Fluorinated diarylamido complexes of lithium, zirconium, and hafnium

Article abstract of DOI:10.1021/ic702293d

Deprotonation of N-(2-fluorophenyl)-2,6-diisopropylaniline (H[ ⁱPrAr-NF]) with 1 equiv of n-BuLi in toluene at -35°C produced cleanly [ⁱPrAr-NF]Li. Subsequent recrystallization of [ ⁱPrAr-NF]Li in diethyl ether generated the bis(ether) adduct [ ⁱPrAr-NF]Li(OEt₂)₂. An X-ray study of [ ⁱPrAr-NF]Li(OEt₂)₂ showed it to be a four-coordinate species with the coordination of the fluorine atom to the lithium center. The reactions of [ⁱPrAr-NF]Li with MCl ₄(THF)₂ (M = Zr, Hf), regardless of the stoichiometry employed, afforded the corresponding dichloride complexes [ⁱPrAr-NF] ₂MCl₂ (M = Zr, Hf). Alkylation of [ⁱPrAr-NF] ₂MCl₂ with a variety of Grignard reagents generated [ ⁱPrAr-NF]₂MR₂ (M = Zr, Hf; R = Me, i-Bu, CH₂Ph). The X-ray structures of [ⁱPrAr-NF] ₂ZrCl₂, [ⁱPrAr-NF]₂HfCl₂, [ⁱPrAr-NF]₂ZrMe₂, [ⁱPrAr-NF] ₂Zr(i-Bu)₂, and [ⁱPrAr-NF] ₂Hf(CH₂Ph)₂ are all indicative of the coordination of the fluorine atoms to these group 4 metals, leading to a C ₂-symmetric, distorted octahedral geometry for these molecules.

Full text of DOI:10.1021/ic702293d

Inorg. Chem. 2008, 47, 3298-3306
Fluorinated Diarylamido Complexes of Lithium, Zirconium, and Hafnium
Wei-Ying Lee and Lan-Chang Liang*
Department of Chemistry and Center for Nanoscience & Nanotechnology, National Sun Yat-sen
UniVersity, Kaohsiung 80424, Taiwan
Received November 21, 2007
Deprotonation of N-(2-fluorophenyl)-2,6-diisopropylaniline (H[iPrAr-NF]) with 1 equiv of n-BuLi in toluene at –35 °C
produced cleanly [iPrAr-NF]Li. Subsequent recrystallization of [iPrAr-NF]Li in diethyl ether generated the bis(ether)
adduct [iPrAr-NF]Li(OEt2)2. An X-ray study of [iPrAr-NF]Li(OEt2)2 showed it to be a four-coordinate species with the
coordination of the fluorine atom to the lithium center. The reactions of [iPrAr-NF]Li with MCl4(THF)2 (M ) Zr, Hf),
regardless of the stoichiometry employed, afforded the corresponding dichloride complexes [iPrAr-NF]2MCl2 (M )
Zr, Hf). Alkylation of [iPrAr-NF]2MCl2 with a variety of Grignard reagents generated [iPrAr-NF]2MR2 (M ) Zr, Hf; R
) Me, i-Bu, CH2Ph). The X-ray structures of [iPrAr-NF]2ZrCl2, [iPrAr-NF]2HfCl2, [iPrAr-NF]2ZrMe2, [iPrAr-NF]2Zr(i-
Bu)2, and [iPrAr-NF]2Hf(CH2Ph)2 are all indicative of the coordination of the fluorine atoms to these group 4 metals,
leading to a C2-symmetric, distorted octahedral geometry for these molecules.
Introduction
mido phosphine complexes, we became interested in their
fluorine analogues due primarily to the potentials of the
weakly coordinating nature of the fluorine atom that may
play an important role in stabilizing and activating the
reactive species upon fluorine association and dissociation,
respectively.12,13,54,55 To this end, we have set out to prepare
metal complexes of ortho-fluorinated diarylamides and
examine their coordination chemistry. In this contribution,
we describe the preparation and structural characterization
of lithium, zirconium, and hafnium complexes derived from
N-(2-fluorophenyl)-2,6-diisopropylanilide ([iPrAr-NF]-). The
coordination characteristics of the ortho-fluorine atom with
respect to these electrophilic metals are discussed.
Amido complexes of group 4 metals continue to constitute
an active area of exploratory research.1–22 Much recent
attention has been paid to the development of well-defined
catalysts for homogeneous olefin polymerization.23–28 It has
been shown that variations of bi- and tridentate amido ligands
such as [RN(CH2)3NR]2- (R ) 2,6-iPr2C6H3, 2,6-Me2C6H3)29
and [(tBuN-o-C6H4)2O]2-,30 respectively, are capable of
stabilizing the catalytically active species of group 4 metals
for polymerization of R-olefins in a living manner. Modifica-
tions of chelating amido ligands in this regard are of current
interest.31–38
We are currently exploring coordination chemistry of
chelating amido ligands involving both early and late
transition metals.39–49 A number of metal complexes that
contain o-phenylene-derived amido phosphine ligands have
shown markedly thermal stability while generating intriguing
reactivity.50–53 During our investigation involving diaryla-
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* E-mail: lcliang@mail.nsysu.edu.tw.
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3298 Inorganic Chemistry, Vol. 47, No. 8, 2008
10.1021/ic702293d CCC: $40.75  2008 American Chemical Society
Published on Web 02/23/2008

Fluorinated Diarylamido Complexes of Li, Zr, and Hf
Scheme 1
Results and Discussion
in pentane but fairly soluble in arenes such as benzene and
1
toluene. The H and 13C NMR spectra of [iPrAr-NF]Li in
Addition of 1 equiv of n-BuLi to a toluene solution of
H[iPrAr-NF]45 at –35 °C produced cleanly [iPrAr-NF]Li as
an off-white solid. The lithium complex is sparingly soluble
C6D6 indicate Cs symmetry for this molecule. The room-
7
temperature 19F{1H} and Li{1H} NMR spectra reveal a
singlet resonance at –148.5 and 1.6 ppm, respectively, for
7
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significantly upon cooling to temperatures lower than -70
°C (in toluene-d8), but no 19F-7Li coupling is observed.
Similar phenomenon was also found in a variable-temper-
ature 19F{1H} NMR study. These results are consistent with
a fluxional exchange process that involves rapid association
and dissociation of the fluorine donor with respect to the
lithium atom. Given the high electrophilic nature of the hard
lithium cation, [iPrAr-NF]Li is likely an oligomeric aggregate
(Scheme 1). In accord with this postulation, [iPrAr-NF]Li
adopts readily 2 equiv of diethyl ether upon recrystallization
from a diethyl ether solution to give colorless crystals of
[iPrAr-NF]Li(OEt2)2. Similar to [iPrAr-NF]Li, [iPrAr-NF]Li(O-
Et2)2 displays solution Cs symmetry on the NMR time scale
as evidenced by the 1H and 13C NMR spectra, and no 19F-7Li
coupling is observed even at -80 °C (in toluene-d8).
