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Manca L, Senzacqua G, Stoccoro S, Zucca A. Regioselective C(sp 2)-C(sp 3) Coupling Mediated by Classical and Rollover Cyclometalation. Molecules 2024; 29:707. [PMID: 38338451 PMCID: PMC10856536 DOI: 10.3390/molecules29030707] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2023] [Revised: 01/26/2024] [Accepted: 01/30/2024] [Indexed: 02/12/2024] Open
Abstract
By taking advantage of a sequence of oxidative addition/reductive elimination reactions, Pt(II) cyclometalated derivatives are able to promote a rare C(sp2)-C(sp3) bond coupling, resulting in the production of novel methyl-substituted pyridines and bipyridines. Starting from 6-phenyl-2,2'-bipyridine, the step-by-step full sequence of reactions has been followed, leading to the unprecedented 3-methyl-6-phenyl-2,2'-bipyridine, which was isolated and fully characterized. The synthesis involves the following steps: (1) rollover cyclometalation to give the starting complex [Pt(N^C)(DMSO)Me]; (2) the synthesis of a more electron-rich complex [Pt(N^C)(PPh3)Me] by the substitution of DMSO with triphenylphosphine; (3) oxidative addition with methyl iodide to give the Pt(IV) complex [Pt(N^C)(PPh3)(Me)2(I)]; (4) iodide abstraction with silver tetrafluoborate to give an unstable pentacoordinate intermediate, which rapidly evolves through a carbon-carbon reductive coupling, forming a new C(sp3)-C(sp2) bond; (5) finally, the extrusion and characterization of the newly formed 3-methyl-6-phenyl-2,2'-bipyridine. The reaction has been therefore extended to a well-known classical cyclometalating ligand, 2-phenylpyridine, demonstrating that the method is not restricted to rollover derivatives. Following the same step-by-step procedure, 2-phenylpyridine was converted to 2-o-tolyl-pyridine, displaying the potential application of the method to the larger family of classical cyclometalated complexes. The application of this protocol may be useful to convert an array of heterocyclic compounds to their methyl- or alkyl-substituted analogs.
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Affiliation(s)
- Lorenzo Manca
- Dipartimento di Scienze Chimiche, Fisiche, Matematiche e Naturali, Università degli Studi di Sassari, Via Vienna 2, 07100 Sassari, Italy; (L.M.); (G.S.); (S.S.)
| | - Giacomo Senzacqua
- Dipartimento di Scienze Chimiche, Fisiche, Matematiche e Naturali, Università degli Studi di Sassari, Via Vienna 2, 07100 Sassari, Italy; (L.M.); (G.S.); (S.S.)
- Consorzio Interuniversitario Reattività Chimica e Catalisi (CIRCC), Villa La Rocca, Via Celso Ulpiani, 27, 70126 Bari, Italy
| | - Sergio Stoccoro
- Dipartimento di Scienze Chimiche, Fisiche, Matematiche e Naturali, Università degli Studi di Sassari, Via Vienna 2, 07100 Sassari, Italy; (L.M.); (G.S.); (S.S.)
- Consorzio Interuniversitario Reattività Chimica e Catalisi (CIRCC), Villa La Rocca, Via Celso Ulpiani, 27, 70126 Bari, Italy
| | - Antonio Zucca
- Dipartimento di Scienze Chimiche, Fisiche, Matematiche e Naturali, Università degli Studi di Sassari, Via Vienna 2, 07100 Sassari, Italy; (L.M.); (G.S.); (S.S.)
- Consorzio Interuniversitario Reattività Chimica e Catalisi (CIRCC), Villa La Rocca, Via Celso Ulpiani, 27, 70126 Bari, Italy
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Jing J, Yu M, Pan L, Zhao Y, Xu G, Zhang HH, Li C, Zhang XP. Synthesis and Biological Activities of Luminescent 5,6-Membered Bis(Metallacyclic) Platinum(II) Complexes. Molecules 2023; 28:6369. [PMID: 37687198 PMCID: PMC10489632 DOI: 10.3390/molecules28176369] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2023] [Revised: 08/25/2023] [Accepted: 08/29/2023] [Indexed: 09/10/2023] Open
Abstract
Four couples of 5,6-membered bis(metallacyclic) Pt(II) complexes with acetylide and isocyanide auxiliary ligands have been prepared and characterized. The structures of (-)-2 and (-)-3 are confirmed by single-crystal X-ray diffraction, showing a distorted square-planar coordination environment around the Pt(II) nucleus. Both solutions and solid samples of all complexes are emissive at RT. Acetylide-coordinated Pt(II) complexes have a lower energy emission than those isocyanide-coordinated ones. The emission spectra of N^N'*C-coordinated Pt(II) derivatives show a lower energy emission maximum relative to N^C*N'-coordinated complexes with the same auxiliary ligand. Moreover, the difference between cyclometalated N^N'*C and N^C*N' ligands exerts a more remarkable effect on the emission than the auxiliary ligands acetylide and isocyanide. Cytotoxicity and cell imaging of luminescent 5,6-membered bis(metallacyclic) Pt(II) complexes have been evaluated.
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Affiliation(s)
| | | | | | | | | | | | | | - Xiao-Peng Zhang
- Key Laboratory of Water Pollution Treatment & Resource Reuse of Hainan Province, College of Chemistry and Chemical Engineering, Hainan Normal University, Haikou 571158, China; (J.J.); (M.Y.); (L.P.); (Y.Z.); (G.X.); (H.-H.Z.); (C.L.)
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