Aminoalkyl-substituted indenyl-nickel compounds: Tuning reactivities as a function of the pendant, hemilabile moiety

Article abstract of DOI:10.1021/om030241q

Indenyl ligands bearing three different aminoalkyl substituents have been used to prepare the complexes (IndNR₂)Ni(PPh₃)Cl (IndNR₂ = 2-(1-indenylmethyl)pyridine (1), N-(1-indenylethyl)pyrrolidine (2), and N-(1-indenylethyl)diisopropylamine (3)). The solution NMR spectra of complexes 1 and 2 point to the existence of a dynamic process involving the reversible coordination of the pendant amine moieties to the Ni center, but no N-Ni interaction is evident in complex 3. Abstraction of Cl^- from the neutral precursors 1-3 yields the corresponding cationic derivatives [(η³:η¹-IndNR₂)Ni(PPh₃)] ⁺ (4-6) wherein the amino tether is chelated to the nickel center. Complexes 1-5 have been isolated and fully characterized by multinuclear NMR spectroscopy and, in the case of 1 and 4, by single-crystal X-ray diffraction studies. The isolation of complex 6 is complicated by its partial conversion to the bis(phosphine) derivative [{η³:η⁰-IndCH₂CH₂N(i-Pr) ₂}Ni(PPh₃)₂]⁺ (7). Studies on the displacement of the chelating amine moiety in 4 and 5 by dppe, PPh₃, and pyridine showed the pyridine moiety to be the least labile. Cyclic voltammetry studies have shown that the reduction potentials of the complexes vary as a function of the Ni-N interaction, the complexes bearing the NMe₂ moieties showing the strongest resistance to reduction. Olefin polymerization reactions also showed that the nature of the N-moiety has a considerable influence on the catalytic reactivity of the cationic complexes.

Full text of DOI:10.1021/om030241q

3124
Organometallics 2003, 22, 3124-3133
Am in oa lk yl-Su bstitu ted In d en yl-Nick el Com p ou n d s:
Tu n in g Rea ctivities a s a F u n ction of th e P en d a n t,
Hem ila bile Moiety
Laurent F. Groux and Davit Zargarian*
De´partement de Chimie, Universite´ de Montre´al, Montre´al, Que´bec, Canada H3C 3J 7
Received April 2, 2003
Indenyl ligands bearing three different aminoalkyl substituents have been used to prepare
the complexes (Ind∧NR2)Ni(PPh3)Cl (Ind∧NR2 ) 2-(1-indenylmethyl)pyridine (1), N-(1-
indenylethyl)pyrrolidine (2), and N-(1-indenylethyl)diisopropylamine (3)). The solution NMR
spectra of complexes 1 and 2 point to the existence of a dynamic process involving the
reversible coordination of the pendant amine moieties to the Ni center, but no N-Ni
interaction is evident in complex 3. Abstraction of Cl- from the neutral precursors 1-3 yields
the corresponding cationic derivatives [(η3:η1-Ind∧NR2)Ni(PPh3)]+ (4-6) wherein the amino
tether is chelated to the nickel center. Complexes 1-5 have been isolated and fully
characterized by multinuclear NMR spectroscopy and, in the case of 1 and 4, by single-
crystal X-ray diffraction studies. The isolation of complex 6 is complicated by its partial
conversion to the bis(phosphine) derivative [{η3:η0-IndCH2CH2N(i-Pr)2}Ni(PPh3)2]+ (7).
Studies on the displacement of the chelating amine moiety in 4 and 5 by dppe, PPh3, and
pyridine showed the pyridine moiety to be the least labile. Cyclic voltammetry studies have
shown that the reduction potentials of the complexes vary as a function of the Ni-N
interaction, the complexes bearing the NMe2 moieties showing the strongest resistance to
reduction. Olefin polymerization reactions also showed that the nature of the N-moiety has
a considerable influence on the catalytic reactivity of the cationic complexes.
In tr od u ction
The above considerations and our long-standing in-
terest in the chemistry of nickel indenyl complexes led
us to study the reactivities of Ni complexes bearing the
ligands Ind∧NR2. In earlier reports, we have described
the structures and reactivities of the neutral complexes
(Ind(CH2)nNRR′)NiL(X) (n ) 2-4; NRR′ ) NH(t-Bu),
NH(PhCH2), NH2, NMe2; L ) PPh3, PCy3, PMe3; X )
Cl, I, Me, Bu)3 and the cationic complex [(η3:η1-Ind(CH2)2-
NMe2)Ni(PPh3)]+.4 These studies showed that using the
ligand Ind(CH2)2NMe2 offers an important advantage
over the nonfunctionalized Ind ligands; namely, the
presence of a hemilabile NfNi coordination in com-
plexes incorporating this ligand prevents the formation
of the catalytically inert bis(phosphine) derivatives
[IndNi(PR3)2]+, thereby improving the catalytic activi-
ties of the cationic complexes. Indeed, even when the
amine moiety is not chelated, its proximity to the Ni
center seems to have a marked influence over the course
of the catalytic reactions and the nature of their
products. These findings prompted us to prepare new
complexes featuring Ind∧NR2 ligands with different
coordinating properties in order to investigate further
the role played by the amine moiety on the stability and
reactivities of these complexes.
The cyclopentadienyl ligand (Cp) and its congeners
such as the indenyl (Ind) have played an important role
in the development of organometallic chemistry. One
attractive feature of these ligands is the ease with which
their steric and electronic properties can be modified
by the judicious introduction of diverse substituents.
The versatility of Cp-type ligands can be further en-
hanced when their substituents bear coordinating moi-
eties. For instance, the ligands Cp∧NR2 (∧ denotes the
tether that links the amine moiety to the Cp ring) are
known to impart many interesting properties to their
complexes, including superior catalytic reactivities,
stabilization of otherwise unstable species, changing
solubility properties, introducing chirality, and so on.1
Although a wide variety of complexes bearing Cp∧NR2
ligands are known for most transition metals, relatively
few derivatives of group 10 metals have been reported2
and little is known of their reactivities.
(1) For reviews of this topic see: (a) Mu¨ller, C.; Vos, D.; J utzi, P. J .
Organomet. Chem. 2000 600, 127. (b) J utzi, P.; Redeker, T. Eur. J .
Inorg. Chem. 1998, 663. (c) J utzi, P.; Siemeling, U. J . Organomet.
Chem. 1995, 500, 175. (d) J utzi, P.; Dahlaus, J . Coord. Chem. Rev.
1994, 137, 179.
(2) (a) Oberbeckmann, N.; Merz, K.; Fischer, R. A. Organometallics
2001, 20, 3265. (b) Segnitz, O.; Winter, M.; Merz, K.; Fischer, R. A.
Eur. J . Inorg. Chem. 2000, 2077. (c) Hoffmann, H.; Fischer, R. A.;
Antelmann, B.; Huttner, G. J . Organomet. Chem. 1999, 584, 131. (d)
Weiss, J .; Frank, A.; Herdweck, E.; Nlate, S.; Mattner, M.; Fischer, R.
A. Chem. Ber. 1996, 129, 297. (e) Fischer, R. A.; Nlate, S.; Hoffmann,
H.; Herdweck, E.; Blumel, J . Organometallics 1996, 15, 5746. (f) Nlate,
S.; Herdweck, E.; Fischer, R. A. Angew. Chem., Int. Ed. Engl. 1996,
35, 1861. (g) J utzi, P.; Redeker, T.; Neumann, B.; Stammler, H.-G. J .
Organomet. Chem. 1995, 498, 127.
The present article describes the preparation and
characterization of a new series of neutral and cationic
nickel complexes bearing the ligands 2-(1-indenylmeth-
(3) Groux, L. F.; Be´langer-Garie´py, F.; Zargarian, D.; Vollmerhaus,
R. Organometallics 2000, 19, 1507.
(4) (a) Groux, L. F.; Zargarian, D. Organometallics 2001, 20, 3811.
(b) Groux, L. F.; Zargarian, D.; Simon, L. C.; Soares, J . B. P. J . Mol.
Catal. A Chem. 2003, 193, 51.
10.1021/om030241q CCC: $25.00 © 2003 American Chemical Society
Publication on Web 06/21/2003

Aminoalkyl-Substituted Indenyl-Ni Compounds
Organometallics, Vol. 22, No. 15, 2003 3125
Ta ble 1. Cr ysta l Da ta , Da ta Collection , a n d
Str u ctu r e Refin em en t of 1 a n d 4
Sch em e 1
1
4
formula
mol wt
C
33H27ClNPNi
C57H47BNPNi‚CH2Cl2
931.37
562.69
cryst color, habit
cryst dimens, mm
symmetry
space group
a, Å
dark red, block
dark red, block
0.25 × 0.23 × 0.14 0.28 × 0.27 × 0.11
triclinic
P1h
monoclinic
P21/c
10.4368(1)
21.0121(2)
21.7137(2)
90
96.340(1)
90
4732.67(8)
4
9.196(3)
12.924(5)
12.943(3)
85.99(3)
73.28(2)
70.72(3)
1390.1(8)
2
b, Å
c, Å
R, deg
â, deg
γ, deg
volume, Å3
Z
D(calcd), g cm-1
diffractometer
1.3443
Nonius CAD-4
1.3072
Bruker AXS
SMART 2K
223(2)
Sch em e 2
temp, K
293(2)
λ (Cu KR), Å
1.54178
2.595
ω/2θ scan
69.91
-11 e h e 11
-15 e k e 15
-15 e l e 15
2892
1.54178
2.247
ω scan
72.96
-12 e h e 11
-25 e k e 25
-26 e l e 26
6288
µ, mm-1
scan type
θ
max, deg
h,k,l range
no. of reflns used
(I > 2σ(I))
abs corr
yl)pyridine, N-(1-indenylethyl)pyrrolidine, and N-(1-
indenylethyl)diisopropylamine. NMR studies were car-
ried out to evaluate the interaction of the tethered
amine moiety with the Ni center in the neutral com-
pounds and study the reaction of nucleophiles with the
cationic compounds. Reactivity studies have also shown
that the cationic complexes can convert styrene into
poly(styrenes); both the polymerization activities of the
precatalysts and the molecular weights of the resulting
polymers depend on the nature of Ni-N interaction.
