Stannyl- and silyl-ortho-carboranes serve as an ortho-carborane carbanion equivalents in the addition reaction to aldehydes. The reaction of (tributylstannyl)-ortho-carborane 2 with aldehydes 4 in the presence of palladium(0) catalysts gave the corresponding (ortho-carboranyl) carbinols 5 in good to high yields. The reaction of (trimethylsilyl)-ortho-carborane 3 with aldehydes 4 in the presence of tetrabutylammonium fluoride (TBAF) gave the corresponding (ortho-carboranyl) carbinols 5 in high yields. Furthermore, (trimethylsilyl)-ortho-carborane 3 underwent a facile [3+2] annulation reaction with various α,β-unsaturated enals and enones in the presence of tetrabutylammonium fluoride, giving the corresponding five-membered carboracyclic products 14 in good to high yields.