Metal-dependent regioselective homocoupling of stannyl- and alkyl-substituted alkynes on group 4 elements. Formation of unsymmetrical titanacyclopentadienes and symmetrical zircona-cyclopentadienes.

Homocoupling of stannyl- and alkyl-substituted alkynes with Cp2TiBu2 gave unsymmetrical titanacyclopentadienes (αβ isomers) with >95% regioselectivities, whereas the coupling with Cp2ZrBu2 provided symmetrical zirconacyclopentadienes (αα isomers) with >93% selectivities. This is the first example of metal-dependent regioselective homocoupling of unsymmetrical alkynes on group 4 elements.