Synthese und Struktur zweikerniger Kupfer(II)‐Komplexe eines neuen Hexaaza‐Makrocyclus mit verbrückenden Oxalat‐ und Acetat‐Ionen

Synthesis and Structure of Dinuclear Copper(II) Complexes of a Novel Hexaaza Macrocycle Containing Bridging Oxalate and Acetate Ions Non‐template Schiff base [2 + 2] condensation of pyridine‐2,6‐dicarbaldehyde with 1,4‐diamino‐2‐butyne yields the hexaazamacrocyclic ligand 1 , which is converted to 2 by NaBH 4 reduction of the imino groups. Two dinuclear copper(II) complexes of 2 containing oxalate and acetate ions, [( 2 )Cu 2 (μ‐C 2 O 4 )](BPh 4 ) 2 ( 3 ) and [( 2 )Cu 2 (μ‐CH 3 CO 2 )(OH 2 )](PF 6 )   2.25   −(NO 3 ) 0.75 ( 4 ), were characterized by X‐ray crystallography. The oxalate ligand in 3 forms a (μ‐η 4 :η 4 ) bridge between the copper atoms. Compound 4 contains a syn‐anti ‐bridging acetate ion. The Cu‐Cu distances are 5.315 Å in 3 and 4.746 Å in 4 , respectively. Oxalate can be separated from other carboxylates in aqueous solution by selective binding to the [( 2 )Cu 2 ] unit and precipitation of 3 .