The solid-state structure of [iPrAr-NF]Li(OEt2)2 was
confirmed by X-ray diffraction analysis. Crystallographic
data are summarized in Table 1. As depicted in Figure 1,
[iPrAr-NF]Li(OEt2)2 is a four-coordinate species with the
lithium center being coordinated with a bidentate [iPrAr-
NF]- and two diethyl ether molecules. The coordination
geometry of [iPrAr-NF]Li(OEt2)2 is best described as a
distorted tetrahedron with the dihedral angles of N-Li-F
and O-Li-O being 64.0°. The bond angles about the lithium
center range from 80.6(2) to 131.0(2)°, with the most acute
being associated with the [iPrAr-NF]- ligand. The lithium
atom lies perfectly on the N-phenylene-F plane, a result
that is in sharp contrast to that of its phosphine analogue
[Me-NP]Li(THF)2 ([Me-NP]- )N-(2-diphenylphosphinophe-
nyl)-2,6-dimethylanilide) in which the lithium atom is
displaced significantly from the N-phenylene-P plane by
0.5954 Å.42 Such discrepancy likely highlights the increased
hardness and the small size of the fluorine atom in [iPrAr-
NF]- as compared to the diphenyl-substituted phosphorus
donor in [Me-NP]-, although the former carries a larger aryl
substituent at the amido nitrogen. The N-aryl ring is
perpendicular to the N-phenylene-F plane. The F-Li
distance of 2.150(4) Å in [iPrAr-NF]Li(OEt2)2 is comparable
to those found in Li4(LH)2(THF)6 (L ) 2,4,6-tris(2-fluoroa-
nilido)-1,3,5-triazene) (2.15(2) Å)56 and [HC{SiMe2N(2-
FC6H4)}3Sn(Li)] (1.984 Å average).57 The fluorine donor,
however, is likely to dissociate readily from the lithium center
in solution as suggested by the NMR spectroscopic studies.
This phenomenon is consistent with the weakly coordinating
(56) Rivals, F.; Steiner, A. Chem. Commun. 2001, 2104–2105.
(57) Lutz, M.; Haukka, M.; Pakkanen, T. A.; McPartlin, M.; Gade, L. H.
Inorg. Chim. Acta 2003, 345, 185–189.
Inorganic Chemistry, Vol. 47, No. 8, 2008 3299

Lee et al.
Table 1. Crystallographic Data for [iPrAr-NF]Li(OEt2)2, [iPrAr-NF]2ZrCl2, [iPrAr-NF]2HfCl2, [iPrAr-NF]2ZrMe2, [iPrAr-NF]2Zr(i-Bu)2, and
[iPrAr-NF]2Hf(CH2Ph)2
compound
[iPrAr-NF]Li(OEt2)2
C26H41FLiNO2
{[iPrAr-NF]2ZrCl2}(OEt2)
formula
Fw
C40H52Cl2F2N2OZr
776.96
425.54
crystal size (mm3)
Dcalc (Mg/m3)
crystal syst
space group
a (Å)
0.55 × 0.4 × 0.25 mm3
0.66 × 0.38 × 0.28
1.067
1.283
monoclinic
P21/c
16.3699(5)
9.5320(3)
17.0844(6)
90
96.353(2)
90
triclinic
j
P1
12.4422(2)
13.03410(10)
14.8695(2)
64.6730(10)
86.7590(10)
68.3530(10)
2011.15(4)
2
b (Å)
c (Å)
R (deg)
ꢀ (deg)
γ (deg)
V (Å3)
2649.44(15)
4
Z
T (K)
200(2)
0.71073
50.72
-16,19;-9,11;-20,20
14501
4820
0.0712
200(2)
0.71073
55.02
-16,16;-16,16;-18,19
30725
9209
0.0529
radiation, λ (Å)
2θmax (deg)
index ranges (h;k;l)
total no. of reflns
no. of indep reflns
Rint
absorp coeff (mm-1
)
0.070
0.447
no. of data/restraints/parameters
goodness of fit
4820/0/281
1.042
R1 ) 0.0654, wR2 ) 0.1586
R1 ) 0.1216, wR2 ) 0.1955
-0.342 to 0.297
9209/0/424
1.142
R1 ) 0.0429, wR2 ) 0.1110
R1 ) 0.0551, wR2 ) 0.1258
-0.665 to 0.720
final R indices (I > 2σ(I))
R indices (all data)
residual density (e/Å3)
compound
[iPrAr-NF]2HfCl2
[iPrAr-NF]2ZrMe2
formula
Fw
C36H42Cl2F2HfN2
790.11
C38H48F2N2Zr
662.00
crystal size (mm3)
Dcalc (Mg/m3)
crystal syst
space group
a (Å)
0.45 × 0.4 × 0.2
0.45 × 0.4 × 0.22
1.509
1.260
triclinic
triclinic
j
j
P1
P1
9.18380(10)
13.6568(2)
16.0542(3)
67.0810(10)
77.9100(10)
70.2950(10)
1738.88(5)
2
12.7396(2)
16.7097(3)
17.8080(4)
105.5730(10)
105.8670(10)
91.7950(10)
3490.07(11)
4
b (Å)
c (Å)
R (deg)
ꢀ (deg)
γ (deg)
V (Å3)
Z
T (K)
200(2)
0.71073
52.04
-11,11;-16,16;-19,19
24897
6845
0.0529
200(2)
Mo KR, 0.71073
50.76
-15,15;-20,20;-21,21
35399
12304
0.0690
0.353
radiation, λ (Å)
2θmax (deg)
index ranges (h;k;l)
total no. of reflns
no. of indep reflns
Rint
absorp coeff (mm-1
)
3.190
no. of data/restraints/parameters
goodness of fit
6845/0/389
0.924
R1 ) 0.0328, wR2 ) 0.0833
R1 ) 0.0391, wR2 ) 0.0993
-1.990 to 1.577
12304/0/775
0.826
R1 ) 0.0600, wR2 ) 0.1593
R1 ) 0.0895, wR2 ) 0.1910
-0.797 to 1.910
final R indices (I > 2σ(I))
R indices (all data)
residual density (e/Å3)
compound
[iPrAr-NF]2Zr(i-Bu)2
[iPrAr-NF]2Hf(CH2Ph)2
formula
Fw
C44H60F2N2Zr
746.16
C50H56F2HfN2
901.46
crystal size (mm3)
Dcalc (Mg/m3)
crystal syst
space group
a (Å)
0.24 × 0.2 × 0.08
0.24 × 0.2 × 0.08
1.198
1.407
monoclinic
P21/n
18.4614(4)
12.6894(3)
19.2483(5)
90
113.4910(10)
90
4135.47(17)
4
triclinic
j
P1
11.06020(10)
11.73110(10)
18.4898(3)
74.8510(10)
86.3970(10)
66.8840(10)
2127.60(4)
2
b (Å)
c (Å)
R (deg)
ꢀ (deg)
γ (deg)
V (Å3)
Z
T (K)
radiation, λ (Å)
200(2)
0.71073
200(2)
0.71073
3300 Inorganic Chemistry, Vol. 47, No. 8, 2008

Fluorinated Diarylamido Complexes of Li, Zr, and Hf
Table 1. Continued
compound
[iPrAr-NF]2Zr(i-Bu)2
50.72
-22,22;-15,15;-23,21
31134
7545
0.0922
0.305
[iPrAr-NF]2Hf(CH2Ph)2
50.76
-13,13;-14,14;-22,22
29927
7798
0.0593
2.496
2θmax (deg)
index ranges (h;k;l)
total no. of reflns
no. of indep reflns
Rint
absorp coeff (mm-1
)
no. of data/restraints/parameters
goodness of fit
7545/0/443
1.124
7798/0/497
1.111
final R indices (I > 2σ(I))
R1 ) 0.0691, wR2 ) 0.1595
R1 ) 0.1134, wR2 ) 0.1977
-1.046 to 0.869
R1 ) 0.0317, wR2 ) 0.0844
R1 ) 0.0416, wR2 ) 0.1115
-1.702 to 0.762
R indices (all data)
residual density (e/Å3)
nature of the fluorine atom but somewhat surprising in view
of the hardness of both donor and acceptor. The Li-N and
Li-O distances are both well within the expected values.
