Synthesis, characterization of a novel zinc diamine–bisphenolate complex and its application as an initiator for ring-opening polymerization of rac-lactide

Dong, Qingchen; Ma, Xiaping; Guo, Jianping; Wei, Xuehong; Zhou, Min; Liu, Dian‐Sheng

doi:10.1016/j.inoche.2008.02.011

Cited by 18 publications

(6 citation statements)

References 29 publications

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“…Unlike the dinuclear white complexes [Fe(salan X )] 2 , this complex is highly soluble, even in nonpolar solvents, such as pentane. The structure of this iron(II) complex is presumed to be tetrahedral, similar to the tetrahedral iron(II) complexes with bidentate salicylaldimine ligands , and the analogous tetrahedral zinc(II) complex [Zn(salan t Bu, t Bu )], which was recently reported . The reaction of H 2 salan t Bu, t Bu with two equivalents of KH results in the dipotassium salt K 2 salan t Bu, t Bu , which can subsequently be reacted with FeCl 2 in THF to give the complex [Fe(salan t Bu, t Bu )(THF) 2 ] (Scheme ).…”

Section: Resultsmentioning

confidence: 77%

Iron(II) Complexes with Tetradentate Bis(aminophenolate) Ligands: Synthesis and Characterization, Solution Behavior, and Reactivity with O₂

et al. 2010

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Tetradentate bis(aminophenolate) ligands H(2)salan(X) and H(2)bapen(X) (where X refers to the para-phenolate substituent = H, Me, F, Cl) react with [Fe{N(SiMe(3))(2)}(2)] to form iron(II) complexes, which in the presence of suitable donor ligands L (L = pyridine or THF) can be isolated as the complexes [Fe(salan(X))(L)(2)] and [Fe(bapen(X))(L)(2)]. In the absence of donor ligands, either mononuclear complexes, for example, [Fe(salan(tBu,tBu))], or dinuclear complexes of the type [Fe(salan(X))](2) are obtained. The dynamic coordination behavior in solution of the complexes [Fe(salan(F))(L)(2)] and [Fe(bapen(F))(L)(2)] has been investigated by VT (1)H and (19)F NMR spectroscopy, which has revealed equilibria between isomers with different ligand coordination topologies cis-α, cis-β and trans. Exposure of the iron(II) salan(X) complexes to O(2) results in the formation of oxo-bridged iron(III) complexes of the type [{Fe(salan(X))}(2)(μ-O)] or [{Fe(salan(X))(L)}(2)(μ-O)]. The lack of catalytic activity of the iron(II) salan and bapen complexes in the oxidation of cyclohexane with H(2)O(2) as the oxidant is attributed to the rapid formation of stable and catalytically inactive oxo-bridged iron(III) complexes.

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Section: Resultsmentioning

confidence: 77%

Iron(II) Complexes with Tetradentate Bis(aminophenolate) Ligands: Synthesis and Characterization, Solution Behavior, and Reactivity with O₂

et al. 2010

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“…Salan zinc complexes have been explored to a lesser extent 27. Nonbulky Salans tend to adopt a bridging dinuclear structure28 but adding a bulky substituent at the ortho ‐position of the phenolato group leads to mononuclear tetrahedral complexes 27a,29. Relevant to the present work, enantioselective aryl transfer to aldehydes with catalytic bipyrrolidine‐based Salans19 in the presence of a large excess of diethylzinc was recently reported 30.…”

Section: Introductionmentioning

confidence: 64%

Zinc Complexes of Bipyrrolidine‐Based Diamine‐Diphenolato and Diamine‐Diolato Ligands: Predetermination of Helical Chirality Around Tetrahedral Centres

et al. 2013

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The coordination chemistry of chiral tetradentate dianionic ligands of the diamine-diphenolato and diamine-diolato families having the (R,R)-2,2Ј-bipyrrolidine core around Zn II was investigated. Reactions with diethylzinc led to complexes of the type [{ONNO}Zn] for most ligands and to bridging dinuclear complexes of the type [μ-Lig 4 (ZnEt) 2 ] for one of the diamine-diolato ligands. Reactions with bis(hexamethyldisilazide)zinc led to complete conversions. Most complexes were obtained as mononuclear complexes. The least bulky Salan ligand, Lig 3 , led to an equilibrium between mononuclear and dinuclear complexes in noncoordinating solvents. All ligands [a]

