C-CN bond activation of aromatic nitriles and fluxionality of the η2-arene intermediates: Experimental and theoretical investigations

Article abstract of DOI:10.1021/om100001m

[Ni(dippe)H]₂ has been reacted with a variety of aromatic nitriles. Both experimental and DFT calculation results have shown that an η²-arene complex with nickel coordinated to the C=C double bond next to the cyano substituent is the crucial intermediate leading to C-CN bond activation. Furthermore, the fluxional processes of the η²-arene species were investigated by low-temperature experiments as well as computational methods. In the case of dicyanobenzenes, a mechanism similar to that found for PhCN was found with the Ni(dippe) fragment rotating as it migrated around the phenyl ring through a series of η³-allyl-like transition states. For polycyclic aromatic nitriles, only certain η²-arenes were stable enough to contribute to the fluxional process, and nickel migrates via an η⁴-coordinated transition state. The transition states connecting the η²-nitrile complex to the η²-arene intermediate and the η²-arene intermediate to the C-CN bond activation products are at much higher energies compared to those for migration around the ring. In the reaction of 9-cyanoanthracene, the instability of the η²-arene precursor and the high-energy activation barrier resulted in the absence of the C-CN oxidative addition product. The complex with 9-cyanophenanthrene undergoes only C-CN cleavage upon photolysis.

Full text of DOI:10.1021/om100001m

2430 Organometallics 2010, 29, 2430–2445
DOI: 10.1021/om100001m
C-CN Bond Activation of Aromatic Nitriles and Fluxionality of the
η2-Arene Intermediates: Experimental and Theoretical Investigations
Ting Li,† Juventino J. Garcı
´
a,‡ William W. Brennessel,† and William D. Jones*,†
†
‡
Department of Chemistry, University of Rochester, Rochester, New York 14627, and Facultad de Quımica,
ꢀ ꢀ ꢀ ꢀ
Universidad Nacional Autonoma de Mexico, Mexico City, Mexico D. F. 04510
´
Received January 1, 2010
[Ni(dippe)H]2 has been reacted with a variety of aromatic nitriles. Both experimental and DFT
calculation results have shown that an η2-arene complex with nickel coordinated to the CdC double bond
next to the cyano substituent is the crucial intermediate leading to C-CN bond activation. Furthermore,
the fluxional processes of the η2-arene species were investigated by low-temperature experiments as well as
computational methods. In the case of dicyanobenzenes, a mechanism similar to that found for PhCN
was found with the Ni(dippe) fragment rotating as it migrated around the phenyl ring through a series of
η3-allyl-like transition states. For polycyclic aromatic nitriles, only certain η2-arenes were stable enough to
contribute to the fluxional process, and nickel migrates via an η4-coordinated transition state. The
transition states connecting the η2-nitrile complex to the η2-arene intermediate and the η2-arene
intermediate to the C-CN bond activation products are at much higher energies compared to those
for migration around the ring. In the reaction of 9-cyanoanthracene, the instability of the η2-arene
precursor and the high-energy activation barrier resulted in the absence of the C-CN oxidative addition
product. The complex with 9-cyanophenanthrene undergoes only C-CN cleavage upon photolysis.
Introduction
[(dippe)Ni0] fragment. For example, C-C and C-S bond
cleavage is seen in a variety of biphenylene and thiophene
substrates.4,5 Our group has also investigated the reaction of
aromatic nitriles using this dimer.6 Recent results of reac-
tions with benzonitrile showed that while initial coordina-
tion of nickel produces an η2-C,N-nitrile adduct, a higher
energy η2-arene intermediate was formed prior to C-C bond
cleavage (eq 1). The fluxionality of the η2-arene complex was
demonstrated both experimentally and computationally.7
The cleavage of carbon-carbon σ-bonds has important
applications in both organic synthesis and industrial pro-
cesses.1 However, due to the kinetic inertness and thermo-
dynamic stability of these bonds, this type of activation
remains a continuing challenge in organometallic chemistry,
especially in substrates without relief of strain or aromatiza-
tion providing a substantial extra driving force.2 Among the
exceptions, several examples of C-C bond activations in aryl
cyanides by transition metals have been reported.3
The hydride-bridged nickel dimer [Ni(dippe)(μ-H)]2, in the
presence of a suitable ligand, releases H2 gas to generate
a product resulting from reaction with the electron-rich
*Corresponding author. E-mail: jones@chem.rochester.edu.
(1) (a) Crabtree, R. H. Chem. Rev. 1985, 85, 245. (b) Miller, J. A.
Tethrahedron Lett. 2001, 42, 6991. (c) Bruce, M. I.; Shelton, B. W.; White,
A. H.; Zaitzeva, N. N. J. Chem. Soc. Dalton Trans. 2001, 3627. (d) Dyker,
G. Angew. Chem. 1999, 111, 1808. (e) Dyker, G. Angew. Chem., Int. Ed.
1999, 38, 1698.
(2) (a) Murakami, M.; Ito, Y. In Topics in Organometallic Chemistry;
Murai, S., Ed.; Springer-Verlag: New York, 1999; pp 97-129. (b) Rybtchinski,
B.; Milstein, M. Angew. Chem., Int. Ed. 1999, 38, 870. (c) Perthuisot, C.;
Edelbach, B. L.; Zubris, D. L.; Simhai, N.; Iverson, C. N.; Muller, C.; Satoh, T.;
Jones, W. D. J. Mol. Catal. A 2002, 189, 157.
In this paper, we report reactions of a variety of aromatic
nitriles with [Ni(dippe)H]2 at ambient and low temperatures.
DFT methods, using [Ni(dmpe)] as a model for [Ni(dippe)],
(4) Edelbach, B. L.; Vicic, D. A.; Lachicotte, R. J.; Jones, W. D.
Organometallics 1998, 17, 4784. Edelbach, B. L.; Lachicotte, R. J.; Jones,
W. D. Organometallics 1999, 18, 4040. Perthuisot, C; Edelbach, B. L.;
Zubris, D. L.; Simhai, N.; Iverson, C. N.; M€uller, C.; Satoh, T.; Jones, W. D. J.
Mol. Catal. A, Chem. 2002, 189, 157–168. M€uller, C.; Lachicotte, R. J.;
Jones, W. D. Organometallics 2002, 21, 1975.
(3) (a) Abla, M.; Yamamoto, T. J. Organomet. Chem. 1997, 532, 267.
(b) Morvillo, A.; Turco, A. J. Organomet. Chem. 1981, 208, 103. (c)
Parshall, G. W. J. Am. Chem. Soc. 1974, 96, 2360. (d) Gerlach, D. H.;
Kane, A. R.; Parshall, G. W.; Jesson, J. P.; Muetterties, E. L. J. Am. Chem.
Soc. 1971, 93, 3543. (e) Liu, Q.-X.; Xu, F.-B.; Li, Q.-S.; Song, H.-B.; Zhang,
Z.-Z. Organometallics 2004, 23, 610. (f) Ozawa, F.; Iri, K.; Yamamoto, A.
Chem. Lett. 1982, 1707. (g) Adam, R.; Villiers, C.; Ephritikhine, M.; Lance,
M.; Nierlich, M.; Vigner, J. J. Organomet. Chem. 1993, 445, 99. (h) Nakao,
Y.; Oda, S.; Hiyama, T. J. Am. Chem. Soc. 2004, 126, 13904. (i) Nakazawa,
H.; Itazaki, M.; Kamata, K.; Ueda, K. Chem. Asian J. 2007, 2, 882.
(5) Vicic, D. A.; Jones, W. D. J. Am. Chem. Soc. 1997, 119, 10855.
Vicic, D. A.; Jones, W. D. Organometallics 1998, 17, 3411. Vicic, D. A.;
Jones, W. D. J. Am. Chem. Soc. 1999, 121, 7606.
ꢀ
(6) (a) Garcia, J. J.; Arevalo, A.; Brunkan, N. M.; Jones, W. D.
Organometallics 2004, 23, 3997. (b) Garcia, J. J.; Brunkan, N. M.; Jones, W.
D. J. Am. Chem. Soc. 2002, 124, 9547. (c) Garcia, J. J.; Jones, W. D.
Organometallics 2000, 19, 5544.
(7) For a comparison of the [Ni(dmpe)] vs [Ni(dippe)] models, see:
Ates-in, T. A.; Li, T.; Lachaize, S.; Garcı
´
metallics 2008, 27, 3811.
a, J. J.; Jones, W. D. Organo-
r
pubs.acs.org/Organometallics
Published on Web 05/12/2010
2010 American Chemical Society