integration
ABSORB
multiscan
SADABS
T(min, max)
0.4649, 0.7327
0.1816, 0.8306
0.0508, 0.1221
1.041
R[F2>2σ(F2)], wR(F2) 0.0441, 0.0801
GOF
0.979
Ta ble 2. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for 1 a n d 4
1
4
Ni-P
2.1847(13)
2.1784(13)
2.132(3)
2.071(4)
2.037(4)
2.308(4)
2.352(2)
1.400(4)
1.413(5)
1.457(5)
1.416(5)
1.450(4)
1.504(4)
0.25
95.83(11)
97.10(5)
101.16(12)
65.98(14)
161.73(11)
165.54(10)
116.4(4)
109.7(3)
10.1(5)
2.2006(7)
1.949(2)
2.023(2)
2.063(3)
2.095(3)
2.325(2)
2.280(2)
1.421(4)
1.401(4)
1.457(4)
1.417(3)
1.470(3)
1.481(3)
0.24
83.61(9)
106.51(6)
103.19(8)
67.24(10)
150.29(10)
166.58(8)
116.4(2)
109.8(2)
11.48(14)
8.10(13)
Ni-(Cl or N)
Ni-C1
Ni-C2
Resu lts a n d Discu ssion
Ni-C3
Ni-C3A
The amino-functionalized Ind ligands were prepared
according to literature procedures5 by adding the ap-
propriate Cl∧NR2 to an Et2O solution of LiInd, followed
by standard aqueous workup. Subsequent deprotonation
of the resultant Ind∧NR2 and reaction with Ni(PPh3)2-
Cl2 gave the desired products (Scheme 1). In the process
of isolating these complexes, we found that their solu-
bilities varied greatly with the type of pendant amine
moiety: whereas the complex (IndCH2-o-Py)Ni(PPh3)-
Cl (1) readily precipitated from concentrated Et2O
solutions, the analogous complexes bearing the ligands
N-(1-indenylethyl)pyrrolidine (2) and N-(1-indenyleth-
yl)diisopropylamine (3) needed multiple recrystalliza-
tions from less polar solutions.
Solution NMR studies of the neutral complexes 1-3
revealed a dynamic process involving the reversible
coordination of the amine moieties in complexes 1 and
2 to the Ni center (Scheme 2), but no such interaction
was detected in complex 3. As will be described in detail
later, the Ni-N interaction in 1 and 2 is stronger at
higher temperatures, while at lower temperatures the
spectral features of these complexes resemble those of
Ni-C7A
C1-C2
C2-C3
C3-C3A
C3A-C7A
C7A-C1
C1-C8
∆(M-C)§
C1-Ni-(Cl or N)
P- Ni-(Cl or N)
P- Ni-C3
C1-Ni-C3
C3-Ni-(Cl or N)
P-Ni-C1
N-C9-C8
C1-C8-C9
HAa
FAa
8.8(4)
a
∆M-C)) 1/2{(M-C3a + M-C7a) - (M-C1 + M-C3)}; HA )
angle between C1/C2/C3 plane and C1/C3/C3A/C7A plane; FA )
angle between C1/C2/C3 plane and C3A/C4/C5/C6/C7/C7A plane.
analogous complexes that do not bear functionalized
substituents on Ind.
The solid state structure of complex 1 has been
studied by X-ray crystallography. Table 1 lists the
crystal data and the details of data collection and
structure refinement, while Table 2 contains selected
structural parameters. The ORTEP diagram of 1 (Figure
1) shows that the pyridine moiety is oriented away from
(5) (a) Do¨hring, A.; Go¨hre, J .; J olly, P. W.; Kryger, B.; Rust, J .;
Verhovnik, G. P. J . Organometallics 2000, 19, 388. (b) Blais, M. S.;
Chien, J . C. W.; Rausch, M. D. Organometallics 1998, 17, 3775. (c)
Ziniuk, Z.; Goldberg, I.; Moshe, K. J . Organomet. Chem. 1997, 545-
546, 441.

3126 Organometallics, Vol. 22, No. 15, 2003
Groux and Zargarian
F igu r e 1. ORTEP view of complex 1. Thermal ellipsoids
are shown at 30% probability, and hydrogen atoms are
omitted for clarity.
F igu r e 2. ORTEP view of complex 4. Thermal ellipsoids
are shown at 30% probability, and hydrogen atoms and the
counterion (BPh4) are omitted for clarity.
the Ni center and does not coordinate to it; the same
observation was made for the previously studied com-
plex (Ind-CH2CH2NMe2)Ni(PPh3)Cl.3 In this sense, the
solid state structure of these complexes represents their
low-temperature solution behavior. The plane contain-
ing P, Cl, and Ni is perpendicular to the Ind ligand,
which adopts an intermediate hapticity (∆(M-C) ) 0.25
Å);6 hence, the overall geometry around the Ni center
can be described as intermediate between a two-legged
piano stool (assuming η5-Ind) and square planar (as-
suming η3-Ind). As anticipated on the basis of the
relative trans influences of PPh3 and Cl ligands, the Ni-
C3 bond length is significantly shorter (by >20σ) than
the Ni-C1 distance; therefore, the Ind hapticity can be
more accurately described as (η5T η1:η2).7 The Ni-P,
Ni-Cl, and C-C distances in complex 1 are similar to
those found for the analogous complexes bearing non-
functionalized Ind substituents.8
Reacting complex 1 or 2 with excess NaBPh4 in CH2-
Cl2 gave the corresponding cationic complex 4 or 5,
respectively, in ca. 60% yield (Scheme 1). The 31P{1H}
NMR spectra of the products showed new singlet
resonances consistent with the coordination of only one
PPh3 to each Ni center, while the 1H NMR spectra
showed downfield shifts for the H3 signals (to ca. 4.0
ppm). Our previous studies showed that the conversion
of (Ind(CH2)2NMe2)Ni(PPh3)Cl to [η3:η1(Ind(CH2)2NMe2)-
Ni(PPh3)]+ engendered similar changes in the NMR
spectra;3,4a by analogy, we concluded that the amine
moieties in 4 and 5 are chelated to the Ni center. This
assertion was confirmed by the results of X-ray diffrac-
tion studies of complex 4 (vide infra).
spectrum of the reaction mixture, as follows. Complex
6 displayed a singlet resonance at 29.3 ppm, similar to
the corresponding signal for complex 5 (30.3 ppm),
whereas complex 7 gave rise to two AB doublets (36.5
2
and 32.1 ppm, J P-P ) 25 Hz), which are virtually
identical to the corresponding signals for [(1-Me-Ind)-
2
Ni(PPh3)2]+ (35.8 and 32.5 ppm, J P-P ) 25 Hz),9
suggesting that a second PPh3 ligand is coordinated to
the Ni center instead of the N(i-Pr)2 moiety. This
assignment was also corroborated by the fact that when
excess PPh3 was added to the mixture of 3 and NaBPh4,
the main product (>90%) was 7. Complexes 6 and 7
interconvert in solution (Scheme 1), which prevented
us from isolating pure 6 or 7; this behavior is presum-
ably caused by the large steric bulk of the (i-Pr)2N
moiety in 3 that hinders the NfNi coordination.
Suitable single crystals of 4 were obtained from a cold
CH2Cl2/Et2O solution of this complex and subjected to
an X-ray diffraction analysis. Crystal data and details
of data collection and structure refinement are pre-
sented in Table 1, selected structural parameters are
listed in Table 2, and an ORTEP diagram is shown in
Figure 2. The overall geometry in 4 is very similar to
that of complex 1, but chelation of the pyridine moiety
alters some parameters. For instance, the Ni-C1 dis-
tance is reduced by more than 0.1 Å on going from 1 to
4 despite the greater trans influence of PPh3. The
chelation also results in a smaller C1-Ni-N angle in
4 (ca. 84°) compared to the corresponding C1-Ni-Cl
angle in 1 (ca. 96°). The Ind ligand also appears to be
more tightly bound to the cationic center in 4, as
indicated by the generally shorter Ni-C distances. The
Ni-N distance is 0.1 Å shorter than the average Ni-N
distance found in the literature.10 On the other hand,
the Ni-P distance in 4 is longer by about 0.016 Å (ca.
20σ) compared to the neutral 1; this is presumably
because the Ni center becomes a harder Lewis acid upon
ionization, thus being less compatible with the soft
Lewis base PPh3.
In the case of complex 3, abstraction of Cl- gave both
the anticipated N-chelated cation [(η3:η1-IndCH2CH2N(i-
Pr)2Ni(PPh3)]+ (6) and the bis(phosphine) cation [(η3:
η0-IndCH2CH2N(i-Pr)2Ni(PPh3)2]+ (7) (Scheme 1). These
species were identified on the basis of the 31P{1H} NMR
(6) For a definition of the slip parameter ∆(M-C) see the footnotes
of Table 2; for a discussion of its values in various Ind complexes see
these reports: (a) Baker, R. T.; Tulip, T. H. Organometallics 1986, 5,
839. (b) Westcott, S. A.; Kakkar, A.; Stringer, G.; Taylor, N. J .; Marder,
T. B. J . Organomet. Chem. 1990, 394, 777.
Comparing the main structural features of 4 and its
analogue [(η3:η1-IndCH2CH2NMe2)Ni(PPh3)]+ shows that
(7) Zargarian, D. Coord. Chem. Rev. 2002, 233-234, 157.
(8) (a) Huber, T. A.; Bayrakdarian, M.; Dion, S.; Dubuc, I.; Be´langer-
Garie´py, F.; Zargarian, D. Organometallics 1997, 16, 5811. (b) Huber,
T. A.; Be´langer-Garie´py, F.; Zargarian, D. Organometallics 1995, 14,
4997.
