Synthesis and structure of divalent thulium borohydrides, and their application in epsilon-caprolactone polymerisation

The new divalent thulium compound [Tm(BH4)(2)(DME)(2)] could be prepared by reduction of [Tm(BH4)(3)(THF)(3)] or from TmI2 and KBH4. It was used as a precursor to the divalent [(Tp(tBu,Me))Tm(BH4)(THF)] by reaction with potassium tris(2-tBu-4-Me) pyrazolylborate (KTp(tBu,Me)). Both Tm-II compounds were found active as epsilon-caprolactone polymerisation catalysts.