A cyclic alkyl(amino)carbene‐stabilized 1,4‐diborabenzene (DBB) ligand enables the isolation of 18‐electron two‐legged parent piano‐stool Fe0 and Ru0 complexes, (η6‐DBB)M(CO)2, the ruthenium complex ...being the first of its kind to be structurally characterized. (η6‐DBB)Fe(CO)2 reacts with E4 (E=P, As) to yield mixed DBB‐cyclo‐E4 sandwich complexes with planar E42− ligands. Computational analyses confirm the strong electron‐donating capacity of the DBB ligand and show that the E4 ligand is bound by four equivalent Fe−P σ bonds.
A cyclic alkyl(amino)carbene‐stabilized 1,4‐diborabenzene ligand enables the isolation of thermally stable two‐legged parent piano‐stool Fe0 and Ru0 complexes. The iron complex reacts with P4 and As4 to yield mixed diborabenzene‐cyclo‐E4 sandwich complexes with planar E42− ligands. Computational analyses confirm the strong electron‐donating capacity of the DBB ligand and show that the E4 ligand is bound by four equivalent Fe−P σ bonds.
Magnesium‐based catalysts are becoming popular for hydroelementation reactions specially using p‐block reagents. Based on the seminal report from Schäfer's group (ChemCatChem 2022, 14, e202201007), ...our study demonstrates that the reaction mechanisms exhibit a far greater degree of complexity than originally presumed. Magnesium has a variety of coordination modes (and access to different hybridizations) which allows this electron‐deficient centre to modulate its catalytic power depending on the σ‐donor properties of the reagent. DFT calculations demonstrate several reaction channels closely operating in these versatile catalysts. In addition, variations in limiting energy barriers resulting from catalyst modifications were examined as a function of the Hammett constant, thereby predicting enhanced efficiency in reaction conversions.
Show me how many ligands you accept, and I will tell you how you react: depending on the number of ligands that the ansa‐half‐sandwich magnesium catalyst can bind, our DFT calculations show that the mechanism proceeds differently with competitive reaction channels.
Synthetic strategies to access high-valent iridium complexes usually require use of π donating ligands bearing electronegative atoms (e.g. amide or oxide) or σ donating electropositive atoms (e.g. ...boryl or hydride). Besides the η5-(methyl)cyclopentadienyl derivatives, high-valent η1 carbon-ligated iridium complexes are challenging to synthesize. To meet this challenge, this work reports the oxidation behavior of an all-carbon-ligated anionic bis(CCC-pincer) IrIII complex. Being both σ and π donating, the diaryl dipyrido-annulated N-heterocyclic carbene (dpa-NHC) IrIII complex allowed a stepwise 4e- oxidation sequence. The first 2e- oxidation led to an oxidative coupling of two adjacent aryl groups, resulting in formation of a cationic chiral IrIII complex bearing a CCCC-tetradentate ligand. A further 2e- oxidation allowed isolation of a high-valent tricationic complex with a triplet ground state. These results close a synthetic gap for carbon-ligated iridium complexes and demonstrate the electronic tuning potential of organic π ligands for unusual electronic properties.
Generation of dihydrogen from water splitting, also known as water reduction, is a key process to access a sustainable hydrogen economy for energy production and usage. The key step is the selective ...reduction of a protic hydrogen to an accessible and reactive hydride, which has proven difficult at a p-block element. Although frustrated Lewis pair (FLP) chemistry is well known for water activation by heterolytic H-OH bond cleavage, to the best of our knowledge, there has been only one case showing water reduction by metal-free FLP systems to date, in which silylene (Si
) was used as the Lewis base. This work reports the molecular design and synthesis of an
-phenylene linked bisborane-functionalized phosphine, which reacts with water stoichiometrically to generate H
and phosphine oxide quantitatively under ambient conditions. Computational investigations revealed an unprecedented multi-centered electron relay mechanism offered by the molecular framework, shuttling a pair of electrons from hydroxide (OH
) in water to the separated proton through a borane-phosphonium-borane path. This simple molecular design and its water reduction mechanism opens new avenues for this main-group chemistry in their growing roles in chemical transformations.
The first iodine(III)‐mediated para‐selective iodination protocol for free anilines as well as the mechanistic elucidation of the reaction pathway is described. The developed method proceeded under ...clean, non‐toxic, efficient, and in general mild reaction conditions. To the best of our knowledge this report describes for the first time a procedure focused specifically on the introduction of an iodine atom in free anilines using PIDA (diacetoxyiodo)benzene and ammonium iodide which formed in situ acetyl hypoiodite (AcO‐I) as the halogenating species. Our DFT calculations suggest a reaction mechanism that highlights the catalytic role of the ammonium cation in the AcO‐I formation and halogenation. Considering there are few procedures for the iodine atom introduction in anilines using non‐acidic conditions, herein we described an initial report on a mild and operationally simple alternative using iodine(III) reagents.
The first iodine(III)‐mediated para‐selective iodination of free anilines through the in situ formed acetyl hypoiodite as halogenating species is described. This procedure allows a cheap, efficient, and easy way to get acetyl hypoiodite in less than 2 minutes by combining PIDA and NH4I. Experimental and theoretical calculations supported the mechanism that proceeds under mild conditions.
