- [Show abstract] [Hide abstract] ABSTRACT: The reaction of the 16-electron (16e) half-sandwich complex CpCo(S2C2B10H10) (1; Cp = cyclopentadienyl) with ethynylferrocene (Fc–C≡CH) in CH2Cl2 at ambient temperature leads to (CHCFc)(S2C2B10H10) (2), where the alkyne is added to the o-carborane-1,2-dithiolate ligand at the two sulfur sites with the loss of the CpCo unit. However, in MeOH the reaction gives rise to an additional product, CpCo(S2C2B9H9)(CH2CFc)(CH2═CFc) (3), in which one alkyne has been reduced to an alkane containing a B–CH2 unit and the second alkyne is present as a terminal alkene at the second sulfur site. If silica and moisture are present, CpCo(S2C2B9H10)(CH═CFc)(CH2C(O)Fc) (4) could be generated, in which one alkyne is stereoselectively inserted into one Co–S bond and the second alkyne is present as an acetyl ferrocenyl group at the second sulfur site. Both 3 and 4 contain a nido-C2B9 unit. Moreover, in boiling toluene the reaction leads to CpCo(S2C2B10H10)(CHCFc) (5), where the cleavage of the weaker Co–C and C–S bonds and the formation of a stronger C–C bond has occurred. In comparison, the reaction of Cp*Co(S2C2B10H10) (1*; Cp* = pentamethylcyclopentadienyl) at ambient temperature gives rise to the alkyne 2-fold inserted product Cp*Co(S2C2B10H10)(FcCCHCHCFc) (6). If 6 is heated in boiling toluene, the unusual product (FcCSCHCHCFc)(SC2B10H10) (7) is obtained, where two alkynes are dimerized with the formation of two five-membered S-heterocycles and the loss of a Cp*Co unit. The five new compounds 3–7 were characterized by NMR (1H, 11B, 13C), mass spectroscopy, and X-ray structural analysis.
- [Show abstract] [Hide abstract] ABSTRACT: The reaction of the 16e half-sandwich complex Cp*Co(S2C2B10H10) (1) (Cp* = pentamethylcyclopentadienyl) with excess methyl acetylene monocarboxylate, HC≡C-CO2Me, affords the 18e complexes 2–6. Compound 2 bears a B-CH2 unit in which B-substitution occurs in the B(3)/B(6) position of the ortho-carborane cage. Complexes 3–6 are geometrical isomers, in which the alkyne is twofold inserted into one of the Co-S bonds in all the four possible ways. Treatment of 1 with excess 3-butyn-2-one or phenyl ethynyl ketone, HC≡C-C(O)R (R = Me, Ph), at ambient temperature leads to the 18e complexes 7–10, respectively, with two alkynes inserted into one of the Co-S bonds. All the new complexes were fully characterized by spectroscopic techniques and elemental analysis. The solid-state structures of 2, 3, 5, 7, 8, 9 and 10 were further characterized by X-ray structural analysis. Keywords ortho-carborane dithiolate-alkynone-cobalt complex-half-sandwich-crystal structure
- [Show abstract] [Hide abstract] ABSTRACT: Two new ruthenium(II) arene complexes, 2a (C(24)H(34)B(10)FeRuS(2)) and 2b (C(15)H(26)B(10)O(2)RuS(2)), bearing a carborane unit and other different functional groups were synthesized, and their cytostatic effects on cancerous cells were evaluated. Our observations illustrate that a structural change from a ferrocene unit to a carboxyl group could lead to high selectivity toward cancer cells and facilitate the efficient inhibition of the proliferation of target cells, indicating that the tuning of the overall properties of the ruthenium(II) arene complex by appropriate ligand tagging is critical to creating a selective antineoplastic agent.