Synthesis, structures, dynamics, and olefin polymerization behavior of group 4 metal (pyCAr2O)2M(NR2)2 complexes containing bidentate pyridine-alkoxide ancillary ligands

Article abstract of DOI:10.1021/om970236k

The reaction of 2-lithiopyridine and the appropriate diarylketone followed by hydrolysis yields pyCAr₂OH pyridine-alcohols (1a, Ar = 4-^tBu-C₆H₄; 1b, pyCAr₂OH = 2-pyridyl-9-fluorenol; 1c, Ar = 3-CF₃-C₆H₄; 1d, Ar = 4-Ph-C₆H₄; 1e, Ar = 4-NEt₂-C₆H₄; 1f, pyCAr₂-OH = 1-(2-pyridyl)-1-dibenzosuberol; 1g, Ar = 3,5-(CF₃)₂-C₆H₃). The reaction of Ti(NMe₂)₄ with 2 equiv of 1a-g yields (pyCAr₂O)₂Ti(NMe₂)₂ (2a-g) and NMe₂H. The reaction of Zr-(NMe₂)₄ with 2 equiv of 1a,b,e yields (pyCAr₂O)₂Zr(NMe₂)₂ (3a,b,e), while similar reactions with 1c,d yield mixtures of (pyCAr₂O)_xZr(NMe₂)_4-x (x = 1-3) species. {pyC(3-CF₃-C₆H₄)₂O} ₃-Zr(NMe₂) (4c) and {pyC(4-NEt₂-C₆H₄)₂O}₄Zr (5e) are prepared from Zr(NMe₂)₄ and 3 equiv of 1c or 4 equiv of 1e, respectively. The reaction of Hf(NMe₂)₄ with 2 equiv of 1a,e yields (pyCAr₂O)₂Hf(NMe₂)₂ (6a,e), while reaction with 3 equiv of 1b,c yields (pyCAr₂O)₃Hf(NMe₂) (7b,c). X-ray crystallographic analyses establish that 2b, 2e, and 3a adopt distorted octahedral structures with a trans-O, cis-py, cis-amide arrangement of ligands. NMR data show that (pyCAr₂O)₂M(NMe₂)₂ complexes adopt the same structure in solution but undergo inversion of configuration at the metal with racemization barriers (ΔG? (racemization)) in the range of 12-14 kcal/mol. Treatment of (pyCAr₂O)₂M(NMe₂)₂ complexes with Al(ⁱBu)₃ and methylalumoxane (MAO) yields active, multisite ethylene polymerization catalysts.

Full text of DOI:10.1021/om970236k

3314
Organometallics 1997, 16, 3314-3323
Syn th esis, Str u ctu r es, Dyn a m ics, a n d Olefin
P olym er iza tion Beh a vior of Gr ou p 4 Meta l
(p yCAr 2O)2M(NR2)2 Com p lexes Con ta in in g Bid en ta te
P yr id in e-Alk oxid e An cilla r y Liga n d s
Il Kim, Yasushi Nishihara, and Richard F. J ordan*
Department of Chemistry, The University of Iowa, Iowa City, Iowa 52242
Robin D. Rogers
Department of Chemistry, The University of Alabama, Tuscaloosa, Alabama 35487
Arnold L. Rheingold and Glenn P. A. Yap
Department of Chemistry, The University of Delaware, Newark, Delaware 19716
Received March 24, 1997X
The reaction of 2-lithiopyridine and the appropriate diarylketone followed by hydrolysis
yields pyCAr2OH pyridine-alcohols (1a , Ar ) 4-tBu-C6H4; 1b, pyCAr2OH ) 2-pyridyl-9-
fluorenol; 1c, Ar ) 3-CF3-C6H4; 1d , Ar ) 4-Ph-C6H4; 1e, Ar ) 4-NEt2-C6H4; 1f, pyCAr2-
OH ) 1-(2-pyridyl)-1-dibenzosuberol; 1g, Ar ) 3,5-(CF3)2-C6H3). The reaction of Ti(NMe2)4
with 2 equiv of 1a -g yields (pyCAr2O)2Ti(NMe2)2 (2a -g) and NMe2H. The reaction of Zr-
(NMe2)4 with 2 equiv of 1a ,b,e yields (pyCAr2O)2Zr(NMe2)2 (3a ,b,e), while similar reactions
with 1c,d yield mixtures of (pyCAr2O)xZr(NMe2)4-x (x ) 1-3) species. {pyC(3-CF3-C6H4)2O}3-
Zr(NMe2) (4c) and {pyC(4-NEt2-C6H4)2O}4Zr (5e) are prepared from Zr(NMe2)4 and 3 equiv
of 1c or 4 equiv of 1e, respectively. The reaction of Hf(NMe2)4 with 2 equiv of 1a ,e yields
(pyCAr2O)2Hf(NMe2)2 (6a ,e), while reaction with 3 equiv of 1b,c yields (pyCAr2O)3Hf(NMe2)
(7b,c). X-ray crystallographic analyses establish that 2b, 2e, and 3a adopt distorted
octahedral structures with a trans-O, cis-py, cis-amide arrangement of ligands. NMR data
show that (pyCAr2O)2M(NMe2)2 complexes adopt the same structure in solution but undergo
inversion of configuration at the metal with racemization barriers (∆Gq (racemization)) in
the range of 12-14 kcal/mol. Treatment of (pyCAr2O)2M(NMe2)2 complexes with Al(iBu)3
and methylalumoxane (MAO) yields active, multisite ethylene polymerization catalysts.
Ch a r t 1
In tr od u ction
Recently, we described the synthesis of new group 4
metal alkyl complexes of the general form (Ox)2MR2 and
(pyCR2O)2MR2 which contain quinolinolato or pyridine-
alkoxide ancillary ligands (Chart 1).1 These species
adopt chiral C2-symmetric structures with a trans-O,
cis-pyridine, cis-alkyl ligand arrangement but undergo
inversion of configuration at the metal (i.e., Λ/∆ isomer-
ization) on the NMR time scale. The corresponding
mono(alkyl) (Ox)2MR+ and (pyCR2O)2MR+ cations were
also prepared and are active catalysts for the polymer-
ization of ethylene and, in some cases, R-olefins. These
species adopt distorted square pyramidal structures
which are stereorigid in some cases and in which the
ligand arrangement is dictated by the π-donor proper-
ties of the alkoxide ligands (Chart 1). It is of interest
to investigate the influence of the pyCR2O- ligand
structure on the stereochemical rigidity and reactivity
of (pyCR2O)2MR2 and (pyCR2O)2MR+ species in order
to eventually develop stereoselective catalysts.
In other work, we have shown that chiral ansa-
metallocene amide complexes chCp2M(NR2)2, such as
rac-(ethylenebis(tetrahydroindenyl))Zr(NMe2)2 and rac-
Me2Si(indenyl)2Zr(NMe2)2, may be prepared efficiently
by amine elimination reactions of M(NR2)4 complexes
and appropriate ansa-cyclopentadiene reagents.2 These
species are converted to chCp2M(R)+ cations, which are
X Abstract published in Advance ACS Abstracts, J une 15, 1997.
(1) (a) Bei, X.; Swenson, D. C.; J ordan, R. F. Organometallics 1997,
16, 3282. This paper contains an extensive listing of references dealing
with other recent studies of non-Cp2M olefin polymerization catalysts.
(b) Tsukahara, T.; Swenson, D. C.; J ordan, R. F. Organometallics 1997,
16, 3303. (c) Tsukahara, T.; Lubben, T.; Swenson, D. C.; Young, V. G.,
J r.; J ordan, R. F. Manuscript in preparation.
S0276-7333(97)00236-7 CCC: $14.00 © 1997 American Chemical Society

Group 4 Metal (pyCAr2O)2M(NR2)2 Complexes
Organometallics, Vol. 16, No. 15, 1997 3315
active for olefin polymerization, via alkylation with AlR3
reagents and subsequent reaction with MAO, B(C6F5)3,
+
+
HNR3 reagents, or CPh3 reagents.3 The simplicity
and success of this approach to metallocene catalysis
suggested that a similar strategy would facilitate the
investigation of structure/reactivity relationships in
(pyCR2O)2MR2 and (pyCR2O)2MR+ systems. Here, we
describe the application of this strategy to group 4 metal
(pyCAr2O)2M(NMe2)2 complexes. The specific objectives
of this study were to develop efficient synthetic routes
to (pyCAr2O)2M(NR2)2 complexes and to determine the
structures and configurational stability of these species.
Initial efforts to activate these compounds for olefin
polymerization are also described.
Similarly, the reactions of Zr(NMe2)4 with 2 equiv of
1a ,b,e in toluene or benzene produce (pyCAr2O)2Zr-
(NMe2)2 complexes 3a ,b,e which are isolated as yellow
crystalline solids in high yields (eq 3). However, the
Resu lts
Liga n d Syn th esis. Pyridine-alcohols 1a -g were
prepared by addition of 2-lithiopyridine to the appropri-
ate ketone, followed by aqueous workup, using the
approach developed by Holm for 1a (eq 1).4 These
reaction of Zr(NMe2)4 with the more acidic pyridine
alcohol 1c in benzene or methylene chloride yields a
mixture of species assigned as (pyCAr2O)xZr(NMe2)4-x
1
(x ) 1-3) on the basis of H NMR data. The reaction
of Zr(NMe2)4 with 2 equiv of 1d yields a similar mixture
of products. The tris(ligand) species (pyCAr2O)3Zr-
(NMe2) (4c) was prepared cleanly by reaction of Zr-
(NMe2)4 with 3 equiv of 1c (eq 4). A tetrakis(ligand)
complex (pyCAr2O)4Zr (5e) was prepared by the reaction
of Zr(NMe2)4 with 4 equiv of 1e (eq 5), but this species
was not studied extensively.
compounds are isolated as sharp-melting white to tan
crystalline solids following recrystallization. The use
of symmetric ketones yields symmetric pyCR2OH alco-
hols, which in turn simplifies the stereochemical pos-
sibilities for metal complexes.1b
Am in e Elim in a tion Rea ction s. The reactions of Ti-
(NMe2)4 with 2 equiv of 1a -g proceed rapidly at room
temperature in toluene or benzene to afford NMe2H and
bis(ligand) complexes (pyCAr2O)2Ti(NMe2)2 2a -g in
high yield (eq 2). Complexes 2 were isolated as analyti-
cally pure crystalline solids by crystallization from CH2-
Cl2/toluene, except for the fluorinated derivative 2c
which was obtained as an oil. The characterization of
these compounds is discussed below.
