Zirconium complexes of fluorinated aryl diamides

Article abstract of DOI:10.1021/om0006559

The reaction of excess Ar^FNHLi with (ICH₂CH₂OCH₂)₂ affords the new diamines (Ar^F CH₂CH₂OCH₂)₂ (1, Ar^F = C₆F₅; 2,

Full text of DOI:10.1021/om0006559

Organometallics 2001, 20, 1153-1160
1153
Zir con iu m Com p lexes of F lu or in a ted Ar yl Dia m id es
Paul E. O’Connor, Darryl J . Morrison, Sheryl Steeves, Katherine Burrage, and
David J . Berg*
Department of Chemistry, University of Victoria, P.O. Box 3065,
Victoria, British Columbia, Canada V8W 3V6
Received J uly 31, 2000
The reaction of excess ArFNHLi with (ICH2CH2OCH2)2 affords the new diamines (ArFNH-
CH2CH2OCH2)2 (1, ArF ) C6F5; 2, ArF ) 3,5-C6H3(CF3)2) in moderate yield. Direct protonolysis
of Zr(CH2Ph)nCl4-n (n ) 2-4) or Zr[N(SiMe3)2]nCl4-n (n ) 2, 3) with 1 or 2 (1 equiv) affords
the zirconium complexes Zr(ArFNCH2CH2OCH2)2(X)(Y) (ArF ) C6F5: 3, X ) Y ) Cl; 4, X )
N(SiMe3)2, Y ) Cl; 5, X ) Cl, Y ) CH2Ph; 6, X ) Y ) CH2Ph. ArF ) 3,5-C6H3(CF3)2: 7, X )
Y ) Cl; 8, X ) Y ) CH2Ph). The structures of 1, 4, 5, and 7 were established by X-ray
crystallography with the zirconium complexes 4, 5, and 7 all adopting a monocapped trigonal
bipyramidal geometry in the solid state. However, in solution, these complexes display higher
symmetry due to rapid ligand rearrangement. The silylamido complex 4 shows restricted
rotation of the C6F5 rings in solution (∆Gq ) 49 ( 3 kJ mol-1). Abstraction of a benzyl group
from 6 by B(C6F5)3 affords {Zr[CH2OCH2CH2N(C6F5)]2(CH2Ph)}+{(PhCH2)B(C6F5)3}- (9). This
complex shows evidence for η2-benzyl coordination and does not polymerize ethylene at room
temperature. Treatment of 3 with excess MAO (500 equiv) and ethylene (1 atm, 50 °C) affords
polyethylene at a modest rate (3.2 kg mol-1 Zr h-1).
In tr od u ction
the isoelectronic yttrium alkyls Y(DAC)R, supported by
the chelating diamido macrocycle, deprotonated 4,13-
diaza-18-crown-6 (DAC2-).5,6 While these complexes
displayed interesting chemistry with alkynes, they
showed no tendency to insert alkenes into the metal-
carbon bonds. This result was attributed to electronic
factors since all of our earlier results suggested that the
DAC ligand was the steric equivalent of two C5Me5
groups.5,6 Therefore, to increase metal-carbon reactiv-
ity, we decided to decrease the number and strength of
the donors present in the ligand framework. This has
been accomplished by removing two of the four DAC
ether donors and substituting the amido nitrogens with
strongly electron-withdrawing fluorinated aryl groups
in the new ligands [ArFNCH2CH2OCH2]22- (ArF ) C6F5,
3,5-C6H3(CF3)2). In this contribution we report the
The past decade has witnessed rapid development in
the use of non-cyclopentadienyl ligand systems for group
4 organometallic chemistry.1-4 Much of this effort has
been directed at the development of new olefin polym-
erization catalysts, and a number of nitrogen-based
ligand systems have been successfully employed for this
application.2-4 Of particular note, zirconium alkyl cat-
ions supported by chelating diamido ligands have been
found to function as high activity, living polymerization
catalysts for ethylene and 1-hexene.3,4
In previous work, we reported the synthesis of a
number of zirconium dialkyls cis- and trans-Zr(DAC)-
R2, their corresponding alkyl cations Zr(DAC)R+, and
* To whom correspondence should be addressed.
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M.; Tomaszewski, R.; Xin, S.; Taylor, N. J .; Collins, S. Organometallics
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R. F.; Rogers, R. D. Organometallics 1998, 17, 382.
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Schrock, R. R. Organometallics 1998, 17, 4795. (b) Schattenmann, F.;
Schrock, R. R.; Davis, W. M. Organometallics 1998, 17, 989. (c) Schrock,
R. R.; Seidel, S. W.; Schrodi, Y.; Davis, W. M. Organometallics 1999,
18, 428. (d) Graf, D. D.; Schrock, R. R.; Davis, W. M.; Stumpf, R.
Organometallics 1999, 18, 843. (e) Flores, M. A.; Manzoni, M.;
Baumann, R.; Davis, W. M.; Schrock, R. R. Organometallics 1999, 18,
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Stumpf, R.; Davis, W. M. Organometallics 1999, 18, 3649. (g) Liang,
L.-C.; Schrock, R. R.; Davis, W. M. Organometallics 2000, 19, 2526.
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119, 3830. (i) Baumann, R.; Stumpf, R.; Davis, W. M.; Liang, L.-C.;
Schrock, R. R. J . Am. Chem. Soc. 1999, 121, 7822 (j) Schrock, R. R.;
Schattenmann, F.; Aizenberg, M.; Davis, W. M. Chem. Commun. 1998,
199. (k) Schrock, R. R.; Lee, J .; Liang, L.-C.; Davis, W. M. Inorg. Chim.
Acta 1998, 270, 353. (l) Baumann, R.; Schrock, R. R. J . Organomet.
Chem. 1998, 557, 69. (m) Schrock, R. R.; Liang, L.-C.; Baumann, R.;
Davis, W. M. J . Organomet. Chem. 1999, 591, 163.
(2) (a) Horton, A. D.; de With, J . Chem. Commun. 1996, 1375. (b)
Cloke, F. G. N. Geldbach, T. J .; Hitchcock, P. B.; Love, J . B. J .
Organomet. Chem. 1996, 506, 343. (c) Clark, H. C. S.; Cloke, F. G. N.;
Hitchcock, P. B.; Love, J . B.; Wainright, A. P. J . Organomet. Chem.
1995, 501, 333. (d) Aoyagi, K.; Gantzel, P. K.; Kalai, K.; Tilley, T. D.
Organometallics 1996, 15, 923. (e) Hermann, W. A.; Denk, M.; Albach,
R. W.; Behm, J .; Herdtweck, E. Chem. Ber. 1991, 124, 683. (f) Gibson,
V. C.; Kimberley, B. S.; White, A. J . P.; Williams, D. J .; Howard, P.
Chem. Commun. 1998, 313. (g) Male, N. A. H.; Thornton-Pett, M.;
Bochmann, M. J . Chem. Soc., Dalton, Trans. 1997, 2487. (h) Kempe,
R.; Brenner, S.; Arndt, P. Organometallics 1996, 15, 1071. (i) Tsuie,
B.; Swenson, D. C.; J ordan, R. F.; Petersen, J . L. Organometallics 1997,
16, 1392. (j) Tinkler, S.; Deeth, R. J .; Duncalf, D. J .; McCamley, A.
Chem. Commun. 1996, 2623.
(3) (a) Scollard, J . D.; McConville, D. H.; Vittal, J . J . Organometallics
1995, 14, 5478. (b) Scollard, J . D.; McConville, D. H.; Vittal, J . J .
