Nickel II octaazamacrocyclic complexes based on thiocarbohydrazide

Another resemblance is the tendency of S-alkylisothiocarbohydrazides to form five-membered rather than six-membered chelate rings by coordination to metal 

It is noteworthy that non-coordinated S-methylisothiocarbohydrazidium iodide adopts the same cis,trans conformation in the solid state [123]. This peculiarity, as discussed below, predetermines to a great extent the structure of the final ligand product when assembled templately. 

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. 

Thus macrocyclic coordination compounds of the tetradecine type are synthesised from alkylated isothiocarbohydrazidium iodides and a-dicarbonyl com- 

The intensely coloured compoimds [Ni(L83)]-[Ni(L88)] are stable when heated in air to relatively high temperatures, despite the presence of N-N bonds. Such properties are conditioned by the high degree of conjugation in the macrocycle and by the consequent decrease in the internal energy of the molecule. 

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