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W. Tan et al. / Journal of Organometallic Chemistry 692 (2007) 5395–5402
4.2. Synthesis of the ligands
and 128.44 and 116.79 (CH of Pz, 2 · Ph, allyl), 105.18
(s, CH of Pz), 71.69, 71.58 and 71.49 (s each, 1:1:1,
@CH2, 2 · OCH2), 54.53 and 45.22 (d each, NCH2),
31.52 (d, PCH2); 31P{1H} NMR (CDCl3) d ꢀ26.75; HRMS
(APCI) calcd for C26H30N4OP (M+H+): 445.2157, found:
445.2118.
4.2.1. Synthesis of 3,3-bis(bromomethyl)oxetane (2) [10]
A mixture of pentaerythritol (12.80 g, 94.0 mmol) in
60 ml of glacial HOAc and 40% aqueous HBr (v/v, 1/5)
was refluxed for 24 h, and then 50 ml 40% aqueous HBr
and 23 ml 98% sulfuric acid were added. The resulting solu-
tion was further refluxed for 24 h. After cooling to the
ambient temperature, the mixture was separated and the
product phase was diluted with 50 ml CHCl3, washed with
water (2 · 20 ml), and dried over anhydrous potassium car-
bonate, and then filtered. All the volatiles were removed
under reduced pressure. The resultant residue was distilled
under reduced pressure to afford tribromide 1 as a colorless
liquid (21.50 g, 68%; b.p.: 130–135 ꢁC/0.3 mmHg). An eth-
anolic solution of sodium ethoxide (1.1 M, 100 ml) was
added to a mixture of 1 (37.00 g, 0.11 mol) and 150 ml eth-
anol and the resulting mixture was stirred at 80 ꢁC for
2.5 h, and then cooled to ambient temperature and filtered.
All the volatiles were removed under reduced pressure to
afford a viscous residue which was distilled in vacuum, giv-
ing dibromide 2 (16.70 g, 62%; b.p.: 62–64 ꢁC/0.3 mmHg).
4.3. Synthesis of the complexes 6–8
4.3.1. Synthesis of [Ru(g6-p-cymene)Cl2{j1(P)-
PPh2CH2C(CH2OH)(CH2Pz)2}] (6)
A mixture of [RuCl2(p-cymene)]2 (76 mg, 0.12 mmol)
and 4 (100 mg, 0.24 mmol) in 20 ml toluene was stirred at
ambient temperature for 5 h, forming red-orange precipi-
tate. All the volatiles were removed under reduced pressure
and the resultant residue was washed with diethyl ether
(3 · 10 ml) and dried in vacuo to afford complex 6 as a
dark red microcrystalline power (172 mg, 98%). M.p.:
165 ꢁC, dec. Single crystals suitable for X-ray crystallo-
graphic determination were grown from recrystallization
in pentane/CH2Cl2 (v/v, 3/1). 1H NMR (CDCl3,
400 MHz, 23 ꢁC) d 7.87 and 7.85 (dd, 2:2H, NCH of Pz),
7.69 and 7.46 (m each, 2:8H, 2 · Ph), 6.23 (t, 2H, CH of
Pz), 5.14 and 4.99 (d each, 2:2H, aromatic CH of p-cym-
ene), 3.69 (dd, 2:2H, NCH2), 3.05 (s, 2H, OCH2), 2.99 (d,
4.2.2. Synthesis of 3,3-bis(pyrazol-1-yl-methyl)oxetane (3)
[4a]
i
A solution of dibromide 2 (4.14 g, 16.9 mmol) in 30 ml
THF was added to a mixture of potassium pyrazolate
freshly prepared from the reaction of KOtBu (3.18 g,
37.3 mmol) and pyrazole (2.50 g, 37.3 mmol) in 30 ml
THF at 0 ꢁC over a period of 20 min. After warmed to
ambient temperature, the mixture was refluxed with stir-
ring for 12 h, and then cooled, filtered through Celite.
The filtrate was concentrated under reduced pressure.
The resultant residue was purified by flash silica gel column
chromatography with petroleum ether (60–90 ꢁC)/diethyl
ether (v/v, 1:1) as the eluent, affording compound 3 as a
colorless oil (3.34 g, 90%).
