HYDROGENATION OF FULLERENES C-60 AND C-70 IN THE PRESENCE OF HYDRIDE-FORMING METALS AND INTERMETALLIC COMPOUNDS

Hydrogen-absorbing intermetallics generate very pure and chemically ac tive hydrogen. In this communication we report on the use of this prop erty for hydrogenation of fullerenes (C-60, C-70) in solvent-free soli d-phase systems. Fullerene hydrides with high contents of hydrogen (24 -26 H atoms per fullerene molecule) have been obtained by hydrogenatio n of solid-phase mixtures of fullerite with either intermetallic compo unds LaNi5, LaNi4.65Mn0.35, CeCo3 or V and Pd metals in relatively mil d conditions, a hydrogen gas pressure of 1.0-2.5 MPa and 573-673 K. Th e mechanochemical treatment of initial solid compositions and repeated 'hydrogenation-dehydrogenation' cycling are both essential to ensure the highest performance of the systems studied, thus emphasizing the i mportance of a highly developed contact surface between two solid phas es and indicating a probable formation of metal-carbon bonds. The full erene hydrides thus obtained decompose in all cases at 800 K, liberati ng hydrogen gas. After further heating tip to 1000 K vanadium reacts w ith fullerenes yielding a cubic phase of vanadium carbide. Intermetall ics under the same conditions react with fullerenes by disintegrating their cage and producing a metallic phase of the corresponding 3d meta l. In the case of palladium that reaction is not observed and the full erene remains intact. The nature of the transformations in the mechani cal mixtures of fullerite with metals or intermetallics is discussed.