Alkoxybenzimidazolin-2-ylidene Palladium Complexes
(500.13 MHz, [D6]DMSO): δ = 9.21 (s, 1 H, NCHN), 7.62 (s, 2 H, mixture was filtered through Celite and the filtrate was concen-
NCHPh2), 7.40–7.53 (m, 20 H, Ar CH), 7.10 (s, 2 H, benzimidazo-
trated in vacuo. The resulting solid was recrystallised by layering
3
lyl Ar CH), 3.86 (t, JH,H = 6.4 Hz, 4 H, OCH2), 1.58–1.65 (m, 4 hexanes onto a CHCl3 solution of the complex to give 4a as a
3
H, OCH2CH2), 1.34–1.44 (m, 4 H, CH2CH3), 0.90 (t, JH,H
=
clear crystalline solid; yield 209 mg (86%). 1H NMR (500.13 MHz,
7.4 Hz, 6 H, CH2CH3) ppm. 13C NMR (125.77 MHz, [D6]DMSO):
δ = 149.0 (benzimidazolyl Ar CO), 139.2 (NCN), 136.2 (Ar C),
129.2 (Ar CH), 129.0 (Ar CH), 128.3 (Ar CH), 125.5 (benzimidazo-
CDCl3): δ = 7.23–7.36 (m, 10 H, Ar CH), 6.70 (s, 2 H, benzimida-
3
zolyl Ar CH), 5.55 (s, 4 H, benzylic CH2), 3.85 (t, JH,H = 6.5 Hz,
4 H, OCH2), 1.68–1.74 (m, 4 H, OCH2CH2), 1.40–1.57 (m, 4 H,
lyl Ar C), 97.5 (benzimidazolyl Ar CH), 68.6 (OCH2), 64.4 CH2CH3), 0.94 (t, JH,H = 7.4 Hz, 6 H, CH2CH3) ppm. 13C NMR
(NCHPh2), 30.0 (OCH2CH2), 18.6 (CH2CH3), 13.6 (CH2CH3) (125.77 MHz, CDCl3): δ = 148.3 (benzimidazolyl Ar CO), 135.0
ppm. C41H43ClN2O2·1.5H2O (658.28): calcd. C 74.81, H 7.04, N (Ar C), 129.3 (Ar CH), 128.7 (Ar CH), 128.0 (benzimidazolyl Ar
3
4.26; found C 74.86, H 6.93, N 4.13. Crystals suitable for X-ray
diffraction were grown by the diffusion of vapours between hexanes
and a solution of the complex in chloroform.
C), 127.2 (Ar CH), 97.0 (benzimidazolyl Ar CH), 69.7 (OCH2),
53.7 (benzylic CH2), 31.1 (OCH2CH2), 19.3 (CH2CH3), 13.9
(CH2CH3) ppm (carbene carbon signal not detected).
C29H34AgClN2O2·0.15CH2Cl2 (598.66): calcd. C 58.48, H 5.78, N
4.68; found C 58.82, H 5.79, N 4.21.
Benzimidazolium Salt 3a: A solution of 1a (0.46 g, 1.31 mmol) and
α,αЈ-dibromo-o-xylene (0.17 g, 0.64 mmol) in THF (15 mL) was
stirred at reflux under nitrogen for 7 d. The solution was concen-
trated in vacuo and the residue was triturated with hexanes (3ϫ
10 mL) and dried under vacuum to yield 3a as a white powder;
Silver Complex 4b: Silver oxide (73 mg, 0.32 mmol) was added to
a solution of 2b (400 mg, 0.63 mmol) in CH3CN (15 mL) and the
mixture was heated at 70 °C in darkness for 4 d. The mixture was
filtered through Celite and the filtrate was concentrated in vacuo.
