[H(OEt2)2]+ and [Ph3C] + salts of the borate anions [B(CF3)4] -, [(CF3)3BCN]-, and [B(CN) 4]-

Article abstract of DOI:10.1021/om050463j

The reaction of gaseous HCl with K[B(CF₃)₄] in diethyl ether gave the oxonium acid [H(OEt₂)₂][B(CF ₃)₄] as a stable salt at room temperature. Syntheses of [Ph₃C] [B(CF₃

Full text of DOI:10.1021/om050463j

Organometallics 2005, 24, 5103-5109
5103
[H(OEt2)2]+ and [Ph3C]+ Salts of the Borate Anions
[B(CF3)4]-, [(CF3)3BCN]-, and [B(CN)4]-
Maik Finze,*,†,§ Eduard Bernhardt,† Michael Berkei,† Helge Willner,*,†
Joyce Hung,‡ and Robert M. Waymouth*,‡
FB C-Anorganische Chemie, Bergische Universita¨t Wuppertal, Gaussstrasse 20,
D-42097 Wuppertal, Germany, and Department of Chemistry, Stanford University,
Stanford, California 94305
Received June 8, 2005
The reaction of gaseous HCl with K[B(CF3)4] in diethyl ether gave the oxonium acid
[H(OEt2)2][B(CF3)4] as a stable salt at room temperature. Syntheses of [Ph3C][B(CF3)4] and
[Ph3C][(CF3)3BCN] were accomplished from the corresponding potassium salts and Ph3CCl.
The metathesis reaction of Ag[B(CN)4] with trityl bromide resulted in formation of [Ph3C]-
[B(CN)4]. Treatment of Cp2ZrMe2 with [H(OEt2)2][B(CF3)4], [Ph3C][B(CF3)4], [Ph3C][(CF3)3-
BCN], and [Ph3C][B(CN)4], monitored by NMR spectroscopy, showed the formation of
[Cp2ZrMe(OEt2)]+, [(Cp2ZrMe)2-µ-Me]+, [Cp2ZrMe]+, Cp2ZrMe{NCB(CF3)3}, and Cp2Zr{NCB-
(CN)3}2, respectively. Attempted polymerizations of propene with catalysts generated in situ
from rac-Et(1-Ind)2ZrMe2 and [H(OEt2)2][B(CF3)4], [Ph3C][B(CF3)4], or [Ph3C][B(CN)4] yielded
only little to no polymer, possibly due to the low solubility of the catalysts in the reaction
medium.
Introduction
was achieved by isomerization of the [(CF3)3BNC]-
anion8 or by dehydration of [(CF3)3BC(O)NH2]- with
phosgene in the presence of triethylamine.9
Recently we reported the synthesis of salts of the
weakly coordinating tetrakis(trifluoromethyl)borate an-
ion, [B(CF3)4]-,1 by fluorination of the tetracyanoborate
anion, [B(CN)4]-,2 in anhydrous HF using either ClF
or ClF3 as fluorinating agent.1,3 The ability of [B(CF3)4]-
to stabilize unusual cations was demonstrated by the
formation of [Ag(CO)4]+,1 and furthermore Li[B(CF3)4]
was shown to be an excellent conducting salt for lithium
ion batteries.3 Tetracyanoborates are now easily acces-
sible by heating a mixture of K[BF4], KCN, and LiCl.4
In contrast to the [B(CF3)4]- anion, [B(CN)4]- exhibits
a rich coordination chemistry.5-7 While the [B(CN)4]-
anion has four and [B(CF3)4]- has practically no coor-
dination site, the related tris(trifluoromethyl)cyanobo-
rate anion, [(CF3)3BCN]-, can coordinate via its cyano
ligand.8 The synthesis of salts of the [(CF3)3BCN]- anion
The influence of the counteranion on the polymeri-
zation behavior of cationic group 4 metallocene com-
plexes in the homogeneous Ziegler-Natta catalysis is
subject to detailed investigations, and the pivotal role
of the anion depending on its stability, coordinating
ability, and influence on the solubility of the ion pair is
widely recognized.10-13 A general procedure for the
formation of the catalytically active species, for example,
[Cp* ZrMe]+, is the abstraction of a Me- ligand from a
2
suitable metallocene complex by methylalumoxane
(MAO), trityl salts, [Ph3C]X, or a proton source, e.g.,
[H(OEt2)2]+ salts.10,11,13
In this study we report the syntheses of the new salts
[H(OEt2)2][B(CF3)4] and [Ph3C]X (X ) [B(CF3)4]-,
[(CF3)3BCN]-, [B(CN)4]-). Reactions of Cp2ZrMe2 with
the potential cocatalysts in deuterated dichloromethane
or toluene were monitored by NMR spectroscopy, and
furthermore the polymerization of propene with rac-Et-
(1-Ind)2ZrMe2 and [H(OEt2)2][B(CF3)4], [Ph3C][B(CF3)4],
or [Ph3C][B(CN)4] was studied.
* To whom correspondence should be addressed. M.F.: Tel: (+49)
211-81-13144. E-mail: maik.finze@uni-duesseldorf.de. H.W.: Tel: (+49)
202-439-2517. Fax: (+49) 202-439-3052. E-mail: willner@uni-wup-
pertal.de. R.M.W.: Tel: (+01) 650-723-4515. Fax: (+01) 650-725-0259.
E-mail: waymouth@stanford.edu.
† Bergische Universita¨t Wuppertal.
‡ Stanford University.
§ Current address: Institut fu¨r Anorganische Chemie und Struk-
turchemie II, Heinrich-Heine-Universita¨t Du¨sseldorf, Universita¨tsstrasse
1, D-40225 Du¨sseldorf, Germany.
Results and Discussion
[H(OEt2)2][B(CF3)4]. Similar to the syntheses of
other [H(OEt2)2]+ salts with [B{3,5-(CF3)2C6H3}4]-,14
(1) Bernhardt, E.; Henkel, G.; Willner, H.; Pawelke, G.; Bu¨rger, H.
Chem. Eur. J. 2001, 7, 4696.
(2) Bernhardt, E.; Henkel, G.; Willner, H. Z. Anorg. Allg. Chem.
2000, 626, 560.
(3) Schmidt, M.; Ku¨hner, A.; Willner, H.; Bernhardt, E. Deutschland
EP1205480(A2), 2002.
(8) Finze, M.; Bernhardt, E.; Lehmann, C. W.; Willner, H. J. Am.
Chem. Soc. 2005, 127, 10712.
(9) Finze, M.; Bernhardt, E.; Terheiden, A.; Berkei, M.; Willner, H.;
Christen, D.; Oberhammer, H.; Aubke, F. J. Am. Chem. Soc. 2002,
124, 15385.
