Regioselective hydroamination of acrylonitrile catalyzed by cationic pincer complexes of nickel(II)

Article abstract of DOI:10.1021/om800840u

The cationic pincer-type complexes [{((i-Pr₂PCH ₂CH₂)₂CH}Ni(NCCH₃)][BPh ₄] (1), [{2,6-(i-Pr₂PCH₂)₂-C ₆H₃}Ni(NCCH₃)][BPh₄] (2), [{2,6-(i-Pr₂PO)₂-C₆H₃}Ni(NCCH ₃)][BPh₄] (3), and [{2,6-(i-Pr₂PO) ₂-3,5-Cl₂-C₆H}Ni(NCCH₃)][BPh ₄] (6) have been prepared and fully characterized by NMR spectroscopy and X-ray crystallography. Cyclic voltammetry measurements of the Ni - Br precursors of 2, 3, and 6 indicated that substituting the CH₂ moiety in the ligand skeleton by O, or some of the aromatic protons by Cl, renders the metal center less susceptible to oxidation. Evaluating the catalytic activities of 1-3, 6, and the t-Bu analogue of 1 for addition of aniline to acrylonitrile showed 3 to be the most competent catalyst precursor. Isolation of [{(t-Bu ₂PCH₂CH₂)₂CH)Ni(NCCH ₂CH₂NHPh)][BPh₄] (7) from the reaction of [{(t-Bu₂PCH₂CH₂)₂CH}Ni(NCCH=CH ₂)][BPh₄] with aniline suggests that these cationic precursors act as Lewis acids that bind the nitrile moiety of acrylonitrile, thereby activating the olefinic moiety toward nucleophilic attack by aniline.

Full text of DOI:10.1021/om800840u

2134
Organometallics 2009, 28, 2134–2141
Regioselective Hydroamination of Acrylonitrile Catalyzed by
Cationic Pincer Complexes of Nickel(II)
Annie Castonguay, Denis M. Spasyuk, Nathalie Madern, Andre´ L. Beauchamp, and
Davit Zargarian*
De´partement de Chimie, UniVersite´ de Montre´al, Montre´al (Que´bec), Canada H3C 3J7
ReceiVed August 29, 2008
The cationic pincer-type complexes [{(i-Pr2PCH2CH2)2CH}Ni(NCCH3)][BPh4] (1), [{2,6-(i-Pr2PCH2)2-
C6H3}Ni(NCCH3)][BPh4] (2), [{2,6-(i-Pr2PO)2-C6H3}Ni(NCCH3)][BPh4] (3), and [{2,6-(i-Pr2PO)2-3,5-
Cl2-C6H}Ni(NCCH3)][BPh4] (6) have been prepared and fully characterized by NMR spectroscopy and
X-ray crystallography. Cyclic voltammetry measurements of the Ni-Br precursors of 2, 3, and 6 indicated
that substituting the CH2 moiety in the ligand skeleton by O, or some of the aromatic protons by Cl,
renders the metal center less susceptible to oxidation. Evaluating the catalytic activities of 1-3, 6, and
the t-Bu analogue of 1 for addition of aniline to acrylonitrile showed 3 to be the most competent catalyst
precursor. Isolation of [{(t-Bu2PCH2CH2)2CH}Ni(NCCH2CH2NHPh)][BPh4] (7) from the reaction of
[{(t-Bu2PCH2CH2)2CH}Ni(NCCHdCH2)][BPh4] with aniline suggests that these cationic precursors act
as Lewis acids that bind the nitrile moiety of acrylonitrile, thereby activating the olefinic moiety toward
nucleophilic attack by aniline.
Chart 1
Introduction
A number of PCP-type pincer complexes, introduced by Shaw
and co-workers in the 1970s,1 have demonstrated good catalytic
activities for a variety of organic reactions of interest.2 In the
past two decades, many groups have worked on modifying the
pincer ligands to improve particular reactions or applications.
Thus, Milstein, Andersson, Shibasaki, Sabounchei, and Jensen
have shown that the efficiency of PCP-type Pd complexes for
the Heck coupling can be increased by changing the nature of
the cyclometalated carbon from sp2 to sp3 hybridization,
incorporating oxygens in the ligand backbone, varying the
phosphorus substituents from t-Bu to i-Pr, or increasing the size
of the metallocycles from five- to six-membered.3 Different
donor moieties also play an important role in reactivities of
pincer complexes. For instance, Milstein has found that systems
based on PCN-type unsymmetrical ligands show reactivities
different from those of their better-known PCP analogues in
C-C vs C-H bond activation reactions,4 and van Koten has
demonstrated that the SO2-sensing activities of Pt complexes
based on NCN-type ligands can be completely altered by varying
the amino substituents from Me to Et.2a
* Corresponding author. E-mail: zargarian.davit@umontreal.ca.
(1) For some of the original reports on PCP-type pincer complexes see:
(a) Moulton, C. J.; Shaw, B. L. Dalton Trans. 1976, 1020. (b) Al-Salem,
N. A.; Empsall, H. D.; Markham, R.; Shaw, B. L.; Weeks, B. Dalton Trans.
1979, 1972. (c) Al-Salem, N. A.; McDonald, W. S.; Markham, R.; Norton,
M. C.; Shaw, B. L. Dalton Trans. 1980, 59. (d) Crocker, C.; Errington,
R. J.; Markham, R.; Moulton, C. J.; Odell, K. J.; Shaw, B. L. J. Am. Chem.
Soc. 1980, 102, 4373. (e) Crocker, C.; Errington, R. J.; Markham, R.;
Moulton, C. J.; Shaw, B. L. Dalton Trans. 1982, 387. (f) Crocker, C.;
Empsall, H. D.; Errington, R. J.; Hyde, E. M.; McDonald, W. S.; Markham,
R.; Norton, M. C.; Shaw, B. L.; Weeks, B. Dalton Trans. 1982, 1217. (g)
Briggs, J. R.; Constable, A. G.; McDonald, W. S.; Shaw, B. L. Dalton
Trans. 1982, 1225.
(2) For recent reviews on pincer-type complexes, see: (a) Albrecht, M.;
van Koten, G. Angew. Chem., Int. Ed. 2001, 40, 3750. (b) van der Boom,
M. E.; Milstein, D. Chem. ReV. 2003, 103, 1759. (c) Singleton, J. T.
Tetrahedron 2003, 59, 1837.
(3) (a) Sjo¨vall, S.; Wendt, O. F.; Andersson, C. J. Chem. Soc., Dalton
Trans. 2002, 1396. (b) Ohff, M.; Ohff, A.; van der Boom, M. E.; Milstein,
D. J. Am. Chem. Soc. 1997, 119, 11687. (c) Miyazaki, F.; Yamaguchi, K.;
Shibasaki, M. Tetrahedron Lett. 1999, 40, 7379. (d) Naghipour, A.;
Sabounchei, S. J.; Morales-Morales, D.; Canseco-Gonza´lez, D.; Jensen,
C. M. Polyhedron 2007, 26, 1445.
In the course of our recent studies on the PCP-type pincer
complexes of nickel,5 we have found that systems based on
the ligand PCsp3Pi-Pr (Chart 1) are better catalysts for the
Kumada-Corriu coupling in comparison to the closely
analogous ligands PCsp3
experiments have also shown that complexes based on
P .
t-Bu and PCsp2Pi-Pr 5h Electrochemical
PCsp3P
i-Pr and POCsp3OPi-Pr ligands are easier to oxidize (NiII
f NiIII) than their counterparts based on PCsp2Pi-Pr and
(4) Rybtchinski, B.; Milstein, D. Angew. Chem., Int. Ed. 1999, 38, 870.
