Synthesis, characterization and crystal structures of [Ir9H(CO)19]4- and [Ir10(CO)21]2-

The base-induced condensation of [Ir4(CO)12] at room temperature has yielded [Ir9(CO)20]3- and [Ir9H(CO)19]4-, which both reveal a face-sharing bioctahedral metallic framework; oxidation of [Ir9(CO)20]3- produced [Ir10(CO)21]2-, after addition of a butterfly-capping iridium atom; these clusters have been compared with known compounds of ruthenium, rhodium and iridium, which together model the building-up process of the closed-shell trigonal-bipyramidal polyhedron; step-by-step growth shows irregularities in the number of valence electrons, since the larger clusters require more filled orbitals than predicted by the capping principle. © Copyright 1994 by the Royal Society of Chemistry.