Group 4 Metal Complexes of Dialkoxide Ligands
Organometallics, Vol. 24, No. 23, 2005 5631
{ONOtol}H2 (2). Et2O (50 mL) and a few drops of CH3I were
introduced in a Schlenk flask containing magnesium turnings
(2.27 g, 97.5 mmol) under argon. After a pale yellow color
appeared, 4-bromotoluene (8.00 g, 48.8 mmol) was added
dropwise to maintain gentle ebullition of the mixture. The
mixture was stirred at room temperature for 4 h. The Grignard
solution was filtered and titrated with a 1.0 M solution of
2-butanol in toluene in the presence of o-phenantroline,
indicating a 90% yield. The solution was cooled to -5 °C, and
ethyl (N-benzylethoxycarbonylmethylamino)acetate (1.95 g, 7.0
mmol) was added by portion over 1 h. The mixture was
refluxed for 2 h, then cooled to 0 °C and quenched with an
aqueous solution of NH4Cl (20 mL of a 2.15 mol/L solution, 43
mmol). The aqueous phase was washed with ether (3 × 20
mL), and the organic phase was washed with water (2 × 10
mL). The organic phases were combined and dried over MgSO4
for 24 h. After filtration, volatiles were removed under vacuum
and the resulting white powder was recrystallized from ethanol
to yield 2 as a colorless microcrystalline powder (1.80 g, 47%).
Mp ) 177 °C. Anal. Calcd for C39H41NO2: C, 84.29; H, 7.44;
(0.170 g, 0.59 mmol). Workup afforded 4 as a white powder
(0.282 g, 86%). Anal. Calcd for C30H46N2O4Ti: C, 65.92; H, 8.48;
N, 5.13. Found: C, 66.26; H, 8.57; N, 5.08. 1H NMR (toluene-
d8, 300 MHz, 298 K): δ 7.23-7.18 (m, 10H, phenyl), 4.25 (s,
1
4H, CH2Ph), 2.83 (s, 8H, CH2NCMe2), 1.37 (s, 24H, CH3). H
NMR (toluene-d8, 300 MHz, 193 K): δ 7.35-7.20 (m, 10H,
2
2
phenyl), 4.69 (d, J ) 9.0 Hz, 2H, CHHPh), 4.12 (d, J ) 9.0
Hz, 2H, CHHPh), 3.08 (d, 2J ) 7.9 Hz, 1H, CHHNCMe2), 2.85
(d, J ) 7.9 Hz, 1H, CHHNCMe2), 2.53 (d, J ) 7.9 Hz, 1H,
CHHNCMe2), 2.35 (d, J ) 7.9 Hz, 1H, CHHNCMe2), 1.87 (s,
2
2
2
3H, CH3), 1.57 (s, 3H, CH3), 1.32 (s, 3H, CH3), 1.21 (s, 3H,
CH3). 3C{1H} NMR (toluene-d8, 75 MHz, 298 K): δ 137.1 (ipso-
C, Ph), 130.5 and 128.1 (o- and m-C, Ph), 127.3 (p-C, Ph), 81.7
(NCH2C(Me)2), 68.3 (NCH2C(Me)2), 63.6 (CH2Ph), 27.9 (CH3).
13C{1H} NMR (toluene-d8, 300 MHz, 203 K): δ 136.6 (ipso, Ph),
131.3 and 128.4 (o- and m-C, Ph), 127.7 (p-C, Ph), 81.7
(NCH2C(Me)2), 80.8 (NCH2C(Me)2), 69.3 (NCH2C(Me)2), 64.9
(NCH2C(Me)2), 63.8 (CH2Ph), 32.0 (CH3), 30.7 (2C, 2 CH3), 29.7
(CH3).