The residue was recrystallised by the diffusion of vapours between
diethyl ether and a solution of the complex in acetone to give 4b
1
yield 0.48 g (78%). H NMR (500.13 MHz, [D6]DMSO): δ = 9.45
(s, 2 H, NCHN), 7.38–7.60 (m, 18 H, Ar CH, xylyene Ar CH,
benzimidazolyl Ar CH), 5.97 (s, 4 H, benzylic CH2), 5.68 (s, 4 H,
3
3
benzylic CH2), 4.07 (t, JH,H = 6.4 Hz, 4 H, OCH2), 3.95 (t, JH,H as
a
colourless crystalline solid (405 mg, 87%). 1H NMR
(500.13 MHz, CDCl3: δ = 7.35–7.41 (m, 12 H, Ar CH), 7.16–7.24
= 6.4 Hz, 4 H, OCH2), 1.69–1.78 (m, 8 H, OCH2CH2), 1.40–1.57
3
(m, 8 H, CH2CH3), 0.97 (t, JH,H = 7.4 Hz, 12 H, CH2CH3) ppm. (m, 8 H, Ar CH), 7.21 (s, 2 H, NCHPh2), 6.40 (s, 2 H, benzimidazo-
13C NMR (125.77 MHz, [D6]DMSO): δ = 149.3 (benzimidazolyl lyl Ar CH), 3.63 (t, JH,H = 6.5 Hz, 4 H, OCH2), 1.55–1.64 (m, 4
3
3
Ar CO), 149.2 (benzimidazolyl Ar CO), 139.3 (NCN), 134.3 (Ar H, OCH2CH2), 1.32–1.40 (m, 4 H, CH2CH3), 0.88 (t, JH,H
C), 132.3 (xylyene Ar C), 130.3 (xylyene Ar CH), 129.9 (xylyene
Ar CH), 128.9 (Ar CH), 128.6 (Ar CH), 128.0 (Ar CH), 125.1 = 188.5 (d, J109Ag,C = 269 Hz, J107Ag,C = 233 Hz, NCN), 148.4
=
7.4 Hz, 6 H, CH2CH3) ppm. 13C NMR (125.77 MHz, CDCl3: δ
1
1
(benzimidazolyl Ar C), 124.6 (benzimidazolyl Ar C), 96.4, 96.7
(benzimidazolyl Ar CH), 68.9 (OCH2), 47.7, 49.5 (benzylic CH2),
(benzimidazolyl Ar CO), 139.0 (Ar C), 130.2 (Ar CH), 129.9 (Ar
CH), 129.4 (Ar CH), 129.2 (benzimidazolyl Ar C), 98.7 (benzimid-
30.4, 30.5 (OCH2CH2), 18.6, 18.7 (CH2CH3), 13.6, 13.7 (CH2CH3) azolyl Ar CH), 69.7 (OCH2), 68.2 (NCHPh2), 31.7 (OCH2CH2),
ppm. C52H64Br2N4O4·H2O (986.93): calcd. C 63.28, H 6.74, N
5.68; found C 62.94, H 6.69, N 5.32.
19.8 (CH2CH3), 14.0 (CH2CH3) ppm. C41H42AgClN2O2 (738.12):
calcd. C 66.72, H 5.74, N 3.80; found C 66.88, H 6.01, N 3.95.
Crystals suitable for X-ray diffraction were grown by the diffusion
of vapours between diethyl ether and a solution of the complex in
acetone.
Benzimidazolium Salt 3b: A mixture of 1b (120 mg, 0.28 mmol),
α,αЈ-dibromo-o-xylene (36 mg, 0.14 mmol) and NaI (0.9 mg,
0.006 mmol) in CH3CN (10 mL) was stirred at reflux for 6 d. The
solvent was removed in vacuo and the residue was subjected to
column chromatography (gradient elution with EtOAc/MeOH).
