Site-selective carbonyl substitution in the mixed-metal cluster anion [H2Ru3Ir(CO)(12)](-): synthesis and characterization of phosphine, phosphite, arsine and stibine derivatives

The reaction of the mixed-metal carbonyl cluster anion [H2Ru3Ir(CO)(12)](-) with PPh3, PMe3, P(OPh)(3), AsPh3 or SbPh3 leads to the mono-substituted d erivatives [H2Ru3Ir(CO)(11)L](-) (L = PPh3 1, L = PMe3 2, L = P(OPh)(3) 3, L = AsPh3 4, L = SbPh3 5). Protonation of the anions 1-5 gives the neutral trihydrido derivatives H3Ru3Ir(CO)(11)L (L = PPh3 6, L = PMe3 7, L = P(OPh) (3) 8, L = AsPh3 9, L = SbPh3 10). All new tetranuclear clusters invariably show a tetrahedral arrangement of the Ru3Ir skeleton, as predicted for 60 e systems. The ligand L is coordinated to one of the ruthenium atoms, excep t in the case of L = PMe3 where two substitution isomers are observed. Whil e the anionic isomers [H2Ru3Ir(CO)(11)(PMe3)](-) (2) could not be separated , the corresponding neutral isomers H3Ru3Ir(CO)(11)(PMe3) (7) could be reso lved by thin-layer chromatography. In isomer 7a, the phosphine ligand is co ordinated to one of the ruthenium atoms, whereas in isomer 7b the PMe3 liga nd is bonded to the iridium atom. The molecular structures of 1, 7b, 8 and 9 were confirmed by a single-crystal X-ray structure analysis. (C) 1999 Els evier Science S.A. All rights reserved.