The reactivity of Hf(NMe2)4 with pyridine-alcohols
1 parallels that of Zr(NMe2)4. The reaction of Hf(NMe2)4
with 2 equiv of 1a or 1e in toluene or benzene yields
the bis(ligand) complexes (pyCAr2O)2Hf(NMe2)2 6a ,e
cleanly (eq 6), while reactions with 2 equiv of 1b or 1c
yield mixtures of products. The tris(ligand) species
(2) (a) Diamond, G. M.; Rodewald, S.; J ordan, R. F. Organometallics
1995, 14, 5. (b) Diamond, G. M.; J ordan, R. F.; Petersen, J . L. J . Am.
Chem. Soc. 1996, 118, 8024. (c) Diamond, G. M.; J ordan, R. F.;
Petersen, J . L. Organometallics 1996, 15, 4030. (d) Christopher, J . N.;
Diamond, G. M.; J ordan, R. F.; Petersen, J . L. Organometallics 1996,
15, 4038. (e) Diamond, G. M.; J ordan, R. F.; Petersen, J . L. Organo-
metallics 1996, 15, 4045. (f) Christopher, J . N.; J ordan, R. F.; Petersen,
J . L.; Young, V. G., J r. Organometallics 1997, 16, 3044.
(3) Kim, I.; J ordan, R. F. Macromolecules 1996, 29, 489.
(4) Schultz, B. E.; Gheller, S. F.; Muetterties, M. C.; Scott, M. J .;
Holm, R. H. J . Am. Chem. Soc. 1993, 115, 2714.
(pyCAr2O)3Hf(NMe2) 7b,c were prepared by reaction of

3316 Organometallics, Vol. 16, No. 15, 1997
Kim et al.
Ch a r t 2
F igu r e 1. Molecular structure of {9-(2-pyridyl)-9-fluor-
enolato}2Ti(NMe2)2 (2b).
Hf(NMe2)4 with 3 equiv of 1b,c (eq 7). Complexes 6a ,e
and 7b,c were isolated as yellow solids.
Isolated (pyCAr2O)xM(NMe2)4-x (x ) 2,3) complexes
appear to be stable toward ligand redistribution in CH2-
Cl2 or aromatic solvents at ambient temperature. Thus,
the formation of product mixtures in some of the
reactions described above results from comparable rates
of reaction of the pyridine-alcohols 1 with (pyCAr2O)2M-
(NMe2)2, M(NMe2)4, and/or (pyCAr2O)M(NMe2)3. In
general, less selectivity for the desired (pyCAr2O)2M-
(NMe2)2 species is observed in reactions of Zr(NMe2)4
and Hf(NMe2)4 with the more acidic pyridine-alcohols.
Str u ctu r a l P ossibilities for (p yCAr 2O)2M(NMe2)2
Com p lexes. Five idealized octahedral structures are
possible for (pyCAr2O)2M(NMe2)2 complexes, A-E (Chart
2). In the C2-symmetric structure A, the two pyridine-
alkoxide ligands and the two amide ligands are equiva-
lent but the two Ar groups on each pyridine-alkoxide
ligand are inequivalent. This structure is expected to
be favored because the short M-O bonds are trans to
each other, the strong trans-influence amide groups are
trans to the weak donor pyridine ligands, and the
alkoxide oxygens can participate in O-M π-bonding
with different metal d orbitals.1,5 The symmetry prop-
erties of B are identical to those of A; however, B should
be disfavored by the cis orientation of the short M-O
bonds and because the alkoxides must share a single
metal d orbital for O-M π-donation. Structure C is of
lower symmetry and contains two inequivalent pyri-
dine-alkoxide and amide ligands; in this case, all four
Ar groups are inequivalent. Structures D and E are of
higher symmetry, and in each case, the four Ar groups
are equivalent. Isomers D and E should be disfavored
by the trans arrangement of the amide ligands, and E
is also disfavored because only a single metal d orbital
can participate in O-M π-bonding in this structure.
Solid Sta te Str u ctu r es of 2b, 2e, a n d 3a . As a
variety of isomers are possible for (pyCAr2O)2M(NMe2)2
complexes, X-ray crystallographic analyses of represen-
tative examples were performed to probe for general
structural trends and to determine the bonding proper-
F igu r e 2. Molecular structure of {pyC(4-NEt2-C6H4)2O}2-
Ti(NMe2)2 (2e).
F igu r e 3. Molecular structure of {pyC(4-tBu-C6H4)2O}2-
Zr(NMe2)2 (3a ).
ties of pyCAr2O- ligands in early metal systems. The
molecular structures of 2b, 2e, and 3a are shown in
Figures 1-3, and crystallographic data and key metrical
parameters are summarized in Tables 1 and 2. All
three complexes adopt a distorted octahedral structure
of type A, with a trans-alkoxide, cis-pyridine, cis-amide
ligand arrangement. In these approximately C2-sym-
metric structures, one aryl group on each pyCAr2O-
ligand points over (under) an amide ligand. The distor-
tions from idealized octahedral geometry arise from the
acute bite angle of the bidentate pyCAr2O- ligands. This
bite angle is ca. 73° in 2b and 2e and 68° in 3a .
The structures of titanium complexes 2b and 2e are
very similar; minor differences in bond angles are
observed, which can be traced to the fact that the Ar
substituents in 2b are tied back in the fluorene ring
system. The Ar-C-Ar angles in 2b (C(7)-C(6)-C(18),
101.9(8)°; C(25)-C(24)-C(36), 100.7(8)°) are 10° smaller
(5) Kepert, D. L. In Progress in Inorganic Chemistry; Lippard, S.
L., Ed.; J ohn Wiley & Sons: New York, 1977; Vol. 23, Chapter 1.

Group 4 Metal (pyCAr2O)2M(NR2)2 Complexes
Organometallics, Vol. 16, No. 15, 1997 3317
Ta ble 1. Su m m a r y of Cr ysta llogr a p h ic Da ta
compound
empirical formula
fw
2b
2e‚toluene
3a ‚0.5NMe2H
C56H72N4O2Zr‚0.5NMe2H
966.81
C
40H36N4O2Ti
C56H76N8O2Ti‚C7H8
652.63
1033.28
cryst size (mm)
color/shape
space group
a (Å)
b (Å)
c (Å)
0.10 × 0.10 × 0.40
orange/plate
Pna21
17.6747(4)
22.5590(6)
11.3732(2)
0.15 × 0.30 × 0.40
orange/fragment
P21/n
13.4825(2)
17.9211(3)
27.4775(1)
97.791(1)
6099.08(14)
4
0.3 × 0.3 × 0.3
colorless/fragment
P21/n
13.095(5)
17.087(7)
26.860(10)
90.95(3)
6010(4)
â (deg)
V (Å3)
4534.8(2)
4
Z
4
temp (K)
293
293
296
diffractometer
radiation, λ
monochromator
2θ range (deg)
data collected h, k, l
total no. of reflns collected
no. of unique reflns
Rint
Siemens SMART, CCD
Mo KR, 0.710 73 Å
graphite
2.92 < 2θ < 46.70
-13 to 19, -25 to 25, -12 to 12
17 298
6165
0.0606
Siemens SMART, CCD
Mo KR, 0.710 73 Å
graphite
2.78 < 2θ < 46.70
-13 to 15, -19 to 10, -28 to 28
23 505
Siemens P4
Mo KR, 0.710 73 Å
graphite
4.0 < 2θ < 45.0
-14 to 14, +18, +28
7944
8697
0.0476
7760
no. of obs reflns, criterion
4598, I > 2σ(I)
6259, I > 2σ(I)
3122, F > 5σ(F)
µ, cm-1
2.19
1.87
2.21
abs corr factors (min/max)
abs corr method
structure soln
refinement
1.051/1.436
ψ scans
none applied
none applied
direct methods
direct methods
direct methods
FMLS on F2;a non-H anisotropic;
FMLS on F2;a non-H anisotropic;
FMLS on F;d N,O,Zr anisotropic;
C isotropic; H calculated
R(F) ) 0.0909e
H calculated
H calculated
R1 (I > 2σ(I))
0.1274b
0.0707b
wR2 (I > 2σ(I)
0.3162c
0.1863c
R(wF) ) 0.1249e
0.65
max resid density (e/Å3)
1.28
0.661
a
b
2
SHELXTL, ver 5; Siemens Analytical X-ray Instruments, Inc.: Madison, WI. R1 ) ∑(|Fo| - |Fc|)/∑Fo. c wR2 ) {[∑w(Fo - Fc2)2]/
[∑w(Fo2)2]}1/2
.
SHELXTL PLUS (4.2); Siemens Analytical X-Ray Instruments, Inc.: Madison, WI. e F > 5σ(F); R(F)) ∑∆/∑Fo; R(wF) )
d
∑∆w1/2/∑(Fow1/2); ∆ ) |(Fo - Fc)|.
Ta ble 2. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for 2b, 2e, a n d 3a
orbital available for N-Ti π-bonding. Thus, in these
six-coordinate complexes, the four ligand π-donor orbit-
als compete for π-bonding with three metal d acceptor
orbitals and partial Ti-O and Ti-Namide π-bonding is
expected. Consistent with this analysis, the Ti-O
distances in 2b and 2e (average 1.910(4) Å) are shorter
than the Ti-O σ-bond distance predicted on the basis
of covalent radii (ca. 1.99-2.05 Å)6 but longer than Ti-O
distances observed in more highly electron-deficient Ti-
(IV) alkoxides; e.g., TiCl2(O-2,6-Ph2-C6H3)2 (1.73 Å),7
[TiCl2(OPh)]2(µ-OPh)2 (terminal Ti-O 1.75 Å),8 Ti{O-
2-tBu-C6H4}4 (1.78 Å),9 and [Ti(CH2Ph)2(OEt)]2(µ-OEt)2
(terminal Ti-O 1.84 Å).10 Similarly, the Ti-Namide
distances in 2b and 2e (average 1.928(7) Å) are shorter
than the predicted Ti-N σ-bond distance (ca. 2.02-2.07
Å)6 but longer than those observed for four-coordinate
Ti(IV) amides; e.g., Ti{O-2,4,6-(tBu)3-C6H2}2(NMe2)2
(average 1.88 Å),11 CpFe(CO)2Ti(NMe2)3 (average 1.88
Å),12 and Ti(O-2,6-Ph2-C6H3)2(NHPh)2 (average 1.88
Å).13,14
2b
2e
3a
M-O(1)
M-O(2)
M-N(1)
M-N(2)
M-N(3)
M-N(4)
1.909(6)
1.917(6)
2.312(7)
2.315(8)
1.915(8)
1.933(8)
1.906(2)
1.908(2)
2.313(3)
2.282(3)
1.930(3)
1.932(3)
2.027(8)
2.038(9)
2.452(11)
2.415(11)
2.055(14)
2.089(13)
O(1)-M-O(2)
N(1)-M-N(3)
N(2)-M-N(4)
O(1)-M-N(1)
O(1)-M-N(2)
O(1)-M-N(3)
O(1)-M-N(4)
O(2)-M-N(1)
O(2)-M-N(2)
O(2)-M-N(3)
O(2)-M-N(4)
N(1)-M-N(2)
N(2)-M-N(3)
N(3)-M-N(4)
N(1)-M-N(4)
M-O(1)-C
149.8(3)
165.2(3)
167.2(3)
73.5(3)
86.1(3)
91.8(3)
106.5(3)
86.0(3)
73.2(3)
108.1(3)
94.2(3)
93.7(3)
86.4(3)
95.6(4)
87.6(3)
128.7(5)
128.3(6)
157.25(10)
161.36(13)
162.31(13)
72.39(10)
89.20(10)
89.23(12)
105.16(13)
91.34(10)
72.97(10)
105.37(13)
90.43(13)
83.88(10)
93.03(12)
97.4(2)
150.6(4)
157.3(5)
157.3(4)
68.4(4)
88.9(4)
90.1(5)
109.8(4)
89.4(4)
68.0(4)
107.9(5)
89.9(4)
80.9(4)
91.8(5)
100.7(5)
93.8(4)
132.0(8)
132.2(8)
90.60(13)
131.0(2)
130.0(2)
The pyridine-alkoxide chelate rings in 2b and 2e are
flat and do not appear to be significantly strained.
