Five- and Seven-Membered Metallacycles in [C,N,N′] and [C,N] Cycloplatinated Compounds

The reactions of cis-[Pt(4-C6H4Me)2(μ-SEt2)]2 with ligands ArCHNCH2CH2NMe2 (Ar = 4-ClC6H4 (1a); 2-BrC6H4 (1b); 2,6-Cl2C6H3 (1c); C6F5 (1d)) and ArCHNCH2(4-ClC6H4) (Ar = 4-ClC6H4 (1e); 2-BrC6H4 (1f); 2,6-Cl2C6H3 (1g); C6F5 (1h)) were studied. Several types of compounds were formed including (i) [N,N′] coordination compounds (2a, 2c, 2d), (ii) [C,N,N′] platinum(IV) (3b, 3c), [C,N,N′] platinum(II) (4a), and [C,N] platinum(II) (4e) cyclometalated compounds with a five-membered metallacycle, and (iii) [C,N,N′] platinum(II) (5c) and [C,N] platinum(II) (5f, 5g) cyclometalated compounds with a seven-membered metallacycle. The reactions of the obtained cyclometalated compounds with triphenylphosphine were studied, and the new compounds were fully characterized including structure determinations for 4a, 5c, 5g, and the phosphine derivative 7 g′. The ease of formation of seven-membered metallacycles is discussed on the basis of the structure of the ligand (terdentate versus bidentate) and the C−X bond to be activated.