Utilization of the bulky acetylide, (Bu3SiC)-Bu-t=C-, enabled the synthesis of several early metal polyacetylides. Addition of NaC=CH to (Bu3SiBr)-Bu-t in dimethyl sulfoxide afforded (Bu3SiC)-Bu-t=CH, which was deprotonated to yield (Bu3SiC)-Bu-t=CLi. Treatment of ZrCl4, HfCl4, and TaCl5 with varying amounts of Bu-t(3)-SiC=CLi gave {(THF)(2)Li((Bu3SiC)-Bu-t=C)(2)}Zr(C=(CSiBu3)-Bu-t)(3)(THF) (1; THF = tetrahydrofuran), {(Et2O)Li(Bu-t(3)-SiC=C)(2)}Hf(C=(CSiBu3)-Bu-t)(3)(OEt2) (2), {Li((Bu3SiC)-Bu-t=C)(3)}(2)M (M = Zr, 6; Hf,7), and {Li((Bu3SiC)-Bu-t=C)(3)}Ta(C=(CSiBu3)-Bu-t)(3) (3). Metathesis of 3 with KOTf generated KTa(C=(CSiBu3)-Bu-t)(6) (4) and cation sequestration of 4 with crypt 2.2.2 provided [K(crypt 2.2.2)][Ta(C=(CSiBu3)-Bu-t)(6)] (5). Single-crystal X-ray structural studies determined the structures (core symmetry) of 1 (O-h), 2, (O-h), 3 (D-3), 5 (D-3), 6 (O-h), and 7 (O-h). The D-3h to D-3 twist in 3 and 5 has a steric origin, and the counterion position appears inconsequential. Origins of the structural preferences illustrated by the dichotomous twisted trigonal prismatic and octahedral cores of the d(0) hexaacetylides 5 and 6 were probed through density functional (ADF) and effective core potential (GAMESS) calculations. The structural difference results from a lessening electronic preference for the trigonal prism-primarily a greater HOMO/LUMO gap-upon moving from Ta to Zr, minor steric factors, and increased interligand repulsions in the dianion (VSEPR).