However, inspection of the angles around the pyridine
M-O(2)-C
than the corresponding angles in 2e (C(7)-C(6)-C(17),
111.4(3)°; C(33)-C(32)-C(43) 110.9(3)°). In 2e, the Ar
groups can rotate freely to minimize interchelate Ar-
py steric interactions, which allows tightening of the
N(1)-Ti-N(2) angle by 10° relative to that in 2b. For
both structures, the O(1)-Ti-N(3) and O(2)-Ti-N(4)
angles are very close to 90° and the N(3)-Ti-N(4)
angles are ca. 96°.
The Ti-O-C units in 2b and 2e are bent (Ti-O-C
ca. 130°), and the oxygens are, therefore, sp2-hybridized
and have only one p orbital available for O-Ti π-bond-
ing. The amide nitrogens are flat and also have one p
(6) Ranges for Ti-O and Ti-N σ bond distances were estimated
using covalent radii taken from the following: (a) Porterfield, W. M.
Inorganic Chemistry; Academic Press: San Diego, CA, 1993; p 214 (Ti,
1.32 Å; O, 0.73 Å, N, 0.75 Å). (b) J olly, W. L. Modern Inorganic
Chemistry; McGraw-Hill, Inc.: New York, 1984, p 52 (O, 0.66 Å; N,
0.70 Å).
(7) Dilworth, J . R.; Hanich, J .; Krestel, M.; Beck, J .; Strahle, J . J .
Organomet. Chem. 1986, 315, C9.
(8) Watenpaugh, K.; Caughlan, C. N. Inorg. Chem. 1966, 5, 1782.
(9) Toth, R. T.; Stephan, D. W. Can. J . Chem. 1991, 69, 172.
(10) Stoeckli-Evans, H. Helv. Chim. Acta. 1975, 58, 373.
(11) J ones, R. A.; Hefner, J . G.; Wright, T. C. Polyhedron 1984, 3,
1121.
(12) Sartain, W. J .; Selegue, J . P. Organometallics 1987, 6, 1812.
(13) Zambrano, C. H.; Profilet, R. D.; Hill, J . E.; Fanwick, P. E.;
Rothwell, I. P. Polyhedron 1993, 12, 689.

3318 Organometallics, Vol. 16, No. 15, 1997
Kim et al.
Ta ble 3. Ra cem iza tion Ba r r ier s for
(p yCAr 2O)2M(NMe2)2 Com p lexes
nitrogen reveals that the metal atom is displaced 5-8°
(toward the oxygen) off of the axis which would maxi-
mize py-Ti bonding. For example in 2b, the Ti-N(2)-
C(19) angle (128.2(7)°) is significantly larger than the
Ti-N(2)-C(23) angle (112.6(6)°).
∆Gq
(racemization)
(kcal/mol)
complex
{pyC(4-tBu-C6H4)2O}2Ti(NMe2)2 (2a )
{pyC(3-CF3-C6H4)2O}2Ti(NMe2)2 (2c)
{11-(2-pyridyl)dibenzosuberolato}2Ti(NMe2)2 (2f)
{pyC(3,5-(CF3)2-C6H3)2O}2Ti(NMe2)2 (2g)
{pyC(4-tBu-C6H4)2O}2Zr(NMe2)2 (3a )
{pyC(4-tBu-C6H4)2O}2Hf(NMe2)2 (6a )
{pyC(4-NEt2-C6H4)2O}2Hf(NMe2)2 (6e)
13.1(2)
12.6(3)
12.2(2)
12.5(2)
12.2(2)
13.2(2)
14.0(1)
The structure of zirconium complex 3a is very similar
to those of 2b and 2e. The minor differences in bond
angles result from the longer M-L bond lengths. The
structures of all three complexes are closely comparable
to those of other group 4 metal (N,O-chelate)2MX2
compounds containing bidentate N,O-chelate ligands
which form five-membered chelate rings, including
(Ox)2TiCl2,15 (Ox)2Ti{O-2,6-(iPr)2-C6H3}2, (MeOx)2Ti{O-
1
The H NMR spectrum of {pyC(3-CF3-C6H4)2O}2Ti-
(NMe2)2 (2c) at 0 °C contains a single set of sharp
pyridine resonances, a singlet for the NMe2 groups, and
broad resonances for the Ar hydrogens. As the tem-
perature is lowered, the pyridine and NMe2 resonances
remain essentially unchanged but the Ar region sharp-
ens to a complex pattern which is consistent with the
presence of two Ar environments. In particular, two
broad singlets (1/1 intensity ratio) for the H2 hydrogens
(see numbering scheme in eq 1) appear at -20 °C and
sharpen as the temperature is lowered further. These
observations are consistent with a static structure of
type A for 2c and rapid racemization at ambient
temperature. The racemization barrier was determined
from the line broadening of the H2 resonances (Table
3).19 Similar dynamic NMR behavior is observed for 2f,
2g, and 6e, indicating that these species adopt C2-
symmetric structures and undergo rapid inversion of
metal configuration at ambient temperature.20-22
On the basis of the X-ray structural and low-temper-
ature NMR results for representative compounds dis-
cussed above and the similarity of the ambient-
temperature NMR data for all of the compounds studied
(in particular the presence of sharp pyridine and NMe2
resonances and broad aromatic Ar resonances), we
conclude that group 4 metal (pyCAr2O)2M(NMe2)2 com-
plexes adopt type A structures in general but undergo
facile racemization which is rapid on the NMR time
scale at room temperature.
The free energy barriers for racemization of
(pyCAr2O)2M(NMe2)2 complexes (Table 3) are insensi-
tive to the ligand structure and the identity of the metal.
The ∆Gq (racemization) values for the titanium com-
plexes vary by less than 1 kcal/mol, despite the signifi-
cant variation in ligand electronic properties (e.g., 2a
vs 2g) and rigidity (2f vs 2a ,c,g). The ∆Gq (racemiza-
tion) values for analogous Ti, Zr, and Hf complexes 2a ,
3a , and 6a also vary by less than 1 kcal/mol. Previous
work by Bickley and Serpone shows that (Ox)2Ti{O-2,6-
(iPr)2-C6H3}2 and (MeOx)2Ti{O-2,6-(iPr)2-C6H3}2 un-
dergo inversion of metal configuration via five-coordi-
nate trigonal bipyramidal intermediates formed by
2,6-(iPr)2-C6H3}2,16
(MeOx)2Zr(CH2Ph)2,1a
and
(pyCMe2O)2Zr(CH2Ph)2.1b
Solu tion Str u ctu r es a n d Dyn a m ic P r op er ties of
(p yCAr 2O)2M(NMe2)2 Com p lexes. As summarized in
1
the experimental section, the ambient-temperature H
NMR spectra of (pyCAr2O)2M(NMe2)2 complexes each
contain a singlet for the NMe2 groups, a single set of
four multiplets for the four pyridine hydrogens, and
single set of resonances for the Ar group; in most cases,
the aromatic resonances for the Ar groups are broad.
The ambient-temperature 13C NMR spectra are analo-
gous and contain a single NMe2 resonance, a single set
of pyridine resonances, and a single set of Ar resonances
which are broadened in some cases. To probe the
fluxional behavior implied by the broadened Ar reso-
nances and to establish static structures, low-temper-
ature 1H NMR spectra of representative complexes were
investigated.
The {pyC(4-tBu-C6H4)2O}2M(NMe2)2 complexes 2a ,
3a , and 6a were investigated initially because it was
t
anticipated that the Bu resonance would serve as a
sensitive reporter of the Ar group environments. For
hafnium complex 6a , the sharp pyridine and NMe2
resonances do not change when the temperature is
lowered to -40 °C. However, the aromatic resonances
for the Ar groups, which comprise a doublet and a broad
singlet at ambient temperature, sharpen to three dou-
blets (2/1/1 intensity ratio) as the temperature is
t
lowered. Additionally, the sharp Bu resonance splits
to two singlets (1/1 intensity ratio). The variable-
temperature NMR behavior of 2a and 3a is analogous.17
These observations establish that the static structures
of 2a , 3a , and 6a contain two equivalent pyridine
groups, two equivalent NMe2 groups, and two inequiva-
lent sets of two Ar groups, i.e., the static structures are
of type A or B (Chart 2). On the basis of the solid state
structures of 2b, 2e, and 3a , we conclude that 2a , 3a ,
and 6a adopt structures of type A in CD2Cl2 solution.
However, these complexes undergo rapid inversion of
metal configuration which renders the four Ar groups
equivalent. Racemization barriers calculated from the
coalescence of the tBu resonances are listed in Table 3.18
(18) The barriers estimated from changes in the aromatic region
are similar but were less precisely determined due to overlapping
resonances which precluded accurate determination of coalescence
temperatures.
(19) For 2c: w1/2(excess) for the H2 resonances ) 20 Hz at 253K,
corresponding to kexchange ) 63 s-1 and ∆Gq ) 12.6(3) kcal/mol. The
coalescence point could not be determined due to interference from
the other Ar and py resonances.
(14) The ionic character of the M-O and M-Namide bonds in
(pyCAr2O)2M(NR2)2 species also contributes to the shortening of the
bond distances from the values predicted on the basis of covalent radii.
