The first highly efficient, diastereo-and regioselective transition metal-catalyzed addition of metal hydrides (stannanes, silanes, and germanes) and bimetallic species (ditins and silyltins) to cyclopropenes has been developed. It was shown that the addition across the double bond of cyclopropenes is generally controlled by steric factors and proceeds from the least hindered face. This methodology represents a powerful and atom-economic ...