Electronic structure studies reveal 4f/5d mixing and its effect on bonding characteristics in Ce-imido and -oxo complexes. Issue 6 (24th January 2022)

• Record Type: Journal Article
• Authors: Moreau, Liane M.; Lapsheva, Ekaterina; Amaro-Estrada, Jorge I.; Gau, Michael R.; Carroll, Patrick J.; Manor, Brian C.; Qiao, Yusen; Yang, Qiaomu; Lukens, Wayne W.; Sokaras, Dimosthenis; Schelter, Eric J.; Maron, Laurent; Booth, Corwin H.
• Is Part Of: Chemical science. Volume 13:Issue 6(2022)
• Page Start: 1759
• Page End: 1773
• Publication Date: 2022-01-24
• Subjects: Chemistry -- Periodicals; 540.5
• DOI: 10.1039/d1sc06623d
• Languages: English
• ISSNs: 2041-6520

Abstract

Abstract : Ce(iv ) complexes with multiple bonds display similar f 0 fractions, but different f/d hybridization, 5d-orbital energies, and TIP levels. Abstract : This study presents the role of 5d orbitals in the bonding, and electronic and magnetic structure of Ce imido and oxo complexes synthesized with a tris(hydroxylaminato) [((2- t BuNO)C6 H4 CH2 )3 N] 3− (TriNO x 3− ) ligand framework, including the reported synthesis and characterization of two new alkali metal-capped Ce oxo species. X-ray spectroscopy measurements reveal that the imido and oxo materials exhibit an intermediate valent ground state of the Ce, displaying hallmark features in the Ce LIII absorption of partial f-orbital occupancy that are relatively constant for all measured compounds. These spectra feature a double peak consistent with other formal Ce(iv ) compounds. Magnetic susceptibility measurements reveal enhanced levels of temperature-independent paramagnetism (TIP). In contrast to systems with direct bonding to an aromatic ligand, no clear correlation between the level of TIP and f-orbital occupancy is observed. CASSCF calculations defy a conventional van Vleck explanation of the TIP, indicating a single-reference ground state with no low-lying triplet excited state, despite accurately predicting the measured values of f-orbital occupancy. The calculations do, however, predict strong 4f/5d hybridization. In fact, within these complexes, despite having similar f-orbital occupancies and therefore levels of 4f/5d hybridization, the d-state distributions vary depending on the bonding motif (CeO vs. CeN) of the complex, and can also be fine-tuned based on varying alkali metal cation capping species. This system therefore provides a platform for understanding the characteristic nature of Ce multiple bonds and potential impact that the associated d-state distribution may have on resulting reactivity.