Composés d'insertion ternaires graphite-métal alcalin Lourd-Benzène

Abstract

Graphite-alkali metal M-benzene ternary intercalation compounds (with M = K, Rb, Ca) have been prepared by immersing binary intercalation compounds of various stages in liquid benzene at room temperature. After a few hours or days, depending on the origin of the graphite (Ceylon or Madagascar), the sample is gently dried and analysed. The results are very similar whatever may be the alkali metal or the graphite when contact time in benzene is long enough. First stage binary compounds MC 8 show no change, but those of second stage or over swell in the benzene. Extensive chemical and thermal analysis done on K compounds allow the formula KC 24(C 6H 6) 2.25–3.1 for the compound prepared from KC 24. X-ray diffraction patterns of ternary compounds are identical whatever may be the alkali metal K, Rb, Cs. Changes in stage occur by intercalation of benzene; a second stage binary compound gives a first stage ternary compound, a third stage gives a mixture of first and second stage ternary compounds, etc. Identify periods I c along the c axis are 9.29 Å for MC 24(C 6H 6) x (first stage), 12.60 Å for MC 48(C 6H 6) x (second stage)…. The absence of variation of the structural parameters with alkali metal size suggests that only the benzene molecules are responsible for the layer spacing in ternary compounds. A free space of 5.94 Å implies that benzene molecules are perpendicular to the graphite layers.