The insertion of H2CCHX (X = OR; R = Me, Et, nPr, iPr, CHCH2, Ph) into (tBu3SiO)3TaH2 (1) afforded (tBu3SiO)3HTaCH2CH2X (2-CH2CH2X), which β-X-eliminated to give ethylene and (tBu3SiO)3HTaX (3-X). β-X-elimination rates were inversely proportional to the size of...