Schwefeldioxid als Ligand und Synthon. XII. Synthese und Reaktivität von Nickel(II)‐Komplexen dreizähniger anionischer Liganden des Typs (C6H3{CH2NR1R2}2‐2,6)−

Schimmelpfennig, U.; Zimmering, René; Schleinitz, Klaus‐Dieter; R, Stösser; Wenschuh, Eberhard; Baumeister, U.; Hartung, H.

doi:10.1002/zaac.19936191118

Cited by 23 publications

(13 citation statements)

References 9 publications

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“…We prepared this ligand via a recently develw x oped enantioselective route 23 outlined in Scheme 2. The absolute stereochemistry of the product was hitherto unknown but has now been established by the structural characterization of 5 5 .…”

Section: Discussionmentioning

confidence: 99%

Synthesis of arylplatinum(II) complexes with chiral monoanionic aryldiamine ligands.

Donkervoort

Vicario

Jastrzebski

et al. 1998

Journal of Organometallic Chemistry

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The new chiral arylplatinum II compounds 2,6-bis 1-dimethylamino ethyl phenyl chloroplatinum II 4 and y -1R,1 R -bis 1-Ž . . x Ž . Ž . dimethylamino propyl phenyl chloroplatinum II 5 have been synthesized. The transmetallation of the corresponding aryllithium compounds does not affect either stereogenic centres of the organic ligand while the rate of the transmetallation is shown to be influenced by the size of the benzylic substituents. The X-ray crystal structure of 5 is reported from which the absolute configuration of both Ž . stereogenic centres of the organic ligand was determined to be R . q 1998 Elsevier Science B.V.

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Section: Discussionmentioning

confidence: 99%

Synthesis of arylplatinum(II) complexes with chiral monoanionic aryldiamine ligands.

Donkervoort

Vicario

Jastrzebski

et al. 1998

Journal of Organometallic Chemistry

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“…Their Ni(II) complexes generally have a square-planar metal geometry with the direct M−C aryl σ-bond flanked by two, mutually trans-positioned, ortho-chelating, tertiary amino substituents. The group X is trans to the aryl unit . We have already reported that the para -substituent (R) influences the Ni(II)/Ni(III) redox potential in such aryldiaminenickel(II) complexes and we have shown that other modifications of the ligand system can influence (through both steric and electronic factors) both catalysis 11,15c and ligand coordination modes 15b…”

Section: Introductionmentioning

confidence: 99%

“…The controlled radical polymerization concept has been extended by Matyjaszewski and co-workers 7d,e for the bulk polymerization of styrene and MMA. This process uses a CuX/2,2‘-bipyridine catalyst which is similar to many of the Cu halide/amine systems that are used in Kharasch addition reactions. − A recent report by Teyssié and collaborators details the similar use of the arylnickel(II) complex ( 1 ), first synthesized in this laboratory, ,15a in a similar manner for a well-controlled radical polymerization of MMA at rather moderate temperatures 7h. This report is highly relevant to the interpretation of the new results reported herein.…”

Section: Introductionmentioning

confidence: 99%

Mechanistic Aspects of the Kharasch Addition Reaction Catalyzed by Organonickel(II) Complexes Containing the Monoanionic Terdentate Aryldiamine Ligand System [C₆H₂(CH₂NMe₂)₂-2,6-R-4]^-

et al. 1997

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The addition reaction of polyhalogenated alkanes to alkenes (Kharasch addition reaction) is homogeneously catalyzed in the absence of O 2 under mild reaction conditions (25°C) by the arylnickel complexes [Ni II {C 6 H 2 (CH 2 NMe 2 ) 2 -2,6-R-4}Br] (R ) H, MeC(O), Cl, MeO, NH 2 ) and shows a high selectivity for the 1:1 adduct. Kinetic data on the catalytic system with [Ni{C 6 H 3 (CH 2 NMe 2 ) 2 -2,6}Br] (R ) H; abbreviated as [Ni(NCN)Br]), methyl methacrylate, and CCl 4 reveal a rate of reaction that is first order in nickel complex and in alkene. In our series of para-substituted arylnickel catalysts, the rate of catalysis increases with the electron donating character of the para substituents on the aryl ligand and this rate correlates directly with the Ni II /Ni III redox potential. These data, together with separate spectroscopic studies and results from individual experiments employing other solvents, other polyhalogenated alkanes such as CBr 4 and CF 3 CCl 3 and other alkene substrates such as styrene, 1-octene, and cyclohexene, lead to the proposal of a catalytic cycle based on a nonchain mechanism with a mononuclear nickel species. Before or in the rate-determining step oxidation of the Ni(II) center to a d 7 arylnickel(III) species occurs by a single electron transfer and halide transfer from the polyhalogenated alkane in an inner-sphere activated complex [Ni(NCN)-(µ-Cl)CCl 4 ]. This step generates an organic radical intermediate which is proposed to stay in the coordination sphere of the metal where it reacts with the alkene. The reaction rate decreases with an increase in the steric congestion at the N-donor centers in derivatives of the [Ni(NCN)Br] catalyst (i.e., NMe 2 > NEt 2 > NMe(i-Pr) > NMe(t-Bu)). This behavior is consistent with the characteristics for an inner-sphere electron-transfer process. Selective 1:1 Kharasch product formation then results from a chain transfer in the Ni(III) coordination sphere by the reverse process, i.e., single electron transfer with concomitant halide transfer. Important conclusions of this study are that the initially active site of the catalyst is the Ni-X unit (X ) halide) and that activation of CCl 4 occurs in the absence of a free coordination site.