The reactions of [iPrAr-NF]Li with MCl4(THF)2 (M ) Zr,
Hf),58 irrespective of the molar ratio, in toluene or diethyl
ether at –35 °C afforded the corresponding dichloride
complexes [iPrAr-NF]2ZrCl2 and [iPrAr-NF]2HfCl2 in high
isolated yield. Attempts to spectroscopically observe or
isolate the transient 1:1 products from reactions employing
1 equiv of [iPrAr-NF]Li were not successful. Instead, [iPrAr-
NF]2ZrCl2 and [iPrAr-NF]2HfCl2 were generated exclusively.
These results are notably different from what has been
reported for the phosphine analogue N-(2-diphenylphosphi-
nophenyl)-2,6-diisopropylanilide ([iPr-NP]-), which reacts
with 1 equiv of MCl4(THF)2 (M ) Zr, Hf) to produce
successfully the corresponding [iPr-NP]MCl3(THF)49 under
similar conditions. The unsuccessful observation or isolation
of the presumed [iPrAr-NF]MCl3(THF) is ascribable to the
steric unsaturation of this transient molecule due to the lack
of substituent at the fluorine donor.
ppm), and [iPrAr-NF]Li(OEt2)2 (-149.0 ppm). The 1H NMR
spectra of [iPrAr-NF]2ZrCl2 and [iPrAr-NF]2HfCl2 at room
temperature reveal one septet resonance for isopropylmethine
and two doublet resonances for isopropylmethyl groups.
These results are indicative of an intramolecular symmetry
for the two [iPrAr-NF]- ligands in [iPrAr-NF]2ZrCl2 and
[iPrAr-NF]2HfCl2 on the NMR time scale. In principle, four
possible stereoisomers (and their corresponding enantiomers)
can be deduced for the solution structures of these dichloride
complexes on the basis of the NMR investigation, assuming
that both molecules contain coordinated fluorine atoms in
1
an octahedral core (Figure 2). A variable-temperature H
NMR study of [iPrAr-NF]2ZrCl2 (in toluene-d8) showed that
the isopropyl methine and methyl signals become broadening
at -20 °C and resolve to give two sets of signals at a
temperature lower than -50 °C, consistent with a rapid
rotation of the 2,6-diisopropylphenyl groups about the N-Ar
bonds at room temperature.59 As a result, the two arylated
amido nitrogen donors in [iPrAr-NF]2MCl2 (M ) Zr, Hf)
are likely trans to each other, given the significant steric bulk
imposed by the diisopropylphenyl groups. Stereoisomers II
and III are thus more possible than I and IV. In view of the
trans influence order of the formally anionic chlorides and
the neutral fluorine atoms, stereoisomer III seems more likely
than II.
The fluorine atoms in [iPrAr-NF]2ZrCl2 and [iPrAr-
NF]2HfCl2 appear as a singlet resonance in the 19F{1H} NMR
spectra at -115.6 and -118.5 ppm, respectively. These 19
F
chemical shifts are relatively downfield as compared to those
of H[iPrAr-NF] (-138.3 ppm),45 [iPrAr-NF]Li (-148.5
Colorless crystals of [iPrAr-NF]2ZrCl2 and [iPrAr-
NF]2HfCl2 suitable for X-ray diffraction analysis were grown
from a concentrated diethyl ether solution at –35 °C. As
depicted in Figures 3 and 4, both structures are C2-symmetric
and correspond to the stereoisomer III in which the two
amido nitrogen donors are virtually trans to each other
(N-M-N angles of 145.44(7)° for Zr and 144.9(1)° for Hf)
and the two fluorine donors (and the two chloride ligands)
are cis, consistent with what is deduced from the solution
NMR studies. The severe distortion from the ideal octahedron
is ascribed to the acute bite angles of 70.16° (average) for
[iPrAr-NF]2ZrCl2 and 71.14° (average) for [iPrAr-NF]2HfCl2,
leading to markedly wide Cl-M-Cl angles of 105.34(3)°
for the former and 104.63(5)° for the latter. The C2 axis lies
Figure 1. Molecular structure of [iPrAr-NF]Li(OEt2)2 with thermal
ellipsoids drawn at the 35% probability level. Selected bond distances (Å)
and angles (deg): F(1)-Li(1) 2.150(4), O(1)-Li(1) 2.000(4), O(2)-Li(1)
1.962(4), N(1)-Li(1) 1.959(4), N(1)-Li(1)-O(2) 115.3(2), N(1)-Li(1)-O(1)
131.0(2), O(2)-Li(1)-O(1) 108.1(2), N(1)-Li(1)-F(1) 80.6(2), O(2)-Li(1)-
F(1) 128.7(2), O(1)-Li(1)-F(1) 89.8(2).
Figure 2. Possible stereoisomers for [iPrAr-NF]2MCl2, where NxFx (x )
1, 2) represents the chelating o-fluorinated diarylamido ligands.
Inorganic Chemistry, Vol. 47, No. 8, 2008 3301

Lee et al.
one set of signals for the reaction aliquots. The stereoisomeric
preference of [iPrAr-NF]2ZrCl2 and [iPrAr-NF]2HfCl2 is
notably different from that of their phosphorus analogues
such as [Me-NP]2ZrCl2,49 [Me-NP]2HfCl2,49 and ZrCl2[η2-
N(SiMe2CH2PMe2)2]2,60 whose solid-state structures cor-
respond instead to that analogous to stereoisomer I (with
phosphorus donors in the place of the fluorine atoms). The
Zr-N and Hf-N distances in [iPrAr-NF]2MCl2 are compa-
rable to the expected values for a six-coordinate Zr(IV) and
Hf(IV) species; however, the Zr-Cl and Hf-Cl distances
of 2.3570 (average) and 2.3349 Å (average), respectively,
are relatively shorter than those of [Me-NP]2ZrCl2 (2.4502
Å average),49 [Me-NP]2HfCl2 (2.4170 Å average),49 ZrCl2(η2-
N(SiMe2CH2PMe2)2]2 (2.4599 Å average),60 and MLCl2(µ-
Cl)2Li(OEt2)2 (L ) 5-tert-butyl-2-[(2,6-diisopropylpheny-
l)aldimino]pyrrolide; M ) Zr, 2.4505 Å average; M ) Hf,
2.4397 Å average).48 The M-F distances in [iPrAr-NF]2ZrCl2
(2.3635 Å average) and [iPrAr-NF]2HfCl2 (2.312 Å average)
are notably shorter than the corresponding values found for
[C6F5NCH2CH2CH2NC6F5]Zr(CH2Ph)2(2.511(1)Å),61HC{SiMe2N(2-
FC6H4)}3ZrCl2Li(OEt2)2 (2.535(5) Å),13 [cis,cis-1,3,5-
(C6F5N)3C6H9]ZrCH(SiMe3)2 (2.559 Å average),62 HC{Si-
Me2N(2-FC6H4)}3Zr(S2C)Fe(CO)2(δ-C5H5) (2.563(8) Å),54
{K(C7H8)2}{ZrCl2[N(C6F5)2]3} (2.602(2) Å),63 HC{SiMe2N(2-
FC6H4)}3Zr(SCNPh)Fe(CO)2(δ-C5H5) (2.703(11) Å),64 and
[(2,6-F2C6H3NCH2)2C(CH3)(2-C5H4N)]Hf(i-Bu)2 (2.559 Å
average).65 The relatively short distances of M-Cl and M-F
bonds in [iPrAr-NF]2ZrCl2 and [iPrAr-NF]2HfCl2 are reflec-
tive of the highly electrophilic nature of these group 4
complexes. Similar to what has been found for [iPrAr-
NF]Li(OEt2)2, the group 4 metals in [iPrAr-NF]2ZrCl2 and
[iPrAr-NF]2HfCl2 lie virtually on the mean N-phenylene-F
planes and the N-aryl rings are approximately perpendicular
to the corresponding N-phenylene-F planes.
