Synthesis and reduction of trifluoromethyl-substituted arenecyclopentadienylruthenium sandwiches [Ru(η5-C5Me4CF3)(η6-C6R6)]+ (R = H, Me) and [Ru(η5-C5Me5)(η6-C6H5CF3)]+

Dimer [Ru-2(eta(5)-C5Me4CF3)(2)Cl-2(mu-Cl)(2)] (1) has been prepared by reaction of RuCl3 .(H2O)(3) with 1,2,3,4-tetramethyl-5-(trifluoromethyl)cyclopentadiene in ethanol under reflux. Cationic arenecyclopentadienyl complexes [Ru(eta(5)-C5Me4CF3)(eta(6)-arene)]+PF6- (2(+), arene =C6H6; 3(+) arene=C6Me6) and [Ru(eta(5)-C5Me5)(eta(6)-C6H5CF3)]+BF4- (4(+)) were obtained by refluxing [Ru-2(eta(5)- C5Me4CF3)(2)Cl-2(mu-Cl)(2)] (1) or [Ru-2(eta(5)-C5Me5)(2)Cl-2(mu-Cl)(2)] with corresponding arenes in alcohol. The redox properties of 2(+)-4(+) were studied by cyclic voltammetry (CV). All three complexes 2(+)-4(+) are reduced irreversibly in one-electron process. The values of reduction peak potentials for 2(+)-3(+) are less negative than those found for eta(5)-C5Me5 analogues. The reduction of 2(+) and 3(+) with sodium amalgam in tetrahydrofuran led to the formation of dimers [Ru-2(eta(5)-C5Me4CF3),(2)(mu-eta(5):eta(5)-C6H6C6H6)] (5) and [Ru-2(eta(5)-C5Me4CF3)(2)( mu-eta(5):eta(5)-C6Me6C6Me6)] (6) respectively. The reduction of 4(+) gave a non-identifiable mixture of neutral products. (C) 1998 Elsevier Science S.A.