Three-coordinate bipyridyl complexes of gold, (κ2-bipy)Au(η2-C2H4)NTf2, are readily accessed by direct reaction of 2,2′-bipyridine (bipy), or its derivatives, with the homoleptic gold ethylene ...complex Au(C2H4)3NTf2. The cheap and readily available bipyridyl ligands facilitate oxidative addition of aryl iodides to the Au(I) center to give (κ2-bipy)Au(Ar)INTf2, which undergo first aryl-zinc transmetalation and second C–C reductive elimination to produce biaryl products. The products of each distinct step have been characterized. Computational techniques are used to probe the mechanism of the oxidative addition step, offering insight into both the origin of the reversibility of this process and the observation that electron-rich aryl iodides add faster than electron-poor substrates. Thus, for the first time, all steps that are characteristic of a conventional intermolecular Pd(0)-catalyzed biaryl synthesis are demonstrated from a common monometallic Au complex and in the absence of directing groups.
Reversible Dissociation of a Dialumene Falconer, Rosalyn L.; Byrne, Keelan M.; Nichol, Gary S. ...
Angewandte Chemie,
November 8, 2021, Letnik:
60, Številka:
46
Journal Article
Recenzirano
Odprti dostop
Dialumenes are neutral AlI compounds with Al=Al multiple bonds. We report the isolation of an amidophosphine‐supported dialumene. Our X‐ray crystallographic, spectroscopic, and computational DFT ...analyses reveal a long and extreme trans‐bent Al=Al bond with a low dissociation energy and bond order. In solution, the dialumene can dissociate into monomeric AlI species. Reactivity studies reveal two modes of reaction: as dialumene or as aluminyl monomers.
A highly trans‐bent dialumene has marginal Al=Al double‐bond character and, in solution, can dissociate into monomeric aluminyl fragments. Reactivity studies reveal that both the dialuminene and aluminyl monomer can be trapped by varying the reaction partner. DFT calculations elaborate the origins of the extreme trans‐bending, weak Al=Al bond, and define substituent effects in dialumenes.
A room-temperature-stable crystalline 2H-phosphirene (1) was prepared by treatment of an electrophilic diamidocarbene with tert-butylphosphaalkyne. Compound 1 is shown to react as a ...vinylphosphinidene generated via phosphirene–phosphinidene rearrangement. Thermolysis is shown to affect C–N bond scission while reactions with C6Cl4O2 or (tht)AuCl afford formal oxidation of the phosphindene center and the phosphinidene-insertion into an aromatic C–C bond of a mesityl group, respectively. The latter reaction is the first example of a phosphorus analog of the Büchner ring expansion reaction.
Aluminum hydrides, once a simple class of stoichiometric reductants, are now emerging as powerful catalysts for organic transformations such as the hydroboration or hydrogenation of unsaturated ...bonds. The coordination chemistry of aluminum hydrides supported by P donors is relatively underexplored. Here, we report aluminum dihydride and dimethyl complexes supported by amidophosphine ligands and study their coordination behavior in solution and in the solid state. All complexes exist as κ2-N,P complexes in the solid state. However, we find that for amidophosphine ligands bearing bulky aminophosphine donors, aluminum dihydride and dimethyl complexes undergo a “ligand-slip” rearrangement in solution to generate κ2-N,N complexes. Thus, importantly for catalytic activity, we find that the coordination behavior of the P donor can be modulated by controlling its steric bulk. We show that the reported aluminum hydrides catalyze the hydroboration of alkynes by HBPin and that the variable coordination mode exhibited by the amidophosphine ligand modulates the catalytic activity.
Oxidative addition and reductive elimination are defining reactions of transition‐metal organometallic chemistry. In main‐group chemistry, oxidative addition is now well‐established but reductive ...elimination reactions are not yet general in the same way. Herein, we report dihydrodialanes supported by amidophosphine ligands. The ligand serves as a stereochemical reporter for reversible reductive elimination/oxidative addition chemistry involving AlI and AlIII intermediates.
Low‐oxidation‐state main‐group compounds exhibit rich oxidative addition chemistry. The same is not true for the reverse process, reductive elimination. Put together, the processes enable numerous catalytic cycles in transition‐metal chemistry. Here, using a stereoactive ligand as a reporter, it is revealed that AlII dihydrodialanes exhibit transition‐metal‐like reversible reductive elimination. Mes=2,4,6‐trimethylphenyl.
The aromatic heterocycle 2,4,6‐tri‐tert‐butyl‐1,3,5‐triphosphabenzene reacts with a series of silanes, germanes and stannanes, with weaker E−H bonds reacting in an increasingly facile manner. All ...react by 1,4‐addition to give bicyclic products with diastereomeric ratios varying with the substrate. Density functional theory (DFT) calculations show that activation of the E−H bond occurs across the 1,4‐C/P axis of the triphosphabenzene, with the small energetic differences with respect to the stereochemistry of the addition offering insight into the experimentally observed diastereomeric ratios.
