Rodlike Polymers Containing Nickel and Cobalt Metal Bis(dicarbollide) Anions: Synthesis and Characterization

Two approaches for the synthesis of rodlike polymers having metal bis(dicarbollide) anions connected by organic linkers, such as acetylene and 1,4-dibutyl-2,5diethynylbenzene, in the backbone are reported. Route 1 involved connecting nido-bis(carborane) compounds, containing the linkers, via pi coordination with Co or Ni metals. This reaction yielded small oligomers having one to six repeating units. Route 2 utilized a palladium-catalyzed cross-coupling copolymerization of diiodo-substituted cobaltocarboranes and a zinc-derivatized aromatic linker. This approach gave a mixture of oligomers and polymers. The polymers were separated from the smaller oligomers by dialysis and were characterized by H-1 NMR, B-11 NMR, B-11{H-1} NMR, IR, UV-vis, TEM, and AFM techniques. End-group analysis and dynamic-light scattering experiments (DLS) determined that the average number of repeating units in the polymers ranged between 35 and 44. GPC analyses failed to aid the molecular weight determination due to the adsorption of the polymers to the stationary phase of the column. Dilute-solution viscometry experiments supported the semirigid nature of these polymers.