Cp-functionalized building blocks for polymetallacarborane assemblies. Multinuclear cobaltacarborane complexes on fulvalene and 1,3,5-tris(cyclopentadienyl)benzene scaffolds

摘要

The introduction of organic and inorganic substituents onto eta(5)-C5H5 (Cp) ligands in the small cobaltacarboranes CpCo(Et2C2B4H4) and nido-CpCo(Et2C2B3H5) and their derivatives has been explored, together with metal-promoted C-C coupling to generate polycluster species featuring Cp-Cp and Cp-benzene linkages. This approach supplements alternative synthetic strategies based on functionalization of boron vertexes via metal-promoted B-C coupling, as described in a series of recent papers from our group,(4,5) and affords complexes of novel architecture as well as improved routes to previously known types. Among the new compounds are triple-sandwich trinuclear and hexanuclear benzene-centered complexes in which three cobaltacarborane units are anchored to a central 1,3,5-(eta(5)-C5H4)(3)C6H3 hydrocarbon scaffold. The fulvalene-bridged dinuclear species [(2,3-Et2C2B4H4)Co(eta(5)-C5H4)](2) (7) and (closo-2,3-Et2C2B4H4)(nido-2,3-Et2C2B3H5)Co-2(eta(5)-C5H4)(2) (8), previously obtained by Davis et al.(7) from the fulvalenide dianion, were prepared in this work directly from the CpCo-(Et2C2B4H4) and nido-CpCo(Et2C2B3H5) monomers. Apically substituted B(7)-trimethylsilylethynyl derivatives of 7 were also synthesized. New compounds were characterized via multinuclear NMR, IR, UV-visible (in some cases), and mass spectroscopy. [References: 29]