45851
2016
2016
eng
140
147
8
642
article
Wiley-VCH
Weinheim
1
--
--
--
Investigation of the Catalytic Activity of a 2-Phenylidenepyridine Palladium(II) Complex Bearing 4,5-Dicyano-1,3-bis(mesityl)imidazol-2-ylidene in the Mizoroki-Heck Reaction
The phenylidenepyridine (ppy) palladacycles [PdCl(ppy)(IMes)] (4) [IMes = 1,3-bis(mesityl) imidazol-2-ylidene] and [PdCl(ppy){(CN)(2)IMes}] (6) [(CN)(2)IMes = 4,5-dicyano-1,3-bis(mesityl) imidazol-2-ylidene] were prepared by facile two step syntheses, starting with the reaction of palladium(II) chloride with 2-phenylpyridine followed by subsequent addition of the NHC ligand to the precatalyst precursor [PdCl(ppy)](2). Suitable crystals for the X-ray analysis of the complexes 4 and 6 were obtained. It was shown that 6 has a shorter NHC-palladium bond than the IMes complex 4. The difference of the palladium carbene bond lengths based on the higher pi-acceptor strength of (CN)(2)IMes in comparison to IMes. Thus, (CN)(2)IMes should stabilize the catalytically active central palladium atom better than IMes. As a measure for the pi-acceptor strength of (CN)(2)IMes compared to IMes, the selone (CN)(2)IMes center dot Se (7) was prepared and characterized by Se-77-NMR spectroscopy. The pi-acceptor strength of 7 was illuminated by the shift of its Se-77-NMR signal. The Se-77-NMR signal of 7 was shifted to much higher frequencies than the Se-77-NMR signal of IMes center dot Se. Catalytic experiments using the Mizoroki-Heck reaction of aryl chlorides with n-butyl acrylate showed that 6 is the superior performer in comparison to 4. Using complex 6, an extensive substrate screening of 26 different aryl bromides with n-butyl acrylate was performed. Complex 6 is a suitable precatalyst for para-substituted aryl bromides. The catalytically active species was identified by mercury poisoning experiments to be palladium nanoparticles.
Zeitschrift für anorganische und allgemeine Chemie
10.1002/zaac.201500625
0044-2313
1521-3749
wos2016:2019
WOS:000369868500007
Holdt, HJ (reprint author), Univ Potsdam, Chair Inorgan Chem, Karl Liebknecht Str 24-25, D-14476 Golm, Germany., holdt@uni-potsdam.de
importub
2020-03-22T21:59:01+00:00
filename=package.tar
9fd1435167ce84310e1f45ce75d4e932
Heiko Baier
Alexandra Kelling
Uwe Schilde
Hans-Jürgen Holdt
eng
uncontrolled
Carbene ligands
eng
uncontrolled
Heck reaction
eng
uncontrolled
Palladium
eng
uncontrolled
Selenium
eng
uncontrolled
C-C coupling
Institut für Chemie
Referiert
Import
39036
2015
2015
eng
1950
1957
8
11
article
Wiley-VCH
Weinheim
1
--
--
--
PEPPSI-Effect on Suzuki-Miyaura Reactions Using 4,5-Dicyano-1,3-dimesitylimidazol-2-ylidene-Palladium Complexes: A Comparison between trans-Ligands
The PEPPSI (Pyridine Enhanced Precatalyst Preparation, Stabilization and Initiation) complexes 12-15 with the structure [PdCl2{(CN)(2)IMes}(3-R-py)] (12: R = H; 13: R = Cl; 14: R = Br; 15: R = CN) bearing the maleonitrile-based N-heterocyclic carbene (NHC) (CN)(2)IMes ({(CN)(2)IMes}: 4,5-dicyano-1,3-dimesitylimidazol-2-ylidene) were prepared. Solid state structures of 14 and 15 were obtained. Complexes 14 and 15 adopt a slightly distorted square-planar coordination geometry in the solid state with the substituted pyridine ligand trans to the NHC. Catalytic activities of precatalysts 12-15 were studied and subsequently compared to complexes [PdCl2{(CN)(2)IMes}(PPh3)] (4) and [PdCl(dmba){(CN)(2)IMes}] (5) recently reported by our group in the Suzuki-Miyaura reaction of various aryl halides and phenylboronic acid. Reactions using previously reported [PdCl2(IMes)(py)] (IMes: 1,3-dimesitylimidazol-2-ylidene) (1) were also carried out and their results contrasted to those involving 12-15, 4 and 5. Differences in initiation rates and the catalytically active species related to the seven complexes in regards to the throw away ligand were investigated. Poisoning experiments with mercury show that palladium nanoparticles are responsible for the catalytic activity.
