The synthesis of Graphene is critical to achieving its functions in practical applications. Different methods have been used to synthesis graphene, but graphite exfoliation is considered the simplest way to produce graphene and graphene oxide. In general, controlling the synthesis conditions to achieving the optimum yield, keeping the pristine structure to realize on-demand properties, minimum layers with the smallest lateral size, and minimum oxygen content are the most obstacles experienced by researchers. Each application requires a specific graphene model, graphene oxides GO, or even graphene intercalated compounds (GIC) depending on synthesis conditions and approach. This paper reviewed and summarized the most researches in this field and focusing on exfoliation methods.
An evaluation of the catalytic reactivity of [CPD (CO)2RuH]2 (1) and (CPD)(CO)3Ru (2) (where CPD = tetraphenylcyclopentadienone) with amines suggests that these complexes catalyze C‐N bond cleavage by activating C‐H bonds alpha to the nitrogen atom of tertiary, secondary and primary amines at ca. 140° C. When two different amines are used, transalkylation takes place. With secondary and primary amines, ammonia and tertiary amines are formed. A series of amine complexes (CPD)(CO)2Ru.NR3 (R = alkyl/H) was isolated from stoichiometric reactions of 1 or 2 with primary and secondary amines. It was found that tertiary amines do not generate complexes of the above type but rather unexpectedly give secondary amine complexes by cleavage of an alkyl group. The only isolatable tertiary amine complex is the moderately stable (CPD)(CO)2RuNMe3. All amine complexes were characterized by spectral and elemental analyses. Catalytic aspects of C‐N bond cleavage were studied. Complexes (1) and (2) were found to react with primary, secondary and tertiary amines to generate imminium or eneamine species which subsequently undergo hydrolysis with water. This is in contrast to the Ru carbene mechanism previously proposed for cluster catalyzed C‐N bond activation and cleavage. The two reactions are compared with respect to D for H exchange (with D2O), water requirement and production of trace products during catalysis. A primary alcohol was found to substitute alkyl groups of a tertiary amine under the catalytic action of 1. A catalytic reaction cycle is proposed.
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