Figure 3. Molecular structure of [iPrAr-NF]2ZrCl2 with thermal ellipsoids
drawn at the 35% probability level. Selected bond distances (Å) and angles
(deg): Zr(1)-N(2) 2.1159(19), Zr(1)-N(1) 2.1298(18), Zr(1)-F(1) 2.3474(14),
Zr(1)-Cl(1) 2.3491(7), Zr(1)-Cl(2) 2.3648(7), Zr(1)-F(2) 2.3796(14),
N(2)-Zr(1)-N(1) 145.44(7), N(2)-Zr(1)-F(1) 83.19(6), N(1)-Zr(1)-F(1)
70.60(6), N(2)-Zr(1)-Cl(1) 102.67(5), N(1)-Zr(1)-Cl(1) 96.84(5),
F(1)-Zr(1)-Cl(1) 162.29(4), N(2)-Zr(1)-Cl(2) 97.83(5), N(1)-Zr(1)-Cl(2)
104.19(5), F(1)-Zr(1)-Cl(2) 90.16(4), Cl(1)-Zr(1)-Cl(2) 105.34(3),
N(2)-Zr(1)-F(2) 69.72(6), N(1)-Zr(1)-F(2) 81.51(6), F(1)-Zr(1)-F(2)
74.35(6), Cl(1)-Zr(1)-F(2) 91.84(5), Cl(2)-Zr(1)-F(2) 160.88(4).
Alkylation of [iPrAr-NF]2ZrCl2 or [iPrAr-NF]2HfCl2 with
a variety of Grignard reagents in diethyl ether at –35 °C
generated the corresponding dialkyl complexes [iPrAr-
NF]2MR2 (M ) Zr, Hf; R ) Me, i-Bu, CH2Ph; Scheme 2)
in high isolated yield. Reminiscent to what has been observed
for [iPrAr-NF]2MCl2, these dialkyl complexes display solu-
tion C2 symmetry on the NMR time scale. The 19F{1H} NMR
spectra exhibit a singlet resonance at ca. -120 ppm. The
ortho-isopropyl substituents on the N-aryl rings are observed
1
Figure 4. Molecular structure of [iPrAr-NF]2HfCl2 with thermal ellipsoids
drawn at the 35% probability level. Selected bond distances (Å) and angles
(deg): Hf(1)-N(2) 2.114(3), Hf(1)-N(1) 2.117(3), Hf(1)-F(1) 2.311(2),
Hf(1)-F(2) 2.312(2), Hf(1)-Cl(1) 2.3340(11), Hf(1)-Cl(2) 2.3358(11),
N(2)-Hf(1)-N(1)144.89(13),N(2)-Hf(1)-F(1)82.64(11),N(1)-Hf(1)-F(1)
70.95(11), N(2)-Hf(1)-F(2) 71.32(11), N(1)-Hf(1)-F(2) 81.25(11),
F(1)-Hf(1)-F(2)79.56(10),N(2)-Hf(1)-Cl(1)102.62(9),N(1)-Hf(1)-Cl(1)
97.94(9), F(1)-Hf(1)-Cl(1) 164.57(8), F(2)-Hf(1)-Cl(1) 88.32(8),
N(2)-Hf(1)-Cl(2) 97.36(9), N(1)-Hf(1)-Cl(2) 104.63(9), F(1)-Hf(1)-Cl(2)
88.86(8), F(2)-Hf(1)-Cl(2) 164.63(8), Cl(1)-Hf(1)-Cl(2) 104.63(5).
in the H NMR spectra as one septet resonance for the
methine and two doublet resonances for the methyl groups.
A variable-temperature 1H NMR study of [iPrAr-NF]2ZrMe2
(58) Manzer, L. E. Inorg. Synth. 1982, 21, 135–140.
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549–551.
on the mean MF2Cl2 plane and bisects the Cl-M-Cl angle.
The chirality of the molecules shown in Figures 3 and 4is
Λ. We suggest that possible stereoisomers other than
conformation III and its enantiomer be virtually not present
in the reaction mixture on the basis of the nearly quantitative
isolated yield and the solution NMR studies that display only
(62) Turculet, L.; Tilley, T. D. Organometallics 2002, 21, 3961–3972.
(63) Giesbrecht, G. R.; Gordon, J. C.; Clark, D. L.; Hijar, C., A.; Scott,
B. L.; Watkin, J. G. Polyhedron 2003, 22, 153–163.
(64) Gade, L. H.; Memmler, H.; Kauper, U.; Schneider, A.; Fabre, S.;
Bezougli, I.; Lutz, M.; Galka, C.; Scowen, I. J.; McPartlin, M.
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(65) Schrock, R. R.; Adamchuk, J.; Ruhland, K.; Lopez, L. P. H.
Organometallics 2003, 22, 5079–5091.
3302 Inorganic Chemistry, Vol. 47, No. 8, 2008

Fluorinated Diarylamido Complexes of Li, Zr, and Hf
Scheme 2
(toluene-d8) revealed that these signals do not tend to broaden
at temperatures higher than -80 °C, implying a rapid rotation
nonmetallocene catalysts for stereospecific polymerization
of R-olefins.66–72 The chirality of [iPrAr-NF]2ZrMe2 shown
in Figure 5 is ∆, whereas that of [iPrAr-NF]2Zr(i-Bu)2 and
[iPrAr-NF]2Hf(CH2Ph)2 illustrated in Figures 6 and 7,
respectively, is Λ. The M-F distances in [iPrAr-NF]2ZrMe2
(2.446 Å average), [iPrAr-NF]2Zr(i-Bu)2 (2.454 Å average),
and [iPrAr-NF]2Hf(CH2Ph)2 (2.411 Å average) are all slightly
longer than those of the corresponding dichloride complexes,
consistent with the greater trans influence of an alkyl than a
chloride. The discrepancy in M-F distances is also ascribable
to the somewhat more electrophilic metals of the dichloride
complexes than those of the dialkyl counterparts (electrone-
gativity: Cl 3.16, C 2.55).73 The benzyl ligands in [iPrAr-
NF]2Hf(CH2Ph)2 adopt an R1-coordination mode as evi-
denced by the Hf-C distances and the Hf-C-C angles.
of the N-aryl rings about the N-Ar bonds.59 The H and
1
13C{1H} NMR spectra exhibit only one set of resonances
corresponding to the Zr- or Hf-bound alkyl ligands. The
triplet resonances found for the CR atoms (2JCRF ) ca. 14
Hz) in the 13C{1H} NMR spectra of these dialkyl species
are indicative of the coordination of the two o-fluorine atoms
in these molecules. The stereochemistry of [iPrAr-NF]2MR2
is thus presumably analogous to that of their dichloride
precursors.
