1575626-06-0Relevant articles and documents
Synthesis and characterization of oxygen-functionalised-NHC silver(i) complexes and NHC transmetallation to nickel(ii)
Hameury, Sophie,De Fremont, Pierre,Breuil, Pierre-Alain R.,Olivier-Bourbigou, Helene,Braunstein, Pierre
, p. 4700 - 4710 (2014)
The new alcohol- and ether-functionalised-NHC silver(i) complexes bis(1-(2,6-diisopropylphenyl)-3-(2-hydroxyethyl)-1H-imidazol-2(3H)-ylidene) silver(i) chloride, [Ag{ImDiPP(C2OH)}2]Cl (4), bis(1-(2-hydroxyethyl)-3-mesityl-1H-imidazol-2(3H)-ylidene)silver(i) chloride, [Ag{ImMes(C2OH)}2]Cl (5), bis(1-(2-hydroxyethyl)-3-methyl- 1H-imidazol-2(3H)-ylidene)silver(i) chloride, [Ag{ImMe(C2OH)} 2]Cl (6), bis(1-(2,6-diisopropylphenyl)-3-(2-hydroxyethyl)-1H- imidazol-2(3H)-ylidene)silver(i) tetrafluoroborate, [Ag{ImDiPP(C 2OH)}2]BF4 (9), and bis(1-(2,6- diisopropylphenyl)-3-(2-methoxyethyl)-1H-imidazol-2(3H)-ylidene)silver(i) chloride, [Ag{ImDiPP(C2OMe)}2]Cl (13), were synthesized and fully characterized by NMR spectroscopy and single crystal X-ray diffraction. For some complexes, an uncommon heteronuclear coupling 4J(107/109Ag-H) was unveiled. Their ability to transfer the NHC ligand to Ni(ii) was assessed in the presence of different nickel(ii) sources; the bis-NHC Ni(ii) complex bis(1-(2,6-diisopropylphenyl)-3-(2- methoxyethyl)-1H-imidazol-2(3H)-ylidene)nickel(ii) chloride, [NiCl 2{ImDiPP(C2OMe)}2] (15), was obtained from 13 and shown by X-ray diffraction study to have a trans-arrangement of the two NHC ligands. However, in contrast to other Ag(i) NHC complexes the transmetallation reaction failed with the hydroxyl-functionalised silver complexes, possibly due to the acidity of the alcohol OH function, leading overall to reprotonation of the CNHC and isolation of the corresponding imidazolium salts.
Controlled ring-opening polymerization of trimethylene carbonate and access to PTMC-PLA block copolymers mediated by well-defined N-heterocyclic carbene zinc alkoxides
Fliedel, Christophe,Mameri, Samir,Dagorne, Samuel,Aviles, Teresa
, p. 504 - 511 (2014)
Four novel Zinc-NHC alkyl/alkoxide/chloride complexes (4, 5, 9 and 9) were readily prepared and fully characterized, including X-ray diffraction crystallography for 5 and 9. The reaction of N-methyl-N-butyl imidazolium chloride (3.HCl) with ZnEt2 (2 equiv.) afforded the corresponding [(CNHC)ZnCl(Et)] complex (4) via a protonolysis reaction, as deduced from NMR data. The alcoholysis of 4 with BnOH led to quantitative formation of the dinuclear Zn(II) alkoxide species [(CNHC)ZnCl(OBn)]2 (5), as confirmed by X-ray diffraction analysis. The NMR data are in agreement with species 5 retaining its dimeric structure in solution at room temperature. The protonolysis reaction of N-(2,6-diisopropylphenyl)-N-ethyl methyl ether imidazolium chloride (8.HCl) with ZnEt2 (2 equiv.) yielded the [(CNHC)ZnCl(Et)] species 9. The latter was found to be reactive with CH2Cl2 in solution and to cleanly convert to the corresponding Zn(II) dichloride [(CNHC)ZnCl2]2 (9), whose molecular structure was also elucidated using X-ray diffractometry. Unlike Zn(II)-NHC alkoxide species 1 and 2, which contain a NHC flanked with an additional N-functional group (i.e. thioether and ether, respectively), the Zn(II) alkoxide species 5 incorporates a monodentate NHC ligand. The Zn(II) complexes 1, 2 and 5 were tested in the ring-opening polymerization (ROP) of trimethylene carbonate (TMC). All three species are effective initiators for the controlled ROP of trimethylene carbonate, resulting in the production of narrow disperse PTMC material. Initiator 1 (incorporating a thioether moiety) was found to perform best in the ROP of TMC. Notably, the latter also readily undergoes the sequential ROP of TMC and rac-LA in the presence of a chain-transfer agent, leading to well-defined and high-molecular-weight PTMC/PLA block copolymers. Copyright
