Journal of the American Chemical SocietyDOI: 10.1021/jacs.1c01486
Stephan M. Rummelt, Paul O. Peterson, Hongyu Zhong, and Paul J. Chirik
https://ift.tt/3wFM03a
Journal of the American Chemical SocietyDOI: 10.1021/jacs.1c01564
Scott M. Chapp and Nathan D. Schley
https://ift.tt/3rDJeaT
Cyclic (alkyl)(amino)carbene (CAAC) precursor salt 2BF4 reacts with [M(PPh3)4] (M=Pd, Pt) to give cis/trans‐[3]BF4 and cis‐[4]BF4, in which the CAAC ligand bears an unusual N‐alkyl substituent. trans‐[5] has a unique anionic CAAC ligand with an unsubstituted ring‐nitrogen atom which can be protonated to give trans‐[6]BF4 bearing a protic CAAC (pCAAC) ligand.
Abstract
CAAC precursors 2‐chloro‐3,3‐dimethylindole 1 and 2‐chloro‐1‐ethyl‐3,3‐dimethylindolium tetrafluoroborate 2BF4 have been prepared and oxidatively added to [M(PPh3)4] (M=Pd, Pt). Salt 2BF4 reacts with [Pd(PPh3)4] in toluene at 25 °C over 4 days to yield complex cis‐[3]BF4 featuring an N‐ethyl substituted CAAC, two cis‐arranged phosphines and a chloro ligand. Compound trans‐[3]BF4 was obtained from the same reaction at 80 °C over 1 day. Salt 2BF4 reacts with [Pt(PPh3)4] to give cis‐[4]BF4. The neutral indole derivative 1 adds oxidatively to [Pt(PPh3)4] to give trans‐[5] featuring a CAAC ligand with an unsubstituted ring‐nitrogen atom. This nitrogen atom has been protonated with py⋅HBF4 to give trans‐[6]BF4 bearing a protic CAAC ligand. The PdII complex trans‐[7]BF4 bearing a protic CAAC ligand was obtained in a one‐pot reaction from 1 and [Pd(PPh3)4] in the presence of py⋅HBF4.
https://ift.tt/33G5isA
Journal of the American Chemical SocietyDOI: 10.1021/jacs.0c09180
Heemal H. Dhanjee, Ivan Buslov, Ian W. Windsor, Ronald T. Raines, Bradley L. Pentelute, and Stephen L. Buchwald
https://ift.tt/3gNzzL7
Mechanical entanglement of the substrate within the coordination sphere of a reactive transition‐metal complex is used as a strategy to access the organometallic chemistry of carbon—carbon bond activation reactions.
Abstract
By use of a macrocyclic phosphinite pincer ligand and bulky substrate substituents, we demonstrate how the mechanical bond can be leveraged to promote the oxidative addition of an interlocked 1,3‐diyne to a rhodium(I) center. The resulting rhodium(III) bis(alkynyl) product can be trapped out by reaction with carbon monoxide or intercepted through irreversible reaction with dihydrogen, resulting in selective hydrogenolysis of the C−C σ‐bond.
https://ift.tt/2H6yVdO
Journal of the American Chemical SocietyDOI: 10.1021/jacs.0c07580
https://ift.tt/2ZuBxs5
The oxidative addition of OH, NH, and weak CH bonds to a palladium(0) complex is facile, allows for additive‐free catalysis, and suggests the non‐innocence of water in palladium catalysis. The oxidative addition of protic solvents or adventitious water switches the chemoselectivity in catalysis with alkynes through activation of the terminal C−H bond.
Abstract
The homolytic cleavage of O−H and N−H or weak C−H bonds is a key elementary step in redox catalysis, but is thought to be unfeasible for palladium. In stark contrast, reported here is the room temperature and reversible oxidative addition of water, isopropanol, hexafluoroisopropanol, phenol, and aniline to a palladium(0) complex with a cyclic (alkyl)(amino)carbene (CAAC) and a labile pyridino ligand, as is also the case in popular N‐heterocyclic carbene (NHC) palladium(II) precatalysts. The oxidative addition of protic solvents or adventitious water switches the chemoselectivity in catalysis with alkynes through activation of the terminal C−H bond. Most salient, the homolytic activation of alcohols and amines allows atom‐efficient, additive‐free cross‐coupling and transfer hydrogenation under mild reaction conditions with usually unreactive, yet desirable reagents, including esters and bis(pinacolato)diboron.
https://ift.tt/3fsCMgO
Journal of the American Chemical SocietyDOI: 10.1021/jacs.0c06995
https://ift.tt/2QAmM25
Two‐in‐one : A (MeDalphos)AuCl complex promotes both oxidative addition of aryl iodides and π‐activation of alkenols/alkenamines. The reaction is robust and general (>30 examples including internal alkenes, 5‐, 6‐, and 7‐membered rings). It is regioselective and leads exclusively to trans addition products.
