid structures, while [8+8]Cycloalkyne has a flexible structure.
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Functionalized [3 + 3]Cycloalkynes: Substituent Effect on Self-Aggregation by Nonplanar π−π Interactions
The Journal of organic chemistry, 2005Co-Authors: Hiroki Sugiura, Yusuke Takahira, Masahiko YamaguchiAbstract:[reaction: see text] Optically active (M)-2,11-dihydroxy-1,12-dimethylbenzo[c]phenanthrene-5,8-dicarbonitrile was synthesized from (M)-1,12-dimethyl-2,11-dinitrobenzo[c]phenanthrene-5,8-dicarbonitrile by the reduction and hydroxylation of nitro groups. The compound was converted to several oxygen-functionalized [3 + 3]Cycloalkynes with -OH, -OSiMe2-t-Bu, -OAc, -OTf, or -ONf groups, which are chiral arylene ethynylene macrocycles containing three helicenes. The aggregation behaviors of these [3 + 3]Cycloalkynes were examined in CHCl3, THF, and acetone using 1H NMR, CD, and vapor pressure osmometry (VPO) studies and were compared with that of the parent [3 + 3]Cycloalkyne. An increasing strength of aggregation in CHCl3 was observed in the following order of the substituted derivatives: -H > -ONf > -OTf > -OAc > -OSiMe2-t-Bu. In THF the following strength of aggregation was observed: -OTf > -ONf > -OAc > -H > -OSiMe(2)-t-Bu > -OH. The aggregation of the functionalized [3 + 3]Cycloalkynes is stronger for the compounds with electron-withdrawing substituents than for those with electron-donating substituents. (M)-1,12-dimethylbenzo[c]phenanthrene-2,5,8,11-tetraol was also synthesized from the same intermediate. This electron-rich helicene was readily oxidized to 5,6-quinone in air, and the quinone was suggested to form a self-charge-transfer complex in solid state.
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[3+3]Cycloalkyne Dimers Linked by an Azo Group: A Stable cis-Azo Compound Forms Polymeric Aggregates by Nonplanar π−π Interactions
Journal of the American Chemical Society, 2003Co-Authors: Yuto Saiki, Tomonori Hoshi, Hiroki Sugiura, Keiichi Nakamura, Masahiko Yamaguchi, Jun-ichi AnzaiAbstract:We previously reported that the structure of the linker moiety controlled intramolecular and bimolecular aggregation of [3+3]Cycloalkyne oligomers, which are cyclic acetylene derivatives containing helicenes. Here, novel [3+3]Cycloalkyne dimers linked by the azo group are synthesized, and aggregation behaviors are studied, which turned out to be considerably different. The trans- and cis-azo compounds were synthesized by the oxidative coupling of a [3+3]Cycloalkyne amine derivative, and the stereochemistry was determined by UV−vis spectroscopy. 1H NMR, CD, gel permeation chromatography analysis, and vapor pressure osmometry in chloroform revealed that the trans-isomer forms a strong and selective bimolecular aggregate. The cis-isomer forms a trimolecular aggregate at a concentration below 1 mM and a polymeric aggregate at above 1 mM. Unlike known diaryl azo compounds, these azo isomers do not interconvert when subjected to heating or irradiation. In contrast, a model compound lacking the cyclic helicene s...
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[3+3]Cycloalkyne dimers linked by an azo group: a stable cis-azo compound forms polymeric aggregates by nonplanar pi-pi interactions.
Journal of the American Chemical Society, 2003Co-Authors: Yuto Saiki, Tomonori Hoshi, Hiroki Sugiura, Keiichi Nakamura, Masahiko Yamaguchi, Jun-ichi AnzaiAbstract:We previously reported that the structure of the linker moiety controlled intramolecular and bimolecular aggregation of [3+3]Cycloalkyne oligomers, which are cyclic acetylene derivatives containing helicenes. Here, novel [3+3]Cycloalkyne dimers linked by the azo group are synthesized, and aggregation behaviors are studied, which turned out to be considerably different. The trans- and cis-azo compounds were synthesized by the oxidative coupling of a [3+3]Cycloalkyne amine derivative, and the stereochemistry was determined by UV-vis spectroscopy. 1H NMR, CD, gel permeation chromatography analysis, and vapor pressure osmometry in chloroform revealed that the trans-isomer forms a strong and selective bimolecular aggregate. The cis-isomer forms a trimolecular aggregate at a concentration below 1 mM and a polymeric aggregate at above 1 mM. Unlike known diaryl azo compounds, these azo isomers do not interconvert when subjected to heating or irradiation. In contrast, a model compound lacking the cyclic helicene structure isomerizes readily.