{ONOMe}2Zr (6). This complex was prepared as described
above for 3 starting from 1 (0.400 g, 1.54 mmol) and Zr(OtBu)4
(0.296 g, 0.77 mmol). Workup afforded 5 as a white powder
(0.361 g, 80%). Anal. Calcd for C30H46N2O4Zr: C, 61.08; H, 7.87;
N, 4.75. Found: C, 62.77; H, 8.42; N, 4.65. 1H NMR (THF-d8,
500 MHz): δ 7.49-7.34 (m, 5H, phenyl), 4.39 (s, 2H, CH2Ar),
2.94 (s, 4H, CH2NCMe2), 1.34 (s, 12H, CH3). 1H NMR (toluene-
d8, 500 MHz, 243 K): δ 7.48-7.18 (m, 5H, phenyl), 4.74 (d, 2J
1
N, 2.52. Found: C, 84.36; H, 7.51; N, 2.61. H NMR (CDCl3,
3
300 MHz): δ 7.17 (d, J ) 8.2 Hz, 8H, p-tol), 6.16-6.91 (m,
5H, Ph), 7.05 (d, 3J ) 8.2 Hz, 8H, p-tol), 4.28 (s, 2H, OH), 3.58
(s, 4H, NCH2C(p-tol)2), 3.32 (s, 2H, NCH2Ph), 2.30 (s, 12H,
1
3
CH3, p-tol). H NMR (toluene-d8, 500 MHz): δ 7.33 (d, J )
8.2 Hz, 8H, p-tol), 7.15-6.91 (m, 5H, Ph), 6.92 (d, 3J ) 8.2 Hz,
8H, p-tol), 4.50 (s, 2H, OH), 3.62 (s, 4H, NCH2C(tol)2), 3.34 (s,
2H, NCH2Ar), 2.12 (s, 12H, CH3, p-tol). 13C{1H} NMR (toluene-
d8, 125 MHz): δ 143.8 (ipso-C, p-tol), 138.5 (ipso-C, Ph), 135.7
(p-C, p-tol), 129.8 (o-C, p-tol), 128.8 (m-C, Ph), 128.1 (m-C,
p-tol), 127.9 (o-C, Ph), 127.0 (p-C, Ph), 77.3 (NCH2C(p-tol)2),
65.6 (NCH2C(p-tol)2), 61.8 (CH2Ph), 20.5 (CH3 p-tol).
2
) 15.0 Hz, 1H, CHHPh), 4.28 (d, J ) 15.0 Hz, 1H, CHHPh),
3.09 (d, 2J ) 13.3 Hz, 1H, CHHNCMe2), 2.96 (d, 2J ) 13.3 Hz,
1H, CHHNCMe2), 2.64 (d, 2J ) 13.3 Hz, 1H, CHHNCMe2), 2.53
(d, 2J ) 13.3 Hz, 1H, CHHNCMe2), 1.60 (s, 3H, CH3), 1.42 (s,
3H, CH3), 1.36 (s, 3H, CH3), 1.25 (s, 3H, CH3). 1H NMR
(toluene-d8, 500 MHz, 340 K): δ 7.17-7.32 (m, 5H, phenyl),
4.48 (s, 2H, CH2Ph), 2.89 (s, 4H, CH2NCMe2), 1.36 (s, 12H,
CH3). 13C{1H} NMR (toluene-d8, 125 MHz, 330 K): δ 137.74
(ipso, Ph), 131.19 (o-C, Ph), 128.1 and 127.5 (p- and m-C, Ph),
77.1 (NCH2C(Me)2), 68.4 (NCH2C(Me)2), 63.0 (CH2Ph), 32.2
(CH3).
{ONOMe}Ti(OiPr)2 (3). A solution of 1 (0.250 g, 0.879 mmol)
in toluene (3 mL) at -30 °C was added dropwise over 5 min
to a stirred solution of Ti(OiPr)4 (0.274 g, 0.879 mmol) in
toluene (2 mL) at -30 °C. Stirring was maintained for 5 h,
letting the mixture warm to room temperature. Removal of
volatiles under vacuum left a white powder, which was
recrystallized from pentane at -30 °C to give 3 as colorless
crystals (0.355 g, 87%). Anal. Calcd for C21H37O4NTi: C, 60.72;
{ONOtol}2Zr (7). This complex was prepared as described
above for 3 starting from 2 (0.100 g, 0.18 mmol) and Zr(OtBu)4
(0.034 g, 0.090 mmol). Workup afforded a white powder, which
was recrystallized from pentane at -30 °C to give colorless
crystals of 7 (0.110 g, 91%). Anal. Calcd for C78H78N2O4Zr: C,
1
H, 8.92; N, 3.37. Found: C, 60.29; H, 8.97; N, 3.42. H NMR
(toluene-d8, 500 MHz, 320 K): δ 7.22-7.16 (m, 5H, phenyl),
3
4.85 (sept, J ) 6.1 Hz, 2H, CH (OiPr)), 4.39 (s, 2H, CH2Ar),
2.84 (s, 4H, CH2NCMe2), 1.40 (d, 3J ) 6.1 Hz, 12H, CH3 (OiPr)),
1
78.15; H, 6.56; N, 2.34. Found: C, 78.38; H, 6.43; N, 2.24. H
1
3
1.30 (s, 12H, CH3). H NMR (toluene-d8, 500 MHz, 252 K): δ
NMR (toluene-d8, 500 MHz): δ 7.90 (d, J ) 7.3 Hz, 4H, o-H
7.24-7.16 (m, 5H, phenyl), 4.93 (sept, 3J ) 4.4 Hz, 2H, CH
(OiPr)), 4.40 (s, 2H, CH2Ph), 3.05 (d, 2J ) 12.7 Hz, 2H,
CHHNCMe2), 2.42 (d, 2J ) 12.7 Hz, 2H, CHHNCMe2), 1.48
(d, 3J ) 4.4 Hz, 6H, CH3 (OiPr)), 1.44 (d, 2J ) 4.4 Hz, 6H, CH3
(OiPr)), 1.42 (s, 6H, CH3), 1.24 (s, 6H, CH3). 13C{1H} NMR
(toluene-d8, 125 MHz, 320 K): δ 135.7 (ipso, Ph), 131.0 and
128.1 (o- and m-C, Ph), 127.5 (p-C, Ph), 81.4 (NCH2C(Me)2),
76.0 (CH (OiPr)), 68.7 (NCH2C(Me)2), 63.6 (CH2Ph), 31.1 (CH3
(OiPr)), 27.9 (CH3).
