Adducts of NHCs as (Latent) Catalysts for Polyurethane Synthesis
3
0 min resulting in the precipitation of a white solid. The product
was dissolved in benzene. Then, aluminum chloride (87.0 mg,
0.65 mmol) was added. The reaction was stirred for 3 h; then all
volatiles were evaporated. The remaining white solid was dried in
was filtered off and washed with diethyl ether (1.8 g, 70.0%). Single
crystals suitable for X-ray analysis were obtained from CH
–
NMR spectra were obtained from different batches. Therefore,
both H NMR spectra are reported. H NMR (CD
2
2
Cl
2
1
at
H
5 °C. Absolutely identical 13C NMR spectra, but different
vacuo and recrystallized from dichloromethane and diethyl ether
1
(238.2 mg, 83% Yield). H NMR (CDCl
3
): δ = 2.31 (s, 6 H, p-
), 4.06 (s, 4 H, N-CH ), 6.97 (s, 4 H,
Mes) ppm. C NMR (CDCl ): δ = 18.2, 21.2, 51.8, 130.0, 132.8,
136.2, 139.9 ppm. HRMS: calcd. for C21 26AlCl 438.0977;
1
1
3
OD): δ = 2.28,
CH
3
), 2.37 (s, 12 H, o-CH
3
2
1
3
.32 (s, 6 H of p-mes), 2.40, 2.44 (s, 12 H, o-Mes), 4.36, 4.49 (s, 4
3
1
H, CH
2
), 6.99, 7.09 (s, 4 H, Mes) ppm. H NMR (CD
3
OD): δ =
), 7.10
OD): δ = 17.6, 21.0, 52.4, 131.0,
31.9, 136.6, 142.0, 161.4 ppm. FTIR (ATR): ν˜ = 2956 (w), 1674
H
3 2
N
2
(
.33 (s, 6 H, p-Mes), 2.40 (s, 12 H, o-Mes), 4.51 (s, 4 H, CH
2
found 438.0988. FTIR (ATR mode): ν˜ = 2921 (br), 1630 (m), 1494
s, 4 H, Mes) ppm. 13C NMR (CD
(br), 1455 (m), 1276 (s), 1191 (m), 1033 (m), 948 (s), 850 cm .
–1
3
1
–1
(
s, CO), 1547 (m), 1439 (m), 1264 (s), 855 (s) cm . MS (ESI): m/z Typical Procedure for the Recording of the Reaction Kinetics: The
+
=
351.2 [M + H] .
catalyst (14.0 mmol-% with respect to DABCO; DABCO was used
on 1.0 wt.-% base) was dissolved in a minimum amount of CH Cl
2
2
.
Compound 5: In a 50 mL Schlenk tube equipped with a stirring bar,
Then, 2 wt.-parts of Desmophen A870 BA (polyol), 1 wt.-part of
Desmodur N 3390 BA (isocyanate) (corresponding to a 1:1 molar
ratio) were added to the catalyst solution. The mixture was mixed
for 3.0 min, and then a small drop was taken from the mixture and
polyaddition kinetics were measured by real-time FTIR by using a
BIO-RAD FTS 6000 spectrometer for 2 h.
,3-dimesitylimidazolium-2-carboxylate[
was suspended in benzene (15 mL); zinc chloride (117.0 mg,
.86 mmol) was then added to the suspension. The Schlenk tube
was taken out of the glove box and placed in a 85 °C oil bath. After
h of stirring, the Schlenk tube was cooled to room temperature.
20]
(300 mg, 0.86 mmol)
1
0
2
The solvent was removed in vacuo, and the Schlenk tube was taken
inside the box again. The crude reaction mixture was dissolved in
dichloromethane. The solution was filtered through glass fiber filter
Typical Procedure for the Recording of the Reaction Kinetics (Lat-
ency): The catalyst (3.5 mmol-% with respect to isocyanate) was
paper. Evaporation of CH
2
Cl
): δ = 7.04 (s, 2 H), 6.9 (s, 4 H), 2.31 (s,
H), 2.0 (s, 12 H) ppm. 13C NMR (CDCl
): δ = 173.1, 139.3,
2
resulted in a white solid (338 mg,
dissolved in a minimum amount of CH
Desmophen A870 BA (polyol), 1 wt.-part of Desmodur N 3390 BA
isocyanate) (corresponding to a 1:1 molar ratio) were added to the
2 2
Cl . Then, 2 wt.-parts of
1
8
6
1
2
9.0%). H NMR (CDCl
3
3
(
35.6, 133.9, 129.2, 123.0, 21.2, 17.9 ppm. FTIR (ATR mode): ν˜ =
catalyst solution. The mixture was mixed for 3.0 min, kept at room
temperature for 45 min, and then the temperature was raised to
919 (br), 1486 (m), 1403 (m), 1377 (m), 1230 (m), 1106 (m), 930
–1
+
(
m), 850 (s), 752 (s) cm . MS (ESI): m/z = 845.16 [M – Cl] .
Zn (876.12): calcd. C 57.23, H 5.49, N 6.36; found C
7.01, H 5.51, N 6.28.
65 °C. The entire process was monitored by real-time FTIR by
C
42
H48Cl
4
N
4
2
using a BIO-RAD FTS 6000 spectrometer.