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“…Importantly, the Lewis basic character of NCN pincer complexes is strongly dependent on the functional groups on the donor sites. An increase in the steric bulk from E=NMe 2 to NEt 2 is sufficient to induce an efficient shielding of the metal z ‐axis and therefore prevents the formation of these Lewis acid–base complexes even though NEt 2 is more basic than NMe 2 (Scheme ) 30b, 56…”

Section: New Materials Propertiesmentioning

confidence: 99%

Sensitive analysis of anti‐HIV drugs, efavirenz, lopinavir and ritonavir, in human hair by liquid chromatography coupled with tandem mass spectrometry

Huang

Gandhi

Greenblatt

et al. 2008

Rapid Comm Mass Spectrometry

116

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A highly sensitive and selective method using liquid chromatography coupled with tandem mass spectrometry (LC/MS/MS) was developed and validated for the measurement of three antiretroviral agents, efavirenz, lopinavir and ritonavir, in human hair. Hair samples from adherent HIV-infected patients on antiretroviral therapies were cut into about 1 mm length segments and drugs were extracted by first shaking the samples with methanol in a 37°C water bath overnight (>14 h), followed by methyl tert-butyl ether/ethyl acetate (1:1) extraction under weak alkaline conditions. The extracted lopinavir and ritonavir were separated by reversed-phase chromatography and detected by tandem mass spectrometry in electrospray positive ionization mode with multiple reaction monitoring (MRM), while efavirenz was monitored in negative ionization MRM mode. This method was validated from 0.01 to 4.0 ng/mg hair for ritonavir and 0.05–20 ng/mg hair for lopinavir and efavirenz by using 2 mg of a human hair sample. The interday and intraday assay precision (coefficients of variation, CV) for spiked quality control (QC) samples at low, medium and high concentrations were within 15% and accuracy ranged from 89% to 110%. Assay reproducibility was also demonstrated by analysis of incurred hair QC samples (CV <14%). No significant matrix ionization suppression was observed. This developed method allowed for the monitoring of these target medications in the hair samples of HIV-infected women on antiretroviral therapy in an observational study using small amounts of hair.

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Schwefeldioxid als Ligand und Synthon. XII. Synthese und Reaktivität von Nickel(II)‐Komplexen dreizähniger anionischer Liganden des Typs (C₆H₃{CH₂NR¹R²}₂‐2,6)⁻

Cited by 23 publications

References 9 publications

Synthesis of arylplatinum(II) complexes with chiral monoanionic aryldiamine ligands.

Synthesis of arylplatinum(II) complexes with chiral monoanionic aryldiamine ligands.

Mechanistic Aspects of the Kharasch Addition Reaction Catalyzed by Organonickel(II) Complexes Containing the Monoanionic Terdentate Aryldiamine Ligand System [C₆H₂(CH₂NMe₂)₂-2,6-R-4]^-

Sensitive analysis of anti‐HIV drugs, efavirenz, lopinavir and ritonavir, in human hair by liquid chromatography coupled with tandem mass spectrometry

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Schwefeldioxid als Ligand und Synthon. XII. Synthese und Reaktivität von Nickel(II)‐Komplexen dreizähniger anionischer Liganden des Typs (C6H3{CH2NR1R2}2‐2,6)−

Cited by 23 publications

References 9 publications

Synthesis of arylplatinum(II) complexes with chiral monoanionic aryldiamine ligands.

Synthesis of arylplatinum(II) complexes with chiral monoanionic aryldiamine ligands.

Mechanistic Aspects of the Kharasch Addition Reaction Catalyzed by Organonickel(II) Complexes Containing the Monoanionic Terdentate Aryldiamine Ligand System [C6H2(CH2NMe2)2-2,6-R-4]-

Sensitive analysis of anti‐HIV drugs, efavirenz, lopinavir and ritonavir, in human hair by liquid chromatography coupled with tandem mass spectrometry

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Schwefeldioxid als Ligand und Synthon. XII. Synthese und Reaktivität von Nickel(II)‐Komplexen dreizähniger anionischer Liganden des Typs (C₆H₃{CH₂NR¹R²}₂‐2,6)⁻

Mechanistic Aspects of the Kharasch Addition Reaction Catalyzed by Organonickel(II) Complexes Containing the Monoanionic Terdentate Aryldiamine Ligand System [C₆H₂(CH₂NMe₂)₂-2,6-R-4]^-