General synthetic routes to zirconium metallocene-like complexes containing derivatives of the dianionic trimethylenemethane (TMM) ligand are presented. One approach consists of reacting the dilithium salts of TMM, tribenzylidenemethane (TBM), tert-butyltribenzylidenemethane (t-Bu-TBM), and dibenzylidenemethylenemethane (DBM) with either Cp*ZrCl3 or CpZrCl(3)(DME). In the case of the small TMM fragment, the product is the zwitterionic Cp*(TMM)Zr(mu-Cl)(2)Li(TMEDA) (1). Larger TMM derivatives give discrete salts such as [Cp*(TBM)ZrCl2][Li(TMEDA)(2)] (2), [Cp(TBM)ZrCl2][Li(TMEDA)(2)] (3), [Cp(t-Bu-TBM)ZrCl2][Li(TMEDA)(2)] (4), [Cp*(t-Bu-TBM)ZrCl2][Li(TMEDA)(2)] (5), and [Cp*(exo-endo-DBM)ZrCl2][Li(TMEDA)(2)] (6). The reaction of TBM(LiTMEDA)(2) with Cp*ZrCl(2)CH(2)Ph affords [Cp*(TBM)ZrCl(CH(2)Ph)][Li(TMEDA)(2)] (9); thus the retention of LiCl(TMEDA)(2) by zirconium is strong. Structural characterization of these complexes reveals crowded environments around the zirconium, especially when both TBM and Cp* are coordinated. It is also possible to take advantage of intramolecular sigma-bond metathesis reactions to convert coordinated allyl ligands to TMM-related fragments. For example, [Cp*(TMM)Zr](2)(mu-CH2) (10) is derived from Cp*(eta(3)-CH2C(Me)CH2)ZrMe(2), and Cp*(TBM)ZrMe(THF) (12) is from Cp*(PhCH(2)C(CHPh)(2))ZrMe(2) (11). Formation of the methylpropargyl complex Cp*(TBM)Zr(eta(3)-CH(2)CCMe) (13) from Cp*(TBM)ZrMe(THF) and 2-butyne instead of a butenyl derivative is a consequence of steric constraints. Activation of 2-6 with methylaluminoxane affords homogeneous catalyst mixtures for polymerization of ethylene and 1,5-hexadiene and copolymerization of ethylene with 1-hexene. There is a strong correlation between catalyst precursor structure and reactivity. Polyethylene can also be prepared by pressurizing a vessel containing only Cp*(TBM)ZrMe(THF).