REACTIONS OF THE TRIPOD-CO-TEMPLATE CH3C( CH(2)PPH(2))(3)CO(II) WITH FUNCTIONALIZED HYDRAZINES

The coordination behaviour of ligands having the same basic constituti on RN=NC(=X)R' (X = O, NR '', S) in their tripod cobalt derivatives ha s been analyzed. The ligands themselves may be considered as neutral h eterodiene compounds and are in this respect vinylogues to diazenes RN =NR'. Two-electron reduction of these neutral species results in diani onic heterosubstituted heteroolefins RN(-)-N=C(X(-))R'. Due to their r edox ambiguity the oxidation state of the metal M in chelate complexes M=N(H)=N=C(X)-R' is not a priori evident. Compounds tripodCo=N(H)=N=C (X)-R'(+) [5: X, R' = O, Ph; 6: (X, R') = (py); 7: X, R' = S, NH2] are best described as containing low-spin Co(III) and dianionic ligands. Co(II) species are obtained with diethyl azodicarboxylate EtOOCN=NCOOE t as the ligand. In the mononuclear compound, with only one nitrogen a nd one carbonyl oxygen of the ligand acting as donor groups, the neutr al ligand is coordinated to give the high-spin cobalt(II) species trip od CoO(EtO)CN=N-COOEt(2+) (8). In the dinuclear compound 9 with both o f the nitrogen atoms and carbonyl groups involved in coordination the dianionic ligand bridges two high-spin cobalt(II) centers to give trip od CoO(EtO)CNNC(OEt)OCotripod(2+) (9) as a derivative with two fused f ive-membered chelate rings. In addition to the conventional analytical techniques X-ray structure analyses, cyclovoltametric measurements, m agnetic susceptibility and ESR data are used to characterize the compo unds.