Abstract
Heteroarylation of alkenes with aryl iodides was efficiently achieved with a (MeDalphos)AuCl complex through AuI/AuIII catalysis. The possibility to combine oxidative addition of aryl iodides and π‐activation of alkenes at gold is demonstrated for the first time. The reaction is robust and general (>30 examples including internal alkenes, 5‐, 6‐, and 7‐membered rings). It is regioselective and leads exclusively to trans addition products. The (P,N) gold complex is most efficient with electron‐rich aryl substrates, which are troublesome with alternative photoredox/oxidative approaches. In addition, it provides a very unusual switch in regioselectivity from 5‐exo to 6‐endo cyclization between the Z and E isomers of internal alkenols.
https://ift.tt/2AQyrVU
Into the fold : Linear HVVH and folded V2(μ‐H)2 have been generated in solid Ne and were detected by infrared spectroscopy. Both molecules are characterized by multiple metal–metal bonding with a high bond order.
Abstract
Dinuclear compounds of early transition metals with a high metal–metal bond order are of fundamental interest due to their intriguing bonding situation and of practical interest because of their potential involvement in catalytic processes. In this work, two isomers of V2H2 have been generated in solid Ne by the reaction between V2 and H2 and detected by infrared spectroscopy: the linear HVVH molecule (3Σg− ground state), which is the product of the spin‐allowed reaction between V2 (3Σg− ground state) and H2, and a lower‐energy, folded V2(μ‐H)2 isomer (1A1 ground state) with two bridging hydrogen atoms. Both isomers are characterized by metal–metal bonding with a high bond order; the orbital occupations point to quadruple bonding. Irradiation with ultraviolet light induces the transformation of linear HVVH to folded V2(μ‐H)2, whereas irradiation with visible light initiates the reverse reaction.
https://ift.tt/3abWXgn
Journal of the American Chemical SocietyDOI: 10.1021/jacs.0c02848
https://ift.tt/2MR9i04
Journal of the American Chemical SocietyDOI: 10.1021/jacs.0c00758
https://ift.tt/33Nnlvn
Journal of the American Chemical SocietyDOI: 10.1021/jacs.9b11507
https://ift.tt/2ULg6l6
I've been under the impression that the oxidative addition in a cross-coupling reaction follows a nucleophilic aromatic substitution mechanism, like described here. I've heard that this is outdated. Is that true? What's the current theory on its mechanism?
The paper I'm referencing: Accounts of Chemical Research, 1977, vol 10, 435.
Or is it one is the subset of the other?
Another question i have: Is there any trend to identify relative sigma donor and pi acceptor/donor strengths of ligands? Is it based on electronegativity or orbitals that the valence electrons are in the ligand or what other factors? I don't want to memorise the order of sigma/pi donors/acceptors for the sake of exams so i'm trying to get a better understanding of it.
http://www.sciencedirect.com/science/article/pii/0022328X94870403
Journal of the American Chemical SocietyDOI: 10.1021/jacs.1c13632
Ting Zhang, Di Zhang, Xinghua Han, Ting Dong, Xinwen Guo, Chunshan Song, Rui Si, Wei Liu, Yuefeng Liu, and Zhongkui Zhao
https://ift.tt/3ETrBKB
Hello, I would like to know the difference between these two different additions as well as ligand dissociation and reductive elimination.
The catalytic asymmetric synthesis of P-chiral phosphorus compounds is an important way to construct P-chiral ligands. Herein, we report a new strategy that adopts the pyridinyl moiety as the coordination group in the cobalt-catalysed asymmetric nucleophilic addition/alkylation of secondary phosphine oxides. A series of tertiary phosphine oxides were generated with up to 99% yield and 99.5% ee with wide functional group tolerances. Mechanistic studies reveal that (R)-secondary phosphine oxides preferentially interact with the cobalt catalysts to produce P-stereogenic compounds.
https://ift.tt/3GWZRH9
Cyclic (alkyl)(amino)carbene (CAAC) precursor salt 2BF4 reacts with [M(PPh3)4] (M=Pd, Pt) to give cis/trans‐[3]BF4 and cis‐[4]BF4, in which the CAAC ligand bears an unusual N‐alkyl substituent. trans‐[5] has a unique anionic CAAC ligand with an unsubstituted ring‐nitrogen atom which can be protonated to give trans‐[6]BF4 bearing a protic CAAC (pCAAC) ligand.
