| Abstrakt: |
Nucleophilic ring opening of the 1-oxa-3,5-diazinium salts 2 and 3 by propylamine furnishes the new polydentate, branched, pincer-type ligands 4 and 5, respectively, in 34 and 57 % yield. The 1-oxa-3,5-diazinium salts 2 and 3 were prepared from pyridine-2,6-dicarbonyl dichloride (1) by treatment with dimethylcyanamide and diisopropylcyanamide in the presence of antimony pentachloride and tin tetrachloride, respectively. The structure of 4, which is characterised by a strongly twisted N-acyloligonitrile arm, was determined by X-ray crystallography. The ligand 4, with its short and long arms, forms chelate complexes 4–·Pd(OAc)+ and 4·CuCl2when treated with palladium(II) acetate and copper(II) chloride, respectively. 4–·Pd(OAc)+ shows remarkable catalytic activity in Suzuki–Miyaura cross-coupling reactions. The pincer-type ligand 5 gives the chelate complexes 5·Co(ClO4)2·DMF, 5·CoCl2 and 5·Ni(ClO4)2·DMF upon treatment with the respective metal salts. These three complexes show octahedral configuration, with DMF or chloride occuping the sixth coordination site. For the CoII complexes a cis configuration is oberserved for 5·CoCl2and a trans configuration for 5·Co(ClO4)2·DMF. In all cases 5 acts as a pentadentate ligand. All metal complexes were characterised by X-ray diffraction. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) |
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