ENCAPSULATED ALKALINE-EARTH METALLOCENES .4. THERMAL-INSTABILITY IN TETRAPHENYLCYCLOPENTADIENYL BARIUM COMPLEXES

Reaction of two equivalents of C(5)Ph(4)H(2) With Ba[N(SiMe(3))(2)](2) (THF)(2) in THF or toluene-produces the solvated octaphenylbarocene (C (5)Ph(4)H)(2)Ba(THF) in quantitative yield. The air-sensitive metalloc ene displays a surprising lack of thermal stability, and decomposes in the solid state at room temperature over a period of two weeks or upo n attempted vacuum sublimation at 110-120 degrees C (10(-6) torr). Rea ction of C(5)Ph(4)H(2) with Ba[N(SiMe(3))(2)](2)(THF)(2) in a 1 : 1 mo lar ratio in THF or toluene produces a yellow solid that is a mixture of the metallocene with the mono(ring) compound (C(5)Ph(4)H)BaN(SiMe(3 ))(2)(THF)(n). Attempts to synthesize a barocene containing the pentap benylcyclopentadienyl ligand were not successful.