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3 3 Cycloalkyne dimers linked by an azo group a stable cis azo compound forms polymeric aggregates by nonplanar π π interactions
Journal of the American Chemical Society, 2003Co-Authors: Yuto Saiki, Tomonori Hoshi, Hiroki Sugiura, Keiichi Nakamura, Masahiko Yamaguchi, Jun-ichi AnzaiAbstract:We previously reported that the structure of the linker moiety controlled intramolecular and bimolecular aggregation of [3+3]Cycloalkyne oligomers, which are cyclic acetylene derivatives containing helicenes. Here, novel [3+3]Cycloalkyne dimers linked by the azo group are synthesized, and aggregation behaviors are studied, which turned out to be considerably different. The trans- and cis-azo compounds were synthesized by the oxidative coupling of a [3+3]Cycloalkyne amine derivative, and the stereochemistry was determined by UV−vis spectroscopy. 1H NMR, CD, gel permeation chromatography analysis, and vapor pressure osmometry in chloroform revealed that the trans-isomer forms a strong and selective bimolecular aggregate. The cis-isomer forms a trimolecular aggregate at a concentration below 1 mM and a polymeric aggregate at above 1 mM. Unlike known diaryl azo compounds, these azo isomers do not interconvert when subjected to heating or irradiation. In contrast, a model compound lacking the cyclic helicene s...
Jun-ichi Anzai - One of the best experts on this subject based on the ideXlab platform.
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[3+3]Cycloalkyne dimers linked by an azo group: a stable cis-azo compound forms polymeric aggregates by nonplanar pi-pi interactions.
Journal of the American Chemical Society, 2003Co-Authors: Yuto Saiki, Tomonori Hoshi, Hiroki Sugiura, Keiichi Nakamura, Masahiko Yamaguchi, Jun-ichi AnzaiAbstract:We previously reported that the structure of the linker moiety controlled intramolecular and bimolecular aggregation of [3+3]Cycloalkyne oligomers, which are cyclic acetylene derivatives containing helicenes. Here, novel [3+3]Cycloalkyne dimers linked by the azo group are synthesized, and aggregation behaviors are studied, which turned out to be considerably different. The trans- and cis-azo compounds were synthesized by the oxidative coupling of a [3+3]Cycloalkyne amine derivative, and the stereochemistry was determined by UV-vis spectroscopy. 1H NMR, CD, gel permeation chromatography analysis, and vapor pressure osmometry in chloroform revealed that the trans-isomer forms a strong and selective bimolecular aggregate. The cis-isomer forms a trimolecular aggregate at a concentration below 1 mM and a polymeric aggregate at above 1 mM. Unlike known diaryl azo compounds, these azo isomers do not interconvert when subjected to heating or irradiation. In contrast, a model compound lacking the cyclic helicene structure isomerizes readily.
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[3+3]Cycloalkyne Dimers Linked by an Azo Group: A Stable cis-Azo Compound Forms Polymeric Aggregates by Nonplanar π−π Interactions
Journal of the American Chemical Society, 2003Co-Authors: Yuto Saiki, Tomonori Hoshi, Hiroki Sugiura, Keiichi Nakamura, Masahiko Yamaguchi, Jun-ichi AnzaiAbstract:We previously reported that the structure of the linker moiety controlled intramolecular and bimolecular aggregation of [3+3]Cycloalkyne oligomers, which are cyclic acetylene derivatives containing helicenes. Here, novel [3+3]Cycloalkyne dimers linked by the azo group are synthesized, and aggregation behaviors are studied, which turned out to be considerably different. The trans- and cis-azo compounds were synthesized by the oxidative coupling of a [3+3]Cycloalkyne amine derivative, and the stereochemistry was determined by UV−vis spectroscopy. 1H NMR, CD, gel permeation chromatography analysis, and vapor pressure osmometry in chloroform revealed that the trans-isomer forms a strong and selective bimolecular aggregate. The cis-isomer forms a trimolecular aggregate at a concentration below 1 mM and a polymeric aggregate at above 1 mM. Unlike known diaryl azo compounds, these azo isomers do not interconvert when subjected to heating or irradiation. In contrast, a model compound lacking the cyclic helicene s...
