An Effective Route to Cycloruthenated N-Ligands under Mild Conditions

Cycloruthenated complexes of the type (η 6 -C 6 H 6 )Ru(C∧N)CH 3 CN + PF 6 - (C∧N = C 6 H 4 -2-CH 2 NMe 2, ( R )-(+)-C 6 H 4 -2-CH(Me)NMe 2, C 6 H 2 -3,4-(OCH 3 ) 2 -2-CH 2 NMe 2 ) are readily obtained by the intramolecular C−H activation of N, N -dimethylbenzylamine derivatives with (η 6 -C 6 H 6 )RuCl 2 2 in up to 53% isolated yields. Under similar conditions, 8-methylquinoline also led to a cycloruthenated complex, though in lower yield (12%) and after a longer reaction time. Reaction with the optically active ( R )-(+)- N, N -dimethyl-1-phenylethylamine led to a 48% diastereomeric excess in the cycloruthenated product. Under the same conditions, and after 14 and 65 h of reaction time, respectively, 2-phenyl- and 2-benzylpyridine are cyclometalated, leading to the formation of complexes in which the benzene ligand has been substituted by three acetonitriles: (C∧N)Ru(CH 3 CN) 4 + PF 6 - (C∧N = C 6 H 4 -2-C 5 H 4 N, C 6 H 4 -2-(CH 2 )-C 5 H 4 N) were obtained in 40 and 24% isolated yields, respectively.