Reactions of [RuCl₂(η⁶-arene)]₂ (arene = benzene, p-cymene) with nido-[7-R-10-L-7,8-C₂B₉H₉]^– in THF at room temperature for 3 d give the (arene)ruthenacarborane complexes closo-[3-Ru(η⁶-arene)-1-R-8-L-1,2-C₂B₉H₉]⁺ {arene = benzene, R = H [L = Me₂S (1a), THT (1b), EtPhS (1c)], R = Me [L = Me₂S (2a)]; arene = p-cymene, R = H [L = Me₂S (3a)]} and mercaptan closo-[3-Ru(η⁶-arene)-1-R-8-HS-1,2-C₂B₉H₉] [arene = benzene, R = H (4), Me (5); arene = p-cymene, R = H (6)] in yields of 20–40 % and 22–29 %, respectively. The asymmetric ligand nido-[9-Me₂S-7,8-C₂B₉H₁₀]^– leads to the thioether complex closo-[3-Ru(η⁶-benzene)-7-MeS-1,2-C₂B₉H₁₀] (8) in 34 % yield under the same reaction conditions. The crystal structure of 1a is described and compared with those of 4 and 8. The fully assigned ¹¹B NMR spectroscopic data for a whole series of ruthenacarboranes having B-substituted sulfonium, thioether and mercaptan groups are presented. These data show a relation between antipodal cluster atom distances (antipodal distance) and antipodal effect (AE) in the crystal structures of these complexes and for other families of heteroboranes such as closo-[EB₁₁H₁₁] and closo-[EB₉H₉]. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

The [Cp′₃U] metallocenes contain substituted cyclopentadienyl ligands and U^III with f³ electron configuration. They are good π donors and bind π-accepting ligands (L) such as carbon monoxide and isocyanides to form the corresponding adducts [Cp′₃U(L)] (see scheme). The π-donating capability of the [Cp′₃U] fragments appears to be readily modulated by the substituents on the cyclopentadienyl ligand.