Synthesis and diastereoselective ligand substitution reaction of a mono(sulfido)-bridged Ir–Mo heterodinuclear complex

The reaction of the mono(hydrosulfido) iridium complex [Cp∗IrH(SH)(PPh3)] (1, Cp∗ = η5-C5Me5) with [Cp∗MCl2(NO)] (2, M = Mo, W) afforded the mono(sulfido)-bridged Ir–Mo and Ir–W heterodinuclear complexes [Cp∗IrH(PPh3)(μ-S)MCl(NO)Cp∗] (3a and 3a′, M = Mo; 3b and 3b′, M = W) as a 2:1 mixture of diastereomers. Abstraction of the hydrido ligand in both 3a and 3a′ with [Ph3C][BF4] in CH2Cl2–MeCN underwent stereoselectively to give the RIr,RMo/SIr,SMo pair of the cationic acetonitrile complex [Cp∗Ir(NCMe)(PPh3)(μ-S)MoCl(NO)Cp∗][BF4] (4). The stereochemical course for the formation of 4 from the major isomer 3a was confirmed to be inversion at the iridium center by X-ray crystallographic studies. Ligand substitution experiment of 4 with CD3CN revealed that the stereochemistry of 4 is controlled thermodynamically.