Single crystals of [iPrAr-NF]2ZrMe2, [iPrAr-NF]2Zr(i-Bu)2,
and [iPrAr-NF]2Hf(CH2Ph)2 suitable for X-ray diffraction
analysis were grown from a concentrated diethyl ether
solution at –35 °C. As depicted in Figures 5-7, these dialkyl
complexes are six-coordinate species with core structures
analogous to those of the dichloride derivatives. These results
are consistent with those determined by NMR spectroscopic
studies. It is interesting to note that these C2-symmetric group
4 dichloride and dialkyl complexes featuring two mutually
cis-chloride or alkyl ligands, respectively, fall into the
territory of the popular motifs for the development of
Conclusions
In summary, we have prepared and characterized a series
of o-fluorinated diarylamido complexes of lithium, zirconium,
and hafnium. The solution- and solid-state structures of these
complexes have been established by multinuclear NMR
spectroscopy and X-ray crystallography, respectively. Con-
sistent with its weakly coordinating nature, the fluorine donor
in [iPrAr-NF]Li and [iPrAr-NF]Li(OEt2)2seems to dissociate
readily from the lithium atom in solution. With the coordina-
tion of the o-fluorine atoms, the group 4 complexes reported
herein are all six-coordinate species that adopt selectively a
C2-symmetric structure with the two chlorides or alkyls
having cis orientation. This result is of particular interest as
no internal symmetry is inherently imposed by the ligands
employed. The C2-symmetric structure found for [iPrAr-
NF]2MX2 (M ) Zr, Hf; X ) Cl, alkyl) in this study is
(66) Tshuva, E. Y.; Goldberg, I.; Kol, M. J. Am. Chem. Soc. 2000, 122,
10706–10707.
(67) Cohen, A.; Yeori, A.; Goldberg, I.; Kol, M. Inorg. Chem. 2007, 46,
8114–8116.
Figure 5. Molecular structure of [iPrAr-NF]2ZrMe2 with thermal ellipsoids
drawn at the 35% probability level. The asymmetric unit cell contains two
independent molecules; only one is shown for clarity. Selected bond
distances (Å) and angles (deg): Zr(1)-N(1) 2.134(3), Zr(1)-N(2) 2.151(3),
Zr(1)-C(19) 2.216(5), Zr(1)-C(20) 2.228(5), Zr(1)-F(2) 2.418(3),
Zr(1)-F(1) 2.473(3), N(1)-Zr(1)-N(2) 139.62(13), N(1)-Zr(1)-C(19)
104.13(17), N(2)-Zr(1)-C(19) 98.91(17), N(1)-Zr(1)-C(20) 101.98(17),
N(2)-Zr(1)-C(20)103.84(18),C(19)-Zr(1)-C(20)104.3(2),N(1)-Zr(1)-F(2)
82.75(12), N(2)-Zr(1)-F(2) 69.56(11), C(19)-Zr(1)-F(2) 167.19(16),
C(20)-Zr(1)-F(2) 84.4(2), N(1)-Zr(1)-F(1) 68.69(11), N(2)-Zr(1)-F(1)
81.85(11), C(19)-Zr(1)-F(1) 83.22(18), C(20)-Zr(1)-F(1) 169.48(17),
F(2)-Zr(1)-F(1) 89.42(12).
(68) Segal, S.; Goldberg, I.; Kol, M. Organometallics 2005, 24, 200–202.
(69) Yeori, A.; Goldberg, I.; Shuster, M.; Kol, M. J. Am. Chem. Soc. 2006,
128, 13062–13063.
(70) Capacchione, C.; Proto, A.; Ebeling, H.; Mulhaupt, R.; Moller, K.;
Spaniol, T. P.; Okuda, J. J. Am. Chem. Soc. 2003, 125, 4964–4965.
(71) Capacchione, C.; De Carlo, F.; Zannoni, C.; Okuda, J.; Proto, A.
Macromolecules 2004, 37, 8918–8922.
(72) Beckerle, K.; Manivannan, R.; Spaniol, T. P.; Okuda, J. Organome-
tallics 2006, 25, 3019–3026.
(73) Pauling, L. The Nature of the Chemical Bond, 3rd ed.; Cornell
University Press: Ithaca, NY, 1960; p 93.
Inorganic Chemistry, Vol. 47, No. 8, 2008 3303

Lee et al.
constants (J) and peak widths at half-height (∆V1/2) are in hertz.
1H and 13C NMR spectra are referenced using the residual solvent
peak at δ 7.16 and 128.39, respectively, for C6D6. The assignment
of the carbon atoms is based on the DEPT 13C NMR spectroscopy.
19F and 7Li NMR spectra are referenced externally using CFCl3 in
CHCl3 at δ 0, respectively. Routine coupling constants are not listed.
All NMR spectra were recorded at room temperature in specified
solvents unless otherwise noted. Elemental analysis was performed
on a Heraeus CHN-O rapid analyzer.
Materials. Compounds N-(2-fluorophenyl)-2,6-diisopropylaniline
(H[iPrAr-NF])45 and MCl4(THF)2 (M ) Zr, Hf)58 were prepared
according to the literature procedures. All other chemicals were
obtained from commercial vendors and used as received.
X-ray Crystallography. Table 1 summarizes the crystallographic
data for [iPrAr-NF]Li(OEt2)2, [iPrAr-NF]2ZrCl2, [iPrAr-NF]2HfCl2,
[iPrAr-NF]2ZrMe2, [iPrAr-NF]2Zr(i-Bu)2, and [iPrAr-NF]2Hf-
(CH2Ph)2. Data were collected on a Bruker-Nonius Kappa CCD
diffractometer with graphite monochromated Mo KR radiation (λ
) 0.7107 Å). Structures were solved by direct methods and refined
by full matrix least-squares procedures against F2 using WinGX
crystallographic software package or SHELXL-97. All full-weight
non-hydrogen atoms were refined anisotropically. Hydrogen atoms
were placed in calculated positions.
Figure 6. Molecular structure of [iPrAr-NF]2Zr(i-Bu)2 with thermal
ellipsoids drawn at the 35% probability level. Selected bond distances (Å)
and angles (deg): Zr(1)-N(2) 2.159(4), Zr(1)-N(1) 2.159(4), Zr(1)-C(37)
2.203(5), Zr(1)-C(41) 2.211(5), Zr(1)-F(2) 2.438(3), Zr(1)-F(1) 2.470(3),
N(2)-Zr(1)-N(1)139.00(14),N(2)-Zr(1)-C(37)97.88(17),N(1)-Zr(1)-C(37)
109.36(17), N(2)-Zr(1)-C(41) 108.44(17), N(1)-Zr(1)-C(41) 99.20(18),
C(37)-Zr(1)-C(41) 95.1(2), N(2)-Zr(1)-F(2) 68.60(12), N(1)-Zr(1)-F(2)
78.53(11), C(37)-Zr(1)-F(2) 163.97(17), C(41)-Zr(1)-F(2) 97.32(17),
N(2)-Zr(1)-F(1) 81.24(11), N(1)-Zr(1)-F(1) 68.74(12), C(37)-Zr(1)-F(1)
90.67(17), C(41)-Zr(1)-F(1) 167.83(16), F(2)-Zr(1)-F(1) 79.07(10).