(5) (a) Groux, L. F.; Be´langer-Garie´py, F.; Zargarian, D. Can. J. Chem.
2005, 83, 634. (b) Sui-Seng, C.; Castonguay, A.; Chen, Y.; Gareau, D.;
Groux, L. F.; Zargarian, D. Top. Catal. 2006, 37, 81. (c) Castonguay, A.;
Sui-Seng, C.; Zargarian, D.; Beauchamp, A. L. Organometallics 2006, 25,
602. (d) Castonguay, A.; Beauchamp, A. L.; Zargarian, D. Acta Crystallogr.
2007, E63, m196. (e) Pandarus, V.; Zargarian, D. Chem. Commun. 2007,
978. (f) Pandarus, V.; Zargarian, D. Organometallics 2007, 26, 4321. (g)
Pandarus, V.; Castonguay, A.; Zargarian, D. Dalton Trans. 2008, 4756.
(h) Castonguay, A.; Zargarian, D.; Beauchamp, A. L. Organometallics 2008,
27, 5723.
10.1021/om800840u CCC: $40.75
2009 American Chemical Society
Publication on Web 03/03/2009

Cationic Pincer Complexes of Nickel(II)
Organometallics, Vol. 28, No. 7, 2009 2135
Scheme 1
POCsp2OPi-Pr (Chart 1).5e,h Finally, we have shown that
the cationic complexes [(PCsp3
t-Bu)Ni(NCCHdCH2)]+ and
(5), or CD3CN (6).8 Observation of one singlet in the 31P{1H}
NMR spectra and virtual triplets in the 1H and 13C{1H} NMR
spectra of these complexes confirmed the equivalence of the
two phosphorus nuclei and suggested their mutually trans
disposition. The greater electrophilicity of the Ni centers in
the cationic complexes is reflected in the more downfield
31P chemical shifts of 1-3 and 6 compared to those of the
corresponding neutral Ni-Br precursors: δ 76.5 for 1 vs 67.4
P
[(POCsp2OPi-Pr)Ni(NCCHdCH2)]+ catalyze the regioselective
addition of aniline to acrylonitrile,5b,f but the influence of
the various ligands on this reaction has not been studied.
As a continuation of the above studies, we have prepared a
series of cationic adducts of acetonitrile and evaluated their
catalytic activities for the addition of aniline to acrylonitrile.
Previous studies5c have demonstrated that acrylonitrile and
acetonitrile adducts are in equilibrium (Keq ≈ 1), which implies
that the latter should be precatalysts for the target reaction. In
for (PCsp3P
i-Pr)NiBr (C6D6); 70.6 for 2 vs 61.8 for (PCsp2Pi-Pr)NiBr
(CDCl3); 191.6 for 3 vs 188.2 for (POCsp2OPi-Pr)NiBr
(CDCl3); 197.2 for 6 vs 192.2 for 5 (C6D6). The presence of
a coordinated acetonitrile in 1-3 was indicated by a singlet
addition to the ligands PCsp3P P P
i-Pr, PCsp3 t-Bu, PCsp2 i-Pr, and
1
resonance in their H and 13C{1H} NMR spectra (CDCl3):
POCsp2OPi-Pr, we selected a new ligand, POCsp2OPi-Pr-Cl2 (Chart
1), in order to study the difference in reactivity brought about
by the incorporation of electronegative Cl elements in the
aromatic ring.
0.7-0.8 ppm (CH3CN) and ∼1 ppm (CH3CN).9 On the other
hand, the quaternary carbon of the coordinated acetonitrile
molecule (CH3CN) was only observed in the 13C{1H} NMR
spectra recorded on a high-field spectrometer (176 MHz,
CD2Cl2, δ): 130.7 (1), 133.0 (2), 128.8 (3), and 127.7 (6).
These high-field spectra also allowed us to detect the triplet
resonance for the cyclometalated carbon in 2 (∼153 ppm,
Results and Discussion
Synthesis and Characterization. The cationic species bearing
2
2JPC ) 14 Hz), 3 (∼123 ppm, JPC ) 20 Hz), and 6 (∼124
the PCsp3Pi-Pr and PCsp2Pi-Pr ligands were prepared by reacting
2
ppm, JPC ) 20 Hz), while the corresponding signal for 1
the previously reported precursors (PCsp3
P
i-Pr)NiBr5h and
2
(∼55 ppm, JPC ) 6 Hz) was also detectable at lower fields.
(PCsp2
P
i-Pr)NiBr6 with NaBPh4 in CH3CN; the target complexes 1
The assignment of the cyclometalated carbon resonance in 3
has been confirmed by a 31P INEPT experiment performed
in CD3CN. Finally, bands in the 2274-2282 cm-1 range of
the IR spectra for these complexes were assigned to ν(Ct N),
consistent with a similar assignment for the previously
and 2 were obtained as pale yellow powders in 85% and 79%
yields, respectively (Scheme 1). Curiously, the analogous reaction
of (POCsp2OPi-Pr)NiBr5e with NaBPh4 gave very low yields of
[(POCsp2OPi-Pr)Ni(NCCH3)][BPh4], 3, even with extended reaction
times, but the use of AgBPh4 allowed the preparation of the desired
complex in 65% yield. The new ligand POCsp2OPi-Pr-Cl2, 4, bearing
electronegative oxygen and chlorine atoms, was synthesized as
shown in Scheme 1 with the intention of preparing a more
electrophilic cationic complex. Reacting 4 with NiBr2 and DMAP
(4-(dimethylamino)pyridine) in refluxing toluene afforded complex
5 as an orange-brown solid (73% yield) that reacted with AgBPh4
in acetonitrile to give the target cationic species 6 (73% yield,
Scheme 1).7
reported [(PCsp3P
t-Bu)Ni(NCCH3)][BPh4] (2270 cm-1);5c com-
parison of these values to ν(Ct N) for free acetonitrile (2254
cm-1) implies little or no π-back-donation in these cationic
complexes.
Solid state structural studies carried out on single crystals of
all complexes allowed us to confirm the structural assignments
(8) Curiously, dissolving some batches of 6 in chloroform or methylene
chloride converted this complex into either 3 or (POCsp2OPi-Pr-Cl2)NiCl,
as confirmed by 31P{1H} NMR spectroscopy. Residual hydrochloric acid,
known to be present in chloroform, is known to transform our cationic pincer
complexes into their Ni-Cl analogues, and we have confirmed that reaction
of 6 with HCl · Et2O gives the corresponding Ni-Cl derivative. However,
the conversion of 6 into 3, and the fact that this transformation is not
reproducible, cannot be explained at this point.