(9) Vollmerhaus, R.; Be´langer-Garie´py, F.; Zargarian, D.; Organo-
metallics 1997, 16, 4762.
(10) A search using ConQuest (v 1.4, CCDC 2002) gave an average
Ni-N distance of 2.054 Å when N ) 2-(alkyl)pyridine.

Aminoalkyl-Substituted Indenyl-Ni Compounds
Organometallics, Vol. 22, No. 15, 2003 3127
Ta ble 3. Electr och em ica l a n d NMR Da ta for Com p lexes 1-5 a n d Rela ted Der iva tivesa
1H (ppm)
H3
31P{1H} (ppm)
H2
H4
ERed (V obs)
ERed (V vs SCE)
1b
30.6
30.7
30.8
30.8
31.2
34.6
30.3
29.1
6.43
6.60
6.60
6.70
6.50
6.93
6.80
6.78
6.27
3.22
3.50
3.43
3.42
3.52
4.06
3.97
3.94
4.79
6.05
6.04
6.10
6.11
6.03
6.10
5.50
5.54
6.05
-1.65
-1.64
-1.64
-1.70
-1.36
-1.34
-1.34
-1.41
-1.26
-1.05
-1.08
-1.16
-1.24
2c
3d
(IndCH2CH2NMe2)Ni(PPh3)Cld
(1-Me-Ind)Ni(PPh3)Clc
4e
-1.34
-1.37
-1.45
5c
[(η3,η1-Ind(CH2)2NMe2)Ni(PPh3)]+c
(1-Me-Ind)Ni(PPh3)2]+c
36.5, 32.9
a
b
All electrochemical studies were conducted in acetonitrile solutions and the NMR spectra are in the following solvents. Toluene-d8
-40 °C. c CDCl3. C6D6. e CD2Cl2.
d
the Ni-N distance is shorter and the overall Ni-Ind
interaction is somewhat stronger in complex 4, while
the Ni-P distances are quite similar (within 3σ). These
observations seemed to suggest that the Ni-N bond in
4 might be less labile, which is supported by the results
of ligand substitution reactions (vide infra). The stronger
Ni-N and Ni-Ind interactions seemed to suggest also
that the Ni center in 4 should be more electron rich,
but this was not borne out by the results of our
electrochemical measurements (vide infra); as will be
described later, these apparently contradictory observa-
tions can be reconciled by invoking NifN π-back-
bonding in 4.
dynamic process involving the reversible coordination
of the amine moiety to the Ni center. The compound
dominant at the low-temperature regime can be repre-
sented by the solid state structure of this complex
(Figure 1), in which no NfNi interaction is evident.
This was confirmed by the room-temperature CP-MAS
NMR spectrum of a solid sample of complex 1, which
showed signals similar to those of complexes bearing
nonfunctionalized susbtituents on Ind.
The high-temperature NMR spectra were studied
next in search of clues on the identity of the species
featuring NfNi chelation. In the case of complex 2, even
the highest temperature accessible to us (ca. 100 °C)
did not drive the dynamic process beyond the coales-
cence point; as a result, we were unable to directly
observe the species formed by the coordination of the
pyrrolidine moiety. On the other hand, the dynamic
process involving complex 1 advanced beyond the coa-
lescence point on the 1H NMR frequency range (400
MHz); we could, thus, detect the species present at high
temperature and compare some of its spectral features
to those of the species dominant at low temperature.
Solu tion Beh a vior of th e Neu tr a l Com p lexes.
The solution NMR spectra of the neutral complexes 1-3
have been compared to those of other IndNi compounds
in order to determine whether the amine moiety in 1-3
is involved in NfNi interactions (Table 3). Among the
complexes examined, the most straightforward spectra
were obtained for complex 3, which displayed room-
temperature spectral features similar to those of the
complexes bearing nonfunctionalized Ind ligands.7 For
example, the 31P{1H} NMR spectrum of this complex
showed a singlet resonance at 30.8 ppm, and the 1H
NMR spectrum showed the anticipated signals at ca.
6.60 and 3.50 ppm for H2 and H3, respectively, of the
Ind ligand (numbering scheme shown in the ORTEP
diagram, Figure 1). According to these spectra, little or
no NfNi interaction takes place in 3, presumably
because of the steric bulk of the (i-Pr)2N moiety. In
contrast, the amine moieties in complexes 1 and 2
reversibly coordinate to the Ni center, as inferred from
their NMR spectral features described below.
1
For example, the H NMR signal for the H3 proton in 4
moved from 3.22 ppm at -40 °C to 4.46 ppm at 90 °C,
while the signals for the methylene tether (IndCH2py)
moved from ca. 3.80 to 2.70 ppm. Most of the other
signals also moved with the temperature, but these were
partially or completely overlapped by other signals.
Unfortunately, the high-temperature 31P{1H} and 13C-
{1H} NMR spectra of 1 did not show any signals and
thus did not contribute to a reliable identification of the
complex formed at the high-temperature regime.
We propose that the dynamic process observed for
complexes 1 and 2 can be adequately described by the
equilibria depicted in Scheme 2. According to this
proposal, the amino tether can coordinate to the Ni
center to form the 18-electron intermediate (or transi-
tion state) shown; the equilibrium is driven further
forward at higher temperatures and with the more
nucleophilic amine moiety (CH2Py > CH2CH2N(C4H8)
≈ CH2CH2NMe2). This chelation step serves as model
for the initial step of the ligand substitution reaction
for the complexes IndNi(PR3)Cl, which has been shown
to proceed by an associative process.11 The NfNi
coordination might be facilitated by either the slippage
of the Ind ligand or the heterolytic dissociation of the
Ni-Cl bond, which would form the chelating cations.
Although the ionization of the Ni-Cl bond seemed
1
The low-temperature H, 31P{1H}, and 13C{1H} NMR
spectra of complexes 1 and 2 displayed the requisite
signals characteristic of the complexes bearing nonfunc-
tionalized Ind ligands. Thus, the low-temperature 31P-
{1H} NMR spectra of these complexes (ca. - 40 °C,
CDCl3 or toluene-d8) showed a singlet resonance at ca.
1
30-31 ppm, while the H NMR spectra showed all the
anticipated signals (e.g., 6.4-6.6 ppm for H2 and 3.2-
3.4 ppm for H3). Warming the samples resulted in a
gradual disappearance of all the signals, which occurred
at around room temperature for complex 1 and at 40-
50 °C for complex 2. That this spectral bleaching is not
caused by a thermal decomposition is evident from the
observation that subsequent cooling of the sample
restored all the original signals. By analogy with the
previously studied complex (IndCH2CH2NMe2)Ni(PPh3)-
Cl, which shows a similar spectral behavior,3 we con-
clude that complexes 1 and 2 are also subject to a
(11) Fontaine, F.; Dubois, M.-A.; Zargarian, D. Organometallics
2001, 20, 5145.

3128 Organometallics, Vol. 22, No. 15, 2003
Groux and Zargarian
unlikely on the basis of our earlier work,12 we were
prompted to see if it would occur more readily in polar
media.13 Examination of the NMR spectra of 1 and 4 in
DMSO and acetone showed that the ionization does take
place quite readily; on the other hand, the spectra of
samples in acetonitrile or chloroform resemble those of
samples in toluene. It appears, therefore, that the
dissociated Cl- is not sufficiently solvated in the latter
media and tends to return to the coordination sphere
of Ni; thus, the full ionization is difficult to attain.
Therefore, the available data point to the presence of
an equilibrium process leading up to the cations, as
shown in Scheme 2.
Liga n d E xch a n ge R ea ct ion s of t h e Ca t ion ic
Com p lexes. The previous section described the results
of NMR studies aimed at evaluating the extent of Ni-N
interaction in the neutral complexes under study. We
have carried out a series of ligand substitution reactions
on the cationic complexes 4 and 5 in order to measure
the relative strength of the NfNi binding. Comparing
the results of these studies to those of the analogous
studies carried out on [(η3:η1-IndCH2CH2NMe2)Ni-
(PPh3)]+ has shown that the pyridine moiety in 4 binds
more strongly to Ni than do the NMe2 and the pyrroli-
dine moieties, as described below.
Sch em e 3
did not lead to the formation of the anticipated bis(PPh3)
cation. The reaction with pyridine also resulted in the
broadening of the signal due to the coordinated PPh3;
in this case, however, the presence of >20 equiv of
pyridine led to the disappearance of the signal for
coordinated PPh3 and the appearance of the signal for
free PPh3. Thus, excess PPh3 does not displace the
pyridine moiety, whereas excess pyridine displaces the
coordinated PPh3. It is significant that the presence of
a chelating amine moiety should render the coordinated
PPh3 susceptible to displacement by an incoming amine
ligand.14
Taken together, the above results suggest that the
strength of the Ni-N bond in these complexes follows
the order 6 < 5 < [(η3:η1-Ind(CH2)2NMe2)Ni(PPh3)]+
<
Reacting 1 equiv of dppe with 4 or 5 resulted in the
displacement of both PPh3 and the chelating amine. The
resulting complexes [(η3:η0-IndCH2Py)Ni(dppe)]+ (9) and
[{η3:η0-Ind(CH2)2N(C4H8}Ni(dppe)]+ (10) were identified
on the basis of their characteristic 31P{1H} NMR spec-
tra, which displayed two broad signals due to the
inequivalent P nuclei in these complexes (67.7 and 70.8
ppm for 9, 68.4 and 65.3 ppm for 10). The broadness of
these signals is attributed to the hindered rotation of
the Ind ligand; a similar observation has been made for
the complex [{η3:η0-Ind(CH2)2NMe2}Ni(dppe)]+, which
was found to have a rotational energy barrier of 14.3
4. This order is further supported by the observation
that the neutral complex 1 reacts with the cations 5 or
[(η3:η1-Ind(CH2)2NMe2)Ni(PPh3)]+ to form 4 and the
corresponding neutral complex (IndCH2CH2NR2)Ni-
(PPh3)Cl (R2 ) Me2 or (CH2)4) (Scheme 3).
