Complexation to FeII, NiII, and ZnII of Multidentate Ligands Resulting from Condensation of 2-Pyridinecarboxaldehyde with 详细信息    查看全文

• 作者：Nicolas Bré ; fuel ; Christine Lepetit ; Sergiu Shova ; Franç ; oise Dahan ; and Jean-Pierre Tuchagues
• 刊名：Inorganic Chemistry
• 出版年：2005
• 出版时间：November 28, 2005
• 年：2005
• 卷：44
• 期：24
• 页码：8916 - 8928
• 全文大小：239K
• 年卷期：v.44,no.24(November 28, 2005)
• ISSN：1520-510X

文摘

The condensation reaction between 2-pyridinecarboxaldehyde and diethylenetriamine, 3-[(2-aminoethyl)amino]propylamine, and 3,3'-iminobis(propylamine) in a 2:1 molar ratio yields ligands that may be isolated exclusively inthe dissymmetric (cyclic) isomeric forms L^A, L^B/L^B*, and L^C. The template effect of a metal center (Fe^II, Ni^II,and Zn^II)results in the ring opening of L^C including one hexahydropyrimidine ring and one (long) propylene bridge. Theresulting symmetric bis-Schiff base isomeric form L^C' is stabilized through pentacoordination, yielding [Fe^IIL^C'(NCS)](NCS) (3), [Ni^IIL^C'(NCS)](NCS) (6), and [Zn^IIL^C'(NCS)](NCS) (9). The same metal centers are too bulky to exert atemplate effect on L^A including one imidazolidine ring and one (short) ethylene bridge. L^A acts as a tetradentateligand yielding [Fe^IIL^A(NCS)₂] (1), [Ni^IIL^A(NCS)₂] (4), and [Zn^IIL^A(NCS)₂] (7). The template effect of the metal centeris selective toward the ligand L^B/L^B* including a hexahydropyrimidine (imidazolidine) ring and the shorter ethylene(longer propylene) bridge. The Fe^II cation is small enough to exert a template effect, resulting in the ring openingof L^B/L^B*. The resulting bis-Schiff base L^B' is stabilized through pentacoordination, yielding [Fe^IIL^B'(NCS)](NCS) (2).Ni^II is too bulky to promote the ring opening of L^B/L^B*: L^B acts as a tetradentate ligand, yielding [Ni^IIL^B(NCS)₂] (5)(the L^B* isomer is totally converted to L^B). The coordinative requirements and stereochemical preference of thebulkier Zn^II cation allow neither the ring opening of L^B/L^B* nor the tetracoordination of L^B or L^B* but stabilize thenovel tetradentate dissymmetric form L^B in [Zn^IIL^B(NCS)₂]·H₂O (8) (L^B results from MeOH addition across theimine bond of L^B). Density functional theory calculations performed for Ni^II and Zn^II complexes of the L^B/L^B*/L^B setof ligands allowed one to compare the relative stabilities of all possible isomers, showing that the most stable onescorrespond to those experimentally obtained: isomerization, or methanol addition across the imine bond, of thetetradentate ligand depends on the relative stabilities of all possible isomeric complexes.