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H. Yang et al. / Polyhedron 24 (2005) 1280–1288
rotomers with a ratio of 1:1. 1H NMR (C6D6, 400 MHz):
d 7.42 (d, 4 H, J = 8.0 Hz, ArH), 7.31–7.19 (m, 6H,
ArH), 6.64 (dd, 1H, J = 19.0, 13.2 Hz, BCH), 6.57 (dd,
1H, J = 19.0, 13.2 Hz, BCH0), 6.02 (bt, 2H,
J = 13.2 Hz, alkene), 5.80–5.50 (m, 4H, alkene), 5.12–
4.91 (m, 4H, alkene), 3.68 (dt, 2H, J = 5.2, 1.7 Hz,
2.2.4. (g-1-Ethyl-2-phenyl-1H-1,2-azaborolyl)(g-penta-
methylcyclopentadienyl)zirconium(IV) dichloride (8)
A solution of lithium 1-ethyl-2-phenyl-1H-1,2-aza-
borolide (0.42 g, 2.37 mmol) in 10 mL of ether was
added to a suspension of pentamethylcyclopentadienyl-
zirconium trichloride (0.78 g, 2.34 mmol) in 10 mL of
ether at ꢀ78 ꢁC. Stirring was maintained for 12 h as
the mixture was slowly warmed to 25 ꢁC. The solvent
was removed in vacuo and the residue was washed with
pentane and dried, affording the product (0.54 g, 56%)
as a yellow powder. The product could be recrystallized
from CH2Cl2/pentane to afford yellow crystals. 1H
NMR (400 MHz, C6D6): d 7.79 (dd, J = 8.2, 1.4 Hz,
2H, ArH); 7.29 (t, J = 7.3 Hz, 2H, ArH); 7.19 (t,
J = 7.4 Hz, 1H, ArH),; 6.24 (t, J = 2.6 Hz, 1H ring
CH); 5.33 (dd, J = 4.9, 2.7 Hz, 1H, ring CH); 4.62 (dd,
J = 4.9, 2.7 Hz, 1H, ring CH); 4.06 (dq, J = 14.0,
7.0 Hz, 1H, NCH); 3.86 (dq, J = 14.0, 7.0 Hz, 1H,
NCH0); 1.77 (s, 15H, CpMe) 0.89 (t, J = 7.3 Hz, 3H,
NCH2CH3). 13C NMR (100.6 MHz): d 134.5, 128.5,
127.7, 127.5, 123.5, 114.1, 44.1, 16.8, 12.1. 11B NMR
@CCH2), 3.51 (dt, 2H, J = 5.2, 1.7 Hz, @CCH0 ), 3.12
2
(q, 2H, J = 7.1 Hz, Et), 2.93 (q, 2H, J = 7.1 Hz, Et0),
0.99 (t, 3H, J = 7.1 Hz, Et), 0.81 (t, 3H, J = 7.1 Hz,
Et0). 13C NMR (C6D6, 100.6 MHz): shows two sets of
signals. 11B NMR (C6D6, 115.5 MHz): d 39.4 HRMS
(EI, m/z): calc. for C13H1811BN (M+), 119.1532; found
119.1528. Anal. Calc. for C13H18BN: C, 78.42; H, 9.11;
N, 7.03. Found: C, 78.28; H, 8.59; N, 6.50%.
2.2.2. 1-Ethyl-2,5-dihydro-2-phenyl-1H-1,2-azaborole
(13)
A solution of 12 (17.2 g, 86.4 mmol) in 20 mL of
CH2Cl2 was added to a solution of bis (tricyclohexyl-
phosphine)benzylidene
ruthenium(IV)
dichloride
(Grubbs catalyst) (3.55 g, 4.31 mmol) in 40 mL of
CH2Cl2 at 25 ꢁC. The mixture was stirred at 25 ꢁC for
10 h after which the color had changed from purple-
red to dark brown. The solvent was removed in vacuo
giving the product (12.6 g, 85%) as a clear colorless li-
quid, bp 60 ꢁC at 0.05 torr. 1H NMR (C6D6,
400 MHz): d 7.75 (d, 2H, J = 8.0 Hz, ArH), 7.33 (t,
2H, J = 8.0 Hz, ArH), 7.25 (t, 1H, J = 8.0 Hz, ArH),
6.93 (d, 1H, J = 8.1 Hz, vinyl), 6.60 (d, 1H, J = 8.1 Hz,
vinyl), 3.51 (m, 2H, NCH2CH@), 3.26 (q, 2H,
J = 7.0 Hz, Et), 0.94 (t, 3H, J = 7.0 Hz, Et). 13C NMR
(C6D6, 100.6 MHz): d 148.5, 134.1, 132.3, 123.1, 128.9,
128.1, 127.6, 60.3 (NCH2C@), 41.4 (Et), 16.7 (Et). 11B
NMR (C6D6, 115.5 MHz): d 39.4. HRMS (EI, m/z):
Calc. for C11H1411BN (M+), 171.1219; found,
171.1224. Anal. Calc. for C11H14BN: C, 77.24; H, 8.25;
N, 8.19. Found: C, 77.83; H, 8.45; N, 7.68%.