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3 3 Cycloalkyne dimers linked by an azo group a stable cis azo compound forms polymeric aggregates by nonplanar π π interactions
Journal of the American Chemical Society, 2003Co-Authors: Yuto Saiki, Tomonori Hoshi, Hiroki Sugiura, Keiichi Nakamura, Masahiko Yamaguchi, Jun-ichi AnzaiAbstract:We previously reported that the structure of the linker moiety controlled intramolecular and bimolecular aggregation of [3+3]Cycloalkyne oligomers, which are cyclic acetylene derivatives containing helicenes. Here, novel [3+3]Cycloalkyne dimers linked by the azo group are synthesized, and aggregation behaviors are studied, which turned out to be considerably different. The trans- and cis-azo compounds were synthesized by the oxidative coupling of a [3+3]Cycloalkyne amine derivative, and the stereochemistry was determined by UV−vis spectroscopy. 1H NMR, CD, gel permeation chromatography analysis, and vapor pressure osmometry in chloroform revealed that the trans-isomer forms a strong and selective bimolecular aggregate. The cis-isomer forms a trimolecular aggregate at a concentration below 1 mM and a polymeric aggregate at above 1 mM. Unlike known diaryl azo compounds, these azo isomers do not interconvert when subjected to heating or irradiation. In contrast, a model compound lacking the cyclic helicene s...
Hiroki Sugiura - One of the best experts on this subject based on the ideXlab platform.
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Synthesis and ring size effect of macrocyclic ethynylhelicene oligomers.
The Journal of organic chemistry, 2006Co-Authors: Yusuke Takahira, Hiroki Sugiura, Masahiko YamaguchiAbstract:The cyclization of acyclic ethynylhelicene oligomers with decyl 3,5-diiodobenzoate under optimized conditions gave the corresponding optically active [n+n]Cycloalkynes (n = 4−8) in high yields. Their structures were compared in terms of ring size by using 1H NMR, UV−vis, and CD spectroscopies and vapor pressure osmometry (VPO). The UV−vis spectra exhibited an increase in absorbance in proportion to n. In contrast, the CD spectra of the macrocycles exhibited a large ring size effect, comparable Δe values despite the increase in n and temperature-dependent properties of the [8+8]Cycloalkyne. It was concluded that [4+4]Cycloalkyne, [5+5]Cycloalkyne, [6+6]Cycloalkyne, and [7+7]Cycloalkyne have rigid structures, while [8+8]Cycloalkyne has a flexible structure.
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Functionalized [3 + 3]Cycloalkynes: Substituent Effect on Self-Aggregation by Nonplanar π−π Interactions
The Journal of organic chemistry, 2005Co-Authors: Hiroki Sugiura, Yusuke Takahira, Masahiko YamaguchiAbstract:[reaction: see text] Optically active (M)-2,11-dihydroxy-1,12-dimethylbenzo[c]phenanthrene-5,8-dicarbonitrile was synthesized from (M)-1,12-dimethyl-2,11-dinitrobenzo[c]phenanthrene-5,8-dicarbonitrile by the reduction and hydroxylation of nitro groups. The compound was converted to several oxygen-functionalized [3 + 3]Cycloalkynes with -OH, -OSiMe2-t-Bu, -OAc, -OTf, or -ONf groups, which are chiral arylene ethynylene macrocycles containing three helicenes. The aggregation behaviors of these [3 + 3]Cycloalkynes were examined in CHCl3, THF, and acetone using 1H NMR, CD, and vapor pressure osmometry (VPO) studies and were compared with that of the parent [3 + 3]Cycloalkyne. An increasing strength of aggregation in CHCl3 was observed in the following order of the substituted derivatives: -H > -ONf > -OTf > -OAc > -OSiMe2-t-Bu. In THF the following strength of aggregation was observed: -OTf > -ONf > -OAc > -H > -OSiMe(2)-t-Bu > -OH. The aggregation of the functionalized [3 + 3]Cycloalkynes is stronger for the compounds with electron-withdrawing substituents than for those with electron-donating substituents. (M)-1,12-dimethylbenzo[c]phenanthrene-2,5,8,11-tetraol was also synthesized from the same intermediate. This electron-rich helicene was readily oxidized to 5,6-quinone in air, and the quinone was suggested to form a self-charge-transfer complex in solid state.