Electr och em ica l Stu d ies. It is reasonable to as-
sume that, all other factors being equal, the electron
density of the Ni center in the complexes (Ind∧NR2)-
Ni(PPh3)Cl and [(η3:η1-Ind∧NR2)Ni(PPh3)]+ should re-
flect the degree of the NfNi interaction, stronger
interactions leading to more electron-rich Ni centers.
Thus, in principle, a direct correlation should exist
between the strength of the Ni-N bond, as determined
from NMR studies described in the preceding two
sections, and the electron density at Ni, as inferred from
the reduction potential of the complex. To determine the
effect of NfNi binding on the electron density at the
Ni center, we have used cyclic voltammetry to measure
the reduction potentials of complexes 1-5, (IndCH2CH2-
NMe2)Ni(PPh3)Cl, and [(η3:η1-Ind(CH2)2NMe2)Ni(PPh3)]+-
[BPh4]-. The electrochemical measurements showed
that these complexes undergo irreversible, one-electron
reduction. The reduction potentials of these compounds
and those of related complexes not having any Ni-N
interaction were measured and corrected against the
standard calomel electrode (SCE) and are listed in Table
3. These data allow the following observations:15
(a) The cationic species are easier to reduce than the
neutral ones, as anticipated.
kcal mol-1 4a
.
In contrast to their similar reactivities with dppe,
complexes 4 and 5 reacted differently with PPh3 and
pyridine. Thus, reaction of 5 with PPh3 led to an
equilibrium between 5 and [{η3:η0-Ind(CH2)2N(C4H8)}-
Ni(PPh3)2]+ (8); as before, the bis(phosphine) species was
identified readily on the basis of its characteristic AB
pattern in the 31P{1H} NMR spectrum (CDCl3; 36.1 ppm
(d, 2J P-P ) 26.8 Hz) and 31.9 (d, 2J P-P ) 26.8 Hz)). The
keq was found to be 4.2 ((0.4), which is larger than the
corresponding value of 0.9 for the equilibrium arising
from the reaction of PPh3 with [{η3:η1-Ind(CH2)2NMe2}-
Ni(PPh3)]+.4a Similarly, the reaction of 5 with pyridine
formed [{η3:η0-Ind(CH2)2N(C4H8)}Ni(PPh3)(Py)]+ (11),
which showed a new signal at 32.1 ppm in the 31P{1H}
NMR spectrum; the keq in this case was 33 ((4), which
is again larger than the corresponding value of 9 ((1)
for the reaction of [{η3:η1-Ind(CH2)2NMe2}Ni(PPh3)]+
with pyridine.4a We conclude, therefore, that the Ni-N
bond is more labile in 5 relative to the NMe2 analogue.
Contrary to the above reactivities, the reaction of
complex 4 with excess PPh3 (up to 45 equiv) resulted in
the broadening of the original 31P{1H} NMR signal, but
(14) The generally stronger binding of phosphines vs amines to low-
valent late transition metals is well documented: (a) Collman, J . P.;
Hegedus, L. S.; Norton, J . R.; Finke, R. G. Principles and Applications
of Organotransition Metal Chemistry; University Science Books: Mill
Valley, CA, 1987; p 241, and references therein. (b) Li, M. P.; Drago,
R. S.; Pribula, A. J . J . Am. Chem. Soc. 1977, 99, 6900. (c) de Graaf,
W.; Boersma, J .; Smeets, W. J . J .; Spek, A. L.; van Koten, G.
Organometallics 1989, 8, 2907. (d) Wang, L.; Wang, C.; Bau, R.; Flood,
T. C. Organometallics 1996, 15, 491. (e) Widenhoefer, R. A.; Buchwald,
S. L. Organometallics 1996 15, 2755. (f) Widenhoefer, R. A.; Buchwald,
S. L. Organometallics 1996, 15, 3534. (g) Pfeiffer, J .; Kickelbick, G.;
Schubert, U. Organometallics 2000, 19, 62.
(12) For instance, analogous Ni-Cl complexes bearing nonfunction-
alized Ind substituents do not undergo ionization even in the presence
of very strongly donating ligands such as phosphines.
(13) We would like to thank one of the reviewers of our manuscript
for suggesting that we reexamine this issue.

Aminoalkyl-Substituted Indenyl-Ni Compounds
Organometallics, Vol. 22, No. 15, 2003 3129
(b) For both the neutral and cationic complexes, the
derivatives bearing the NMe2 moiety were more difficult
to reduce. For instance, the complexes 1-3 are reduced
at -1.36 to -1.34 V, compared to -1.41 V for (IndCH2-
CH2NMe2)Ni(PPh3)Cl; the cations 4 (-1.05 V) and 5
(-1.08 V) were also easier to reduce than [(η3:η1-
Ind(CH2)2NMe2)Ni(PPh3)]+ (-1.16 V). Clearly, the na-
ture of the tethered amine moiety modulates the level
of electron density at the Ni center.
P olym er iza tion of Olefin s. Many cationic Ni com-
plexes are active in the catalytic polymerization and
oligomerization of olefins.16 We have reported recently
that systems consisting of IndNi(PR3)X and methyl-
aluminoxane (MAO) catalyze both the dimerization and
polymerization of ethylene;17 on the other hand, the
dimerization of ethylene (but not its polymerization) is
also promoted by the highly electrophilic cations gener-
ated in-situ from the complexes (Ind)Ni(PR3)(OTf).18 The
available mechanistic information indicates that the
dimerization of ethylene in these systems proceeds by
an initial insertion of ethylene into the Ni-Ind bond;
subsequent â-H elimination from the resulting alkyl
ligand releases CH2dCH-Ind (detected in some cases18)
and generates a postulated, cationic, Ind-free Ni-H
species that serves as the main catalyst. The mecha-
nistic details of the ethylene polymerization reaction are
not known with certainty, but the involvement of
cationic species such as [IndNi(PR3)]+ in these reactions
has been ruled out.17
(c) The relatively easier reduction of the complexes
not possessing a chelating moiety (e.g., (1-Me-Ind)Ni-
(PPh3)Cl: ERed ) -1.26 V) shows that the NfNi
interaction causes a net increase in the electron density
at the Ni center in the neutral species. On the other
hand, replacing the chelating amine donor in the
cationic complexes by a second PPh3 ligand results in a
greater net transfer of electron density to Ni in the
cationic species (e.g., [(1-Me-Ind)Ni(PPh3)2]+: ERed
-1.24 V).
)
According to the data listed in Table 3, the electron
density at the Ni center decreases in the order (IndCH2-
CH2NMe2)Ni(PPh3)Cl > 1 ≈ 2 ≈ 3 and [(IndCH2CH2-
NMe2)Ni(PPh3)]+ > 5 > 4. On the other hand, the NMR
studies indicated the following relative orders of NfNi
interactions: 1 > (IndCH2CH2NMe2)Ni(PPh3)Cl ≈ 2 >
3 and 4 > [(η3: η1-IndCH2CH2NMe2)Ni(PPh3)]+ > 5.
Comparison of these orders reveals that the complexes
bearing the pyridine moiety (i.e., 1 and 4) seem to defy
the predicted correlation between Ni-N bond strength
and the reduction potential. This anomaly might be
rationalized in terms of the π-acidity of the pyridine
moiety: NifN π-back-bonding would be expected to
reinforce the Ni-N interaction in 1 and 4, which would
be reflected in the NMR spectra, but it would also
reduce the net electron density of the Ni center, which
would be reflected in the reduction potentials of these
complexes. The existence of some degree of NifN
π-back-bonding is also evident from the structural
parameters of complex 4. For example, the Ni-N bond
is somewhat shorter and the Ni-Ind interaction is
somewhat stronger in 4 than in [(η3: η1-IndCH2CH2-
NMe2)Ni(PPh3)]+ (Ni-N ) 1.95 vs 2.01 Å, ∆(M-C) )
0.24 vs 0.26 Å).
In conclusion, the electrochemical measurements are
very sensitive to the net electrophilicity of the Ni center
in these complexes, whereas the NMR studies can
evaluate the relative lability of the Ni-N chelation.
There exists some correlation between these param-
eters, except in cases where there is NifN π-back-
bonding. While it might seem counterintuitive to sug-
gest that the cationic Ni center is engaged in significant
back-bonding to the pyridine moiety, the above data
support this possibility.
Subsequent studies showed that cations bearing
chelating amine moieties such as [(η3:η1-Ind(CH2)2-
NMe2)Ni(PPh3)]+ are also active in the dimerization of
ethylene (in the presence of MAO)4b and the polymer-
ization of styrene (without cocatalysts).4a Although the
dimerization of ethylene by these systems might operate
by the insertion-type mechanisms discussed above, the
polymerization of styrene can also proceed via carbo-
cationic19 or radical20 pathways. It should be noted,
however, that the complex [(η3:η1-Ind(CH2)2NMe2)Ni-
(PPh3)]+ does not promote the polymerization of other
monomers such as ethyl(vinyl) ether or methyl meth-
acrylate, which are very prone to carbocationic21 or
radical22 polymerizations, respectively.