Synthesis of Lithium N-(2-Fluorophenyl)-2,6-diisopropyla-
nilide, [iPrAr-NF]Li, and Its Diethyl Ether Adduct, [iPrAr-
NF]Li(OEt2)2. Compound H[iPrAr-NF] (1.007 g, 3.71 mmol) was
dissolved in toluene (10 mL) and cooled to -35 °C. To this was
added n-BuLi (2.32 mL, 1.6 M in hexane, Aldrich, 3.71 mmol)
dropwise. The reaction solution was stirred at room temperature
for 3 h and evaporated to dryness under reduced pressure. The red,
viscous residue was triturated with pentane (10 mL) to afford the
product as an off-white solid, which was isolated, washed with
pentane (5 mL × 2), and dried in vacuo: yield 798.4 mg (78%);
1H NMR (C6D6, 500 MHz) δ 7.06 (s, 3, Ar), 6.95 (dd, 1, Ar), 6.79
(t, 1, Ar), 6.26 (q, 1, Ar), 6.14 (t, 1, Ar), 3.03 (septet, 2, CHMe2),
1.03 (d, 6, CHMe2), 0.74 (d, 6, CHMe2); 7Li{1H} NMR (C6D6, 194
MHz) δ 1.64 (V1/2 ) 8.97 Hz); 19F NMR (C6D6, 188.15 MHz) δ
-148.51; 13C{1H} NMR (C6D6, 125.5 MHz) δ 156.63 (d, JCF
214.10, CF), 147.75 (d, JCF ) 8.16, C), 145.72 (s, C), 14.99 (s, C),
127.01 (s, CH), 125.50 (s, CH), 125.17 (s, CH), 115.88 (d, JCF
)
)
6.40, CH), 113.99 (d, JCF ) 21.96, CH), 111.71 (d, JCF ) 9.16,
CH), 27.93 (s, CHMe2), 25.11 (s, CHMe2), 24.79 (s, CHMe2). Anal.
Calcd for C18H21FLiN: C, 77.93; H, 7.64; N, 5.05. Found: C, 77.60;
H, 8.07; N, 4.69. Recrystallization of the off-white solid [iPrAr-
NF]Li from a concentrated diethyl ether solution at –35 °C gave
colorless crystals of [iPrAr-NF]Li(OEt2)2 suitable for X-ray dif-
Figure 7. Molecular structure of [iPrAr-NF]2Hf(CH2Ph)2 with thermal
ellipsoids drawn at the 35% probability level. Selected bond distances (Å)
and angles (deg): Hf(1)-N(2) 2.130(4), Hf(1)-N(1) 2.147(4), Hf(1)-C(44)
2.220(4), Hf(1)-C(37) 2.221(5), Hf(1)-F(1) 2.367(3), Hf(1)-F(2) 2.454(3),
N(2)-Hf(1)-N(1)138.91(14),N(2)-Hf(1)-C(44)110.63(16),N(1)-Hf(1)-C(44)
92.67(16), N(2)-Hf(1)-C(37) 103.73(16), N(1)-Hf(1)-C(37) 106.12(16),
C(44)-Hf(1)-C(37)97.72(19),N(2)-Hf(1)-F(1)84.31(12),N(1)-Hf(1)-F(1)
70.14(12), C(44)-Hf(1)-F(1) 162.77(15), C(37)-Hf(1)-F(1) 86.49(15),
N(2)-Hf(1)-F(2) 68.87(11), N(1)-Hf(1)-F(2) 83.63(12), C(44)-Hf(1)-F(2)
79.38(16), C(37)-Hf(1)-F(2) 170.03(14), F(1)-Hf(1)-F(2) 99.09(11)
1
fraction analysis: H NMR (C6D6, 500 MHz) δ 7.35 (d, 2, Ar),
7.23 (t, 1, Ar), 7.03 (dd, 1, Ar), 6.89 (t, 1, Ar), 6.32 (dd, 1, Ar),
6.15 (q, 1, Ar), 3.60 (septet, 2, CHMe2), 3.06 (q, 8, OCH2CH3),
1.31 (d, 6, CHMe2), 1.22 (d, 6, CHMe2), 0.83 (d, 12, OCH2CH3);
7Li{1H} NMR (C6D6, 194 MHz) δ 1.12 (V1/2 ) 7.68 Hz); 19F NMR
(C6D6, 188.15 MHz) δ -148.97; 13C{1H} NMR (C6D6, 125.5 MHz)
conceptually analogous to that of ansa-metallocenes and their
noncyclopentadienyl alternatives. Studies directed to delin-
eate the reactivity of these molecules are currently underway.
δ 157.00 (d, JCF ) 214.10, CF), 150.53 (s, C), 149.73 (d, JCF
)
8.16, C), 145.15 (s, C), 127.21 (s, CH), 124.30 (s, CH), 122.84 (s,
CH), 114.83 (d, JCF ) 6.78, CH), 113.23 (d, JCF ) 20.71, CH),
106.39 (d, JCF ) 9.16, CH), 66.28 (s, OCH2CH3), 28.52 (s, CHMe2),
25.53 (s, CHMe2), 25.23 (s, CHMe2), 14.92 (s, OCH2CH3). Anal.
Calcd for C26H41FLiNO2: C, 73.35; H, 9.72; N, 3.29. Found: C,
73.35; H, 9.31; N, 3.77.
Synthesis of [iPrAr-NF]2ZrCl2. Solid ZrCl4(THF)2 (204 mg,
0.54 mmol) was suspended in toluene (5 mL) and cooled to –35
°C. To this was added dropwise a prechilled solution of [iPrAr-
NF]Li (300 mg, 1.08 mmol, 2 equiv) in toluene (5 mL) at –35 °C.
Experimental Section
General Procedures. Unless otherwise specified, all experiments
were performed under nitrogen using standard Schlenk or glovebox
techniques. All solvents were reagent grade or better and purified
by standard methods. The NMR spectra were recorded on Varian
Unity or Bruker AV instruments. Chemical shifts (δ) are listed as
parts per million downfield from tetramethylsilane, and coupling
3304 Inorganic Chemistry, Vol. 47, No. 8, 2008

Fluorinated Diarylamido Complexes of Li, Zr, and Hf
Upon addition, the reaction solution became pale yellow in color
and the suspended ZrCl4(THF)2 dissolved gradually. The reaction
mixture was stirred at room temperature overnight and evaporated
to dryness in vacuo. The solid residue was dissolved in diethyl
ether (15 mL), and the ether solution was filtered through a pad of
Celite, which was further washed with diethyl ether (1 mL × 2).
The filtrates were combined, concentrated under reduced pressure
to ca. 2 mL, and cooled to –35 °C to afford the product as colorless
crystals suitable for X-ray diffraction analysis: yield 312.1 mg
ether, Aldrich, 0.126 mmol, 2 equiv) dropwise. The reaction mixture
was naturally warmed to room temperature and stirred overnight.
The reaction solution was filtered through a pad of Celite,
concentrated under reduced pressure to ca. 3 mL, and cooled to
–35 °C to afford the product as colorless crystals: yield 32.7 mg
1
(69%); H NMR (C6D6, 500 MHz) δ 7.29 (s, 6, Ar), 6.68 (t, 4,
Ar), 6.22 (m, 2, Ar), 6.17 (m, 2, Ar), 3.72 (septet, 4, ArCHMe2),
1.35 (d, 12, CHMe2), 1.12 (d, 12, CHMe2), 0.58 (s, 3, HfCH3); 19
F
NMR (C6D6, 188.15 MHz) δ -123.21; 13C{1H} NMR (C6D6,
125.68 MHz) δ 158.03 (dd, JCF ) 224.21 and 5.40, C), 147.28 (s,
C), 143.50 (dd, JCF ) 6.28 and 3.64, C), 141.88 (s, C), 127.90 (s,
CH), 127.02 (s, CH), 125.69 (s, CH), 117.65 (s, CH), 117.07 (t,
JCF ) 4.52, CH), 113.45 (dd, JCF ) 12.80 and 7.28, CH), 63.79 (t,
2JCF ) 13.68, HfCH3), 28.39 (s, CHMe2), 26.58 (s, CHMe2), 24.95
(s, CHMe2).
