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 ZnII, CuII, CoII, NiII and PdII 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 PdCl2 [compound 6·(PdCl2)2] and from the tridentate ligand 7a in reactions with Ni(ClO4)2 (compound 9). All new complexes were characterized by X‐ray crystallography. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) Multivalent amino‐substituted bis‐ and tris(armed) oligonitrile derivatives are synthesized by two alternative reaction pathways. In the solid state some derivatives show inter‐ and intramolecular hydrogen bonding. They act as chelating ligands with various metal ions to form novel types of coordination compounds.