Ring‐opening polymerization of cyclic esters promoted by phosphido‐diphosphine pincer group 3 complexes

Abstract

Phosphido-diphosphine Group 3 metal complexes\ud 1–4 [(o-C6H4PR2)2P-M(CH2SiMe3)2; R ¼ Ph, 1: M ¼ Y, 2: M ¼ Sc;\ud R ¼ iPr, 3: M ¼ Y, 4: M ¼ Sc] are very efficient catalysts for\ud the ring-opening polymerization (ROP) of cyclic esters such as\ud e-caprolactone (e-CL), L-lactide, and d-valerolactone under mild\ud polymerization conditions. In the ROP of e-CL, complexes 1–4\ud promote quantitative conversion of high amount of monomer\ud (up to 3000 equiv) with very high turnover frequencies (TOF)\ud (4 104 molCL/molI h) showing a catalytic activity among the\ud highest reported in the literature. The immortal and living ROP\ud of e-CL and L-lactide is feasible by combining complexes 1–4\ud with 5 equiv of 2-propanol. Polymers with controlled molecular\ud parameters (Mn, end groups) and low polydispersities (Mw/Mn\ud ¼ 1.05–1.09) are formed as a result of fast alkoxide/alcohol\ud exchange. In the ROP of d-valerolactone, complexes 1–4\ud showed the same activity observed for lactide (L- and D,L-lactide)\ud producing high molecular weight polymers with narrow\ud distribution of molar masses. Complexes 1–4 also promote the\ud ROP of rac-b butyrolactone affording atactic low molecular\ud weight poly(hydroxybutyrate) bearing unsaturated end groups\ud probably generated by elimination reaction

Coordination Chemistry and Reactivity of Zinc Complexes Supported by a Phosphido Pincer Ligand

“…On the other hand, variable-temperature 31 P NMR spectra, accumulated in the same temperature range, showed that the signal of neutral phosphorus donors progressively loses its multiplicity and appears as a broad peak at À60 8C, while the peak of the phosphido ligand preserves its multiplicity. Thus, the low-temperature NMR experiments lean towards the hypothesis that a fluxional process is active affording a C s -symmetric species on the NMR timescale.…”

“…Removal of the volatile materials under reduced pressure gave pale yellow solids, which were washed with a minimum amount of cold hexane to obtain analytically pure 1 (83 % yield) and 2 (91 % yield). Complexes 1 and 2 were characterized by multinuclear and two-dimensional NMR spectroscopy [36] ( 1 H, 13 C, 31 P NMR and COSY experiments) and elemental analysis.…”

“…These results indicated that ancillary ligands incorporating soft donors are a valid option in the development of efficient early transition metal based polymerization catalysts. [30,31] Since phosphine derivatives of group 12 metals are quite rare, we decided to extend the use of this class of ligands to the coordination chemistry of zinc. Some examples of crystallographically characterized zinc complexes were reported by Darensbourg et al [32] and more recently by Liang et al [33,34] In all cases phosphine donors are in combination with hard phenoxide or amide additional donors.…”

Synthesis and Structure of Lanthanide Aryloxo Complexes and Their Polymerization Behavior for ϵ‐Caprolactone

“…[26][27][28][29] It has been found that many organolanthanide complexes are efficient initiators for the ring-opening polymeriza- tion (ROP) of ε-caprolactone. [20][21][22][30][31][32] To further explore the influence of the initiating group of organolanthanide complexes on the catalytic property, the catalytic behaviors of complexes 1-6 for the ROP of ε-caprolactone were tested (Scheme 2), and the results are listed in Table 3.…”

Catalyst‐Free Ring Opening Synthesis of Biodegradable Poly(ester‐urethane)s Using Isosorbide Bio‐Based Initiator

“…The ROP of ε‐caprolactone has been performed using different models of catalytic or coinitiator systems. The polycaprolactone can be produced by using metallic catalysts such as aluminum amido complexes, Tin octoate, and rare earth metal derivatives …”