(10) Marks, T. J.; Chen, E. X.-Y. Chem. Rev. 2000, 100, 1391.
(11) Lubin, l.; Marks, T. J. Top. Catal. 1999, 7, 97.
(12) Bochmann, M. J. Chem. Soc., Dalton Trans. 1996, 255.
(13) Brintzinger, H. H.; Fischer, D.; Mu¨lhaupt, R.; Rieger, B.;
Waymouth, R. M. Angew. Chem., Int. Ed. Engl. 1995, 34, 1143.
(4) Bernhardt, E.; Finze, M.; Willner, H. Z. Anorg. Allg. Chem. 2003,
629, 1229.
(5) Berkei, M.; Bernhardt, E.; Schu¨rmann, M.; Mehring, M.; Willner,
H. Z. Anorg. Allg. Chem. 2002, 628, 1734.
(6) Bernhardt, E.; Berkei, M.; Schu¨rmann, M.; Willner, H. Z. Anorg.
Allg. Chem. 2003, 629, 677.
(7) Ku¨ppers, T.; Bernhardt, E.; Willner, H.; Rohm, H. W.; Ko¨ckerling,
M. Inorg. Chem. 2005, 44, 1015.
10.1021/om050463j CCC: $30.25 © 2005 American Chemical Society
Publication on Web 09/13/2005

5104 Organometallics, Vol. 24, No. 21, 2005
Finze et al.
CD2Cl2
KA + Ph3CCl
8
RT
[Ph3C]A + KCl (A- ) [B(CF3)4]-, [(CF3)3BCN]-) (2)
However, the corresponding tetracyanoborate salt
cannot be prepared from Ph3CCl and K[B(CN)4]. The
synthesis of [Ph3C][B(CN)4] was achieved by reacting
silver tetracyanoborate with trityl bromide (eq 4).
Ag[B(CN)4] + Ph3CBr CH CN8
3
RT
[Ph3C][B(CN)4] + AgBr (3)
According to DSC measurements the three salts melt
with decomposition at 125 °C ([Ph3C][(CF3)3BCN]), 158
°C ([Ph3C][B(CN)4]), and 235 °C ([Ph3C][B(CF3)4]). A
comparison with the respective decomposition temper-
atures of the potassium salts (320 °C (K[B(CF3)4]), 370
°C (K[(CF3)3BCN]), 510 °C (K[B(CN)4]))1,2,8 indicates
that there is no simple correlation between the thermal
stabilities of different salts with the three borate anions.
The NMR spectroscopic data of the anions in [Ph3C]X
(X ) [B(CF3)4]-, [B(CN)4]-, [(CF3)3BCN]-) dissolved in
CD2Cl2 are identical to those reported previously for
solutions of other salts.1,2,8 The presence of the solvated
trityl cation in the CD2Cl2 solutions was also confirmed
by NMR spectroscopy. Even in the case of [Ph3C]-
[B(CN)4] and [Ph3C][(CF3)3BCN] the NMR data proved
the ionic nature of the compounds and the lack of
coordination of the cyano nitrogen atom to the carboca-
tion. [Ph3C]X (X ) [B(CF3)4]-, [B(CN)4]-) also were
characterized by IR spectroscopy, and the spectra are
displayed in the Supporting Information in Figures S1
and S2. No Raman spectra could be acquired due to
decomoposition in the Nd:YAG laser beam. The anion
bands are easily assigned by comparison with similar
spectra of the respective potassium salts (Tables S1 and
S2).1,2 For [Ph3C][B(CN)4] only one weak band in the
characteristic region for ν(CN) was observed at 2221
cm-1. This value is comparable to that measured for [n-
Bu4N][B(CN)4] (2222 cm-1),2 indicating a similar, very
weak interaction between cations and anions in the solid
state, in contrast to M[B(CN)4] (M ) K, Ag), where
Figure 1. IR and Raman spectrum of [H(OEt2)2][B(CF3)4].
[B(C6F5)4]-,15 [(C3H3N2){B(C6F5)3}2]-,16 or [HCB11-
H5Cl6]-17 as counteranions, the preparation of
[H(OEt2)2][B(CF3)4] was achieved in a metathesis reac-
tion according to eq 1.
Et2O
K[B(CF3)4] + HCl + 2 Et2O -30 °C8
[H(OEt2)2][B(CF3)4] + KCl (1)
Potassium chloride and [H(OEt2)2][B(CF3)4] precipi-
tated quantitatively from the diethyl ether solution. The
insolubility of [H(OEt2)2][B(CF3)4] is contrary to the
behavior of [H(OEt2)2][HCB11H5Cl6]17 or [H(OEt2)2]-
[B(C6F5)4],15 which can be recrystallized from Et2O.
However, the [B(CF3)4]- salt is soluble in methylene
chloride and can be extracted from the salt mixture. The
hygroscopic salt melts at 68 °C, whereas for [H(OEt2)2]-
[B(C6F5)4] a melting point of 148 °C was reported.15
According to DSC measurements decomposition of
[H(OEt2)2][B(CF3)4] takes place at 172 °C.
The 11B, 13C, and 19F NMR chemical shifts and
coupling constants of the anion in CD2Cl2 solution are
nearly identical to those of K[B(CF3)4] measured in CD3-
higher wavenumbers (K+: 2234 cm-1, Ag+: 2257 cm-1
)
1
CN.1 The H and 13C NMR spectroscopic data of the
and hence stronger interactions were found.2 The band
positions of the [Ph3C]+ cation are summarized in Table
S3 and compared to values reported for [Ph3C][BF4].18
In addition Ph3CCl was reacted with K[(CF3)3BNC]
to study the difference in the coordination chemistry of
the -CN versus the -NC substituent toward [Ph3C]+.
The product (CF3)3BNCCPh3 is a molecular complex, as
demonstrated by its NMR spectroscopic properties. The
1H and 13C NMR signals of the Ph3C fragment are
shifted to lower frequencies in comparison to the trityl
cation. The strong interaction between [Ph3C]+ and
[(CF3)3BNC]- is also demonstrated by comparison with
the 11B and 19F NMR chemical shifts of K[(CF3)3BNC]8
(δ(11B) ) -17.5 ppm, δ(19F) ) -67.0 ppm) versus (CF3)3-
BNCCPh3 (δ(11B) ) -14.4 ppm, δ(19F) ) -66.4 ppm).
Another indication for the different bonding situations
are the colors: [Ph3C]X (X ) [B(CF3)4]-, [(CF3)3BCN]-)
exhibit the typical yellow to orange color of the [Ph3C]+
cation, in contrast to the covalently bonded (CF3)3-
cation are in agreement with values reported for other
[H(OEt2)2]+ salts.14-17 Characteristic is the high 1H
NMR resonance frequency at 16.3 ppm.14-17 The salt is
also characterized by IR and Raman spectroscopy
(Figure 1), and most of the anion bands are easily
assigned by comparison to those reported for K[B(CF3)4].1
The remaining bands are similar to those found for
[H(OEt2)2]+ salts with carborate counteranions.17
[Ph3C]X (X ) [B(CF3)4]-, [(CF3)3BCN]-, [B(CN)4]-).