For a discussion and listing of key references regarding this point,
see: Howard, W. A.; Trnka, T. M.; Parkin, G. Inorg. Chem. 1995, 34,
5900.
(15) Studd, B. F.; Swallow, A. G. J . Chem. Soc. A 1968, 1961.
(16) Bird, P. H.; Fraser, A. R.; Lau, C. F. Inorg. Chem. 1973, 12,
1322.
(20) For 2f: Coalescence of δ 6.03 and 5.87 doublets, Tc ) 250 K,
∆ν ) 54 Hz; ∆Gq ) 12.2(2) kcal/mol.
(21) For 2g: Coalescence of the Ar H2 signals (δ 8.02, 7.42), Tc
)
t
(17) Coalescence of Bu resonances. For 2a : Tc ) 268 K, ∆ν ) 52
273 K, ∆ν ) 214 Hz, ∆Gq ) 12.5(2) kcal/mol; coalescence of Ar H4
signals (δ 7.94, 7.83), Tc ) 254 K, ∆ν ) 42 Hz, ∆Gq ) 12.5(2) kcal/mol.
(22) For 6e: Coalescence of δ 7.16 and 6.80 doublets, Tc ) 298 K,
∆ν ) 335 Hz; ∆Gq ) 14.0(1) kcal/mol.
Hz; ∆Gq ) 13.1(2) kcal/mol. For 3a : Tc ) 248 K, ∆ν ) 43 Hz; ∆Gq
)
12.2(2) kcal/mol. For 6a : Tc ) 268 K, ∆ν ) 43 Hz; ∆Gq ) 13.2(2) kcal/
mol.

Group 4 Metal (pyCAr2O)2M(NR2)2 Complexes
Organometallics, Vol. 16, No. 15, 1997 3319
Ta ble 4. Eth ylen e P olym er iza tion Resu ltsa
µmol of
time yield
activity
Mw
cocatalystsb
(h)
(g)
(kg/(mol‚atm‚h)) (×10-3
)
Mw/Mn
Tm
c
run
catalyst
catalyst
1
2
3
4
5
6
{pyC(4-tBu-Ph)2O}2Ti(NMe2)2 (2a )
{pyC(4-tBu-Ph)2O}2Zr(NMe2)2 (3a )
{pyC(4-NEt2-Ph)2O}2Ti(NMe2)2 (2e)
{pyC(4-NEt2-Ph)2O}2Zr(NMe2)2 (3e)
{pyC(4-Ph-Ph)2O}2Ti(NMe2)2 (2d )
{9-(2-pyridyl)-9-flu}2Ti(NMe2)2 (2b)
6.8
5.4
5.3
5.1
5.2
7.2
Al(iBu)3 + MAO
Al(iBu)3 + MAO
Al(iBu)3 + MAO
Al(iBu)3 + MAO
Al(iBu)3 + MAO
Al(iBu)3 + MAO
1
1
2
2
1
1
0.17
1.5
0.77
1.3
0.26
0.18
25
280
73
120
49
122
88
24.1
8.3
128.9
132.5
105
8.7
126.2
25
a
b
Conditions: toluene (120 mL), 1 atm of ethylene, T ) 43 °C. Al(iBu)3: 4.0 mmol. MAO: 7.0 mmol. Al/M ) ca. 2000. c DSC peak
mp.
pyridine dissociation.23 A similar “bond rupture” mech-
anism is likely for the (pyCAr2O)2M(NMe2)2 systems
studied here (eq 8). The lack of influence of ligand
(ligand) complex 5e is also highly fluxional, and low-
temperature NMR data (to -80 °C) do not allow
structural assignment in this case.24
Olefin P olym er iza tion Stu d ies. The ethylene po-
lymerization behavior of several (pyCAr2O)2M(NMe2)2
and (pyCAr2O)3M(NMe2) complexes has been investi-
gated using the in situ alkylation/activation protocol
developed earlier for chCp2Zr(NMe2)2 metallocene amide
compounds.3 The metal amide complex was treated
with excess Al(iBu)3 in toluene, activated with MAO,
and charged with ethylene (1 atm). The working
hypothesis of these experiments was that the AlR3
reagent and activator would generate (pyCAr2O)2M(R)+
or (pyCAr2O)2M(H)+ species in situ, by analogy to the
results observed in analogous experiments with
chCp2Zr(NMe2)2 complexes. The results are summarized
in Table 4. The in situ alkylation/activation procedure
activates (pyCAr2O)2Ti(NMe2)2 and (pyCAr2O)2Zr(NMe2)2
complexes for ethylene polymerization but not the
corresponding Hf compounds. The catalysts derived
from (pyCAr2O)2Zr(NMe2)2 species are more active than
the corresponding Ti catalysts (run 1 vs 2; run 3 vs 4)
under the conditions studied (toluene, 43 °C, 1 atm).
However, no clear ligand effects on activity are evident
from the limited data yet available.
The catalysts derived from (pyCAr2O)2M(NMe2)2 (M
) Ti, Zr) produce linear polyethylene (by 13C NMR) with
a very broad molecular weight distribution; in most
cases, the distributions are multimodal, characteristic
of multisite catalysts. Thus, the catalyst activation
chemistry is more complex than that observed for
chCp2Zr(NMe)2 catalysts. Earlier, we showed that
chCp2Zr(NMe)2 complexes are cleanly converted to
chCp2ZrR2 complexes upon reaction with AlR3 re-
agents.2,3 However, (Ox)2M(NMe2)2 and (pyCR2O)2MR2
complexes react with AlMe3 via Ox- or pyCR2O- trans-
fer yielding (Ox)AlMe2 or (pyCR2O)AlMe2 as the prin-
cipal products.1 It is likely the reaction of
(pyCAr2O)2M(NMe2)2 complexes with Al(iBu)3 or MAO
can result in transfer of either a Me2N- or a pyCAr2O-
ligand to Al, ultimately generating several metal alkyl
species which are active for ethylene polymerization.
This issue is under investigation.
structure or metal identity on the ∆Gq (racemization)
values presumably reflects the fact that (i) the electronic
differences between the pyCAr2O- ligands in these
compounds are located at the Ar groups and not the py
groups and (ii) steric interactions in these systems are
similar. The racemization barriers observed for
(pyCAr2O)2M(NMe2)2 compounds (12-14 kcal/mol) are
lower than those observed for (Ox)2Ti{O-2,6-(iPr)2-
C6H3}2 (20.0(3) kcal/mol), (MeOx)2Ti{O-2,6-(iPr)2-C6H3}2
(17.1(3) kcal/mol), (MeOx)2Zr(CH2CMe3)2 (15.1(1) kcal/
mol), (MeBr2Ox)2Zr(CH2CMe3)2 (15.7(1) kcal/mol), and
(MeBr2Ox)2Hf(CH2Ph)2 (17.5(1) kcal/mol).1a,23 This dif-
ference presumably results from the increased flexibility
of the pyCAr2O- ligands versus the quinolinolato ligands.
On the other hand, much lower barriers (ca. 8-10 kcal/
mol) were observed for (pyCR2O)2M(CH2Ph)2 complexes
(R ) CF3, Me, H; M ) Ti, Zr) which contain alkyl
substituents at the alkoxide carbon of the pyCR2O-
ligands.1b,c
1
The ambient-temperature H and 13C NMR spectra
of tris(ligand) (pyCAr2O)3M(NMe2) complexes 4c, 7b,
and 7c exhibit a single set of pyCAr2O- ligand reso-
nances. In each case, the pyridine ortho-hydrogen 1H
resonance appears as a broad singlet downfield from the
position observed for the corresponding resonance in
(pyCAr2O)2M(NMe2)2 complexes and in the range ob-
served for the free pyridine-alcohols. The 1H NMR
spectrum of 4c becomes more complex when the tem-
perature is lowered; however, a limiting spectrum was
not reached at -80 °C and a static structure could not
be established. Thus, these (pyCAr2O)3M(NMe2) species
are highly fluxional and may adopt structures with at
least one uncoordinated pyridine group. The tetrakis-
Further investigations of these catalysts and parallel
studies of (pyCAr2O)2M(R)+ cations are in progress.1c
Su m m a r y. Amine elimination reactions of pyCAr2-
OH pyridine-alcohols and group 4 metal M(NMe2)4
amides provide an efficient entry to (pyCAr2O)2M-
(NMe2)2 complexes. These species adopt C2-symmetric
structures in the solid state and in solution but undergo
facile inversion of configuration at the metal, with
(24) The structure of (Ox)4Zr has been determined by X-ray crystal-
lography, see: Lewis, D. F.; Fay, R. C. J . Chem. Soc., Chem. Commun.
1974, 1046.
(23) Bickley, D. G.; Serpone, N. Inorg. Chem. 1979, 8, 2200.

3320 Organometallics, Vol. 16, No. 15, 1997
Kim et al.
Bis(3-(tr iflu or om eth yl)ph en yl)-2-pyr idylm eth an ol (pyC-
(3-CF 3-C6H4)2OH, 1c). A solution of 3,3′-bis(trifluoromethyl)-
benzophenone (8.00 g, 25.1 mmol) in ether (80 mL) was added
dropwise to a solution of 2-lithiopyridine (from 30.0 mmol of
racemization barriers in the range of 12-14 kcal/mol.
The racemization barriers are insensitive to the Ar
group structure or the metal (Ti, Zr, Hf). These amide
complexes are activated for ethylene polymerization by
alkylation with AlR3 reagents and subsequent reaction
with MAO; however, the molecular weight distributions
of the polymer products are broad and show multimodal
character characteristic of multisite catalysts. The
reaction of the more acidic pyCAr2OH alcohols 1c or 1d
with Zr(NMe2)4 and the reactions of 1b, 1c or 1d with
Hf(NMe2)4 yield mixtures of (pyCAr2O)xM(NMe2)4-x
(x ) 1-3) species. The {pyCAr2O}3M(NMe2) tris(ligand)
species 4c and 7b,c can be obtained by suitable adjust-
ment of the reaction stoichiometry.
n
2-bromopyridine and BuLi) in ether (100 mL) at -78 °C. The
addition was made over 2 h, and the temperature was
maintained at -78 °C for an additional 3 h. The cold bath
was removed, and the dark green reaction mixture was stirred
overnight at ambient temperature, resulting in a viscous
brown solution. To this solution was added 50 mL of H2O
containing 5.00 g of [NH4]Cl. The solution was neutralized,
and the product was isolated and recrystallized as described
above for 1b. Yield 8.12 g, 68%; white crystals; mp 84-85
°C. 1H NMR (C6D6): δ 8.06 (d, J ) 4.8 Hz, 1H), 7.87 (s, 2H),
7.29 (d, J ) 7.9 Hz, 2H), 7.24 (d, J ) 7.8 Hz, 2H), 6.85 (t, J )
7.8 Hz, 2H), 6.80 (td, J ) 7.7, 1.7 Hz, 1H), 6.65 (d, J ) 6.9 Hz,
1H), 6.43 (m, 1H), 6.40 (s, 1H). 13C{1H} NMR (C6D6): 161.8,
148.2, 147.4, 136.7, 132.0, 130.8 (q, J CF ) 32 Hz), 129.0, 124.9
(q, J CF ) 4 Hz), 124.8 (q, J CF ) 273 Hz), 124.7 (q, J CF ) 4 Hz),
122.8, 122.4, 80.6. Anal. Calcd for C20H13F6NO: C, 60.46; H,
3.30; N, 3.53. Found: C, 60.62; H, 3.30; N, 3.65.