1
(82%); H NMR (C6D6, 500 MHz) δ 7.26 (m, 6, Ar), 6.65 (q, 2,
Ar), 6.61 (t, 2, Ar), 6.22 (m, 2, Ar), 6.05 (m, 2, Ar), 3.63 (septet,
4, CHMe2), 1.48 (d, 12, CHMe2), 1.07 (d, 12, CHMe2); 19F NMR
(C6D6, 188.15 MHz) δ -115.61; 13C{1H} NMR (C6D6, 125.679
1
3
MHz) δ 159.03 (dd, JCF ) 226.47, JCF ) 7.04, CF), 146.35 (s,
C), 142.11 (s, C), 141.74 (m, C), 128.75 (s, CH), 127.47 (s, CH),
125.81 (s, CH), 118.81 (t, JCF ) 6.03, CH), 116.73 (s, CH), 113.07
(dd, JCF ) 13.07, 8.04, CH), 28.59 (s, CHMe2), 26.40 (s, CHMe2),
25.00 (s, CHMe2). Anal. Calcd for C36H42Cl2F2N2Zr: C, 61.50; H,
6.03; N, 3.99. Found: C, 61.08; H, 6.10; N, 3.86.
Synthesis of [iPrAr-NF]2Zr(i-Bu)2. Solid [iPrAr-NF]2ZrCl2
(104.9 mg, 0.15 mmol) was dissolved in diethyl ether (3 mL) and
i
cooled to –35 °C. To this was added BuMgCl (0.15 mL, 2 M in
diethyl ether, Aldrich, 0.30 mmol, 2 equiv) dropwise. The reaction
mixture was naturally warmed to room temperature and stirred
overnight. The reaction solution was filtered through a pad of Celite,
concentrated under reduced pressure to ca. 3 mL, and cooled to
–35 °C to afford the product as colorless crystals suitable for X-ray
Synthesis of [iPrAr-NF]2HfCl2. Solid HfCl4(THF)2 (251 mg,
0.54 mmol) was suspended in toluene (5 mL) and cooled to –35
°C. To this was added dropwise a prechilled solution of [iPrAr-
NF]Li (300 mg, 1.08 mmol, 2 equiv) in toluene (5 mL) at –35 °C.
Upon addition, the reaction mixture became pale green in color
and the suspended HfCl4(THF)2 dissolved gradually. The reaction
mixture was stirred at room temperature overnight. All volatiles
were removed in vacuo. The solid residue was dissolved in diethyl
ether (15 mL). The ether solution was filtered through a pad of
Celite, which was further washed with diethyl ether (1 mL × 2).
The filtrates were combined, concentrated under reduced pressure
to ca. 2 mL, and cooled to -35 °C to afford the product as colorless
crystals suitable for X-ray diffraction analysis: yield 330.8 mg
1
diffraction analysis: yield 99.7 mg (90%); H NMR (C6D6, 500
MHz) δ 7.33 (m, 6, Ar), 6.77 (dd, 2, Ar), 6.65 (t, 2, Ar), 6.26 (dd,
2, Ar), 6.18 (m, 2, Ar), 3.85 (septet, 4, ArCHMe2), 1.81 (septet, 2,
ZrCH2CHMe2), 1.48 (d, 12, CHMe2), 1.44 (d, 4, ZrCH2CHMe2),
1.15 (d, 12, CHMe2), 0.67 (d, 12, CHMe2); 19F NMR (C6D6, 188.15
MHz) δ –122.97; 13C{1H} NMR (C6D6, 125.679 MHz) δ 157.08
(dd, 1JCF ) 223.46, 3JCF ) 2.76, CF), 146.75 (s, C), 143.55 (t, JCF
) 4.52, C), 127.62 (s, CH), 126.61 (s, CH), 125.69 (s, CH), 117.79
(s, CH), 117.00 (t, JCF ) 5.53, CH), 113.48 (dd, JCF ) 13.70, JCF
1
2
(77%); H NMR (C6D6, 500 MHz) δ 7.27 (s, 6, Ar), 6.62 (m, 4,
) 6.41, CH), 94.53 (t, JCF ) 14.20, ZrCH2), 30.73 (s, CHMe2),
Ar), 6.16 (m, 2, Ar), 6.07 (m, 2, Ar), 3.63 (septet, 4, CHMe2),
1.47 (d, 12, CHMe2), 1.09 (d, 12, CHMe2); 19F NMR (C6D6, 188.15
MHz) δ -118.53; 13C{1H} NMR (C6D6, 125.679 MHz) δ 159.79
(dd, 1JCF ) 222.45, 3JCF ) 7.54, CF), 146.73 (s, C), 142.25 (s, C),
142.21 (m, C), 128.68 (s, CH), 127.73 (s, CH), 124.64 (s, CH),
120.50 (t, d, JCF ) 10.04, CH), 117.62 (s, CH), 112.91 (m, CH),
28.45 (s, CHMe2), 26.35 (s, CHMe2), 25.06 (s, CHMe2). Anal. Calcd
for C36H42Cl2F2HfN2: C, 54.70; H, 5.36; N, 3.55. Found: C, 54.44;
H, 5.39; N, 3.44.
28.57 (s, CHMe2), 27.83 (s, CHMe2), 26.91 (s, CHMe2), 24.63 (s,
CHMe2).
Synthesis of [iPrAr-NF]2Hf(i-Bu)2. Solid [iPrAr-NF]2HfCl2 (50
mg, 0.063 mmol) was dissolved in diethyl ether (3 mL) and cooled
to –35 °C. To this was added iBuMgCl (0.063 mL, 2 M in diethyl
ether, Aldrich, 0.126 mmol, 2 equiv) dropwise. The reaction mixture
was naturally warmed to room temperature and stirred overnight.
The reaction solution was filtered through a pad of Celite,
concentrated under reduced pressure to ca. 3 mL, and cooled to
–35 °C to afford the product as colorless crystals: yield 48.9 mg
Synthesis of [iPrAr-NF]2ZrMe2. Solid [iPrAr-NF]2ZrCl2 (100
mg, 0.14 mmol) was dissolved in diethyl ether (3 mL) and cooled
to –35 °C. To this was added MeMgBr (0.09 mL, 3 M in diethyl
ether, Aldrich, 0.27 mmol, 1.93 equiv) dropwise. The reaction
mixture was naturally warmed to room temperature and stirred
overnight. The reaction solution was filtered through a pad of Celite,
concentrated under reduced pressure to ca. 3 mL, and cooled to
–35 °C to afford the product as colorless crystals: yield 85.0 mg
1
(93%); H NMR (C6D6, 500 MHz) δ 7.33 (m, 6, Ar), 6.78 (q, 2,
Ar), 6.65 (t, 2, Ar), 6.22 (q, 2, Ar), 6.16 (t, 2, Ar), 3.85 (septet, 4,
ArCHMe2), 1.90 (m, 2, HfCH2CHMe2), 1.49 (d, 12, CHMe2), 1.14
(d, 12, CHMe2), 1.10 (d, 4, J ) 6.5, HfCH2CHMe2), 0.69 (d, 12,
CHMe2); 19F NMR (C6D6, 188.15 MHz) δ –122.49; 13C{1H} NMR
(C6D6, 125.5 MHz) δ 157.73 (dd, 1JCF ) 222.07, 3JCF ) 2.76, CF),
147.10 (s, C), 143.73 (dd, JCF ) 7.34 and 2.26, C), 143.40 (s, C),
127.62 (s, CH), 126.85 (s, CH), 125.70 (s, CH), 118.49 (s, CH),
116.85 (t, JCF ) 4.52, CH), 113.40 (dd, JCF ) 13.68 and 5.90,
CH), 99.22 (t, 2JCF ) 14.68, HfCH2), 30.29 (s, CHMe2), 28.80 (s,
CHMe2), 28.46 (s, CHMe2), 26.98 (s, CHMe2), 24.60 (s, CHMe2).