The syntheses of the salts [Ph3C]X (X ) [B(CF3)4]-,
[(CF3)3BCN]-) are straightforward starting from the
corresponding potassium salts and trityl chloride (eq 2).
(14) Jutzi, P.; Mu¨ller, C.; Stammler, A.; Stammler, H.-G. Organo-
metallics 2000, 19, 1442.
(15) Brookhart, M.; Grant, B.; Volpe, A. P. J. Organometallics 1992,
11, 3920.
(16) Vagedes, D.; Erker, G.; Fro¨hlich, R. J. Organomet. Chem. 2002,
641, 148.
(17) Stasko, D.; Hoffmann, S. P.; Kim, K.-C.; Fackler, J. P.; Larsen,
A. S.; Drovetskaya, T.; Tham, F. S.; Reed, A. E.; Rickard, C. E. F.;
Boyd, P. D. W.; Stoyanov, E. S. J. Am. Chem. Soc. 2002, 124, 13869.
(18) Sharp, D. W. A.; Sheppard, N. J. Chem. Soc. 1957, 674.

Salts of Borate Anions
Organometallics, Vol. 24, No. 21, 2005 5105
Table 1. Crystallographic Data of [Ph3C][B(CN)4]
at 173(2) K
empirical formula
C23H15BN4
358.20
fw [g mol-1
]
cryst size [mm]
cryst syst
space group
a, b [Å]
c [Å]
1.3 × 1.3 × 1.5
trigonal
R3h
12.618(2)
21.220(4)
2925.9(9)
6
V [Å3]
Z
F
calc [g cm-3
]
1.220
0.074
µ [mm-1
]
data collection range [deg]
no. of reflns collected/unique
no. of reflns obsd [I > 2σ(I)]
R1 (I > 2σ(I))a
2.10 <θ < 25.99
3216/1012
676
Figure 3. 1H NMR spectra of the reaction of Cp2ZrMe2
with [Ph3C][B(CF3)4] in CD2Cl2.
0.0356
R1 (all data)
0.1027
0.1361
wR2 (all data)b
2
2
2 1/2
a R1 ) (∑||Fo| - |Fc||)/∑|Fo|. b Rw ) [∑w(Fo - Fc )2/∑wFo
] ,
cation similar bond parameters have been found in other
trityl salts.21
weight scheme w ) [σ2(Fo) + (aP)2 + bP]-1, P ) (max(0,Fo2) +
2
2Fc )/3, a ) 0.0447, b ) 0.0000.
NMR Spectroscopic Studies on the Reactions of
[H(OEt2)2][B(CF3)4] and [Ph3C]X (X ) [B(CF3)4]-,
[(CF3)3BCN]-, [B(CN)4]-) with Cp2ZrMe2. According
to Figure 3 the reaction of [Ph3C][B(CF3)4] with
Cp2ZrMe2 at -60 °C leads to the formation of the
dimeric [(Cp2ZrMe)2-µ-Me]+ cation (eq 4).
CD2Cl2
2 Cp2ZrMe2 + [Ph3C][B(CF3)4] -60 °C, 30 min8
[(Cp2ZrMe)2-µ-Me][B(CF3)4] + Ph3CMe (4)
When the temperature was increased to approxi-
mately -25 °C, [(Cp2ZrMe)2-µ-Me]+ reacted further to
form [Cp2ZrMe]+ and Ph3CMe (eq 5).
Figure 2. Ion pair of [PPh3][B(CN)4] in the solid-state
structure (25% probability ellipsoids). Selected bond dis-
tances [Å]: C(1)-C(2), 1.371(2); C(2)-C(3), 1.388(2); C(3)-
C(4), 1.388(2); C(4)-C(5), 1.380(2); C(5)-C(6), 1.415(2),
C(6)-C(7), 1.4463(14); B(1)-C(8), 1.572(4), B(1)-C(9),
1.592(2); N(1)-C(9), 1.152(3); N(2)-C(8), 1.145(3). Selected
bond angles [deg]: B(1)-C(8)-N(2), 180; B(1)-C(9)-N(1),
177.6(2); C(8)-B(1)-C(9), 108.51(11).
[(Cp2ZrMe)2-µ-Me][B(CF3)4] +
CD2Cl2
[Ph3C][B(CF3)4] -60 f 25 °C, 2 h8
2[(Cp2ZrMe)][B(CF3)4] + Ph3CMe (5)
As the temperature was raised slowly to 0 °C and then
to room temperature, the amount of unidentified de-
composition products observed in the NMR spectra
increased. The NMR spectroscopic data of [(Cp2ZrMe)2-
µ-Me][B(CF3)4] and [Cp2ZrMe][B(CF3)4] are collected in
Table 2. The initial formation of the bridged dimeric
zirconocene according to eq 4 was previously described
for similar systems, for example, [Ph3C][B(C6F5)4] and
Cp2ZrMe2.22 A colorless solid of unknown composition
precipitated during the reaction, and its formation rate
increased with increasing temperature. After 15 h at
room temperature only low-intensity signals remained
in the proton spectra, which can be assigned to the cyclo-
pentadienyl ligands. Fast decomposition of the [Cp2-
BNCCPh3, which is colorless. (CF3)3BNCCPh3 is not a
suitable cocatalyst for homogeneous Ziegler-Natta
catalysis or a transfer reagent of the [(CF3)3BNC]- ion.
Structure of [Ph3C][B(CN)4]. [Ph3C][B(CN)4] crys-
tallizes in the trigonal space group R3h with 6 indepen-
dent formula units in the unit cell. Crystallographic
data are collected in Table 1. An ion pair in the crystal
structure with selected bond parameters is depicted in
Figure 2, and a model of the unit cell is displayed in
Figure S3.
The local symmetry of the tetracyanoborate anions
in the crystal structure is C3v but with a very small
distortion from Td symmetry. The trityl cations exhibit
nearly D3 symmetry. The shortest contact between the
cationic C atom and one N atom of the cyano ligands
(3.174(1) Å) is similar to the sum of the van der Waals
radii (∼3.3 Å).19,20 This observation is in agreement with
the spectroscopic results and the ionic structure of
[Ph3C][B(CN)4].
ZrMe]+ cation in CD2Cl2 solution is known.22 In the 11
B
and 19F NMR spectra neither decomposition products
of the counteranion [B(CF3)4]- due to F- abstraction23
nor the possible side products Cp2ZrMeF24,25 or
25-28
Cp2ZrF2
were detected.
