Insertion of Carbenes into Deprotonated nido-Undecaborane, B11H13(2-).

We have examined the insertion of carbenes carrying leaving groups into the [nido-B11H13]2- dianion to form the [closo-1-CB11H12]- anion. The best procedure uses CF3SiMe3 and LiCl as the source of CF2. It is simple, convenient and scalable and proceeds with 70-90% yield. Density functional calculations have been used to develop a mechanistic proposal that accounts for the different behavior of CF2, requiring only one equivalent of base for successful conversion of Na[nido-B11H14]- to [closo-1-CB11H12]-, and CCl2 and CBr2, which require more.