Me2Si(η5-C5H4)2-Bridged Dinuclear Ruthenium Complexes: X-ray Crystal Structures of [Ru2{μ-(η5-C5H4)2SiMe2}(Cl)2(CO)4] and [Ru2{μ-(η5-C5H4)2SiMe2}(μ-Br)(CO)4][BF4

Abstract

The treatment of the binuclear tetracarbonyl complex [Ru2{μ-(η5-C5H4)2SiMe2}(μ-CO)2(CO)2] (1) with HBF4 in dichloromethane leads to the electrophilic addition of one proton to yield the bridging hydride complex [Ru2{μ-(η5-C5H4)2SiMe2}(μ-H)(CO)4][BF4] (2). Complex 1 also reacts with Li[BHEt3] to afford the bridging methylene complex [Ru2{μ-(η5-C5H4)2SiMe2}(μ-CH2)(μ-CO)(CO)2] (3). Binuclear complexes [Ru2{μ-(η5-C5H4)2SiMe2}(X)2(CO)4] (X = Cl (4a), Br (4b), and I (4c)) have been synthesized in good yields from the reaction of complex 1 with N-chlorosuccinimide (X = Cl) and X2 (X = Br, I) in CH2Cl2. The structure of complex 4a which has been determined by X-ray crystallography shows a three-legged piano-stool geometry around each ruthenium atom linked by the bridging Me2Si(η5-C5H4)2 group. The cyclopentadienyl rings which are coordinated in a η5 fashion are rotated in opposite directions around the Si−C(bridgehead) bond, leading to the trans arrrangement of the metal fragments and giving rise to a long ruthenium−ruthenium distance (6.120(6) Å). Complex 4c has been used as a precursor in a series of halide and carbonyl substitution reactions. The reaction of 4c with the cuprate derivative Li[CuMe2] in THF leads to the exchange of both iodide anions to give the dimethyl complex [Ru2(μ-(η5-C5H4)2SiMe2}(CH3)2(CO)4] (5). The treatment of complex 4c with AgBF4 in refluxing acetonitrile leads to halide abstraction to afford the cationic complex [Ru2{μ-(η5-C5H4)2SiMe2}(CO)4(NCMe)2][BF4]2 (9). The analogous reaction of complexes 4a−c with AgBF4 in CH2Cl2 or acetone at room temperature gives the cationic double-bridged derivatives [Ru2{μ-(η5-C5H4)2SiMe2)}(μ-X)(CO)4][BF4] (10a−c). The X-ray crystal structure of 10b shows the two ruthenium moieties bridged by a halogen atom, forcing a cisoid arrangement in the molecule. Irradiation of a solution of 4c and PCy3 in THF leads to carbonyl substitutions to yield the monocarbonyl complex [Ru2{μ-(η5-C5H4)2SiMe2}(I)2(CO)2(PCy3)2] (6c). Analogous isocyanide carbonyl substituted complexes [Ru2{μ-(η5-C5H4)2SiMe2}(I)2(CNR)x(CO)4-x] (R = CH2Ph, x = 1 (7a), x = 2 (7b), x = 3 (7c), x = 4 (7d); R = Cy, x = 1 (8a), x = 2 (8b), x = 3 (8c), x = 4 (8d)) have been obtained by UV irradiation of 4c and the corresponding isocyanide in THF, depending on the ligand:complex ratio.