(21) Zhou, J.; Lancaster, S. J.; Walker, D. A.; Beck, S.; Thornton-
Pett, M.; Bochmann, M. J. Am. Chem. Soc. 2001, 123, 223.
(22) Bochmann, M.; Lancaster, S. J. Angew. Chem. 1994, 106, 1715.
(23) Finze, M.; Bernhardt, E.; Za¨hres, M.; Willner, H. Inorg. Chem.
2004, 43, 490.
(24) Jordan, R. F.; Bajgur, C. S.; Willett, R.; Scott, B. J. Am. Chem.
Soc. 1986, 108, 7410.
(25) Jordan, R. F. J. Organomet. Chem. 1985, 294, 321.
(26) Jordan, R. F.; Echols, S. F. Inorg. Chem. 1986, 26, 383.
The C-N bond lengths (3 × 1.152(3) Å, 1.145(3) Å)
and d(B-C) (3 × 1.572(4) Å, 1.592(2) Å) are comparable
to values of other tetracyanoborates.2,7 For the [Ph3C]+
(19) Bondi, A. J. Phys. Chem. 1964, 68, 441.
(20) Alcock, N. W. Adv. Inorg. Radiochem. 1972, 1, 15.

5106 Organometallics, Vol. 24, No. 21, 2005
Finze et al.
Table 2. NMR Spectroscopic Data of the Products of the Reactions of Cp2ZrMe2 with [Ph3C][B(CF3)4],
[Ph3C][(CF3)3BCN], [Ph3C][B(CN)4], and [H(OEt2)2][B(CF3)4]a,b
[Cp2ZrMe][B(CF3)4]
δ(1H) ) 0.74 (CH3; 3 H), 6.34 (C5H5; 10 H);
δ(11B) ) -18.9; δ(19F) ) -61.6; 2J(11B,19F) ) 25.9
[{Cp2ZrMe}2-µ-Me][B(CF3)4]
[Cp2ZrMe(OEt2)][B(CF3)4]
δ(1H) ) -0.78 (µ-CH3; 3 H), 0.23 (CH3; 6 H), 6.30 (C5H5; 20 H);
δ(11B) ) -18.9; δ(19F) ) -61.6; 2J(11B,19F) ) 25.9
δ(1H) ) 0.84 (CH3; 3 H), 1.24 (CH2CH3; 12 H), 3.68 (CH2; 8 H), 6.46 (C5H5; 10 H);
δ(11B) ) -18.9; δ(19F) ) -61.6; 3J(C1H2,C1H3) ) 7.0; 2J(11B,19F) ) 25.9
δ(1H) ) 0.64 (CH3; 3 H), 6.46 (C5H5; 10 H); δ(11B) ) -21.9; δ(19F) ) -61.0
δ(1H) ) 6.36 (C5H5; 10 H); δ(11B) ) -21.9; δ(19F) ) -60.9
δ(1H) ) 0.09 (CH3; 3 H), 6.04 (C5H5; 10 H); δ(11B) ) -37.3
δ(1H) ) 0.08 (CH3; 3 H), 6.09 (C5H5; 10 H); δ(11B) ) -38.5
Cp2ZrMe{NCB(CF3)3}
Cp2Zr{NCB(CF3)3}2
Cp2ZrMe{NCB(CN)3}
Cp2ZrMe{NCB(CN)3}‚CD3CN/
[Cp2ZrMe(NCCD3)]+‚CD3CNc
Cp2Zr{NCB(CN)3}2‚CD3CN/
[Cp2Zr{NCB(CN)3}(NCCD3)]+‚CD3CN/
[Cp2Zr(NCCD3)2]2+‚CD3CNc
δ(1H) ) 6.55 (C5H5; 10 H); δ(11B) ) -38.5
a δ in ppm, J in Hz. b NMR solvent: CD2Cl2. c NMR solvent: CD3CN.
Table 3. Polymerization of Propene with
rac-Et(1-Ind)2ZrMe2 and [Ph3C][B(CF3)4],
[Ph3C][B(CN)4], or [H(OEt2)2][B(CF3)4]
The reaction of [Ph3C][B(CF3)4] with Cp2ZrMe2 was
also investigated in d8-toluene. At 0 °C the main
reaction product was the [Cp2ZrMe]+ cation. Probably
due to low solubility of the [Cp2ZrMe][B(CF3)4] salt or
a similar species, a brownish precipitate was formed.
T
t
productivity
mmmm
] [%]
cocatalyst
MAO
(C6F5)3B
[°C] [min] [kg mol(Zr)-1 h-1
20
iBu3Al 20
iBu3Al 26
iBu3Al 20
iBu3Al 20
iBu3Al 50
iBu3Al 20
20
20
3
12 000
360
92
It easily dissolved in acetonitrile, and in the NMR
spectra no evidence was found for a decomposition of
86
[Ph3C][B(C6F5)4]
[Ph3C][B(CF3)4]
[Ph3C][B(CF3)4]
[Ph3C][B(CF3)4]
[Ph3C][B(CN)4]
153 000
5
91
1
the [B(CF3)4]- anion. An assignment of the H NMR
20
120
20
20
20
n.o.a
84
0.5
signals in the region typical for Cp protons was not
possible. Probably zirconocene complexes with one or
more CD3CN ligands are present.29,30
[H(OEt2)2][B(CF3)4] iBu3Al 20
1
n.o.
Through protonation of Cp2ZrMe2 with [H(OEt2)2]-
[B(CF3)4], methane is released from the reaction mixture
and the vacant coordination site at Zr is saturated by
one diethyl ether molecule (eq 6).
a n.o. ) not observed.
neutral complexes are collected in Table 2. The 11B and
19F NMR signals of the [(CF3)3BCN]- ligand are broad-
ened when coordinated to an electrophilic center. As
found for the reactions described above, a solid precipi-
tated from solution, and this process also was enhanced
with increasing temperature. The precipitate can nei-
ther in CD3CN nor in D2O completely be dissolved;
hence the composition remained unclear. In the NMR
spectra no evidence was found for the decomposition of
the [(CF3)3BCN]- anion.
CD2Cl2
Cp2ZrMe2 + [H(OEt2)2][B(CF3)4] -60 °C, 1 h8
[Cp2ZrMe(OEt2)][B(CF3)4] + Et2O + CH4 (6)
The proton NMR signals of the [Cp2ZrMe(OEt2)]+
cation are collected in Table 2 and are assigned by using
the relative intensities of the signals and by comparing
with data described in the literature.16 During the
reaction a solid was formed that was sparingly soluble
in CD3CN. In the 11B and 19F NMR spectra traces of
novel unidentified trifluoromethylborate anions were
found that indicate a partial decomposition of the
[B(CF3)4]- anion.
