Metallocene Coordination to Neutral Alkaline Earth Metal Complexes

The geometrically constrained, Lewis acidic magnesium diamide complex, [Mg(^EtNON^TCHP)] (^EtNON^TCHP = 4,5-bis(2,4,6-tricyclohexylanilido)-2,7-diethyl-9,9-dimethyl-xanthene), forms complexes with a series of metallocenes, [Mg(^EtNON^TCHP)(η²-Cp₂M)] (M = Mn, Fe, Co, or Ni), in which one cyclopentadienyl ring of the metallocene is η²-coordinated to the magnesium center. Treating the heavier group 2 metal amide complexes, [M(^EtNON^TCHP){N(H)(SiMe₃)₂}] (M = Ca, Sr or Ba) with ferrocene yields complexes [M(^EtNON^TCHP)(η⁵-Cp₂Fe)] in which one cyclopentadienyl ring of ferrocene is η⁵-coordinated to the group 2 metal center. Computational studies on the metallocene complexes reveal that the metallocene-group 2 metal interactions are largely electrostatic in nature.