Article
Organometallics, Vol. 29, No. 11, 2010 2431
spectrum, assigned to the ortho and meta protons of the η2-C,C
adduct. These observations suggest rapid equilibrations of iso-
mers A2, A3, A4, andA5 (eq3). Asthe temperature ofthesample
increased to -20 °C, the η2-arene complexes completely disap-
peared, leaving only A1. When the temperature reached 60 °C, a
new set of doublets appeared in the 31P{1H} spectrum that
belonged to the C-CN activation product A6. When the mixture
was cooled back to room temperature, none of the η2-arene
complexes were observed to reappear in the NMR spectrum
(Supporting Information, Figure SI-1).
Figure 1. ORTEP drawing of [Ni(dippe)H]2. Ellipsoids are
shown at the 50% probability level. Selected bond lengths (A):
Ni(1)-Ni(1)A, 2.3737(5); Ni(1)-H(1), 1.64(6); Ni(1)-H(2),
1.51(7); Ni(1)-P(1), 2.1291(6); Ni(1)-P(2), 2.1212(6). Selected
angles (deg): P(1)-Ni(1)-P(2), 91.78(2); P(2)-Ni(1)-Ni(1)A,
136.28(2); P(2)-Ni(1)-H(1), 106(2); H(1)-Ni(1)-H(2), 76(3).
were undertaken to examine the energetics, intermediates,
and reaction pathways of the C-CN bond activation. Again,
it was found that formation of an η2-arene complex is crucial
prior to C-C bond cleavage. This complex is fluxional and
can exist as a stable species in reactions with polycyclic
aromatic nitriles. The transition states leading to C-CN
oxidative addition products showed very similar geometries
to that seen for PhCN,7 but an additional fluxional pathway
has been identified.
Upon adding a second equivalent of [Ni(dippe)H]2 to A1,
a new pair of broad doublets appeared in the 31P{1H} NMR
spectrum (C6D6) at δ 62.0 and 72.5 (JP-P = 70 Hz), which
was assigned to a bis-η2-nitrile complex (A7).6b After sitting
at room temperature for 1 h, a new species (A8) appeared
in the 31P{1H} NMR spectrum with characteristics of two
different Ni centers, each displaying a pair of doublets, both
Ni(II) (δ 63.4 and 77.5, JP-P = 25 Hz) and Ni(0) (δ 63.1 and
74.5, JP-P = 71 Hz) within the same molecule, indicating
only one C-CN bond in A7 was cleaved (eq 4). About 50%
A6 was also observed. Single-crystal structures of A6 and A8
were obtained as shown in Figure 2.
Results and Discussion
Structure of the [Ni(dippe)H]2 Complex. The red dimer
[Ni(dippe)H]2 is readily prepared from the reaction of Ni-
(dippe)Cl2 and LiHBEt3.8 Recrystallization from hexanes
allowed the X-ray structure of the nickel dimer to be
obtained (Figure 1). At each Ni center, two P atoms and
one bridging H atom are essentially planar, with the second
bridging H atom out of the plane. The twist angle between the
P1-Ni1-P2 and P1A-Ni1A-P2Aplanesis80° and compares
with values of 80° in [Ni(dtbpe)H]2,9 63° in [Ni(dcypp)H]2,10 and
75° in [Ni(dippp)H]2.11 The angle between the Ni1-H1-Ni1A
and Ni1-H2-Ni1A planes is approximately 156°. The distance
between the two Ni atoms is 2.37 A, indicating the presence of a
Ni-Ni bond between the two formally NiI centers. The NiI-NiI
distances in the other hydride dimers average 2.44 A.
Reactions with Dicyanobenzenes. Thereactionof[Ni(dippe)H]2
with 1,2-dicyanobenzene at -60 °C initially formed both
η2-nitrile (A1) andη2-arene complexes (eq 2, A2-A5). Themajor
product A1 showed a pair of doublets in the 31P{1H} NMR
spectrum at δ 62.7 and 73.5 (JP-P = 62 Hz). The minor product
showed a singlet at δ57.0 in the 31P{1H} NMR spectrum and two
broad upfield peaks at δ 5.83 (2H) and 6.28 (2H) in the 1HNMR
A computational study was undertaken to examine the
fluxionality of the η2-arene complexes and the pathway
leading to the C-CN oxidative addition product. The
[Ni(dmpe)] fragment was used as a model of the active
species [Ni(dippe)] in the experiment.12 Initially the ground
(8) Vicic, D. A.; Jones, W. D. J. Am. Chem. Soc. 1997, 119, 10855.
Compare to [Ni(dcype)H]2: Jonas, K.; Wilke, G. Angew. Chem., Int. Ed.
Engl. 1970, 9, 312.
(9) Bach, I.; Goddard, R.; Kopiske, C.; Seevogel, K.; Porschke, K.-R.
Organometallics 1999, 18, 10.
(10) Barnett, B. L.; Kruger, C.; Tsay, Y. H.; Summerville, R. H.;
€
Hoffmann, R. Chem. Ber. 1977, 110, 3900.
(11) Fryzuk, M. D.; Clentsmith, G. K. B.; Leznoff, D. B.; Rettig, S. J.;
Geib, S. J. Inorg. Chim. Acta 1997, 265, 169.
(12) Atesin, T. A.; Li, T.; Jones, W. D. J. Am. Chem. Soc. 2007, 129,
7562.

