A. Caballero et al. / Journal of Organometallic Chemistry 617–618 (2001) 395–398
397
ver(I) complex may be synthesised by the reaction of
silver(I) triflate with the in situ generated carbene.
Im), 145.4 (C2-Py), 145.9 (C4-Py). Anal. Calc. for
C H N Br : C, 54.27; H, 4.19; N, 12.66. Found: C,
25
23
5
2
5
4.15; H, 4.24; N, 12.59%.
4. Experimental
4.3. Preparation of 1,1%-(pyridine-2,6-diyl)bis-
(
3-benzyl-2,3-dihydro-1H-imidazol-2-ylidene) (5)
Solvents were purified by distillation from appropri-
ate drying reagents before use. Melting points were
determined in capillary tubes on a Gallenkamp appara-
tus and are uncorrected. Elemental analyses were per-
formed on a Perkin–Elmer 2400 CHN microanalyzer.
NMR spectra were recorded on a Varian Unity 300.
Chemical shifts are expressed in parts per million (l)
relative to TMS as internal standard. The resonances of
compounds 3, 4, 6 and 7 were assigned by their cou-
pling constants, and different NOE- and Hetcor experi-
ments. FAB-MS was recorded on a VG Autospect
instrument using m-nitrobenzylalcohol as matrix.
A THF-d (0.5 ml) solution of potassium tert-butox-
ide (0.056 mmol) was transferred at −78°C to a NMR
8
tube containing 4 (0.027 mmol) After 5 min the follow-
1
ing spectra were recorded: H-NMR (l, THF-d , 0°C):
8
5.33 (s, 4H, CH ), 7.11 (d, J=1.8 Hz, 2H, H4-Im),
2
7.25–7.36 (m, 10H, Ph), 7.91 (t, J=8.1 Hz, 1H, H4-
Py), 8.20 (d, J=1.8 Hz, 2H, H5-Im), 8.29 (d, J=8.1
13
Hz, 2H, H3-Py). C{H}-NMR (l, THF-d , 0°C): 55.8
8
(CH ), 111.1(C3-Py), 117.6 (C5-Im), 120.6 (C4-Im),
2
128.3 (C4-Ph), 128.5 (C2-Ph), 129.3 (C3-Ph), 139.4
(C1-Ph), 141.0 (C4-Py), 153.2 (C2-Py), 217.4 (C2-Im).
4.1. Preparation of 2,6-bis(imidazol-1-yl)pyridine (3)
4.4. Preparation of 1,1%-(pyridine-2,6-diyl)bis-
(
3-benzylimidazole-2-thione) (6)
In a 50 ml round bottom flask, provided with a
condenser of reflux, imidazole (45 mmol), KOH (90
mmol) and TBAB (1,35 mmol) were stirred at room
temperature (r.t.) for 15 min, then 2,6-dichloropyridine
To a solution of 4 (0.7 mmol) in THF (75 ml) and
potassium tert-butoxide (1.4 mmol) was added at r.t.
The mixture was stirred for 5 min and then sulphur (1.5
mmol) was added. After 2 h the solution was filtered
and the solvent removed to give a crude product which
was purified by flash chromatography (70:1 CH Cl –
(
21 mmol) was added and the mixture was stirred for 2
h at 80°C. The residue was extracted with EtOH and
after removing the solvent the crude product was
purified by flash chromatography on silica gel
2
2
MeOH). M.p. 159–160°C (CHCl –Hexane); 77% yield.
