Synthesis and Characterization of <i>β</i>‐Diketiminate Zinc Complexes

Schulz, Stephan; Eisenmann, Tamara; Bläser, Dieter; Boese, Roland

doi:10.1002/zaac.200801382

Cited by 27 publications

(10 citation statements)

References 60 publications

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“…26 The zinc atom is found in a distorted tetrahedral coordination geometry. Bond distances and angles are comparable to other alkoxide bridged zinc diketiminates (Table S1 †), [22][23][24]39,52,[54][55][56][57] but on the lower end of the range observed for Zn-N distances and the higher end for the N-Zn-N angle, indicating rather low steric pressure from the ligand despite the annulated aromatic ring. The orientation of the anthryl moieties in 5c is in agreement with π-stacking interactions: the anthryl moieties are nearly coplanar (angle between mean planes: 7°), with a slight offset Complex 5c proved to be a moderately active and controlled catalyst for the solution polymerization of rac-lactide (Table 1, Fig.…”

Section: Resultssupporting

confidence: 65%

Lactide polymerization catalyzed by Mg and Zn diketiminate complexes with flexible ligand frameworks

2014

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Diketimine ligands bearing N-benzyl, N-9-anthrylmethyl and N-mesitylmethyl substituents (nacnac(Bn)H, nacnac(An)H, and nacnac(Mes)H) were prepared from condensation of the amine with either acetyl acetone or its ethylene glycol monoketal. Chlorination with N-chlorosuccinimide in the 3-position yielded Clnacnac(Bn)H and Clnacnac(An)H. The ligands were reacted with Zn(TMSA)2 (TMSA = N(SiMe3)2) to yield nacnac(An)Zn(TMSA) and Clnacnac(Bn)Zn(TMSA). Protonation with isopropanol afforded nacnac(An)ZnOiPr and Clnacnac(Bn)ZnOiPr. Reaction of the diketimines with Mg(TMSA)2 afforded nacnac(An)Mg(TMSA), nacnac(Mes)Mg(TMSA), Clnacnac(Bn)Mg(TMSA) and Clnacnac(An)Mg(TMSA). Subsequent protonation with tert-butanol produced nacnac(Mes)MgOtBu and Clnacnac(Bn)MgOtBu, but only decomposition was observed with N-anthrylmethyl substituents. Most complexes were characterized by X-ray diffraction studies. TMSA complexes were monomeric and alkoxide complexes dimeric in the solid state. All alkoxide complexes, as well as nacnac(An)Mg(TMSA)/BnOH and Clnacnac(An)Mg(TMSA)/BnOH were moderately to highly active in rac-lactide polymerization (90% conversion in 30 s to 3 h). nacnac(An)ZnOiPr produced highly heterotactic polymers (P(r) = 0.90), Clnacnac(Bn)MgOtBu/BnOH produced slightly isotactic polymers at -30 °C (P(r) = 0.43), and all other catalysts produced atactic polymers with a slight heterotactic bias.

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Section: Resultssupporting

confidence: 65%

Lactide polymerization catalyzed by Mg and Zn diketiminate complexes with flexible ligand frameworks

2014

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“…2 crystallizes together with a toluene molecule in monoclinic space group P21/n, whereas 3 crystallizes without any additional solvent molecules in the space group P-1 The central bond lengths and bond angles within the Mesnacnac ligands in 2 and 3 are almost identical to those previously observed for 1 as well as LZnX (X = I, OMe, OEt, Oi-Pr) and L2Zn. [14] The Zn-N bond lengths of the Mesnacnac ligand (2: 2.0188( 14), 2.0121(14); 3: 1.9956(9), 2.0037(9) Å) are significantly shorter compared to the Zn-Ndmap bond length (2: 2.0979(14); 3: 2.0468(9) Å), as was expected due to the dative character of the latter one. Moreover, the increased Lewis acidity of the Zn atom in 3 compared to 2, which results from the more electronegative chlorine substituent, significantly influences the Zn-Ndmap bond length as was expected.…”

Section: Resultsmentioning

confidence: 99%

Reactivity of (β‐Diketiminato)zinc Hydride toward Lewis Bases, Heterocumulenes and Cyclohexene Oxide

et al. 2012

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The reaction of LZnH 1 (L = Mesnacnac = { [2,4,-N(Me)C)]2CH}) with 4-dimethylaminopyridine (dmap) yielded the Lewis acid-base adduct LZn(H)dmap 2, whereas LZn(Cl)dmap 3 was obtained from the equimolar reaction of LZnCl with dmap. In addition, reactions of 1 with tert-Butylcarbodiimide C(Nt-Bu)2 and tert-butylthioisocyanate t-BuNCS proceeded with insertion of the heterocumulene into the Zn-H bond and formation of [LZn(t-BuNC(H)Nt-Bu)] 4 and [LZn(t-BuNC(H)S)] 5, whereas 1 reacted with Me3SiN3 with elimination of Me3SiH and formation of [LZnN3]2 6. Moreover, the reaction of 1 with cyclohexene oxide (CHO) occurred with ring opening and formation of [LZnOCy]2 7. 2-7 were characterized by multinuclear NMR ( 1 H, 13 C) and IR spectroscopy, elemental analyses and by single crystal X-ray diffraction (2, 3, 6, 7).

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“…We became recently interested in β -diketiminate zinc halide complexes of the type MesnacnacZnX (Mesnacnac = [HC{C(Me)N(Mes)} 2 ], Mes = 2,4,6-Me 3 C 6 H 2 ; X = Cl, I) [8], which we believed to be suitable starting reagents for the synthesis of the corresponding low-valent complexes Zn 2 R 2 as well as the zinc hy-0932-0776 / 09 / 1100-1397 $ 06.00 c 2009 Verlag der Zeitschrift für Naturforschung, Tübingen · http://znaturforsch.com dride RZnH. Unfortunately, reactions with several reducing agents only resulted in the formation of ZnR 2 [9], whereas reduction of the comparable Dippsubstituted complex DippnacnacZnI (Dipp = 2,6-iPr 2 C 6 H 3 ) yielded Dippnacnac 2 Zn 2 [10].…”

Section: Introductionmentioning

confidence: 99%