Synthesis, characterization and crystal structures of osmium–rhodium mixed-metal clusters containing pentamethylcyclopentadienyl ligand: [Os3Rh(μ-CO)2(CO)9(η5-Cp*)], [Os3Rh2(μ-H)(μ-CO)2(CO)8(η5-Cp*)(μ2-η5,η1-CH2C5Me4)] and [Os3Rh(μ3-H)(μ-Cl)(μ-CO)(CO)9(η5-Cp*)]

Abstract

Treatment of the anionic triosmium cluster [N(PPh3)2][Os3(μ-H)(CO)11] with one equivalent of [RhCp*(MeCN)3][{PF6}2] [Cp*=pentamethylcyclopentadiene] yielded three Cp*-containing clusters including [Os3Rh(μ-H)2(μ-CO)(CO)9(η5-Cp*)] 1, [Os3Rh(μ-CO)2(CO)9(η5-Cp*)] 2 and [Os3Rh2(μ-H)(μ-CO)2(CO)8(η5-Cp*)(μ2-η5,η1-CH2C5Me4)] 3. Solid state vacuum pyrolysis of 2 gave 1 in moderate yield via the replacement of a bridging carbonyl by two bridging hydrides. The coupling reaction of [N(PPh3)2][Os3(μ-H)(CO)11] with the monocationic complex, [RhCp*(dppe)Cl][PF6] [dppe=bis(diphenylphosphino)ethane] afforded the tetranuclear cluster [Os3Rh(μ3-H)(μ-Cl)(μ-CO)(CO)9(η5-Cp*)] 4 in a moderate yield. Clusters 2–4 have been fully characterized by both spectroscopic and crystallographic methods. The X-ray structure analysis shows that 3 comprises an edge-bridging tetrahedron in which one of the pentamethylcyclopentadienyl units adopts a novel μ2-η5,η1-bonding mode across a Os–Rh bond. Cluster 4 is a tetranuclear osmium–rhodium mixed-metal cluster containing a chloride, bridging across the wing-tips of the butterfly core.