(115.6 MHz, C6H6):
d
33.7. HRMS: Calc. for
C21H2811B35Cl2N90Zr, 465.0740. Found: 465.0740. Anal.
Calc. for C21H28BCl2N90Zr: C, 53.96; H, 6.05; N, 3.00.
Found: C, 52.52; H, 6.41; N, 2.79%.
2.2.5. 1-Ethyl-3-chlorodimethylsilyl-2,3-dihydro-2-
phenyl-1H-1,2-azaborole (15)
A solution of Me2SiCl2 (0.69 mL, 0.73 g, 5.65 mmol)
in 15 mL of ether was added dropwise to a solution of
lithium 1-ethyl-2-phenyl-1H-1,2-azaborolide (1.0 g,
5.65 mmol) in 25 mL of ether at ꢀ78 ꢁC. When the addi-
tion was complete, the mixture was warmed slowly to
25 ꢁC and stirred for 10 h. The solvent was removed un-
der reduced pressure and the residue was extracted with
pentane. The extracts were filtered through celite and
the solvent was removed in vacuo leaving the product
as an orange oil (1.38 g, 92%). 1H NMR (400 MHz,
CDCl3): d 7.40 (dd, J = 7.7, 1.8 Hz, 2H, ArH), 7.23
(m, 3H, ArH); 6.32 (dd, J = 3.8, 1.3 Hz, 1H, ViH);
5.70 (dd, J = 3.8, 2.4 Hz, 1H, ViH); 3.30 (m, 1H,
NCH); 3.12 (m, 1H, NCH0); 2.64 (br s, 1H, BCH);
0.94 (t, J = 7.1 Hz, 3H, CMe), 0.14 (s, 3H, SiMe0),
0.09 (s, 3H, SiMe0). 13C NMR (100.6 MHz, C6D6): d
139.1, 133.5 (Ph), 128.8 (Ph), 127.9 (Ph), 122.2, 41.1
(NCH2), 39 (br, BCH), 17.3 (CMe), 2.4 (SiMe), 0.2
(SiMe0). 11B NMR (115.5 MHz, C6D6): d 44.6. HRMS:
Calc. for C13H1911B35ClNSi: 263.1068. Found:
263.1078. Anal. Calc. for C13H19BClNSi: C, 59.21; H,
7.28; N, 5.31. Found: C, 59.04; H, 7.12; N, 5.46%.
2.2.3. Lithium 1-ethyl-2-phenyl-1H-1,2-azaborolide (14)
1-Ethyl-2,5-dihydro-2-phenyl-1H-1,2-azaborole (5.0 g,
29.2 mmol) was dissolved in 15 mL of ether at ꢀ78 ꢁC.
To this was added a solution of LDA (3.13 g,
29.2 mmol) in 15 mL of ether. The mixture was stirred
at ꢀ78 ꢁC for 2 h and at 25 ꢁC for 10 h. After removal
of the solvent the residue was washed with 3 · 20 mL
of pentane. The residue was dried under vacuum to give
1
the product as a light yellow powder (3.9 g, 77%). H
NMR (THF-d8, 400 MHz): d 7.51 (d, 2H, J = 8.0 Hz,
ArH), 7.05 (t, 2H, J = 8.0 Hz, ArH), 6.87 (t, 1H,
J = 8.0 Hz, ArH), 5.91 (m, 1H, H4), 5.86 (m, 1H,
H5), 4.16 (m, 1H, H3), 3.78 (q, 2H, J = 7.0 Hz, Et),
1.27 (t, 3H, J = 7.0 Hz, Et). 13C NMR (THF-d8,
100.6 MHz): d 133.9, 127.2, 123.8, 112.8, 111.9, 86.5
(br), 43.2 (Et), 19.6 (Et). 11B NMR (THF-d8,
115.5 MHz): d 29.4.
2.2.6. 1-Ethyl-3-(cyclopentadienyldimethylsilyl)-2,3-
dihydro-2-phenyl-1H-1,2-azaborole (16)
A solution of cyclopentadienyl lithium (0.16 g,
2.27 mmol) in 10 mL of THF was added slowly to