Organometallics 1997, 16, 4415. (c) Scollard, J . D.; McConville, D. H.;
Vittal, J . J . Macromolecules 1996, 29, 5241. (d) Scollard, J . D.;
McConville, D. H. J . Am. Chem. Soc. 1996, 118, 10008. (e) Guerin, F.;
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(6) (a) Lee, L.; Berg, D. J .; Einstein, F. W.; Batchelor, R. J .
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10.1021/om0006559 CCC: $20.00 © 2001 American Chemical Society
Publication on Web 02/23/2001

1154 Organometallics, Vol. 20, No. 6, 2001
O’Connor et al.
warm to room temperature over a 1 h period and was then
refluxed overnight. The THF solvent was removed under
reduced pressure, and the residue was redissolved in diethyl
ether. Water was carefully added, and the dark red organic
phase was separated and dried over anhydrous MgSO4. After
filtration, the ether solution was reduced in volume to ca. 2
mL and transferred to a short-path distillation apparatus. The
remaining ether was removed, and the residue was heated at
120 °C (10-1 mmHg) to distill off all remaining pentafluoro-
aniline. The black tarry residue was extracted with diethyl
ether and taken to dryness. Repeated recrystallization from
hot hexane yielded very pale yellow crystals. Yield: 63%. Mp:
62-4 °C. NMR (d6-benzene): 1H δ 3.81 (br s, 2H, NH), 3.13
(m, 4H, CH2O), 3.085 (m, 4H, CH2N), 3.077 (m, 4H, CH2O);
13C{1H} (d6-benzene) δ 138.4 (d, m-arylC, 1J CF ) 249 Hz), 133.7
synthesis and structural studies on several zirconium
complexes containing these ligands. In addition, the
formation of a cationic zirconium alkyl complex and the
reactivity of these complexes as precatalysts for olefin
polymerization are discussed.
It should be pointed out that Schrock’s group has
reported closely related group 4 complexes of NON and
NSN ligand systems that possess a single ether4a,e-i,l-m
or thioether4a,d donor in the backbone, but without the
fluorinated aryl substituents on the amido nitrogen.
Many of these complexes polymerize or oligomerize
olefins and provide an interesting comparison to those
reported here.
1
(d, p-arylC, J CF ) 244 Hz), 127.3 (quat-arylC), 125.8 (d,
o-arylC, 1J CF ) 255 Hz), 70.3 (NCH2CH2O), 69.7 (OCH2CH2O),
Exp er im en ta l Section
45.8 (NCH2CH2O); 19F{1H} (d-chloroform) δ -160.3 (dd, o-
Gen er a l P r oced u r es. All manipulations were carried out
under an argon atmosphere, with the rigorous exclusion of
oxygen and water, using standard glovebox (Braun MB150-
GII) or Schlenk techniques. Tetrahydrofuran (THF), hexane,
and toluene were dried by distillation from sodium benzo-
phenone ketyl under argon immediately prior to use. Tetra-
3
4
arylF, J FF ) 22.5 Hz, J FF ) 7.5 Hz), -166.0 (br t, m-arylF,
3J FF ) 22.5 Hz), -175.2 (tt, p-arylF, J FF ) 22.5 Hz, J FF
)
3
4
7.5 Hz). High res. MS (EI) found (calcd): M+ 480.0883
(480.0896).
[CH2OCH2CH2NH(3,5-C6H3(CF 3)2)]2 (2). This compound
was prepared by the procedure outlined for 1 above using bis-
(3,5-trifluoromethyl)aniline. Yield: 40%. Mp: 58-60 °C. NMR
(d-chloroform): 1H δ 7.15 (s, 2H, p-arylCH), 6.90 (s, 4H, o-aryl-
CH), 4.58 (br s, 2H, NH), 3.77 (m, 4H, NCH2CH2O), 3.70 (s,
4H, OCH2CH2O), 3.35 (m, 4H, CH2N); 13C{1H} δ 148.5 (quat-
benzylzirconium,7 Zr[N(SiMe3)2]3Cl,8 and Zr[N(SiMe3)2]2Cl2
8
were prepared according to literature procedures. Tribenzyl-
zirconium chloride and dibenzylzirconium dichloride were
prepared from zirconium tetrachloride and benzylmagnesium
chloride by appropriate modification of the tetrabenzylzirco-
nium synthesis.7 B(C6F5)3 was a generous gift from Boulder
Scientific and was purified by stirring with Me2SiCl2 followed
by vacuum sublimation. Pentafluoroaniline, 3,5-bis(trifluoro-
methyl)aniline, 1,2-bis(2-chloroethoxy)ethane, n-butyllithium,
and MAO were obtained commercially (Aldrich) and were used
as received. 1,2-Bis(2-iodoethoxy)ethane was prepared by
refluxing 1,2-bis(2-chloroethoxy)ethane with NaI in acetone
according to a literature procedure.9
2
1
arylC), 132.4 (q, m-arylC, J CF ) 37 Hz), 123.5 (q, CF3, J CF
)
276 Hz), 112.3 (o-arylC), 110.6 (p-arylC), 70.3 (NCH2CH2O),
69.2 (OCH2CH2O), 43.3 (NCH2CH2O); 19F{1H} δ -63.0 (CF3).
High res MS (FAB) found (calcd): M++ 1 573.1419 (573.1412).
Zr [CH2OCH2CH2N(C6F 5)]2Cl2 (3). A solution of 1 (0.100
g, 0.208 mmol) in 4 mL of toluene was added to a suspension
of Zr[N(SiMe3)2]2Cl2 (0.100 g, 0.208 mmol) in 16 mL of toluene,
and the reaction mixture was heated at 110 °C for 2 days.
Complex 3 precipitated directly from the reaction mixture on
cooling and was obtained as an analytically pure powder after
washing with hexane and drying under vacuum. Alternatively,
3 can be obtained in similar yield and purity by mixing
equimolar quantities of 1 and Zr(CH2Ph)2Cl2 at room temper-
ature. Yield: 90%. Mp: 231-2 °C. NMR (d5-bromobenzene):
1H δ 4.04 (br s, 4H, NCH2CH2O), 3.84 (s, 4H, OCH2CH2O),
3.80 (br s, 4H, NCH2CH2O); 13C{1H} δ 71.5 (NCH2CH2O), 69.9
(OCH2CH2O), 53.2 (NCH2CH2O); 19F{1H} δ -148.4 (d, o-arylF,
1H (360 MHz), 13C (90.55 MHz), 19F (338.86 MHz), 29Si (71.54
MHz), 11B (115.54 MHz), and all variable-temperature NMR
spectra were recorded on a Bruker AMX-360 MHz spectrom-
eter. All deuterated solvents were dried over activated 4 Å
molecular sieves, and spectra were recorded using 5 mm tubes
fitted with a Teflon valve (Brunfeldt) at room temperature
unless otherwise specified. 1H and 13C NMR spectra were
referenced to residual solvent resonances. 19F NMR spectra
were referenced to external CCl3F, 29Si NMR spectra were
referenced to external TMS, and 11B spectra were referenced
to external BF3(OEt2) (0.1 M in CDCl3). For most compounds,
3
3J FF ) 22.4 Hz), -164.1 (t, p-arylF, J FF ) 22.4 Hz), -170.2
(br s, m-arylF). 1H NMR (d6-benzene): δ 3.58 (br s, 4H,
NCH2CH2O), 3.48 (br s, 4H, NCH2CH2O), 3.07 (s, 4H,
OCH2CH2O). Anal. Calcd for C18H12N2O2F10Cl2Zr: C, 33.76;
H, 1.89; N, 4.37. Found: C, 33.86; H, 1.96; N, 4.14. High res
MS (EI) found (calcd): M+ 637.9185 (637.9159). The quater-
nary aryl 13C resonances were not located due to the extremely
low solubility of this compound and the presence of solvent
aryl resonances.
