The equimolar reaction of calcium bis[bis(trimethylsilyl)amide] with 2,2,6,6‐tetramethylheptane‐3,5‐dione (Htmhd) in THF yields liquid mononuclear [Ca(tmhd){N(SiMe3)2}(THF)3] (1). A similar reaction in toluene with a stoichiometric ratio of 2:3 gives the dinuclear complex [{(THF)Ca}2(tmhd)2(µ‐tmhd){µ‐N(SiMe3)2}] (2). The calcium atoms of these complexes are in a distorted octahedral environment. In 2 the complex consists of two octahedra connected by a common face of one nitrogen base and two oxygen atoms; the bridging Ca−N bond lengths are extremely large. The metalation of the tetradentate Jacobsen reagent with calcium bis[bis(trimethylsilyl)amide] in 1,2‐dimethoxyethane (DME) gives the corresponding calcium complex 3, nearly quantitatively, as its DME adduct. The calcium atom is in an unusual trigonal prismatic coordination sphere. The metathesis reaction of 3 with tin(II) chloride yields the corresponding yellow tin(II) complex with the metal atom in a distorted square‐pyramidal environment. Complexes 2 and 3 show catalytic reactivity in the ring‐opening polymerization of cyclic esters such as lactones and lactides. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

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The zincation of bis(2-pyridylmethyl)amine with dimethylzinc yields dimeric methylzinc bis(2-pyridylmethyl)amide (1) with a central Zn2N2 cycle with Zn-N distances of 204.8(5) and 209.8(4) pm. The Zn-C bond length of 197.0(5) pm lies in the characteristic region. The addition of dimethylzinc to 1 leads to an opening of the Zn2N2 cycle and the formation of tetramethyltrizinc bis[bis(2-pyridylmethyl)amide] (2). The dimethylzinc molecule coordinates to a pyridyl and an amide group, the C-Zn-C bond angle of 135.3(3) being rather large. In solution, compound 2 loses methane at room temperature and the intramolecular metalation product tris(methylzinc) bis(2- pyridylmethyl)amide 1,3-di(2-pyridyl)-2-azapropane-1,2-diide (3) precipitates. The newly formed Zn-C bond is extremely long at 219.7(5) pm.

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