Exp er im en ta l Section
Gen er a l P r oced u r es. All experiments were performed on
a high-vacuum line or in a drybox under a purified N2
atmosphere. NMR spectra were recorded on a Bruker AC-
300 or AMX-360 spectrometer in sealed or Teflon-valved tubes
Bis(4-p h en ylp h en yl)-2-p yr id ylm eth a n ol (p yC(4-P h -
C6H4)2OH, 1d ). A slurry of 4,4′-diphenylbenzophenone (8.00
g, 23.9 mmol) in ether (120 mL) was added in portions to a
solution of 2-lithiopyridine (obtained from 26.3 mmol of
2-bromopyridine and nBuLi) in ether (80 mL) at -78 °C. The
addition was made over 2 h, and the temperature was
maintained at -78 °C for an additional 3 h. The cold bath
was removed, and the dark green reaction mixture was stirred
overnight at ambient temperature and then refluxed for 3 h.
The product was isolated and recrystallized as described above
for 1b. Yield 7.84 g, 72%; white crystals;, mp 170-172 °C. 1H
NMR (C6D6): δ 8.23 (d, J ) 4.7 Hz, 1H), 7.60 (d, J ) 8.4 Hz,
4H), 7.47 (m, 8H), 7.19 (t, J ) 8.0 Hz, 4H), 7.10 (t, J ) 7.2 Hz,
2H), 7.02 (d, J ) 7.9 Hz, 1H), 6.92 (td, J ) 7.6, 1.7 Hz, 1H),
6.62 (s, 1H), 6.52 (m, 1H). 13C{1H} NMR (CD2Cl2): 163.4,
148.2, 145.7, 141.0, 140.5, 137.0, 129.2, 129.0, 127.7, 127.3,
127.0, 123.2, 123.0, 80.9. Anal. Calcd for C30H23NO: C, 87.14;
H, 5.61; N, 3.39. Found: C, 87.14; H, 5.56; N, 3.59.
Bis(4-(d ieth yla m in o)p h en yl)-2-p yr id ylm eth a n ol (p yC-
(4-NEt2-C6H4)2OH, 1e). A solution of 4,4′-bis(diethylamino)-
benzophenone (8.00 g, 24.7 mmol) in ether (120 mL) was added
dropwise at -78 °C to a solution of 2-lithiopyridine (generated
from 27.1 mmol of 2-bromopyridine and nBuLi) in ether (80
mL). The addition was made over 2 h and the reaction
temperature was maintained at -78 °C for a further 3 h. The
cold bath was removed, and the dark green reaction mixture
was stirred overnight at ambient temperature. The product
was isolated and recrystallized as described above for 1b.
Yield 8.62 g, 79%; tan crystals; mp 106-107 °C. 1H NMR (CD2-
Cl2): δ 8.56 (d, J ) 4.9 Hz, 1H), 7.64 (td, J ) 7.8, 1.8 Hz, 1H),
7.19 (m, 2H), 7.09 (d, J ) 9.0 Hz, 4H), 6.61 (d, J ) 9.0 Hz,
4H), 5.88 (s, 1H), 3.35 (q, J ) 7.0 Hz, 8H), 1.16 (t, J ) 7.0 Hz,
12H). 13C{1H} NMR (CD2Cl2): 165.3, 147.8, 147.1, 136.5,
133.8, 129.4, 123.1, 122.2, 111.1, 80.5, 44.7, 12.7. Anal. Calcd
for C26H33N3O: C, 77.38; H, 8.24; N, 10.41. Found: C, 77.24;
H, 8.49; N, 10.40.
1-(2-p yr id yl)d iben zosu ber ol (1f). A solution of dibenzo-
suberone (9.98 mL, 55.4 mmol) in ether (80 mL) was added
dropwise over 90 min to a solution of 2-lithiopyridine (from
66.5 mmol of 2-bromopyridine and n-BuLi) in ether (100 mL)
at -78 °C. The temperature was maintained at -78 °C for a
further 3 h. The cold bath was removed, and the dark red
reaction mixture was stirred overnight at room temperature.
During this period, the color turned to greenish black. Water
(50 mL) was added, and the mixture was stirred for 1 h. The
ether and water phases were separated, and the water phase
was extracted with dichloromethane (4 × 50 mL). The extracts
were combined with the ether phase, dried over MgSO4, and
evaporated to give a pale yellow solid. Recrystallization from
methanol gave a white crystalline solid. Yield 11.0 g, 69%;
mp 198-199 °C. 1H NMR (CDCl3): δ 8.51 (dq, J ) 4.0, 0.9
1
at ambient probe temperature unless otherwise indicated. H
and 13C chemical shifts are reported versus SiMe4 and were
determined by reference to the residual solvent peaks. El-
emental analyses were performed by E & R Microanalytical
Laboratory, Inc., or Desert Analytics. Solvents were dried over
Na/benzophenone ketyl, except for chlorinated solvents, which
were distilled from activated molecular sieves (3 Å) or P2O5.
2-Bromopyridine was distilled from CaH2 prior to use. The
ketones 3,3′-bis(trifluoromethyl)benzophenone, 9-fluorenone,
4,4′-diphenylbenzophenone, 4,4′-bis(dimethylamino)benzo-
phenone, 3,3′,5,5′-tetrakis(trifluoromethyl)benzophenone, and
dibenzosuberone were obtained from Aldrich. The following
compounds were prepared by literature procedures: 4,4′-di-
tert-butylbenzophenone,25 bis(4-tert-butylphenyl)-2-pyridyl-
methanol (1a ), Ti(NMe2)4, Zr(NMe2)4, and Hf(NMe2)4.2,26
Compounds 2a , 3a , and 6a , which contain pyC(4-tBu-
C6H4)2O- ligands, were too soluble for conventional recrystal-
lization. However, these compounds were obtained as ana-
lytically pure crystalline solids by careful control of reaction
stoichiometry and subsequent slow evaporation of solvent from
CH2Cl2 solution. Compounds 4c and 5e were also found to be
extremely soluble and could not be recrystallized but were
obtained as analytically pure materials in a similar manner.
9-(2-P yr id yl)-9-flu or en ol (1b). A solution of 9-fluorenone
(10.2 g, 55.4 mmol) in ether (80 mL) was added dropwise to a
solution of 2-lithiopyridine (from 66.5 mmol of 2-bromopyridine
n
and BuLi) in ether (100 mL) at -78 °C (dry ice/acetone). The
addition was made over 90 min, and the temperature was
maintained at -78 °C for a further 3 h. The cold bath was
removed, and the dark green viscous reaction mixture was
stirred overnight at ambient temperature, hydrolyzed with
water, and neutralized. The ether layer was separated and
washed with water. The aqueous layer was extracted with
ether. The ether layer and ether extract were combined, dried
over MgSO4, and evaporated to dryness under vacuum. The
off-white solid was recrystallized from ether and then from
toluene to afford a white crystalline solid. Yield 12.9 g, 75%;
mp 130-131 °C. 1H NMR (CD2Cl2): δ 8.61 (d, J ) 3.9 Hz,
1H), 7.74 (d, J ) 7.6 Hz, 2H), 7.47 (td, J ) 8.8, 1.6 Hz, 1H),
7.41 (td, J ) 8.5, 1.9 Hz, 2H), 7.24 (m, 5H), 6.63 (d, J ) 8.0
Hz, 1H), 6.43 (s, 1H). 13C{1H} NMR (CD2Cl2): 161.2, 150.2,
147.7, 140.6, 137.5, 129.4, 128.5, 124.7, 123.1, 120.5, 120.4,
83.0. Anal. Calcd for C18H13NO: C, 83.38; H, 5.05; N, 5.40.
Found: C, 83.38; H, 5.20; N, 5.41.
(25) (a) Larner, B.; Peters, A. T. J . Chem. Soc. 1952, 880. (b) Buu-
Hoi, N. P.; Royer, R.; Xuong, N. D.; Thang, K. V. Bull. Soc. Chim. Fr.
1955, 1204.
(26) (a) Bradley, D. C.; Thomas, I. M. Proc. Chem. Soc. 1959, 225;
J . Chem. Soc. 1960, 3857. (b) Chisholm, M. H.; Hammond, C. E.;
Huffman, J . C. Polyhedron 1988, 7, 2515.

Group 4 Metal (pyCAr2O)2M(NR2)2 Complexes
Organometallics, Vol. 16, No. 15, 1997 3321
Hz, 1H), 7.99 (dd, J ) 7.8, 1.5 Hz, 2H), 7.55 (td, J ) 7.7, 1.8
Hz, 1H), 7.26 (td, J ) 7.4, 1.6 Hz, 2H), 7.20 (td, J ) 7.3, 1.5
Hz, 2H), 7.13 (ddd, J ) 8.5, 4.8, 1.0 Hz, 1H), 7.08 (dd, J ) 7.3,
1.3 Hz, 2H), 7.05 (dt, J ) 7.9, 0.9 Hz, 1H), 3.80 (br s, 1H, -OH),
2.96-2.76 (m, 4H). 13C{1H} NMR (CDCl3): 166.0, 149.4, 142.7,
137.8, 136.5, 130.2, 127.7, 126.2, 125.9, 122.2, 121.8, 80.0, 32.8.
volatiles were removed under vacuum. The deep red solid was
washed with pentane, dried overnight under vacuum, and
dissolved in dichloromethane. The solution was evaporated
to dryness under nitrogen purge yielding a red viscous oil
(quantitative yield). 1H NMR (CD2Cl2): δ 7.6-7.4 (br m, 20H),
7.14 (d, J ) 6 Hz, 2H), 6.56 (t, J ) 6 Hz, 2H), 3.20 (s, 12H). 1H
NMR (CD2Cl2, -80 °C): 7.98 (s, 2H), 7.6 (m, 6H), 7.49 (m, 4H),
7.39 (m, 4H), 7.10 (d, J ) 5.2 Hz, 2H), 6.94 (d, J ) 8.0 Hz,
2H), 6.76 (s, 2H), 6.42 (t, J ) 6.5 Hz, 2H), 3.21 (s, 12H).
