The reac
tion of 2 equiv of
the bulky ligand
N,N'-bis(3,5-di-
tert-bu
tylphenyl)-1,2-phenylenediamine, H
2[
3L
PDI], excess
trie
thylamine, and 1 equiv of M(CH
3CO
2)
2·4H
2O (M = Ni, Co) in
the presence of air in CH
3CN/CH
2Cl
2 solu
tionyields viole
t-black crys
tals of [Ni
II(
3L
ISQ)
2] CH
3CN (
1) or viole
t crys
tals of [Co(
3L)
2] (
3). By using Pd(CH
3CO
2)
2 ass
tar
ting ma
terial, green-blue crys
tals of [Pd
II(
3L
ISQ)
2]·CH
3CN (
2) were ob
tained. Single-crys
tal X-ray crys
tallographyrevealed
tha
t 1 and
3 con
tain (pseudo)
te
trahedral neu
tral molecules [M(
3L)
2] (M = Ni, Co) whereas in
2 nearlysquare planar, neu
tral molecules [Pd
II(
3L
ISQ)
2] are presen
t. Tempera
ture-dependen
t suscep
tibili
ty measuremen
tses
tablished
tha
t 1 and
2 are diamagne
tic (
S = 0) whereas
3 is paramagne
tic wi
th an
S =
3/
2 ground s
ta
te. I
t isshown
tha
t 1 con
tains
two
radical ben
zosemiquinona
te(1-)-
type monoanions, ((
3L
ISQ)
1-tities/bull.gif">,
Srad =
1/
2), and acen
tral Ni(II) ion (d
8;
S = 1) which are an
tiferromagne
tically coupled yielding
the observed
St = 0 ground s
ta
te.This resul
t has been confirmed by broken symme
try DFT calcula
tions of
1. In con
tras
t,
the
St =
3/
2 ground s
ta
teof
3 is more difficul
t to unders
tand:
the
two resonance s
truc
tures [Co
III(
3L
ISQ)(
3L
PDI)]
ti
ties/harr.gif"> [Co
II(
3L
PDI)(
3L
IBQ)] migh
t beinvoked (for
te
trahedral [Co
II(
3L
ISQ)
2] con
taining an
SCo =
3/
2 wi
th
two an
tiferromagne
tically coupled
-radical ligandsan
St =
1/
2 is an
ticipa
ted). Complex
2 is diamagne
tic (
S = 0) con
taining a Pd
II ion (d
8,
SPd = 0 in an almos
tsquare planar ligand field) and
two an
tiferromagne
tically coupled ligand radicals (
Srad =
1/
2). The elec
trochemis
tryand spec
troelec
trochemis
try of
1, 2, and
3 have been s
tudied, and elec
tron-
transfer series comprising
the species[M(L)
2]
z (
z = 2+, 1+, 0, 1-, 2-) have been es
tablished. All oxida
tions and reduc
tions are ligand cen
tered.