1
proton and carbon NMR assignments were confirmed by H-
1
1H or H-13C COSY experiments. Melting points were recorded
using a Bu¨chi melting point apparatus and are not corrected.
Elemental analyses were performed by Canadian Microana-
lytical, Delta, B.C. Despite the use of cooxidants such as V2O5
and PbO2, the analytical data for most complexes were
consistently 1-3% low in carbon. This may be due to metal
carbide formation. Mass spectra were recorded on a Kratos
Concept H spectrometer using electron impact (70 eV) or FAB
methods.
[CH2OCH2CH2NH(C6F 5)]2 (1). Pentafluoroaniline (5.82 g,
31.8 mmol) was weighed into a large Schlenk flask and
dissolved with stirring in 100 mL of dry THF under argon.
The solution was cooled to -78 °C with an acetone-dry ice
bath, and 20 mL of 1.6 M n-BuLi (32 mmol) was added via
syringe. The dark red solution was stirred for 10 min, and bis-
(2-iodoethoxy)ethane (2.96 g, 8.00 mmol) was added by drop-
ping funnel over a 30 min period. The solution was allowed to
Zr [CH2OCH2CH2N(C6F 5)]2[N(SiMe3)2]Cl (4). Meth od 1:
A solution of 1 (0.100 g, 0.208 mmol) and Zr[N(SiMe3)2]3Cl
(0.126 g, 0.208 mmol) in toluene (20 mL) was placed in a
Schlenk flask sealed with a Kontes valve. The mixture was
heated at 110 °C for 3 days with stirring. After cooling, the
solvent was removed under vacuum, leaving 4 as a powder.
Recrystallization from hot toluene gave white crystals. Yield:
61%. Meth od 2: A toluene solution of NaN(SiMe3)2 (0.028 g,
0.156 mmol) was added to a suspension of 3 (0.100 g, 0.156
mmol) in toluene with stirring. The cloudy reaction mixture
was stirred overnight and filtered through Celite on a sintered
glass frit. The filtrate was concentrated and cooled to yield 4
as a white crystalline solid. Yield: 90%. Mp: 230-2 °C. NMR
(d6-benzene): 1H δ 3.74 (m, 2H, CH2), 3.57 (m, 2H, CH2), 3.23
(m, 2H, CH2), 3.09 (m, 2H, CH2), 2.72 (m, 4H, CH2), 0.32 (s,
18H, SiMe3); 13C{1H} δ 143.8 (d, arylCF, 1J CF ) 237 Hz), 137.9
(7) . Zucchini, U.; Albizatti, E.; Giannini, U. J . Organomet. Chem.
1971, 26, 357.
(8) . Andersen, R. A. J . Chem. Soc., Dalton Trans. 1980, 2010.
(9) Kulstad, S.; Malmsten, L. A. Acta Chem. Scand. B 1979, 33B,
469.
1
1
(d, arylCF, J CF ) 244 Hz), 134.5 (d, arylCF, J CF ) 272 Hz),

Zr Complexes of Fluorinated Aryl Diamides
Organometallics, Vol. 20, No. 6, 2001 1155
128.9 (quat-arylC), 72.5 (NCH2CH2O), 68.1 (OCH2CH2O), 54.0
(NCH2CH2O)), 4.2 (SiMe3); 19F{1H} δ -146.0 (br s, o-arylF),
Calcd for C36H32N2O2F12Zr: C, 51.24; H, 3.82; N, 3.32. Found:
C, 49.55; H, 3.85; N, 3.17.
3
{Zr [CH2OCH2CH2N(C6F5)]2(CH2P h )}+{(P h CH2)B(C6F5)3}-
(9). A solution of B(C6F5)3 (0.011 g, 0.020 mmol) in 0.1 mL of
CD2Cl2 was added to a precooled (-30 °C) solution of 6 (0.015
g, 0.021 mmol) in 0.4 mL of CD2Cl2 in the glovebox. The deep
orange solution was thoroughly mixed and allowed to stand
at room temperature for 10 min. The product was character-
ized in situ by NMR spectroscopy; degradation of the sample
was observed over 4 h. 1H NMR: δ 7.52 (t, 2H, m-arylH),
7.32 (t, 1H, p-arylH), 6.98 (d, 2H, o-arylH), 6.87 (t, 2H, m-
arylH), 6.79 (t, 1H, p-arylH), 6.73 (d, 2H, o-arylH), 4.54 (dt,
2H, CH2, J ) 9.5, 4.8 Hz), 4.27 (dt, 2H, CH2, J ) 9.5, 5.0 Hz),
4.17 (m, 2H, CH2), 4.04 (br t, 4H, CH2, J ) 5.0 Hz), 3.90 (m,
2H, CH2), 2.81 (s, 2H, ZrCH2), 2.77 (br s, 2H, BCH2). 13C{1H}
NMR: δ 132.7, 130.0, 129.0, 128.7, 127.3, 122.9 (arylCH), 79.3
-164.4 (t, p-arylF, J FF ) 22.2 Hz), -166.6 (br t, m-arylF,
3J FF ) 22.2 Hz). 29Si{1H} (d8-toluene): δ -4.21 ppm. Anal.
Calcd for the hemi-toluene solvate C27.5H34N3O2F10ClSi2Zr: C,
40.71; H, 4.22; N, 5.18. Found: C, 40.59; H, 4.38; N, 5.17.
Zr [CH2OCH2CH2N(C6F 5)]2(CH2P h )Cl (5). This complex
was prepared by the procedure outlined for 3 using equimolar
quantities of 1 and Zr(CH2Ph)3Cl. In this case however, large
yellow crystals of 5 were obtained by layering the mother
liquor with hexane and cooling at -30 °C. Yield: 63%. Mp:
159-63 °C. NMR (d5-bromobenzene): 1H δ 7.1-7.3 (m, 8H,
benzyl and toluene H), 6.85 (br m, 2H, benzylH), 4.01 (br m,
2H, CH2), 3.85 (br s, 2H, CH2), 3.69 (br m, 2H, CH2), 3.57 (br
s, 2H, CH2), 3.38 (br s, 2H, CH2), 3.23 (br s, 2H, CH2), 2.55 (s,
2H, CH2Zr); 13C{1H} (d6-benzene) δ 143.4 (o- or m-arylCF, 1J CF
1
1
) 254 Hz), 138.5 (o- or m-arylCF, J CF ) 254 Hz), 129.3 (o- or
(NCH2CH2O), 75.2 (ZrCH2Ph, t (gated 13C), J CH ) 138 Hz),
m-benzylC), 128.7 (o- or m-benzylC), 125.6 (quat-benzylC),
121.8 (p-benzylC), 73.6 (CH2Ph), 73.1 (NCH2CH2O), 69.8
(OCH2CH2O), 53.5 (NCH2CH2O). Assignments are tentative;
the limited solubility of this compound made it difficult to
locate the remaining quaternary aryl resonances. 19F{1H}
73.2 (OCH2CH2O), 60.8 (BCH2Ph), 52.9 (NCH2CH2O). The
quaternary aryl carbon resonances were not observable.
