Synthesis and catalytic application of aluminium anilido-pyrazolate complexes

Abstract

A series of aluminium complexes containing anilido-pyrazolate ligands is described. Reactions of four anilido-pyrazolate ligand precursors, HNPhPz, HNPhTriMePz, HNPhOMePz, or HNPhSMePz [HNPhPz = ortho-C6H4(NH-phenyl)(1-pyrazole); HNPhTriMePz = ortho-C6H4(NH-2,4,6-trimethylphenyl)(1-pyrazole); HNPhOMePz = ortho-C6H4(NH-2-methoxyphenyl)(1-pyrazole); HNPhSMePz = ortho-C6H4(NH-2-methylthiophenyl)(1-pyrazole)], with one molar equivalent of AlMe3 in toluene give the aluminium dimethyl complexes, (NArPz)AlMe2 [Ar = phenyl, (NPhPz)AlMe2 (1); Ar = 2,4,6-trimethylphenyl, (NPhTriMePz)AlMe2 (2); Ar = 2-methoxyphenyl, (NPhOMePz)AlMe2 (3); Ar = 2-methylthiophenyl, (NPhSMePz)AlMe2 (4)], respectively. The molecular structures are reported for compounds 1 and 3. Their catalytic activities toward the ring opening polymerisation reaction of -caprolactone in the presence of BnOH are also under investigation.

Ring-opening polymerization of rac-lactide using anilinotropone-based aluminum complexes-sidearm effect on the catalysis

“…Very interestingly, salicylaldiminato aluminum complex A is not active at all under the above conditions ( It was proposed previously that the protonation process may proceed through the release of ligand precursors instead of the substitution of methyl with benzyl alkoxide group [40,41].…”

“…Crystal Data for C 42 H40 Al 2 N 2 O 4 (M =690.72): triclinic, space group P-1 (no. 2), a = 8.6503(7) Å, b = 10.1063(8) Å, c = 12.3226(6) Å, α = 74.459(5)°, β = 83.768(5)°, γ = 64.835(8)°, V = 939.36(13) Å 3 , Z = 1, T = 291(2) K, μ(MoKα) = 0.121 mm -1 , Dcalc = 1.221 g/mm 3 , 7129 reflections measured (6.252 ≤ 2Θ ≤ 52.744), 3846 unique (R int = 0.0187, R sigma = 0.0341) which were used in all calculations.…”

An unprecedented transformation mode in aluminium oxazoline‐amido‐phenolate complexes

“…This led us to investigate ligand precursors bearing similar chelating systems related to β‐diketiminate ligands. In our previous studies of anilido‐oxazolinate systems[6k, 6o, 7] or anilido‐pyrazolate system, their catalytic activities were displayed with different metal centers, including Mg, Al and Zn, and played roles as efficient initiators/catalysts in ROP. In the work reported in this paper, we aimed at aluminium pendant oxazoline‐amido‐phenolate complexes, which exhibited different coordination modes as depicted in Figure .…”

Reactions of 4-methylidene-bis(1-phenyl-3-methylpyrazol-5-one) with trimethylaluminum: Synthesis, structure and catalysis for the ring-opening polymerization of ε-caprolactone

“…Based on lactone polymerizations catalyzed with dimethyl (salicylaldiminato)-aluminum [18], aluminum anilido-oxazolinate [19] Scheme 1. Synthetic routes for complexes 1 and 2. or anilido-pyrazolate complexes [20], mono-adduct Al methyl complex 1 was expected to behave as a catalyst toward the ROP of ε-CL in the presence of alcohol. In this context, polymerizations were performed in toluene with the catalyst, monomers, and 9-anthracenemethanol (9-AnOH) at prescribed equivalent ratios for a particular duration.…”