2432 Organometallics, Vol. 29, No. 11, 2010
Li et al.
Figure 2. ORTEP drawing of (a) (dippe)Ni(CN)(C6H4CN) (A6). Ellipsoids are shown at the 50% probability level. Selected bond
lengths (A): Ni(1)-C(8), 1.863(4); Ni(1)-C(1), 1.911(4); Ni(1)-P(1), 2.1915(12); Ni(1)-P(2), 2.1815(12); C(7)-N(1), 1.145(5);
C(7)-C(2), 1.442(6); C(8)-N(2), 1.144(5). Selected angles (deg): P(1)-Ni(1)-P(2), 88.64(4); C(1)-Ni(1)-C(8), 88.42(16); N(2)-
C(8)-Ni(1), 177.7(4); C(7)-C(2)-C(1), 119.4(3); N(1)-C(7)-C(2), 178.3(4). (b) (dippe)Ni(μ-NCPh)Ni(CN)(dippe) (A8). Ellipsoids
are shown at the 50% probability level. Selected bond lengths (A): Ni(1)-C(7), 1.869(3); Ni(1)-N(1), 1.913(2); Ni(1)-P(1), 2.1673(9);
Ni(1)-P(2), 2.1396(8); C(7)-N(1), 1.230(3); C(7)-C(1), 1.464(4); Ni(2)-C(2), 1.933(3); Ni(2)-C(8), 1.861(3); Ni(2)-P(3), 2.1924(8);
Ni(2)-P(4), 2.1653(8); C(8)-N(2), 1.157(3). Selected angles (deg): P(1)-Ni(1)-P(2), 91.32(3); C(7)-Ni(1)-N(1), 37.93(10); C(7)-
N(1)-Ni(1), 69.14(16); C(7)-C(1)-C(2), 119.2(2); C(1)-C(2)-Ni(2), 118.50(19); C(2)-Ni(2)-C(8), 88.59(11); N(2)-C(8)-Ni(2),
173.4(2); P(3)-Ni(2)-P(4), 87.98(3).
Figure 3. Energetics of C-C bond activation of 1,2-dicyanobenzene by [Ni(dmpe)] (free energies in kcal mol-1) relative to the total
energies of fragments ([Ni(dmpe)] and 1,2-dicyanobenzene) (PCM corrected in THF).
states were constructed on the basis of previously reported
X-ray structures for Ni(dippe)(η2-NCPh) and Ni(dippe)-
(Ph)(CN).6c Local minima for all the species were located
on the potential energy surface in the gas phase, and all the
optimized structures and selected bond lengths are summar-
ized in the Supporting Information (Figure 3, SI-17, and
Table SI-1).
surface scan by constraining the Ni-Cipso distance in SA1
to shorten and optimizing the resulting structures as the
Ni-Cipso distance was reduced. The structure around the
energy maximum was optimized as a transition state. The
intrinsic reaction coordinate calculation (IRC) starting from
this transition state leads to SA1 in one direction and the
η2-arene complex SA2 in the other, where the nickel atom is
coordinated through the CdC between the two nitrile sub-
stituents. In TSA12, nickel coordinates to the nitrile carbon
(Ni-CN = 2.04 A) and weakly through its nitrogen and aryl
carbon atoms (Ni-N = 2.33 A, Ni-Cipso = 2.30 A). The
Ni-C-C plane is at an angle of 61.5° to the P-Ni-P plane.
The transition state (TSA26) leading to the formation of the
oxidative addition product SA6 was located by a relaxed
potential energy surface scan by constraining the Ni-CN
distance in SA2 to shorten and optimizing the resul-
ting structures as the distance was reduced. IRC following
In the Ni(dmpe)(η2-C,N-nitrile) complex SA1, the coordi-
nated C-N bond is longer than that in free 1,2-dicyanoben-
zene (1.23 A vs 1.16 A), and the C-C-N angle bends to
138.8°. The coordination around nickel is almost planar,
with the angle between the P-Ni-P and the C-N-Ni
planes being only 2.9°. The phenyl group is also coplanar
with the Ni-N-C plane. The C-CN oxidative addition
product SA6 has a square-planar geometry around the nickel
center, and the phenyl ring is perpendicular to the P-Ni-P
plane. TSA12 was located from a relaxed potential energy

Article
Organometallics, Vol. 29, No. 11, 2010 2433
protons. When the temperature was raised to -30 °C, the
resonances of the η2-arene complexes disappeared (see Sup-
porting Information, Figure SI-2). Upon heating, a new
complex appeared in the 31P{1H} NMR spectrum (δ 70.8
and 82.5, JP-P = 26 Hz), corresponding to the C-CN
cleavage product B5. After heating at 60 °C for 13 h,
B1-B4 completely converted to B5. A single-crystal struc-
ture of B5 was obtained and is shown in Figure 4.
Figure 4. ORTEP drawing of (dippe)Ni(3-cyanophenyl)(CN)
(B5). Ellipsoids are shown at the 50% probability level. Selected
bond lengths (A): Ni(1)-C(8), 1.890(2); Ni(1)-C(1), 1.927(2);
Ni(1)-P(1), 2.1815(6); Ni(1)-P(2), 2.1863(6); C(7)-N(1),1.153(3);
C(8)-N(2), 1.112(3); Selected angles (deg): P(1)-Ni(1)-P(2),
89.02(2); C(8)-Ni(1)-C(1), 88.67(8); N(2)-C(8)-Ni(1), 178.3(2).
demonstrated that TSA26 connected SA6 to the η2-arene
complex SA2. In TSA26, the Ni-CN bond is 0.12 A longer
than in SA6, while the C-CN distance is lengthened only by
0.04 A. The C-C-N angle is 146.6°, much smaller than in
SA2 (176.6°). Also, the Ni-C-N plane rotates at an angle of
38.5° to the P-Ni-P plane (see weo’s for TSA12 and TSA26
in the Supporting Information). Therefore, TSA26 can be
viewed as having essentially formed the Ni-CN bond while
only slightly breaking the C-CN bond and is well-pro-
gressed toward the nickel(II) square-planar product.
SA2 therefore is established as the immediate precursor of
the C-CN activation. Four stable, high-energy η2-arene
complexes, SA2, SA3, SA4, and SA5, have been located on
the potential energy surface. All of them have nickel metal
bound to the phenyl ring through one of the CdC double
bonds. The nickel-carbon bond lengths are very similar, and
the angle between the plane of the phenyl ring and the
P-Ni-P plane is 64.9° in SA2, 69.3° in SA3, 73.3° in SA4,
and 78.9° in SA5. The transition states connecting these
η2-arene complexes (TSA23, TSA34, TSA45) all show an
η3-allyl-like structure with the allyl perpendicular to the
P-Ni-P plane, and they are located at much lower energies
than TSA12 or TSA26. The low kinetic barriers for the
migration of the nickel around the phenyl ring prevent the
detection of the different η2-arene species in the NMR
spectrum even at -60 °C. The NiP2 unit rotates as it migrates
around the aromatic ring, and the two phosphorus environ-
ments exchange with each other when the nickel returns to
the starting position (see movie in Supporting Information).
These result in one singlet being observed in the 31P{1H}
NMR spectrum for the η2-arene complexes, in contrast to
what was seen for the η2-C,C-benzonitrile complex (two
doublets in the 31P{1H} spectrum at low T).7
Similar to 1,2-dicyanobenzene, adding another equivalent
of [Ni(dippe)H]2 to B1 at room temperature led to the bis-
η2-nitrile species B6, with a pair of sharp doublets in the
=
68 Hz). The corresponding resonances in the 1H NMR
spectrum indicated Cs symmetry in B6, with one meta-H
31P{1H} NMR spectrum (C6D6, δ 63.0 and 75.2, JP-P
(δ 7.24, t, J = 8 Hz, 1H), two ortho-H (δ 7.99, d, JH-H
=
6 Hz, 2 H), and one ortho-H between the two cyano substi-
tuents (δ 8.79, s, 1H). Upon heating, one of the two C-CN
bonds was cleaved, leading to product B7 (eq 7). B7 has two
pairs of doublets in the 31P{1H} NMR spectrum (C6D6,
δ 63.2 and 75.3, JP-P = 68 Hz; δ 67.3 and 76.0, JP-P
17 Hz), again indicating the presence of both Ni(0) and Ni(II)
=
coordination centers in the same molecule.
[Ni(dippe)H]2 was also reacted with 1,3-dicyanobenzene
at -60 °C, and observations were made that differed slightly
from those seen with 1,2-dicyanobenzene (eq 5). Two pairs of
doublets were observed in the 31P{1H} NMR spectrum. The
major pair at δ 64.8 and 76.4 (JP-P = 62 Hz) belonged to the
η2-nitrile complex B1, and the minor pair at δ 57.0 and 61.4
(JP-P = 74 Hz) was assigned to the fluxional η2-C,C-arene
complexes B2-B4 (eq 6). One set of upfield peaks was seen in
the corresponding 1H NMR spectrum for the aromatic
Results from the computational study are summarized in
Figure 5. Again, the η2-arene complex SB2 lies at the center
of the C-CN activation pathway. There are two different
transition states located on the potential energy surface. One
is TSB12, which connects the η2-nitrile complex SB1 and
SB2, and the other is TSB25, which connects SB2 and the
oxidative addition product SB5. The three η2-arene com-
plexes SB2, SB3, and SB4 have comparable energies and can
equilibrate through a series of η3-allyl-like transition states