3
19F{1H} NMR: δ -132.0 (d, 6F, borate o-arylF, J FF ) 23.4
3
Hz), -150.4 (d, 4F, ligand o-arylF, J FF ) 23.2 Hz), -162.4
(dt, 4F, ligand m-arylF, J FF ) 22.5, 3.5 Hz), -165.0 (t, 3F,
3
NMR: δ -148.8 (br s, o-arylF), -164.0 (t, p-arylF, J FF ) 22.6
borate p-arylF, 3J FF ) 20.4 Hz), -165.4 (t, 2F, ligand p-arylF,
3
3
Hz), -164.5 (t, m-arylF J FF ) 21.9 Hz).
3J FF ) 21.6 Hz), -168.1 (t, 6F, borate m-arylF, J FF ) 19.6
Hz). 11B{1H} NMR: δ -10.9 (s).
Zr [CH2OCH2CH2N(C6F 5)]2(CH2P h )2 (6). Complex 6 was
prepared from equimolar quantities of 1 and Zr(CH2Ph)4 by
the procedure described for 3. Yield: 85%. Mp: 167-9 °C. NMR
(d5-bromobenzene): 1H δ 7.14 (t, 4H, m-arylH, 3J HH ) 7.7 Hz),
In a second experiment, a sample of 9 was prepared exactly
as above except that 0.1 mL of d8-THF was added to the
1
sample prior to recording the NMR spectra. H NMR: δ 7.00
3
6.92 (d, 4H, o-arylH, J HH ) 8.1 Hz), 6.80 (t, 2H, p-arylH,
(t, 2H, m-arylH), 6.90 (t, 2H, m-arylH), 6.81 (m, 3H, overlap-
ping o,p-arylH), 6.75 (m, 3H, o,p-arylH), 4.54 (br m, 2H, CH2),
4.49 (br m, 2H, CH2), 4.40 (br m, 2H, CH2), 4.25 (s, 2H, CH2),
4.15 (br m, 2H, CH2), 4.06 (br m, 2H, CH2), 2.80 (br s, 2H,
BCH2), 2.49 (s, 2H, ZrCH2). 13C{1H} NMR: δ 79.6 (NCH2CH2O),
3J HH ) 7.0 Hz), 3.56 (m, 4H, NCH2CH2O), 3.53 (m, 4H, NCH2-
CH2O), 2.82 (s, 4H, OCH2CH2O), 2.18 (s, 4H, CH2Ph); 13C{1H}
1
δ 147.6 (quat-arylC), 142.3 (d, arylCF, J CF ) 246 Hz), 138.0
1
1
(d, arylCF, J CF ) 251 Hz), 135.5 (d, arylCF, J CF ) 280 Hz),
128.2 (quat-arylC), 127.6 (o- or m-benzylC), 127.0 (o- or
m-benzylC), 120.6 (p-benzylC), 72.7 (CH2Ph, t (gated 13C),
1J CH ) 124 Hz), 72.0 (NCH2CH2O), 68.7 (OCH2CH2O), 52.0
(NCH2CH2O). Assignments are confirmed by 1H-13C COSY.
1
75.1 (OCH2CH2O), 73.7 (ZrCH2Ph, t (gated 13C), J CH ) 126
Hz), 53.0 (NCH2CH2O). The aryl carbon resonances occur
between 122 and 152 ppm. 19F{1H} NMR: δ -129.8 (d, 6F,
borate o-arylF), -148.5 (d, 4F, ligand o-arylF), -161.5 (t, 4F,
ligand m-arylF), -162.9 (t, 3F, borate p-arylF), -165.6 (br m,
2F, ligand p-arylF), -165.9 (br s, 6F, borate m-arylF).
Olefin P olym er iza t ion Test s. A solution of 3 (0.040 g,
0.062 mmol) in toluene (30 mL) was placed in a Schlenk flask
equipped with a Kontes valve and degassed by three freeze-
pump-thaw cycles. The solution was placed under 1 atm of
ethylene, MAO (20 mL of a 10% by wt solution in toluene, ca.
500 equiv) was added, and the sealed flask was immersed in
a 50 °C oil bath for 1 h with rapid stirring. At the end of this
period, methanol (12 mL) was added to the flask and the
precipitated solids were dried on the vacuum line. The solids
were stirred in aqueous HCl (20%) overnight, collected by
filtration, and washed with water and then hexanes. The
remaining solid was dried under vacuum to yield polyethylene
(0.199 g; rate ) 3.2 kg mol-1 Zr h-1). A blank experiment run
with only MAO produced no polyethylene under these condi-
tions.
X-r a y Cr ysta llogr a p h ic Stu d ies. Crystallographic data
for 1, 4, 5, and 7 are given in Table 1. A crystal of 1 was grown
from a saturated hexane solution at -30 °C; crystals of 4, 5,
and 7 were obtained by cooling a warm (60 °C) toluene solution
to room temperature. Crystals of 4, 5, and 7 were loaded into
glass capillaries in the glovebox while crystals of 1 were
mounted on a glass fiber in air. The crystals were transferred
to a Nonius CAD4F diffractometer equipped with Cu KR or
Mo KR radiation. The unit cells were refined using 25
reflections in the 2θ range 59-64° (4), 70-80° (5), 36-40° (1),
and 32-44° (7). Experimental densities were not determined.
From three to six standard reflections, measured at 1 h
intervals during data collection, showed less than a 2% decline
in combined intensity for 1, 5, and 7; however, the standards
for 4 decayed to 59.9% of their original intensity so a decay
correction was applied. Intensity measurements were collected
for one-half of the sphere for 1 and 5 and one-fourth of the
3
19F NMR (d6-benzene): δ -150.8 (d, o-arylF, J FF ) 21.2 Hz),
3
-164.9 (m-arylF, J FF ) 21.0 Hz), -166.6 (br t, p-arylF). 1H
3
(d6-benzene): δ 7.16 (t, 4H, m-arylH, J HH ) 7.7 Hz), 7.00 (d,
3
3
4H, o-arylH, J HH ) 8.1 Hz), 6.83 (t, 2H, p-arylH, J HH ) 7.0
Hz), 3.26 (m, 4H, NCH2CH2O), 3.18 (m, 4H, NCH2CH2O), 2.28
(s, 4H, OCH2CH2O), 2.22 (s, 4H, CH2Ph). Anal. Calcd for
C32H26N2O2F10Zr: C, 51.13; H, 3.49; N, 3.72. Found: C, 48.83;
H, 3.45; N, 3.77.
Zr [CH 2OCH 2CH 2N(3,5-C6H 3(CF 3)2)]2Cl2 (7). Complex 7
was prepared from equimolar quantities of 2 and either Zr-
[N(SiMe3)2]2Cl2 or Zr(CH2Ph)2Cl2 using the procedure described
for 3. Pale yellow crystals were obtained by slow cooling of a
hot toluene solution to room temperature. Yield: 94%. Mp:
173-5 °C. NMR (d5-bromobenzene): 1H δ 7.38 (br s, 6H, o-
and p-arylH), 3.90 (br s, 4H, OCH2CH2O), 3.73 (br m, 4H,
NCH2CH2O), 3.15 (br m, 4H, NCH2CH2O); 13C{1H} δ 153.5
2
(quat-arylC), 131.6 (q, m-arylC, J CF ) 33 Hz), 123.6 (q,
1
CF3, J CF ) 273 Hz), 118.2 (o-arylC), 113.7 (p-arylC), 75.0
(NCH2CH2O), 71.4 (OCH2CH2O), 51.8 (NCH2CH2O); 19F{1H}
δ -62.55 (CF3). Anal. Calcd for C22H18N2O2F12Cl2Zr: C, 36.07;
H, 2.48; N, 3.82. Found: C, 34.99; H, 2.46; N, 3.85.