13C{1H} NMR (CD2Cl2): 166.1, 151.0, 148.4, 137.1, 132.4 (br),
130.3 (q, J CF ) 32 Hz), 128.9, 125.1 (poorly resolved q, J ) 4
Hz), 124.7 (q, J CF ) 272 Hz), 124.3 (poorly resolved q, J ) 4
Hz), 123.7, 121.9, 93.2, 48.8. 19F NMR (CD2Cl2): δ -62.6.
Anal. Calcd for C44H36F12N4O2Ti: C, 56.91; H, 3.91; N, 6.03.
Found: C, 56.87; H, 3.85; N, 6.03.
{p yC(4-P h -C6H4)2O}2Ti(NMe2)2 (2d ). A solution of bis-
(4-phenylphenyl)-2-pyridylmethanol (1d , 0.517 g, 1.25 mmol)
in benzene (20 mL) was added dropwise at room temperature
to a solution of Ti(NMe2)4 (0.140 g, 0.625 mmol) in benzene
(20 mL). The mixture was stirred for 1 h, and the volatiles
were removed under vacuum. The deep red solid was recrys-
tallized from hot toluene, yielding red crystals (0.493 g, 82%).
1H NMR (C6D6): δ 7.82 (d, J ) 4.9 Hz, 2H), 7.7 (br m, 24H),
7.24 (t, J ) 7.4 Hz, 8H), 7.14 (t, J ) 7.5 Hz, 4H), 7.03 (d, J )
8.0 Hz, 2H), 6.63 (td, J ) 7.7, 1.5 Hz, 2H), 6.18 (t, J ) 6.6 Hz,
2H), 3.86 (s, 12H). 13C{1H} NMR (CD2Cl2): 167.5, 149.7 (br),
148.9, 141.2, 139.9, 136.4, 129.3, 129.2, 127.6, 127.3, 126.8,
123.9, 121.3, 93.8, 49.2. Anal. Calcd for C64H56N4O2Ti: C,
79.99; H, 5.87; N, 5.83. Found: C, 79.82; H, 5.86; N, 5.63.
{p yC(4-NEt2-C6H4)2O}2Ti(NMe2)2 (2e). A solution of bis-
(4-(diethylamino)phenyl)-2-pyridylmethanol (1e, 0.500 g, 1.24
mmol) in toluene (20 mL) was added dropwise to a solution of
Ti(NMe2)4 (0.139 g, 0.620 mmol) in toluene (15 mL) at room
temperature over 30 min. The deep red solution was stirred
for 1 h, and the volatiles were removed under vacuum. The
red solid was washed several times with pentane, dried
overnight under vacuum, and recrystallized from ether. Yield
0.553 g, 95%; red microcrystals. Recrystallization of the crude
product from toluene/pentane (1/1) yielded red rectangular
crystals of 2e‚toluene suitable for X-ray diffraction. 1H NMR
(CD2Cl2): δ 7.50 (d, J ) 4.6 Hz, 2H), 7.30 (td, J ) 7.9, 1.7 Hz,
2H), 7.18 (very br m, 8H), 7.01 (d, J ) 7.9 Hz, 2H), 6.56 (d, J
) 9.0 Hz, 8H), 6.40 (m, 2H), 3.37 (q, J ) 7.0 Hz, 16H), 3.31 (s,
12H), 1.17 (t, J ) 7.0 Hz, 24H). 13C{1H} NMR (CD2Cl2): 169.2,
148.8, 146.7, 137.8 (br), 135.4, 129.8 (br), 123.6, 120.4, 111.0,
93.5, 49.1, 44.7, 12.8. Anal. Calcd for C56H76N8O2Ti: C, 71.47;
H, 8.14; N, 11.91. Found: C, 71.58; H, 8.35; N, 11.40.
Anal. Calcd for
C20H17NO: C, 83.60; H, 5.96; N, 4.87.
Found: C, 83.59; H, 5.81; N, 4.81.
Bis(3,5-b is(t r iflu or om et h yl)p h en yl)-2-p yr id ylm et h a -
n ol (p yC(3,5-(CF 3)2-C6H3)2OH, 1g). A solution of 2-lithio-
pyridine (from 11.0 mmol of 2-bromopyridine and n-BuLi) in
ether (20 mL) was added dropwise over 30 min to a solution
of 3,3′,5,5′-tetrakis(trifluoromethyl)benzophenone (4.54 g, 10.0
mmol) in ether (30 mL) at -78 °C. The temperature was
maintained at -78 °C for a further 3 h. The cold bath was
removed, and the dark red reaction mixture was stirred
overnight at room temperature. Aqueous [NH4]Cl (4.6 M, 50
mL) was added. The mixture was extracted with dichlo-
romethane (4 × 25 mL). The extract was dried over MgSO4
and evaporated to give a brown viscous oil. Recrystallization
from hexanes gave a colorless crystalline solid. Yield 1.6 g,
30%; mp 74-75 °C. 1H NMR (CDCl3): δ 8.66 (dt, J ) 4.8, 1.0
Hz, 1H), 7.84 (s, 2H), 7.78 (td, J ) 7.7, 1.7 Hz, 1H), 7.72 (s,
4H), 7.38 (ddd, J ) 7.5, 5.7, 0.8 Hz, 1H), 7.06 (d, J ) 7.9 Hz,
1H), 6.62 (br s, 1H, OH). 13C{1H} NMR (CDCl3): 159.6, 148.7,
147.4, 137.7, 131.9 (q, J CF ) 34 Hz), 128.0 (q, J CF ) 4 Hz),
123.9, 122.7 (q, J CF ) 273 Hz), 122.3 (poorly resolved sept, J CF
) 4 Hz), 122.2, 79.9. 19F NMR (CDCl3): δ -63.2. Anal. Calcd
for C22H11F12NO: C, 49.55; H, 2.08; N, 2.63. Found: C, 49.61;
H, 1.87; N, 2.62.
{p yC(4-tBu -C6H4)2O}2Ti(NMe2)2 (2a ). A solution of bis-
(4-tert-butylphenyl)-2-pyridylmethanol (1a , 0.560 g, 1.50 mmol)
in toluene (20 mL) was added dropwise at room temperature
to a solution of Ti(NMe2)4 (0.168 g, 0.750 mmol) in toluene (20
mL). The deep red solution was stirred for 1 h, and the
volatiles were removed under vacuum. The deep red solid was
washed with pentane, dried under vacuum, and crystallized
by slow evaporation of a dichloromethane solution under
nitrogen purge. Yield 0.650 g, 98%; red rectangular crystals.
1H NMR (CD2Cl2): δ 7.39 (d, J ) 4.7 Hz, 2H), 7.33 (td, J )
7.9, 1.6 Hz, 2H), 7.25 (br m, 16H), 7.05 (d, J ) 7.9 Hz, 2H),
6.36 (m, 2H), 3.31 (s, 12H), 1.34 (s, 36H). 1H NMR (CD2Cl2,
-30 °C): 7.36 (m, 8H), 7.27 (m, 8H), 7.09 (d, J ) 8.3 Hz, 4H),
6.94 (d, J ) 7.7 Hz, 2H), 6.30 (t, J ) 6 Hz, 2H), 3.37 (s, 12H),
1.41 (s, 18H), 1.27 (s, 18H). 13C{1H} NMR (CD2Cl2): 168.0,
149.8, 148.8, 147.5 (v br), 135.9, 128.4, 124.8, 123.8, 120.9, 93.7,
49.1, 34.7, 31.6. Anal. Calcd for C56H72N4O2Ti: C, 76.34; H,
8.24; N, 6.36. Found: C, 76.24; H, 8.25; N, 6.40.
{11-(2-p yr id yl)d iben zosu ber ola to}2Ti(NMe2)2 (2f).
A
{9-(2-p yr id yl)-9-flu or en ola to}2Ti(NMe2)2 (2b). A solu-
tion of 9-(2-pyridyl)-9-fluorenol (1b, 0.500 g, 1.93 mmol) in
toluene (20 mL) was added dropwise to a solution of Ti(NMe2)4
(0.216 g, 0.964 mmol) in toluene (20 mL) at room temperature
over 30 min. The deep red solution was stirred for 1 h, and
the volatiles were removed under vacuum. The red solid was
washed several times with pentane, dried overnight in vacuo,
and recrystallized from toluene/pentane (10/1), yielding red
rectangular crystals (0.552 g, 88%). The crude product was
also recrystallized from dichloromethane/toluene (1/1), yielding
red rectangular crystals suitable for X-ray diffraction. 1H
NMR (CD2Cl2): δ 9.01 (d, J ) 5.0 Hz, 2H), 7.76 (d, J ) 7.5
Hz, 4H), 7.44 (t, J ) 7.8 Hz, 2H), 7.40 (t, J ) 7.0 Hz, 4H), 7.17
(m due to overlapping t and d, 6H), 7.04 (d, J ) 7.5 Hz, 4H),
6.46 (d, J ) 7.9 Hz, 2H), 3.24 (s, 12H). 13C{1H} NMR (CD2-
Cl2): 168.3, 152.8, 150.0, 140.4, 138.0, 128.9, 128.2, 126.1,
121.7, 120.7, 120.2, 96.4, 48.9. Anal. Calcd for C40H36N4O2-
Ti: C, 73.62; H, 5.56; N, 8.58. Found: C, 73.68; H, 5.76; N,
8.30.
solution of 11-(2-pyridyl)dibenzosuberol (0.575 g, 2.00 mmol)
in toluene (20 mL) was added dropwise to a solution of Ti-
(NMe2)4 (0.228 g, 1.00 mmol) in toluene (20 mL) at room
temperature. The resulting deep red solution was stirred for
1 h at room temperature. The volatiles were removed under
vacuum to give a red solid, which was washed with pentane
(40 mL). This product was recrystallized from dichloro-
methane, washed with pentane, and dried under vacuum (0.41
g, 55%). 1H NMR (CD2Cl2, 20 °C): δ 7.62 (d, J ) 4.7 Hz, 2H),
7.46 (td, J ) 7.9, 1.7 Hz, 2H), 7.25 (d, J ) 7.2 Hz, 4H), 7.13 (t,
J ) 7.5 Hz, 4H), 7.01 (d, J ) 8.1 Hz, 2H), 6.76 (m, 4H), 6.67
(m, 2H), 6.17 (d, J ) 8.0 Hz, 4H), 4.12 (m, 4H), 3.07 (m, 4H),
2.73 (s, 12H, NMe2). 1H NMR (CD2Cl2, -75 °C): δ 7.37 (m,
4H), 7.23-7.17 (m, 4H), 7.09 (d, J ) 7.4 Hz, 2H), 7.01 (t, J )
7.3 Hz, 2H), 6.81 (d, J ) 7.9 Hz, 2H), 6.74 (t, J ) 7.8 Hz, 2H),
6.64 (t, J ) 7.9 Hz, 2H), 6.54 (t, J ) 6.6 Hz, 2H), 6.04 (d, J )
8.1 Hz, 2H), 5.88 (d, J ) 7.9 Hz, 2H), 4.22-4.14 (m, 2H), 3.52-
3.45 (m, 2H), 3.10-2.99 (m, 4H), 2.80 (s, 12H, NMe2). 13C{1H}
NMR (CD2Cl2, 20 °C): 161.2, 148.6, 135.0, 131.1, 130.6, 127.2,
126.1, 125.2, 125.1, 121.5, 47.3 (NMe2), 35.7; the COTi
resonance was not detected. Anal. Calcd for C44H44N4O2Ti:
C, 74.62; H, 6.26; N, 7.91. Found: C, 74.41; H, 6.24; N, 7.73.
