Crystalline magnesium chloride–electron donor complexes: new support materials for Ziegler–Natta catalysts

Abstract

In this study, crystalline magnesium chloride-electron donor complexes were prepared by recrystallization of δ-MgCl in the presence of chelating electron donors, including two diethers (1,2-dimethoxyethane; DME and 1,3-dimethoxypropane; DMP) and one diamine (N,N'-diethylethylenediamine; DEEDA). The syntheses and crystal structures of such magnesium chloride complexes with chelating ligands have been rarely reported, even though they can provide important information for the selection of electron donors for stereoselective MgCl-supported Ziegler-Natta catalysts. The synthesized complexes were characterized using single-crystal X-ray diffraction, and FTIR and CP/MAS C NMR spectroscopy methods. A polymeric complex [MgCl(DME)] and molecular complexes [MgCl(DMP)(HO)] and [MgCl(DEEDA)] were formed in recrystallizations. In all complexes, the bidentate electron donors are bound in chelate binding mode. The [MgCl(DME)] complex, the structure of which consists of a helical polymeric MgCl backbone chain and one DME molecule coordinated to each Mg atom, can be considered as a structural model for layered MgCl. The crystal structure of the [MgCl(DMP)(HO)] complex is composed of a tetrahedral Mg atom with four Cl ligands and a distorted octahedral Mg atom with two DMP molecules, one water molecule, and one Cl ligand. The two types of Mg atoms are connected to each other with a bridging Cl ligand. In the [MgCl(DEEDA)] complex, magnesium is octahedrally coordinated by two chloride ligands trans to each other and two DEEDA molecules. The structures of the obtained magnesium chloride-electron donor complexes clearly show how diether and diamine electron donors can dictate the crystal structure of MgCl.

New Insight into Titanium–Magnesium Ziegler–Natta Catalysts Using Photoluminescence Spectroscopy

“…For example, MgCl 2 · (LB) 2 , where LB is ethyl acetate, ethyl propionate, EB, ethyl crotonate, acetone or 2-butanone, ethanol, THF, [Mg 2 Cl 4 (1,3-dimethoxypropane) 2 (H 2 O)]. 12,32–34…”

“…The formation of [MgCl 2 Á (LB) x ] n molecular complexes during the synthesis of the MgCl 2 /LB support has been suggested previously. 30,31 12,[32][33][34] The DFT calculations also show the possibility of the formation of molecular complexes upon adsorption of donors (1,3-diethers, alkoxysilanes, and succinates) on magnesium chloride. 35 In such complexes, two oxygen atoms of one or two LB are bound to a four-coordinated magnesium ion.…”

Genesis of MgCl2‐based Ziegler‐Natta Catalysts as Probed with Operando Spectroscopy

“…As a matter of fact, the distribution of the active phase has already been proved to depend on the relative extent of the surfaces exposing either 4-fold coordinated Mg 2 + sites, as the (110) surface, or 5-fold coordinated Mg 2 + sites, as the (104) one. [32,[46][47][48][49][50][51][52][53][54][55] The latter method was recently proved to promote the formation of MgCl 2 nanocrystals whose morphologies depend on the starting alcoholic adduct. [32,[46][47][48][49][50][51][52][53][54][55] The latter method was recently proved to promote the formation of MgCl 2 nanocrystals whose morphologies depend on the starting alcoholic adduct.…”

“…[44,45] In the industrial practice, several procedures are adopted to produced MgCl 2 -based materials, including the mechanical ball-milling of MgCl 2 in the co-presence of TiCl 4 and suitable electron donors, the decomposition of previously synthesized adducts between MgCl 2 and Lewis bases (such as alcohols or ethers) in the presence of TiCl 4 , and the direct chlorination of Mg and Ti alkoxides with AlR n Cl 3-n compounds. [32,[46][47][48][49][50][51][52][53][54][55] The latter method was recently proved to promote the formation of MgCl 2 nanocrystals whose morphologies depend on the starting alcoholic adduct. [45,[56][57][58][59][60] In the past, Thune and coworkers monitored by FT-IR spectroscopy in ATR mode the direct transformation of the alcoholate precursor into the Ziegler-Natta pre-catalyst in the presence of TiCl 4 and an electron donor.…”

Structure of Magnesium Chloride Complexes in Ethereal Systems: Computational Comparison of THF and Glymes as Solvents for Magnesium Battery Electrolytes

“…). [61][62][63] An analogous structure, with one additional chlorine anion around the central magnesium cation, replacing the G1 molecule, was found to be the most stable for Mg 3 Cl 5 + stoichiometry (Mg 3 Cl 5 (G1) 4 + : À 1783 kJ mol À 1 ; 3 × À 594 kJ mol À 1 - Figure S4d). Surprisingly, the pyramidal structure observed in the THF system, is not as preferred (Mg 3 Cl 5 (G1) 3…”