Zr [CH2OCH2CH2N(3,5-C6H3(CF 3)2)]2(CH2P h )2 (8). Yel-
low-orange crystals of complex 8 were isolated from equimolar
quantities of 2 and Zr(CH2Ph)4 by the procedure described
for 3. Yield: 68%. Mp: 171-4 °C. NMR (d6-benzene): 1H δ
7.48 (br s, 2H, p-C6H3(CF3)2), 7.42 (br s, 4H, o-C6H3(CF3)2), 7.00
(t, 4H, m-benzylH, J ) 7.4 Hz), 6.76 (br t, 4H, o- and p-
benzylH, J ) 7.4 Hz), 2.5-3.0 (br m, 12H, CH2), 1.94
(br s, 4H, CH2Ph).; 13C{1H} δ 146.7 (quat-arylC), 132.4 (q,
2
m-arylC, J CF ) 33 Hz), 130.9 (quat-benzylC), 129.2 (o- or
m-benzylC), 128.6 (o- or m-benzylC), 124.6 (q, CF3, 1J CF ) 233
Hz), 121.4 (p-benzylC), 117.1 (o-arylC), 112.0 (p-arylC), 72.6
(CH2Ph, t (gated 13C), 1J CH ) 124 Hz), 70.7 (NCH2CH2O), 67.9
(OCH2CH2O), 50.5 (NCH2CH2O); 19F{1H} δ -62.57 (CF3). Anal.

1156 Organometallics, Vol. 20, No. 6, 2001
Ta ble 1. Su m m a r y of Cr ysta llogr a p h ic Da ta
O’Connor et al.
1
4
5
7
formula
C
18H14N2O2F10
C24H30N3O2F10ClSi2Zr‚
1/2C7H8
811.40
monoclinic
P21/ n (No. 14)
12.815(1)
18.883(2)
14.915(2)
90
103.226(9)
90
3513.3(6)
4
C25H19N2O2F10ClZr‚
1/2C7H8
742.15
C22H18N2O2F12Cl2Zr
fw
480.29
triclinic
P1h (No. 2)
7.022(3)
9.601(2)
15.121(4)
87.48(2)
77.73(2)
73.54(2)
955.1(5)
1
1.67
1.75
Mo KR, 0.7107
ambient
45
732.49
monoclinic
P21/ c (No. 14)
8.560(1)
18.381(3)
17.260(2)
90
94.166(11)
90
2708.5(6)
4
1.80
7.10
Mo KR, 0.7107
ambient
45
cryst syst
space group
a (Å)
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
triclinic
P1h (No. 2)
7.4451(6)
11.558(2)
17.514(2)
94.850(12)
94.790(9)
93.639(10)
1492.7(3)
2
1.55
47.56
Cu KR, 1.542
ambient
120
Z
F(calcd) (g cm-3
)
1.54
47.69
Cu KR, 1.542
ambient
120
µ (cm-1
λ (Å)
T
)
2θmax (deg)
no. of obsd reflns
2740
5574
4433
3807
no. of unique reflns
2497
5351
4372
3671
F000
484
0.064
0.047
1648
0.048
0.039
692
0.069
0.057
1448
0.058
0.044
Ra
b
Rw
a
b
2
R ) ∑(|Fo| - |Fc|)/∑|Fo|. Rw ) [∑w(|Fo| - |Fc| )/∑w(|Fo|)2]1/2
.
sphere for 4 and 7. After the usual data reduction procedures
(NRCVAX),10 the structures were solved using the Patterson11
or direct methods (SIR97)12 options in teXsan98.13 Structure
expansion was carried out using Fourier synthesis, and the
least-squares refinements minimized ∑w((|Fo| - |Fc|)2).14 The
criterion for inclusion of reflections was I > 2.5σ(I) for 1, I >
3.0σ(I) for 4 and 7, and I > 4.0σ(I) for 5. The weighting scheme
was determined by counting statistics using w ) 1/σ2(F) +
0.001(F2). The data were corrected for absorption and Lorentz-
polarization, and the secondary extinction coefficient was
refined in all cases. The toluene of solvation in 4 lies on a
special position so that the methyl group is disordered about
the 21 screw axis. The methyl group was modeled successfully
as half-occupancy over both sites. Similarly, 5 contains a half
molecule of toluene per formula unit. In this case, the toluene
was modeled as a rigid C7H5 group and refined isotropically
with a single group thermal parameter and occupancy factor.
The occupancy factor refined to 0.531, consistent with our
observation of half-equivalent of toluene by NMR spectroscopy.
For 7, two of the four CF3 groups were disordered. Ultimately
the best refinement was achieved by refining all atoms
anisotropically while restraining the C-F bond distances to
1.30 Å for the two disordered CF3 groups (C14/F4,F5,F6 and
C22/F10,F11,F12). The largest positive and negative peaks in
the final Fourier difference map were rather large for this
structure (1.28 and -1.09 e/Å3) and were associated with the
disordered CF3 groups. Structural plots were drawn with
ORTEP3.15
Resu lts
The fluorinated diamines 1 and 2 were prepared in
moderate yield by reaction of 1,2-bis(2-iodoethoxy)-
ethane with an excess of the aniline anion, formed by
in situ deprotonation of the commercially available
fluorinated aniline with n-BuLi (eq 1). An excess of
fluorinated aniline anion was necessary in order to
obtain acceptable yields, but it is possible to recover the
volatile anilines by short-path vacuum distillation after
quenching the reaction mixture with water. The amines
were isolated as nearly white crystals by extraction of
the tarry residue with ether and repeated recrystalli-
zation from hexanes. Crystals of 1 obtained in this
manner were suitable for X-ray diffraction (Table 1). The
solid state structure of this diamine shows a fully
extended, ladder-like backbone chain with π-stacking
between the fluorinated aryl groups of adjacent mol-
ecules (Figure 1).
(10) Larson, A.; Lee, F.; Page, Y.; Webster, M.; Charland, J .; Gabe,
E. J . NRC Solver: A Program for Crystal Structure Determination;
National Research Council of Canada, Chemistry Division: Ottawa,
1985.
(11) Beurskens, P. T.; Admiraal, G.; Beurskens, G.; Bosman, W. P.;
Garcia-Granda, S.; Gould, R. O.; Smits, J . M. M.; Smykalla, C.
ORIENT: Technical Report of the Crystallography Laboratory; Uni-
versity of Nijmegen: The Netherlands, 1992.
(12) Altomare, A.; Cascarano, M.; Giacovazzo, C.; Guagliardi, A.
SIR97. J . Appl. Crystallogr. 1993, 26, 343.
(13) teXsan for Windows: Crystal Structure Analysis Package;
Molecular Structure Corporation, 1997.
(14) Beurskens, P. T.; Admiraal, G.; Beurskens, G.; Bosman, W. P.;
de Gelder, R.; Israel, R.; Smits, J . M. M. DIRDIF94; Technical Report
of the Crystallography Laboratory; University of Nijmegen: The
Netherlands, 1994.
(15) Farrugia, L. J . ORTEP3 for Windows. J . Appl. Crystallogr.
1997, 30, 565.
