Li M, Gupta SK, Dechert S, Demeshko S, Meyer F. Merging Pincer Motifs and Potential Metal-Metal Cooperativity in Cobalt Dinitrogen Chemistry: Efficient Catalytic Silylation of N
2 to N(SiMe
3 )
3.
Angew Chem Int Ed Engl 2021;
60:14480-14487. [PMID:
33829680 PMCID:
PMC8251579 DOI:
10.1002/anie.202101387]
[Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2021] [Indexed: 12/15/2022]
Abstract
Using a pyrazolate-bridged dinucleating ligand that provides two proximate pincer-type PNN binding sites ("two-in-one pincer"), different synthetic routes have been developed towards its dicobalt(I) complex 2 that features a twice deprotonated ligand backbone and two weakly activated terminal N2 substrate ligands directed into the bimetallic pocket. Protonation of 2 is shown to occur at the ligand scaffold and to trigger conversion to a tetracobalt(I) complex 4 with two end-on μ1,2 -bridging N2 ; in THF 4 is labile and undergoes temperature-dependent N2 /triflate ligand exchange. These pyrazolate-based systems combine the potential of exhibiting both metal-metal and metal-ligand cooperativity, viz. two concepts that have emerged as promising design motifs for molecular N2 fixation catalysts. Complex 2 serves as an efficient (pre)catalyst for the reductive silylation of N2 into N(SiMe3 )3 (using KC8 and Me3 SiCl), yielding up to 240 equiv N(SiMe3 )3 per catalyst.
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