Targeted Rapid Synthesis of Redox-Active Dodecaborane Clusters
We have developed a fast, efficient route to obtain targeted perfunctionalized ether-linked alkyl and benzyl derivatives of the closo-[B12(OH)12]2- icosahedral dodecaborate cluster via microwave-assisted synthesis. These icosahedral boron clusters exhibit unique properties including three-dimensional delocalization of the cage-bonding electrons, tunable photophysical properties, and a high degree of stability in air in both solid and solution states. Several B12(OR)12 clusters have been prepared with reaction times ranging from hours to several minutes using microwave-assisted synthesis. This represents a significant improvement upon previously reported protocols due to a dramatic reduction in required reaction times and the elimination of the need for inert atmosphere conditions. The robust nature of the new microwave-based method has been further demonstrated through the targeted synthesis of several new derivatives, which feature desired properties such as redox potentials up to 0.6 V more positive than previously known B12(OR)12 cluster compounds or substituents that allow further facile functionalization via thiol “click” SNAr. We further demonstrate the ability to synthesize hybrid, vertex-differentiated cluster species B12(OR)11(OR’) via a single-step one-pot reaction that was formerly accessible only via multi-step reaction sequence.