The coordination chemistries of the potential tetradentate ligands
N,
N'-bis(3,5-di-
tert-butyl-2-hydroxyphenyl)ethylenedia
mine, H
4[L
1], the unsaturated analogue glyoxal-bis(2-hydroxy-3,5-di-
tert-butylanil), H
2[L
2], and
N,
N'-bis(2-hydroxy-3,5-di-
tert-butylphenyl)-2,2-dimethylpropylenedia
mine, H
4[L
3], have been investigated with nickel(II),palladium(II), and copper(II). The complexes prepared and characterized are [Ni
II(H
3L
1)
2] (
1), [Ni
II(HL
2)
2]·
5/
8CH
2Cl
2(
2), [Ni
II(L
3![](/images/entities/bull.gif)
![](/images/entities/bull.gif)
)] (
3), [Pd
II(L
3![](/images/entities/bull.gif)
![](/images/entities/bull.gif)
)][Pd
II(H
2L
3) (
4), and [Cu
II(H
2O)(L
4)] (
5), where (L
4)
2- is the oxidized dii
mine form of(L
3)
4- and (L
3![](/images/entities/bull.gif)
![](/images/entities/bull.gif)
)
2- is the bis(
o-i
minosemiquinonate) diradical form of (L
3)
4-. The structures of compounds
1-
5have been deter
mined by single crystal X-ray crystallography. In complexes
1 and
2, the ligands (H
3L
1)
- and(HL
2)
- are tridentate and the nickel ions are in an octahedral ligand environment. The oxidation level of the ligandsis that of an aromatic
o-a
minophenol.
1 and
2 are paramagnetic (
eff ~ 3.2
B at 300 K), indicating an
S = 1ground state. The diamagnetic, square planar, four-coordinate complexes
3 and [Pd
II(L
3![](/images/entities/bull.gif)
![](/images/entities/bull.gif)
)] in
4 each contain twoantiferromagnetically coupled
o-i
minobenzosemiquinonate(1-)
![](/images/gifchars/pi.gif)
radicals. Diamagnetic [Pd
II(H
2L
3)] in
4 forms aneclipsed dimer via four N-H···O hydrogen bonding contacts which yields a nonbonding Pd···Pd contact of 3.0846(4) Å. Complex
5 contains a five-coordinate Cu
II ion and two
o-a
minophenolate(1-) halves in (L
4)
2-. Theelectrochemistries of complexes
3 and
4a ([Pd
II(L
3![](/images/entities/bull.gif)
![](/images/entities/bull.gif)
)] of
4) have been investigated, and the EPR spectra of themonocations and -anions are reported.