Catalyst Residue and Oxygen Species Inhibition of the Formation of Hexahapto-Metal Complexes of Group 6 Metals on Single-Walled Carbon Nanotubes

The reaction of Group 6 metals with SWCNT has the potential to bridge the resistive SWCNT ... SWCNT junctions by the formation of Cr(SWCNT)(2) complexes analogous to Cr(C6H6)(2). This study reports that the formation of such species is very sensitive to oxidation by a residual iron oxide catalyst used for the growth of the SWCNTs and adsorbed/bound oxygen functionality. The reaction of raw HiPco SWCNTs with M(CO)(6) and (C7H8)M(CO)(3) (M = Cr, W) or (C6H6)Cr(CO)(3) results in the formation of the Group 6 metal oxides. Annealing and acid treating the HiPco SWCNTs to reduce the catalyst content allows for the observation of zero valent metals by XPS, while the use of very high purity SWCNTs and graphene allows for the addition of primarily zero valent Group 6 metals, including the bis-hexahapto metal complex.