The crystal structure of a novel compound Cu
II(dNbpy)Br
2 (dNbpy = 4,4'-di(5-nonyl)-2,2'-bipyridine), which isused in the reverse atom transfer radical polymerization, is reported. Cu
II(dNbpy)Br
2 crystallizes in the triclinic
P1 space
group with
a = 12.5283(11) &Arin
g;,
b = 15.0256(14) &Arin
g;,
c = 17.7900(16) &Arin
g;,
ges/
gifchars/alpha.
gif" BORDER=0> = 90.350(2)
ges/entities/de
g.
gif">,
ges/
gifchars/beta2.
gif" BORDER=0 ALIGN="middle"> = 99.360(2)
ges/entities/de
g.
gif">,
ges/
gifchars/
gamma.
gif" BORDER=0 > = 107.937(2)
ges/entities/de
g.
gif">, and
Z = 2. The Cu
II center in the complex has a distorted square planar
geometry and iscoordinated by two nitro
gen atoms of a sin
gle dNbpy li
gand (Cu-N = 2.011(7) and 2.022(7) &Arin
g;) and two bromineatoms (Cu-Br = 2.3621(14) and 2.3567(13) &Arin
g;). The similarity of the absorption spectra in the solid state and insolution su
ggested that the
geometry of the complex remained unchan
ged upon dissolution. In the presence ofdNbpy, Cu
II(dNbpy)Br
2 under
goes Br substitution to form ionic [Cu
II(dNbpy)
2Br]
+[Br]
-.
ges/
gifchars/Delta.
gif" BORDER=0 >
Hges/entities/de
g.
gif"> and
ges/
gifchars/Delta.
gif" BORDER=0 >
Sges/entities/de
g.
gif"> valuesfor this equilibrium were ne
gative and dependent on the polarity of the medium. It was found that, under thetypical polymerization conditions (
T ges/entities/
ge.
gif">90
ges/entities/de
g.
gif">C and the total copper concentration in the ran
ge 1.0 × 10
-2-1.0 ×10
-1 M), Cu
IIBr
2 and 2 equiv of dNbpy will predominantly form the neutral Cu
II(dNbpy)Br
2 complex. In a polarmedium under the same conditions, [Cu
II(dNbpy)
2Br]
+[Br]
- is preferred.