V. Korner et al., REACTIONS OF THE TRIPOD-CO-TEMPLATE CH3C( CH(2)PPH(2))(3)CO(II) WITH FUNCTIONALIZED HYDRAZINES, Chemische Berichte, 129(9), 1996, pp. 1107-1113
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.