All new complexes have been characterized by NMR
spectroscopy using samples prepared in CDCl3 (1-3), C6D6
´
(6) Ca´mpora, J.; Palma, P.; del R´ıo, D.; Alvarez, E. Organometallics
2004, 23, 1652.
(7) The high sensitivity of 4 to hydrolysis requires it to be used right
after its preparation, whereas complex 6 is fairly stable to hydrolysis.
(9) The 13C{1H} NMR spectrum of 6 in CD2Cl2 also displayed a singlet
corresponding to CH3CN (2.77 ppm).

2136 Organometallics, Vol. 28, No. 7, 2009
Castonguay et al.
Figure 1. ORTEP diagrams for complex 1. Thermal ellipsoids are shown at the 30% probability level. Hydrogens (and isopropyl methyl
carbons of the left view) are omitted for clarity. The alkyl chain of the ligand was found to occupy two positions, in a 7:3 ratio (A:B).
Figure 2. ORTEP views for complex 2. Thermal ellipsoids are shown at the 30% probability level. Hydrogens (and isopropyl methyl
carbons of the left view) are omitted for clarity.
Figure 3. ORTEP views for complex 3. Thermal ellipsoids are shown at the 30% probability level. Hydrogens (and isopropyl methyl
carbons of the left view) are omitted for clarity.
based on the above-discussed spectral data. ORTEP views of
complexes 1-3 and 5 are shown in Figures 1-4, the crystal
data and collection details are listed in Table 1, and selected
bond distances and angles are given in Table 2; in the case of
complex 6, X-ray analysis allowed us to establish the connec-
tivities, but low quality of the results obtained precludes

Cationic Pincer Complexes of Nickel(II)
Organometallics, Vol. 28, No. 7, 2009 2137
Figure 4. ORTEP diagrams for complex 5. Thermal ellipsoids are shown at the 30% probability level. Hydrogens (and isopropyl methyl
carbons of the left view) are omitted for clarity.
Table 1. Crystal Data Collection and Refinement Parameters for Complexes 1-3, 5, and 7
1
2
3
5
7
chemical formula
fw
T (K)
wavelength (Å)
space group
a (Å)
C43H60NiP2NB
722.38
150(2)
1.54178
Pbca
17.8194 (6)
19.0036 (6)
23.9586 (7)
90
C46H58NiP2NB
756.39
100(2)
1.54178
Pbca
18.9665(9)
17.7718(8)
24.7209(11)
90
C44H54NiP2O2NB.CH3CN
801.40
153(2)
1.54178
P21/c
11.8122(4)
17.2040(6)
21.9175(8)
90
103.087(2)
90
4
4338.3(3)
1.227
16.31
C18H29BrNiCl2P2O2
548.87
200(2)
1.54178
P21/n
11.0281(5)
17.9155(7)
13.0131(5)
90
111.017(2)
90
4
2400.01(17)
1.519
65.08
C54H75NiP2N2B
883.62
150(2)
1.54178
Pbca
18.7220(3)
18.4056(3)
28.4880(5)
90
b (Å)
c (Å)
R (deg)
ꢀ (deg)
γ (deg)
Z
90
90
8
90
90
8
90
90
8
V (Å3)
8113.2 (4)
1.183
16.41
3.69-78.99
0.0524
0.1429
0.0704
0.1566
1.137
8332.6(7)
1.206
16.23
3.58-69.05
0.0461
0.1128
0.0805
0.1290
0.935
9816.7(3)
1.196
14.52
3.10-69.04
0.0499
0.1306
0.0761
0.1473
1.036
Fcalcd (g cm-3
)
µ (cm-1
)
θ range (deg)
R1a [I > 2σ(I)]
wR2b [I > 2σ(I)]
R1 [all data]
wR2 [all data]
GOF
3.30-72.06
0.0376
0.0921
0.0442
0.0949
0.971
4.40-72.41
0.0478
0.1224
0.0509
0.1250
1.129
b
a R1 ) ∑(|Fo| - |Fc|)/∑|Fo|. wR2 ) {∑[w(Fo - Fc2)2]/∑[w(Fo )2]}1/2
.
2
2
Table 2. Selected Bond Distances (Å) and Angles (deg) for Complexes 1-3, 5, and 7
+
+
+
+
+
Ni(PCsp3Pi-Pr
)
Ni(PCsp3Pt-Bu
)
Ni(PCsp2Pi-Pr
)
Ni(POCsp2OPi-Pr
)
Ni(POCsp2OPi-Pr-Cl2)Br
Ni(PCsp3Pt-Bu
)
(1)
(2)
(3)
(5)
(7)
Ni-C(3)
1.9751(10)
1.9787(10)
2.1495(9)
2.1882(9)
1.807(2)
1.090(3)
1.383(4)
174.93(15)
164.4(3)
169.72(4)
91.49(8)
98.69(8)
91.13(10)
84.3(2)
1.969(3)
1.916(3)
1.8839(14)
1.879(2)
1.978(3)
Ni-P(1)
Ni-P(2)
Ni-N or -Br
N-C(10)
C(10)-C(11)
C(3)-Ni-N or -Br
2.2154(10)
2.2142(10)
1.908(3)
1.122(4)
1.471(5)
2.1724(8)
2.1889(8)
1.887(3)
1.132(4)
1.452(4)
177.51(11)
2.1692(5)
2.1753(5)
1.8862(13)
1.140(2)
1.455(2)
177.78(7)
2.1571(6)
2.1482(6)
2.3114(5)
2.2208(8)
2.2162(8)
1.900(2)
1.139(4)
1.461(4)
175.40(12)
173.98(16)
178.48(6)
P(1)-Ni-P(2)
169.31(4)
95.08(9)
95.56(8)
84.75(12)
168.55(4)
93.75(8)
97.69(7)
83.78(9)
162.719(1)
98.35(4)
98.66(4)
81.16(5)
165.64(3)
98.30(2)
96.03(2)
82.80(6)
170.54(3)
94.59(7)
94.86(7)
85.10(9)
P(1)-Ni-N or -Br
P(2)-Ni-N or -Br
P(1)-Ni-C(3)
P(2)-Ni-C(3)
78.61(10)
86.3(2)
84.79(12)
84.77(9)
81.95(5)
82.89(6)
85.44(9)
reporting the molecular structure of this compound here.10 All
complexes adopt a distorted square-planar geometry around the
nickel center. The Ni-P bond distances vary between 2.15 and
2.19 Å, which is a typical range for this type of pincer
complexes bearing i-Pr substituents on the phosphorus atoms.
The Ni-C(3) bond lengths observed for complexes 2, 3, and 5
are also in the range, 1.88-1.92 Å, usually observed for Ni-Csp2
(10) The X-ray data for 6 were recorded on a multiply twinned crystal;
numerous attempts at growing better quality crystals of this compound failed.

2138 Organometallics, Vol. 28, No. 7, 2009
Castonguay et al.