As a follow-up to the latter studies, we have examined
the polymerization activities of the cationic complexes
4-6 in order to assess the influence of the tether on
these reactions. The bulk of our studies has concen-
trated on the polymerization of styrene, because it gave
the most informative results among the monomers
tested (e.g., norbornene gave <5% yields of an in-
(16) (a) J ohnson, L. K.; Killian, C. M.; Arthur, S. D.; Feldman, J .;
McCord, E. F.; McLain, S. J .; Kreutzer, K. A.; Bennett, M. A.; Coughlin,
E. B.; Ittel, S. D.; Parthasarathy, A.; Tempel, D. J .; Brookhart, M. S.
DuPont, WO 96/23010, 1996. (b) J ohnson, L. K.; Killian, C. M.;
Brookhart, M. S. J . Am. Chem. Soc. 1995, 117, 6414. (c) Keim, W.;
Appel, R.; Gruppe, S.; Knoch, F. Angew. Chem. 1987, 99, 1042. (d)
Ostoja-Starzewski, K. A.; Witte, J . Angew. Chem. 1985, 97, 610. (e)
Flid, V. R.; Kuznetsov, V. B.; Grigor’ev, A. A.; Belov, A. P. Kinetics
Catal. 2000, 41(5), 604. (f) Flid, V. R.; Manulik, O. S.; Grigor’ev, A. A.;
Belov, A. P. Kinetics Catal. 2000, 41(5), 658. (g) Goodall, B. L.;
Benedikt, G. M.; McIntosh, L. H.; Barnes, D. A. U.S. Patent-5468819,
1995. (h) Goodall, B. L.; Benedikt, G. M.; McIntosh, L. H.; Barnes, D.
A.; Rhodes, L. F. U.S. Patent-5468819, 1995. (i) Bonnet, M. C.; Dahan,
F.; Ecke, A.; Keim, W.; Schulz, R. P.; Tkatchenko, I. J . Chem. Soc.,
Chem. Commun. 1994, 615. (j) Aresta, M.; Dibenedetto, A.; Quaranta,
E.; Lanfanchi, M.; Tiripicchio, A. Organometallics 2000, 19, 4199. (k)
Ihara, E.; Fujimura, T.; Yasuda, H.; Maruo, T.; Kanehisa, N.; Kai, Y.
J . Polym. Sci.: Part A: Polym. Chem. 2000, 38, 4764.
(15) One of the reviewers of our manuscript has asked for
a
justification for the use of reduction potentials in this context in light
of the irreversibility of the reduction process. Strictly speaking, the
reduction potential of an irreversible reduction (or oxidation) process
(17) Dubois, M.-A.; Wang, R.; Zargarian, D.; Tian, J .; Vollmerhaus,
R.; Li, Z.; Collins, S. Organometallics 2001, 20, 663.
might vary as
a
function of many different parameters such as
(18) Wang, R.; Groux, L. F.; Zargarian, D. Organometallics 2002,
21, 5531.
(19) (a) Yang, M.-L.; Li, K.; Sto¨ver, H. H. Macromol. Rapid Commun.
1994, 15, 425. (b) Satoh, K.; Nakashima, J .; Kamigaito, M.; Sawamoto,
M. Macromolecules 2001, 34, 396.
(20) (a) Li, P.; Qiu, K.-Y. Polymer 2002, 43, 5873. (b) Grognec, E.
L.; Claverie, J .; Poli, R. J . Am. Chem. Soc. 2001, 123, 9513.
(21) (a) Wang, Q.; Baird, M. C. Macromolecules 1995, 28, 8021. (b)
Baird, M. C. Chem. Rev. 2000, 100, 1471.
(22) Xia, J .; Matyjaszewski, K. Macromolecules 1997, 30, 7692, and
references therein.
electrolyte composition and nature of electrode. It is common practice,
however, to consider that in situations where an analogous series of
compounds are being studied under identical conditions the values of
reduction potential can be related, to a good approximation, to
structural or electronic properties of the compounds. In the present
case, since we are dealing with a family of complexes possessing very
similar structural features and compositions, and since the electro-
chemical studies were performed under identical conditions, we believe
that the reduction potential values represent fairly accurately the
electron richness of the metal centers in this family of complexes.

3130 Organometallics, Vol. 22, No. 15, 2003
Groux and Zargarian
Ta ble 4. P olym er iza tion of Styr en e Ca ta lyzed by
Com p lexes 4, 5, a n d 6a
The above results demonstrate that, among the
complexes studied, in-situ-generated 6 is the most active
precatalyst for the polymerization of styrene, which is
consistent with the weak Ni-N interaction in this
complex. The precatalysts 4 and 5 possess similar
activities, although 4 appears to give somewhat higher
TON values. On the other hand, all of these precatalysts
are more active than [(η3:η1-Ind(CH2)2NMe2)Ni(PPh3)]+.
On a first approximation, this order of reactivity seems
to correlate with the electrochemical properties of these
cationic complexes (Table 3): the most Lewis acidic
cation (i.e., the one easiest to reduce) appears to be the
most active catalyst for the polymerization of styrene.
Thus, the nature of the amine moiety in Ind∧NR2
ligands modulates both the electrophilicity of the Ni
center and its polymerization activity.
high Mw
polymers
low Mw
oligomers
T
time
Mw
Mw
run
cat.
(°C) (h) TON (× 103) Mw/Mn (× 103) Mw/Mn
1
2
3
4
5
6
7
8
9a
9b
9c
9d
9e
9f
4 or 5 20
48
48
48
48
48
48
48
48
1
0
127
207
554
35
180
486
1519
47
4
4
4
5
5
5
6a
4
40
60
80
40
60
80
80
60
1.9
3.0
5.7
1.5
134
200
1.4
1.3
2.3
3.0
1.2
1.4
153
145
22.9
1.6
1.7
3.0
1.8
3.8
4.0
4.4
4.2
4.3
1.0
1.5
1.5
1.6
1.6
1.6
4.5
86
7
24
30
48
142
163
185
207
184
191
193
1.4
1.2
1.3
a
The importance of the nature of the tethered amine
moiety on the reactivity of the complexes indicates that
the Ind ligand remains coordinated to the Ni center,
which implies, in turn, that the insertion-type mecha-
nism described above for the dimerization of ethylene
is not likely to be the polymerization pathway for
styrene. To test the feasibility of a carbocationic propa-
gation, we examined the reaction of N-vinylcarbazole;
the reactions were carried out in the dark in order to
avoid light-induced radical polymerization. This mono-
mer does indeed react with complex 4 (1:100 ratio; 80
°C) to give a solid (95% yield) consisting of a broad
mixture of oligomers (GPC in THF: Mw between 23 725
and 367, maximum at 575); the reaction with 5 under
the same conditions gave a solid with shorter oligomers
(Mw between 2760 and 360, maximum at 433). For
comparison, polymerization of this electron-rich olefin
by the cationic complex [L2Pt(Me)(MeCN)]+ (L2 ) di-
aryldiazabutadienes) gives polymers with Mw values of
ca. 23 000 and Mw/Mn of ca. 3 (at room temperature),23a
while initiation with the Lewis acid B(C6F5)3 gives
polymers with Mw values of ca. 100 000 and Mw/Mn of
ca. 3.6 (at -78 °C).21a
The above results seem to favor a carbocationic
pathway for the polymerization of styrene and N-
vinylcarbazole by the complexes 4/5. To gain further
insight on the course of the styrene polymerization
reaction in these systems, we monitored the progress
of a typical polymerization experiment (reaction of 4
with styrene at 60 °C, run 9) by performing GPC
analyses on 1 mL samples of the reaction mixture after
1, 4.5, 7, 24, 30, and 48 h. The results of this experiment
show that the reaction generated mainly oligomers (up
to Mw of ca. 4000) during the initial stages. A steady
increase was noted in Mw values as a function of time
such that after a few hours the system seems to convert
the oligomers into high Mw polymers, which constitute
the dominant products after ca. 24 h. This reaction
profile can be interpreted as implying that the polym-
erization reactions promoted by 4 proceed via two
distinct pathways, one that is active throughout the
experiment and generates oligomers and another that
is activated after a few hours and generates longer chain
polymers.
Prepared in-situ by combining 3 with 5 equiv of NaBPh4.
tractable material). We have also studied briefly the
reactivity of N-vinylcarbazole, which is prone to carbo-
cationic23 or radical24 polymerizations, to address the
mechanistic issues alluded to above. To compare the
results of the present studies with those obtained from
our previous studies with the (CH2)2NMe2 analogue, we
have performed most of the polymerization experiments
under similar conditions, i.e., stirring the appropriate
precatalyst and 1000-2000 equiv of monomer in CH2-
Cl2 or dichloroethane at 20-80 °C over 48 h. In
experiments involving complex 6, given the above-
mentioned difficulty in isolating pure samples of this
complex, we have used a combination of 3/NaBPh4 (1:
5) to generate this species in-situ.
Initial tests showed that the reaction temperature had
a very important influence on the course of the polym-
erization reaction, giving different results in terms of
catalytic turnover numbers (TON), Mw of the products,
and polydispersity index values (Mw/Mn). Thus, neither
4 nor 5 reacted with the monomers at room temperature
(run 1, Table 4), presumably because the relatively
strong Ni-N bond does not break to facilitate the
coordination of the monomer. On the other hand, the
reaction of 4 with styrene at 40 °C resulted in low Mw
oligomers (run 2); increasing the temperature to 60 °C
gave a bimodal distribution of high Mw polymers and
low Mw oligomers (run 3), whereas at 80 °C we obtained
a fairly narrow distribution of high Mw species (run 4).
Higher temperatures also led to higher activities (i.e.,
larger TON values). Similar observations were made for
the polymeriztion of styrene catalyzed by 5 (runs 5-7).
In contrast to the reactivities of 4 and 5, the polym-
erization of styrene in the presence of in-situ-generated
6 did proceed at room temperature, albeit with low
yields and smaller Mw. Moreover, polymerization of
styrene catalyzed by 6 at higher temperatures also gave
much higher yields compared to the corresponding
polymerizations catalyzed by 4 or 5; on the other hand,
the poly(styrene) obtained from the reaction of 6 dis-
played a unimodal distribution of fairly low Mw species
(run 8).
(23) (a) Albietz, P. J .; Kaiyuan, Y.; Eisenberg, R. Organometallics
1999, 18, 2747. (b) Cho, H.-N.; Choi, S.-K. J . Polym. Sci. A: Polym.
Chem. 1987, 25, 1769, and references 5-10 therein. (c) Bowyer, P. M.;
Ledwith, A.; Sherrington, D. C. Polymer 1971, 12, 509.
