Synthesis and Physical Properties of Pentamethylmanganocene, (C5Me5)Mn(C5H5), and the Inclusion Compounds [(C5Me5)2Yb]2[(C5H5)2M] (Where M = V, Cr, Fe, Co)

The inclusion complexes of composition (Cp*2Yb)2(Cp2M) (M = V, Cr, Fe, and Co; Cp* = η5-C5Me5; Cp = η5-C5H5) are isolated in the solid state. The crystal structure of one of them, M = Co, shows that the Cp2Co metallocene is sandwiched between two Cp*2Yb metallocenes with two long Yb···C bond distances of 2.914(6) Å, one from each of the Cp rings of Cp2Co. When M = Mn and Ni are used, the ring exchange products, Cp*MCp, are isolated along with Cp*YbCp, a hydrocarbon-insoluble green solid isolated as the thf adduct. This Cp for Cp* exchange reaction is the only currently available synthesis for the low-spin pentamethylmanganocene and the pentamethylytterbocene. The crystal structures and magnetic and related physical properties of Cp*MCp, M = Mn, Co, and Ni (Organometallics 1985, 4, 1680), are reported and analyzed. The origin of the different relative rates of Cp* for Cp ring exchange is traced to the kinetic lability resulting from the (e1g*)2 electronic structure of Cp2M, M = Mn and Ni.