European journal of inorganic chemistry : a journal of ChemPubSoc Europe
10.1002/ejic.201500010
1434-1948
1099-0682
wos:2015
WOS:000352803900012
Holdt, HJ (reprint author), Univ Potsdam, Dept Inorgan Chem, Karl Liebknecht Str 24-25, D-14476 Golm, Germany., Holdt@uni-potsdam.de
Heiko Baier
Alexandra Kelling
Hans-Jürgen Holdt
eng
uncontrolled
Carbene ligands
eng
uncontrolled
Palladium
eng
uncontrolled
Cross-coupling
eng
uncontrolled
Arenes
Institut für Chemie
Referiert
37799
2014
2014
eng
2952
2960
9
18
article
Wiley-VCH
Weinheim
1
--
--
--
Efficient palladium(II) precatalysts bearing 4,5-dicyanoimidazol-2-ylidene for the Mizoroki-Heck reaction
The new N-heterocyclic carbene (NHC) complex [PdCl2{(CN)(2)IMes}(PPh3)] (2) ({(CN)(2)IMes}: 4,5-dicyano-1,3-dimesitylimidazol-2-ylidene) and the NHC palladacycle [PdCl(dmba){(CN)(2)IMes}] (3) (dmba: N,N-dimethylbenzylamine) have been synthesized by thermolysis of 4,5-dicyano-1,3-dimesityl-2-(pentafluorophenyl) imidazoline (1) in the presence of suitable palladium(II) precursors. The acyclic complex 2 was formed by ligand exchange using the mononuclear precursor [PdCl2(PPh3)(2)] and the palladacycle 3 was formed by cleavage of the dinuclear chloro-bridged precursor [Pd(mu-Cl)(dmba)](2). The new NHC precursor 1-benzyl-4,5-dicyano-2-(pentafluorophenyl)-3-picolylimidazoline (5) was formed by condensation of pentafluorobenzaldehyde with N-benzyl-N'-picolyldiaminomaleonitrile (4). The NHC palladacycle [PdCl2{(CN)(2)IBzPic}] (6) ({(CN)(2)IBzPic}: 1-benzyl-4,5-dicyano-3-picolylimidazol-2-ylidene) was prepared by in situ thermolysis of 5 in the presence of [PdCl2(PhCN)(2)]. The three palladium(II) complexes were characterized by NMR and IR spectroscopy, mass spectrometry and elemental analysis. In addition, the molecular structures of 2 and 3 were determined by X-ray diffraction. The pi-acidity of (CN)(2)IBzPic was compared with (CN)(2)IMes and perviously reported pi-acidic imidazol-2-ylidenes by NBO analysis. The Mizoroki-Heck (MH) reactions of various aryl halides with n-butyl acrylate were performed in the presence of complexes 2, 3 and 6. The new precatalysts showed high activity in the MH reactions giving good-to-excellent product yields with 0.1 mol-% pre-catalyst. The nature of the catalytically active species of 2, 3 and 6 was investigated by poisoning experiments with mercury and transmission electron microscopy. It was found that palladium nanoparticles formed from the precatalysts were involved in the catalytic process.
