Molecular Structure of a Hydridoniobocene Complex [Nb(η5‐C5H4SiMe3)2(H)3] and Its Use as Catalyst for the Ring‐Opening Polymerization of Cyclic Esters

Abstract

AbstractThe second polyhydridoniobocene complex that was characterized by X‐ray diffraction is reported. On the basis of H–H distances and H–Nb–H angles, [Nb(η5‐C5H4SiMe3)2(H)3] (1) is classified as a “compressed hydride”. Compound 1 acts as an efficient single‐component initiator for the ring‐opening polymerization of ϵ‐caprolactone and δ‐valerolactone. ϵ‐Caprolactone and δ‐valerolactone are both polymerized within a few hours to yield high‐to‐medium‐molecular‐weight polymers with medium to broad polydispersities. Polymer end‐group analysis showed that the polymerization proceeds through a coordination–insertion mechanism based on the cleavage of the ring between the oxygen atom and the acyl carbon atom.