Inorganic Chemistry
Article
thermodynamically favored over the formation of the dimeric
species 5 by 12 kcal/mol, and the C−H bond activation in 5 to
generate 6 is 11 kcal/mol downhill.
2699 (m), 2621 (w), 1999 (s, N−N), 1402 (w), 1362 (s), 1317 (m),
1
8
234 (s), 1206 (s), 1101 (s), 1065 (m), 1022 (s), 965 (m), 882 (m),
18 (s), 721 (s), 631 (s). Anal. Calc: C, 49.10; H, 9.27; N, 10.74.
Observed C, 48.94; H, 9.19; N, 7.79. Complex 4 readily loses N . Mp
2
1
48−150 °C.
EXPERIMENTAL SECTION
[
(PNP)Co] (5). The synthesis was carried out analogously to that of
■
2
4
under an Ar atmosphere, starting with KC (0.30 g, 2.2 mmol) and
General Considerations. Unless otherwise noted, all reactions
8
[
(
(PNP)CoCl] (0.75 g, 1.9 mmol), to yield brown, block-like crystals
0.34 g, 50%) after crystallization from hexane. Crystals suitable for an
X-ray diffraction study were grown from a concentrated solution of
were performed using standard Schlenk techniques under a N -
2
atmosphere or in a N -atmosphere glovebox. Solvents were dried by
passing through a column of activated alumina and degassed with
nitrogen. C D and C D CD were dried over Na/benzophenone
and vacuum transferred. All NMR spectra were obtained in C D (at
2
1
32
diethyl ether cooled to −40 °C. H NMR (C D , 25 °C, 400 MHz): δ
6
6
6
6
6
5
3
4
.87 (br, 4H, PCH(CH )), 3.10 (br, 4H, NCH ), 2.76 (br, 4H,
3
2
6
6
NCH ), 2.24 (br, 12H, PCH(CH ) (4H) and PCH (8H)), 1.90 (br,
12H, CH ), 1.31 (br, 12H, CH ), 0.89 (br, 12H, CH ), 0.31 (br, 12H,
CH ). P{ H} NMR (C D , 25 °C, 400 MHz): δ 85.71 (br). IR
ambient temperature) or C D CD (for low temperature experiments)
2
3
2
6
5
3
1
using Bruker AVQ-400, AV-500, or AV-600 spectrometers. H NMR
chemical shifts (δ) were calibrated relative to the residual solvent peak.
Magnetic susceptibility measurements were performed in C D
according to the Evans NMR method. Melting points were
determined using sealed capillaries prepared under a nitrogen
atmosphere. Infrared (IR) spectra were recorded with a Thermo
Scientific Nicolet iS10 series FTIR spectrophotometer as a powder or
a Nujol mull between KBr plates. Elemental analyses were performed
at the University of California, Berkeley Microanalytical Facility. X-ray
crystal diffraction analyses were performed at the University of
3 3 3
31
1
3
6
6
−
1
(
(
cm ) 1260 (s), 1149(w), 1092 (s), 1025 (s), 880 (w), 799 (s), 668
w), 607 (m). Anal. Calc: C, 52.89; H, 9.99; N, 3.85. Observed C,
6
6
3
3
52.87; H, 9.66; N, 3.90. Mp 113−116 °C. μ = 0.8 ± 0.1 μ /Co. MS
726.3325 (M ).
Co(H)(μ-PNP)(μ-PCH CH NCHCH P)Co] (6). 6 is formed by
eff
B
+
[
2
2
2
rearrangement of 5 in solution (20 days) and in solid state (two
months). H NMR (C D , 25 °C, 400 MHz): δ 11.09 (br), 4.74 (br),
1
6
6
3
0
.11 (br), 2.79 (br), 2.14 (br), 1.85 (br, 1.56 (br), 1.33 (br), 1.02 (br),
.34 (br), −0.90 (br), −1.49 (br), −6.99 (br, Co-H).). P{ H} NMR
3
1
1
California, Berkeley CHEXRAY facility. [(HPNP)CoCl ] (1) was
2
21
(
C D , 25 °C, 400 MHz): δ 93.5 (br), 86.9 (br), 72.9 (br). μ = 1.2 ±
prepared according to literature procedure. The remaining starting
materials were obtained from Aldrich and used without further
purification.