Table 3. Results of Catalytic Hydroamination of Acrylonitrilea
run
catalyst
solvent time (h) amine:olefin yield (%)b
1
2
3
4
5
PCsp3Pi-Pr (1)
THF
THF
THF
toluene
toluene
18
18
18
6
1:1
2:1
1:2
2:1
2:1
18
51
12
44
74
18
t-Bu
6
7
8
9
PC P
sp3
THF
THF
THF
toluene
toluene
18
18
18
6
1:1
2:1
1:2
2:1
2:1
6
14
10
25
25
10
18
i-Pr
11 PC
12
13
14
15
P
sp2
(2)
THF
THF
THF
toluene
toluene
18
18
18 h
6
1:1
2:1
1:2
2:1
2:1
37
63
45
70
70
18
Figure 5. Cyclic voltammograms of 5, (POCsp2OPi-Pr)NiBr, and
(PCsp2Pi-Pr)NiBr in CH2Cl2 (1 mM solutions) measured at 298 K
with 0.1 M of tetrabutylammonium hexafluorophosphate as elec-
trolyte (scan rate 100 mV s-1, E(V) vs Ag/AgCl).
16 POCsp2OPi-Pr (3)
THF
THF
THF
toluene
toluene
18
18
18
6
1:1
2:1
1:2
2:1
2:1
63
>95
86
68
73
17
18
19
20
18
bonds.11 The Ni-Nacetonitrile bond distances in complexes 2 and
3 are very similar to the corresponding bond lengths seen in
previously studied monocationic Ni-NCCH3 complexes.11,12
Finally, comparing the molecular structure of the neutral
complex 5 to that of the previously reported (POCsp2OPi-Pr)NiBr
analogue5e shows that introducing chloride atoms on the
aromatic core of the ligand causes little or no change in
ligand-metal bond distances and angles.
21 POCsp2OPi-Pr-Cl2 (6) THF
18
18
18
6
1:1
2:1
1:2
2:1
2:1
12
6
10
57
74
22
23
24
25
THF
THF
toluene
toluene
18
a Reaction conditions: 0.007 mmol of Ni complex, 100-200 equiv of
the substrates, 1 mL of solvent, 60 °C. b Yields were determined by GC/
MS and are the average of 3 experiments.
Electrochemical Measurements. The cyclic voltammogram
a 1 mol % loading of catalyst precursors and an aniline:olefin
ratio of 1:1, 1:2, or 2:1. The main product of the catalysis is
3-anilinopropionitrile, which does not form in catalyst-free,
control reactions. Small amounts of a second product were also
detected in some of the runs performed in THF; the molecular
ion of this product suggests that it arises from the addition of
the N-H bond of the main product, 3-anilinopropionitrile, to
acrylonitrile PhN(CH2CH2CN)2 (m/z 199).
of 5 was measured and compared to those of the analogous
i-Pr
Ni-Br complexes based on the PC
P
and POCsp2OPi-Pr
sp2
ligands (Figure 5). This comparison has confirmed the
anticipated order of electron-richness for these complexes:
(PCsp2P -
i-Pr)NiBr5h,6 > (POCsp2OPi-Pr)NiBr5e > (POCsp2OPi-Pr
Cl2)NiBr. Inspection of these voltammograms also shows that
substituting hydrogens in the aromatic core of the ligand by
chlorine atoms has a smaller impact on the electronic density
around the metal than the substitution of carbons by oxygens
in the ligand backbone; the higher electronegativity of oxygen
atoms and their proximity to the metal center are the likely
explanations for these observations.
(13) For a few leading references on metal-catalyzed hydroamination
reactions see: (a) Casalnuovo, A. L.; Calabrese, J. C.; Milstein, D. J. Am.
Chem. Soc. 1988, 110, 6738. (b) Seligson, A. L.; Trogler, W. C.
Organometallics 1993, 12, 744. (c) Brunet, J. J.; Commenges, G.; Neibecker,
D.; Philippot, K. J. Organomet. Chem. 1994, 469, 221. (d) Dorta, R.; Egli,
P.; Zu¨rcher, F.; Togni, A. J. Am. Chem. Soc. 1997, 119, 10857. (e) Beller,
M.; Trauthwein, H.; Eichberger, M.; Breindl, C.; Mu¨ller, T. Eur. J. Inorg.
Chem. 1999, 1121. (f) Tian, S.; Arredondo, V. M.; Stern, C. L.; Marks,
T. J. Organometallics 1999, 18, 2568. (g) Kawatsura, M.; Hartwig, J. F.
J. Am. Chem. Soc. 2000, 122, 9546. (h) Brunet, J. J.; Neibecke, D. In
Catalytic Heterofunctionalization, Togni, A., Gru¨tzmacher, H., Eds.; VCH:
Weinheim, 2001; pp 91-141. (i) Lo¨ber, O.; Kawatsura, M.; Hartwig, J. F.
J. Am. Chem. Soc. 2001, 123, 4366. (j) Ackermann, L.; Bergman, R. G.
Org. Lett. 2002, 4 (9), 1475. (k) Pawlas, J.; Nakao, Y.; Kawatsura, M.;
Hartwig, J. F. J. Am. Chem. Soc. 2002, 124, 3669. (l) Nettekoven, U.;
Hartwig, J. F. J. Am. Chem. Soc. 2002, 124, 1166. (m) Ackermann, L.;
Kaspar, L. T.; Gschrei, C. J. Org. Lett. 2004, 6 (15), 2515. (n) Karshtedt,
D.; Bell, A. T.; Tilley, T. D. J. Am. Chem. Soc. 2005, 127, 12640. (o)
Bexrud, J. A.; Beard, J. D.; Leitch, D. C.; Schafer, L. L. Org. Lett. 2005,
7 (10), 1959. (p) Thomson, R. K.; Bexrud, J. A.; Schafer, L. L.
Organometallics 2006, 25, 4069. (q) Munro-Leighton, C.; Delp, S. A.; Blue,
E. D.; Gunnoe, T. B. Organometallics 2007, 26, 1483, and references
therein. (r) Wood, M. C.; Leitch, D. C.; Yeung, C. S.; Kozak, J. A.; Schafer,
L. L. Angew. Chem., Int. Ed. Engl. 2007, 46, 354. (s) Mu¨ller, T. E.; Beller,
M. Chem. ReV. 1998, 98, 675. (t) Nobis, M.; Drieaˆen-Ho¨lscher, B. Angew.
Chem., Int. Ed. 2001, 40, 3983. For a relevant article on addition of O-H
bonds to activated olefins, see: (u) Miller, K. J.; Kitagawa, T. T.; Abu-
Omar, M. M. Organometallics 2001, 20, 4403–4412. For some precedents
on metal-catalyzed additions of anilines to acrylonitrile, see: (v) Munro-
Leighton, C.; Delp, S. A.; Blue, E. D.; Gunnoe, T. B. Organometallics
2007, 26, 1483. (w) Seul, J. M.; Park, S. Dalton Trans. 2002, 1153.
