Synthesis and properties of the dichloro[tetramethyl(trifluoromethyl)cyclopentadienyl]ruthenium dimer:: X-ray structure of [M2(η5-C5Me4CF3)2Cl2(μ-Cl)2] (M = Ru, Rh)

The reaction of RuCl3(H2O), with C5Me4CF3H in refluxing EtOH gives [Ru-2(mu(5)-C5Me4CF3)(2)Cl-2(mu-Cl)(2)] (2) in 44% yield. Dimer 2 is antiferromagnetic (-2J = 200 cm(-1)). The crystal structures of 2 (rhombohedral system, R (3) over bar space group, Z = 9, R = 0.0589) and [Rh-2(eta(5)-C5Me4CF3)2Cl2(mu-Cl)2] (3) (rhombohedral system, R (3) over bar space group, Z=9, R = 0.0641) were solved; both complexes have dimeric structures with a trans arrangement of the eta(5)-C5Me4CF3 rings. Comparison of the geometry of 2 and 3 with those of the corresponding eta(5)-C5Me5 complexes shows that lowering the ring symmetry causes significant distortion of the M-2(mu-Cl)(2) moiety. The analysis of the MCl3 fragment conformations in 2 and 3 and in the eta(5)-C5Me5 analogues shows that they are correlated with the M-M distances. The Cl atoms are displaced by Br on reaction of 2 with KBr in MeOH to give the diamagnetic dimer [Ru-2(eta(5)-Me4CF3)(2)Br-2(mu-Br)(2)] (4). Complex 2 reacts with O-2 in CH2Cl2 solution at ambient temperature to form a mixture of isomeric eta(6)-fulvene dimers [Ru-2(eta(6)-C5Me3CF3=CH2)(2)Cl-2(mu-Cl)(2)] (5). Reactions of 5 with CO and allyl chloride give Ru(eta(5)-C5Me3CF3CH2Cl)(CO)(2)Cl (6) and Ru(eta(5)-C5Me3CF3CH2Cl) (eta(3)-C3H5)Cl-2 (7) respectively. (C) 1998 Elsevier Science S.A. All rights reserved.