This paper describes the reaction of hydroborate ions (B12H12 2-, B10H10 2-, and B11H14-) and π-arene-π cyclopentadienyliron cations, yielding 36 π-arene-π- cyclopentadienyliron hydroborates, which has been identified by elemental analysis and IR spectra, and some of which by ^1H NMR. DTA results indicate that: (1) with the same cation, the order of the thermal stabilities of the compounds is (ArFeC5H5)2B12H12> (ArFeC5H5)2B10H10>(ArFeC5H5)B11H14; (2) with the same anion, the order of the thermal stabilities of the compounds is effected by the substituted group in the arene.

Key words: THERMAL STABILITY, BENZENE P, CYCLOPENTADIENE P, IRON COMPLEX, ORGANO BORON COMPOUNDS, BORIC ACID P