Me2Si(eta(5)-C5H4)(2)-bridged dinuclear ruthenium complexes: X-ray crystalstructures of [Ru-2{mu-(eta(5)-C5H4)(2)SiMe2}(Cl)(2)(CO)(4)] and [Ru-2{mu-(eta 5-C5H4)(2)SiMe2}(mu-Br)(CO)(4)][BF4]

The treatment of the binuclear tetracarbonyl complex [Ru-2{mu-(eta(5)-C5H4) (2)SiMe2}(mu-CO)(2)(CO)(2)] (1) with HBF4 in dichloromethane leads to the e lectrophilic addition of one proton to yield the bridging hydride complex [ Ru-2{mu-(eta(5)-C5H4)(2)SiMe2}(mu-H)(CO)(4)][BF4] (2). Complex 1 also react s with Li[BHEt3] to afford the bridging methylene complex [Ru-2{mu-(eta(5)- C5H4)(2)SiMe2}-(mu-CH2)(mu-CO)(CO)(2)] (3). Binuclear complexes [Ru-2{mu-(e ta(5)-C5H4)(2)SiMe2}(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-chlor osuccinimide (X = Cl) and X-2 (X = Br, I) in CH2Cl2. The structure of compl ex 4a which has been determined by X-ray crystallography shows a three-legg ed piano-stool geometry around each ruthenium atom linked by the bridging M e2Si(eta(5)-C5H4)(2) group. The cyclopentadienyl rings which are coordinate d in a eta(5) fashion are rotated in opposite directions around the Si-C(br idgehead) bond, leading to the trans arrangement of the metal fragments and giving rise to a long ruthenium-ruthenium distance (6.120(6) Angstrom). Co mplex 4c has been used as a precursor in a series of halide and carbonyl su bstitution reactions. The reaction of 4c with the cuprate derivative Li[CuM e2] in THF leads to the exchange of both iodide anions to give the dimethyl complex [Ru-2(mu-(eta(5)-C5H4)(2)SiMe2}(CH3)(2)(CO)(4)] (5). The treatment of complex 4c with AgBF4 in refluxing acetonitrile leads to halide abstrac tion to afford the cationic complex [Ru-2{mu-(eta(5)-C5H4)(2)SiMe2}(CO)(4)( NCMe)(2)][BF4](2) (9) The analogous reaction of complexes 4a-c with AgBF4 i n CH2Cl2 or acetone at room temperature gives the cationic double-bridged d erivatives [Ru-2{mu-(eta(5)-C5H4)(2)SiMe2)}(mu-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 yiel d the monocarbonyl complex [Ru-2{mu-(eta(5)-C5H4)(2)SiMe2}-(I)(2)(CO)(2)(PC y3)(2)] (6c). Analogous isocyanide carbonyl substituted complexes [Ru-2{mu- (eta(5)-C5H4)(2)-SiMe2}(I)(2)(CNR)(x)(CO)(4-x)] (R = CH2Ph, x = 1 (7a), x = 2 (7b), x = 3 (7c), x = 4 (7d); R = Cy, 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.