Rollover-Assisted C(sp2)C(sp3) Bond Formation

• Published in: Chemistry : a European journal Vol. 20; no. 18; pp. 5501 - 5510
• Main Authors: Zucca, Antonio, Maidich, Luca, Canu, Laura, Petretto, Giacomo L., Stoccoro, Sergio, Cinellu, Maria Agostina, Clarkson, Guy J., Rourke, Jonathan P.
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 25.04.2014; WILEY‐VCH Verlag; Wiley Subscription Services, Inc
• Subjects: Activation; bond coupling; Bonding; Chemistry; Heterocyclic compounds; Ligands; NMR spectroscopy; platinum; reductive elimination; Rock; Rollover; rollover cyclometalation; Sequences; Series (mathematics); platinum; reductive elimination; bond coupling; NMR spectroscopy; rollover cyclometalation
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201304257

Rollover cyclometalation involves bidentate heterocyclic donors, unusually acting as cyclometalated ligands. The resulting products, possessing a free donor atom, react differently from the classical cyclometalated complexes. Taking advantage of a “rollover”/“retro‐rollover” reaction sequence, a succession of oxidative addition and reductive elimination in a series of platinum(II) complexes [Pt(N,C)(Me)(PR3)] resulted in a rare C(sp2)C(sp3) bond formation to give the bidentate nitrogen ligands 3‐methyl‐2,2′‐bipyridine, 3,6‐dimethyl‐2,2′‐bipyridine, and 3‐methyl‐2‐(2′‐pyridyl)‐quinoline, which were isolated and characterized. The nature of the phosphane PR3 is essential to the outcome of the reaction. This route constitutes a new method for the activation and functionalization of CH bond in the C(3) position of bidentate heterocyclic compounds, a position usually difficult to functionalize. Rock and rollover! Rare cases of C(sp2)C(sp3) bond formation from PtIV cyclometalated complexes are described, through a succession of oxidative addition and reductive elimination reactions, taking advantage of a “rollover”/“retro‐rollover” sequence (see scheme).