2434 Organometallics, Vol. 29, No. 11, 2010
Li et al.
Figure 5. Energetics of C-C bond activation of 1,3-dicyanobenzene by [Ni(dmpe)] (free energies in kcal mol-1) relative to the total
energies of fragments ([Ni(dmpe)] and 1,3-dicyanobenzene) (PCM corrected in THF).
Figure 6. Energetics of C-C bond activation of 1,4-dicyanobenzene by [Ni(dmpe)] (free energies in kcal mol-1) relative to the total
energies of fragments ([Ni(dmpe)] and 1,4-dicyanobenzene) (PCM corrected in THF).
(TSB22, TSB23, TSB34, and TSB44). The barriers for nickel
metal migration around the phenyl ring are much lower than
the barrier for C-CN activation; thus the η2-arene com-
plexes are again fluxional. SB2, SB3, and SB4 are much less
stable than SB1 or SB5, which explains the disappearance of
the η2-arene resonances upon heating. In contrast to 1,2-
dicyanobenzene, the rotational migration of the [Ni(dippe)]
fragment preserves the distinct phosphorus environments
(see weo in Supporting Information). Instead of a singlet as
seen for A2-A5, two sharp doublets were observed in the
31P{1H} NMR spectrum for B2-B4. The fluxional behavior
and 31P{1H} spectrum of B2-B4 are similar to those seen
with benzonitrile.7
the 1H NMR spectrum, assigned to the η2-nitrile complex
C1 (eq 8). The singlet for the aryl protons was possibly due
to accidental degeneracy of the chemically distinct pro-
tons. The minor doublets at δ 55.9 and 60.1 (JP-P = 71 Hz)
in the 31P{1H} NMR spectrum and the slightly broad
upfield singlet at δ 5.9 in the 1H NMR spectrum were
assigned to the equilibrating η2-arene complexes C2 and
C20 (eq 9). The observation of two doublets in the 31P{1H}
spectrum of C2/C20 was surprising, as the rotational
migration of the [Ni(dippe)] unit was expected to equili-
brate the phosphorus nuclei via a symmetrical η2-C,C
intermediate. These resonances disappeared from the
NMR spectrum when the mixture was warmed to 0 °C
(see Supporting Information, Figure SI-3). C-CN activa-
tion occurred upon heating, leading to the Ni(II) species
C3. C1 can also react with another equivalent of [Ni-
(dippe)H]2 to form a bis-η2-nitrile compound C4, which
undergoes oxidative addition reaction. The formation and
The reaction of [Ni(dippe)H]2 with 1,4-dicyanobenzene
at low temperature initially formed two Ni(0) species. At
-60 °C, the major product showed one pair of doublets
in the 31P{1H} NMR spectrum (δ 62.8 and 74.5, JP-P
=
62 Hz), with a single corresponding resonance at δ 7.8 in

Article
Organometallics, Vol. 29, No. 11, 2010 2435
Scheme 1. Reactions of [(dippe)NiH]2 with 1-Cyanonaphthalene, 2-Cyanonaphthalene, 1-Cyano-4-methylnaphthalene, and 1,4-Dicya-
nonaphthalene
single-crystal structures of C1, C3, and C4 were described
in an earlier report.6b
Figure 7. ORTEP drawing of (dippe)Ni(C10H7)(CN) (D13).
Ellipsoids are shown at the 50% probability level. Selected bond
lengths (A): Ni(1)-C(1), 1.872(4); Ni(1)-C(2), 1.953(5); Ni(1)-
P(1), 2.1949(12); Ni(1)-P(2), 2.1805(11); C(1)-N(1), 1.138(5).
Selected angles (deg): P(1)-Ni(1)-P(2), 87.48(4); C(2)-Ni(1)-
C(1), 89.27(18); N(2)-C(8)-Ni(1), 175.3(4).
The results from DFT calculations (Figure 6) show that the
η2-arene complex SC2 is connected to the η2-nitrile SC1 by
transition state TSC12 and to the oxidative addition product
SC3 by another transition state, TSC23, as with the other
dicyanobenzenes. TSC12 and TSC23 have structures similar
to TSA12 and TSA25. In calculating the fluxional process, if the
nickel migrated via η3-allyl-like transition states as before, it
would equilibrate the two phosphorus environments as nickel
moves from one cyano-substituted double bond to the other (see
Supporting Information weo). This pathway includes another
η2-arene complex with an energy higher than SC2 by 3.3 kcal
mol-1, in which nickel coordinates to the central double bond
and has a fluxional barrier of 12 kcal mol-1 (see FigureSI-4). As
this pathway is in contradiction with the observed phosphorus
data, another migration mode was modeled in which nickel
migrates between C2 and C20 via a single η4-coordinated
transition state, TS220_2 (eq 9). This migration pathway has a
lower energy barrier and does not equilibrate the phosphorus
environments. (Figure 6 and weo in Supporting Information).
The change from [1,2] to [1,3] shifts around the ring can be
attributed to the preference for binding to a double bond
substituted with a cyano group.
For the dicyanobenzenes, the C-CN bond cleavage still
occurs in the same way as with benzonitrile, i.e., via an η2-C,
C adduct. For the fluxional η2-arene intermediates, however,
the migration mode of nickel metal varies from η2 f [η3]q f
η2 to η2 f [η4]q f η2 and results in different behaviors in the
low-T 31P NMR spectra.
Reaction with Cyanonaphthalenes and Derivatives. To
compare the reactivity of polycyclic aromatic nitriles for

