Metal containing polyhedral oligomeric silsesquioxanes (POSS) have been used to model a variety of industrial catalysts consisting of silica (SiO2) supported metals. We have successfully synthesized and fully characterized four different iron (III) chloro-POSS compounds. (isobutyl, cyclopentyl, phenyl and ethyl derivatives, see Figure) The isobutyl derivative has been shown to facilitate the aerobic oxidation of tetrahydrofuran (C4H8O) to γ-butyrolactone (C4H6O2). In this paper, we will demonstrate the aerobic conversion of tetrahydrofuran to g-butyrolactone using the cyclopentyl-, phenyl-, and ethyl- iron (III) chloro-POSS derivatives. We will compare the effect of varied hydrocarbon substituents (isobutyl, cyclopentyl, phenyl and ethyl) on the iron (III) chloro-POSS derivatives and their influence on the yield of g-butyrolactone from the aerobic oxidation of tetrahydrofuran.