Functionalization of closo-Borates via Iodonium Zwitterions

A simple method for the functionalization of closo-borates [closo-B10H10](2-) (1), [closo-1-CB9H10](-) (2), [closo-B12H12](2-) (3), [closo-1-CB11H12](-) (4), and [3,3-Co(1,2-C2B9H11)(2)](-) (5) is described. Treatment of the anions and their derivatives with ArI(OAc)(2) gave aryliodonium zwitterions, which were sufficiently stable for chromatographic purification. The reactions of these zwitterions with nucleophiles provided facile access to pyridinium, sulfonium, thiol, carbonitrile, acetoxy, and amino derivatives. The synthetic results are augmented by mechanistic considerations.