2436 Organometallics, Vol. 29, No. 11, 2010
Li et al.
Figure 8. Energetics of C-C bond activation of 1-cyanonaphthalene by [Ni(dmpe)] (free energies in kcal mol-1) relative to the total
energies of fragments ([Ni(dmpe)] and 1-cyanonaphthalene) (PCM corrected in THF).
square planar, and the naphthalene ring is almost perpendi-
cular to the nickel square plane (86.8°).
A DFT calculation was conducted in order to investigate
the C-CN activation pathway (Figure 8). Both the η2-nitrile
complex (SD1) and the oxidative addition product (SD13) were
optimized as ground states. The potential energy surface scan
from SD1 leads to the transition state TSD13, with similar
coordination geometry to that seen in the dicyanobenzenes
(TSA12, TSB12, and TSC12). Another transition state,
TSD313, was located by a potential energy surface scan starting
from SD13. The IRC calculations from TSD13 and TSD313 both
led to the η2-arene species SD3, with nickel coordinated to the
C1-C2 double bond. Ten other possible η2-arene complexes were
modeled (SD2, SD4-12) (Figure 8). On the basis of the energies,
only two isomers, SD3 and SD5, are stable enough to be observed
in the experiment. There can be a fast equilibration between SD3
and SD5 (eq10) viatheη4-arene transition state TSD35 with a low
kinetic barrier of about 7 kcal/mol. While the fluxional process
results in a shift of all three proton resonances upfield, it does
not render equivalent the two phosphorus environments (see
Supporting Information for weo), consistent with the observa-
tion of two doublets at ambient temperature in the 31P{1H} NMR
spectrum. A similar rearrangement via an η4-transition state was
proposed for the complexes Ni(dippe)(η2-naphthalene)13 and
Figure 9. ORTEP drawing of (dippe)Ni(C10H7)(CN) (E13). Ellip-
soids are shown at the 50% probability level. Selected bond lengths
(A): Ni(1)-C(1), 1.8779(16); Ni(1)-C(3), 1.922(5); Ni(1)-P(1),
2.2018(4); Ni(1)-P(2), 2.1809(4); C(1)-N(1), 1.139(2). Selected
angles (deg): P(1)-Ni(1)-P(2), 88.919(15); C(3)-Ni(1)-C(1),
86.3(2); N(2)-C(8)-Ni(1), 178.76(16).
C-CN bond activation, [Ni(dippe)H]2 was reacted with
cyanonaphthalenes and derivatives. The reaction with 1-cy-
anonaphthalene at ambient temperature gave a mixture of
two Ni(0) species (Scheme 1). In the 31P{1H} NMR spec-
trum, one had features of the η2-nitrile complex (D1), with
two doublets at δ 62.0 and 73.8 (JP-P = 65 Hz). The other
showed two inequivalent resonances (δ 57.4 and 60.7,
JP-P = 61 Hz) with three corresponding upfield resonances
Ni(PBun ) (η2-anthracene).14
3 2
1
in the H spectrum at δ 4.66, 5.93, and 6.15, implying the
coordination of nickel to the substituted ring. Unlike the
η2-arene species of the dicyanobenzenes, the latter complex is
relatively stable. Upon heating or standing at room tem-
perature, these two Ni(0) complexes slowly converted into
a new product, D13, which displayed two sharp doublets in
the 31P{1H} NMR spectrum with JP-P = 20 Hz and was
formulated as the C-CN bond oxidative addition product
(dippe)Ni(CN)(1-naphthyl) (see Figures SI-5 and SI-6). A
single-crystal X-ray structure of D13 is shown in Figure 7.
The coordination geometry around nickel is essentially
A similar situation was observed in the reaction of [Ni-
(dippe)H]2 with 2-cyanonaphthalene (Scheme 1). The 31P
NMR spectrum of the two products indicates the presence of
ꢀ
(13) Benn, R.; Mynott, R.; Topalovic, I.; Scott, F. Organometallics
1989, 8, 2299.
(14) Stanger, A. Organometallics 1991, 10, 2979. Stanger, A.; Volhardt,
K. P. C. Organometallics 1992, 11, 317. (c) Stanger, A.; Weismann, H. J.
Organomet. Chem. 1996, 515, 183.

Article
Organometallics, Vol. 29, No. 11, 2010 2437
Figure 10. Energetics of C-C bond activation of 2-cyanonaphthalene by [Ni(dmpe)] (free energies in kcal mol-1) relative to the total
energies of fragments ([Ni(dmpe)] and 2-cyanonaphthalene) (PCM corrected in THF).
η2-nitrile and η2-arene complexes (see Figures SI-7 and SI-8).
Upon heating, (dippe)Ni(CN)(2-naphthyl) (E13) appeared,
and its single-crystal structure is shown in Figure 9. DFT
computational results (Figure 10) again indicate that among
all of the possible η2-arene species (SE3-12), only the fast
equilibration between SE3 and SE5 would be observed in the
NMR spectra. SE3 is the intermediate in the C-CN activation
process, connecting both to the η2-nitrile SE1 and the oxidative
addition product SE13. On the basis of the energies, the
oxidative addition product SE13 would be thermodynamically
preferred, and this matches the experimental observations.
To study the effect of substituents on the cyanonaphthalene,
[(dippe)NiH]2 has been reacted with 1-cyano-4-methylnaphtha-
lene and 1,4-dicyanonaphthalene (Scheme 1). For the reac-
tion with 1-cyano-4-methylnaphthalene, experimental results
are very similar to those seen with 1-cyano- and 2-cyano-
naphthalenes (Figures SI-9 and SI-10). The DFT calculations
(Figure 11) show that with an electron-donating substituent in
the para-position to the CN group, the energies of another two
η2-arene species (SF8 and SF10), in which nickel coordinates to
the unsubstituted ring, are now comparable to SF3 and SF5.
The kinetic barrier for equilibration between the latter two via
an η4 transition state is much lower. The transition state leading
to the sp3 Cipso-CH3 bond cleavage (TSF514) is about 16 kcal/
mol higher in energy than that of the C-CN bond activation
(TSF313), and the Ni(II) species SF14 is about 24 kcal/mol
higher in energy than SF15. Thus C-CN bond activation is
highly preferred both kinetically and thermodynamically over
C-CH3 bond activation. A single-crystal structure of F13 was
obtained, as shown in Figure 12.
the H NMR spectrum. Upon heating to 70 °C, the 31P{1H}
spectrum showed the characteristics of coalescence, which might
be due to the PNiP fragment rotating around the CdC double
bond, which would equilibrate the two phosphorus environments.
When the sample was cooled back to room temperature, the
resonances of G3 appeared as two sharp doublets again. With
continued heating at 75 °C, the C-CN activation product G13
started to appear. Upon heating to 80 °C for 36 h, small yellow
crystals of G13 formed, and the structure is shown in Figure 13b.
The bis-η2-nitrile complex G14 could also be formed by
adding another equivalent of [Ni(dippe)H]2 to G3, with a single
new pair of doublets in the 31P{1H} NMR spectrum (C6D6) at
δ 52.7 and 65.2 (dd, JP-P = 56, 13 Hz), indicative of two equi-
valent Ni(dippe) fragments coordinated to Ni(0), each with two
distinct phosphorus environments. The coupling constants
suggest that the nickel might coordinate to the CdC double
bond next to the cyano substituent from either face of the
dicyanonaphthalene molecule, as shown below. G14 turned out
to be very stable, and no C-CN cleavage was observed upon
heating or irradiation (λ > 300 nm). A similar bifacial coordi-
nation has been seen in [Cp*Rh(PMe3)]2(μ-η2:η2-naphtha-
lene)15 and [Ni(dtbpe)]2(μ-η2:η2-benzene).16
1
DFT calculations (Figure 14) show that the η2-arene
complex SG3 has lower energy than the η2-nitrile species
SG1, but higher energy than the oxidative addition product
One obvious difference in the reaction with 1,4-dicyano-
naphthalene is that the η2-nitrile complex (G1) can barely be
seen even at low temperature (Scheme 1, Figures SI-11 and SI-
12). Upon heating, G1 is completely converted to the η2-arene
species G3 (Figure 13a). G3 displays two sharp doublets in the
31P{1H} NMR spectrum, indicating two inequivalent phos-
phorus environments and an upfield singlet at δ 5.90 (2 H) in
(15) Chin, R. M.; Dong, L.; Duckett, S. B.; Jones, W. D. Organome-
tallics 1992, 11, 871.
€
(16) Bach, I.; Porschke, K.-R.; Goddard, R.; Kopiske, C.; Kruger,
€
ꢀ
C.; Rufinska, A.; Seevogel, K. Organometallics 1996, 15, 4959.