Zirconium complexes containing fluorinated amide
ligands were synthesized by direct protonolysis of a
suitable zirconium precursor with amines 1 and 2 (eqs
2-4). The benzyl and silylamido zirconium derivatives,
Zr(CH2Ph)nCl4-n (n ) 2-4) and Zr[N(SiMe3)2]nCl4-n (n
) 2-3), are ideally suited to this purpose. In general,
we have found that metathesis of zirconium chlorides
with the dilithium salts of the amides produces poorer
yields and less pure materials than the protonolysis
route.5,6 However, the mixed silylamide chloride com-
plex 4 can be conveniently prepared from 3 and 1 equiv

Zr Complexes of Fluorinated Aryl Diamides
Organometallics, Vol. 20, No. 6, 2001 1157
F igu r e 1. ORTEP3 drawing15 (thermal ellipsoid 30%
probability) of diamine 1.
F igu r e 2. ORTEP3 drawing15 (thermal ellipsoid 30%
probability) of complex 4. The toluene of solvation (1/2
molecule) is omitted for clarity.
of NaN(SiMe3)2 (eq 5), presumably because the large
silylamido group prevents unwanted side reactions (for
F igu r e 3. ORTEP3 drawing15 (thermal ellipsoid 30%
probability) of complex 5. The toluene of solvation (1/2
molecule) is omitted for clarity.
In each structure, the amido nitrogens of the chelating
ligand and the silylamido (4) or benzyl (5) groups are
located in equatorial positions, while the axial sites are
occupied by the chloro group and one ether oxygen. This
arrangement, where the bulkier ligand occupies the
equatorial site, is typical of trigonal bipyramidal mixed-
ligand complexes.4c,d The other ether oxygen caps one
face of the trigonal bipyramid. The bond angles around
zirconium in the equatorial plane sum to 360.0° in both
structures, indicating that the zirconium lies in the
trigonal plane. As might be expected, the angle between
the chelating amido nitrogens is significantly com-
pressed when the other equatorial group is a bulky
silylamide (4, 104.9(3)°) versus a benzyl group (5,
121.1(2)°). In both structures, the two angles between
the chelating amido nitrogens and the other equatorial
substituent are highly asymmetric (4, 120.6(3)° and
134.5(3)°; 5, 103.4(2)° and 135.5(2)°), the wider angle
being on the side with the capping oxygen. Thus these
structures can be viewed as distortions from an octa-
hedral geometry where one oxygen is forced out of the
equatorial plane and away from the metal due to steric
crowding.
The Zr-Cl and Zr-N bond distances in 4 and 5 are
very similar to one another, while the Zr-O distances
are greater in the more crowded silylamide complex 4.
The axial Zr-O bond is nearly 0.1 Å shorter than the
Zr-O capping oxygen distance in both compounds. The
most closely related structures reported in the litera-
ture are the fac-trigonal bipyramidal Zr complexes
bearing NON-,4f NSN-,4a,d NNN-,16 and NPN-type4c
chelate ligands and the six-coordinate complexes
ZrCl2(NR2)2(THF)2 (R ) Me, Et)17 which contain trans-
example, formation of the complex with two silylamido
ligands). All of the complexes were isolated as white or
very pale yellow crystals except those containing benzyl
groups, which were yellow-orange in color. With the
exception of 4, complexes containing chloride ligands (3,
5, and 7) displayed much lower solubility than the
dibenzyl derivatives (6 and 8). While this might be taken
as evidence of bridging halide interactions between
monomeric units, we do not believe this to be the case.
The solid state structures of 5 and 7 have both been
determined (vide infra), and there is no evidence for
significant intermolecular interactions; complex 5 is in
fact distorted toward a five-coordinate structure, so it
is highly unlikely that any bridging halide interactions
persist in solution. Of further note, 3 readily gives a
monomeric molecular ion in the mass spectrum, and
while this is not definitive proof that the solution or solid
state species are monomeric in nature, it has been our
experience that this is usually the case.
The solid state structures of the mixed ligand chloro
complexes 4 and 5 were determined by X-ray crystal-
lography (Table 1). The structures are depicted in
Figures 2 and 3, while important bond distances and
angles are summarized in Table 2. Both complexes
contain a six-coordinate zirconium center in what is best
described as a capped trigonal bipyramidal geometry.

1158 Organometallics, Vol. 20, No. 6, 2001
O’Connor et al.
Ta ble 2. Selected Bon d Dista n ces (Å) a n d An gles (d eg) for Zir con iu m Com p lexes 4, 5, a n d 7a
4
5
7
Distances
Zr(1)-Cl(1)
Zr(1)-O(1)
Zr(1)-O(2)
Zr(1)-N(1)
Zr(1)-N(2)
Zr(1)-N(3)
2.461(2)
2.296(4)
2.372(5)
2.102(5)
2.131(5)
2.100(5)
Zr(1)-Cl(1)
Zr(1)-O(1)
Zr(1)-O(2)
Zr(1)-N(1)
Zr(1)-N(2)
Zr(1)-C(19)
2.431(3)
2.347(8)
2.276(7)
2.076(9)
2.076(10)
2.292(11)
Zr(1)-Cl(1)
Zr(1)-Cl(2)
Zr(1)-O(1)
Zr(1)-O(2)
Zr(1)-N(1)
Zr(1)-N(2)
2.427(2)
2.417(2)
2.263(4)
2.294(4)
2.101(5)
2.120(5)
Angles
Cl(1)-Zr(1) -O(1)
Cl(1)-Zr(1)-O(2)
Cl(1)-Zr(1)-N(1)
Cl(1)-Zr(1)-N(2)
Cl(1)-Zr(1)-N(3)
O(1)-Zr(1)-O(2)
O(1)-Zr(1)-N(1)
O(1)-Zr(1)-N(2)
O(1)-Zr(1)-N(3)
O(2)-Zr(1)-N(1)
O(2)-Zr(1)-N(2)
O(2)-Zr(1)-N(3)
N(1)-Zr(1)-N(2)
N(1)-Zr(1)-N(3)
N(2)-Zr(1)-N(3)
Zr(1)-N(1)-C(1)
Zr(1)-N(1)-C(7)
Zr(1)-N(2)-C(6)
Zr(1)-N(2)-C(13)
Zr(1)-N(3)-Si(1)
Zr(1)-N(3)-Si(2)
155.3(1)
138.7(1)
85.5(2)
90.7(2)
92.7(1)
65.9(2)
70.4(2)
99.8(2)
95.5(2)
Cl(1)-Zr(1)-O(1)
Cl(1)-Zr(1)-O(2)
Cl(1)-Zr(1)-N(1)
Cl(1)-Zr(1)-N(2)
Cl(1)-Zr(1)-C(19)
O(1)-Zr(1)-O(2)
O(1)-Zr(1)-N(1)
O(1)-Zr(1)-N(2)
O(1)-Zr(1)-C(19)
O(2)-Zr(1)-N(1)
O(2)-Zr(1)-N(2)
O(2)-Zr(1)-C(19)
N(1)-Zr(1)-N(2)
N(1)-Zr(1)-C(19)
N(2)-Zr(1)-C(19)
Zr(1)-N(1)-C(1)
Zr(1)-N(1)-C(7)
Zr(1)-N(2)-C(6)
Zr(1)-N(2)-C(13)
Zr(1)-C(19)-C(20)
129.1(2)
162.3(2)
89.4(3)
90.5(3)
87.0(3)
68.6(3)
68.9(3)
140.3(3)
79.0(4)
97.5(3)
71.9(3)
99.3(4)
121.7(4)
134.9(4)
103.3(4)
126.2(8)
120.8(7)
119.9(8)
127.6(8)
117.9(8)
Cl(1)-Zr(1)-Cl(2)
Cl(1)-Zr(1)-O(1)
Cl(1)-Zr(1)-O(2)
Cl(1)-Zr(1)-N(1)
Cl(1)-Zr(1)-N(2)
Cl(2)-Zr(1)-O(1)
Cl(2)-Zr(1)-O(2)
Cl(2)-Zr(1)-N(1)
Cl(2)-Zr(1)-N(2)
O(1)-Zr(1)-O(2)
O(1)-Zr(1)-N(1)
O(1)-Zr(1)-N(2)
O(2)-Zr(1)-N(1)
O(2)-Zr(1)-N(2)
N(1)-Zr(1)-N(2)
Zr(1)-N(1)-C(1)
Zr(1)-N(1)-C(7)
Zr(1)-N(2)-C(6)
Zr(1)-N(2)-C(15)
C(1)-N(1)-C(7)
C(6)-N(2)-C(15)
92.42(7)
91.93(13)
81.90(12)
102.5(2)
147.2(2)
166.17(12)
126.63(12)
94.4(1)
87.1(2)
67.0(2)
71.8(2)
96.3(2)
133.6(2)
69.1(2)
78.9(2)
104.8(2)
120.8(2)
134.4(2)
122.9(5)
128.0(4)
122.6(5)
123.1(4)
123.7(3)
117.9(3)
138.8(2)
72.4(2)
110.2(2)
117.9(4)
128.6(4)
115.4(4)
125.6(4)
113.3(5)
114.1(6)
a
Estimated standard deviations in parentheses.