Hydroamination of Acrylonitrile. Direct addition of N-H
bonds to olefins is an atom-efficient approach toward the
preparation of substituted amines since no byproducts are
formed.13 Although many transition metal complexes are known
to catalyze amination of olefins, very few are commercially
viable in terms of being based on inexpensive metals, operating
at sufficiently low catalyst loadings and temperatures, and
promoting the addition of weakly nucleophilic amines.13t
We have reported5b,f that [(PCsp3 t-Bu)NiL]+ and [(POCsp2OPi-
P
Pr)NiL]+ (L ) acrylonitrile) promote the addition of aniline to
the activated olefin acrylonitrile.13v,w The present report extends
these studies to the cationic acetonitrile complexes discussed
above in order to allow a direct comparison of the catalytic
activities as a function of ligand structure. The catalytic reactions
were performed at 60 °C in THF or toluene for 6 or 18 h, using
(11) Cambridge Structural Database search (Version 5.28 with updates
up to November 2006: Allen, F. H. Acta Crystallogr. 2002, B58, 380).
(12) We cannot include the comparison of the Ni-C bond distance
observed in complex 1 with that of the analogous complex [(PCsp3P
t-Bu)-
Ni(NCCH3)][BPh4] since the highly disordered alkyl chain in 1 required
us to fix some of the distances during the refinement.

Cationic Pincer Complexes of Nickel(II)
Organometallics, Vol. 28, No. 7, 2009 2139
Scheme 2
Scheme 3
the hydroaminated product (path A, Scheme 2). In the hy-
droamination of acrylonitrile, the nitrile moiety might compete
with the olefin moiety for coordination to the electrophilic metal
center, thus making possible the so-called Lewis-acid mecha-
nism (path B, Scheme 2) involving the indirect activation of
the CdC bond for a nucleophilic attack.
In order to obtain mechanistic information for the hy-
droamination reactions promoted by our cationic complexes,
we monitored a typical catalytic experiment by 31P{1H} NMR
spectroscopy using 2 mol % of [(PCsp3P
t-Bu)Ni(NCCHd
As can be noticed from the results listed in Table 3 (runs 1,
6, 11, 16, and 21), complex 3 is by far the most efficient to
catalyze the addition of aniline to acrylonitrile. For reactions
run in THF, varying the amine to olefin ratio from 1:1 to 2:1
gave better yields in all reactions except those catalyzed by
complex 6 (runs 2, 7, 12, and 17 vs run 22), whereas a 1:2
ratio was significantly more beneficial only for reactions
catalyzed by complex 3 (run 18); therefore, the 2:1 ratio was
used for all reactions run in toluene. Overall, the catalysis
proceeds better in toluene relative to THF in all cases except
reactions of complex 3 (runs 5, 10, 15, and 25 vs run 20). Longer
reaction times (18 vs 6 h) gave better yields only for reactions
catalyzed by complexes 1 and 6 (runs 5 vs 4, and 25 vs 24).
Interestingly, reactions run for 18 h and catalyzed by 1, 2, 3,
and 6 gave very similar yields (70-74%), while the reaction
catalyzed by the t-Bu analogue of 1 gave quite low yields (runs
9 and 10, 25%); this can be explained by the greater steric
hindrance of the bulky t-Bu groups.
CH2)][BPh4] and a 2:1 ratio of aniline to acrylonitrile in C6D6
at 80 °C. Throughout the course of this catalytic reaction,
we observed the resonance due to the starting complex (89.4
ppm) in addition to a new singlet very close by (88.2 ppm)
and a third singlet more downfield (95.6 ppm). In an attempt
to isolate and identify these two unknown species, we reacted
[(PCsp3P
t-Bu)Ni(NCCHdCH2)][BPh4] with an excess of aniline
in C6D6 at 80 °C for 16 h. Monitoring this reaction by 31P{1H}
NMR spectroscopy showed the disappearance of the starting
compound and the emergence of a new species displaying a
singlet at ∼88 ppm. This reaction mixture gave some crystals,
which were isolated and analyzed by NMR spectroscopy and
X-ray diffraction. The 31P{1H} NMR spectrum confirmed that
the crystals represented one of the species observed during
the catalytic run (∼88 ppm), whereas crystallography allowed
us to identify this complex as 7 (Scheme 3), the 3-anilino-
propionitrile adduct of the precursor. Unfortunately, we did
not obtain any other evidence that might help identify the
second unknown species observed during the catalysis.
The ORTEP diagram of complex 7 is shown in Figure 6, the
crystal data and collection details are listed in Table 1, and
selected bond distances and angles are given in Table 2. In this
molecular structure, the metal-ligand bonds are quite similar
to the previously reported acrylonitrile adduct bearing the same
ligand.5c The N-C(10) bond is also about the same length in
both complexes (1.139(4) Å in 7 vs 1.144(3) Å for the
acrylonitrile adduct), indicating a similar degree of σ-donation/
π-back-donation. The C(11)-C(12) bond distance is indeed
longer in 7 and is characteristic of a single C-C bond (1.536(4)
Å in 7 vs 1.300(3) Å).
Mechanistic Insights. The most frequently cited mechanistic
proposal for olefin hydroaminations catalyzed by late transition
metal complexes involves nucleophilic attack of the amine to
the coordinated olefin, followed by proton transfer to generate
Conclusion
Structural and reactivity studies have been performed on
different cationic pincer complexes of nickel. The comparison
of the oxidation potentials and solid state structures for
(POCsp2OPi-Pr)NiBr and its dichloro analogue 5, (POCsp2OPi-Pr
-
Cl2)NiBr, the neutral precursors of 3 and 6, respectively, has
shown that the introduction of chlorides on the aromatic moiety
reduces the Ni center’s electron-richness, whereas solid state
Figure 6. ORTEP diagrams for complex 7. Thermal ellipsoids are
shown at the 30% probability level. Hydrogens and t-Bu methyl
groups are omitted for clarity.

2140 Organometallics, Vol. 28, No. 7, 2009
Castonguay et al.
was stirred at room temperature for 2 h. Evaporation of the solvent
and extraction of the solid residues with CH2Cl2 (10 mL) gave a
yellow suspension, which was filtered on a glass frit and evaporated
to give compound 2 as a pale yellow solid (0.665 g, 79%). 1H NMR
parameters such as Ni-C and Ni-P bonds are fairly insensitive
to this substitution. Similarly, reactivity studies have shown that
structural differences have little impact on the catalytic com-
petence of the cationic complexes in promoting the hydroami-
nation of acrylonitrile with aniline, the only major exception
being the inhibiting effect introduced by the t-Bu substituents.
