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'-die thylethylenediamine, 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 prepare d and characterized by NMR spectroscopy, mass spectrometry, and thermal ana lysis. Crystal structures of compounds 2, 5, and 7 are presented. In all st ructures, Mg exhibits distorted six-coordination, with four shorter distanc es between Mg and keto-oxygens and two longer distances between Mg and nitr ogen atoms (2, 5, 7). The structure of 2 consists of two monomeric complexe s which form an asymmetric unit. The structure of 7 is similar to 2. but th e trien molecule has coordinated through one terminal and one vicinal N ato m to Mg. All complexes containing amines evaporated almost completely, but the complex 8, which contained 1,2-ethanediol, was thermally unstable and d ecomposed when heated. At temperatures below the dissociation temperature, all adducts of diamines appeared to evaporate intact.