(24) (a) Ellinger, L. P. Polymer 1964, 5, 559. (b) J ones, R. G.; Khalid,
N. Makrom. Chem. 1982, 26, 625.
To delineate the importance of continued heating for
the polymerization process, two reactions were carried
out under standard conditions (4/styrene/dichloro-
ethane/80 °C/48 h) with the difference that one was

Aminoalkyl-Substituted Indenyl-Ni Compounds
Organometallics, Vol. 22, No. 15, 2003 3131
data for 1 were collected on a Nonius CAD-4 diffractometer
with graphite-monochromated Cu KR radiation at 293(2) K
using CAD-4 software. The refinement of the cell parameters
was done with the CAD-4 software,25 and the data reduction
used NRC-2 and NRC-2A.26 Dark red crystals of 4 were
obtained from a -20 °C CH2Cl2/Et2O solution of 4. The crystal
data for 4 were collected on a Bruker AXS SMART 2K
diffractometer with graphite-monochromated Cu KR radiation
at 223(2) K using SMART.27 Cell refinement and data reduc-
tion were done using SAINT.28 Both structures were solved
by direct methods using SHELXS9729 and difmap synthesis
using SHELXL96;30 the refinements were done on F2 by full-
matrix least squares. All non-hydrogen atoms were refined
anisotropically, while the hydrogens (isotropic) were con-
strained to the parent atom using a riding model. Crystal data
and experimental details for 1 and 4 are listed in Table 1, and
selected bond distances and angles are listed in Table 2.
(η3:η0-In d CH2P y)Ni(P P h 3)Cl (1). An Et2O solution (250
mL) containing IndCH2Py (300 mg, 1.45 mmol) and BuLi (0.58
mL of a 2.5 M solution in hexane) was stirred for 4 h at room
temperature and then transferred (dropwise over 1.5 h) to a
stirred slurry of (PPh3)2NiCl2 (1.23 g, 1.89 mmol) in Et2O (50
mL). The dark red solution was then filtered, and the solvent
volume was reduced to ca. 75 mL. A dark red powder
precipitated as fairly pure product (160 mg, 0.28 mmol, 20%
yield), which was recrystallized from cold Et2O to give crystals
suitable for X-ray analysis. 31P{1H} NMR (toluene-d8, -40
heated only during the initial 2 h of the polymerization
reaction, while the other was heated throughout the
entire experiment. Analysis of the polymers showed that
the partially heated reaction gave about a quarter of
the yield of the poly(styrene) obtained from the other,
indicating that higher temperatures are necessary not
only for initiating the polymerization reaction but also
for sustaining it.
Another experiment was carried out in order to
answer the important question of whether PPh3 remains
coordinated to Ni during the polymerization reaction.
Thus, we followed a polymerization experiment by
monitoring the 31P NMR spectrum of a 0.016 M solution
of complex 4 containing 100 equiv of styrene (0.5 mL
ClCH2CH2Cl/0.1 mL C6D6) at 50 °C. The NMR spectra
did not show the presence of a free phosphine, implying
that this ligand remains coordinated to Ni during the
reaction; by inference, we believe that it is the amine
moiety that detaches from the Ni center to open up a
coordination site. As mentioned above, the displacement
of the chelating amine ligand is slow at low tempera-
tures, and so initiation of the catalysis requires higher
temperatures. It is not clear, however, why the high
temperatures must be sustained throughout the polym-
erization, because carbocationic propagation should not
require high temperatures.21b
1
°C): 30.6 ppm. H NMR (toluene-d8, -40 °C): 7.50 and 7.00
(m, py and PPh3), 7.33 (m, H7), 7.24 (m, H6), 6.60 (m, H5),
6.43 (H2), 6.05 (d, 3J H-H ) 7.6 Hz, H4), 3.80 and 3.66 (m, Ind-
CH2), 3.22 (H3). 13C{1H} CP-MAS: 157.9 (C9), 152.1 (C13),
134.9 (C11), 133.3 (o-C PPh3), 130.0, 129.4 and 128.1 (C10/
p-C and m-C PPh3), 126.9 and 125.7 (C5/C6)), 121.6 and 120.7
(C7/C12), 115.9 (C4), 107.3 (C1), 104.3 (C2), 68.1 (C3), 35.7
(IndCH2). Anal. Calcd for C33H27PNiNCl: C, 70.44; H, 4.84;
N, 2.49. Found: C, 70.56; H, 4.91; N, 2.11.
Con clu sion
The preparation of the neutral and cationic complexes
1-6 has allowed us to study in more detail the effect of
placing a hemilabile amino moiety adjacent to the Ni
center in this family of complexes. Studying the revers-
ible coordination of the amine moiety in the neutral
complexes and measuring the impact of NfNi coordi-
nation on the reduction potentials of these complexes
have allowed us to gauge the nucleophilicity of the
hemilabile moiety. The correlation between the electro-
philicity of the Ni center in the cationic complexes and
their catalytic activities provides a convenient means
of predicting catalytic activity on the basis of simple
ligand kinetics and electrochemical measurements.
Although our results do not provide strong support for
the involvement of a carbocationic pathway in the
polymerization reactions, this possibility is most con-
sistent with the experimental observations.
{η3:η0-In d (CH2)2N(C4H8)}Ni(P P h 3)Cl (2). An Et2O solu-
tion (200 mL) containing Ind(CH2)2NC4H8 (1.00 g, 4.69 mmol)
and BuLi (1.88 mL of a 2.5 M solution in hexane) was stirred
for 5 h and then transferred (dropwise over 2 h) to a stirred
slurry of (PPh3)2NiCl2 (3.7 g, 5.6 mmol) in Et2O (30 mL). Half
of the solvent was then evaporated and the solution filtered.
The filtrate volume was further reduced to ca. 50 mL and the
resulting solution cooled to -15 °C. A first crop of the desired
product (ca. 1 g of a reddish solid) was isolated. Recrystalli-
zation from CH2Cl2/pentane gave 550 mg of pure product (0.97
1
mmol, 21% yield). 31P{1H} NMR (CDCl3): 30.7 ppm. H NMR
(CDCl3, -40 °C): 7.7-7.0 (PPh3, H6 and H7), 6.96 (H5), 6.60
(H2), 6.04 (H4), 3.50 (H3) 3.06 and 2.87 (CH2N), 2.62 (NCH2
cycle), 2.18 (IndCH2), 1.82 (NCH2CH2 cycle). 13C{1H} NMR
2
(CDCl3, -40 °C): 133.9 (d, J P-C ) 11 Hz, o-C of PPh3), 132.1
1
and 131.9 (C3A/C7A), 131.1 (d, J P-C ) 44.8 Hz, i-C of PPh3),
Exp er im en ta l Section
130.4 (p-C of PPh3), 128.3 (d, 3J P-C ) 9 Hz, m-C of PPh3), 126.7
2
and 126.3 (C5/C6), 117.9 and 116.4 (C4/C7), 104.9 (d, J P-C
)
Gen er a l Com m en ts. All manipulations except the GPC
analyses were performed under an inert atmosphere of N2
using standard Schlenk techniques and a drybox. Dry, oxygen-
free solvents were prepared by distillation from appropriate
drying agents and employed throughout. The substituted
indenyl ligands have been prepared by adding the appropriate
Cl∧NR2 to a solution of LiInd, as described previously.5 All
other reagents used in the experiments were obtained from
commercial sources and used as received. The elemental
analyses were performed by the Laboratoire d’Analyse EÄ l-
e´mentaire (Universite´ de Montre´al). The spectrometers used
for recording the NMR spectra are Bruker AMXR400 (1H (400
MHz), 13C{1H} (100.56 MHz), and 31P{1H} (161.92 MHz)) and
Bruker AV300 (1H (300 MHz) and 31P{1H} (121.49 MHz)). 13C-
{1H}-CP-MAS (75.49 MHz) spectra were recorded on a Bruker
DSX300 spectrometer.
14 Hz, C1), 103.0 (C2), 67.1 (C3), 54.1 (NCH2, cycle), 53.1
(CH2N), 26.2 (IndCH2), 23.2 (NCH2CH2, cycle). Anal. Calcd for
C
33H33PNiNCl: C, 69.69; H, 5.85; N, 2.46. Found: C, 69.33;
H, 5.83; N, 2.44.
{η3:η0-In d (CH2)2N(i-P r )2}Ni(P P h 3)Cl (3). An Et2O solu-
tion (200 mL) containing Ind(CH2)2N(i-Pr)2 (800 mg, 3.29
(25) CAD-4 Software, Version 5.0; Enraf-Nonius: Delft, The Neth-
erlands, 1989.
(26) Gabe, E. J .; Le Page, Y.; Charlant, J .-P.; Lee, F. L.; White, P.
S. J . Appl. Crystallogr. 1989, 22, 384.
(27) SMART, Release 5.059; Bruker Molecular Analysis Research
Tool; Bruker AXS Inc.: Madison, WI 53719-1173, 1999.
(28) SAINT, Release 6.06; Integration Software for Single-Crystal
Data; Bruker AXS Inc.: Madison, WI 53719-1173, 1999.
(29) Sheldrick, G. M. SHELXS, Program for the Solution of Crystal
Structures; University of Goettingen: Germany, 1997.
(30) Sheldrick, G. M. SHELXL, Program for the Refinement of
Crystal Structures; University of Goettingen: Germany, 1996.