The aromatic heterocycle 2,4,6‐tri‐tert‐butyl‐1,3,5‐triphosphabenzene reacts with silanes, germanes and stannanes by initial 1,4‐addition and subsequent rearrangement to give bicyclic products with diastereomeric ratios that vary with the substrate.
Hydroboration of Phosphaalkynes by HB(C6F5)2 Longobardi, Lauren E.; Johnstone, Timothy C.; Falconer, Rosalyn L. ...
Chemistry,
August 26, 2016, Letnik:
22, Številka:
36
Journal Article
Recenzirano
Odprti dostop
The hydroboration of phosphaalkynes with Piers’ borane (HB(C6F5)2) generated unusual phosphaalkenylboranes RCH=PB(C6F5)22 that persisted as dimers in both solution and the solid state. These P2B2 ...heterocycles underwent ring opening when subjected to nucleophiles, such as pyridine and tert‐butylisocyanide, to yield monomeric phosphaalkenylborane adducts RCH=PB(C6F5)2(L). DFT calculations were performed to probe the nature of the interaction of phosphaalkynes with boranes.
Phosphaalkynes were shown to undergo hydroboration with HB(C6F5)2, yielding P2B2 dimeric species that were characterized by solution and solid‐state methods. Rationale for the unexpected regiochemical outcome of this reaction was provided through DFT calculations. These inorganic heterocycles were treated with donors (pyridine and tert‐butylisocyanide) and the corresponding monomeric phophaalkenylborane adducts were formed.
Reversible Dissociation of a Dialumene Falconer, Rosalyn L.; Byrne, Keelan M.; Nichol, Gary S. ...
Angewandte Chemie,
November 8, 2021, Letnik:
133, Številka:
46
Journal Article
Recenzirano
Odprti dostop
Dialumenes are neutral AlI compounds with Al=Al multiple bonds. We report the isolation of an amidophosphine‐supported dialumene. Our X‐ray crystallographic, spectroscopic, and computational DFT ...analyses reveal a long and extreme trans‐bent Al=Al bond with a low dissociation energy and bond order. In solution, the dialumene can dissociate into monomeric AlI species. Reactivity studies reveal two modes of reaction: as dialumene or as aluminyl monomers.
A highly trans‐bent dialumene has marginal Al=Al double‐bond character and, in solution, can dissociate into monomeric aluminyl fragments. Reactivity studies reveal that both the dialuminene and aluminyl monomer can be trapped by varying the reaction partner. DFT calculations elaborate the origins of the extreme trans‐bending, weak Al=Al bond, and define substituent effects in dialumenes.
Oxidative addition and reductive elimination are defining reactions of transition‐metal organometallic chemistry. In main‐group chemistry, oxidative addition is now well‐established but reductive ...elimination reactions are not yet general in the same way. Herein, we report dihydrodialanes supported by amidophosphine ligands. The ligand serves as a stereochemical reporter for reversible reductive elimination/oxidative addition chemistry involving AlI and AlIII intermediates.
Low‐oxidation‐state main‐group compounds exhibit rich oxidative addition chemistry. The same is not true for the reverse process, reductive elimination. Put together, the processes enable numerous catalytic cycles in transition‐metal chemistry. Here, using a stereoactive ligand as a reporter, it is revealed that AlII dihydrodialanes exhibit transition‐metal‐like reversible reductive elimination. Mes=2,4,6‐trimethylphenyl.
•Heavy p-block aromatics.•Main group compounds as transition metals.•Phosphorus as a carbon copy.
In this review, the synthesis, reactivity and theoretical studies on 1,3,5-triphosphorus analogues of ...benzene are discussed including all the literature up to September 2014. Whereas the structure, spectroscopic studies and theory all point towards a significant degree of aromaticity for 1,3,5-triphosphabenzenes, the chemistry that has thus far been demonstrated is largely distinct from its carbocyclic counterparts. This can be ascribed to the substituents that have thus far been employed in 1,3,5-triphosphabenzene synthesis. Hence the discussion of triphosphabenzene reactivity is broken down into four sections describing η1-coordination, η6-coordination, 1,4-addition and ring-contraction reactions. Furthermore, the section on 1,4-addition reactions contains a subsection which highlights the reactions of 1,3,5-triphosphabenzenes with small molecules (principally dihydrogen, alkynes and alkenes), a facet of reactivity that has greater links to the chemistry of transition metals than traditional aromatic chemistry.
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