Chi-Tien Chen

Aluminium metal complexes supported by amine bis-phenolate ligands as catalysts for ring-opening polymerization of ε-caprolactone

A family of aluminium complexes supported by dianionic amine bis(phenolate) ligands are described. Treatment of ligand precursors H2O2NNPy or H2O2NNMe [H2O2NNPy = (2-C5H4N)CH2N(CH2-2-HO-3,5-C6H2(tBu)2)2; H2O2NNMe = Me2NCH2CH2N(CH2-2-HO-3,5-C6H2(tBu)2)2] with 1.1 molar equivalent of AlMe3 in toluene affords MeAl(O2NNPy) (1) and MeAl(O2NNMe) (2) as five-coordinate aluminium methyl complexes, which further react with one equivalent of benzyl alcohol affording (C6H5CH2O)Al(O2NNPy) (3) and (C6H5CH2O)Al(O2NNMe) (4) as five-coordinate aluminium benzyloxy complexes. The molecular structures are reported for compounds 1 and 4. Compounds 3 and 4 show excellent catalytic activity toward the ring-opening polymerization of e-caprolactone.

Magnesium complexes containing bis-amido-oxazolinate ligands as efficient catalysts for ring opening polymerisation of L-lactide

A series of magnesium bis(amido-oxazolinate) complexes have been described. Reactions of six amido-oxazolinate ligand precursors, HNC(2)(Me)Oxa, HNC(2)(OMe)Oxa, HNC(2)(StBu)Oxa, HNPhOxa, HNPh(OMe)Oxa or HNPh(SMe)Oxa, with half molar equivalent of Mg(n)Bu(2) in hexane yield the magnesium bis(amido-oxazolinate) complexes, (NC(2)(E)Oxa)(2)Mg [C(2)(E) = propyl, (NC(2)(Me)Oxa)(2)Mg (1); C(2)(E) = 2-methoxyethyl, (NC(2)(OMe)Oxa)(2)Mg (2); C(2)(E) = 2-tert-butylthioethyl, (NC(2)(StBu)Oxa)(2)Mg (3)], or magnesium bis(anilido-oxazolinate) complexes, (NArOxa)(2)Mg [Ar = phenyl, (NPhOxa)(2)Mg (4); Ar = 2-methoxyphenyl, (NPh(OMe)Oxa)(2)Mg (5); Ar = 2-methylthiophenyl, (NPh(SMe)Oxa)(2)Mg (6)], respectively. The molecular structures are reported for compounds 1, 2, 5 and 6. Their catalytic activities toward the ring opening polymerisation of L-lactide in the presence of benzyl alcohol are also under investigation.

Synthesis and catalytic application of aluminium anilido-pyrazolate complexes

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.

Metal complexes containing nitrogen-heterocycle based aryloxide or arylamido derivatives as discrete catalysts for ring-opening polymerization of cyclic esters

The development of well-defined homogeneous catalysts for the ring-opening polymerization (ROP) of cyclic esters has made enormous progress over the past decade. This perspective focuses on some recent advances in the field of discrete metal complexes modified by various aryloxide or arylamido ligands bearing the nitrogen-containing heterocycle moiety, and their catalytic applications in ROP of lactones. It mainly highlights aryloxide/arylamido ligands that are directly installed by the N-heterocyclic group. The complex structure-ROP performance relationships and the observed trends with respect to their catalytic efficiency affected by ligand modifications are also discussed.

Palladacyclic complexes bearing CNN-type ligands as catalysts in the Heck reaction

Preparations of novel unsymmetrical, tridentate nitrogen ligand precursors, PhN=C(CMe2)(NPh)C=N(CH2)2NMe2(1) and PhN=C(CMe2)(NPh)C=N(CH2)Py (2), are described. Treatment of 1 with 1 molar equiv. (COD)PdCl2 in the presence of NEt3 or with 1 molar equiv. Pd(OAc)2 affords orthometallated palladium(II) complexes, [PhN=C(CMe2)(N-eta1-Ph)C=N(CH2)2NMe2]PdX (X=Cl (3); X=OAc (4)), respectively. Compound can be yielded via the reaction of with an excess of LiCl in methanol. Treatment of with 1 molar equiv. of (COD)PdCl2, Pd(OAc)2 or Pd(TFA)2 affords orthometallated palladium(II) complexes, [PhN=C(CMe2)(N-eta1-Ph)C=NCH2Py]PdX (X=Cl (5); X=OAc (6); X=TFA (7)), respectively. The crystal and molecular structures are reported for compounds 2, 3, 5 and 6. The application of these novel palladacyclic complexes to the Heck reaction with aryl halide substrates was examined.

Synthesis and characterisation of aluminium and magnesium complexes supported by pendant oxalic amidinate ligands

Two pendant oxalic amidine compounds [C6H5NC{NH(CH2)2OMe}–C{NH(CH2)2OMe}NC6H5] (1) (oxam(OMe)2H2) and [C6H5NC{NH(CH2)2NMe2}–C{NH(CH2)2NMe2}NC6H5] (2) (oxam(NMe2)2H2) are described. Reactions of 1 or 2 with two molar equivalents of AlMe3 in toluene give the bimetallic complexes [(Me2)Al(oxam(OMe)2)Al(Me2)] (3) and [(Me2)Al(oxam(NMe2)2)Al(Me2)] (4), respectively. Treatment of 1 or 2 with two molar equivalents of MeMgBr in THF affords the bimetallic complexes [(Br)(THF)Mg(oxam(OMe)2)Mg(THF)(Br)] (5) and [(Br)(THF)Mg(oxam(NMe2)2)Mg(THF)(Br)] (6) respectively. The crystal and molecular structures are reported for compounds 1, 2, 3, 5 and 6.