The bis(aminophenol) 2,2′-biphenylbis(3,5-di- tert -butyl-2-hydroxyphenylamine) (ClipH 4 ) forms trans -(Clip)Os(py) 2 upon aerobic reaction of the ligand with {( p -cymene)OsCl 2 } 2 in the presence of pyridine and triethylamine. A more oxidized species, cis -β-(Clip)Os(OCH 2 CH 2 O), is formed from reaction of the ligand with the osmium( vi ) complex OsO(OCH 2 CH 2 O) 2 , and reacts with Me 3 SiCl to give the chloro complex cis -β-(Clip)OsCl 2 . Octahedral osmium and ruthenium tris-iminoxolene complexes are formed from the chelating ligand tris(2-(3′,5′-di- tert -butyl-2′-hydroxyphenyl)amino-4-methylphenyl)amine (MeClampH 6 ) on aerobic reaction with divalent metal precursors. The complexes’ structural and electronic features are well described using a simple bonding model that emphasizes the covalency of the π bonding between the metal and iminoxolene ligands rather than attempting to dissect the parts into discrete oxidation states. Emphasizing the continuity of bonding between disparate complexes, the structural data from a variety of Os and Ru complexes show good correlations to π bond order, and the response of the intraligand bond distances to the bond order can be analyzed to illuminate the polarity of the bonding between metal and the redox-active orbital on the iminoxolenes. The osmium compounds’ π bonding orbitals are about 40% metal-centered and 60% ligand-centered, with the ruthenium compounds’ orbitals about 65% metal-centered and 35% ligand-centered.
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Catalytic reduction of dinitrogen to silylamines by earth-abundant lanthanide and group 4 complexes
Dinitrogen is a challenging molecule to reduce to useful products under ambient conditions. The range of d-block metal complexes that can catalyze dinitrogen reduction to ammonia or tris(silyl)amines under ambient conditions has increased recently but lacks electropositive metal complexes, such as those of the f-block, which lack filled d-orbitals that would support classical binding modes of N2. Here, metallacyclic phenolate structures with lanthanide or group 4 cations can bind dinitrogen and catalyze its conversion to bis(silyl)amines under ambient conditions. The formation of this unusual product is controlled by metallacycle sterics. The group 4 complexes featuring small cavities are most selective for bis(silyl)amine, while lanthanide complexes and the solvated uranium(IV) congener, with larger cavities, can also make a conventional tris(silyl)amine product. These results offer new catalytic applications for plentiful titanium and more earth-abundant members of the lanthanides that are also less toxic than many base metals used in catalysis.
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- Award ID(s):
- 2154369
- PAR ID:
- 10531863
- Publisher / Repository:
- Chem Catalysis
- Date Published:
- Journal Name:
- Chem Catalysis
- Volume:
- 4
- Issue:
- 5
- ISSN:
- 2667-1093
- Page Range / eLocation ID:
- 100964
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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