5
Compound 6: In a 50 mL Schlenk tube equipped with a stirring
Typical Procedure for Isocyanurate Formation: A solution of phenyl
bar, 1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-1-ium-2-carboxylate isocyanate (1:1 v/v in thf) was added to an oven-dried 25 mL
(
300 mg, 0.82 mmol) was suspended in benzene (15 mL); zinc chlo-
Schlenk tube containing 1,3-dimesityl-4,5-imidazolinium-2-carbox-
ylate (3.0 mg, 1.0 mol-% with respect to the isocyanate). The reac-
tion mixture was stirred at 65 °C for 12 h. Yields were determined
by GC–MS.
ride (113.0 mg, 0.82 mmol) was then added to the suspension.
Then, the Schlenk tube was taken out of the glove box and placed
in a 85 °C oil bath. After 2 h of stirring, the Schlenk tube was
cooled to room temperature. The solvent was removed in vacuo,
and the Schlenk tube was taken inside the box again. The crude
reaction mixture was dissolved in dichloromethane. The solution
Typical Procedure for the Cyclotrimerization of HMDI Trimer: Cat-
alyst 3 (1.0 mol-%, 3.5 mg; with respect to HMDI trimer) was dis-
solved in a minimum amount of dichloromethane; HMDI trimer
(0.5 g) was added to the catalyst solution. The reaction mixture was
was filtered through glass fiber filter paper. Evaporation of CH
2
Cl
): δ =
2
1
resulted in a white solid (340 mg, 90.0%). H NMR (CDCl
.96 (4 H, Mes), 3.45 (t, J = 2.25 Hz, 4 H, N-CH
CH
), 2.36 (s, 12 H), 2.27 (s, 6 H) ppm. 13C NMR (CDCl
3
6
2
), 2.39 (2 H, mixed and heated to 65 °C for 1 h, during this time a white solid
): δ =
of polymeric HMDI trimer was obtained. Yield: 495.0 mg, 99.0%.
2
3
1
1
94.7, 153.3, 140.2, 139.7, 139.5, 136.8, 135.7, 134.7, 130.3, 130.0,
28.4, 47.6, 45.1, 21.2, 21.1, 20.4, 19.6, 18.2, 18.0 ppm. FTIR (ATR
FTIR (ATR mode): ν˜ = 2931 (br), 2358 (br), 2264 (m, free NCO),
1675 (s, CO), 1454 (br), 1423 (br) cm .
–
1
mode): ν˜ = 2917 (br), 1663 (s), 1516 (m), 1310 (s), 1207 (s), 850 (s)
cm . MS (ESI): m/z = 877.21 [M – Cl] .
–1
+
X-ray Analyses for 1, 4, and 8: Data were collected with a Nonius
KappaCCD diffractometer equipped with graphite-monochro-
matized Mo-K -radiation and a nominal crystal to area detector
α
Compound 8: In a 10 mL vial equipped with a stirring bar, 1,3-bis-
(
2,4,6-trimethylphenyl)imidazol-2-ylidene (250.0 mg, 0.82 mmol)
was dissolved in benzene. Then, aluminum chloride (110.0 mg,
.81 mmol) was added. The reaction was stirred for 3 h, and then
all volatiles were evaporated. The remaining white solid was dried
in vacuo and recrystallized from CH Cl and diethyl ether
306.0 mg, 85%). Crystals suitable for single crystal X-ray analysis
distance of 36 mm. The structures were solved with direct methods
2
SHELXS86 and refined against F SHELX97. All non-hydrogen
0
atoms were refined with anisotropic displacement parameters and
positions of hydrogen atoms were calculated. CCDC-711502 (for
2
2
1), -711503 (for 4), and -711504 (for 8) contain the supplementary
(
crystallographic data for this paper. These data can be obtained
free of charge form The Cambridge Crystallographic Data Centre
via www.ccdc.cam.ac.uk/data_request/cif.
1
were obtained from CH
2
2
Cl
2
/diethyl ether. H NMR (CDCl
), 7.02 (s, 4 H, Mes), 7.21
) ppm. 13C NMR (CDCl
): δ = 17.7, 21.3, 124.7,
29.5, 133.2, 135.3, 140.4 ppm. HRMS: calcd. for C21 24AlCl
36.0820; found 436.0679. FTIR (ATR): ν˜ = 2917 (br), 1603 (m),
3
): δ =
3 3
.13 (s, 12 H, o-CH ), 2.36 (s, 6 H, p-CH
(s, 2 H, N-CH
2
3
1
4
1
H
3 2
N
Supporting Information (see footnote on the first page of this arti-
cle): X-ray and structural data of compounds 1, 4, and 8; pseudo-
second-order kinetic graphs for compounds 1 and 3–5, kinetic plots
–
1
543 (m), 1480 (br), 1230 (s), 1127 (m), 1030 (m), 850 cm .
Compound 9: In a 10 mL vial equipped with a stirring bar, 1,3-bis-
2,4,6-trimethylphenyl)imidazolin-2-ylidene (200.0 mg, 0.65 mmol)
of PUR formation under the action of MgCl
ZnCl , 5, and 7.
2 3 2
, Zn(CH COO) ,
(
2
Eur. J. Inorg. Chem. 2009, 1970–1976
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
1975