In contrast to the reaction of [Ph3C][B(CF3)4] with Cp2-
ZrMe2, in the related reaction of [Ph3C][(CF3)3BCN]
with Cp2ZrMe2 a bridged dimeric intermediate was not
observed and instead only Cp2ZrMe{NCB(CF3)3} was
formed according to eq 7.
The reaction between [Ph3C][B(CN)4] and Cp2ZrMe2
resulted even at -60 °C in the relatively fast precipita-
tion of Cp2ZrMe{NCB(CN)3} as main product (eq 8).
CD2Cl2
Cp2ZrMe2 + [Ph3C][B(CN)4] -60 °C, 30 min8
Cp2ZrMe{NCB(CN)3} + Ph3CMe (8)
The colorless insoluble reaction product is completely
soluble in acetonitrile. The NMR spectroscopic data are
summarized in Table 2, and the NMR spectra are
presented in Figure S4. The 1H NMR chemical shifts of
the cyclopentadienyl protons in CD3CN solution are
similar to those reported for [Cp2ZrMe(NCMe)][BPh4]
and [Cp2Zr(NCMe)2][BPh4]2,29 which indicates a fast
ligand exchange between CD3CN and the [B(CN)4]-
anion.
CD2Cl2
Cp2ZrMe2 + [Ph3C][(CF3)3BCN] -60 °C, 30 min8
Cp2ZrMe{NCB(CF3)3} + Ph3CMe (7)
Since a small excess of the trityl reagent was em-
ployed, the formation of a second zirconocene complex
was possible: Cp2Zr{NCB(CF3)3}2. Similar coordination
compounds of the Cp2Zr2+ fragment have been described
with acetonitrile as ligand.29,30 The NMR data of the
Polymerization of Propene. In Table 3 the results
of the polymerization reactions of rac-Et(1-Ind)2ZrMe2
and [H(OEt2)2][B(CF3)4], [Ph3C][B(CF3)4], or [Ph3C]-
i
[B(CN)4] as cocatalysts in the presence of Bu3Al are
summarized. For comparison the respective data of
the polymerizations with MAO, (C6F5)3B, and [Ph3C]-
[B(C6F5)4] are listed. The very low to zero productivities
with the cocatalysts containing the [B(CF3)4]- anion can
be attributed to their obvious low solubility even in d8-
toluene and CD2Cl2 as outlined in the NMR experi-
(27) Edelbach, B. L.; Rahman, A. K. F.; Lachicotte, R. J.; Jones, W.
D. Organometallics 1999, 18, 3170.
(28) Watson, L. A.; Yandulov, D. V.; Caulton, K. G. J. Am. Chem.
Soc. 2001, 123, 603.
(29) Jordan, R. F.; Echols, S. F. Inorg. Chem. 1987, 26, 383.
(30) Bahr, S. R.; Boudjouk, P. J. Org. Chem. 1992, 57, 5545.

Salts of Borate Anions
Organometallics, Vol. 24, No. 21, 2005 5107
cm-1. Solid samples were crushed between AgBr disks. Raman
spectra of the solids were recorded at room temperature with
a resolution of 2 cm-1 on a RFS 100/S FT Raman spectrometer
(Bruker, Karlsruhe, Germany) using the 1064 nm excitation
(<500 mW) of a Nd:YAG laser.
DSC Measurements. Thermo-analytical measurements
were made with a Netzsch DSC204 instrument. Temperature
and sensitivity calibrations in the temperature range 20-500
°C were carried out with naphthalene, benzoic acid, KNO3,
AgNO3, LiNO3, and CsCl. About 5-10 mg of the solid samples
was weighed and contained in sealed aluminum crucibles.
They were studied in the temperature range 20-600 °C with
a heating rate of 5 K min-1; throughout this process the
furnace was flushed with dry nitrogen. For the evaluation of
the output, Netzsch Protens4.0 software was employed.
ments. Another reason that cannot be fully excluded is
the instability of [B(CF3)4]- under the reaction condi-
tions due to F- abstraction as found previously under
more severe conditions, e.g., in the presence of silyl
cations.23 Especially the polymerization reaction at 50
°C, where no polymer was obtained, supports this
hypothesis.
In the case of the activation of the metallocene with
[Ph3C][B(CN)4] the coordination site at the cationic
metallocene complex is occupied by [B(CN)4]-, and so
no reaction with propene can occur.
Summary and Conclusion
Simple reaction routes to salts with the borate anions
[B(CF3)4]-, [(CF3)3BCN]-, and [B(CN)4]- are described.
The oxonium salt [H(OEt2)2][B(CF3)4] exhibits an un-
expected high thermal stability. The three trityl salts
are all ionic in nature, whereas the isocyanoborate anion
[(CF3)3BNC]- forms the molecular complex Ph3CCNB-
(CF3)3.
Methyl group abstraction from Cp2ZrMe2 using
[H(OEt2)2][B(CF3)4] or [Ph3C]X (X ) [B(CF3)4]-, [(CF3)3-
BCN]-, [B(CN)4]-) generates metallocene cations, with
[B(CF3)4]-, while [(CF3)3BCN]- and [B(CN)4]- coordi-
nate to the metal center. The zirconocene salts with
[B(CF3)4]- counteranions are not soluble in common
weakly coordinating solvents, e.g., toluene. Hence, they
are not suitable for homogeneous Ziegler-Natta cataly-
sis.
[H(OEt2)2][B(CF3)4]. A 250 mL round-bottom flask equipped
with a valve with a PTFE stem (Young, London), fitted with
a PTFE-coated magnetic stirring bar, was charged with
K[B(CF3)4] (546 mg, 1.68 mmol) and dried in vacuo. Diethyl
ether (80 mL) was vacuum transferred into the flask. The
reaction mixture was warmed to -50 °C. Into a second 290
mL round-bottom flask equipped with a valve with a PTFE
stem (Young, London) HCl (12 mmol) was added. Both flasks
were connected, and the HCl gas was allowed to diffuse into
the diethyl ether solution. A colorless solid precipitated. The
mixture was warmed to -20 °C for 5 h. All volatiles were
removed under reduced pressure, and the colorless residue was
extracted two times with CH2Cl2 (20 mL, 10 mL). The
suspension was filtered through a glass frit with Celite, and
the colorless solutions were collected in a 100 mL two-neck
round-bottom flask with a standard cone taper and a valve
with a PTFE stem (Young, London). After removal of the
solvent in vacuo [H(OEt2)2][B(CF3)4] was obtained as a colorless
solid. Yield: 530 mg (1.22 mmol, 73%). 1H NMR (CD2Cl2,
Experimental Section
3
3
RT): δ 16.3 (s, 1H), 4.11 (q, JHH ) 7.2 Hz, 8H), 1.44 (t, JHH
1
) 7.2 Hz, 12H). 13C{19F} NMR (CD2Cl2, RT): δ 132.6 (q, JBC
General Considerations. Apparatus. Volatile materials
were manipulated in a glass vacuum apparatus equipped with
a capacitance pressure gauge (type 280 E Setra Instruments)
and fitted with PTFE stem valves (Young, London) and NS
14.5 standard tapers. Air- and moisture-sensitive compounds
were handled under an Ar atmosphere in a glovebox (MBraun,
Germany). Reactions involving air-sensitive compounds were
performed under nitrogen using standard Schlenk techniques.