2438 Organometallics, Vol. 29, No. 11, 2010
Li et al.
Figure 11. Energetics of C-C bond activation of 1-cyano-4-methylnaphthalene by [Ni(dmpe)] (free energies in kcal mol-1) relative to
the total energies of fragments ([Ni(dmpe)] and 1-cyano-4-methylnaphthalene) (PCM corrected in THF).
Reaction with Cyanoanthracene and Cyanophenanthrene.
The reaction of [Ni(dippe)H]2 with 9-cyanoanthracene initi-
ally formed two Ni(0) species (Scheme 2). In this case, similar
to 1,4-dicyanonapthalene, the major product was the
η2-arene species H4, displaying two doublets in the 31P{1H}
NMR spectrum at δ 52.5 and 71.5 with JP-P = 44 Hz, similar
to the η2-acridine complex reported previously.6b The corres-
1
ponding H NMR spectrum showed four upfield proton
resonances at δ 5.34, 5.58, 5.65, and 5.80, suggesting an
η4-bound arene ring. However, the single-crystal X-ray
structure, shown in Figure 15, reveals η2-coodination. The
minor product was the Ni(0) adduct with the nitrile, H1. No
C-CN activation was observed upon heating or upon
irradiation (λ > 300 nm).
The computational investigation results are shown in Fig-
ure 16. The η2-arenecomplex SH4 is about3 kcal/mol lower in
energy than the η2-nitrile species SH1, which explains the
small amount of the latter observed in the experiment even
Figure 12. ORTEP drawing of Ni(dippe)(CN)(4-Me-1-Naphthyl),
at low temperature (Figures SI-14 and SI-15). SH2 is the
F13. Ellipsoids are shown at the 50% probability level. Selected bond
η2-arene intermediate preceding the C-CN activation. How-
lengths (A): Ni(1)-C(1), 1.935(3); Ni(1)-C(12), 1.892(5); Ni(1)-
ever, SH2 is much less stable compared to SH4 (>7 kcal/
P(1), 2.1952(11); Ni(1)-P(2), 2.1777(12); C(12)-N(1), 1.111(6).
mol). The transition state TSH210 leading to C-CN cleavage
is 3 kcal/mol higher in energy than the free fragments
(Ni(dmpe) þ 9-cyanoanthracene). Thus it is highly possible
that the complex decomposes rather than undergo C-CN
bond activation. The instabilities of both the intermediate
SH2 and transition state TSH210 result in the absence of the
oxidative addition product SH10 in the experiment. The fast
equilibration between SH4 and SH6 via TSH46 results in all
four aromatic protons being shifted upfield in 1H NMR
spectrum. In accord with SH4 being more stable than SH6,
crystallization of H4/H6 gives crystals of only H4, as shown in
Figure 15. The high energy of TSH210 for C-CN cleavage
suggests that substrate dissociation may occur in preference to
C-CN cleavage.
Selected angles (deg): P(1)-Ni(1)-P(2), 88.15(5); C(12)-Ni(1)-
C(1), 89.39(16); N(1)-C(12)-Ni(1), 176.5(4).
SG13, which explains that in the experiment the η2-arene was
initially the major product, while G13 was thermodynami-
cally preferred. All of the η2-arene species are at high energies
except for SG3 and SG5, which can rapidly equilibrate via
the η4-arene transition state TSG35 without interchanging
the two phosphorus environments. The equilibration also
results in a Cs symmetry intermediate η4-arene complex and
1
results in symmetric aromatic proton resonances in the H
NMR spectrum. A simulation of the PNiP fragment rotation
in SG3 has also been conducted, and the kinetic barrier is
very similar to that in the experiment (see Supporting
Information, Figure SI-13 and weo), providing evidence that
the coalescence arises from rotation of the CdC bond
around the nickel.
In the reaction with 9-cyanophenanthrene on the other
hand, both the η2-nitrile (I1) and η2-arene (I2) complexes
were observed at low temperature (Scheme 2, Figure SI-16).