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[3+3]Cycloalkyne Dimers Linked by an Azo Group: A Stable cis-Azo Compound Forms Polymeric Aggregates by Nonplanar π−π Interactions
Journal of the American Chemical Society, 2003Co-Authors: Yuto Saiki, Tomonori Hoshi, Hiroki Sugiura, Keiichi Nakamura, Masahiko Yamaguchi, Jun-ichi AnzaiAbstract:We previously reported that the structure of the linker moiety controlled intramolecular and bimolecular aggregation of [3+3]Cycloalkyne oligomers, which are cyclic acetylene derivatives containing helicenes. Here, novel [3+3]Cycloalkyne dimers linked by the azo group are synthesized, and aggregation behaviors are studied, which turned out to be considerably different. The trans- and cis-azo compounds were synthesized by the oxidative coupling of a [3+3]Cycloalkyne amine derivative, and the stereochemistry was determined by UV−vis spectroscopy. 1H NMR, CD, gel permeation chromatography analysis, and vapor pressure osmometry in chloroform revealed that the trans-isomer forms a strong and selective bimolecular aggregate. The cis-isomer forms a trimolecular aggregate at a concentration below 1 mM and a polymeric aggregate at above 1 mM. Unlike known diaryl azo compounds, these azo isomers do not interconvert when subjected to heating or irradiation. In contrast, a model compound lacking the cyclic helicene s...
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[3+3]Cycloalkyne dimers linked by an azo group: a stable cis-azo compound forms polymeric aggregates by nonplanar pi-pi interactions.
Journal of the American Chemical Society, 2003Co-Authors: Yuto Saiki, Tomonori Hoshi, Hiroki Sugiura, Keiichi Nakamura, Masahiko Yamaguchi, Jun-ichi AnzaiAbstract:We previously reported that the structure of the linker moiety controlled intramolecular and bimolecular aggregation of [3+3]Cycloalkyne oligomers, which are cyclic acetylene derivatives containing helicenes. Here, novel [3+3]Cycloalkyne dimers linked by the azo group are synthesized, and aggregation behaviors are studied, which turned out to be considerably different. The trans- and cis-azo compounds were synthesized by the oxidative coupling of a [3+3]Cycloalkyne amine derivative, and the stereochemistry was determined by UV-vis spectroscopy. 1H NMR, CD, gel permeation chromatography analysis, and vapor pressure osmometry in chloroform revealed that the trans-isomer forms a strong and selective bimolecular aggregate. The cis-isomer forms a trimolecular aggregate at a concentration below 1 mM and a polymeric aggregate at above 1 mM. Unlike known diaryl azo compounds, these azo isomers do not interconvert when subjected to heating or irradiation. In contrast, a model compound lacking the cyclic helicene structure isomerizes readily.
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3 3 Cycloalkyne dimers linked by an azo group a stable cis azo compound forms polymeric aggregates by nonplanar π π interactions
Journal of the American Chemical Society, 2003Co-Authors: Yuto Saiki, Tomonori Hoshi, Hiroki Sugiura, Keiichi Nakamura, Masahiko Yamaguchi, Jun-ichi AnzaiAbstract:We previously reported that the structure of the linker moiety controlled intramolecular and bimolecular aggregation of [3+3]Cycloalkyne oligomers, which are cyclic acetylene derivatives containing helicenes. Here, novel [3+3]Cycloalkyne dimers linked by the azo group are synthesized, and aggregation behaviors are studied, which turned out to be considerably different. The trans- and cis-azo compounds were synthesized by the oxidative coupling of a [3+3]Cycloalkyne amine derivative, and the stereochemistry was determined by UV−vis spectroscopy. 1H NMR, CD, gel permeation chromatography analysis, and vapor pressure osmometry in chloroform revealed that the trans-isomer forms a strong and selective bimolecular aggregate. The cis-isomer forms a trimolecular aggregate at a concentration below 1 mM and a polymeric aggregate at above 1 mM. Unlike known diaryl azo compounds, these azo isomers do not interconvert when subjected to heating or irradiation. In contrast, a model compound lacking the cyclic helicene s...
Hubert Wadepohl - One of the best experts on this subject based on the ideXlab platform.