Indeed, it appears that the catalysis is most sensitive to the choice
of solvent, toluene giving the best results for all complexes
except 3. The amine:olefin ratio is also an important factor, 2:1
being the best ratio in most cases. The available data suggest
that the hydroamination reaction probably proceeds via a
mechanism in which the Ni center is acting simply as a Lewis
acid for activating the olefin toward nucleophilic attack. Future
studies will be directed to screening the catalytic activities of
complex 3 for the addition of other nucleophiles.
v
(CDCl3): 0.78 (s, NCCH3, 3H), 1.14 (dvt, JPH ≈ JHH ) 7.0-7.2,
CH(CH3)2, 12H), 1.30 (dvt, vJPH ≈ JHH ) 7.5-8.5, CH(CH3)2, 12H),
3
2.14 (m, CH(CH3)2, 4H), 3.14 (s, CH2P, 4H), 6.88 (t, JHH ) 6.8,
3
BPh4, 4H), 6.80-7.10 (m, ArH, 3H), 7.05 (t, JHH ) 7.4, BPh4,
8H), 7.49 (br s, BPh4, 8H). 13C{1H} NMR (CDCl3): 1.0 (s, NCCH3,
1C), 18.3 (s, CH(CH3)2, 4C), 19.0 (s, CH(CH3)2, 4C), 23.9 (vt, vJPC
v
) 11, CH(CH3)2, 4C), 30.8 (vt, JPC ) 15, CH2P, 2C), 121.8 (s,
v
BPh4, 4C), 123.5 (vt, JPC ) 9, ArH, 2C), 125.8 (s, BPh4, 8C),
127.8 (s, ArH, 1C), 136.2 (s, BPh4, 8C), 152 (vt, vJPC ) 12, ArCH2P,
2C), 164.4 (q, 1JBC ) 49, BPh4, 4C). 13C{1H} NMR (CD2Cl2, 176
2
MHz): 133.0 (s, NCCH3, 1C), 153.0 (t, JPC ) 14, NiC, 1C).
31P{1H} NMR (CDCl3): 70.6. IR (KBr): 2282 cm-1 (νCt N). Anal.
Calcd for C46H58Ni1P2N1B1: C,73.04; H,7.73; N,1.85. Found: C,
72.67; H, 7.68; N, 1.91.
Experimental Section
[{(i-Pr2PO)2C6H3}Ni(NCCH3)][BPh4] (3). CH3CN (5 mL) was
added to a Schlenk tube containing Ni(POCsp2OPi-Pr)Br (0.500 g,
1.04 mmol) and AgBPh4 (0.489 g, 1.15 mmol), and the mixture
was allowed to react for 4 h. The resultant suspension was filtered
in air through a layer of Celite on a glass frit; evaporation of the
solvent gave complex 3 as a yellow solid (0.515 g, 65%). 1H NMR
(CDCl3): 0.65 (s, NCCH3, 3H), 1.30 (br m, CH(CH3)2, 24H,
coincidentally oVerlapped signals), 2.34 (m, CH(CH3)2, 4H), 6.51
(m, ArH, 2H), 6.91 (br s, BPh4, 4H), 7.07 (br s, BPh4, 8H), 7.52
(br s, BPh4 + ArH, 9H). 13C{1H} NMR (CDCl3): 1.0 (s, NCCH3,
1C), 17.0 (s, CH(CH3)2, 4C), 17.6 (s, CH(CH3)2, 4C), 28.6 (vt, vJPC
General Comments. Except where noted, all manipulations were
carried out under a nitrogen atmosphere using standard Schlenk
techniques and/or in a nitrogen-filled glovebox. Solvents were
purified by distillation from appropriate drying agents before use.
All reagents were used as received from commercial vendors.
Literature procedures were used to prepare the nickel precursors
(PCsp3P P
i-Pr)NiBr,5h (PCsp2 i-Pr)NiBr,5h and (POCsp2OPi-Pr)NiBr;5e
AgBPh4 was prepared via the reaction of AgNO3 and NaBPh4 in
H2O, and 3-anilinopropionitrile14 was isolated from a large-scale
nickel-catalyzed reaction of aniline and acrylonitrile. The NMR
spectra were recorded at ambient temperature on Bruker AV400
(1H, 31P{1H}) and Bruker ARX400 (13C{1H}) instruments. The 1H
and 13C{1H} NMR spectra were referenced to solvent resonances,
and spectral assignments were confirmed by DEPT135, COSY, and
HMQC experiments; vJ refers to the apparent coupling constant of
the virtual triplets. The 31P{1H} NMR spectra were referenced to
external 85% H3PO4 (0 ppm). All chemical shifts and coupling
constants are expressed in ppm and Hz, respectively. The IR spectra
v
) 12, CH(CH3)2, 4C), 106.6 (vt, JPC ) 7, ArH, 2C), 121.8 (s,
BPh4, 4C), 125.8 (m, BPh4, 8C), 131.8 (s, ArH, 1C), 136.2 (s, BPh4,
v
8C), 164.4 (1JBC ) 49, BPh4, 4C), 168.8 (vt, JPC ) 9, ArO, 2C).
13C{1H} NMR (CD3CN): 17.0 (s, CH(CH3)2, 4C), 17.8 (s,
CH(CH3)2, 4C), 29.3 (vt, vJPC ) 10, CH(CH3)2, 4C), 107.1 (vt, vJPC
) 5, ArH, 2C), 122.8 (s, BPh4, 4C), 123.4 (very weak m, NiC,
1C), 126.6 (m, BPh4, 8C), 132.6 (s, ArH, 1C), 136.7 (s, BPh4, 8C),
1
v
164.8 (q, JBC ) 39, BPh4, 4C), 170.1 (vt, JPC ) 7, ArO, 2C).
13C{1H} NMR (CD2Cl2, 176 MHz): 122.5 (t, JPC ) 20, NiC, 1C),
128.8 (s, NCCH3, 1C). 31P{1H} NMR (CDCl3 or CD3CN): 191.6.
IR (KBr): 2277 cm-1 (νCt N). Anal. Calcd for C44H54Ni1P2O2N1B1:
C, 69.50; H, 7.16; N, 1.84. Found: C, 69.27; H, 7.46; N, 1.82.
(i-Pr2PO)2C6H2Cl2 (4). To a solution of 2,4-dichloro-1,3-
resorcinol (0.562 g, 3.14 mmol) and DMAP (0.768 g, 6.28 mmol)
in THF (40 mL) that had been stirred for 0.5 h and cooled to 0 °C
was added dropwise i-Pr2PCl (1.00 mL, 6.28 mmol), and the final
reaction mixture allowed to react for 1 h at room temperature.
Evaporation of THF to dryness, followed by addition of hexanes,
stirring, filtration of the resultant suspension, and evaporation of
hexanes gave ligand 4 as a highly water-sensitive oil (0.650 g, 50%);
this material was used immediately after its preparation and without
further purification. 1H NMR (C6D6): 0.93 (dd, JPH ) 16, JHH ) 7,
CH(CH3)2, 12H), 1.13 (dd, JPH ) 11, JHH ) 7, CH(CH3)2, 12H),
1.74 (m, CH(CH3)2, 4H), 7.24 (s, ArH, 1H), 7.80 (t, JPH ) 4, ArH,
1H). 1H{31P} NMR (C6D6): 0.93 (ps t, J ) 7-8, CH(CH3)2, 12H),
1.13 (ps t, J ) 6, CH(CH3)2, 12H), 1.75 (m, CH(CH3)2, 4H), 7.23
(s, ArH, 1H), 7.79 (s, ArH, 1H). 13C{1H} NMR (C6D6): 17.1 (d,
JPC ) 8, CH(CH3)2, 4C), 17.7 (d, JPC ) 20, CH(CH3)2, 4C), 28.6
(d, JPC ) 19, CH(CH3)2 4C), 109.7 (t, JPC ) 22, ArH, 1C), 117.0
(s, ArCl, 2C), 130.5 (s, ArH, 1C), 154.6 (d, JPC ) 10, ArO, 1C).
