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

Abstract

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 diand 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

Synthesis of Secondary, Tertiary and Quaternary 1,3,5‐Triazapenta‐1,3‐dienes and Their CoII, ZnII, PdII, CuII and BF2 Coordination Compounds

“…[12] By ring opening of tri(2-pyridyl)triazine in the presence of the Lewis acid copper(II) acetate and sodium perchlorate in methanol Kajiware et al obtained a complex chain structure, which was converted to a bis[2,4-di(2-pyridyl)-1,3,5-triazapentadienyl]copper(II) complex by the addition of EDTA. [13] Access to a neutral copper complex from 4-cyanopyridine, Cu(OH) 2 and (NH 4 ) 2 CO 3 , as an ammonia source, was achieved by Zhang et al in 2005. [14] Tertiary 1,3,5-triazapentadienes 3 as anionic ligands are scarcely investigated.…”

“…Primary (1), secondary (2), tertiary (3) and quaternary (4) 1,3,5-triazapenta-1,3-dienes are interesting as nitrogenrich bidentate ligands for metal ion and Lewis acid coordination forming six-membered chelates (Scheme 1). [1] In comparison to β-diimines, the additional central nitrogen atom influences the electronic properties of the ligand by its electronegativity and its lone pair, and allows cyclic conjugation not only in its anionic but also in its neutral form.…”

“…they may be considered as amino-substituted dimers of nitriles. [2] Several different synthetic routes for primary, secondary and tertiary 1,3,5-triazapentadienes 1-3 have been disclosed. Ley and Müller were the first to prepare secondary triazapentadienes already in 1907 by the reaction of amidines with imidoyl halides.…”

“…In these cases a proton shift from the terminal nitrogen atom of the free ligand to the central nitrogen atom of the complex was observed. Two equivalents of 3c reacted at room temperature with Cu(ac) 2 or Pd(ac) 2 to form the neutral 2:1 chelate complexes (3c) 2 ·Cu and (3c) 2 ·Pd, respectively. A fluorescent 1:1 boron complex 3c·BF 2 was obtained from 3c and boron trifluoride-diethyl ether.…”

“…[4,5] Tertiary 1,3,5-triazapenta-1,3-reacting 2b with boron trifluoride-diethyl ether. From the tertiary triazapentadiene 3c and CoCl 2 or ZnCl 2 the six-membered 1:1 chelate complexes 3c·CoCl 2 and 3c·ZnCl 2 , respectively, were obtained. In these cases a proton shift from the terminal nitrogen atom of the free ligand to the central nitrogen atom of the complex was observed.…”