Abstract
CAAC precursors 2‐chloro‐3,3‐dimethylindole 1 and 2‐chloro‐1‐ethyl‐3,3‐dimethylindolium tetrafluoroborate 2BF4 have been prepared and oxidatively added to [M(PPh3)4] (M=Pd, Pt). Salt 2BF4 reacts with [Pd(PPh3)4] in toluene at 25 °C over 4 days to yield complex cis‐[3]BF4 featuring an N‐ethyl substituted CAAC, two cis‐arranged phosphines and a chloro ligand. Compound trans‐[3]BF4 was obtained from the same reaction at 80 °C over 1 day. Salt 2BF4 reacts with [Pt(PPh3)4] to give cis‐[4]BF4. The neutral indole derivative 1 adds oxidatively to [Pt(PPh3)4] to give trans‐[5] featuring a CAAC ligand with an unsubstituted ring‐nitrogen atom. This nitrogen atom has been protonated with py⋅HBF4 to give trans‐[6]BF4 bearing a protic CAAC ligand. The PdII complex trans‐[7]BF4 bearing a protic CAAC ligand was obtained in a one‐pot reaction from 1 and [Pd(PPh3)4] in the presence of py⋅HBF4.
https://ift.tt/33G5isA
Journal of the American Chemical SocietyDOI: 10.1021/jacs.0c08506
https://ift.tt/36pooVu
Journal of the American Chemical SocietyDOI: 10.1021/jacs.0c06703
https://ift.tt/2ZoRXBB
Journal of the American Chemical SocietyDOI: 10.1021/jacs.0c03143
https://ift.tt/3dC2zme
The homolytic cleavage of O‒H and N‒H or weak C‒H bonds is a key elementary step in redox catalysis, yet thought to be unfeasible for palladium. In stark contrast, we report the room temperature and reversible oxidative addition of water, isopropanol, hexafluoroisopropanol, phenol, and aniline to a palladium(0) complex with a very labile pyridino ligand thus resembling pervasive N‐heterocyclic carbene (NHC) palladium(II) pre‐catalysts. We elucidate how the oxidative addition of protic solvents or adventitious water switches the chemoselectivity in palladium catalysis with alkynes through activation of the terminal C‒H bond. Most salient, the homolytic activation of alcohols and amines allows for atom‐efficient, additive‐free cross coupling and transfer hydrogenation under mild reaction conditions with usually unreactive, yet desirable reagents including esters and bis(pinacolato)diboron.
https://ift.tt/3fsCMgO
The hetero‐arylation of alkenes with aryl iodides has been efficiently achieved with the (MeDalphos)AuCl complex via Au(I)/Au(III) catalysis. The possibility to combine oxidative addition of aryl iodides and π‐activation of alkenes at gold is demonstrated for the first time. The reaction is robust and general (>30 examples including internal alkenes, 5, 6 and 7‐membered rings). It is regioselective and leads exclusively to trans addition products. The (P,N) gold complex is most efficient with electron‐rich aryl substrates, which are troublesome with alternative photoredox / oxidative approaches. In addition, it actuates a very unusual switch in regioselectivity from 5‐exo to 6‐endo cyclization between the Z and E isomers of internal alkenols.
https://ift.tt/2zR4iW5
Into the fold: Linear HVVH and folded V2(μ‐H)2 have been generated in solid Ne and were detected by infrared spectroscopy. Both molecules are characterized by multiple metal–metal bonding with a high bond order.
Abstract
Dinuclear compounds of early transition metals with a high metal–metal bond order are of fundamental interest due to their intriguing bonding situation and of practical interest because of their potential involvement in catalytic processes. In this work, two isomers of V2H2 have been generated in solid Ne by the reaction between V2 and H2 and detected by infrared spectroscopy: the linear HVVH molecule (3Σg− ground state), which is the product of the spin‐allowed reaction between V2 (3Σg− ground state) and H2, and a lower‐energy, folded V2(μ‐H)2 isomer (1A1 ground state) with two bridging hydrogen atoms. Both isomers are characterized by metal–metal bonding with a high bond order; the orbital occupations point to quadruple bonding. Irradiation with ultraviolet light induces the transformation of linear HVVH to folded V2(μ‐H)2, whereas irradiation with visible light initiates the reverse reaction.
https://ift.tt/3abWXgn
Dinuclear compounds of early transition metals with a high metal‐metal bond‐order are of fundamental interest due to their intriguing bonding situation and of practical interest because of their potential involvement in catalytic processes. In this work, two isomers of V 2 H 2 have been generated in solid Ne by reaction between V 2 and H 2 and detected by infrared spectroscopy. The linear HVVH molecule ( 3 Σ g − ground term), being the product of the spin‐allowed reaction between V 2 ( 3 Σ g − ground term) and H 2 , and a lower‐energy, folded V 2 (μ‐H) 2 isomer ( 1 A 1 ground term) with two bridging hydrogen atoms. Both isomers are characterized by metal‐metal bonding with a high bond‐order, the orbital occupations point to quadruple bonding. Irradiation with ultraviolet light induces the transformation of linear HVVH to folded V 2 (μ‐H) 2 , whereas irradiation with visible light initiates the reverse reaction.
https://ift.tt/3abWXgn
Journal of the American Chemical SocietyDOI: 10.1021/jacs.0c01466
https://ift.tt/3c0hPZj
