Validación del instrumento

The synthesis was also achieved by rapid addition o f the deprotonated ligand to solid

VOSO4 under stirring at room temperature, then the temperature was increased to 60 °C and preserved until the end o f the reaction. This was done to avoid the loss o f the product in the aqueous layer in which it is soluble. The product did not change colour upon collection with the spatula from the Schlenk tube in the glove box.

Selected characteristic IR absorptions for compound 170 are given in Table 3.9. The band for the C=N group appears at 1614 cm '\ displaced to lower frequency than the free ligand indicating a decrease in the C=N bond order due to the involvement o f N in the co-ordination o f the metal. The stretching frequency from 962 cm'^ was assigned to ü(vo). The value is intermediate between the values reported for monomeric and polymeric VO salen type complexes, closer to the monomeric form [42].

3.6 Conclusions

Syntheses o f V,A/''-bis(2,2’-imino-R-benzylideneimino)-cyclobexane nickel, copper, manganese, cobalt and vanadyl complexes were performed and the products were characterized using different techniques. While complexation with nickel and copper gave the corresponding M(II)(ambch) complexes (M = Ni, Cu) for most ligands used, complexation o f 5-Me-ambch with Cu(0 Ac) 2 and CuCb in air resulted in formation o f

Cu(ni) species. This is similar to previous studies carried out on 5-R-salen ligands which indicated that the ligand with R=Me has the highest tendency to form 5- coordinated complexes.

Manganese R-ambch complexes (R=H, 3-Me) were obtained via complexation o f the ligand with MnCl], while the product proved hard to isolate pure from the route involving complexation with Mn(0 Ac) 2 followed by ligand exchange. After synthesis o f

Co(R-ambch)(R=H, 3-Me, 5-Me) complexes, the reactivity o f the unsubstituted complex toward oxygen in presence o f different nucleophiles was investigated. Co(in)(ambch) complexes were isolated in reaction o f Co(ambch) with 4-t-Bu-phenol, CHCI3 and ethanol/ A c O . The process depends on the solvent and the nucleophile

employed. Further studies are necessary in order to obtain more information regarding oxidation in presence o f 2,4-di-^-Bu-phenol and 2-butanol.

Complexation with V0 (acac) 2 resulted in formation o f the asymmetrical ligand 171 and

o f the corresponding vanadyl complex 173, which is thermodynamically more favourable than formation o f VO(ambch). Synthesis o f the latter complex was achieved by employing a different vanadyl source, VOSO4.

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