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Reaction of dppBIANMgTHF31 {dppBIAN = 1,2bis[2,6diisopropylphenylimino]acenaphthene} with one molar equivalent of 2,2,6,6tetramethylpiperidine1oxyl TEMPO proceeds with oxidation of the dppBIAN dianion in 1to the radicalanion and affords the dppBIANMgTEMPOthf 2 complex. The reaction of dppBIAN with an excess amount of magnesium and 0.5 molar equivalents of I2in Et2O gives dppBIANMgIEt2On, which then reacts in situ with Me3Si2NK to produce dppBIANMg[NSiMe32]Et2O 3. Solventfree magnesium amide dppBIANMg[NSiMe32] 4 was synthesized by treating equimolar amounts of MgI2, dppBIAN, and sodium in toluene at reflux followed by treatment with Me3Si2NK. Deprotonation of diphenylacetonitrile with [dppBIANMgμMe]25 produces keteniminate complex dppBIANMgN=C=CPh2Et2O 6. Complexes 2–4and 6were characterized by ESR and IR spectroscopy; their molecular structures were determined by singlecrystal Xray analysis. Compounds 1–3catalyze the ringopening polymerization of L and raclactides to give high molecular weight isotactic and stereoblock polylactides correspondingly.© WileyVCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009