(1,2-[ETA(5)-(C(5)ME(5))IR]2B5H5) - ISOLATION AND STRUCTURAL CHARACTERIZATION OF A CLOSO-POLYHEDRAL METALLABORANE CLUSTER WITH A CAPPING BHGROUP

The synthesis and characterization of the novel pileo-cluster [(eta(5) -C(5)Me(5))(2)Ir2B5H5], 1, are reported. Compound 1 is formed as yello w crystals in very low yield from the reaction between [(eta(5)-C(5)Me (5))IrCl2]2 and Na-2[B5H9] in tetrahydrofuran. Irt is characterized by H-1 and B-11 NMR spectra, elemental analysis, a mass spectrum, and a crystal structure determination, The structure of 1 is that of an octa hedral cluster containing four BH groups and two adjacent [(eta(5)-C(5 )Me(5))Ir] groups. A fifth BH group caps a B-Ir-Ir trianglular face. T he pileo-cluster, 1, is related to the known system [(eta(5)-C(5)Me(5) )(2)Co2B5H5] for which a similar structure is proposed and [(eta(5)-C( 5)Me(5))Co)(3)B4H4] the Known structure of which also indicates the pr esence of a capping BH group, this one involving a [(eta(5)-C(5)Me(5)) Co](3) face.