High nuclearity iridium clusters derived from the transformation of [Ir-4(CO)(11)(PPh2Cl)] on silica gel and the thermolysis of [HIr4(CO)(10)(mu-PPh2)]; synthesis and characterization of [Ir-6(mu-CO)(CO)(12)(mu-PPh2)(2)], [Ir-7(mu-CO)(CO)(13)(mu-PPh2

摘要

The monosubstituted compound [Ir-4(CO)(11)(PPh2Cl)] reacts on silica gel to give [HIr4(CO)(10)(mu-PPh2)] and the novel compounds [Ir-4(CO)(11)(PPh2OH)] and [Ir-6(mu-CO)(CO)(12)(mu-PPh2)(2)] whose relative yields (up to 75, 10 and 40%, respectively) depend on cluster loading and the polarity of the eluent. The molecular structure of the hexanuclear compound was established by an X-ray analysis and consists of an octahedron of iridium atoms with two diphenylphosphido groups symmetrically bridging two non consecutive edges. Thermolysis of [HIr4(CO)(10)(mu-PPh2)] in THF results in the formation of the same hexanuclear compound (up to 40%), together with [Ir-7(mu-CO)(CO)(13)(mu-PPh2)(mu 3-PPhC6H4)] (10%) and [Ir-s(mu-CO)(2)(CO)(14)(eta(1)-Ph)(mu-PPh2)(mu(4)-PPh)] (40%), depending on the reaction conditions; their molecular structures were determined by X-ray analyses. The heptanuclear compound exhibits a capped octahedral metal frame with a diphenylphosphido and a phenyl orthometallated phosphido ligands bridging two opposite equatorial edges of the octahedron; the octanuclear cluster exhibits a fused octahedron-square based pyramid metal atom arrangement with the phosphinedene ligand bonded to the square face of the pyramid and the phosphido group to one of the edges of the octahedron. Possible mechanisms for the formation of these high nuclearity clusters are discussed. (C) 1998 Elsevier Science Ltd. All rights reserved. [References: 40]