Model reactions between neat Bu(2)SnOct(2) and benzylalcohol suggest that no exchange occurs at temperatures less than or equal to 60 degrees C. However, at 100 degrees C a dow esterification process yielding benzyl octanoate and Sn-OH groups takes place. Bu(2)SnOct(2) is a little less reactive than SnOct(2), but polymerizes trimethylene carbonate (TMC) at 80 degrees C. Addition of benzylalcohol accelerates the polymerization process and allows controlling the molecular weight via the TMC/alcohol ratio. The resulting poly TMC contains the stoichiometric quantity of benzyl carbonate endgroups. Neat Bu(2)SnOct(2) reacts above 120 degrees C with TMC by transesterification and formation of octanoate endgroups. However, a satisfactory control of M-n via the M/I ratio is not possible, and the "backbiting" degradation competes with the polymerization process at high conversions.