chloro, cis-amido, and cis-tetrahydrofuran groups. In
these structures the Zr-N and Zr-C bond lengths span
the ranges 2.054(3)-2.116(2) and 2.278(2)-2.343(8) Å,
respectively.4a,c,d,f The Zr-N bond lengths in 4 and 5
(2.100(6)-2.124(7) Å) and the Zr-C bond in 5 (2.363(7)
Å) are at the long end of this range, consistent with a
more crowded six-coordinate geometry. The Zr-Cl
distances in 4 and 5 (2.462(2) and 2.431(3) Å, respec-
tively) are similar to those observed for the six-
coordinate complexes ZrCl2(NR2)2(THF)2 (2.486-2.487
Å)17 and for the axial Zr-Cl distances in the fac-tbp
structures {(t-BuN-o-C6H4)2S}ZrCl(NMe2) (2.4555(11)
Å),4d {(t-BuNCH2CH2)2PPh}ZrCl(Me) (2.5067(6) Å),4c
and the six-coordinate dimer [{(t-BuN-o-C6H4)2O}ZrCl-
(µ-Cl)]2 (2.40125(13) Å).4f
F igu r e 4. ORTEP3 drawing15 (thermal ellipsoid 30%
probability) of complex 7. The fluorines of the CF3 groups
have been omitted for clarity.
The structure of 7 was also determined by X-ray
crystallography. The structure is shown in Figure 4, and
significant bond lengths and angles are collected in
Table 2. This complex also adopts a structure that can
be viewed as a capped trigonal biypramid, although the
distortions from an octahedral geometry are noticeably
less pronounced in 7 than for 4 or 5. This is most evident
in the less asymmetric Zr-O bond lengths (∆ ) (Zr-
O
cap)-(Zr-Oaxial) ) 0.031 Å). The Zr-Cl distances are
slightly shorter in 7 than in 4 or 5, while the Zr-N
distances are essentially the same in all three com-
pounds. Not surprisingly, these observations are con-
sistent with less steric crowding in 7 than in 4 or 5.
Interestingly, 7 adopts an extended lattice structure
with π-stacking between the C6H3(CF3)2 rings of adja-
cent molecules (Figure 5). The limited solubility of 7
F igu r e 5. ORTEP3 packing diagram15 showing π-stacking
interactions between the C6H3(CF3)2 rings (shaded) in
adjacent molecules. Only one of the two chains passing
through the unit cell is shown. Fluorines of the CF3 groups
have been omitted for clarity.
may stem from the strength of these interactions since
no intermolecular interactions involving the chloro
ligands are observed.
(16) (a) Cloke, F. G. N.; Hitchcock, P. B.; Love, J . B. J . Chem. Soc.,
Dalton Trans. 1995, 25. (b) Horton, A. D.; de With, J .; van der Linden,
A. J .; van de Weg, H. Organometallics 1996, 15, 2672.
(17) Brenner, S.; Kempe, R.; Arndt, P. Z. Anorg. Allg. Chem. 1995,
621, 2021.
1
The H NMR spectra of the mixed-ligand complexes
4 and 5 show higher symmetry in solution than is

Zr Complexes of Fluorinated Aryl Diamides
Organometallics, Vol. 20, No. 6, 2001 1159
F igu r e 6. Axial-capping oxygen exchange for a six-
coordinate, capped-tbp structure.
F igu r e 8. Variable-temperature 19F{1H} NMR spectra (d5-
bromobenzene) for the ortho-F resonances of 4.
F igu r e 7. Backbone inversion of a five-coordinate inter-
mediate derived from 3 and 6-8.
observed in the crystal structure. The observation of
only six backbone CH2 resonances, rather than 12,
indicates average Cs symmetry in solution. This fact can
be accommodated by a simple shift of the ether oxygens
between the capping and axial positions such that an
average mirror plane passes through the midpoint of
the OCH2CH2O carbon-carbon bond and between the
two aryl amido groups (Figure 6). Similarly, the 1H
NMR spectra of 3, 6, 7, and 8 all show three backbone
CH2 resonances at room temperature, indicating that
a fluxional process (or processes) is also operative for
these complexes. While the solid state structures of 3,
6, and 8 are not known, its seems reasonable to
postulate that they adopt a capped trigonal bipyramidal
geometry similar to 4, 5, and 7. If this is correct, then
the structures would have no symmetry and 12 reso-
nances would be expected. Given the weak binding of
one oxygen donor evident in the solid state, it is
reasonable to assume that ether oxygen dissociation
occurs to give a five-coordinate species that undergoes
backbone inversion (Figure 7). If this process and the
axial-capping oxygen interchange depicted in Figure 6
are both fast on the NMR time scale, then average C2v
symmetry is obtained and only three backbone reso-
nances should be observed. The trigonal biyramidal
complex [{(2,6-Me2C6H3)NCH2CH2}2O]Ti(CH2Ph)2 has
a structure analogous to 4 and 5 (without the capping
oxygen), and it too undergoes a similar fluxional process,
albeit at a slower rate.4j The larger size of zirconium
compared to titanium may be responsible for the faster
rate observed here. Similarly, the complexes [{(2,6-
Me2C6H3)NCH2CH2}2O]ZrX2 (X ) NMe2 or Me) adopt
a fac-trigonal bipyramidal geometry, and they too
display an average C2v structure in solution on heating
(100 °C, X ) NMe2; 60 °C, X ) Me).4a,d While it is quite
reasonable to assume that 4 and 5 also undergo back-
bone inversion (Figure 7), it is not possible to distinguish
this possibility by NMR.
F igu r e 9. Variable-temperature 19F{1H} NMR spectra (d5-
bromobenzene) for the meta- and para-F resonances of 4
(/ marks an impurity).
