X-ray Structure and Raman Spectrum of [Ti(4)(&mgr;(3)-O)(2)(&mgr;(2)-O(i)()Pr)(2)(O(i)()Pr)(8)(acac)(2)]: Presence of a Ti(4)(&mgr;(3)-O)(2)(&mgr;(2)-O(i)()Pr)(2) Ladder-like Core.