6
6
e
f
f
0
.3 μ /Co.
B
[
(HPNP)CoCl(H)SiH Ph] (7). H SiPh (0.30 mL, 2.4 mmol) was
2 3
added via syringe to a solution of [(HPNP)CoCl] (0.30 g, 0.75 mmol)
in 5 mL of toluene at room temperature. The solution was stirred for 1
h. A color change from blue to yellow was observed. The solution was
cooled to −40 °C to give yellow, rod-like crystals (0.25 g, 66%).
Crystals suitable for an X-ray diffraction study were grown from a
[
(PNP)CoCl] (2). A 1.6 M solution of n-BuLi (0.90 mL, 1.4 mmol) in
hexanes was added to a suspension of [(HPNP)CoCl ] (0.60 g, 1.4
2
mmol) in 25 mL of toluene at −78 °C. The suspension immediately
turned from purple to red. The reaction mixture was allowed to warm
to room temperature and was stirred for 3 h. The solvent was removed
under vacuum, and the product was extracted with hexanes (3 × 15
mL). The solution was concentrated and cooled to −40 °C to give
brown, block-like crystals (0.23 g, 42%). Crystals suitable for an X-ray
diffraction study were grown from a concentrated solution of diethyl
1
concentrated solution of toluene cooled to −40 °C. H NMR
(
C D CD , 25 °C, 400 MHz): δ 8.25 (d, 2H, o-C H ), 7.21 (m, 3H,
6
5
H
3
6
5
m-C
2H, NCH
(br, 4H, PCH
and p-C
H
), 6.20 (br, 1H, NH), 4.69 (s, 2H, SiH
), 2.11 (br, 4H, PCH(CH
), 1.25−0.70 (m, 24H, CH ), −28.78 (m, 1H, Co-H,
, 25 °C, 400 MHz): δ 87.42
), 2.87 (br,
6
5
6
5
2
), 2.64 (br, 2H, NCH
)
3 2
), 1.61
2
2
1
ether cooled to −40 °C. H NMR (C D , 25 °C, 400 MHz): δ 1.73
2
3
6
6
31
1
31
1
(
(
(
1
4
6
br), 1.06 (br), 0.31 (br), −3.47 (br), −17.32 (br). P{ H} NMR
J
H−P: 55 Hz). P{ H} NMR (C
6
D
CD
5
3
−1
−1
C D , 25 °C, 400 MHz): δ −1.83 (br). IR (cm ) 2816 (m), 2797
(br), 66.16 (br). IR (cm ) 3179 (w), 2037 (w), 1260 (s), 1084 (s),
1019 (s), 936 (w), 843 (m), 799 (s), 724 (w), 698 (w). Anal. Calc: C,
52.01; H, 8.93; N, 2.76. Observed C, 51.82; H, 9.11; N, 2.68. Mp 87−
91 °C (d).
6
6
s), 2708 (w), 2625 (w), 1404 (w), 1364 (s), 1318 (m), 1238 (s),
208 (m), 1098 (s), 1024 (s), 882 (m), 723 (s), 632 (s). Anal. Calc: C,
8.19; H, 9.10; N, 3.51. Observed C, 48.17; H, 9.48; N, 3.50. Mp 60−
3 °C. μ = 1.8 ± 0.2 μ .