Solvents were dried and distilled under N2 and stored over
3 or 4 Å molecular sieves in flasks, equipped with valves with
a PTFE stem (Young, London). Ph3CCl, Ph3CBr, and MeLi
were obtained from Aldrich and Cp2ZrMe2 from Strem Chemi-
cals and used as received. K[B(CF3)4],1 K[(CF3)3BCN],8
K[B(CN)4],2,4 and rac-(Ind)2EtZrCl231 were synthesized accord-
ing to literature procedures.
) 73.4 Hz, 4C, CF3), 71.1 (tqt, 1JHC ) 150.0 Hz, 2JHC ) 4.3 Hz,
3JHC ) 2.7 Hz, 4C, CH2), 13.9 (qt, 1JHC ) 128.4 Hz, 2JHC ) 2.7
2
Hz, 4C, CH3). 11B NMR (CD2Cl2, RT): δ -18.9 (tridecet, JBF
2
) 25.9 Hz). 19F NMR (CD2Cl2, RT): δ -61.6 (q, JBF ) 25.9
Hz). Anal. Calcd for H21C12BF12O2 (436.09): C, 33.05; H, 4.85.
Found: C, 32.23; H, 4.84.
[Ph3C][B(CF3)4]. K[B(CF3)4] (500 mg, 1.53 mmol) and trityl
chloride (430 mg, 1.61 mmol) were placed into a 250 mL round-
bottom flask equipped with a valve with a PTFE stem (Young,
London) and fitted with a PTFE-coated magnetic stirring bar.
The solids were carefully dried under reduced pressure. Under
a nitrogen atmosphere dichloromethane (100 mL) was added
via a PFA cannula. Immediately after addition of the solvent
the solution above the suspension turned yellow. The reaction
mixture was stirred 4 h at room temperature. The resulting
suspension was filtered through a glass frit covered with Celite
under an inert atmosphere into a 200 mL Schlenk flask fitted
with a PTFE-coated magnetic stirring bar. The reaction flask
and the glass frit were washed two times with dichloromethane
(20 and 10 mL). The yellow solution was reduced to a volume
of 10 mL. Upon addition of hexane (70 mL) a yellow precipitate
formed. The yellow solid was separated by filtration through
a glass frit, washed with 10 mL of hexane, and dried in a
1
NMR Spectroscopy. H, 19F, and 11B NMR spectra were
recorded at different temperatures on a Bruker Avance DRX-
300 spectrometer operating at 300.13, 282.41, or 96.92 MHz
for 1H, 19F, and 11B nuclei, respectively. 13C NMR spectroscopic
studies were performed at room temperature on a Bruker
Avance DRX-500 spectrometer, operating at 125.758 MHz. The
NMR signals were referenced against TMS and CFCl3 as
internal standards and BF3‚OEt2 as external standard. Samples
of moisture-sensitive compounds were prepared in 5 mm o.d.
NMR tubes, equipped with special valves with PTFE stems
(Young, London).32
Vibrational Spectroscopy. IR spectra were recorded at
room temperature in the range 4000-400 cm-1 on an IFS 66v
FTIR instrument (Bruker, Karlsruhe, Germany). A DTGS
detector, together with a KBr/Ge beam splitter, was used in
the region of 4000-400 cm-1. In this region 128 scans were
co-added for each spectrum using an apodized resolution of 2
1
vacuum. Yield: 705 mg (1.33 mmol, 87%). H NMR (CD2Cl2,
RT): δ 8.31 (m, 1H, p-H), 7.93 (m, 2H, m-H), 7.73 (m, 2H, o-H).
13C{19F} NMR (CD2Cl2, RT): δ 211.5 (s, 1C, C+), 144.1 (dtt,
1JHC ) 167.9 Hz, 2JHC ) 1.6 Hz, 3JHC ) 7.9 Hz, 3C, p-C), 143.3
(ddd, 1JHC ) 167.9 Hz, 3JHC ) 7.5 Hz, 3JHC ) 7.6 Hz, 6C, o-C),
140.5 (tt, 2JHC ) 0.9 Hz, 3JHC ) 7.9 Hz, 3C, i-C), 132.6 (q, 1JBC
1
3
) 73.4 Hz, 4C, CF3), 131.2 (dd, JHC ) 167.6 Hz, JHC ) 7.8
Hz, 6C, m-C). 11B NMR (CD2Cl2, RT): δ -18.9 (tridecet, JBF
2
) 25.9 Hz). 19F NMR (CD2Cl2, RT): δ -61.6 (q, JBF ) 25.9
2
(31) Diamond, G. M.; Rodewald, S.; Jordan, R. F. Organometallics
1995, 14, 5.
(32) Gombler, W.; Willner, H. Int. Lab. 1984, 84.
Hz). Anal. Calcd for H15C23BF12 (530.16): C, 52.11; H, 2.85.
Found: C, 52.06; H, 2.80.

5108 Organometallics, Vol. 24, No. 21, 2005
Finze et al.
[Ph3C][(CF3)3BCN]. The compound was prepared accord-
ing to the procedure as described for [Ph3C][B(CF3)4]. Sub-
strates: K[(CF3)3BCN] (312 mg, 1.10 mmol) and trityl chloride
(323 mg, 1.16 mmol). Yield: 445 mg (0.91 mmol, 83%). 1H NMR
(CD2Cl2, RT): δ 8.31 (m, 1H, o-H), 7.93 (m, 2H, m-H), 7.73
(m, 2H, p-H). 13C{19F} NMR (CD2Cl2, RT): δ 211.5 (s, 1C, C+),
144.1 (dtt, 1JHC ) 167.9 Hz, 2JHC ) 1.6 Hz, 3JHC ) 7.9 Hz, 3C,
residue was dissolved in dry CD3CN. Neither in the 11B nor
in the 19F NMR spectrum were decomposition products of
[B(CF3)4]- identified. In the 1H NMR spectrum signals in the
typical range for cyclopentadienyl protons were located, but
no assignment was possible.
Reaction of Cp2ZrMe2 with [H(OEt2)2][B(CF3)4].
