  We demonstrate the organometallic hexahapto complexation of chromium with
graphene, graphite and carbon nanotubes. All of these extended periodic
pi-electron systems exhibit some degree of reactivity toward the reagents
CrCO)6 and (eta6-benzene)Cr(CO)3, and we are able to demonstrate the formation
of (eta6-rene)Cr(CO)3 or (eta6-arene)2Cr, where arene = single-walled carbon
nanotubes (SWNT), exfoliated graphene (XG), epitaxial graphene (EG) and
highly-oriented pyrolytic graphite (HOPG). We find that the SWNTs are the least
reactive presumably as a result of the effect of curvature on the formation of
the hexahapto bond; in the case of HOPG, (eta6-HOPG)Cr(CO)3 was isolated while
the exfoliated graphene samples were found to give both (eta6-graphene)2Cr, and
(eta6-graphene)Cr(CO)3 structures. We report simple and efficient routes for
the mild decomplexation of the graphene-chromium complexes which appears to
restore the original pristine graphene state. This study represents the first
example of the use of graphene as a ligand and is expected to expand the scope
of graphene chemistry in connection with the application of this material in
organometallic catalysis.

Chemical Physics;Materials Science