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Synthesis and Reactivity of Zr MOFs Assembled from PNNNP‑Ru Pincer Complexes

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journal contribution
posted on 06.09.2019, 15:46 by Abebu A. Kassie, Pu Duan, Matthew B. Gray, Klaus Schmidt-Rohr, Patrick M. Woodward, Casey R. Wade
Three isostructural Zr metal–organic frameworks have been synthesized from PNNNP-Ru pincer metallolinkers bearing different combinations of ancillary ligands (1, Zr6O4­(OH)4(­OAc)4{cis-(PNNNP)­RuCl2­(CO)}2; 2, Zr6O4­(OH)4­(O2CH)4­{(PNNNP)­RuCl­(CO)2}2­Cl2; 3, Zr6O4­(OH)4­(OAc)4{cis-/trans-(PNNNP)­RuCl2­(CO)}2; PNNNP = 2,6-(HNPAr2)2C5H3N; Ar = p-C6H4CO2). The structure and composition of the PNNNP-Ru pincer MOFs have been determined using synchrotron X-ray powder diffraction, solid- and solution-state NMR spectroscopy, IR spectroscopy, and elemental analysis. Reaction of 2 with KOtBu results in deprotonation of an NH group of the PNNNP-RuCl­(CO)2 linkers. Subsequent treatment with Me3NO removes a Ru-coordinated CO ligand, generating 2-b, which proved to be a recyclable catalyst for the hydrosilylation of aryl aldehydes with Et3SiH. A similar postsynthetic treatment of 1 and 3 does not generate active catalysts, highlighting the importance of precatalyst design and activation. A homogeneous analogue of 2-b also showed inferior catalytic performance, demonstrating the benefit of catalyst immobilization.

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