[H(OEt2)2][B(CF3)4] (86 mg, 0.20 mmol); Cp2ZrMe2 (47 mg, 0.19
mmol). At -60 °C gas evolution and formation of a beige solid
was observed. By 1H NMR spectroscopy [Cp2ZrMe(OEt2)]+,
diethyl ether, CH4, and excess [H(OEt2)2]+ were identified. The
ratio of Et2O versus [Cp2ZrMe(OEt2)]+ was 5:1. With increasing
temperature and reaction time more solid precipitated and the
color changed from orange to brown. After 12 h at room
temperature all volatile components were removed in vacuo
and dry CD3CN was condensed into the NMR tube. The
resulting brown solution contained a colorless solid and was
analyzed by NMR spectroscopy. In the 1H NMR spectra three
signals were attributed to Cp protons, but an assignment was
impossible. A few other signals of weaker intensity than those
of the [B(CF3)4]- anion were present in the 11B and 19F NMR
spectra.
1
3
3
p-C), 143.3 (ddd, JHC ) 167.9 Hz, JHC ) 7.5 Hz, JHC ) 7.6
Hz, 6C, o-C), 140.5 (tt, 2JHC ) 0.9 Hz, 3JHC ) 7.9 Hz, 3C, i-C),
132.4 (q, 1JBC ) 76.2 Hz, 3C, CF3), 131.2 (dd, 1JHC ) 167.6 Hz,
1
3JHC ) 7.8 Hz, 6C, m-C), 127.5 (q, JBC ) 64.0 Hz, 1C, CN).
2
11B NMR (CD2Cl2, RT): δ -22.3 (decet, JBF ) 29.0 Hz). 19F
2
NMR (CD2Cl2, RT): δ -62.1 (q, JBF ) 29.0 Hz). Anal. Calcd
for H15C23BF9N (487.17): C, 56.71; H, 3.10; N, 2.88. Found:
C, 55.85; H, 3.15; N, 2.98.
[Ph3C][B(CN)4]. The preparation was performed similar
to the syntheses of [Ph3C][B(CF3)4] and [Ph3C][(CF3)3BCN].
The only difference was the use of acetonitrile as solvent
instead of dichloromethane. CH3CN was removed after the
reaction (4 h), and the residue was suspended in CH2Cl2 and
filtered. Substrates: Ag[B(CN)4] (500 mg, 2.25 mmol) and trityl
bromide (726 mg, 2.25 mmol). Yield: 408 mg (1.14 mmol, 51%).
1H NMR (CD2Cl2, RT): δ 8.31 (m, 1H, p-H), 7.94 (m, 2H, m-H),
7.73 (m, 2H, o-H). 13C{1H} NMR (CD2Cl2, RT): δ 211.2 (s, 1C,
C+), 143.8 (s, 3C, p-C), 143.0 (s, 6C, o-C), 140.2 (s, 3C, i-C),
131.0 (s, 6C, m-C), 122.7 (q, 1JBC ) 71.5 Hz, 4C, CN). 11B NMR
Reaction of Cp2ZrMe2 with [Ph3C][(CF3)3BCN].
[Ph3C][(CF3)3BCN] (53 mg, 0.11 mmol); Cp2ZrMe2 (25 mg, 0.10
mmol). At -60 °C a red-brown, clear solution was obtained.
According to the NMR spectra Cp2ZrMe{NCB(CF3)3} was the
main product and probably Cp2Zr{NCB(CF3)3}2 was formed
as a side product due to the excess of [Ph3C][(CF3)3BCN]. At
-30 °C the reaction mixture slowly turned cloudy. At room
temperature the rate of precipitation increased. The mixture
was kept at room temperature for 1 day before all volatiles
were removed under reduced pressure. The residue was not
completely soluble in CD3CN. The 11B and 19F NMR spectra
showed only the signals of the [(CF3)3BCN]- anion. The signals
(CD2Cl2, RT):
δ -38.6 (s). Anal. Calcd for H15C23BN4
(358.21): C, 77.12; H, 4.22; N, 15.64. Found: C, 77.19; H, 4.21;
N, 15.50.
(CF3)3BNCCPh3. K[(CF3)3BNC] (32 mg, 0.11 mmol) and
Ph3CBr (40 mg, 0.12 mmol) were transferred into a 5 mm o.d.
NMR tube, equipped with a valve with a PTFE stem (Young,
London) and connected with a glass vacuum apparatus. The
mixture was dried in a vacuum, and then CD2Cl2 (1.5 mL) was
condensed into the NMR tube at -196 °C. The NMR tube was
warmed to room temperature and shaken for 3 h. The solution
and the precipitate are colorless. 1H NMR (CD2Cl2, RT): δ 7.4
(m, 3H), 7.2 (m, 2H). 13C{1H} NMR (CD2Cl2, RT): 136.0 (s,
3C), 130.7 (s, 6C), 130.4 (s, 6C), ∼130 (s, 3C, CF3), 129.0 (s,
3C), 123.1 (s, 1C, CN), δ 60.1 (s, 1C, CCN). 11B NMR (CD2Cl2,
RT): δ -14.4 (s, br). 19F NMR (CD2Cl2, RT): δ -66.4 (s, br).
Reactions of Cp2ZrMe2 with Cocatalysts Monitored by
NMR Spectroscopy. General Procedure. In a glovebox a
5 mm o.d. NMR tube, equipped with a valve with a PTFE stem
(Young, London),32 was charged with Cp2ZrMe2 and cocatalyst.
The NMR tube was connected to a glass vacuum apparatus,
and 1 mL of CD2Cl2 was added in vacuo. The NMR tube was
placed into an ethanol bath at -60 °C, and after 10 min it
was transferred into the probe head of a NMR spectrometer
(Bruker Avance 300). The first NMR spectra were recorded
30 min after starting the reaction.
1
in the H NMR spectrum could not be assigned. Attempts to
dissolve the residue in water failed.
Reaction of Cp2ZrMe2 with [Ph3C][B(CN)4]. [Ph3C]-
[B(CN)4] (39 mg, 0.11 mmol); Cp2ZrMe2 (18 mg, 0.07 mmol).
Immediately after warming to -60 °C a white solid precipi-
tated. While at the beginning of the reaction the presence of
Cp2ZrMe{NCB(CN)3} could be established by NMR spectros-
copy, after 15 h at room temperature no boron-, fluorine-, or
cyclopentadienyl-containing species were found in solution.
The liquid phase and the precipitate were colorless. The
solvent was removed in vacuo, and the residue was dissolved
in CD3CN and analyzed by NMR spectroscopy.
