Octaazamacrocycle

The octaazamacrocyclic complex (83) is capable of undergoing numerous transformations to give complexes with different patterns ofligand unsaturation (Scheme 36).191... 

The reduction of imBT ligand with NaBH4 in methanol led to the formation of a saturated octaazamacrocyclic amBT ligand that forms binuclear complexes with zinc(II) and copper(II) [199] and mononuclear clathrochelates with manganese, iron, cobalt, nickel, and zinc (II) [203] by treatment of the free ligand with the corresponding metal ion salts. 

The metal-promoted reactions of 1,2-dihydrazones with formaldehyde (see Scheme 35) can be compared with the purely organic reactions of 1,2-dihydrazones with orthoesters, which lead directly to macrocyclic compounds from which complexes of stnwtural type (85) can be prepared. The octaazamacrocyclic complex (83) is capable of undergoing numerous transformations to give complexes with different patterns ofligand unsaturation (Scheme 36). ... 

In 1973, Baldwin and Huff [31] reported the synthesis of the iron(n) octaazamacrocycle (2) (Figure 2), the first nonporphyrin model which acts as a reversible dioxygen carrier at relatively low temperature. The sterically hindered substituents form a cavity in which the dioxygen is fixed and retard p-0x0 dimer formation. 

Attempts to synthesise manganese(II) and zinc(II) octaazamacrocyclic compounds had no success. Complexes of these metals with 2,3-butanedione dihydrazone react with formaldehyde, but in this case products containing the acyclic tetradentate ligand L37 are isolated [2]. 

Attempts to prepare octaazamacrocyclic systems similar to L36 but derived from... 

Attempts to obtain complexes with the 16-membered octaazamacrocycle L44 by interaction of diacetyl with hydrazinium halides, followed by the subsequent addition of nickel(II) or copper(Il) salts and prolonged heating of the reaction mixture, led to the isolation of [M(L45)]X2 H20, where X = Cl , Br , N03 , C104 or BF4 andn = 0,2(Eq. 2.8) [13],... 

However, in contrast to isothiosemicarbazides, where coordination to the metal ion leads to the loss of nucleophilicity of end aminogroups, isothiocarbohydrazides on binding to the metal ion still have one non-coordinated amino group, which bears a non-bonded electron pair capable of nucleophilic attack on electrophiles. Another distinction is the chemical equivalence of the end amino groups towards condensation reactions with aldehydes and ketones. This difference is displayed advantageously in the one-pot template sjmthesis of octaazamacrocyclic systems. 

Scheme 2-7. Synthetic route to symmetric and non-symmetric octaazamacrocyclic ligand products.

Thus pSTi(L90)] can be regarded as an intermediate in the synthesis of synunetric octaazamacrocyclic products [Ni(L84)]. It is also a suitable precursor for building up other non-symmetric systems, such as [Ni(L91)]. The coordinated ligand in [Ni(L91)] is rather acidic. An X-ray diffraction study, carried out on recrystallised product from acetonitrile-pyridine mixture [Ni(L91)] (R = CH3), showed that the complex consists of the cation PyH and the anion [Ni(L91)] . The structure of the latter is given in Figure 2-16 [130]. 

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