Crystal and molecular structure of the tetra-n-butylammonium salt of the cluster anion iodopentadecacarbonylhexarhodate

The structure of tetra-n-butylammonium iodopentadecacarbonylhexarhodate [N(C4H9)4][Rh6(CO)15l] has been determined from three-dimensional X-ray data collected by counter methods. The crystals are monoclinic with a= 14·93(2), b= 20·02(3), c= 15·50(2)A, β= 111·0(1)°, space group P21/n, and Z= 4. The structure determination, based on 1650 independent reflections, has been refined to R= 0·041. The crystal contains cluster anions [Rh6(CO)15l]– closely related to Rh6(CO)16. The mean edge of the metal octahedron is 2·746 A long. Each of four carbonyl groups bridges three metal atoms on alternate faces of the octahedron and the remaining carbonyl groups and the iodine atom behave as unidentate ligands. The Rh–l distance is 2·709(6)A. The idealized symmetry of the anion is Cs.