Zr Complexes Containing TMM-Based Ligands
J. Am. Chem. Soc., Vol. 119, No. 2, 1997 351
stirred overnight. The solvent was replaced with pentane and stirred
for 3 days to give an orange solid which was collected by filtration
and washed twice with a minimum amount of cold pentane. Spectro-
scopic data are consistent with previous characterization: 1H NMR
(C6D6) δ 7.68-6.69 (m, 15H, -C6H5), 5.27 (s, 2H, (PhCH)2C), 4.01
(s, 2H, CH2Ph), 3.12 (t, 10H, OCH2), 1.15 (m, 10H, OCH2CH2).
[Cp*(TBM)ZrCl2][Li(TMEDA)2] (2). A toluene solution of Li2-
TBM(TMEDA)2 (0.529 g, 1.00 mmol) was added to a toluene
suspension of Cp*ZrCl3 (0.333 g, 1.00 mmol) and stirred for 3 h.
Evaporation was followed by a diethyl ether extraction. Solvent
removal and a pentane wash provided the product as a red solid in
71% yield (0.580 g): 1H NMR (C6D6, 25 °C) δ 1.90 (C5Me5), 2.06 (s,
8, Me2NCH2CH2NMe2), 2.09 (s, 24, Me2NCH2CH2NMe2), 6.55 (t, 3,
p-H-C6H5), 7.03 (t, 6, m-H-C6H5), 7.51 (b, 6, o-H-C6H5), C(CH-C5H6)3
signals not observed (likely to be broadened into the baseline); 1H NMR
(C6D5CD3, -30 °C) δ 3.40, 3.58, 4.16 (s, 1, C(CH-C6H5)3, ea); 13C
NMR (THF-d8) δ 141.5 (C(CH-C6H5)3), 129.0 (m-C(CH-C6H5)3), 128.4
(o-C(CH-C6H5)3), 127.3 (p-C(CH-C6H6)3), 120.9 (C(CH-C6H6)3), 120.3
(C5Me5), 58.9 (Me2NCH2CH2NMe2), 46.2 (Me2NCH2CH2NMe2), 12.3
(C5Me5), ipso carbons in the TBM ligand not observed. Anal. Calcd
for ZrC44H65Cl2LiN2: C, 64.45; H, 7.99; N, 6.85. Found: C, 64.07;
H, 7.52; N, 5.77.
[Cp(TBM)ZrCl2][Li(TMEDA)2] (3). A toluene solution of Li2-
TBM(TMEDA)2 (0.679 g, 1.28 mmol) was added dropwise to a toluene
suspension of CpZrCl3‚DME (0.453 g, 1.28 mmol) and stirred for 3 h.
After solvent removal, the residue was heated to 60 °C for 1 h while
under dynamic vacuum. A brick-red solid was left from which the
product was extracted with copious amounts of a 1:1 dimethyl ether:
benzene mixture. Solvent evaporation, followed by pentane wash, and
filtration afforded the product as a solid in 46% yield (0.445 g).
Analytically pure crystals can be obtained from slow evaporation of a
diethyl ether solution: 1H NMR (C6D6: THF-d8, 1:1) δ 7.50 (b, 6H,
o-Ph), 7.09 (t, 6H, m-Ph), 6.78 (t, 3H, p-Ph), 6.25 (s, 5H, C5H5), 2.12
(s, 8H, NCH2), 2.06 (s, 24H, NCH3), PhCH signals broad and centered
at 4.74 ppm; 13C NMR (C6D6: THF-d8, 1:1) δ 139.5 ((PhCH)3C), 129.2,
127.6, 125.6, 121.2 (C6H5CH), 114.5 (C5H5), 57.5 (NCH2), 46.0
(NCH3). Anal. Calcd for ZrC39H55Cl2LiN4: C, 62.54; H, 7.42; N, 7.48.
Found: C, 62.30; H, 7.21; N, 6.76.
[Cp(t-Bu-TBM)ZrCl2][Li(TMEDA)2] (4). To a stirring solution
of CpZrCl3‚DME (0.398 g, 1.13 mmol) in THF was added dropwise a
solution of [t-Bu-TBM][Li(TMEDA)2] (0.659 g, 1.13 mmol) in THF.
