The BH compounds IMes(Ar^F)BH(NTf₂) (Ar^F: C₆F₅ or FpXyl) were converted to the IMes(Ar^F)BCH₂ boraalkenes in a three step reaction sequence of B-methylation with methyllithium, hydride abstraction and deprotonation. The BCH₂ boraalkenes reacted with elemental sulfur to give a thiaborirane product. They underwent [2+2] cycloaddition reactions with carbon dioxide or sulfur dioxide to give four-membered boron containing heterocycles. The boraalkenes added strongly Lewis acidic boranes at their CH₂ carbon atoms. The corresponding HB(C₆F₅)₂/boraalkene adduct reduced carbon monoxide to a –OCH(C₆F₅)– moiety inside a five-membered heterocycle at the B–CH₂–B template. The boraalkenes reacted with the [(Me₂S)AuCl] reagent to form the corresponding (boraalkene)AuCl complexes.