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Sengupta D, Sandoval-Pauker C, Schueller E, Encerrado-Manriquez AM, Metta-Magaña A, Lee WY, Seshadri R, Pinter B, Fortier S. Isolation of a Bimetallic Cobalt(III) Nitride and Examination of Its Hydrogen Atom Abstraction Chemistry and Reactivity toward H 2. J Am Chem Soc 2020; 142:8233-8242. [PMID: 32279486 DOI: 10.1021/jacs.0c00291] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Room temperature photolysis of the bis(azide)cobaltate(II) complex [Na(THF)x][(ketguan)Co(N3)2] (ketguan = [(tBu2CN)C(NDipp)2]-, Dipp = 2,6-diisopropylphenyl) (3a) in THF cleanly forms the binuclear cobalt nitride Na(THF)4{[(ketguan)Co(N3)]2(μ-N)} (1). Compound 1 represents the first example of an isolable, bimetallic cobalt nitride complex, and it has been fully characterized by spectroscopic, magnetic, and computational analyses. Density functional theory supports a CoIII═N═CoIII canonical form with significant π-bonding between the cobalt centers and the nitride atom. Unlike other group 9 bridging nitride complexes, no radical character is detected at the bridging N atom of 1. Indeed, 1 is unreactive toward weak C-H donors and even cocrystallizes with a molecule of cyclohexadiene (CHD) in its crystallographic unit cell to give 1·CHD as a room temperature stable product. Notably, addition of pyridine to 1 or photolyzed solutions of [(ketguan)Co(N3)(py)]2 (4a) leads to destabilization via activation of the nitride unit, resulting in the mixed-valent Co(II)/Co(III) bridged imido species [(ketguan)Co(py)][(ketguan)Co](μ-NH)(μ-N3) (5) formed from intermolecular hydrogen atom abstraction (HAA) of strong C-H bonds (BDE ∼ 100 kcal/mol). Kinetic rate analysis of the formation of 5 in the presence of C6H12 or C6D12 gives a KIE = 2.5 ± 0.1, supportive of a HAA formation pathway. The reactivity of our system was further probed by photolyzing benzene/pyridine solutions of 4a under H2 and D2 atmospheres (150 psi), which leads to the exclusive formation of the bis(imido) complexes [(ketguan)Co(μ-NH)]2 (6) and [(ketguan)Co(μ-ND)]2 (6-D), respectively, as a result of dihydrogen activation. These results provide unique insights into the chemistry and electronic structure of late 3d metal nitrides while providing entryway into C-H activation pathways.
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Affiliation(s)
- Debabrata Sengupta
- Department of Chemistry and Biochemistry, University of Texas at El Paso, El Paso, Texas 79968, United States
| | | | - Emily Schueller
- Materials Department and Materials Research Laboratory, University of California, Santa Barbara, Santa Barbara, California 93106, United States
| | | | - Alejandro Metta-Magaña
- Department of Chemistry and Biochemistry, University of Texas at El Paso, El Paso, Texas 79968, United States
| | - Wen-Yee Lee
- Department of Chemistry and Biochemistry, University of Texas at El Paso, El Paso, Texas 79968, United States
| | - Ram Seshadri
- Materials Department and Materials Research Laboratory, University of California, Santa Barbara, Santa Barbara, California 93106, United States.,Department of Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, California 93106, United States
| | - Balazs Pinter
- Department of Chemistry, Universidad Técnica Federico Santa María, Valparaíso 2390123, Chile
| | - Skye Fortier
- Department of Chemistry and Biochemistry, University of Texas at El Paso, El Paso, Texas 79968, United States
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