2H, PCH2), 2.49 (m, 1H, CH of Pr), 1.79 (s, 3H, Me),
i
0.89 (d, 6H, 2 · Me of Pr); 13C{1H} NMR (CDCl3) d
139.23 (s, N@CH), 134.22 and 133.82 (Cq, i-C of 2 · Ph),
133.24, 133.15, 132.50, 131.28, 128.79, 128.69, 109.64,
105.49, 94.62, 90.52, 85.69, 85.64, 63.24, 54.68 (d), 47.15,
30.15, 27.49 (d) 21.70, 17.45; 31P{1H} NMR (CDCl3) d
16.08 ppm; IR (KBr) cmꢀ1 m(O–H) 3436 (br). Anal. Calc.
for C33H39Cl2N4OPRu Æ 0.33CH2Cl2: C, 54.18; H, 5.41;
N, 7.58. Found: C, 54.33; H, 5.61; N, 7.49%.
4.3.2. Synthesis of [Ru(g6-p-cymene)Cl2{j1(P)-
PPh2CH2C(CH2OMe)(CH2Pz)2}] (R = Me (7);
allyl (8))
4.2.3. Synthesis of 3-(diphenylphosphanyl)-2,2-bis(pyrazol-
1-ylmethyl)propyl allyl ether (5b)
In a fashion similar to synthesis of complex 6, treatment
of [RuCl2(p-cymene)]2 with 2.0 equiv. of ligand 5a or 5b in
toluene afforded complex 7 or 8 as the product.
To a solution of 4 (0.30 g, 0.74 mmol) in 10 ml THF was
added NaH (0.03 g, 1.11 mmol) at 0 ꢁC with stirring. After
gas evolution ceased, allyl bromide (0.14 g, 1.11 mmol) in
5 ml of THF was added. The mixture was stirred at ambi-
ent temperature for 12 h, filtered through Celite and con-
centrated under reduced pressure. The resulting viscous
oil was purified by silica gel column chromatography using
petroleum ether (60–90 ꢁC)/diethyl ether (v/v, 4/1) as the
4.3.2.1. Synthesis of complex 7. A mixture of [RuCl2(p-
cymene)]2 (256 mg, 0.418 mmol) and 5a (350 mg,
0.836 mmol) in 20 ml toluene was stirred at ambient tem-
perature for 6 h afforded complex 7 (480 mg, 81%). Orange
crystals of 7 were obtained by recrystallization from dichlo-
romethane/hexane (v/v, 1/3) at ꢀ20 ꢁC. M.p.: 167 ꢁC, dec.
1H NMR (CDCl3, 400 MHz, 23 ꢁC) d 7.97 (br, 4 H), 7.64
and 7.43 (br and m each, 2:8H, 2 · Ph), 6.20 (br, 2H, CH
of Pz), 5.14 and 4.98 (d each, 2:2H, CH of p-cymene),
3.90 (dd, 2:2H, 2 · NCH2), 3.14 (d, 2H, PCH2), 2.80 (s,
3H, OCH3), 2.57 (s, 2H, OCH2), 2.43 (m, 1H, CH of
1
eluent to give 5b as a colorless liquid (0.31 g, 95%). H
NMR (CDCl3, 400 MHz, 23 ꢁC) d 7.78 and 7.64 (br each,
2:2H, CHN of Pz), 7.42 and 7.28 (m each, 4:6H, 2 · Ph),
6.24 (br, 2H, CH of Pz), 5.69 (m, 1H, CH of allyl), 5.15
and 5.11 (d each, 1:1H, CH2 of allyl), 4.37 (dd, 2:2H,
NCH2), 3.50 (d, 2H, OCH2–CH@CH2), 3.05 (s, 2H,
OCH2), 2.23 (s, 2H, PCH2); 13C{1H} NMR (CDCl3) d
139.39 (s, N@CH of Pz), 139.12 and 139.01 (s, Cq, i-C of
2 · Ph), 134.43, 133.18, 132.98, 131.86, 128.64, 128.50
i
iPr), 1.74 (s, 3H, CH3), 0.67 (d, 6H, 2 · Me of Pr);
13C{1H} NMR (CDCl3) d 139.13 (s, N@CH), 134.34 and
133.94 (Cq, i-C of 2 · Ph), 133.31, 133.22, 132.34, 130.85,
128.42, 128.32, 109.11, 105.31, 94.31, 90.66, 85.29, 72.69,