Copper(II)- and Proton-Assisted Condensation Reactions of a Tetrapodal Pentaamine with Acetone: Formation of “Podand-cum-Macrocycle” Copper Complexes and a Protonated Bis(aminal)
✍ Scribed by Christopher Zimmermann; Frank W. Heinemann; Andreas Grohmann
- Publisher
- John Wiley and Sons
- Year
- 2001
- Tongue
- English
- Weight
- 384 KB
- Volume
- 2001
- Category
- Article
- ISSN
- 1434-1948
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✦ Synopsis
N ligands / Copper / Template synthesis / Schiff bases / Macrocycles The tetrapodal pentaamine 2,6-C 5 H 3 N[CMe(CH 2 NH 2 ) 2 ] 2 (pyN 4 , 1) forms mononuclear complexes with Cu II , as shown for a series of compounds of the type [( )Cu]X 2 (X = Br, SCN, PF 6 , ClO 4 ). The coordination environment of the copper ion is square-pyramidal, with the pyridine nitrogen atom of 1 in the apical position. The axial bond Cu-N py is significantly longer than the four Cu-N bonds at the base of the pyramid, average values being 2.16 A ˚and 2.03 A ˚, respectively. When [( )Cu]X 2 (X = PF 6 , ClO 4 ) is refluxed with an excess of acetone in methanol in the absence of base, the corresponding bis(isopropylideneimine) complexes [{(nac) 2 pyN 4 }Cu]X 2 are obtained, in which two diametrically opposite primary amino groups of 1 have condensed with the ketone. The complex cations, which are now chiral, again have square-pyramidal coordinated Cu II . In the presence of sodium methoxide, the condensation of [( )Cu]X 2 with acetone proceeds further, leading to the formation of one diacetone-amine-imine linkage in the product. A 12-membered 1,5,9-triazamacrocycle,