Z. Guo et al. / Journal of Organometallic Chemistry 776 (2015) 136e142
141
Table 1
The cyclotrimerization of isocyanate catalyzed by zinc compounds 1e6.
Entry Catalyst Loading (mol %) Substrate
Yield (%)
1
2
3
4
5
6
7
8
1
2
3
4
5
6
3
3
3
3
3
5
5
5
5
5
5
2.5
1
5
Phenyl isocyanate
Phenyl isocyanate
Phenyl isocyanate
Phenyl isocyanate
Phenyl isocyanate
Phenyl isocyanate
Phenyl isocyanate
Phenyl isocyanate
84.9
87.3
92.4
71.6
74.3
83.1
82.4
54.5
93.6
90.7
Fig. 6. ORTEP diagram of compound 7. Thermal ellipsoids are drawn at the 20%
probability level. Hydrogen atoms are omitted for clarity. Selected bond lengths (Å)
and bond angles (deg): Zn1eN1 2.217(3), Zn1eN2 2.139(3), Zn2eN2 2.112(3), Zn2eN3
2.231(3), Zn1eO1 2.005(2), Zn2eO1 2.008(2), Zn3eO1 1.955(2), Zn4eO1 1.965(2),
Zn3eO2 1.964(2), Zn4eO2 1.955(2), Zn5eO2 2.018(2), Zn6eO2 1.994(2), Zn5eN5
2.086(3), Zn5eN4 2.216(3), Zn6eN5 2.179(3), Zn6eN6 2.191(3); N1eZn1eN2
82.35(11), N2eZn2eN3 81.93(12), Zn1eN2eZn2 86.45(10), N4eZn5eN5 81.87(12),
N5eZn6eN6 82.87(12), Zn5eN5eZn6 86.34(11), O1eZn3eO2 88.39(9), O1eZn4eO2
88.34(9), Zn3eO1eZn4 91.57(9), Zn3eO2eZn4 91.59(9).
9
10
11
4-Chlorophenyl isocyanate
4-Methylphenyl isocyanate
4-Methoxyphenyl isocyanate 88.4
5
5
Reaction conditions: room temperature, 12 h.
{[C4H2N(2,5-CH2N(CH2)4)2]Zn(OeC6H4-4-tBu)}2 (5)
The synthesis of compound 5 was carried out following the
procedures similar to those used for the preparation of 4. The white
solid was recrystallized from a saturated hexane solution to yield
colorless crystals of 5 (0.232 g, 0.52 mmol, 52%). 1H NMR (C6D6):
7.08 (d, J ¼ 6.9, 4H, C6H4), 6.71 (d, J ¼ 6.9, 4H, C6H4), 6.52 (s, 4H,
C4H2N), 3.68 (s, 8H, eCH2e), 2.59 (s, 16H, eN(CH2)4), 1.56 (s, 16H,
eN(CH2)4), 1.29 (t, 18H, eC(CH3)3). 13C NMR (C6D6): 160.3 (C6H4),
145.4 (C6H4), 129.6 (C6H4), 125.4 (C6H4), 123.2 (C4H2N), 113.8
(C4H2N), 62.3 (eCH2e), 49.1 (eN(CH2)4), 34.9 (eC(CH3)3), 32.6
(eC(CH3)3), 27.9 (eN(CH2)4). Anal. Calc. for C48H70N6O2Zn2: C,
64.50; H, 7.89; N, 9.40. Found: C, 64.21; H, 7.93; N, 9.23.
{[C4H2N(2,5-CH2N(CH2)5)2]Zn(OeC6H4-4-tBu)}2 (6)
The synthesis of compound 6 was carried out following the pro-
cedures similar to those used for the preparation of 4. The white solid
was recrystallized from a saturated hexane solution to yield colorless
crystals of 6 (0.289 g, 0.61 mmol, 61%).1H NMR (C6D6): 7.09 (d, J ¼ 8.7,
4H, C6H4), 7.01 (d, J ¼ 8.4, 4H, C6H4), 6.79 (s, 4H, C4H2N), 3.80 (s, 8H,
eCH2e), 2.55 (s, 16H, eN(CH2)5), 1.51 (s, 16H, eN(CH2)5), 1.34 (s, 8H,
eN(CH2)5), 1.25 (t, 18H, eC(CH3)3). 13C NMR (C6D6): 158.5 (C6H4),
142.1 (C6H4), 133.8 (C6H4), 127.0 (C6H4), 117.4 (C4H2N),107.9 (C4H2N),
60.5 (eCH2e), 55.1 (N(CH2)5), 33.9 (eC(CH3)3), 31.6 (eC(CH3)3), 25.6
(N(CH2)5), 24.2 (N(CH2)5). Anal. Calc. for C52H78N6O2Zn2: C, 65.74; H,
8.28; N, 8.85. Found: C, 65.91; H, 7.96; N, 8.68.
Fig. 7. ORTEP diagram of compound 8. Thermal ellipsoids are drawn at the 20%
probability level. Hydrogen atoms are omitted for clarity. Selected bond lengths (Å)
and bond angles (deg): Zn1eN1 2.095(3), Zn1eN2 2.198(3), Zn3eN1 2.198(3), Zn3eN3
2.248(4), Zn1eO 2.045(3), Zn3eO 2.010(3), Zn2eO 1.975(3), Zn20-O 1.982(3);
N1eZn3eN3 82.53(11), N1eZn1eN2 81.91(13), Zn1eN1eZn3 85.80(13), OeZn2eO0
88.39(11), Zn2eOeZn20 91.61(11), Zn1eOeZn3 92.25(11).
Typical procedure employed for cyclotrimerization of isocyanate
A 25 mL Schlenk flask was charged with zinc compounds
(1.0 mmol) and 30 mL of diethyl ether was added, then phenyl
isocyanate (20 mmol) was added dropwise through a syringe with
stirring. The solution became cloudy gradually and the white sus-
pension was stirred at room temperature for 12 h after the addition
was completed. The resulting precipitate was isolated via filtration,
washed with diethyl ether (3 ꢂ 10 mL) and dried under vacuum to
give the corresponding isocyanurate.
(0.150 g, 1.0 mmol) in tetrahydrofuran (15 mL) at ꢁ78 ꢀC. The
resulting solution was stirred at room temperature for 1 h and dried
in vacuo to remove all the volatiles. The orange residue was
recrystallized from a saturated hexane solution to yield yellow
crystals of 4 (0.233 g, 0.59 mmol, 59%). 1H NMR (C6D6): 6.99 (d,
J ¼ 0.6, 4H, C6H4), 6.84 (d, J ¼ 0.9, 4H, C6H4), 6.69 (s, 4H, C4H2N), 3.67
(s, 8H, eCH2e), 2.18 (s, 24H, eN(CH3)2), 1.23 (t, 18H, eC(CH3)3). 13
C
NMR (C6D6): 159.1 (C6H4), 141.4 (C6H4), 133.4 (C6H4), 126.8 (C6H4),
116.7 (C4H2N), 106.7 (C4H2N), 60.5 (eCH2e), 45.9 (eN(CH3)2), 33.8
(eC(CH3)3), 31.6 (eC(CH3)3). Anal. Calc. for C40H62N6O2Zn2: C,
60.84; H, 7.91; N, 10.64. Found: C, 60.52; H, 7.67; N, 10.39.
X-ray crystallography
All crystals were coated in oil and then directly mounted on the
diffractometer under a stream of cold nitrogen gas. Single X-ray