After 1 h the solvent was removed and the product extracted with a
diethyl ether:methylene chloride solvent mixture (1:1). The volume
of the solution was reduced by one-half and pentane added. Cooling
this solution for 1 h at -30 °C afforded the product as a red-orange
semisolid (62%, 0.560 g): 1H NMR (THF-d8) δ 7.33-6.85 (m, 12H,
o-Ph, m-Ph), 6.65 (t, 3H, p-Ph), 5.98 (s, 5H, C5H5), 4.34 (bs, 3H,
C(CHPh)3), 2.30 (s, 8H, NCH2), 2.15 (s, 24H, NCH3), 1.27 (s, 9H,
C(CH3)3); 13C NMR (THF-d8) δ 143.0 (C(CHPh)3), 139.3, 128.0, 126.5,
124.8, 123.3, 121.5, 120.0, 114.9 (C(CHC6H5)), 113.2 (C5H5), 58.5
(NCH2), 45.8 (NCH3), 33.4 (C(CH3)3), 31.7 (C(CH3)3). The oily nature
of this compound prevented accurate elemental analysis.
[Cp*(t-Bu-TBM)ZrCl2][Li(TMEDA)2] (5). To a stirring THF
solution of Cp*ZrCl3 (0.378 g, 1.14 mmol) was added dropwise a THF
solution of [t-Bu-TBM][Li(TMEDA)2] (0.664 g, 1.14 mmol). After 1
h the solvent was removed in Vacuo and the product extracted with
diethyl ether. Solvent removal and extensive trituration with pentane
afforded the product as a red-orange semisolid in 60% yield (0.60 g).
Small quantities of analytically pure material can be obtained from
recrystallization in pentane at -30 °C: 1H NMR (CDCl3) δ 7.28-
7.07 (m, 12H, o-Ph, m-Ph), 6.18 (t, 2H, p-Ph), 4.61 (s, 3H, C[CHPh]),
2.31 (s, 8H, NCH2), 2.18 (s, 24H, NCH3), 1.75 (s, 15H, C5(CH3)5),
1.24 (s, 9H, C(CH3)3); 13C NMR (CDCl3) δ 145.8 (C(CHPh)3), 130.4-
124.2 (C(CHC6H5)), 121.6 (C5(CH3)5), 56.9 (NCH2), 46.0 (NCH3), 31.5
(C(CH3)3), 31.0 (C(CH3)3), 11.8 (C5(CH3)5). Anal. Calcd for ZrC48-
H73Cl2LiN4: C, 65.86; H, 8.42; N, 6.40. Found: C, 65.49; H, 7.60;
N, 4.50.
washed with pentane to provide a brick-red solid (57%, 0.381 g).
Crystals for X-ray and elemental analyses can be obtained by slow
evaporation of a concentrated benzene solution: 1H NMR (THF-d8) δ
7.58-6.78 (m, 10H, C6H5), 2.11 (s, 8H, NCH2), 2.07 (s, 15H, C5(CH3)5),
1.99 (s, 24H, NCH3); 13C NMR (THF-d8) δ 146.8, 129.4-120.3 (CH2C-
(CHC6H5)2), 57.7 (NCH2), 45.8 (NCH3), 12.52 (C5(CH3)5). The TMM
inner core protons and carbons were broadened into the baseline due
to fast rotation on the NMR time scale. Anal. Calcd for ZrC38H60-
Cl2LiN4: C, 61.50; H, 8.17; N, 7.55. Found: C, 61.78; H, 8.19; N,
5.89.
[Cp*(TBM)ZrCl(CH2Ph)][Li(TMEDA)2] (9). Li2TBM(TMEDA)2
(0.400 g, 0.78 mmol) in toluene was added to a stirring solution of
Cp*ZrCl2(CH2Ph) (0.395 g, 0.78 mmol) in toluene, and the mixture
was stirred for 3 h. The resulting solids (most likely LiCl) were filtered,
the volume was reduced by approximately 80%, and pentane was added
to induce further precipitation. This slurry was cooled overnight and
the product collected by filtration as an orange microcrystalline solid
(88%). Crystallization for further (X-ray and elemental) analyses was
carried out in a mixture of CH2Cl2 with small amounts of THF. One
TMEDA of the [Li(TMEDA)2] countercation was displaced by two
THF’s during crystallization (determined by 1H NMR, elemental
analysis, and X-ray crystallography): 1H NMR (THF-d8) δ 7.20-6.61
(20H, Ph), 2.24 (d, 1H, CH2Ph, JH-H′ ) 9.84 Hz), 2.25 (s, 8H, NCH2),
2.50 (s, 15H, C5(CH3)5), 1.97 (s, 24H, NCH3), 0.96 (d, 1H, CH2Ph,
JH-H′ ) 9.84 Hz); 13C NMR (C6D6: THF-d8, 1:1) δ 158.3 (C(CHC6H5),
139.2-119.4 (C(CHC6H5), 118.1 (C5(CH3)5), 57.9 (NCH2), 45.9
(NCH3), 43.6 (Zr-CH2Ph), 12.4 (C5(CH3)5). Anal. Calcd for ZrC53-
H72ClLiN2O2: C, 71.06; H, 8.05; N, 3.10. Found: C, 71.12; H, 8.09;
N, 5.17.
