Organometallic cation-exchanged phyllosilicates - Fe-57 Mossbauer spectroscopic study of organoiron complexes on a low-iron montmorillonite

Variable-temperature Fe-57 Mossbauer spectroscopy, thermogravimetry and powder X-ray diffraction have been used to study the cations tricarbonyl(eta(5)-2,4-dimethylcyclohexadienyl)iron(1+) and tricarbonyl(eta(5)-2-methoxycyclohexadienyl)iron(1+) as both the hexafluorophosphate salts (A1 and A2, respectively) and when cation-exchanged onto the interlamellar sites of Westone-L (W-L), a low-iron montmorillonite (denoted A1-W-L and A2-W-L, respectively). A combination of thermogravimetry, total carbon analysis and X-ray fluorescence analysis for iron indicated that 40% of the available exchange sites on W-L were occupied by the cyclohexadienyl cations. The isomer shift, delta, and quadrupole splitting, Delta, of both A1 (delta=0.02 mm s(-1); Delta=1.56 mm s(-1)) and A2 (delta=0,02 mm s(-1); Delta=1.47 mm s(-1)) were unaffected by incorporation of the cations into the interlamellar environment. The hexafluorophosphate salts, A1 and A2, exhibited similar Debye temperatures, theta(D), and recoilless fractions, f, of 160+/-2K and 0.61, respectively, indicating that both iron moities enjoyed the same amount of freedom in the parent salt. In contrast, the values of theta(D) and f for A2-W-L (140 K and 0.54, respectively) were both higher than for A1-W-L (131 K and 0.49), indicating that A2 was held more tightly in the interlamellar environment than A1.