Cr ysta l Str u ctu r e Deter m in a tion s. Dark red crystals of
1 were obtained from a -20 °C Et2O solution of 1. The crystal

3132 Organometallics, Vol. 22, No. 15, 2003
Groux and Zargarian
mmol) and BuLi (1.31 mL of a 2.5 M solution in hexane) was
stirred for 16 h at room temperature and then transferred
(dropwise over 2 h) to a stirred slurry of (PPh3)2NiCl2 (2.8 g,
4.3 mmol) in Et2O (50 mL). The mixture was then filtered,
and the filtrate volume was reduced to ca. 20 mL and cooled
to -15 °C. The pure product was isolated as a dark red powder
after multiple precipitation from cold ether and washings with
hot hexanes (630 mg, 1.05 mmol, 32% yield). 31P{1H} NMR
(C6D6): 30.8 ppm. 1H NMR (C6D6): 7.66 and 6.98 (PPh3), 7.30
Ch a r t 1
3
3
(d, J H-H ) 7.8 Hz, H7), 7.10 (t, J H-H ) 7.8 Hz, H6), 6.83 (t,
[{η3:η0-In d (CH2)2N(i-P r )2}Ni(P P h 3)2][BP h 4] (7). {Ind-
(CH2)2N(i-Pr)2}Ni(PPh3)Cl (95.4 mg, 0.16 mmol), PPh3 (360 mg,
1.37 mmol), and NaBPh4 (340 mg, 1.0 mmol) were stirred in
CH2Cl2 (20 mL) for 4 h, then filtered and evaporated. The
resulting solid was dissolved in CH2Cl2 (2 mL) and precipitated
by adding hexanes (50 mL). Repeated recrystallizations did
not give a pure product because the dissociation of one of the
phosphines allowed the chelation of the tether to produce [{η3:
η1-Ind(CH2)2N(i-Pr)2}Ni(PPh3)][BPh4] (6-10%). 31P{1H} NMR
3
3J H-H ) 7.6 Hz, H5), 6.60 (H2), 6.10 (d, J H-H ) 7.6 Hz, H4),
3.43 (H3), 3.05 and 2.98 (m, Ind-CH2CH2N), 2.40 and 2.26
(NCHMe2), 1.01 (m, NCH(CH3)2). 13C{1H} NMR (C6D6): 134.6
2
1
(d, J P-C ) 11 Hz, o-C of PPh3), 132.8 (d, J P-C ) 42.8 Hz, i-C
of PPh3), 130.3 (p-C of PPh3), 128.5 (m-C of PPh3), 126.5 and
126.2 (C5/C6), 118.7 and 116.9 (C4/C7), 106.8 (C1), 103.7 (C2),
66.9 (C3), 48.4 (NCHMe2), 42.4 (CH2N), 29.0 (IndCH2), 21.1
(NCH(CH3)2). Anal. Calcd for C35H39PNiClN: C, 70.20; H, 6.56;
N, 2.34. Found: C, 69.84; H, 6.81; N, 2.18.
2
2
(CDCl3): 36.8 (d, J P-P ) 25 Hz) and 32.5 (d, J P-P ) 25 Hz).
[(η3:η1-In d CH2P y)Ni(P P h 3)][BP h 4] (4). A CH2Cl2 solution
(10 mL) containing (IndCH2Py)Ni(PPh3)Cl (200 mg, 0.36 mmol)
and NaBPh4 (730 mg, 2.2 mmol) was stirred for 24 h and then
filtered. The filtrate volume was reduced to ca. 1 mL, and Et2O
(ca. 20 mL) was added to precipitate the product. Repeated
precipitation gave the pure product as an orange powder (175
mg, 0.21 mmol, 58% yield). 31P{1H} NMR (CDCl3): 33.1 ppm;
1H NMR (CDCl3): 7.6-6.9 (PPh3, BPh4, H5 to H7), 6.51 (H2),
2
2
6.25 (d, J H-H ) 6.5 Hz, H4 or H7), 6.02 (d, J H-H ) 7.4 Hz,
H4 or H7), 4.89 (d, J H-H ) 3.2 Hz, H3), 2.75 (m, NCH2), 2.35
and 2.28 (m, IndCH2), 2.40 and 2.26 (NCHMe2), 0.78 (m, NCH-
(CH3)2).
2
P olym er iza tion of Styr en e. Runs 1-7: 4 and 5 (ca. 15
mg) and styrene (ca 3.7 g, 2000 equiv) were stirred for 2 days
in CH2Cl2 (8 mL) at room temperature (runs 1 and 5), or in
dichloroethane at 40 °C (runs 2 and 5), 60 °C (runs 3, 6, and
8), and 80 °C (runs 4 and 7). Evaporation of the solvent and
unreacted styrene gave a white solid, which was isolated (run
2: 0.23 g, 6.3% yield; run 3: 0.37 g, 10% yield; run 4: 1.02 g,
28% yield; run 5: 0.07 g, 1.8% yield; run 7: 0.33 g, 9% yield;
run 8: 0.93 g, 24% yield) and analyzed by GPC (THF). A
representative 1H NMR (CDCl3) spectrum: 7.07 (br), 6.57 (br),
1.88 (br), 1.46 (br). A representative 13C{1H} (CDCl3) spectrum:
145.3 (ipso-C), 128.1 (o- and m-C), 125.8 (p-C), 44.1 and 40.6
(alkyl chain). Run 8: Neutral complex 3 (10.0 mg, 0.0167
mmol), NaBPh4 (28.6 mg, 0.083 mmol, 5 equiv), and styrene
(3.48 g, 33.4 mmol, 2000 equiv) were mixed together in
dichloroethane (5 mL) and stirred for 48 h at 80 °C. Evapora-
tion of the solvent and unreacted styrene gave a gray solid,
which was isolated (2.642 g, 76% yield) and analyzed by GPC
(THF).
P olym er iza tion of N-Vin ylca r ba zole. Complex 4 or 5 (ca.
11 mg) and N-vinylcarbazole (ca. 250 mg, 100 equiv) were
stirred for 4 days in dichloroethane (2 mL) at room tempera-
ture or at 80 °C. Evaporation of the solvent left a light red
solid consisting of unreacted N-vinylcarbazole (room-temper-
ature experiments) or poly(N-vinylcarbazole) at >95% yield
(80 °C experiments). Analysis by GPC (THF) indicated that
the molecular weight of the polymer ranges between 23 725
and 367, with a maximum at 575 (reaction with 4), or 2760
and 360, with a maximum at 433. These samples of poly(N-
vinylcarbazole) were partially soluble in CDCl3 and could be
characterized by NMR spectroscopy (Chart 1).31 1H NMR
(CDCl3): 8.1 (br, H5), 7.9 (br, H4), 7.6 (br), 7.3 (br, H7, H6),
6.6 (br, H3, H8, H2), 5.9 (br), 5.1 (br, H1), 3.7 (br), 2.4 (br), 2.0
(br), 1.8 (br), and 1.6 (br). 13C{1H} NMR (CDCl3) 139.2 (C1a,
C8a), 126.1 (C7, C2), 125.4 (C5a), 125.1 (C4a), 123.7 (C5), 123.4
(C4), 120.1 (C6), 118.9 (C3), 110.3 (C8), 110.1 (C1), 50.1, 48.1,
43.3.
1
(CD2Cl2): 34.6 ppm. H NMR (CD2Cl2): 7.6-6.7 (PPh3, BPh4,
3
3
H5 to H7, py), 6.93 (d, J H-H ) 5.5 Hz, H2), 6.52 (t, J H-H
)
3
6.6 Hz, H5), 6.10 (d, J H-H ) 7.7 Hz, H4), 4.06 (H3), 3.87 and
3.57 (d, J H-H ) 18.1 Hz, IndCH2). 13C{1H} NMR (CD2Cl2):
2
2
175.7 (d, J P-C ) 7 Hz, C9), 163.8 (4-line multiplet, J B-C ) 49
Hz, i-C of BPH4), 152.4 (d, J P-C ) 4 Hz, C13), 139.1 (C11),
135.8 (m-C of BPH4), 133.6 (d, J P-C ) 12 Hz, o-C of PPh2),
131.6 (p-C of PPh2), 129.2 (d, J P-C ) 10 Hz, m-C of PPh2),
2
2
3
128.9, 128.6, and 128.5 (i-C of PPh2/C5/C6), 125.5 (o-C of
BPH4), 124.7 (C10), 124.6 and 124.4 (C3A/C7A), 123.4 (C12),
121.6 (p-C of BPH4), 118.3 and 117.9 (C4/C7), 108.7 (C2), 100.9
2
(d, J P-C ) 8 Hz, C1), 72.3 (C3), 34.5 (IndCH2). Anal. Calcd
for C57H47PNiNB: C, 80.88; H, 5.60; N, 1.66. Found: C, 80.55;
H, 5.86; N, 1.73.
[{η3:η1-In d (CH2)2N(C4H8)}Ni(P P h 3)][BP h 4] (5). A CH2Cl2
solution (20 mL) containing {Ind(CH2)2N(C4H8)}Ni(PPh3)Cl
(300 mg, 0.53 mmol) and NaBPh4 (1.08 g, 3.16 mmol) was
stirred for 4 h and then filtered. The filtrate volume was
reduced to ca. 6 mL, and Et2O (ca. 30 mL) was added to
precipitate the product. Repeated precipitation gave the pure
product as an orange powder (280 mg, 62% yield). 31P{1H}
NMR (CDCl3): 30.3 ppm. 1H NMR (CDCl3): 7.6-6.9 (PPh3,
2
BPh4, H5 to H7), 6.80 (H2), 5.50 (d, J H-H ) 7.4 Hz, H4), 3.97
(H3), 2.55 (m, IndCH2), 2.4 to 1.4 (m, NCH2), 1.2 to 0.6
(NCH2CH2). 13C{1H} NMR (CDCl3): 163.5 (4-line multiplet,
J B-C ) 49 Hz, i-C of BPH4), 136.5 (m-C of BPH4), 133.7 (d,
2J P-C ) 12 Hz, o-C of PPh2), 131.7 (p-C of PPh2), 129.3 (d, 3J P-C
1
) 10 Hz, m-C of PPh2), 129.3 (d, J P-C ) 36 Hz, i-C of PPh2),
128.4 and 127.7 (C5/C6), 126.9 and 123.9 (C3A/C7A), 125.7
(o-C of BPH4), 121.9 (p-C of BPH4), 118.4 and 118.3 (C4/C7),
109.8 (d, J P-C ) 10 Hz, C1), 106.8 (C2), 70.7 (C3), 70.1, 59.7
and 58.4 (CH2N), 23.7 (IndCH2), 21.3 and 21.1 (NCH2CH2).
