'Dibenzotetraaza[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-phenylenediamine with /5-dicarbonyl compounds, carried out in the presence of metal ions, leads easily and efficiently to the metal complexes. However, this so called template procedure is limited only to the later transition metals, usually Ni2+, more rarely Cu2+ and Co2+. Consequently, the majority of complexes of other metals, described in the literature, have been synthesized by the insertion of metal into the preformed macrocyclic ligand. The insertion is usually accomplished 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]annulenes. Crystallographic data for the main important ligands and complexes may be found in the following papers: H2taa — [128, 132], H2tmtaa — [25], H2omtaa — [121, 122], H2dmdptaa — [125], 6,17-dmtaa — [129], [Ni(Il)taa]. A review concerning the transition metal complexes has also appeared [126]. It has been found crystallographically that dibenzotetraaza[14]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-tetrasubstitutod macrocycles adopt the saddle-shaped conformation in which o-phenylene rings and diiminate chelate framework are tilted to opposite sides of the plane defined by four nitrogen atoms (Fig. 1). Non-planar conformation of the macrocyclic framework in the H2tmtaa greatly influences the coordination geometry in their metal complexes. Saddle- -shaped deformation together with a relatively small size of the coordination cavity results in the tendency of metal centres to be displaced out of the N4 plane. Consequently, 5-coordination (square pyramidal), found for example in [Fe(III)(tmtaa)Cl] [1], [Cr(III)(tmtaa)Cl] [50] and [Co(III)(tmtaa)I] [1, 5], seems to be more favourable than 6-coordination. Moreover, in the 6-coordinated complexes metal ions favour cis configuration (trigonal prismatic, e.g. [Zr(tmtaa)Cl2] [66], [Ti(tmtaa)Cl2] [63]) over trans (octahedral, e.g. [Sn(tmtaa)Cl2] [20]). Conformations other than planar and saddle-shaped for dibenzotetraaza[14]annulene framework have been observed in a few cases only: [Ge(omtaa)Te] (inverted saddle-shaped) [116], [Ru(tmtaa)(PMePh2)2] [90] and [Ru(omtaa)(PPh3)2] (Fig. 8 [93]), [Pd(tmtaa)] (Fig. 9 [97]) and [Pt(tmtaa)] [104] (step-like structure).