Synthesis of [iPrAr-NF]2Zr(CH2Ph)2. Solid [iPrAr-NF]2ZrCl2
(100 mg, 0.14 mmol) was dissolved in diethyl ether (3 mL) and
cooled to –35 °C. To this was added PhCH2MgCl (0.28 mL, 1 M
in diethyl ether, Aldrich, 0.28 mmol, 2 equiv) dropwise. The
reaction mixture was naturally warmed to room temperature and
stirred overnight. The reaction solution was filtered through a pad
of Celite, concentrated under reduced pressure to ca. 3 mL, and
cooled to –35 °C to afford the product as colorless crystals: yield
1
(90%); H NMR (C6D6, 500 MHz) δ 7.29 (s, 6, Ar), 6.68 (t, 4,
Ar), 6.27 (m, 2, Ar), 6.18 (m, 2, Ar), 3.72 (septet, 4, ArCHMe2),
1.34 (d, 12, CHMe2), 1.12 (d, 12, CHMe2), 0.81 (s, 6, ZrCH3); 19
F
NMR (C6D6, 188.15 MHz) δ -123.14; 13C{1H} NMR (C6D6,
125.68 MHz) δ 157.45 (dd, JCF ) 226.64 and 5.02, CF), 147.10
(s, C), 143.15 (dd, JCF ) 7.03 and 3.01, C), 141.65 (s, C), 128.03
(s, CH), 126.76 (s, CH), 125.70 (s, CH), 117.32 (t, JCF ) 4.02,
CH), 116.96 (s, CH), 113.52 (dd, JCF ) 13.11 and 7.03, CH), 56.62
2
(t, JCF ) 13.58, ZrCH3), 28.53 (s, CHMe2), 26.57 (s, CHMe2),
24.92 (s, CHMe2).
Synthesis of [iPrAr-NF]2HfMe2. Solid [iPrAr-NF]2HfCl2 (50
mg, 0.063 mmol) was dissolved in diethyl ether (3 mL) and cooled
to –35 °C. To this was added MeMgBr (0.042 mL, 3 M in diethyl
1
103.1 mg (89%); H NMR (C6D6, 500 MHz) δ 7.31 (m, 6, Ar),
Inorganic Chemistry, Vol. 47, No. 8, 2008 3305

Lee et al.
6.88 (t, 4, Ar), 6.70 (t, 2, Ar), 6.56 (td, 2, Ar), 6.52 (m, 6, Ar),
6.25 (q, 2, Ar), 6.01 (t, 2, Ar), 3.52 (septet, 4, ArCHMe2), 2.94 (s,
4, ZrCH2Ph), 1.23 (d, 12, CHMe2), 0.99 (d, 12, CHMe2); 19F NMR
(C6D6, 188.15 MHz) δ 116.17; 13C{1H} NMR (C6D6, 125.68 MHz)
δ 157.06 (d, 1JCF ) 221.88, CF), 147.17 (s, C), 145.04 (s, C), 143.18
(d, JCF ) 10.17, C), 142.67 (s, C), 128.66 (s, CH), 128.04 (s, CH),
126.89 (s, CH), 126.23 (s, CH), 125.84 (s, CH), 122.60 (s, CH),
118.03 (s, CH), 117.63 (dd, JCF ) 4.58 and 3.77, CH), 113.88 (dd,
JCF ) 19.70 and 7.78, CH), 84.29 (t, 2JCF ) 15.06, ZrCH2Ph), 29.03
(s, ArCHMe2), 27.02 (s, ArCHMe2), 24.24 (s, ArCHMe2).
(s, C), 143.43 (d, JCF ) 9.66, C), 142.90 (s, C), 128.32 (s, CH),
127.94 (s, CH), 127.25 (s, CH), 126.62 (s, CH), 125.97(s, CH),
122.69 (s, CH), 118.54 (s, CH), 117.42 (t, JCF ) 4.52, CH), 113.64
(dd, JCF ) 10.04 and 4.64, CH), 89.45 (t, 2JCF ) 15.06, HfCH2Ph),
28.82 (s, CHMe2), 27.04 (s, CHMe2), 24.19 (s, CHMe2).
Acknowledgment. We thank the National Science Council
of Taiwan for financial support (NSC 96-2628-M-110-007-
MY3) of this work, Ms. Chao-Lien Ho (NSYSU) and Ms.
Ru-Rong Wu (National Cheng Kung University) for technical
assistance with NMR experiments, Mr. Ting-Shen Kuo
(National Taiwan Normal University) for assistance with
X-ray crystallography, and the National Center for High-
Performance Computing (NCHC) for computer time and
facilities.
Synthesis of [iPrAr-NF]2Hf(CH2Ph)2. Solid [iPrAr-NF]2HfCl2
(100 mg, 0.127 mmol) was dissolved in diethyl ether (3 mL) and
cooled to –35 °C. To this was added PhCH2MgCl (0.254 mL, 1 M
in diethyl ether, Aldrich, 0.254 mmol, 2 equiv) dropwise. The
reaction mixture was naturally warmed to room temperature and
stirred overnight. The reaction solution was filtered through a pad
of Celite, concentrated under reduced pressure to ca. 3 mL, and
cooled to –35 °C to afford the product as pale yellow crystals: yield
Supporting Information Available: X-ray crystallographic data
in CIF format for [iPrAr-NF]Li(OEt2)2, [iPrAr-NF]2ZrCl2, [iPrAr-
NF]2HfCl2, [iPrAr-NF]2ZrMe2, [iPrAr-NF]2Zr(i-Bu)2, and [iPrAr-
NF]2Hf(CH2Ph)2. This material is available free of charge via the
Internet at http://pubs.acs.org.
1
89.4 mg (78%); H NMR (C6D6, 500 MHz) δ 7.34 (m, 6, Ar),
6.87 (t, 4, Ar), 6.66 (t, 2, Ar), 6.59 (t, 2, Ar), 6.49 (dd, 2, Ar), 6.29
(d, 4, Ar), 6.20 (q, 2, Ar), 6.07 (t, 2, Ar), 3.69 (m, 4, ArCHMe2),
2.61 (s, 4, HfCH2Ph), 1.24 (d, 12, CHMe2), 1.05 (d, 12, CHMe2);
19F NMR (C6D6, 188.15 MHz) δ 117.92; 13C{1H} NMR (C6D6,
125.5 MHz) δ 157.75 (d, JCF ) 220.00, CF), 147.39 (s, C), 144.96
IC702293D
3306 Inorganic Chemistry, Vol. 47, No. 8, 2008