3
1
(
AcOEt:MeOH, 10:1) to afford the compound 3 as a
H-NMR (l, CDCl ): 5.35 (s, 4H, CH ), 6.68 (d, J=2.7
3
2
white powder. M.p. 142–143°C (CHCl –Et O); 85%
Hz, 2H, H4-Im), 7.36–7.39 (m, 10H, Ph), 7.48 (d,
J=2.7 Hz, 2H, H5-Im), 8.06 (t, J=8.1 Hz, 1H, H4-
Py), 8.95 (d, J=8.1 Hz, 2H, H3-Py). C{H}-NMR (l,
3
2
1
yield. H-NMR (l, CDCl ): 7.21 (bs, 2H, H4-Im), 7.27
3
13
(
d, J=8.1 Hz, 2H, H3-Py), 7.65 (pseudot, J=1.3 Hz,
2
2
1
H, H5-Im), 7.96 (t, J=8.1 Hz, 1H, H4-Py), 8.36 (bs,
CDCl ): 51.0 (CH ), 116.3(C5-Im), 117.0 (C3-Py), 117.2
3
2
1
3
H, H2-Im). C{H}-NMR (l, CDCl ): 109.6 (C3-Py),
(C4-Im), 128.3 (C4-Ph), 128.4 (C2-Ph), 128.9 (C3-Ph),
135.3 (C1-Ph), 139.8 (C4-Py), 148.4 (C2-Py), 162.8 (C2-
Im). Anal. Calc. for C H N S : C, 65.91; H, 4.65; N,
3
16.1 (C5-Im), 131.1 (C4-Im), 134.9 (C2-Im), 142.0
(
C4-Py), 148.3 (C2-Py). Anal. Calc. for C H N : C,
11 9 5
25 21
5 2
6
3
2.56; H, 4.30; N, 33.16. Found: C, 62.45; H, 4.62; N,
2.81%.
15.37; S, 14.08. Found: C, 65.83; H, 4.61; N, 15.31; S,
14.11%.
4
1
.2. Preparation of 1,1%-(pyridine-2,6-diyl)bis(3-benzyl-
H-imidazolium) dibromide (4)
4.5. Preparation of [Ag(pbbdiy)]OSO CF (7)
2
3
To a 250 ml Schlenk tube light protected, containing
4 (0.36 mmol) a solution of potassium tert-butoxide
(0.75 mmol) in THF (75 ml) was added at 0°C. Then
silver trifluoromethanesulfonate (0.54 mmol) was added
and the mixture was stirred for 5 min. The solution was
filtered and the solvent removed to give a brown pow-
der, which was washed with 1:10 tetrahydrofuran–pen-
tane. The product was obtained as brown powder. M.p.
191–192°C (decomposition) (THFꢀPentane); 60%
In a 250ml round bottom flask, provided with a
condenser of reflux, a mixture of 3 (10 mmol) and
benzyl bromide (200 mmol) was heated at 100°C for 24
h. The reaction mixture was washed with CH Cl to
2
2
give 4 which was purified by crystallisation. M.p. 288–
1
2
89°C (EtOH–AcOEt); 78% yield. H-NMR (l,
DMSO-d ): 5.68 (s, 4H, CH ), 7.40–7.66 (m, 10H, Ph),
6
2
8
.20 (pseudot, J=1.8 Hz, 2H, H4-Im), 8.29 (d, J=8.1
Hz, 2H, H3-Py), 8.61 (t, J=8.1 Hz, 1H, H4-Py), 8.91
pseudot, J=1.8 Hz, 2H, H5-Im), 11.20 (bs, 2H, H2-
1
yield. H-NMR (l, DMSO-d ): 4.89 (bs 4H, CH ), 6.85
6
2
(
(d, J=7.3 Hz, 4H, H2-Ph), 7.07 (t, J=7.3 Hz, 4H,
H3-Ph), 7.17 (t, J=7.3 Hz, 2H, H4-Ph), 7.73 (s, 2H,
H4-Im), 7.99 (d, J=8.0 Hz, 2H, H3-Py), 8.34 (s, 2H,
1
3
Im). C{H}-NMR (l, DMSO-d ): 53.1 (CH ), 114.9
6
2
(
1
C3-Py), 120.6 (C5-Im), 124.4 (C4-Im), 129.3 (C2-Ph),
29.6 (C4-Ph), 129.7 (C3Ph), 135.0 (C1-Ph), 136.6 (C2-
13
H5-Im), 8.42 (t, J=8.0 Hz, 1H, H4-Py). C{H}-NMR