Synthesis and Characterization of Group 4 Fluorinated Bis(amidinates) and Their Reactivity in the Formation of Elastomeric Polypropylene

Abstract

Bis(amidinate) titanium and zirconium bis-(dimethylamido) complexes were prepared, and the dynamic behavior of the titanium complex containing perfluorinated amidinate ligand (11) was studied in detail. The variabletemperature NMR revealed the presence of two species in solution, in line with the different connection modes of the ligand to the metal center. The resulting complexes were tested as catalysts in the polymerization of propylene, and the resulting polymers were consistent with elastomeric high-molecularweight atactic polypropylenes.

(Amido)‐ and (Chlorido)titanium and ‐zirconium Complexes Coordinated by ansa‐Bis(amidinate) Ligands with a Rigid o‐Phenylene Linker

“…The Zr–N(amidine) bond lengths are also somewhat different from each other; N(1) and N(1A) are located much closer to the metal center [2.241(3) Å] than the two nitrogen atoms from the 2,6‐Me 2 C 6 H 3 N groups [2.373(3) Å]. These bond lengths fall in the same range measured for related bis( N , N′ ‐amidinate)–Zr IV (NMe 2 ) 2 complexes . They are markedly longer than those measured for bis( N , O ‐mesitoylamidate)–Zr IV (NMe 2 ) 2 compounds , .…”

“…They are markedly longer than those measured for bis( N , O ‐mesitoylamidate)–Zr IV (NMe 2 ) 2 compounds , . Finally, the Zr–N bond length of the amido group belonging to the plane of the pentagonal bipyramid falls in the typical range of hexacoordinate bis(amido)zirconium species [2.096(3) Å] with either N ⌢ N, , or N ⌢ O, , amidinate ligands. On the contrary, the Zr–N bonds of the amido groups (NMe 2 ) at the apical positions [2.294(3) Å] are markedly longer.…”

“…Group 4 transition‐metal complexes containing chelating amidinate ligands have received much attention in recent years owing to their easy synthetic access and stability. These features make them valuable candidates as precatalysts in olefin polymerization . Following our interest in the coordination chemistry of highly electrophilic metal ions in combination with sterically demanding amidinate ligands, for applications in catalysis, in this work, we report the synthesis, structure, and stability of a series of amido–Zr IV /Ti IV and chlorido–Zr IV complexes stabilized by bis(amidinate) ligands tethered by a rigid o ‐phenylene linker.…”

Group 4 metal complexes for homogeneous olefin polymerisation: a short tutorial review

“…Other Tp-supported Group 4 polyolefin catalysts have also been investigated by other groups [89][90][91][92]. In addition, Group 4 non-cyclopentadienyl catalysts supported by j 2 N,N 0 -amidinate ligands have also been reported [93][94][95][96].…”

Amidinate group 4 complexes in the polymerization of olefins

“…The positions of the fluorine atoms in the ligand were found to influence the R i and R t values as compared to the corresponding complex without fluorinated ligands (28). 78 As the use of electron withdrawing groups (EWG) led to more active, but less stereoselective titanium and zirconium complexes compared to the unsubstituted amidinates, the study of electron donating groups (EDG) in the amidinate complexes represents a logical antithesis. Interestingly, the fluorinated zirconium complex 32 showed no reactivity towards propylene at room temperature; however, at 60°C, the complex exhibits an impressive activity of 113 kg mol −1 h −1 (Table 1), yielding a viscid, atactic, low molecular weight polymer.…”