Ancillary ligand effect on the properties of "Mg(thd)2" and crystal structures of [Mg(thd)2(ethylenediamine)]2, [Mg(thd)2(tmeda)], and [Mg(thd)2(trien)].
Complexes [Mg(thd)2(A)] (Hthd = 2,2,6,6-tetramethyl-3,5-heptanedione; A = ethylenediamine, en (2); N,N'-dimethylethylenediamine, dmeda (3); N,N'-diethylethylenediamine, deeda (4); N,N,N',N'-tetramethylethylenediamine, tmeda (5); diethylenetriamine, dien (6); triethylenetetra-amine, trien (7); 1,2-ethanediol (8)) and [Mg(thd)2(EtOH)]2(1,3-propanediol) (9) were prepared and characterized by NMR spectroscopy, mass spectrometry, and thermal analysis. Crystal structures of compounds 2, 5, and 7 are presented. In all structures, Mg exhibits distorted six-coordination, with four shorter distances between Mg and keto-oxygens and two longer distances between Mg and nitrogen atoms (2, 5, 7). The structure of 2 consists of two monomeric complexes which form an asymmetric unit. The structure of 7 is similar to 2, but the trien molecule has coordinated through one terminal and one vicinal N atom to Mg. All complexes containing amines evaporated almost completely, but the complex 8, which contained 1,2-ethanediol, was thermally unstable and decomposed when heated. At temperatures below the dissociation temperature, all adducts of diamines appeared to evaporate intact.
Department of Chemistry, Laboratory of Inorganic Chemistry, University of Helsinki, P.O. Box 55, FIN-00014 Helsinki, Finland.
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