Macrocyclic complexes with ligands based on 1,3-dicarbonyl compounds and 1,2- or 1,3-diamines

7 Macrocyclic complexes with ligands based on 1,3-dicarbonyl compounds and 1,2- or 1,3-diamines 

Product HL220 is also formed by reaction of freshly distilled Hacac with a threefold excess of ethane-1,2-diamine if the temperature of the reaction medium is no greater than 20°C [258]. In strongly acidic media pentane-2,4-dione interacts with ethane-1,2-diamine giving the cyclic product diazepin L221 (Eq. 2.133) [259], 

Complexes of the bivalent 3d metals with H2L219 can be obtained both by direct interaction of the corresponding metal salt with the presynthesised ligand [261] and in situ. For example, [Ni(L219)] is isolated from the reaction of Ni(en)2Cl2 with pentane-2,4-dione in the presence of a catalytic quantity of pyridine [262], as well as on addition of nickel(II) acetate to an equimolar mixture of ethane-1,2-diamine and pentane-2,4-dione, or by interaction of bis[4-amino-3-penten-2-onato(2-)]nickel( II) with en [260, 263]. 

Macrocycle H2L223 can also be obtained in a non-template way by reaction of en with 4-amino-3-penten-2-one [269] or yS-aminothiones [270, 271] resulting from activation of ketone or thioketone groups by triethyloxonium tetrafluoroborate. 

Related complexes of other metals, such as [M]L7)] where M = Fe, Co and Pd, have been prepared by the same method [276]. Both the reactions of precursor [Pd]L6)] and final formation of [Pd]L7)] proc easily. Palladium] II) seems to favour the template process in the same way as nickel(II) and copper]II). In contrast to palladium] II), platinum] II) is oxidised during construction of H2L6, and the resulting product in this case is [Pt ]L6)Cl2] . All attempts to produce the macrocyclic complex of platinum] II) were unsuccessful because, after the reaction with en, [Pt]L6)Cl2] + decomposed. The template reaction probably fails to take place due to the octahedral coordination of the metal, as the postulated mechanism for the ring closure reaction involves ethane-1,2-diamine taking up axial positions [277]. 

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