Crystal Structure of a Dinuclear Magnesium(II) Complex with 4-Chloro-2,6-bis[(2-hydroxyethyl)methylaminomethyl]phenolate

Abstract

75Phenol-based dinucleating ligands, 2,6-bis[(2-hydroxyethyl)-methylaminomethyl]-4-methylphenolate [(sym-hmp) -] and 4-chloro-2,6-bis[(2-hydroxyethyl)methylaminomethyl]phenolate [(sym-hcp) -], are capable of forming dinuclear metal complexes [metal = cobalt(II), nickel(II), manganese(II), and zinc(II)]. [1][2][3][4][5][6] In order to expand the system to new metal ions, a magnesium(II) derivative was prepared and its crystal structure was determined by the single-crystal X-ray method.Single crystals of [Mg2(sym-hcp)2](BPh4)2·2acetone·2H2O were prepared as follows: to a methanolic solution of magnesium(II) acetate tetrahydrate (0.21 g, 1.0 mmol) was added a methanolic solution of H(sym-hcp) (0.30 g, 1.0 mmol) and LiOH (0.02 g, 0.5 mmol); the resulting solution was refluxed for 1 h. After the addition of sodium tetraphenylborate (0.34 g, 1.0 mmol), upon cooling, colorless precipitation was obtained. The compound was recrystallized from acetone, and the recrystallized sample was used for an X-ray diffraction study. Crystal data are included in Table 1. The structure was solved by direct methods and expanded using Fourier techniques. In order to eliminate the effect of abnormally strong reflections above 2θ > 55 , the "OMIT -10 55" command was executed. The non-hydrogen atoms were refined anisotropically, and hydrogen atoms were refined using the riding model. It is noted that all hydrogen atoms of OH groups were found in the difference Fourier map. The final cycle of a full-matrix leastsquares refinement on F 2 was allowed to satisfactory converge with R1 = 0.042 [I > 2σ(I)].The crystal structure consists of [Mg2(sym-hcp)2] 2+ complex cations, tetraphenylborate anions, acetone molecules, and water molecules in a 1:2:2:2 molar ratio. (Figs. 1 and 2). In the complex cation (Fig. 3), a pair of sym-hcp -ligands incorporates two magnesium(II) ions, bridged by two phenolate oxygen atoms of sym-hcp -, forming a bis-μ-phenolato-dimagnesium(II) core structure. The Mg(1)···Mg(2) separation is 3.1433(10)Å (Table 2), and very similar separations were found in the isomorphous dinuclear metal complexes: 2+ are almost equivalent, and the symmetry of the dimagnesium core is approximated as D2 symmetry (in a precise sense C2 symmetry); the dimagnesium core is twisted along the Mg···Mg axis. The dihedral angle between the two terminal N···N edges is ~51 , and the dihedral angle between the two alcoholic O···O axes is ~33 . As observed in the related isomorphous complexes, . In addition to the hydrogen bonds, OH···π interaction was observed between the water molecule and one of the phenyl groups of tetraphenylborate anion.In conclusion, the [Mg2(sym-hmp)2] 2+ complex cation was found to have a bis-μ-phenolato-dimagnesium(II) core structure, and each magnesium(II) ion was found to have a distorted octahedral geometry.

Structures of Dimer-of-Dimers Type Defect Cubane Tetranuclear Copper(II) Complexes with Novel Dinucleating Ligands

“…For example, 2,6-bis[(2-hydroxyethyl)methylaminomethyl]-4-methylphenolate ((sym-hmp) − ) [15] and 4-chloro-2,6-bis[(2-hydroxyethyl)methylaminomethyl] phenolate ((sym-hcp) − ) [16] each have a skeletal structure very similar to (sym-cmp) 3− ligand; however, the obtained complex structures are different. The (sym-hmp) − and (sym-hcp) − ligands form 2:2 (ligand:metal) metal complexes, [M 2 (sym-hmp) 2 ] (M = Mg(II) [17], Mn(II) [16], Co(II) [15,18,19], Ni(II) [20,21], Zn(II) [21]), while the (sym-cmp) 3− ligand forms 2:4 (ligand:metal) metal complexes, [M 4 (sym-hmp) 2 X 2 Y 2 ] (M = Cu(II); X = Cl − , CH 3 O − ; Y = H 2 O, CH 3 OH), as presented in this paper. This difference is thought to be caused by the difference in ligand charge.…”