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C–H Bond Activation Facilitated by Bis(phosphinoamide) Heterobimetallic Zr/Co Complexes

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journal contribution
posted on 2021-10-20, 14:38 authored by Nathanael H. Hunter, Elizabeth M. Lane, Kathryn M. Gramigna, Curtis E. Moore, Christine M. Thomas
The activation of C–H bonds using first-row transition metals poses a formidable challenge in the development of sustainable catalytic methods. Early/late heterobimetallic complexes provide a Lewis acidic binding site for directing groups, facilitating the activation of C–H bonds at an appended first-row transition metal center. Herein, the reactivity of the ZrIV/Co–I heterobimetallic complexes (THF)­(I)­Zr­(XylNPiPr2)2Co­(PR3) (1-PR3; Xyl = 3,5-dimethylphenyl; PR3 = PMe3, PPh2Me) toward directed C–H bond activation is explored with pyridine and terminal alkyne derivatives. 1-PMe3 reacts reversibly with 4-methylpyridine to afford the C–H activated complex (4-Me-C5H4N)­(I)­Zr­(XylNPiPr2)2(μ-4-Me-C5H3N)­Co­(PMe3)­(H) (3-PMe3). By using the more Lewis basic substrate 4-tert-butylpyridine, (I)­Zr­(XylNPiPr2)2(μ-4-tBu-C5H3N)­Co­(PMe3)­(H) (4-PMe3) is formed irreversibly. In addition to pyridine derivatives, 1-PPh2Me can activate the C–H bond of terminal alkynes to form (THF)­(I)­Zr­(XylNPiPr2)2(μ-R′CC)­Co­(PPh2Me)­(H) (R′ = Ph (5-PPh2Me); R′ = SiMe3 (6-PPh2Me)).

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