The synthesis, characterization, and reaction chemistry of a cationic Pt(II) solvento complex (2) are described. The complex demonstrates the unprecedented ability to promote polymerization of the electron-rich olefins ethyl vinyl ether (EVE), N-vinylcarbazole (NVC), and 2,3-dihydrofuran (DHF) via cationic initiation and subsequent propagation of the carbocation.