Reaction of two equivalents of the bi-dentate 2,2?-PhCH[4,6-(t-Bu)2C6H2OH]2 with one equivalent of niobium pentachloride gave the complexes Nb{2,2?-PhCH[4,6-(t-Bu)2C6H2O]2}2 (1) . Similar use of two equivalents of the same ligand with one equivalents tantalum pentachloride afforded Ta{2,2?-PhCH[4,6-(t-Bu)2C6H2O]2}2 (2). The molecular structure of complexes (1) and (2) have been characterised by IR, 1HNMR. Both complexes were investigated as catalysts polymerization of cyclicesters (?-caprolactone) with no solvent at various temperature in all cases, the polymer produced was of high conversion