Emergence of a New [NNN] Pincer Ligand via Si−H Bond Activation and β‐Hydride Abstraction at Tetravalent Cerium. Issue 53 (7th September 2020)

• Record Type: Journal Article
• Authors: Werner, Daniel; Bayer, Uwe; Schädle, Dorothea; Anwander, Reiner
• Is Part Of: Chemistry. Volume 26:Issue 53(2020)
• Page Start: 12194
• Page End: 12205
• Publication Date: 2020-09-07
• Subjects: cerium -- hydride abstraction -- lithium -- pincer ligands -- silicon; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.202000625
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: The cerium(IV) pyrazolate complexes [Ce(Me2 pz)4 ]2 and [Ce(Me2 pz)4 (thf)] initiate β‐hydride abstraction of the bis(dimethylsilyl)amido moiety, to afford a heteroleptic cerium(IV) species containing a dimethylpyrazolyl‐substituted silylamido ligand, namely [Ce(Me2 pz)3 (bpsa)] (bpsa=bis((3, 5‐dimethylpyrazol‐1‐yl)dimethylsilyl)amido; Me2 pz =3, 5‐dimethylpyrazolato), along with some cerium(III) species. Remarkably, the nucleophilic attack of the pyrazolyl at the silicon atom and concomitant Si−H‐bond cleavage is restricted to the tetravalent cerium oxidation state and appears to proceed via the formation of a transient cerium(IV) hydride, which engages in immediate redox chemistry. When [Ce(Me2 pz)4 ]2 is treated with [Li{N(SiMe3 )2 }], that is, in the absence of the SiH functionality, any redox chemistry did not occur. Instead, the ceric ate complex [LiCe2 (Me2 pz)9 ] and the stable mixed‐ligand ceric species [Ce(Me2 pz)2 {N(SiMe3 )2 }2 ] were obtained. Abstract : Putative heteroleptic ceric species [Ce(Me2 pz) x {N(SiHMe2 )2 }4− x ] promote the formation of a new monoanionic dipyrazolylamido pincer ligand, while both tetravalent [Ce(Me2 pz)2 {N(SiMe3 )2 }2 ] and trivalent [Li2 (thf)2 Ce(Me2 pz)2 {N(SiHMe2 )2 }3 ] are isolable and stable.