Group 4 Complexes with Aminebisphenolate Ligands and Their Application for the Ring Opening Polymerization of Cyclic Esters

Abstract

A series of tetradentate amine(bisphenolate) ligands have been synthesized and complexed to Ti(IV), Zr(IV), and Hf(IV) centers. Two distinct ligand sets have been synthesized both exhibiting ONNO coordination. The steric bulk of the ligands was varied to assess the impact of sterics on the catalytic performance in the ring-opening-polymerization (ROP) of cyclic esters. In all cases the metal centers are pseudo octahedral in geometry. Several group 4 amine(bisphenolate) complexes have been characterized by single-crystal X-ray diffraction. The complexes were tested for the ROP of ε-caprolactone and L/rac-lactide, with significant activity seen for complexes of all group 4 metals. For Ti(IV), complexes of sterically demanding ligands were more effective initiators, whereas sterically less demanding ligands were more successful for Zr(IV) complexes. Copolymers of poly(ε-caprolactone) and poly-l-lactide were produced utilizing the Zr(IV) initiators. The polymerization of rac-lactide was also studied allowing stereoselectivity of a range of metal−ligand combinations to be assessed. Isotactic polymer was produced with both Zr(IV) and Hf(IV) centers whereas Ti(IV) produced an atactic polymer.

Synthesis, Characterization, Cytotoxicity, and Hydrolytic Behavior of C2‐ and C1‐Symmetrical TiIV Complexes of Tetradentate Diamine Bis(Phenolato) Ligands: A New Class of Antitumor Agents

“…[17] The complexes [Ti( -5) were prepared in quantitative yields according to a highly convenient, published procedure from the ligand precursors H 2 L n (n = 1-5) and [TiA C H T U N G T R E N N U N G (OiPr) 4 ] at room temperature in diethyl ether or THF. [33,[35][36][37] The ligands were all synthesized by a single-step Mannich condensation from the substituted phenol, formaldehyde, and the N,N'-disubstituted diamine. [38] As we recently communicated, [33] the X-ray structure of [Ti( Table 1) indicates a C 2 -symmetrical complex with two cis isopropoxo groups and with the phenolato groups in a trans configuration, similar to other known compounds of this class.…”

“…[38] As we recently communicated, [33] the X-ray structure of [Ti( Table 1) indicates a C 2 -symmetrical complex with two cis isopropoxo groups and with the phenolato groups in a trans configuration, similar to other known compounds of this class. [36,37,39,40] 2 ] was also crystallized from diethyl ether by slow evaporation at room temperature and the X-ray structure ( Figure 2; Table 2) reveals a similar general geometry of a C 2 -symmetrical complex with two cis isopropoxo groups and a trans configuration of the phenolato oxygen donors. 2 ] was crystallized from diethyl ether at À358 C www.chemeurj.org and its X-ray structure ( Figure 3; Table 3) again shows a C 2 -symmetrical complex with two cis isopropoxo groups and two trans phenolato donors, which is of very high structural similarity to its dimethyl analogue [Ti(L .…”

Anticancer Metal Complexes: Synthesis and Cytotoxicity Evaluation by the MTT Assay

“…The complexes were prepared based on established procedures 18,28 and their purity may be evaluated by NMR and elemental analysis.…”

Preparation and characterization of TAMP/TIMP-Ti and Zr compounds and their catalytic activity over propylene oxide and Ɛ-caprolactone

“…However, as can be seen in Figure 6, the GPC chromatogram of the PO polymer prepared at 75 °C with Ti-TAMP showed bimodal molecular weight distribution. The first peak in Figure 6 has weight average molecular weight Transition metal compounds carry out ROP of ε-CL and PO via a coordination-insertion mechanism [26][27][28][29][30][31][32][33]. For example, the polymerization mechanism of ε-CL can be shown in …”