4631370512

330 J. EILMES, M PTASZEK

ABSTRACT

“Dibenzotetr aaza[ 14]annulenes. Part II” presents an overview of the transition and main groups metal compounds of the title macrocyclic ligands. The results of the crystal structure determination are also summarized.

Synthesis. As it was reported in Part I, the 2 + 2 condensation of o-pheny-lenediamine with /?-dicarbonyl compounds, carried out in the presence of metal ions, leads easily and efficiently to the metal complexes. However, this so called template procedurę is limited only to the later transition metals, usually Ni^{2 +} , morę rarely Cu²⁺ and Co^{2 +} . Conseąuently, the majority of complexes of other metals, described in the literaturę, have been synthesized by the insertion of metal into the preformed macrocyclic ligand. The insertion is usually accomp-lished through the reaction of a free ligand with a salt of the appropriate metal (e.g. [1, 74,97]) or its labile complex (e.g. [25, 36, 89]), as well as by the reaction with a metallorganic compound (e.g. [51, 109, 110]) (Scheme 1). The use of dilithiated derivatives of dibenzotetraaza[14]annulenes (Scheme 2) instead of a neutral ligand proved to be also successful [66, 81].

A number of new metal derivatives have been obtained as a result of further reactions of the metal complexes with various reagents. For example, oxidation of a central metal atom [5, 89] and transmetallation [53], as well as metal-carbon [77, 17, 18] and metal-metal [29, 31, 52] bond formation are reported.

Structure. X-Ray crystal structure determination has been done for a number of free ligands and metal complexes of dibenzotetraaza[14]annulencs. Crystallographic data for the main important ligands and comp!exes may be found in the following papers: H₂taa — [128, 132], H₂tmtaa — [25], H₂omtaa — [121, 122], H₂dmdptaa — [125], 6,17-dmtaa — [129], [Ni(Il)taa] - [124], [Ni(II)tmtaa] - [131], [Cu(tmtaa)] - [130, 133], [Ni(dmtaa)] -[123], A review concerning the transition metal complexcs has also appcaied [126].

It has been found crystallographically that dibenzotetraaza[l4]annulene ring in unsubstituted taa system is planar, both in the free ligand H₂taa and its square Ni(II) complex [124]. On the other hand, 6,8,15,17-tetrasubstituted ma-crocycles adopt the saddle-shapcd conformation in which o-phenylene rings and diiminate chelate framework are tilted to opposite sides of the piane de-fined by four nitrogen atoms (Fig. 1).

Non-planar conformation of the macrocyclic framework in the H₂tmtaa greatly influences the coordination geometry in their metal complexcs. Saddle--shaped deformation together with a relatively smali size of the coordination cavity results in the tendency of metal centres to be displaccd out of the N₄ piane. Conseąuently, 5-coordination (sąuare pyramidal), found for example