SYNTHESIS AND REACTIVITY OF THE NEW UNSATURATED HETEROBIMETALLIC POLYHYDRIDE COMPLEX (CO)(PPH3)2HRE(MU-H)3RUH(PPH3)2

The reaction of [K][ReH6(PPh3)2] with RuHCl(CO)(PPh3)3 leads to the fo rmation of the 30-electron complex (CO)(PPh3)2HRe(mu-H)3RuH(PPh3)2 (1) in good yield. Its structure has been established by an X-ray structu re determination. Most of the bridging hydrides were located in a diff erence Fourier map. The position of the terminal hydrides has been cal culated using the program HYDEX. Crystallographic data for 1: monoclin ic C2h5-P2(1)/n, a = 21.938(6) angstrom, b = 13.046(2) angstrom, c = 4 4.804(10) angstrom; beta = 96.50(1)degrees, V = 12740 angstrom3, Z = 8 ; R = 0.053, R(w) = 0.068 for 4683 observations and 425 variable param eters. Compound 1 is inactive toward alkynes, but with ethylene the su bstitution of two hydride ligands and not the expected addition reacti on is observed, leading to (CO)(PPh3)2Re(mu-H)3Ru(C2H4)(PPh3)2 (2). Th e reaction is reversible under hydrogen at atmospheric pressure. With chloroform 1 gives selectively the 34-electron complex (CO)(PPh3)2Re(m u-Cl)2(mu-H)RuH(PPh3)2 (3). Compounds 1 and 3 react with HBF4.OEt2 to give [(CO)(PPh3)2Re(mu-X)2(mu-H)Ru(H2)(PPh3)2][BF4] (X = H (4); X = Cl (5)), the first examples of heterobimetallic complexes containing mol ecular hydrogen as a ligand. Contrary to 5, the molecular hydrogen lig and in 4 is labile and can be replaced by ligands L like acetone, acet onitrile, or ethylene, leading to [(CO)(PPh3)2Re(mu-H)3Ru(L)(PPh3)2][B F4] complexes.