European journal of inorganic chemistry : a journal of ChemPubSoc Europe
10.1002/ejic.201402040
1434-1948
1099-0682
wos:2014
WOS:000338033200009
Holdt, HJ (reprint author), Univ Potsdam, Dept Inorgan Chem, Karl Liebknecht Str 24-25, D-14476 Golm, Germany., Holdt@uni-potsdam.de
Heiko Baier
Philipp Metzner
Thomas Körzdörfer
Alexandra Kelling
Hans-Jürgen Holdt
eng
uncontrolled
Homogeneous catalysis
eng
uncontrolled
Palladium
eng
uncontrolled
Cross coupling
eng
uncontrolled
Carbene ligands
Institut für Chemie
Referiert
34820
2013
2013
eng
1731
1739
9
10
639
article
Wiley-VCH
Weinheim
1
--
--
--
Rhodium(I) and Silver(I) Complexes of 4,5-Dicyano-1,3-dimesityl- and 4,5-Dicyano-1,3-dineopentylimidazol-2-ylidene
The new N-heterocyclic carbene (NHC) precursors 4,5-dicyano-1, -dimesityl- (9) and 4, 5-dicyano-1, 3-dineopentyl-2-(pentafluorophenyl)imidazoline (14) were synthesized. 9 could be determined by X-ray crystallography. With the 2-pentafluorophenyl-substituted imidazolines 9 and 14, the [AgCl(NHC)], [RhCl(COD)(NHC)], and [RhCl(CO)(2)(NHC)] complexes [NHC = 4, 5-dicyano-1, 3-dimesitylimidazol-2-ylidene (3) and 4, 5-dicyano-1, 3-dineopentylimidazol-2-ylidene (4)] were obtained. Crystal structures of [AgCl(3)] (15), [RhCl(COD)(3)] (17), [RhCl(COD)(4)] (18), and [RhCl(CO)(2)(3)] (19) were solved and with the crystal data of 19, the percent buried volume (%V-bur) of 31.8(+/- 0.1)% was determined for NHC 3. Infrared spectra of the imidazolines 9 and 14 and of the complexes 15-20 were recorded and the CO stretching frequencies of complexes 19 and 20 were used to determine the 3 ( (-1)) and 4 ( (-1)), thus proving that 1, 3-substitution of maleonitrile-NHCs does not have a significant effect for the high -acceptor strength of these carbenes.
Zeitschrift für anorganische und allgemeine Chemie
10.1002/zaac.201300250
0044-2313
1521-3749
wos:2011-2013
WOS:000327704000005
Holdt, HJ (reprint author), Univ Potsdam, Chair Inorgan Chem, Karl Liebknecht Str 24-25, D-14476 Golm, Germany., holdt@uni-potsdam.de
Heiko Baier
Alexandra Kelling
Ralf Jackstell
Hans-Jürgen Holdt
eng
uncontrolled
Carbenes
eng
uncontrolled
Rhodium
eng
uncontrolled
Silver
eng
uncontrolled
Crystal structure
eng
uncontrolled
Diaminomaleonitrile
Institut für Chemie
Referiert
30878
2009
2009
eng
article
1
--
--
--
2,11-dialkylated 1,12-diazaperylene copper(I) complexes : first supramolecular column assemblies by pi-pi stacking between homoleptic tetrahedral metal complexes, exhibiting low-energy MLCT transitions
2,11-Dialkylated 1,12-diazaperylenes (alkyl = Me, Et, iPr) dmedap, detdap and dipdap have been synthesized by reductive cyclization of 3,3-dialkylated 1,1-biisoquinolines 3a-c, resulting in the first copper(I) complexes of a large- surface ligand. The new copper(I) complexes show low-energy MLCT absorptions unprecedented for bis(-diimin)copper(I) complexes. The solid structures of the complexes[Cu(dipdap)2]BF4·CH2Cl2·1.5H2O, [Cu(dipdap)2]OTf·CH2Cl2, [Cu(dipdap)2]I·C2H4Cl2·THF·2H2O, [Cu(dmedap)2]OTf and [Cu(dipdap)2]AQSO3·H2O (AQSO3 = sodium 9,10-dihydro-9,10-dioxo-2- anthracenesulfonate) are reported. In [Cu(dipdap)2]BF4·CH2Cl2·1.5H2O, each copper(I) complex cation interacts with two others by - stacking interactions forming a novel supramolecular column structural motif running along the crystallographic c axis. In the crystalline compound [Cu(dipdap)2]AQSO3·H2O, aggregation between two complex cations and two additional anions by - stacking interactions is observed, leading to a tetrameric assembly. Furthermore, the three complex compounds [Cu(L)2]BF4 (L = dmedap, detdap, dipdap) were tested for sensory applications in aqueous buffer solutions in electrochemical studies of the complex immobilized on glassy carbon electrodes.
http://www3.interscience.wiley.com/journal/27721/home
10.1002/ejic.200900695
1434-1948
allegro:1991-2014
10106710
European journal of inorganic chemistry. - ISSN 1434-1948. - (2009), 31, S. 4648 - 4659
Stefan Kammer
Alexandra Kelling
Heiko Baier
Wulfhard Mickler
Carsten Dosche
Knut Rurack
Andreas Kapp
Fred Lisdat
Hans-Jürgen Holdt
Institut für Chemie
Referiert