31P{1H} NMR (C6D6): 156.0.
were recorded on a Perkin-Elmer 1750 FTIR (4000-450 cm-1
)
with samples prepared as KBr pellets. The elemental analyses were
´
performed by the Laboratoire d’Analyze Ele´mentaire (Universite´
de Montre´al).
[{(i-Pr2PCH2CH2)2CH}Ni(NCCH3)][BPh4] (1). CH3CN (10
mL) was added to a Schlenk tube containing (PCsp3P
i-Pr)NiBr (400
mg, 0.90 mmol) and NaBPh4 (341 mg, 1.00 mmol), and the mixture
was stirred at room temperature for 1 h. Evaporation of the solvent
and extraction of the solid residue with CH2Cl2 (10 mL) gave a
yellow suspension, which was filtered on a glass frit and evaporated
to dryness to give compound 1 as a pale yellow solid (554 mg,
1
85%). H NMR (CDCl3): 0.71 (s, NCCH3, 3H), 0.85-1.90 (m,
CH(CH3)2, CH2CH2, NiCH, 33H), 2.03 (m, CH(CH3)2, 2H), 2.13
3
3
(m, CH(CH3)2, 2H), 6.91 (t, JHH ) 7, BPh4, 4H), 7.08 (t, JHH
)
7, BPh4, 8H), 7.50 (br s, BPh4, 8H). 13C{1H} NMR (CDCl3): 1.2
(s, NCCH3, 1C), 17.7 (s, CH(CH3)2, 2C), 18.7 (s, CH(CH3)2, 2C),
v
v
19.3 (vt, JPC ) 3, CH(CH3)2, 2C), 19.4 (vt, JPC ) 2, CH(CH3)2,
2C), 20.4 (vt, vJPC ) 12, CH2P, 2C), 23.3 (vt, vJPC ) 10, CH(CH3)2,
v
v
2C), 25.1 (vt, JPC ) 10 Hz, CH(CH3)2, 2C), 38.2 (vt, JPC ) 8,
2
CH2CH2P, 2C), 54.9 (t, JPC ) 6, NiC, 1C), 121.8 (s, BPh4, 4C),
125.8 (s, BPh4, 8C), 136.1 (s, BPh4, 8C), 164.1 (q, 1JBC ) 49, BPh4,
4C). 13C{1H} NMR (CD2Cl2, 176 MHz): 130.7 (s, NCCH3, 1C).
31P{1H} NMR (CDCl3): 76.5. IR (KBr): 2274 cm-1 (νCt N). Anal.
Calcd for C43H60Ni1P2N1B1: C,71.49; H, 8.37; N,1.94. Found: C,
71.49; H, 8.41; N, 1.96.
{(i-Pr2PO)2C6HCl2}NiBr (5). Ligand 4 (0.460 g, 1.12 mmol)
was added to a suspension of anhydrous NiBr2 (0.278 g, 1.27 mmol)
and DMAP (0.137 g, 1.12 mmol) in toluene (15 mL), and the
reaction mixture was refluxed for 5 h. The solvent was then
evaporated to dryness, hexanes (20 mL) added, and the resultant
mixture filtered in the air on a glass frit. The filtrate was washed
with water and concentrated until a minimum of hexanes was left.
[{(i-Pr2PCH2)2C6H3}Ni(NCCH3)][BPh4] (2). CH3CN (5 mL)
was added to a Schlenk tube containing (PCsp2P
i-Pr)NiBr (0.500 g,
1.05 mmol) and NaBPh4 (0.431 g, 1.26 mmol), and the mixture
(14) For 3-anilinopropionitrile NMR data, see: Li, K.; Horton, P. N.;
Hursthouse, M. B.; Hii, K. K. J. Organomet. Chem. 2003, 665, 250.

Cationic Pincer Complexes of Nickel(II)
Organometallics, Vol. 28, No. 7, 2009 2141
Orange-brown crystals of 5 formed by keeping the solution at -14
°C (0.450 g, 73%). 1H NMR (C6D6): 1.08 (dvt, vJPH ≈ JHH ) 7-8,
temperature, and p-xylene was added (to serve as an internal
standard). Hexanes (5 mL) was then added to the tube. A small
fraction of the resulting suspension/solution was filtered through a
Celite pad, and the filtrate was analyzed by GC/MS. The yields
were determined from a calibration curve based on the product
(anilinopropionitrile/p-xylene).
Cyclic Voltammetry Experiments. Cyclic voltammetry mea-
surements were performed using a BAS Epsilon potentiostat. A
typical three-electrode system was used, consisting of a glassy
carbon working electrode, a Pt auxiliary electrode, and a Ag/AgCl
reference electrode (E1/2(FeCp2+/FeCp2) ) +0.60 V under these
conditions). The experiments were carried out in CH2Cl2 at room
temperature with tetrabutylammonium hexafluorophosphate as
electrolyte (0.1 M), and the solutions were bubbled with nitrogen
before each experiment.
Crystal Structure Determinations. Single crystals of the
complexes were grown by slow diffusion of diethyl ether into a
saturated solution of the complex in CDCl3 (1) or into a saturated
solution of THF (2 and 3) and by slow evaporation (at room
temperature) of a hexanes solution (5) or a C6D6 solution (7). The
crystallographic data (Table 1) for all complexes were collected
on a Nonius FR591 generator (rotating anode) equipped with a
Montel 200, a D8 goniometer, and a Bruker Smart 6000 area
detector.
v
CH(CH3)2, 12H), 1.27 (dvt, JPH ≈ JHH ) 7-9, CH(CH3)2, 12H),
2.14 (m, CH(CH3)2, 4H), 7.07 (s, ArH, 1H). 1H{31P} NMR (C6D6):
1.1 (d, JHH ) 7, CH(CH3)2, 12H), 1.3 (d, J ) 7, CH(CH3)2, 12H),
2.14 (m, CH(CH3)2, 4H), 7.07 (s, ArH, 1H). 13C{1H} NMR (C6D6):
v
16.6 (s, CH(CH3)2, 4C), 17.7 (vt, JPC ) 2, CH(CH3)2, 4C), 28.4
v
v
(vt, JPC ) 11, CH(CH3)2, 4C), 110.8 (vt, JPC ) 7, ArCl, 2C),
128.9 (s, ArH, 1C), 131.4 (t, JPC ) 20, NiC, 1C), 162.3 (vt, vJPC
)
11, ArO, 2C). 31P{1H} NMR (C6D6): 192.2. Anal. Calcd for
C18H29BrNiCl2P2O2: C, 39.39; H, 5.33. Found: C, 39.41; H, 5.20.