{p yC(3,5-(CF 3)2-C6H3)2O}2Ti(NMe2)2 (2g). A solution of
bis(3,5-bis((trifluoromethyl)phenyl)-2-pyridylmethanol (0.715
{p yC(3-CF 3-C6H4)2O}2Ti(NMe2)2 (2c). A solution of bis-
(3-(trifluoromethyl)phenyl)-2-pyridylmethanol (1c, 0.532 g,
1.34 mmol) in toluene (20 mL) was added dropwise at room
temperature to a solution of Ti(NMe2)4 (0.150 g, 0.669 mmol)
in toluene (15 mL). The solution was stirred for 1 h, and the

3322 Organometallics, Vol. 16, No. 15, 1997
Kim et al.
g, 1.34 mmol) in toluene (20 mL) was added dropwise to a
solution of Ti(NMe2)4 (0.228 g, 1.00 mmol) in toluene (20 mL)
at room temperature. The deep red solution was stirred for 1
h at room temperature. The volatiles were removed under
vacuum to give a red solid, which was washed with pentane
(40 mL). Recrystallization from toluene gave a dark red
crystals (plates), which were separated by decantation, washed
with pentane, and dried under vacuum (0.47 g, 59%). 1H NMR
(CD2Cl2, 20 °C): δ 7.89 (s, 4H), 7.80 (br s, 8H), 7.65-7.61 (m,
4H), 7.19 (d, J ) 7.9 Hz, 2H), 6.76 (t, J ) 6.3 Hz, 2H), 3.11 (s,
91.3, 44.3. 19F NMR (CD2Cl2): δ -62.6. Anal. Calcd for
C
62H42F18N4O3Zr: C, 56.24; H, 3.20; N, 4.23. Found: C, 56.45;
H, 3.30; N, 4.17.
{p yC(4-NEt2-C6H4)2O}4Zr (5e). A solution of 1e (0.240
g, 0.595 mmol) in benzene (15 mL) was added dropwise at room
temperature to a solution of Zr(NMe2)4 (0.040 g, 0.149 mmol)
in benzene (10 mL). The solution was stirred for 1 h. Removal
of the volatiles under vacuum yielded a tan oil in quantitative
yield. 1H NMR (C6D6): δ 8.15 (d, J ) 7.8 Hz, 4H), 8.07 (d, J
) 4.6 Hz, 4H), 7.59 (d, J ) 8.8 Hz, 16H), 7.10 (td, J ) 7.7, 1.7
Hz, 4H), 6.35 (t, J ) 5.7 Hz, 4H), 6.29 (d, J ) 8.9 Hz, 16H),
2.99 (q, J ) 7.0 Hz, 32H), 0.90 (t, J ) 6.9 Hz, 48H). 13C{1H}
NMR (C6D6): 170.6, 148.4, 146.1, 138.9, 135.3, 130.3, 123.9,
120.4, 111.3, 90.7, 44.4, 12.9. Anal. Calcd for C104H128N12O4-
Zr: C, 73.42; H, 7.58; N, 9.88. Found: C, 73.48; H, 7.49; N,
9.69.
{p yC(4-tBu -C6H4)2O}2Hf(NMe2)2 (6a ). This compound
was prepared according to the procedure for 2a and crystal-
lized by slow evaporation of dichloromethane/toluene (10/1)
under nitrogen purge. Yield 0.684 g, 92%; pale yellow micro-
crystals. 1H NMR (CD2Cl2): δ 7.41 (td, J ) 7.9 Hz, 0.9 Hz,
2H), 7.36 (d, J ) 5.4 Hz, 2H), 7.31 (d, J ) 8.2 Hz, 8H), 7.2 (br
s, 8H), 7.13 (d, J ) 8.0 Hz, 2H), 6.44 (m, 2H), 3.06 (s, 12H),
1.32 (s, 36H). 1H NMR (CD2Cl2, -20 °C): 7.39 (td, J ) 8, 1.4
Hz, 2H), 7.3 (m due to three overlapping d, 14H), 7.06 (d, J )
8 Hz, 2H), 7.00 (d, J ) 8 Hz, 4H), 6.39 (m, 2H), 3.06 (s, 12H),
1.38 (s, 18H), 1.26 (s, 18H). 13C{1H} NMR (CD2Cl2): 169.7,
150.0, 148.7, 147.5 (v br), 136.7, 128.2 (br), 125.0, 124.8, 121.4,
91.7, 44.7, 34.7, 31.6.
{p yC(4-NEt2-C6H4)2O}2Hf(NMe2)2 (6e). A solution of 1e
(0.500 g, 1.24 mmol) in benzene (20 mL) was added dropwise
at room temperature to a solution of Hf(NMe2)4 (0.220 g, 0.620
mmol) in benzene (20 mL). The yellow solution was stirred
for 1 h, and the volatiles were removed under vacuum. The
yellow solid was washed several times with pentane, dried
overnight under vacuum, and recrystallized from ether. Yield
0.382 g, 58%; yellow needles. 1H NMR (CD2Cl2): δ 7.45 (d, J
) 5 Hz, 2H), 7.37 (t, J ) 8 Hz, 2H), 7.1 (v br s, 8H), 7.10 (d, J
) 8 Hz, 2H), 6.54 (d, J ) 8 Hz, 8H), 6.47 (t, J ) 6 Hz, 2H),
3.33 (q, J ) 7.0 Hz, 16H), 3.03 (s, 12H), 1.10 (t, J ) 7.0 Hz,
24H). 1H NMR (CD2Cl2, -50 °C): δ 7.36 (t, J ) 8 Hz, 2H),
7.24 (d, J ) 6 Hz, 2H), 7.16 (d, J ) 9 Hz, 4H), 6.97 (d, J ) 8
Hz, 2H), 6.80 (d, J ) 9 Hz, 4H), 6.48 (d, J ) 9 Hz, 4H), 6.47
(d, J ) 9 Hz, 4H), 6.40 (t, J ) 6 Hz, 2H), 3.3 (m, 16H), 3.01 (s,
12H), 1.13 (t, J ) 7 Hz, 12H), 1.05 (t, J ) 7 Hz, 12H). 13C-
{1H} NMR (C6D6): 171.6, 149.0, 146.7, 139.0, 135.6, 130.0 (br),
124.8, 120.6, 111.7 (br), 92.0, 45.7, 44.5, 12.8. Anal. Calcd
for C56H76N8O2Hf: C, 62.76; H, 7.15; N, 10.46. Found: C,
66.85; H, 7.45; N, 9.59.
1
12H, NMe2), H NMR (CD2Cl2, -60 °C): δ 8.02 (s, 4H), 7.94
(s, 2H), 7.83 (s, 2H), 7.56 (t, J ) 7.9 Hz, 2H), 7.43 (s, 4H), 7.31
(d, J ) 5.0 Hz, 2H), 7.09 (d, J ) 8.0 Hz, 2H), 6.62 (t, J ) 6.3
Hz, 2H), 3.11 (s, 12H, NMe2). 13C{1H} NMR (CD2Cl2): 164.7,
151.8, 148.3, 138.3, 131.8 (q, J CF ) 34 Hz), 128.6 (q, J CF ) 4
Hz), 123.9, 123.8 (q, J CF ) 274 Hz), 122.9, 122.0 (poorly
resolved sept, J CF ) 4 Hz), 92.3, 48.4 (NMe2). 19F NMR (CD2-
Cl2): δ -63.1. Anal. Calcd for C48H32F24N4O2Ti: C, 48.02; H,
2.69; N, 4.67. Found: C, 47.89; H, 2.51; N, 4.43.
{p yC(4-tBu -C6H4)2O}2Zr (NMe2)2 (3a ). This compound
was prepared according to the procedure for 2a and crystal-
lized by slow evaporation of a dichloromethane/toluene (10/1)
solution under nitrogen purge. Yield 0.625 g, 92%, yellow
crystals. 1H NMR (CD2Cl2): δ 7.40 (td, J ) 7.8, 1.5 Hz, 2H),
7.35 (d, J ) 5.4 Hz, 2H), 7.31-7.17 (br m, 16H), 7.12 (d, J )
8.0 Hz, 2H), 6.45 (m, 2H), 3.02 (s, 12H), 1.35 (s, 36H). 1H NMR
(CD2Cl2, -40 °C): 7.44 (d, J ) 8.2 Hz, 2H), 7.36 (td, J ) 6.3
Hz, 1.5 Hz, 2H), 7.29 (br m, 12H), 7.13 (d, J ) 5.4 Hz, 2H),
7.00 (d, J ) 7.9 Hz, 4H), 6.36 (t, J ) 6.4 Hz, 2H), 3.00 (s, 12H),
1.37 (s, 18H), 1.24 (s, 18H). 13C{1H} NMR (CD2Cl2): 169.3,
149.9, 147.2, 136.6, 128.1, 125.0, 124.5, 121.3, 91.6, 44.7, 34.7,
31.6. Anal. Calcd for C56H72N4O2Zr: C, 74.04; H, 7.99; N, 6.17.
Found: C, 73.77; H, 7.96; N, 5.90.
{9-(2-p yr id yl)-9-flu or en ola to}2Zr (NMe2)2 (3b). A solu-
tion of 1b (0.500 g, 1.93 mmol) in toluene (20 mL) was added
dropwise to a solution of Zr(NMe2)4 (0.258 g, 0.965 mmol) in
toluene (20 mL) at room temperature over 30 min. The
reaction mixture was refluxed for 1 h. The volatiles were
removed under vacuum, and the yellow solid was washed with
pentane. Recrystallization from toluene/pentane (10/1) yielded
needles which collapsed to a yellow powder upon isolation.
