Synthesis and X-ray structural characterization of sterically hindered bis(3,5-di-tert-butylsalicylaldiminato)Cu(II) complexes
摘要:
Bis(3,5-di-tert-butylsalicylaldiminato)Cu(II) complexes were prepared in high yields from a sterically hindered 3,5-di-tert-butylsalicylaldehyde and a variety of amines using three synthetic approaches. They were all thoroughly characterized by various spectroscopic methods (UV-Vis, IR, EPR and EI-MS). Crystal structures of seven complexes determined by X-ray crystallography show the Cu ion in a N2O2 coordination environment and a tetrahedrally distorted square-planar geometry. The UV-Vis and EPR results indicated that the complexes have the same geometry also in solution. In two solid state structures of the complexes the ligands have obtained an unusual cis-orientation whereas the rest of the complexes are trans-isomers. Computational studies carried out by the density functional theory method verified that in the case of complex with N-alkyl fragment the preferred isomer is trans, while the opposite behavior is observed for the complex with N-phenyl substituent. (C) 2012 Elsevier Ltd. All rights reserved.
Efficient coupling of CO2 and epoxides with bis(phenoxyiminato) cobalt(III)/Lewis base catalysts
作者:Ahlam Sibaouih、Paul Ryan、Kirill V. Axenov、Markku R. Sundberg、Markku Leskelä、Timo Repo
DOI:10.1016/j.molcata.2009.07.009
日期:2009.10
A series of unbridged bis(phenoxyiminato) cobalt(III)complexes were synthesized and studied as catalysts for the coupling of CO2 and epoxide. Dimethylamino pyridine (DMAP) and tetrabutyl ammonium bromide (Bu4NBr). were used as co-catalysts in the reaction. Both Co(III)/DMAP and Co(III)/Bu4NBr systems showed high catalytic activity and selectivity in the Coupling of n-hexyl oxide and CO2, resulting in n-hexyl carbonate. Several mono- and di-substituted terminal epoxides were also tested. The reaction mechanism of the Co(III)/DMAP system was investigated in detail using ESI-MS revealing that in addition to the main product, cyclic carbonate, traces of oligomers are formed. (C) 2009 Elsevier B.V. All rights reserved.
A facile synthesis of mixed ligand Cu(II) complexes with salicylaldehyde and salicylaldimine ligands and their X-ray structural characterization
作者:Jahir Uddin Ahmad、Minna T. Räisänen、Martin Nieger、Markku Leskelä、Timo Repo
DOI:10.1016/j.ica.2011.12.009
日期:2012.4
High yield synthetic routes to the preparation of new mixed ligand Cu(II) complexes (1-7) derived from a sterically hindered salicylaldimine and the corresponding salicylaldehyde have been developed. The complexes could be obtained either forming a salicylaldimine preligand or two optional Cu(II) complex precursors. One-pot synthesis could also be used. The complexes have been fully characterized by means of elemental analysis, UV-Vis and IR spectroscopy. Crystal structures obtained for four [(3,5-di-tert-butylsalicylaldehydato)(N-R-3,5-di-tert-butylsalicylaldiminato)]Cu(II) (where R = phenyl (1), isopropyl (3), benzyl (5) and 2-phenylethyl (6)) complexes show that three of them are cis-isomers and one is a trans-isomer with respect to the phenolic O-atoms. Complexes 1, 5 and 6 form preferably loose dimers while 3 favors to exist in a loose polymeric structure in a crystal. In all these polynuclear forms the geometry around the Cu(II) ions is a distorted octahedron. (C) 2011 Elsevier B. V. All rights reserved.