Article
Organometallics, Vol. 29, No. 11, 2010 2439
Figure 13. (a) ORTEP drawing of Ni(dippe)(1,2-η2-1,4-dicyanonaphthalene) (G3). Ellipsoids are shown at the 50% probability level.
Selected bond lengths (A): Ni(1)-C(1), 1.9794(11); Ni(1)-C(2), 1.9765(12); Ni(1)-P(1), 2.1866(4); Ni(1)-P(2), 2.1807(4); C(1)-
C(11), 1.4404(16); C(11)-N(1), 1.1557(16); C(1)-C(2), 1.4556(16); C(2)-C(3), 1.4221(17); C(3)-C(4), 1.3704(18); C(4)-C(12),
1.4336(17); C(12)-N(2), 1.1522(17). Selected angles (deg): P(1)-Ni(1)-P(2), 92.092(15); C(2)-Ni(1)-C(1), 43.18(5); C(1)-C(11)-
N(1), 178.43(14); C(4)-C(12)-N(2), 178.85(15). (b) ORTEP drawing of Ni(dippe)(CN)(4-CN-naphthyl) (G13). Ellipsoids are shown
at the 50% probability level. Selected bond lengths (A): Ni(1)-C(1), 1.933(3); Ni(1)-C(12), 1.877(3); Ni(1)-P(1), 2.1847(8); Ni(1)-
P(2), 2.1915(9); C(12)-N(2), 1.137(4). Selected angles (deg): P(1)-Ni(1)-P(2), 88.32(3); C(12)-Ni(1)-C(1), 88.95(12); N(2)-C(12)-
Ni(1), 177.9(4); C(4)-C(11)-N(1), 178.6(4).
Figure 14. Energetics of C-C bond activation of 1,4-dicyanonaphthalene by [Ni(dmpe)] (free energies in kcal mol-1) relative to the
total energies of fragments ([Ni(dmpe)] and 1,4-dicyanonaphthalene) (PCM corrected in THF).
The former has two doublets in the 31P{1H} NMR spectrum
at δ 61.7 and 72.5 with JP-P = 68 Hz. The latter shows a pair
of doublets at δ 55.6 and 62.6 with smaller coupling constant
Upon irradiation for 30 min, the oxidative addition product
I18 appeared in the 31P{1H} NMR spectrum, with two sharp
doublets at δ 65.8 and 75.7 with JP-P = 21 Hz. After
irradiation for 36 h, only about 27% of I18 was formed,
and upon heating at 120 °C for 1 h, it was completely
converted back to I2.
Results from DFT calculations are summarized in Figure
18. The η2-nitrile species SI1 is about 1.4 kcal/mol higher in
energy than the η2-arene species SI2. While both adducts
could be observed at low temperature, upon warming, SI2 is
calculated to be preferred thermodyanically, consistent with
the experimental observations. All other possible η2-arene
1
(JP-P = 58 Hz). In the corresponding H NMR spectrum,
the resonances for the η2-arene species are shifted upfield
compared to the η2-nitrile species. When the temperature
was increased to 30 °C, the η2-nitrile complex I1 completely
converted into the η2-arene complex I2. A single-crystal
X-ray structure for the η2-arene complex was obtained
(Figure 17), which showed nickel coordinating to the CdC
double bond next to the cyano substituent. Upon heating to
120 °C for 1 week in THF, no C-CN cleavage was observed.

2440 Organometallics, Vol. 29, No. 11, 2010
Scheme 2. Reactions of [Ni(dippe)H]2 with 9-Cyanoanthracene and 9-Cyanophenanthrene
Li et al.
Conclusion
The reaction of [Ni(dippe)H]2 with cyanobenzenes, cya-
nonapthalene, and derivatives at low temperature leads to
the formation of both η2-nitrile and η2-arene complexes.
Both converted to C-CN activation products upon heating.
Due to the high polarity of the C-CN bond cleavage
products, solvent effects were taken into consideration in
all DFT calculations in terms of the PCM correction, and the
results show excellent agreement with the experimental ob-
servations. The transition state for the C-CN cleavage was
located on the potential energy surface and found to connect
with the η2-arene complex with nickel coordinated to the
CdC double bond next to the cyano substituent. In the case
of 9-cyanoanthracene and 9-cyanophenanthrene, η2-arene
species were more stable than η2-nitrile complexes. No
C-CN cleavage was observed in the reaction with 9-cya-
noanthracene, ascribed to the inability to coordinate to the
tetrasubstituted double bond adjacent to the nitrile. The
fluxionalities of the η2-arene complexes were due to low-
energy barriers for migration of the [Ni(dippe)] fragment
around the aromatic ring via a series of η3- or η4-coordinated
transition states.
Figure 15. ORTEP drawing of C29H41NNiP2 (H4). Ellipsoids
are shown at the 50% probability level. Selected bond lengths
(A): Ni(1)-C(1), 2.0285(16); Ni(1)-C(2), 1.9634(16); Ni(1)-
P(1), 2.1631(5); Ni(1)-P(2), 2.1697(5); C(1)-C(2), 1.449(3);
C(2)-C(3), 1.428(3); C(3)-C(4), 1.362(3); C(4)-C(12),
1.449(2); C(1)-C(11), 1.446(2); C(11)-C(12), 1.449(2). Sele-
cted angles (deg): P(1)-Ni(1)-P(2), 92.10(2); C(2)-Ni(1)-
C(1), 42.52(7); N(1)-C(15)-C(9), 178.8(2).
complexes (SI3-17) are much higher in energy than SI2 and
would not be expected to be observed in the NMR spectrum.
As for the 9-cyanoanthracene reaction, TSI218 for C-CN
cleavage is also at high energy, and dissociation may occur in
preference to C-CN activation.
Experimental Section
General Procedures. All reactions were carried out using
standard Schlenk and glovebox techniques under nitrogen.
Solvents were dried and distilled before use from sodium/
benzophenone ketyl or directly taken from an Innovative
Technologies MD-6 solvent purification system. Deuterated
solvents (Cambridge Isotope Laboratories) for NMR experi-
ments were dried over sodium/benzophenone ketyl and dis-
tilled under vacuum. All other chemicals and filter aids were
In reactions of the Ni(dippe) fragment with polycyclic
aromatic nitriles, the η2-arene complexes with nickel
coordinated via the CdC double bond containing a cyano
substituent were in every case the intermediates leading
to C-CN bond cleavage. Among all possible structures,
only certain η2-arenes were stable enough to be observed,
and some were even more stable than the η2-nitrile species.
The fluxional processes result from a [1,3] migration
around the end of the fused polycyclic aromatic ring via
an η4 transition state. This same preference for the for-
mation of η2-complexes in which the loss of resonance
energy is minimized was seen in studies of Cp*Rh(PMe3)-
(polycyclic arene) complexes17 and other P2Ni(arene)
complexes.18
1
reagent grade and were used as received. H and 31P{1H} NMR
spectra were determined on AVANCE400 spectrometers in
THF-d8 or toluene-d8; chemical shifts (δ) are relative to the
deuterated solvent residual protons, and 31P{1H} NMR spectra are
relative to external 85% H3PO4. The synthesis of [Ni(dippe)H]2
was carried out using the previously reported procedure.19 1,2-,
1,3-, and 1,4-Dicyanobenzene, 1- and 2-cyanonaphthalene,
9-cyanoanthracene, and 9-cyanophenanthrene were purchased
from Aldrich. 1,4-Dicyanonapthalene was obtained from
Alfa Aesar, and 1-cyano-4-methylnaphthalene was obtained
from Matrix Scientific. All were dried under vacuum before
use.
(17) Chin, R. M.; Dong, L.; Duckett, S. B.; Partridge, M. G.; Jones,
W. D.; Perutz, R. N. J. Am. Chem. Soc. 1993, 115, 7685.
€
(18) Brauer, D. J.; Kruger, C. Inorg. Chem. 1979, 16, 884.
(19) Vicic, D. A.; Jones, W. D. J. Am. Chem. Soc. 1997, 119, 10855.