Yield 0.446 g, 67%. 1H NMR (CD2Cl2): δ 8.90 (d, J ) 5.4 Hz,
2H), 7.76 (d, J ) 7.5 Hz, 4H), 7.50 (td, J ) 7.9, 1.7 Hz, 2H),
7.39 (td, J ) 7.5, 1.2 Hz, 4H), 7.22-7.15 (m, 6H), 7.08 (d, J )
7.5 Hz, 4H), 6.52 (d, J ) 8.0 Hz, 2H), 2.94 (s, 12H). 13C{1H}
NMR (CD2Cl2): 169.7, 152.6, 149.5, 140.3, 138.7, 129.0, 128.5,
125.3, 122.2, 121.7, 120.3, 44.5; alkoxide carbon not observed.
Anal. Calcd for C40H36N4O2Zr: C, 69.03; H, 5.21; N, 8.05.
Found: C, 68.89; H, 5.42; N, 7.79.
{p yC(4-NEt2-C6H4)2O}2Zr (NMe2)2 (3e). This compound
was prepared by the reaction of 1e (0.500 g, 1.24 mmol) and
Zr(NMe2)4 (0.166 g, 0.620 mmol) according to the procedure
for 2e, but with benzene as a solvent. The product was
recrystallized from ether. Yield 0.376 g, 62%; yellow needles.
1H NMR (C6D6): δ 7.91 (d, J ) 5.1 Hz, 2H), 7.6 (br s, 8H),
7.20 (d, J ) 8.0 Hz, 2H), 6.76 (td, J ) 7.6 Hz, 1.5 Hz, 2H),
6.54 (br, 8H), 6.35 (t, J ) 6.6 Hz, 2H), 3.70 (s, 12H), 2.99 (q, J
) 7.0 Hz, 16H), 0.89 (t, J ) 7.0 Hz, 24H). 13C{1H} NMR
(C6D6): 171.2, 148.9, 146.7, 138.7, 135.5, 130.0, 124.6, 120.5,
111.6, 91.8, 45.7, 44.5, 12.9. Anal. Calcd for C56H76N8O2Zr:
C, 68.32; H, 7.78; N, 11.38. Found: C, 68.41; H, 7.64: N, 11.14.
{p yC(3-CF 3-C6H4)2O}3Zr (NMe2) (4c). This compound
was prepared by the reaction of Zr(NMe2)4 (0.200 g, 0.748
mmol) and 1c (0.890 g, 2.24 mmol) according to the procedure
for 2c. The crude product was recrystallized from toluene/
pentane (10/1). Yield 0.644 g, 65%; pale yellow rectangular
crystals. 1H NMR (CD2Cl2): δ 8.25 (br, 3H), 7.53-7.48 (m,
9H), 7.40 (d, J ) 8.5 Hz, 6H), 7.28 (d, J ) 7.9 Hz, 6H), 7.24-
7.17 (m, 9H), 6.72 (t, J ) 5.9 Hz, 3H), 2.47 (s, 6H). 13C{1H}
NMR (CD2Cl2): 167.4, 150.9, 148.1, 137.3, 132.1, 129.9 (q, J CF
) 32 Hz), 128.3, 125.2 (poorly resolved q, J ) 4 Hz), 124.6 (q,
J CF ) 273 Hz), 124.0, 123.9 (poorly resolved q, J ) 4 Hz), 122.2,
{9-(2-p yr id yl)-9-flu or en ola to}3Hf(NMe2) (7b). A solution
of 1b (0.500 g, 1.93 mmol) in toluene (20 mL) was added to a
solution of Hf(NMe2)4 (0.228 g, 0.643 mmol) in toluene (20 mL)
at room temperature over 30 min. The reaction mixture was
refluxed for 2 h and evaporated to dryness under vacuum. The
yellow solid was washed with pentane and dried. Recrystal-
lization from hot toluene yielded pale yellow microcrystals.
Yield 0.406 g, 54%. 1H NMR (C6D6): δ 8.89 (br s, 3H), 7.55
(d, J ) 7.6 Hz, 6H), 7.29 (br d, J ) 6.6 Hz, 6H), 7.12 (t, J )
7.9 Hz, 6H), 6.84 (t, J ) 7.4 Hz, 6H), 6.59 (td, J ) 7.8, 1.5 Hz,
3H), 6.43 (d, J ) 7.9 Hz, 3H), 6.33 (t, J ) 6.4 Hz, 3H), 3.33 (s,
6H). 13C{1H} NMR (C6D6): 171.1, 154.8, 149.2, 140.5, 137.3,
128.4, 128.2, 126.3, 121.9, 121.7, 119.9, 94.7, 46.9. Anal. Calcd
for C56H42N4O3Hf: C, 67.43; H, 4.24; N, 5.62. Found: C, 66.98;
H, 4.12; N, 4.72.
{p yC(3-CF 3-C6H4)2O}3Hf(NMe2) (7c). A solution of 1c
(0.672 g, 1.69 mmol) in toluene (20 mL) was added dropwise
at room temperature to a solution of Hf(NMe2)4 (0.200 g, 0.564
mmol) in toluene (15 mL). The solution was stirred for 1 h,
and the volatiles were removed under vacuum. The yellow
solid was washed with pentane and dried overnight under
vacuum. The crude product was recrystallized from benzene.
Yield 0.652 g, 82%; pale yellow needles. 1H NMR (C6D6): δ

Group 4 Metal (pyCAr2O)2M(NR2)2 Complexes
Organometallics, Vol. 16, No. 15, 1997 3323
8.34 (br, 3H), 7.72 (s, 6H), 7.2 (m, 12H), 6.8 (m, 9H), 6.73 (td,
J ) 7.6, 1.5 Hz, 3H), 6.23 (t, J ) 6.0 Hz, 3 H), 2.85 (s, 6H).
13C{1H} NMR (C6D6): 167.6, 151.3, 148.0, 137.1, 132.1, 130.4
(q, J CF ) 32 Hz), 128.3, 125.1 (poorly resolved q, J ) 4 Hz),
124.9 (q, J CF ) 273 Hz), 124.0, 123.9 (poorly resolved q, J )
4.0 Hz), 121.9, 91.3, 44.6. 19F NMR (CD2Cl2): δ -62.6. Anal.
molecule showed a high degree of thermal motion; however,
again no model could be successfully refined. As a result, the
solvent molecule H atoms were not included in the final
refinement.
3a : Crystals of 3a containing 0.5 equiv of NMe2H were
obtained from the toluene reaction solution from the reaction
of 1a and Zr(NMe2)4. A suitable crystal was sectioned and
mounted in a capillary under N2. The systematic absences
were uniquely consistent with the space group P21/n. The
NMe2H molecule was located in the asymmetric unit with 50%
refined partial occupancy. The N, O, and Zr atoms were
refined anisotropically, the C atoms were refined isotropically,
and the H atoms were placed in idealized positions.
Calcd for
C62H42F18N4O3Hf: C, 52.76; H, 3.00; N, 3.97.
Found: C, 52.86; H, 3.01; N, 3.80.
X-r a y Cr ysta llogr a p h y. The X-ray analyses of 2b and 2e
were performed by R. D.Rogers. The X-ray analysis of 3a was
performed by A. L. Rheingold and G. P. A. Yap. Details are
provided in Table 1 and the Supporting Information.
2b: An orange single crystal of 2b was mounted in a glass
capillary flushed with Ar and transferred to the goniometer.
The space group was determined to be either the centric Pnma
or the acentric Pna21 from the systematic absences; the
subsequent solution and refinement of the structure was
carried out in the latter. The geometrically constrained H
atoms were placed in calculated positions and allowed to ride
on the bonded atom with B ) 1.2 × Uequiv(C). Refinement of
non-H atoms was carried out with anisotropic temperature
factors. The available crystals for 2b were very small, and
eventually the data for this compound were collected on a 0.1
× 0.1 × 0.4 mm crystal. The scattering at room temperature
was very weak, and the final refinement exhibited high
thermal motion. The refinement of this compound was based
on all data (observed as well as unobserved), and as a result,
the final R values are high. Despite the high R values, the
refinement proceeded without difficulty. The geometrical
details are affected by higher than normal esd’s, but the overall
structure and atom connectivity are clear.
2e: An orange single crystal of 2e‚toluene was mounted in
a glass capillary flushed with Ar and transferred to the
goniometer. The space group was determined to be P21/n from
the systematic absences. The geometrically constrained H
atoms were placed in calculated positions and allowed to ride
on the bonded atom with B ) 1.2 × Uequiv(C). The methyl
hydrogens were included as a rigid group with rotational
freedom at the bonded carbon (B ) 1.2 × Uequiv(C)). Refine-
ment of non-H atoms was carried out with anisotropic tem-
perature factors. A high degree of thermal motion was noted
in a number of atoms, especially the ethyl and methyl groups.
While disorder is most likely present in all or some of these
atoms, no suitable disorder model could be successfully
developed and refined. In addition, the toluene solvent
Eth ylen e P olym er iza tion . Polymerization experiments
were performed in a 250 mL Fischer-Porter bottle equipped
with a mechanical stirrer and temperature probe. Data are
summarized in Table 4. The Fischer-Porter bottle was
charged with toluene (120 mL), Al(iBu)3 (1 mL, 4.0 mmol), and
the metal amide complex. MAO (Albemarle; 9.9% solution in
toluene; 4.49 wt % total Al; 7.0 mmol Al) was added. The
reaction mixture was heated to 43 °C, and the bottle was
charged with ethylene (1 atm). The ethylene pressure was
maintained at 1 atm during the polymerization. The polym-
erization was quenched after 1 h by injection of EtOH/1 M
HCl. The polymer was collected by filtration, washed several
times with EtOH, dried (70 °C, vacuum oven, overnight), and
weighed. 13C NMR, gel permeation chromatography (GPC),
and differential scanning calorimetry (DSC) analyses of the
polymer samples were carried out at the Yokkaich Research
Center, Mitsubishi Petrochemical Co., J apan. For DSC analy-
ses, samples were heated from 30 to 200 °C at 50 °C/min and
cooled to 0 °C at 10 °C/min and the second trace (0 to 200 °C
at 10 °C/min) was recorded.
Ack n ow led gm en t. This work was supported by the
Department of Energy (Grant No. DE-FG02-88ER13935)
and the Mitsubishi Chemical Corporation.
Su p p or tin g In for m a tion Ava ila ble: Tables of crystal
data and structural refinement, atomic coordinates, bond
lengths and angles, anisotropic displacement parameters, and
hydrogen coordinates for 2b, 2e, and 3a (32 pages). Ordering
information is given on any current masthead page.
OM970236K