[(HPNP)CoCl](BPh ) (8). A suspension of AgBPh (0.22 mL, 0.52
eff
B
4
4
[
(HPNP)CoCl] (3). After the extraction of 2, the remaining residue
mmol) in 15 mL of THF was added via cannula to a solution of
[(HPNP)CoCl] (0.20 g, 0.50 mmol) in 10 mL of THF at room
temperature. The reaction mixture turned from a blue solution to a red
was extracted with toluene (4 × 15 mL) to give a blue solution. The
solution was concentrated and cooled to −40 °C to give blue, block-
like crystals (0.10 g, 18%). Crystals suitable for an X-ray diffraction
0
suspension and the formation of Ag is observed. After stirring for 1 h,
study were grown from a concentrated solution of toluene cooled to
the solvent was removed under vacuum, and the product was extracted
with THF (3 × 10 mL). The solution was concentrated and cooled to
−40 °C to give red, block-like crystals (0.28 g, 78%). Crystals suitable
1
−
40 °C. H NMR (C D , 25 °C, 400 MHz): δ 64.76 (br), 29.22 (br),
6
6
2
0.10 (br), 17.84 (br), 11.70 (br), 10,26 (br), −0.20 (br), −1.76 (br),
31
1
−
13.57 (br). P{ H} NMR (C D , 25 °C, 400 MHz): δ 83.0 (br). IR
cm ) 3216 (s, N-H), 1408 (w), 1363 (s), 1244 (m), 1181 (m), 1157
w), 1080 (s), 1044 (s), 1012 (s), 886 (m), 815 (s), 769 (m). 678 (s),
for an X-ray diffraction study were grown from a concentrated solution
6
6
−1
1
(
(
of THF/diethyl ether cooled to −40 °C. H NMR (C
6
D
6
, 25 °C, 400
MHz): δ 6.23 (br), 5.05 (br), 3.62 (br), 1.48 (br), 0.96 (br), 0.38 (br).
−1
6
4
30 (m), 606 (s). Anal. Calc: C, 48.07; H, 9.33; N, 3.50. Observed C,
IR (cm ) 3182 (w), 1578 (m), 1424 (m), 1260 (s), 1085 (s), 1031
(s), 800 (s), 732 (s), 705 (s), 612 (m). Anal. Calc: C, 66.82; H, 7.99;
N, 1.95. Observed C, 66.81; H, 8.16; N, 1.76. Mp 117−119 °C.
Equilibrium constant measurements by UV−vis for 3/7: Two
solutions of known concentration of 3 and phenylsilane were
8.15; H, 9.48; N, 3.59. Mp 186−188 °C. μ = 2.6 ± 0.2 μB.
eff
[
(PNP)CoN ] (4). A solution of 2 (0.70 g, 1.8 mmol) in 15 mL of
2
THF was added to a suspension of KC (0.31 g, 2.3 mmol) in 10 mL
8
of THF at −78 °C under an N2 atmosphere. The suspension
immediately turned from brown to red-brown. The reaction mixture
was allowed to warm to room temperature and was stirred for 2 h. The
solvent was removed under vacuum, and the product was extracted
with hexane (3 × 15 mL). The solution was concentrated and cooled
to −40 °C to give brown, block-like crystals (0.53 g, 77%). Crystals
suitable for an X-ray diffraction study were grown from a concentrated
prepared: (a) [3] = 0.006 M, [H
SiPh] = 0.006 M; (b) [3] = 0.011
3
M, [H SiPh] = 0.026 M. The solutions were placed in a 1 cm Schlenk-
3
type quartz cell and transferred to Cary 50 UV−vis spectrophotometer
adapted with a calibrated liquid nitrogen low-temperature apparatus.
The values were recorded each 5 °C in the 60−90 °C temperature
range, waiting at least 5 min once the target temperature was reached
to ensure equilibrium. The equilibrium constant was calculated by the
1
solution of hexane cooled to −40 °C. H NMR (C D , 25 °C, 400
6
6
MHz): δ 2.98 (br, 4H, N-H), 2.11 (br, 4H, PCH(CH ) ), 1.67 (br,
formula K = [7]/([3][H SiPh]) (where [H SiPh] = [H SiPh]
−
3
2
3
3
3
initial
3
1
1
4
(
H, PCH ), 1.39 (br, 12H, CH ), 1.15 (br, 12H, CH ). P{ H} NMR
[7]; and [7] = [3]initial − [3]). A Van’t Hoff plot was generated for
each solution and fitted to a line by the least-squares method. The
obtained values were averaged to obtain the thermodynamic
parameters.
2
3
3
13
1
C D , 25 °C, 400 MHz): δ 92.54 (s). C{ H} NMR (C D , 25 °C,
6
6
6
6
4
00 MHz): δ 61.4 (m, NCH ), 25.2 (m, PCH(CH )), 23.7 (m,
2
3
−1
PCH ), 20.0 (s, CH ), 18.6 (s, CH ). IR (cm ) 2816 (m), 2783 (w),
2
3
3
1
1548
dx.doi.org/10.1021/ic4018882 | Inorg. Chem. 2013, 52, 11544−11550