A Re(CO)5 Fragment Bonded to a Polyhedral Oligomeric Hydroxysilsesquioxane as a Model which Gives Further Evidence to the Existence of an Unexpected Re(CO)5 Surface Species

Reaction of Re(CO)5O3SCF3 with (c-C6H11)7Si8O12O-Li+ at 273 K under a CO atmosphere affords the [Re(CO)5OR] (R = (c-C6H11)7Si8O12) derivative (1). 1 is the first example of a rhenium pentacarbonyl bearing an OR ligand (R = alkyl, aryl, or silyl) stable enough to be characterized, and it represents also the first molecular model of the surface [Re(CO)5OSi] species formed by reductive carbonylation of silica-supported [Re(CO)3OH]4. At room temperature, 1 loses one carbonyl ligand and dimerizes to afford {Re(CO)4[(-O)O12Si8(c-C6H11)7]}2 (2), which has been characterized by X-ray diffraction and is the first reported example of a rhenium tetracarbonyl -oxo-bridged dimer of the type [Re(CO)4(-OR)]2.