Anal. Calcd for C57H53PNiNB: C, 80.31; H, 6.27; N, 1.64.
Found: C, 80.39; H, 6.54; N, 1.52.
R ea ct ion of {In d (CH2)2N(i-P r )2}Ni(P P h 3)Cl (3) w it h
Na BP h 4. {Ind(CH2)2N(i-Pr)2}Ni(PPh3)Cl (31 mg, 0.05 mmol)
and NaBPh4 (106.3 mg, 0.31 mmol) were stirred in CH2Cl2 (80
mL) for 4 h, filtered, and evaporated. The resulting solid was
dissolved in CH2Cl2 (0.75 mL) and precipitated by adding
hexanes (40 mL). The 31P{1H} NMR (CDCl3) spectrum showed
four major signals, as follows: 29.3, attributed to [{η3:η1-Ind-
(CH2)2N(i-Pr)2}Ni(PPh3)][BPh4] (6); 30.7, attributed to un-
Cyclic Volta m m etr y. Electrochemical measurements were
performed on an Epsilon Electrochemical Analyzer using CH3-
CN solutions of the nickel(II) complexes (0.002 M) and n-Bu4-
NPF6 (0.1 M). Cyclic voltammograms were obtained in a
standard, one-compartment electrochemical cell using a graph-
ite-disk electrode as working electrode, a platinum wire as the
counter electrode, and an Ag-AgNO3 (0.01 M in CH3CN)
2
reacted 3; 32.1 and 36.5 (d, J P-P ) 25 Hz), attributed to [{η3:
(31) Karali, A.; Froudakis, G. E.; Dais. P. Macromolecules 2000, 33,
3180.
η0-Ind(CH2)2N(i-Pr)2}Ni(PPh3)2][BPh4] (7).

Aminoalkyl-Substituted Indenyl-Ni Compounds
Organometallics, Vol. 22, No. 15, 2003 3133
reference electrode. The cyclic voltammetry was performed in
the potential range -2.8 to 0.8 V using scan rates of 50-200
mV/s. Under these conditions, E1/2 for the Fc+-Fc couple is
90 mV.32
(dppe; 15 mg, 0.039 mmol, ca. 3 equiv) were dissolved in CD2-
Cl2, and the sample was analyzed by NMR after 2 h. The 31P-
{1H} NMR spectrum showed free PPh3 and free dppe along
1
with two broad signals at 68.4 and 65.3 ppm. H NMR (CD2-
Cl2): 7.6-6.7 (dppe, PPh3, BPh4, H5 to H7, py), 6.56 (d, 3J H-H
Rea ction of [(η3:η1-In d CH2P y)Ni(P P h 3)][BP h 4] (4) w ith
P P h 3. Compound 4 (18 mg, 0.021 mmol) and PPh3 (57 mg,
0.22 mmol, ca. 10 equiv) were dissolved in CD2Cl2 (0.75 mL),
3
) 7.8 Hz, H4 or H7), 6.03 (H2), 5.93 (d, J H-H ) 8.2 Hz, H4 or
H7), 5.31 (H3), 2.49, 2.38, and 2.29 (NCH2CH2), 2.11 (free
dppe), 1.72 (CH2P).
1
and H and 31P{1H} NMR spectra were recorded 15 min later.
Rea ction of [(η3:η1-In d CH2P y)Ni(P P h 3)][BP h 4] (4) w ith
P yr id in e. Compound 4 (29 mg, 0.034 mmol) and pyridine
(10.9 µL, 0.14 mmol, ca. 4 equiv) were dissolved in CD2Cl2 (0.75
mL), and the sample was analyzed by NMR after 15 min. The
31P{1H} NMR spectrum showed the broadening of the signal
of 4 (34.6 ppm). The addition of three portions of pyridine (for
a total of 8, 16, and 24 equiv) led to further broadening of the
signal of 4 until it disappeared and gave rise to the signal for
free PPh3. All the volatiles were then removed under vacuum
and the 31P{1H} NMR spectrum was recorded, which showed
that the main phosphorus-containing species is PPh3 and
implied the decomposition of 4.
The 31P{1H} NMR spectrum showed the signals of the starting
material only (δ ) 34.6 ppm); the signal due to free PPh3 was
not detected. In the 1H NMR spectrum, the only difference
noted was the increase of the intensities of the signals for PPh3.
A second portion of PPh3 (76 mg, 0.29 mmol, total of ca. 24
equiv) was added and the mixture analyzed by NMR. The 31P-
{1H} NMR spectrum showed the starting material (δ ) 34.8
ppm) along with a new broad peak at 9.4 ppm. No new peaks
were detected in the 1H spectrum, which showed the signals
for 4 and PPh3 (increased intensity). A last portion of PPh3
(116 mg, 0.44 mmol, for a total of ca. 45 equiv) was added,
and the spectra were recorded. The 31P{1H} NMR spectrum
showed the starting material (δ ) 34.9 ppm) and a broad peak
[{η3:η0-In d (CH2)2N(C4H8)}Ni(P P h 3)(P y)][BP h 4] (11) in
Equ ilibr iu m w ith 5. Compound 5 (29 mg, 0.034 mmol) and
pyridine (5.5 µL, 0.068 mmol, 2 equiv) were dissolved together
in CDCl3 (0.75 mL), and the 1H and 31P{1H} NMR spectra were
recorded 15 min later. 31P{1H} NMR (CDCl3): 32.1 ppm. 1H
NMR (CDCl3): 7.6-6.9 (PPh3, BPh4, Ind), 6.60 and 6.52 (H4/
H7), 6.28 (H2), 4.18 (br, H3), 2.79 and 2.55 (IndCH2CH2), 2.4
(m, NCH2), 1.73 (NCH2CH2). On the basis of the integration
of the 31P{1H} NMR signals a 2.3:1 ratio was established for
the complexes 11 and 5. An additional equivalent of pyridine
(2.3 µL, 0.034 mmol) was then added to the above sample, and
the NMR spectra were recorded 15 min later, which showed a
4.3:1 ratio of 11 and 5. Repeated addition of 1 equiv of pyridine
1
at -0.5 ppm. The H NMR spectrum was as for the previous
mixture. The anticipated AB signals (31P) were not detected,
implying that the complex [(η3:η0-IndCH2Py)Ni(PPh3)2]+ did
not form.
[(η3:η0-In d (CH2)2NC4H8)Ni(P P h 3)2][BP h 4] (8) in Equ i-
libr iu m w ith 5. Compound 5 (12 mg, 0.015 mmol) and PPh3
(14 mg, 0.054 mmol, ca. 3.7 equiv) were mixed together in
CDCl3 (0.65 mL) and analyzed by 1H and 31P{1H} spectroscopy
15 min later. The emergence of the new product 8 was evident
2
from the 31P{1H} NMR (CDCl3) spectrum: 36.1 ppm (d, J P-P
2
) 26.8 Hz) and 31.9 (d, J P-P ) 26.8 Hz). 1H NMR (CDCl3):
7.6-6.9 (PPh3, BPh4, Ind), 6.46 (H2), 6.35 and 6.02 (H4/H7),
4.89 (br, H3), 2.6-1.1 (signals for the tether overlapping with
those of 5). A 0.34:1 ratio of 8:5 was determined on the basis
of the integration of the 31P{1H} NMR signals. Additional PPh3
(20 mg, 0.077 mmol) was added to the sample, and the NMR
spectra were recorded 15 min later, showing a 0.71:1 ratio. A
final portion of PPh3 (25 mg, 0.095 mmol) was added and the
mixture analyzed by NMR spectroscopy, which showed a 1.48:1
ratio. The equilibrium constant has been calculated: Keq ) 4.2
( 0.4.
allowed the determination of the equilibrium constant: Keq
)
33 ( 4. Evaporation of the solution to dryness re-formed the
starting complex 5.
Ack n ow led gm en t. The Natural Sciences and En-
gineering Research Council of Canada, le fond FCAR
of Quebec, and the University of Montreal are gratefully
acknowledged for financial support. W. Baille and Prof.
J . Zhu are thanked for help with the GPC analyses, and
F.-G. Fontaine is thanked for help with the electro-
chemistry experiments. Prof. M. C. Baird is thanked for
valuable discussions on the relevance of carbocationic
pathways in the polymerization reactions promoted by
our complexes.
[(η3:η0-In d CH2P y)Ni(d p p e)][BP h 4] (9). Compound 4 (13
mg, ca. 0.015 mmol) and bis(diphenylphosphino)ethane (dppe,
19 mg, ca. 0.048 mmol, 3 equiv) were dissolved in CD2Cl2, and
the sample was analyzed by NMR after 2 h. The 31P{1H} NMR
spectrum showed free PPh3 and free dppe along with two broad
signals at 67.7 and 70.8 ppm. 1H NMR (CD2Cl2): 7.6-6.7
3
(dppe, PPh3, BPh4, H5 to H7, py), 6.64 (d, J H-H ) 7.3 Hz, H4
Su p p or tin g In for m a tion Ava ila ble: Complete details on
the X-ray analysis of 1 and 4, including tables of crystal data,
collection, and refinement parameters, bond distances and
angles, anisotropic thermal parameters, and hydrogen atom
coordinates. This material is available free of charge via the
Internet at http://pubs.acs.org.
3
or H7), 6.34 (H2), 5.96 (d, J H-H ) 7.8 Hz, H4 or H7), 5.47
(H3), 3.25 and 3.08 (d, 2J H-H ) 14.2 Hz IndCH2), 2.08 (CH2P).
[(η3:η0-In d (CH2)2NC4H8)Ni(d p p e)][BP h 4] (10). Compound
5 (11 mg, ca. 0.013 mmol) and bis(diphenylphosphino)ethane
(32) Pavlishchuk, V. V.; Addison, A. W. Inorg. Chem. Acta 2000,
298, 97.
OM030241Q