Guanidine-centred reactivity of CNN Pd(II) pincer complexes including carboxylate-assisted N–H activation and –CH<subscript>2</subscript>– → –C(O)– oxygenation.
In: New Journal of Chemistry, Jg. 48 (2024-04-07), Heft 13, S. 5710-5720
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Zugriff:
Transition metal complexes of N-substituted guanidinates are widely studied due to their intriguing structures, reactivities, and bonding as homogeneous catalysts and precursors for chemical vapor deposition. In this manuscript, we have isolated a family of pincer complexes, [Pd{κ 3 (CNN)(OC(O)R′)}] (CNN = N-picolyl-N′,N′′-diarylguanidinate(1−); aryl = 2-RC 6 H 4 ; R = Me and CF 3 ; R′ = CF 3 , Me and t Bu; A) and studied their reactions with XylN≡C (Xyl = 2,6-Me 2 C 6 H 3 ) and PPh 3 (Ls′) with the objective of understanding the substituent effects of the pincer complexes upon the nature of the products. In this endeavour, we were able to isolate the respective cationic [Pd{κ 3 (CNN)(L)}][OC(O)R′] (B) and neutral [Pd{κ 3 (CNN)(C≡NXyl)}] (CNN = N-picolinoyl-N′,N′′-diarylguanidinate(2−); D) complexes with the latter complexes formed from the former through carboxylate-assisted N–H activation followed by –CH 2 – → –C(O)– oxygenation of the 2-picolyl unit in the guanidinate(1−) ligand, which is induced by atm. O 2 . An elusive intermediate, [Pd{κ 3 (CNN)(C≡NXyl)}] (CNN = N-picolyl-N′,N′′-di(2-tolyl)guanidinate(2−); C) formed during B → D transformation was successfully isolated. The new complexes were fully characterised and the molecular structures of nine complexes were determined by X-ray crystallography. Various intermediates formed during the oxygenation were mapped out using the model complexes through DFT calculations. The solution behaviour of A was studied by multinuclear NMR and their utility as catalysts in Suzuki–Miyaura coupling reactions and base-free cycloisomerization of 4-pentynoic acid was briefly explored. The carboxylate-assisted N–H activation and oxygenation of the Pd(II) bound guanidinate(1−/2−) ligands reported herein represent the redox active behaviour of the ligand towards atm. O 2 for the first time. [ABSTRACT FROM AUTHOR]
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Titel: |
Guanidine-centred reactivity of CNN Pd(II) pincer complexes including carboxylate-assisted N–H activation and –CH<subscript>2</subscript>– → –C(O)– oxygenation.
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Autor/in / Beteiligte Person: | Sinha, Nitish Kumar ; Khan, Hilal Ahmad ; Sivasankar, Chinnappan ; Thirupathi, Natesan |
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Zeitschrift: | New Journal of Chemistry, Jg. 48 (2024-04-07), Heft 13, S. 5710-5720 |
Veröffentlichung: | 2024 |
Medientyp: | academicJournal |
ISSN: | 1144-0546 (print) |
DOI: | 10.1039/d3nj05516g |
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