The first well-defined 1,3-butadienylzinc trimers have been synthesized by transmetalation of 1,4dilithio-1,3-butadienes with 1 equiv of ZnBr 2 . Their structures have been determined by single-crystal X-ray structural analysis. Their reaction chemistry has been demonstrated by Pd-catalyzed Negishi cross-coupling with iodobenzenes.