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“…20 The range of supporting ligands reported for these complexes include amidinate, 21 ketiminate 22 and b-diiminate, [23][24][25][26][27][28][29][30][31] Salen type ligands, 32,33 pyrazolyl derived scorpionates, 31,34-36 oxazolinate, 37 and phenolates. [38][39][40][41] Of the reported zinc-NHC complexes, 42-46 only a few have been applied to lactide polymerisation. Tolman and Hillmeyer reported substituted zinc-NHC complexes, A-D in Fig.…”

Section: Introductionmentioning

confidence: 99%

Magnesium and zinc complexes of functionalised, saturated N-heterocyclic carbene ligands: carbene lability and functionalisation, and lactide polymerisation catalysis

et al. 2009

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The synthesis of magnesium and zinc complexes of bidentate anionic alkoxide ligands with saturated-backbone carbene groups is reported. Mono(ligand) and bis(ligand) complexes [M(L(R))N''](2) and [M(L(R))(2)] (M = Mg, Zn, N'' = N(SiMe(3))(2), L(R) = [OCMe(2)CH(2){CNCH(2)CH(2)NR}] R = (i)Pr, Mes, Dipp) have been isolated, and some structurally characterised and compared with the new unsaturated carbene complex [Mg(L)(2)]. Reactions with silyl halides show either addition across the metal carbene bond, or across the metal alkoxide bond, in accordance with the metals' electronegativity difference: the metal alkoxide bonds are stronger for Mg(II) complexes, for which the carbene is silylated to form zwitterionic [MgI(Me(3)SiL(R))N''] (Me(3)SiL(R) = OCMe(2)CH(2){Me(3)SiCNCH(2)CH(2)NR}) while the metal-bound alkoxide group is silylated in the Zn(II) complexes forming [ZnI(Me(3)SiOL(R))N''] (Me(3)SiOL(R) = Me(3)SiOCMe(2)CH(2){CNCH(2)CH(2)NR}). The proligand [HL(R)] is silylated at the alcohol group, forming the iodide salt [Me(3)SiOCMe(2)CH(2){HCNCH(2)CH(2)NR}]I.Preliminary results on the use of these complexes as initiators for the polymerisation of rac-lactide are reported, and suggest different initiation mechanisms are occurring for the two metals, in agreement with the different silylation reactivity observed. The polymerisation reactions are facile at room temperature even without an initiator, and yield polymers of reasonable molecular weight and heterotacticity and with good PDI. These are the first magnesium NHC complexes demonstrated to effect lactide polymerisation.Also, an adduct instead of the anticipated potassium alkoxycarbene is generated from the reaction of the proligand [HL(R)] with potassium amide KN''; this has been structurally characterised.

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Synthesis, characterization of a novel zinc diamine–bisphenolate complex and its application as an initiator for ring-opening polymerization of rac-lactide

Cited by 18 publications

References 29 publications

Iron(II) Complexes with Tetradentate Bis(aminophenolate) Ligands: Synthesis and Characterization, Solution Behavior, and Reactivity with O₂

Iron(II) Complexes with Tetradentate Bis(aminophenolate) Ligands: Synthesis and Characterization, Solution Behavior, and Reactivity with O₂

Zinc Complexes of Bipyrrolidine‐Based Diamine‐Diphenolato and Diamine‐Diolato Ligands: Predetermination of Helical Chirality Around Tetrahedral Centres

Magnesium and zinc complexes of functionalised, saturated N-heterocyclic carbene ligands: carbene lability and functionalisation, and lactide polymerisation catalysis

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Synthesis, characterization of a novel zinc diamine–bisphenolate complex and its application as an initiator for ring-opening polymerization of rac-lactide

Cited by 18 publications

References 29 publications

Iron(II) Complexes with Tetradentate Bis(aminophenolate) Ligands: Synthesis and Characterization, Solution Behavior, and Reactivity with O2

Iron(II) Complexes with Tetradentate Bis(aminophenolate) Ligands: Synthesis and Characterization, Solution Behavior, and Reactivity with O2

Zinc Complexes of Bipyrrolidine‐Based Diamine‐Diphenolato and Diamine‐Diolato Ligands: Predetermination of Helical Chirality Around Tetrahedral Centres

Magnesium and zinc complexes of functionalised, saturated N-heterocyclic carbene ligands: carbene lability and functionalisation, and lactide polymerisation catalysis

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Iron(II) Complexes with Tetradentate Bis(aminophenolate) Ligands: Synthesis and Characterization, Solution Behavior, and Reactivity with O₂

Iron(II) Complexes with Tetradentate Bis(aminophenolate) Ligands: Synthesis and Characterization, Solution Behavior, and Reactivity with O₂