[{(i-Pr2PO)2C6HCl2}Ni(NCCH3)][BPh4] (6). CH3CN (10 mL)
was added to a Schlenk tube containing (POCsp2Cl2OPi-Pr)NiBr
(0.450 g, 0.82 mmol) and AgBPh4 (0.419 g, 0.98 mmol), and the
mixture was allowed to react for 15 min at room temperature. The
resultant solution was filtered in air through a layer of Celite on a
glass frit, and the solvent evaporated to dryness to give complex 6
as a pale yellow solid (0.496 g, 73%). 1H NMR (CD3CN):
1.00-1.20 (m, CH(CH3)2, 24H), 2.39 (m, CH(CH3)2, 4H), 6.62 (t,
3
3JHH ) 7, BPh4, 4H), 6.78 (t, JHH ) 7, BPh4, 8H), 6.90-7.10 (s,
BPh4 + ArH, 9H). 13C{1H} NMR (CD3CN): 17.0 (s, CH(CH3)2,
v
4C), 17.7 (s, CH(CH3)2, 4C), 29.5 (vt, JPC ) 11, CH(CH3)2, 4C),
111.7 (vt, vJPC ) 7, ArCl, 2C), 122.7 (s, BPh4, 4C), 126.6 (m, BPh4,
8C), 131.4 (s, ArH, 1C), 136.7 (s, BPh4, 8C), 163.1 (vt, vJPC ) 10,
ArO, 2C), 164.8 (q, 1JBC ) 49, BPh4, 4C). 13C{1H} NMR (CD2Cl2,
Cell refinement and data reduction were done using SAINT.15
An empirical absorption correction, based on the multiple measure-
ments of equivalent reflections, was applied using the program
SADABS.16 The space group was confirmed by XPREP routine17
in the program SHELXTL.18 The structures were solved by direct
methods and refined by full-matrix least-squares and difference
Fourier techniques with SHELX-97.19 All non-hydrogen atoms were
refined with anisotropic displacement parameters. Hydrogen atoms
were set in calculated positions and refined as riding atoms with a
common thermal parameter.
Complete details of the X-ray analyses for complexes 1-3, 5, and
7 have been deposited at The Cambridge Crystallographic Data Centre
(CCDC 691621 (1), 691622 (2), 691623 (3), 691624 (5), 691625 (7)).
These data can be obtained free of charge via www.ccdc.cam.ac.uk/
data_request/cif, or by e-mailing data_request@ccdc.cam.ac.uk, or by
contacting The Cambridge Crystallographic Data Centre, 12 Union
Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
2
176 MHz): 123.7 (t, JPC ) 20, NiC, 1C), 127.7 (s, NCCH3, 1C).
31P{1H} NMR (CD3CN): 197.2. IR (KBr): 2282 cm-1 (νCt N). Anal.
Calcd for C44H52NiCl2P2O2N1B1.H2O: C, 62.37; H, 6.42; N, 1.65.
Found: C, 62.59; H, 6.36; N, 1.72.
[{(t-Bu2PCH2CH2)2CH}Ni(NCCH2CH2NHPh)][BPh4]
Method A. Aniline (20 µL, 0.22 mmol) was added to a Schlenk
tube containing a solution of [(PCsp3
t-Bu)Ni(NCCHdCH2)][BPh4]
(7).
P
(0.010 g, 0.01 mmol) in C6D6 (1 mL). The reaction mixture was
heated at 80 °C for 16 h. 31P{1H} NMR spectroscopy showed the
disappearance of the starting compound and the emergence of a
new species, which was identified as complex 7. Method B.
3-Anilinopropionitrile (0.147 g, 1.00 mmol) was added to a Schlenk
tube containing (PCsp3P
t-Bu)NiBr (0.500 g, 1.00 mmol), AgBPh4
(0.514 g, 1.20 mmol), and CH2Cl2 (20 mL). The mixture was
allowed to react for 10 min at room temperature. The resultant
suspension was then filtered in air through a layer of Celite on a
glass frit, and the solvent evaporated to dryness to give complex 7
as a pale yellow solid, which was fully characterized by NMR
spectroscopy. 1H NMR (CDCl3): 0.80-2.20 (m, PCH2CH2CH, 9H),
Acknowledgment. The authors are grateful to Universite´
de Montre´al (fellowships to A.C.) and to NSERC of Canada
(Discovery and Research Tools and Instruments grants to
D.Z.).
v
v
1.27 (vt, JPH ) 6, C(CH3)3, 18H), 1.32 (vt, JPH ) 6, C(CH3)3,
3
18H), 2.57 (m, CH2, 2H), 2.98 (t, JHH ) 7, CH2, 2H), 6.33 (d,
3JHH ) 7, ArH, 2H), 6.74 (t, JHH ) 7, ArH, 1H), 6.91 (t, JHH
)
3
3
7, BPh4, 4H), 7.05 (t, 3JHH ) 7, BPh4, 8H), 7.13 (t, 3JHH ) 7, ArH,
2H), 7.48 (br s, BPh4, 8H). 13C{1H} NMR (CDCl3): 18.7 (s, CH2,
Supporting Information Available: Complete details of the
X-ray analyses for complexes 1-3, 5, and 7 are available free of
charge via the Internet at http://pubs.acs.org.
v
1C), 22.3 (vt, JPC ) 11, CH2P, 2C), 29.3 (s, C(CH3)3, 6C), 29.6
(s, C(CH3)3, 6C), 34.9 (vt, vJPC ) 7, C(CH3)3, 2C), 36.2 (vt, vJPC
)
v
OM800840U
6, C(CH3)3, 2C), 38.5 (s, CH2, 1C), 39.0 (vt, JPC ) 8, CH2CH2P,
2
2C), 54.1 (t, JPC ) 6, NiC, 1C), 113.2 (s, ArH, 2C), 118.6 (s,
ArH, 1C), 121.9 (s, BPh4, 4C), 125.8 (s, BPh4, 8C), 129.3 (s, ArH,
2C), 133.7 (weak s, NC, 1C), 136.2 (s, BPh4, 8C), 146.4 (s, ArN,
(15) SAINT, Release 6.06; Integration Software for Single Crystal Data;
Bruker AXS Inc.: Madison, WI, 1999.
(16) Sheldrick, G. M. SADABS, Bruker Area Detector Absorption
Corrections; Bruker AXS Inc.: Madison, WI, 1999.
(17) XPREPRelease 5.10, X-ray Data Preparation and Reciprocal Space
Exploration Program; Bruker AXS Inc.: Madison, WI, 1997.
(18) SHELXTLRelease 5.10, The Complete Software Package for Single
Crystal Structure Determination; Bruker AXS Inc.: Madison, WI, 1997.
(19) (a) Sheldrick, G. M. SHELXS97, Program for the Solution of Crystal
Structures; Univ. of Gottingen: Germany, 1997. (b) Sheldrick, G. M.
SHELXL97, Program for the Refinement of Crystal Structures; University
of Gottingen: Germany, 1997.
1
1C), 164.1 (q, JBC ) 49, BPh4, 4C). 31P{1H} NMR (C6D6 or
CDCl3): 88.2. Anal. Calcd for C54H75NiP2N2B1 · H2O: C, 71.93; H,
8.61; N, 3.11. Found: C, 71.65; H, 8.46; N, 3.20.
Typical Procedure for Hydroamination Reactions. Aniline (63
µL, 0.69 mmol), acrylonitrile (46 µL, 0.70 mmol), and the catalyst
stock solution (1.0 mL of a 6.9 mM THF solution) were added
into a sealable vessel, which was put in an oil bath at 60 °C for 6
or 18 h. The reaction vessel was then allowed to cool to room