Carbon–tin bonds in alkynyl-, allyl-, acyl-, alkenyl-, and arylstannanes were found to add to carbon–carbon unsaturated bonds of alkynes, 1, 3-dienes and 1, 2-dienes in the presence of a catalytic amount of palladium or nickel complexes to give alkenyl-or allylstannanes having various functional groups. Mechanisms are proposed that start with oxidative addition of a carbon–tin bond, or palladacycle formation followed by β-tin elimination or by ...