Abstract
A cyclic alkyl(amino)carbene‐stabilized 1,4‐diborabenzene (DBB) ligand enables the isolation of 18‐electron two‐legged parent piano‐stool Fe
0
and Ru
0
complexes, (η
6
‐DBB)M(CO)
2
, the ...ruthenium complex being the first of its kind to be structurally characterized. (η
6
‐DBB)Fe(CO)
2
reacts with E
4
(E=P, As) to yield mixed DBB‐
cyclo
‐E
4
sandwich complexes with planar E
4
2−
ligands. Computational analyses confirm the strong electron‐donating capacity of the DBB ligand and show that the E
4
ligand is bound by four equivalent Fe−P σ bonds.
Ein cyclisches Alkyl(amino)carben‐stabilisierter 1,4‐Diborabenzol‐Ligand (DBB) ermöglichte die Isolierung von zweibeinigen 18‐Elektronen Klavierstuhl‐Komplexen von Fe0 und Ru0 der Form ...(η6‐DBB)M(CO)2, wobei der Rutheniumkomplex der erste seiner Art ist, der strukturell charakterisiert wurde. (η6‐DBB)Fe(CO)2 reagierte mit E4 (E=P, As) unter Ausbildung von gemischten DBB‐cyclo‐E4‐Sandwichkomplexen mit planaren E42− Liganden. Quantenchemische Berechnungen bestätigen die hohe Elektrondonorstärke des DBB Liganden und zeigen, dass die E4‐Liganden über vier äquivalente Fe‐P‐σ‐Bindungen gebunden sind.
Ein cyclisches Alkyl(amino)carben‐stabilisierter 1,4‐Diborabenzol‐Ligand ermöglicht die Isolation von thermisch stabilen zweibeinigen Fe0‐ und Ru0‐Klavierstuhl‐Komplexen. Der Eisenkomplex reagiert mit P4 und As4 unter Ausbildung von gemischten Diborabenzol‐cyclo‐E4‐Sandwichkomplexen mit planaren E42−‐Liganden. Quantenchemische Berechnungen bestätigen die hohe Elektrondonorstärke des DBB Liganden und zeigen, dass die E4‐Liganden über vier äquivalente Fe‐P‐σ‐Bindungen gebunden sind.
Abstract
Synthetic strategies to access high‐valent iridium complexes usually require use of π donating ligands bearing electronegative atoms (e. g. amide or oxide) or σ donating electropositive ...atoms (e. g. boryl or hydride). Besides the η
5
‐(methyl)cyclopentadienyl derivatives, high‐valent η
1
carbon‐ligated iridium complexes are challenging to synthesize. To meet this challenge, this work reports the oxidation behavior of an all‐carbon‐ligated anionic bis(
CCC‐
pincer) Ir
III
complex. Being both σ and π donating, the diaryl dipyrido‐annulated
N
‐heterocyclic carbene (dpa‐NHC) Ir
III
complex allowed a stepwise 4e
−
oxidation sequence. The first 2e
−
oxidation led to an oxidative coupling of two adjacent aryl groups, resulting in formation of a cationic chiral Ir
III
complex bearing a CCCC‐tetradentate ligand. A further 2e
−
oxidation allowed isolation of a high‐valent tricationic complex with a triplet ground state. These results close a synthetic gap for carbon‐ligated iridium complexes and demonstrate the electronic tuning potential of organic π ligands for unusual electronic properties.
Abstract
Ein cyclisches Alkyl(amino)carben‐stabilisierter 1,4‐Diborabenzol‐Ligand (DBB) ermöglichte die Isolierung von zweibeinigen 18‐Elektronen Klavierstuhl‐Komplexen von Fe
0
und Ru
0
der Form (η
...6
‐DBB)M(CO)
2
, wobei der Rutheniumkomplex der erste seiner Art ist, der strukturell charakterisiert wurde. (η
6
‐DBB)Fe(CO)
2
reagierte mit E
4
(E=P, As) unter Ausbildung von gemischten DBB‐
cyclo
‐E
4
‐Sandwichkomplexen mit planaren E
4
2−
Liganden. Quantenchemische Berechnungen bestätigen die hohe Elektrondonorstärke des DBB Liganden und zeigen, dass die E
4
‐Liganden über vier äquivalente Fe‐P‐σ‐Bindungen gebunden sind.
Generation of dihydrogen from water splitting, also known as water reduction, is a key process to access a sustainable hydrogen economy for energy production and usage. The key step is the selective ...reduction of a protic hydrogen to an accessible and reactive hydride, which has proven difficult at a p-block element. Although frustrated Lewis pair (FLP) chemistry is well known for water activation by heterolytic H-OH bond cleavage, to the best of our knowledge, there has been only one case showing water reduction by metal-free FLP systems to date, in which silylene (Si
II
) was used as the Lewis base. This work reports the molecular design and synthesis of an
ortho
-phenylene linked bisborane-functionalized phosphine, which reacts with water stoichiometrically to generate H
2
and phosphine oxide quantitatively under ambient conditions. Computational investigations revealed an unprecedented multi-centered electron relay mechanism offered by the molecular framework, shuttling a pair of electrons from hydroxide (OH
−
) in water to the separated proton through a borane-phosphonium-borane path. This simple molecular design and its water reduction mechanism opens new avenues for this main-group chemistry in their growing roles in chemical transformations.
A (bisborane)triarylphosphine was developed to spontaneously generate H
2
from water under ambient conditions, revealing an unprecedented multi-centered electron relay mechanism for a metal-free umpolung of proton to hydride.
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