3
3
p-tol), 7.63 (d, J ) 7.3 Hz, 4H, o-H p-tol), 7.50 (d, J ) 7.3
3
Hz, 4H, o-H p-tol), 7.34 (d, J ) 7.1 Hz, 4H, o-H p-tol), 7.10-
7.20 (m, 10H, m-H Bz, p-H Bz and m-H ptol), 6.91 (d, 3J ) 8.0
Hz, 4H, m-H p-tol), 6.86-6.84 (m, 8H, o-H Bz and m-H p-tol),
3
2
6.82 (d, J ) 8 Hz, 4H, m-H p-tol), 4.79 (d, J ) 14.2 Hz, 2H,
CHHPh), 4.63 (d, 2J ) 14.2 Hz, 2H, CHHPh), 4.03 (d, 2J )
12.7 Hz, 2H, NCHHC(p-tol)2), 4.01 (d, 2J ) 12.7 Hz, 2H,
NCHHC(p-tol)2), 3.91 (d, J ) 12.7 Hz, 2H, NCHHC(p-tol)2),
3.75 (d, J ) 12.7 Hz, 2H, NCHHC(p-tol)2), 2.24 (s, 6H, CH3
2
2
Reaction of Zr(OtBu)4 with Diol 1: Generation of
{ONOMe}Zr(OtBu)2 (4) and {ONOMe}2Zr (6). This reaction
was carried out as described above for the synthesis of 3
starting from 1 (0.100 g, 0.39 mmol) and Zr(OtBu)4 (0.148 g,
0.39 mmol). Workup afforded a white powder, which was
recrystallized from pentane at -30 °C to give a mixture of
colorless crystals of 4 and 6 (0.172 g), in a 1:2 ratio according
to 1H NMR. Further crystallization did not allow recovering 4
in an analytically pure form. Complex 4: 1H NMR (THF-d8,
300 MHz): δ 7.49-7.34 (m, 5H, phenyl), 4.32 (s, 2H, CH2Ar),
2.87 (s, 4H, CH2NCMe2), 1.27 (s, 12H, CH3), 1.25 (s, 18H,
OtBu). 13C{1H} NMR (THF-d8, 75 MHz): δ 138.1 (ipso-C, Ph),
130.2 (o-C, Ph), 128.0 and 127.1 (p- and m-C), Ph), 78.2
(OC(CH3)2), 72.9 (C(CH3)3), 62.1 (NCH2Ph), 52.2 (NCH2), 33.0
(C(CH3)3), 31.0 (OC(CH3)2).
p-tol), 2.20 (s, 12H, 2 CH3 p-tol), 2.00 (s, 6H, CH3 p-tol). 13C-
{1H} NMR (toluene-d8, 125 MHz, 298 K): δ 149.0 (ipso-C,
p-tol), 148.3 (ipso-C, p-tol), 147.9 (ipso-C, p-tol), 147.1 (ipso-C,
p-tol), 134.9 (p-C, p-tol), 134.6 (p-C, p-tol), 134.5 (p-C, p-tol),
134.1 (ipso-C, bz), 134.0 (p-C, p-tol), 131.19 (o-C, bz), 128.7
and 128.4 (m-C, p-tol), 128.3 and 128.2 (m-C and p-C, bz), 85.4
(NCH2C(Me)2), 84.8 (NCH2C(Me)2), 66.7 (NCH2C(Me)2), 66.3
(NCH2C(Me)2), 60.3 (CH2Ph), 20.7 (CH3), 20.6 (CH3), 20.4 (2
overlapping signals, 2 CH3).
{ONOMe}Zr(CH2Ph)2 (8). Synthesis by Alkane Elimina-
tion. A solution of 1 (0.200 g, 0.795 mmol) in toluene (20 mL)
was added at -20 °C to a solution of Zr(CH2Ph)4 (0.354 g, 0.795
mmol) in toluene (20 mL). The mixture was stirred for 2 h at
room temperature. The clear solution was concentrated under
vacuum to ca. 1/4 of the initial volume and placed at -30 °C
to afford 8 as a colorless microcrystalline powder (0.380 g,
91%). Anal. Calcd for C29H37NO2Zr: C, 66.62; H, 7.13; N, 2.68.
{ONOMe}2Ti (5). This complex was prepared as described
above for 3 starting from 1 (0.300 g, 1.19 mmol) and Ti(OiPr)4