X-ray Crystallographic Study of [Ph3C][B(CN)4]. Crys-
tals suitable for an X-ray diffraction study were obtained from
a saturated solution of [Ph3C][B(CN)4] in CD3CN. The crystals
were placed on a copper trough,33 cooled to -70 °C in a steam
of nitrogen. During the preparation the trough was flushed
with dry nitrogen. Suitable crystals were selected under a
polarizing microscope and fitted into glass capillaries (o.d. 0.1
to 0.3 mm). The capillaries were sealed off at both ends to give
glass cylinders of approximately 20 mm length. The glass
cylinders, containing the crystals, were attached with wax to
the goniometer head. Diffraction data were collected at 173 K
on a Nonius diffractometer with a CCD camera using Mo KR
radiation (λ ) 0.71069 Å) and a graphite monochromator. At
the end of the data collection, the first intensity measurement
was repeated, which demonstrated the stability of the crystal
during the X-ray diffraction analysis. The intensity data were
subsequently corrected with the SCALEPACK program.34 The
structure was solved in R3h (No. 148) by direct methods with
SHELXS-9735,36 and refined with anisotropic temperature
Reaction of Cp2ZrMe2 with [Ph3C][B(CF3)4] in CD2Cl2.
[Ph3C][B(CF3)4] (40 mg, 0.08 mmol); Cp2ZrMe2 (19 mg, 0.08
mmol). At -60 °C an orange solution was obtained, and slowly
a colorless precipitate formed. After 30 min a mixture of [(Cp2-
ZrMe)2-µ-Me][B(CF3)4], [Ph3C][B(CF3)4], and Ph3CMe was
observed. The reaction mixture was warmed to -25 °C, and
after 1.5 h as sole reaction products [Cp2ZrMe][B(CF3)4] and
Ph3CMe were found. When the reaction mixture was warmed
to 0 °C and then to room temperature, other unidentified
signals were observed and the precipitation is more rapid.
After 15 h only weak, broad signals due to cyclopentadienyl
1
protons were observed in the H NMR spectrum.
Reaction of Cp2ZrMe2 with [Ph3C][B(CF3)4] in d8-
Toluene. [Ph3C][B(CF3)4] (39 mg, 0.07 mmol); Cp2ZrMe2 (18
mg, 0.07 mmol). The reaction was started at 0 °C, and a brown
(33) Veith, M.; Ba¨ringhausen, H. Acta Crystallogr., Sect. B: Struct.
Sci. 1974, 30, 1806.
(34) Otwinowski, Z.; Minor, W. Methods Enzymol. 1997, 276, 307.
(35) Sheldrick, G. M. SHELXS-97, Program for Crystal Structure
Solution; University of Go¨ttingen: Germany, 1997.
(36) Sheldrick, G. M. SHELXL-97, Program for Crystal Structure
Refinement; University of Go¨ttingen: Germany, 1997.
1
precipitate began to form. In the H NMR spectrum only the
signals of [Cp2ZrMe]+ and Ph3CMe were observed. After
keeping the mixture for 3 h at room temperature no signals
were found in the region of the Cp protons anymore. All
volatiles were removed at reduced pressure, and the brownish

Salts of Borate Anions
Organometallics, Vol. 24, No. 21, 2005 5109
factors.37 A summary of experimental details and crystal data
is presented in Table 1.
Gaseous Propylene Polymerization at 50 °C (Borate
Activation). In a 300 mL stainless steel Parr reactor, 50 mg
of TIBA in 95 mL of toluene was equilibrated for 1 h at 50 °C
with 75 psig propylene gas. Metallocene and borate (stoichio-
metric) in toluene (total volume 5 mL) were injected, respec-
tively, into the reactor by propylene pressure, and the polym-
erization was run for 1 h, after which time methanol (10 mL)
was injected to quench the reaction.
Polymer Characterization. Polypropylene pentad distri-
butions were determined by 13C NMR measurements using a
Varian Unity Innova 300 MHz instrument. Spectra were
acquired with samples (80 mg in 2 mL of o-dichlorobenzene/
10% vol d6-benzene with Cr(acac)3 as a relaxation agent) at
100 °C in 10 mm NMR tubes.
Polymerizations. General Considerations for Propy-
lene Polymerization. Methylaluminoxane (MAO) was ob-
tained from Albemarle and dried under vacuum. Triisobuty-
laluminum (TIBA) was purchased from Aldrich and was used
as received. Toluene was passed through two purification
columns packed with activated alumina and copper catalyst
and collected under nitrogen. Propylene gas was purchased
from Matheson, and liquid propylene was purchased from Scott
Specialty Gases. Both were passed through two purification
columns packed with activated alumina and copper catalyst.
Polymerization Procedure for MAO Activation. In a
300 mL stainless steel Parr reactor, 150 mg of MAO in 8 mL
of toluene was equilibrated for 30 min at 20 °C with 90 mL of
liquid propylene. Metallocene in toluene (2 mL) was injected
into the reactor by argon pressure, and the polymerization was
run for 20 min, after which time methanol (10 mL) was
injected to quench the reaction. The polypropylene was
precipitated from acidified methanol, filtered, washed with
methanol, and dried under vacuum at 40 °C.
Details of the crystal structure determination can be
obtained from the Cambridge Crystallographic Data Centre,
12 Union Road, Cambridge CB21EZ, UK (fax: +44-1223-336-
033; e-mail: deposit@ccdc.cam.ac.uk) on quoting the depository
number CCDC-273901.
Acknowledgment. Financial support by the Deut-
sche Forschungsgemeinschaft-DFG and Merck KGaA
(Darmstadt, Germany) is acknowledged. R.M.W. ac-
knowledges support from the NSF (NSF-CHE 0305436).
We are grateful to Professor Minkwitz, University of
Dortmund, for allowing the use of the CCD diffracto-
meter.
Liquid Propylene Polymerization (Borate or Borane
Activation). In a 300 mL stainless steel Parr reactor, 50 mg
of TIBA in 8 mL of toluene was equilibrated for 30 min at 20
°C with 90 mL of liquid propylene. Metallocene and borate/
borane (stoichiometric) in toluene (total volume 2 mL) were
injected, respectively, into the reactor by argon pressure, and
the polymerization was run for 20 min, after which time
methanol (10 mL) was injected to quench the reaction. Poly-
propylene was precipitated from acidified methanol, filtered,
washed with methanol, and dried under vacuum at 40 °C.
Supporting Information Available: Tables of IR data
of [Ph3C][B(CN)4] and [Ph3C][B(CF3)4], a view of the unit cell,
IR spectra of [Ph3C][B(CN)4] and [Ph3C][B(CF3)4], and the 1H
NMR spectra of the reaction of Cp2ZrMe2 with [Ph3C][B(CN)4].
This material is available free of charge via the Internet at
http://pubs.acs.org.
(37) Sheldrick, G. M. Universita¨t Go¨ttingen, 1997.
OM050463J