2,5-DIMETHYLTHIOPHENE COORDINATION TO 3 METAL CENTERS IN THE COMPLEXES (MU-4,S-MU-3-2,5-ME2T)(IRCP-ASTERISK) [M(CO)2CP]2 WHERE M = MO OR W

The 2,5-dimethylthiophene (2,5-Me2T) ligand in the isomers Cp*Ir(eta-4-2,5-Me2T) (1) and Cp*Ir(C,S-2,5-Me2T) (2) is activated to react with the dimers Cp(CO)2M = M(CO)2Cp[M = Mo (3), W (4)] to give complexes (5, 6) in which the thiophene is coordinated to three metals. Oxidation of 5 with Cp2Fe+ removes [GRAPHICS] the Mo dimer to give Cp*Ir(eta-5-2,5-Me2T)2+. Reaction of 5 with CO displaces the Mo as [CpMo(CO)3]2 to give Cp*Ir(CO)(C,S-2,5-Me2T) (7). Ultraviolet photolysis of 1 provides a convenient route to the ring-opened isomer 2. Despite the remarkable nature of the thiophene coordination in 5 and 6, its reactivity does not suggest new pathways that would lead to the hydrodesulfurization of thiophenes.