INTERCALATIVE REACTION OF A COBALT(III) CAGE COMPLEX, CO(SEP)3+, WITH MAGADIITE, A LAYERED SODIUM-SILICATE

The cationic metal cage complex (1,3,6,8,10,13,16,19-octaazabicyclo[6.6.6]eicosane)cobalt(III), Co(sep)3+, has been investigated as a potential pillaring reagent for Na+-magadiite (Na1.7Si14O27.9(OH)1.9 . 7.6 H2O) a synthetic layered sodium silicate. Reaction of Na+-magadiite with aqueous solutions of Co(sep)Cl3, at 25-degrees-C resulted in the binding of Co(sep)3+ cations to the external crystalline surface of the layered silicate. In contrast, an intercalated product exhibiting a 17.6 angstrom basal spacing was generated by reaction at 100-degrees-C. Si-29 MAS NMR and FT-IR spectroscopy indicate that Co(sep)3+ intercalated reaction products retain the magadiite layer structure. Moreover, scanning electron micrographs of the reaction products showed retention of the original particle morphology, suggesting a topotactic intercalation. However, during intercalation, some of the Co(sep)3+ was found to undergo an unusual demetalation reaction leaving a combination of Co(II) and Co(sep)3+ between the layers. Nitrogen surface area analysis showed that only a small amount of microporous surface existed in the Co(sep)3+ intercalated derivative. suggesting that most of the interlayer space is 'stuffed' with cobalt species.