Thermal Transformation of cis- and trans-[{Mo(CO)3H}2{μ-η5:η5-C5H3(SiMe2)2C5H3}] into [{Mo(CO)3}2{μ-η5:η5-C5H4(SiMe2SiMe2)- C5H4}](Mo−Mo) Promoted by Hydride Migration

When cis- or trans-[{Mo(CO)3H}2{μ-η5:η5-C5H3(SiMe2)2C5H3}] (1) is heated for 5 days to 90 °C in toluene or C6D6, the unexpected complex [{Mo(CO)3}2{μ-η5:η5-C5H4(SiMe2SiMe2)C5H4}] (2) is obtained, in which the hydride has migrated to the cyclopentadienyl group and the two silicon atoms have been coupled. The formation of 2 has been studied by labeling techniques.