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c h bond activation of simple alkenes with c5h5 co fragments preparation molecular structure and dynamical behaviour of tri and tetranuclear cyclopentadienylcobalt cluster complexes with μ Cycloalkyne ligands
Chemische Berichte, 1997Co-Authors: Hubert Wadepohl, Till Borchert, Hans PritzkowAbstract:Vicinal C–H bonds of the cycloalkenes CnH2n (n = 5–8) were activated upon treatment under mild conditions with reactive sources of the (C5H5)CO fragment. With [C5H5)CO(C2H4)2] (2a), the trinuclear cluster complexes [H2((C5H5)CO)3(μ3-C2(CH2)n-2)] (5a: n = 5; 5c: n = 5d: n = 8) were formed. Using the more reactive [(C5H5)2Co]/K, 5a–5dwere obtained, along with small amounts of the tetranuclear [{(C5H5)CO}4r{μ4-C2(CH2)n-2}] (8a–c: n = 5–7). X-ray structure analyses of 5c, d and 8b, c were performed. A μ-‖ (orμ3-η1:η2:η1) coordination of the Cycloalkyne ligands was found in the trinuclear cluster complexes. The tetranuclear 8b, c had the Cycloalkynes quadruply bridging (μ4-η1:η2:η2:η1_ a butterfly arrangement of the metal atoms. The acetylenic carbon–carbon bonds are considerably lengthened upon coordination [1.392(4), 1.398(3) a in 5c d; 1.464(8), 1.499(5) A in 8b, c]. Three dynamic processes – alkyne “walk” on top of the CO3 triangle, μ2-hydride migration, and μ2/μ3-hydride exchange – are operational in the trinuclear 5a–d. Dynamic NMR data for 5a are consistent with a “windshield-wiper” mechanism for the alkyne migration. Hydride exchange is associated with a higher energy barrier, and is probably and independent dynamic process.
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C–H Bond Activation of Simple Alkenes with (C5H5)CO Fragments: Preparation, Molecular Structure, and Dynamical Behaviour of Tri- and Tetranuclear Cyclopentadienylcobalt Cluster complexes with μ-Cycloalkyne Ligands
Chemische Berichte, 1997Co-Authors: Hubert Wadepohl, Till Borchert, Hans PritzkowAbstract:Vicinal C–H bonds of the cycloalkenes CnH2n (n = 5–8) were activated upon treatment under mild conditions with reactive sources of the (C5H5)CO fragment. With [C5H5)CO(C2H4)2] (2a), the trinuclear cluster complexes [H2((C5H5)CO)3(μ3-C2(CH2)n-2)] (5a: n = 5; 5c: n = 5d: n = 8) were formed. Using the more reactive [(C5H5)2Co]/K, 5a–5dwere obtained, along with small amounts of the tetranuclear [{(C5H5)CO}4r{μ4-C2(CH2)n-2}] (8a–c: n = 5–7). X-ray structure analyses of 5c, d and 8b, c were performed. A μ-‖ (orμ3-η1:η2:η1) coordination of the Cycloalkyne ligands was found in the trinuclear cluster complexes. The tetranuclear 8b, c had the Cycloalkynes quadruply bridging (μ4-η1:η2:η2:η1_ a butterfly arrangement of the metal atoms. The acetylenic carbon–carbon bonds are considerably lengthened upon coordination [1.392(4), 1.398(3) a in 5c d; 1.464(8), 1.499(5) A in 8b, c]. Three dynamic processes – alkyne “walk” on top of the CO3 triangle, μ2-hydride migration, and μ2/μ3-hydride exchange – are operational in the trinuclear 5a–d. Dynamic NMR data for 5a are consistent with a “windshield-wiper” mechanism for the alkyne migration. Hydride exchange is associated with a higher energy barrier, and is probably and independent dynamic process.
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C–H bond activation of simple alkenes with cyclopentadienylcobalt fragments: preparation and structure of tri- and tetra-cobalt µ-Cycloalkyne cluster complexes
J. Chem. Soc. Chem. Commun., 1995Co-Authors: Hubert Wadepohl, Till Borchert, Hans PritzkowAbstract:Twofold C–H bond activation of cycloalkenes resulting in the formation of tri- and tetra-nuclear Cycloalkyne bridged cluster complexes takes place on reaction with reactive sources of (η5-C5C5)Co fragments.
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c h bond activation of simple alkenes with cyclopentadienylcobalt fragments preparation and structure of tri and tetra cobalt µ Cycloalkyne cluster complexes
Journal of The Chemical Society Chemical Communications, 1995Co-Authors: Hubert Wadepohl, Till Borchert, Hans PritzkowAbstract:Twofold C–H bond activation of cycloalkenes resulting in the formation of tri- and tetra-nuclear Cycloalkyne bridged cluster complexes takes place on reaction with reactive sources of (η5-C5C5)Co fragments.