[Cp*(TMM)Zr]2(µ-CH2) (10). A THF solution of Cp*Zr(CH3)2-
Cl (0.445 g, 1.52 mmol) at -30 °C was treated with 2.37 mL of (2-
methylallyl)magnesium bromide (0.64 M in THF) and stirred for 30
min. The solvent was replaced with benzene and the reaction mixture
filtered. Benzene evaporation provided the product as a red solid which
may be washed with pentane in order to remove any remaining
impurities. Recrystallization from pentane afforded analytically pure
red plates: 1H NMR (C6D6) δ 4.02 (s, µ-CH2), 2.83, 2.49, 2.42, 2.21,
1.68, 0.05 (d, (CH2)3C), 1.88 (s, 15H, C5(CH3)5); 13C NMR (C6D6, JC-H
in Hz) δ 180.1 (s, (CH2)3C), 146.5 (t, ZrCH2Zr, JC-H ) 115.7), 117.9
(s, C5(CH3)5), 77.3 (t, (CH2)2CCH2‚‚‚Zr, JC-H ) 152.6), 66.0 (t, (CH2)2-
CCH, JC-H ) 152.6), 62.4 ((CH2)2CCH2‚‚‚Zr, JC-H ) 127.2), 12.3 (q,
C5(CH3)5, JC-H ) 125.9). Anal. Calcd for ZrC29H44: C, 60.55; H, 7.73.
Found: C, 60.64; H, 7.78.
Cp*Zr(CH3)2((PhCH)2CCH2Ph) (11). Cp*Zr(CH3)2Cl (0.300 g,
1.03 mmol) was dissolved in benzene and treated with Li(PhCH)CCH2-
Ph(THF)2.5 (0.484 g, 1.03 mmol). After stirring for 10 min, the mixture
was filtered and the solvent evaporated to provide the product as a red
microcrystalline solid in 63% yield (0.340 g). 1H NMR analysis of
the product showed partial decomposition to Cp*(TBM)ZrMe within
minutes of preparation: 1H NMR (C6D6) δ 7.28-6.91 (aromatic H’s),
4.54 (s, 2H, PhCH), 3.85 (s, 2H, PhCH2), 1.62 (s, 15H, C5(CH3)5),
0.17 (s, 6H, ZrCH3); 13C NMR (C6D6) δ 139.7-118.7 (aromatic C’s),
98.6 (C5(CH3)5), 78.1 (Ph-CH), 44.6 (ZrCH3), 25.0 (PhCH2), 11.5 (C5-
(CH3)5). The thermal instability of this allylic compound prevented
elemental analysis (see text).
Cp*(TBM)ZrCH3 (12). This compound was prepared and used in
situ from the decomposition of 11 in benzene over 2 days. The
coordinated THF-d8 is displaced when THF-d8 was added to the NMR
tube in order to solubilize the product: 1H NMR (C6D6/THF-d8) δ 7.59,
7.11, 6.74 (m, 15H, [C6H5CH]3C), 4.71 (b, 3H, [C6H5CH]3C), 1.95 (s,
15H, C5(CH3)5), -0.31 (s, 3H, Zr-CH3); 13C NMR (C6D6/THF-d8) δ
145.3 (PhCH)3C), 129.8-127.6 ((C6H5CH)3C), 120.5 (C5(CH3)5), 101.5,
83.7, 71.5 ((PhCH)3C), 34.4 (Zr-CH3), 11.5 (C5(CH3)5). The thermal
instability of this compound prevented elemental analysis (see text).
Cp*(TBM)Zr(η3-CH2CtCCH3) (13). Material from the previous
procedure (0.121 g, 0.23 mmol) was dissolved in a minimum amount
of 2-butyne and allowed to stand overnight. The 2-butyne was then
removed under reduced pressure and the remaining orange solid washed
with cold pentane. These solids were dissolved in a minimum amount
of toluene, and pentane was allowed to diffuse slowly at -30 °C. After
20 h, 30 mg of crystalline product was collected. A second crop was
obtained by further cooling the mother liquor with further pentane
[Cp*(DBM)ZrCl2][Li(TMEDA)2] (6). A stirring solution of
Cp*ZrCl3 (0.300 g, 0.90 mmol) in benzene was treated dropwise with
a solution of Li2DBM(TMEDA)2 (0.410 g, 0.90 mmol) in benzene.
After stirring for 3 h the solvent was replaced with diethyl ether and
filtered in order to remove LiCl. The ether was removed and the residue