Multivalent 1‐Oxa‐3,5,7‐triazahepta‐1,3,5‐trienes: Synthesis, Structural Properties and Metal Coordination

Nucleophilic ring opening of bis‐ and tris(1‐oxa‐3,5‐diazinium) salts 1 with n ‐propylamine leads to the bis‐ and tris(armed) oligonitrile derivatives 3 and 8 with secondary amino groups in the side chain. Alternatively, treatment of simple 1‐oxa‐3,5‐diazinium salts 2 with primary and secondary di‐ and triamines offers a convenient pathway for the synthesis of bis‐ and tris(armed) oligonitriles 4 , 5 and 7 . 2,6‐Diaminopyridine furnishes the new pincer‐type ligand 6 upon reaction with 1‐oxa‐3,5‐diazinium salt 2a . Multivalent oligonitriles 4 , 6 , 7 and 8 containing secondary amino groups are able to form intra‐ and intermolecular hydrogen bonds in the solid state as detected by X‐ray crystallography. The oligonitriles 3a , b , 4b , d , h , 6 and 7a form coordination complexes with various Zn II , Cu II , Co II , Ni II and Pd II salts acting as bidentate ligands to give six‐membered chelates of 1:1, 1:2 and 2:2 ligand/metal ion ratios. More complex structures are obtained from pincer ligand 6 with PdCl 2 [compound 6·(PdCl 2 ) 2 ] and from the tridentate ligand 7a in reactions with Ni(ClO 4 ) 2 (compound 9 ). All new complexes were characterized by X‐ray crystallography. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)