A series of Cu(I) and Cu(II) complexes of a varie
ty of
ta2.gif" BORDER=0 ALIGN="middle">-dike
timina
te ligands (L
-) wi
th a range of subs
ti
tu
tionpa
tterns were prepared and charac
terized by spec
troscopic, elec
trochemical, and, in several cases, X-raycrys
tallographic me
thods. Specifically, complexes of
the general formula [LCuCl]
2 were s
truc
turally charac
terizedand
their magne
tic proper
ties assessed
through EPR spec
troscopy of solu
tions and, in one ins
tance, by variable-
tempera
ture SQUID magne
tiza
tion measuremen
ts on a powder sample. UV-vis spec
tra indica
ted reversibledissocia
tion
to 3-coordina
te monomers LCuCl in solu
tion a
t tempera
tures above -55
ti
ties/deg.gif">C. The Cu(I) complexesLCu(MeCN) exhibi
ted reversible Cu(I)/Cu(II) redox couples wi
th
E1/2 values be
tween +300 and +520 mV versusNHE (cyclic vol
tamme
try, MeCN solu
tions). These complexes were highly reac
tive wi
th O
2, yielding in
termedia
tes
tha
t were iden
tified as rare examples of neu
tral bis(
ti
ties/mgr.gif">-oxo)dicopper complexes on
the basis of
their EPR silence,diagnos
tic UV-vis absorp
tion da
ta, and O-iso
tope-sensi
tive resonance Raman spec
troscopic fea
tures. The s
truc
turalfea
tures of
the compounds [LCuCl]
2 and LCu(MeCN) as well as
the proclivi
ty
to form bis(
ti
ties/mgr.gif">-oxo)dicopper produc
tsupon oxygena
tion of
the Cu(I) complexes are compared
to da
ta previously repor
ted for complexes of more s
tericallyhindered
ta2.gif" BORDER=0 ALIGN="middle">-dike
timina
te ligands (Aboelella, N. W.; Lewis, E. A.; Reynolds, A. M.; Brennessel, W. W.; Cramer, C.J.; Tolman, W. B.
J. Am. Chem. Soc. 2002,
124, 10600. Spencer, D. J. E.; Aboelella, N. W.; Reynolds, A. M.;
Holland, P. L.; Tolman, W. B.
J. Am. Chem. Soc. 2002,
124, 2108. Holland, P. L.; Tolman, W. B.
J. Am. Chem.Soc. 1999,
121, 7270). The observed s
truc
tural and reac
tivi
ty differences are ra
tionalized by considering
the s
tericinfluences of bo
th
the subs
ti
tuen
ts on
the flanking aroma
tic rings and
those presen
t on
the
ta2.gif" BORDER=0 ALIGN="middle">-dike
timina
te backbone.