Unexpected Reactions between Ziegler–Natta Catalyst Components and Structural Characterization of Resulting Intermediates

Abstract

In this work, we investigated precursors and procatalysts with well-defined crystal structures and morphologies in Ziegler-Natta systems to improve our understanding of the nature of the active metal sites. Molecular cluster precursors such as [Mg4Ti3(μ6-O)(μ3-OH)3(μ-OEt)9(OEt)3(EtOH)3Cl3], [Mg4Ti3(μ6-O)(μ3-OH)(μ3-OEt)2(μ-OEt)9(OEt)3(EtOH)3Cl3], and [Mg6Ti4(μ6-O)2(μ3-OH)4(μ-OEt)14(OEt)4(EtOH)2Cl2] were prepared via simple elimination of the cyclopentadienyl ring from Cp2TiCl2 as CpH in the presence of magnesium metal and ethanol. Titanocene dichloride acts as both a source of titanium and a magnesium-chlorinating agent. The resulting novel complexes were characterized using single-crystal X-ray diffraction. In these compounds, Ti(OEt)4 molecules are grafted onto Mg4 and Mg6 ethoxide cubane-like surfaces; this strongly affects the procatalyst morphology, which is transferred to the polymer. Mg4(OR)8 units act as carriers for the AlR3 co-catalyst, resulting in return of alkyl functions to the Ti center.

Hydrolysis of organometallic and metal–amide precursors: synthesis routes to oxo-bridged heterometallic complexes, metal-oxo clusters and metal oxide nanoparticles

“…96 While a vast amount of research has focused on the conversion of M−OR groups to M−O−M' units, this topic has been extensively covered in other reviews and will not be discussed in detail here. 118,69 Other successful yet less widely-developed strategies to form oxobridged heterometallic complexes include C−H deprotonation to yield zwitterionic complexes; 119, 120 oxidation of heterometallic precursors; 121,122 use of a heterometallic reagent to encapsulate oxo dianions from air or ethereal solvents; [123][124][125] or adduct formation from a donor M=O functionality to a Lewis acidic metal centre. 126 Here we shall focus on the well-established and versatile dealkylation or deamination routes from organometallic/metal-amide precursors.…”

Probing Interactions between Electron Donors and the Support in MgCl2-Supported Ziegler–Natta Catalysts

“…Recent years have seen more experimental studies that focus on structure–function relationships, for both traditional MgCl 2 -based ZNCs − and new MgCl 2 -derived support materials. − Still, many studies try to investigate the produced polymer in intricate ways to learn more about these elusive catalysts via an indirect approach . It is our belief that the final answers about the working mechanisms of ZNCs will primarily be found when studying the catalysts themselves …”

Molecular Routes to Group IV Magnesium and Calcium Nanocrystalline Ceramics

“…According to our previous work, the reaction of Cp 2 TiCl 2 with 2 equiv of metallic magnesium in ethanol (EtOH)/toluene (3:1) at room temperature gave colorless cyclopentadienyl-free crystals of [Mg 2 Ti 2 (μ 3 -OEt) 2 (μ-OEt) 4 (OEt) 6 (EtOH) 4 ] (1, 62%). 24 Moreover, when zirconocene and hafnocene dichloride were used instead of Cp 2 TiCl 2 under the same conditions, we obtained compounds [Mg 2 Zr 2 (μ 3 -OEt) 2 (μ-OEt) 4 (OEt) 6 (EtOH) 4 ] (2, 70%) and [Mg 2 Hf 2 (μ 3 -OEt) 2 (μ-OEt) 4 (OEt) 6 (EtOH) 4 ] (3, 73%), respectively, which are isostructural to 1 (Scheme 1).…”