An Effective Route to Cycloruthenated N-Ligands under Mild Conditions

Abstract

Cycloruthenated complexes of the type [(η6-C6H6)Ru(C∧N)CH3CN]+PF6- (C∧N = C6H4-2-CH2NMe2, (R)-(+)-C6H4-2-CH(Me)NMe2, C6H2-3,4-(OCH3)2-2-CH2NMe2) are readily obtained by the intramolecular C−H activation of N,N-dimethylbenzylamine derivatives with [(η6-C6H6)RuCl2]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(CH3CN)4]+PF6- (C∧N = C6H4-2-C5H4N, C6H4-2-(CH2)-C5H4N) were obtained in 40 and 24% isolated yields, respectively.