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The regioselective head-to-head dimerization of alkynes is catalyzed by a dibenzyl tethered bis(ureate) zirconium precatalyst with aniline as an additive. This system also gives outstanding stereoselectivity to furnish Z-enynes in high yields. A dinuclear reactive intermediate has been characterized, which provides a potential mechanistic rationale for the unexpected regio- and stereoselectivity in this catalytic system.