The reduction of 2- [(2,6-diisopropylphenyl)imino]acenaphthen-1-one (dpp-MIAN) with metallic calcium in THF affords tetrameric [(dpp-MIAN)Ca(THF)] 4 (1). A further addition of dpp-MIAN to complex 1 leads to the formation of paramagnetic species [(dpp-MIAN) 3 Ca] 2 Ca (2). Both complexes were characterized by X-ray diffraction. Complex 1 is active towards phenylacetylene and acetylene at temperatures above 80 °C. As a result, cycloaddition products are formed. Their hydrolysis results in a release of the dpp-MIAN ligand with an attached phenylethynyl or ethynyl moiety to the carbonyl C atom. Complexes 1 and 2 demonstrate catalytic activity in the polymerization of L-lactide both in solution and in bulk.