New ionic complexes with various metals (Mg2+, titanium in various oxidation states, and iron triad metals) in the 15-crown-5 cavity as a cation and a titanium-containing anion have been synthesized. The structure of some synthesized complexes was determined by X-ray diffraction analysis. These compounds, in the presence of the Al/Mg activator {Et2AlCl + Bu2Mg}, catalyze the polymerization of ethylene with the formation of ultrahigh molecular weight polyethylene (UHMWPE) with molecular weights up to 2.56·106 Da. Only complexes with a titanium-containing anion showed catalytic activity; its maximum value −4651 kg of PE/mol·h·atm was exhibited by the complex [15C5 ⊃ FeIIICl·2CH3CN]2+[Ti2Cl10]2-. The resulting ultra-high molecular weight polyethylene (Mv to 2.56•106 Da) can be processed by a solventless method into high-strength (up to 2.45 GPa) and high-modulus (up to 144 GPa) oriented tapes. Most polyethylene samples have a linear structure, with the exception of polymers obtained on Ni/Ti complexes, which have 2–3 branches per 1000 carbon atoms.