CARBORANE COMPLEXES OF RUTHENIUM - A CONVENIENT SYNTHESIS OF [RU(CO)(3)(ETA(5)-7,8-C2B9H11)] AND A STUDY OF REACTIONS OF THIS COMPLEX

Treatment of [Ru-3(CO)(12)] with nido-7,8-C2B9H13 in heptane at reflux temperatures affords [Ru(CO)(3)(eta(5)-7,8-C2B9H11)] (1) in high yield. Heating thf (tetrahydrofuran) solutions of the latter with [NEt(4)]I gives [NEt(4)][RuI(CO)(2)(eta(5)-7,8-C2B9H11)] (2a) which with AgBF4 in thf yields the neutral complex [Ru(CO)(2)(thf)(eta(5)-7,8-C2B9H11)] (3). The latter reacts with molecular hydrogen to give, after addition of [NEt(4)][BF4], the diruthenium species [NEt(4)][Ru-2(mu-H)(CO)(4)(eta(5)-7,8-C2B9H11)(2)] (4a). The [K(18-crown-6)1 salt (4b) of the anionic diruthenium complex is formed on protonation (HBF4 . Et(2)O) of [K(18-crown-G)][RuH/CO)(2)(eta(5)-7,8-C(2)B9H(11))] in CH2Cl2. The structure of 4a was established by X-ray crystallography. Crystals are monoclinic, space group P2(1)/c (No. 14), with a 11.205(2) Angstrom, b = 20.736(2) Angstrom, c 13.769(2) Angstrom, beta = 96.69(2)degrees, and Z = 4. The Ru-Ru bond [3.189(6) Angstrom] is bridged by the hydride ligand. The nido-7,8-C2B9H11 cages are transoid with respect to each other as are the two pairs of terminal CO groups on each ruthenium. The reaction between [K(18-crown-6)][RuH(CO)(2)(eta(5)-7,8-C2B9H11)] and [AuCl(PPh(3))] in thf in the presence of either AgBF4 or TIPF6 unexpectedly gives [Au(PPh(3))(2)][RuCl(CO)(2)(eta(5)-7,8-C2B9H11)] (2b) the structure of which was determined by X-ray crystallography. Crystals are triclinic, space group Pi (No. 2), with a = 11.167(2) Angstrom, b = 11.861(2) Angstrom, c = 17.103(3) Angstrom, alpha = 99.50(2)degrees, beta = 105.01(2)degrees, gamma = 95.58(2)degrees, and Z = 2. The anion in 2b has a piano stool configuration with ruthenium being coordinated on one side by the nido-C2B9H11 cage in the usual pentahapto manner and on the other by the two CO groups and the Cl atom [Ru-Cl = 2.452(1) Angstrom]. The salt 4b is deprotonated with NaH in thf yielding [K(18-crown-6)](2)[Ru-2(mu-CO)(2)(CO)(2)(eta(5)-7,8-C2B9H11)(2)] (5). An X-ray crystallographic study revealed that crystals are monoclinic, space group P2(1)/c (No. 14), with 12.746(1) Angstrom, b = 18.116(4) Angstrom, c = 12.440(2) Angstrom, beta = 109.58(1)degrees, and Z = 2. The Ru-Ru separation in the dianion is 2.793(1) Angstrom. The metal atoms and the two terminal CO ligands lie in a mirror plane and the two eta(5)-7,8-C2B9H11 groups are transoid on opposite sides of the plane, while the two mirror-related bridging CO groups lie on the crystallographic 2-fold axis. The reaction between [K(18-crown-G)1[RuH(CO)(2)(eta(5)-7,8-C2B9H11)] and [PtR(Cl)(PEt(3))(2)] in thf in the presence of TlPF6 yields [RuPt(mu-H)(mu-sigma:eta(5)-7,8-C2B9H10)(CO)(2)(PEt(3))(2)] (6), the structure of which was determined by X-ray crystallography. Crystals are monoclinic, space group P2(1)/c (No. 14), with a 18. 774(4) Angstrom, b = 12.094(2) Angstrom, c = 13.429(3) Angstrom, beta = 110.78(2)degrees, and Z = 4. The Ru-Pt bond [2.802(1) Angstrom] is spanned on one side by the hydride ligand and on the other by an exopolyhedral B-Pt linkage [2.069(7) Angstrom] involving a cage boron atom which is in the a site with respect to the two carbon atoms in the [GRAPHICS] ring ligating the ruthenium. The latter carries two terminal CO ligands, and the platinum atom is in an essential planar environment defined by the Ru, B-alpha, and the two P atoms. The new complexes have been characterized by NMR spectroscopy in addition to the X-ray diffraction