low valent
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2022 ◽  
Author(s):  
Philipp Dabringhaus ◽  
Julie Willrett ◽  
Ingo Krossing

Abstract Low-valent aluminium compounds are among the most reactive and widely researched main-group compounds. Since the isolation of [(AlCp*)4] in 1991 as the first stable, molecular AlI compound, a variety of highly reactive neutral or anionic low-valent aluminium complexes were developed. In particular, the strongly basic aluminyl anions allowed for nucleophilic activation of a large variety of small molecules and formation of elusive transition-metal complexes. By contrast, an accessible cationic, low-valent aluminium compound combining the nucleophilicity of low-valent compounds with the electrophilicity of aluminium is hitherto unknown. Here, we report the synthesis of [Al(AlCp*)3]+[Al(ORF)4]– (RF = C(CF3)3) via a simple metathesis route. Unexpectedly, the complex ion forms a dimer in the solid state and in concentrated solutions. Addition of Lewis bases results in monomerization and coordination to the unique formal Al+ atom giving [(L)xAl(AlCp*)3]+ salts with L = hexaphenylcarbodiphosporane (cdp; x = 1), tetramethylethylenediamine (tmeda; x = 1) and 4-dimethylamino-pyridine (dmap; x = 3). Depending on the donor strength of the ligand added, the Al+–AlCp* bonds in the [(L)xAl(AlCp*)3]+ cluster cations can be finely tuned between very strong (L = nothing) to very weak and approaching isolated [Al(L)3]+ ions (L = dmap). We anticipate our easily accessible low-valent aluminium cation salts to be the starting point for investigation and potential application of this unusual compound class. In particular, the ambiphilic reactivity of the cationic, low-valent compounds will be studied. Moreover, knowledge gained from the stabilization of the reported complex salts is expected to facilitate the isolation and application of novel cationic, low-valent Al complexes.


2022 ◽  
Author(s):  
Christoph Helling ◽  
Chelladurai Ganesamoorthy ◽  
Christoph Wölper ◽  
Stephan Schulz

The activation of relatively inert E-X σ-bonds by low-valent main group metal complexes is receiving increasing interest. We here confirm the promising potential of gallanediyl LGa (L = HC[C(Me)N(Dip)]2, Dip...


Author(s):  
Elliot L. B. Johnson Humphrey ◽  
Alan R. Kennedy ◽  
Stephen Sproules ◽  
David James Nelson

2021 ◽  
Vol 118 (52) ◽  
pp. e2113910118
Author(s):  
Yuki Tanahashi ◽  
Kosuke Takahashi ◽  
Yuta Tsubonouchi ◽  
Shunsuke Nozawa ◽  
Shin-ichi Adachi ◽  
...  

The understanding of O–O bond formation is of great importance for revealing the mechanism of water oxidation in photosynthesis and for developing efficient catalysts for water oxidation in artificial photosynthesis. The chemical oxidation of the RuII2(OH)(OH2) core with the vicinal OH and OH2 ligands was spectroscopically and theoretically investigated to provide a mechanistic insight into the O–O bond formation in the core. We demonstrate O–O bond formation at the low-valent RuIII2(OH) core with the vicinal OH ligands to form the RuII2(μ-OOH) core with a μ-OOH bridge. The O–O bond formation is induced by deprotonation of one of the OH ligands of RuIII2(OH)2 via intramolecular coupling of the OH and deprotonated O− ligands, conjugated with two-electron transfer from two RuIII centers to their ligands. The intersystem crossing between singlet and triple states of RuII2(μ-OOH) is easily switched by exchange of H+ between the μ-OOH bridge and the auxiliary backbone ligand.


2021 ◽  
Author(s):  
Jichao Xiao ◽  
John Montgomery

A simple procedure is reported for the nickel-catalyzed defluorinative alkylation of unactivated aliphatic aldehydes. The process involves the catalytic reductive union of trifluoromethyl styrenes with aldehydes using a nickel complex of a 6,6’-disubstituted bipyridine ligand with zinc metal as the terminal reductant. The protocol is distinguished by its broad substrate scope, mild conditions, and simple catalytic setup. Reaction outcomes are consistent with the intermediacy of an alpha-silyloxy(alkyl)nickel intermediate generated by a low-valent nickel catalyst, silyl electrophile, and the aldehyde substrate. Mechanistic findings with cyclopropanecarboxaldehyde provide insights into nature of the reactive intermediates and illustrate fundamental reactivity differences that are governed by subtle changes in ligand and substrate structure.


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