The combined fractions were concentrated in vacuo, and the resi-
due was dissolved in CH2Cl2 and passed through a 0.2 μm nylon
filter. The solvent was removed in vacuo to give 3b as a white pow-
der; yield 130 mg (83%). 1H NMR (500.13 MHz, [D6]DMSO): δ =
9.48 (s, 2 H, NCHN), 7.64 (s, 2 H, NCHPh2), 7.47–7.52 (m, 12 H,
Ar CH), 7.40–7.50 (m, 10 H, Ar CH, xylyene Ar CH), 7.38 (s, 2
H, benzimidazolyl Ar CH), 7.32 (s, 2 H, benzimidazolyl Ar CH),
7.08 (m, 2 H, xylyene Ar CH), 5.96 (s, 4 H, benzylic CH2), 3.94
Preparation of Palladium Complexes
Palladium Complex 5a: Silver complex 4a (400 mg, 0.68 mmol) was
added to
a
solution of [{Pd(η3-C3H5)Cl(μ-Cl)}2] (125 mg,
0.34 mmol) in CH2Cl2 (20 mL) and the mixture was stirred in dark-
ness for 5 d. The mixture was filtered through Celite and the filtrate
was concentrated in vacuo to give 5a as a white solid; yield 384 mg
1
(90%). H NMR (500.13 MHz, CDCl3: δ = 7.30–7.35 (m, 4 H, Ar
CH), 7.25–7.30 (m, 6 H, Ar CH), 6.66 (s, 2 H, benzimidazolyl Ar
CH), 5.63–5.85 (m, 4 H, benzylic CH2), 5.10 (m, 1 H, allyl CH),
3
4.26 (m, 1 H, allyl CH), 3.85 (t, JH,H = 6.6 Hz, 4 H, OCH2), 3.19
3
(apparent t, JH,H = 6.4 Hz, 8 H, OCH2), 1.62–1.70 (m, 8 H,
2
(d, JH,H = 13.6 Hz, 1 H, allyl CH), 3.03 (m, 1 H, allyl CH), 1.93
3
OCH2CH2), 1.36–1.46 (m, 8 H, CH2CH2CH3), 0.94 (t, JH,H
=
(d, 2JH,H = 12.0 Hz, 1 H, allyl CH), 1.68–1.75 (m, 4 H, OCH2CH2),
3
7.3 Hz, 6 H, CH2CH3), 0.90 (t, JH,H = 7.3 Hz, 6 H, CH2CH3)
ppm. 13C NMR (125.77 MHz, [D6]DMSO): δ = 149.4 (benzimida-
zolyl Ar CO), 149.3 (benzimidazolyl Ar CO), 139.9 (NCN), 136.2
(Ar C), 132.3 (xylyene Ar C), 129.3 (Ar CH), 129.1 (Ar CH), 128.9
(xylyene Ar CH), 128.3 (Ar CH), 127.4 (xylyene Ar CH), 125.6
(benzimidazolyl Ar C), 124.5 (benzimidazolyl Ar C), 97.2, 97.3
(benzimidazolyl Ar CH), 68.7, 68.9 (OCH2), 64.0 (NCHPh2), 47.9
(benzylic CH2), 30.1, 30.2 (OCH2CH2), 18.6, 18.6 (CH2CH3), 13.6,
13.6 (CH2CH3) ppm. C64H72Br2N4O4·H2O (1139.12): calcd. C
67.48, H 6.55, N 4.92; found C 67.39, H 6.85, N 4.55.
3
1.43–1.49 (m, 4 H, CH2CH3), 0.93 (t, JH,H = 7.4 Hz, 6 H,
CH2CH3) ppm. 13C NMR (125.77 MHz, [D6]DMSO): δ = 190.5
(NCN), 147.2 (benzimidazolyl Ar CO), 136.4 (Ar C), 129.1
(benzimidazolyl Ar C), 129.0 (Ar CH), 128.0 (Ar CH), 127.3 (Ar
CH), 115.5 (allyl CH), 97.0 (benzimidazolyl Ar CH), 73.6 (allyl
CH2), 69.9 (OCH2), 52.4 (benzylic CH2), 49.3 (allyl CH2), 31.2
(OCH2CH2),
19.3
(CH2CH3),
14.0
(CH2CH3)
ppm.
C32H39ClN2O2Pd (625.50): calcd. C 61.44, H 6.28, N 4.48; found
C 61.58, H 6.46, N 4.45. Crystals suitable for X-ray diffraction
were grown by the slow evaporation of a CH2Cl2/hexanes solution
of the complex.
Preparation of Silver Complexes
Silver Complex 4a: Silver oxide (49 mg, 0.21 mmol) was added to
a solution of 2a (200 mg, 0.42 mmol) in CH2Cl2 (10 mL) and the added to
Palladium Complex 5b: Silver complex 4b (145 mg, 0.20 mmol) was
a
solution of [{Pd(η3-C3H5)Cl(μ-Cl)}2] (36 mg,
mixture was stirred in darkness at room temperature for 3 d. The 0.098 mmol) in CH2Cl2 (10 mL) and the mixture was stirred in
Eur. J. Inorg. Chem. 2011, 1937–1952
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1949