The 19F NMR spectrum of 4 shows evidence for
restricted rotation of the C6F5 rings. At room temper-
ature the ortho-F resonance at δ -146.0 ppm is severely
broadened, but on cooling it decoalesces into two signals
separated by nearly 7 ppm (Figure 8). The meta-F shows
similar behavior, while the para-F remains a simple
triplet over the entire temperature range (Figure 9).
From the coalescence temperatures in Figures 8 and 9,
the activation energy for this process is calculated to
be 49 ( 3 kJ /mol.18 None of the other complexes show
any evidence for restricted rotation of the amido aryl
rings, suggesting that steric interference between the
bulky silylamido group and the aryl rings is responsible
for this effect. Restricted rotation about the N-Cipso aryl
bond has been observed for several zirconium complexes
(18) (a) The free energy of activation was calculated from the
coalescence temperature (Tc) using the equal population, two-site
exchange equation: ∆Gq ) (1.912 × 10-2)(Tc)[9.972 + log(Tc/δν)] in kJ
mol-1 where δν is the separation of the resonances in Hz at coalescence
and Tc is in K.19b The error in ∆Gq was estimated to be (3 kJ mol-1
assuming a liberal error of (3 °C in estimation of Tc. (b) Sandstrom,
J . Dynamic NMR Spectroscopy; Pergamon: London, 1982.

1160 Organometallics, Vol. 20, No. 6, 2001
O’Connor et al.
bearing diamido ligands that contain bulky 2,6-diiso-
propylphenyl groups on nitrogen.3a,e,4e,j
bipyramidal geometry. This is evident from the increas-
ing dihedral angle between the capping oxygen and the
plane containing the three equatorial ligands (7, 52.9°;
5, 59.4°; 4, 62.6°) and from the displacement of the
capping oxygen from the same plane (7, 1.46 Å; 5, 1.58
Å; 4, 1.66 Å). This is accompanied by increasing asym-
metry in the Zr-O bond lengths (∆ ) (Zr-Ocap)-(Zr-
The benzyl complexes 5, 6, and 8 do not show any of
the NMR features normally associated with η2-benzyl
bonding.19 For example, the ortho-benzyl protons do not
appear upfield of 6.7 ppm (5, 6.85; 6, 6.92; 8, 6.76 ppm),
1
and the J CH coupling constants for the benzyl CH2
groups are less than 130 Hz (6, 124 Hz). In addition,
the crystal structure of 5 shows unequivocally that this
complex possesses a η1-benzyl group (Zr-CH2-Cipso
angle ) 120.6(4)°).
Oaxial): 7, 0.031 Å; 5, 0.071 Å; 4, 0.076 Å). This effect
would appear to be primarily steric in origin, as the size
of the other equatorial ligand increases in the order Cl
(7) < CH2Ph (5) < N(SiMe3)2 (4). The observation of
hindered N-Caryl ring rotation in 4 also supports a high
degree of crowding in this complex. There does not
appear to be a large difference in steric profile between
the C6F5 and 3,5-C6H3(CF3)2 aryl groups given the small
size of fluorine and the meta-CF3 disposition. However,
since we were unable to obtain structural information
for 3 (the structural pair of 7), we cannot establish the
extent to which electronic differences between the C6F5
and 3,5-C6H3(CF3)2 ligands play a role.
Complexes 3 and 6 were examined as precatalysts for
olefin polymerization. A mixture of 3 and 500 equiv of
MAO showed modest activity for the polymerization of
ethylene (1 atm, 3.2 kg mol-1 Zr h-1) at 50 °C. Treat-
ment of dibenzyl complex 6 with 1 equiv of B(C6F5)3 in
d2-dichloromethane resulted in an orange solution,
which was inactive as a polymerization catalyst for
1-hexene or ethylene. The NMR data strongly support
benzyl abstraction20 to produce {Zr[CH2OCH2CH2N-
(C6F5)]2(CH2Ph)}+{(PhCH2)B(C6F5)3}- (9); however, it
is less clear from this evidence alone whether strong
anion coordination occurs in d2-dicloromethane solu-
tion.21 There is evidence for η2-benzyl coordination to
zirconium (1J CH ) 138 Hz for the benzyl CH2 group) in
9, although the o-benzyl protons do not appear as far
upfield as might be expected.19 Addition of d8-THF to a
d2-dichloromethane solution of 9 has little effect on the
borate anion 19F resonances, but it does result in a
Not surprisingly, given the evidence for η2-benzyl
coordination, treatment of 6 with 1 equiv of B(C6F5)3
does not produce an active catalyst for ethylene or
1-hexene polymerization. Even using 500 equiv of MAO
as initiator, 3 displays modest activity for ethylene
polymerization at 50 °C. In hindsight, this result is
consistent with Schrock’s postulate that the 12e five-
coordinate M(NON)R2 species must generate a 10e four-
coordinate, cationic metal center M(NON)R+ in order
to bind and insert hexene or ethylene.4a No olefin
polymerization activity was observed when 1 equiv of
Et2O was coordinated to the cationic metal center,
presumably because the ether base was not labile. The
ligand systems described in this work possess a second
built-in ether donor, so formation of a complex with less
than a 12e cationic metal center is unlikely. Thus, the
systems described here do not appear to be well-suited
to olefin polymerization chemistry.
1
significant change in the H chemical shift (2.41 ppm)
1
and J CH coupling constant (1J CH ) 126 Hz) associated
with the Zr-CH2Ph group. From these observations we
conclude that in noncoordinating solvents 9 most likely
exists as a weakly associated anion-cation pair with
the cation containing an η2-benzyl group (eq 6).
The fluorinated amido ligands do impart high Lewis
acidity to the metal center in these complexes. This is
demonstrated by the rapid polymerization of ethyl vinyl
ether by 322 and by η2-coordination of the benzyl group
in the cation of 9. Work is continuing to investigate the
use of these complexes as Lewis acid catalysts.
Discu ssion
The solid state structures of 7, 5, and 4, taken in that
order, show increasing distortion away from an octa-
hedron and toward a highly asymmetric capped trigonal
Ack n ow led gm en t. The support of the Natural
Sciences and Engineering Research Council of Canada
is gratefully acknowledged. The authors would like to
thank one referee for valuable comments.
(19) (a) Latesky, S. L.; McMullen, A. K.; Niccolai, G. P.; Rothwell,
I. P.; Huffman, J . C. Organometallics 1985, 4, 902. (b) Bochmann, M.;
Lancaster, S. J . Organometallics 1993, 12, 633. (c) Bochmann, M.;
Lancaster, S. J .; Hursthouse, M. B.; Malik, K. M. A. Organometallics
1994, 13, 2235. (d) J ordan, R. F.; LaPointe, R. E.; Bajgur, C. S.; Echolls,
S. F.; Willet, R. J . Am. Chem. Soc. 1987, 109, 4111.
Su p p or tin g In for m a tion Ava ila ble: Tables of atomic
coordinates, bond distances and angles, and anisotropic ther-
mal parameters for 1, 4, 5 and 7. This material is available
free of charge via the Internet at http://pubs.acs.org.
-
(20) Conversion of neutral B(C6F5)3 to a borate B(CH2Ph)(C6F5)3
is clear from the upfield shift of the 11B resonance from +60.1 to -10.9
ppm (d2-dichloromethane).
(21) It has been suggested that a ∆δm,p value of greater than 3.0
ppm is indicative for strong anion binding.16b The value observed for
9 is 3.0 ppm versus a typical free anion value of 2.6 ppm.
OM0006559
(22) Steeves, S.; Berg, D. J . Unpublished results.