Article
Organometallics, Vol. 29, No. 11, 2010 2441
Figure 16. Energetics of C-C bond activation of 9-cyanoanthracene by [Ni(dmpe)] (free energies in kcal mol-1) relative to the total
energies of fragments ([Ni(dmpe)] and 9-cyanoanthracene) (PCM corrected in THF).
correlation functional (LYP).22 All calculations were performed
using the Gaussian03 package.23 The Ni and P atoms were
represented with the effective core pseudopotentials of the
Stuttgart group and the associated basis sets improved with a
set of f-polarization functions for Ni (R = 3.130)24 and a set of
d-polarization functions for P (R = 0.387).25 The remaining
atoms (C, H, and N) were represented with 6-31G(d,p)26 basis
sets. The geometry optimizations were performed without any
symmetry constraints, and the local minima and the transi-
tion states were checked by frequency calculations. For each
transition-state structure, the intrinsic reaction coordinate
(IRC) routes were calculated in both directions toward the
corresponding minima. For some of the transition states,
the IRC calculations failed to reach the energy minima on the
potential energy surface; therefore, in those cases geometry
optimizations were carried out as a continuation of the IRC
path. Because of the polarity of the structures, the solvent effects
on their relative stabilities were evaluated by calculating the free
energies of solvation in terms of the polarizable continuum
model (PCM). The self-consistent reaction field calculations
using the PCM-UA0 solvation model27 were carried out for
the gas-phase-optimized structures. The dielectric constant in
the PCM calculations was set to ε = 7.58 to simulate THF as the
solvent media used in the experimental study. Gibbs free
energies have been calculated at 298.15 K and 1 atm. The
Ortep32 package was used to display the molecular structures.
Structure of [Ni(dippe)H]2. [Ni(dippe)H]2 was synthesized
according to the previously reported procedure.19 The initial
dark red, oily residue was dissolved in hexanes and slowly evapo-
rated under vacuum, yielding thin, dark red plates. NMR spectra
for [Ni(dippe)H]2 in THF-d8 (25 °C), 1H: δ -9.89 (quintet, 2 H,
bridging H), 1.25 (d, JH-H = 36 Hz, 48 H, CHMe2), 1.61 (s, 8 H,
CH2), 2.03 (s, 8 H, CHMe2); 31P{H}: δ 73.45 (s); 13C: δ 19.53
(s, CHMe2), 20.32 (s, CH2), 23.08 (m, CHMe2). Anal. Calcd for
C28H66Ni2P4: C, 52.21; H, 10.33. Found: C, 52.20; H, 10.45.
Figure 17. ORTEP drawing of C29H41NNiP2 (I2). Ellipsoids are
shown at the 50% probability level. Selected bond lengths (A):
Ni(1)-C(1), 1.9666(15); Ni(1)-C(2), 1.9608(14); Ni(1)-P(1),
2.1785(10); Ni(1)-P(2), 2.1708(11); C(1)-C(2), 1.452(2); C(1)-
C(14), 1.465(2); C(1)-C(15), 1.468(3); C(15)-N(1), 1.152(3);
C(2)-C(3). Selected angles (deg): P(1)-Ni(1)-P(2), 90.34(9);
C(2)-Ni(1)-C(1), 43.41(6); N(1)-C(15)-C(1), 178.7(3).
Computational Details. When available, known experimental
structures for the complexes were used as the starting point for
the calculations. To simplify these calculations, the i-Pr groups
were substituted by methyl groups. This simplification is as-
sumed to have no steric outcome on the calculations, as estab-
lished in earlier studies of both dmpe and dippe ligands on
nickel.7 The gas-phase structures were fully optimized in re-
dundant internal coordinates,20 with density functional theory
(DFT) and a wave function incorporating Becke’s three-para-
meter hybrid functional (B3),21 along with the Lee-Yang-Parr
(24) Ehlers, A. W.; Bohme, M.; Dapprich, S.; Gobbi, A.; Hollwarth,
A.; Jonas, V.; Kohler, K. F.; Stegmann, R.; Veldkamp, A.; Frenking, G.
Chem. Phys. Lett. 1993, 208, 111.
€ €
(25) Hollwarth, A.; Bohme, M.; Dapprich, S.; Ehlers, A. W.; Gobbi,
(20) Peng, C.; Ayala, P. Y.; Schlegel, H. B.; Frisch, M. J. J. Comput.
Chem. 1996, 17, 49.
€
A.; Jonas, V.; Kohler, K. F.; Stegmann, R.; Veldkamp, A.; Frenking, G.
(21) Becke, A. D. J. Chem. Phys. 1993, 98, 5648.
Chem. Phys. Lett. 1993, 208, 237.
(26) Hehre, W. J.; Ditchfield, R.; Pople, J. A. J. Chem. Phys. 1972, 56,
2257.
(22) Lee, C.; Yang, W.; Parr, R. G. Phys. Rev. B 1988, 37, 785.
(23) Frisch, M. J.; et al. et al. Gaussian03; Gaussian, Inc.,: Wallingford,
CT, 2004. For the full reference, see Supporting Information ref 1 .
(27) Barone, V.; Cossi, M.; Tomasi, J. J. Chem. Phys. 1997, 107, 3210.

2442 Organometallics, Vol. 29, No. 11, 2010
Li et al.
Figure 18. Energetics of C-C bond activation of 9-cyanophenanthrene by [Ni(dmpe)] (free energies in kcal mol-1) relative to the total
energies of fragments ([Ni(dmpe)] and 9-cyanophenanthrene) (PCM corrected in THF).
Reaction of [Ni(dippe)H]2 with 1,2-Dicyanobenzene. [Ni-
(dippe)H]2 (10 mg, 0.016 mmol) was dissolved in THF-d8,
transferred into an NMR tube capped with a septum, and
cooled to -78 °C in a dry ice/acetone bath. Then 1,2-dicyano-
benzene (4.0 mg, 0.031 mmol, dissolved in 0.02 mL of THF) was
then 1,2-dicyanobenzene (2.5 mg, 0.017 mmol) was added. A8 was
observed to form at room temperature, along with A6. Yellow-
orange crystals were obtained by vapor diffusion of a toluene
solution with hexanes under an N2 atmosphere at room tempera-
ture. There is also one Ni(dippe)(CN)(C6H4CN) molecule and a
toluene solvent molecule cocrystallized in the unit cell. NMR
spectra for A8 in C6D6 (25 °C), 1H: δ 7.30 (s, br, 1 H), 7.66-7.70
(m, 2 H), 7.79 (m, 1 H); 31P{H}: δ 63.4 and 77.5 (d, JP-P = 25 Hz),
63.1 and 74.5 (d, JP-P = 71 Hz). Anal. Calcd for C61.5H108N4Ni3P6
(corrected with 0.5 toluene): C, 58.37; H, 8.60; N, 4.43. Found: C,
58.62; H, 8.56; N, 4.24.
1
added while the tube was still in the bath. H and 31P NMR
spectra were recorded once every 10 °C as the reaction mixture
was warmed from -60 to 60 °C in the NMR probe. NMR
spectra for A1 in THF-d8 (-60 °C), 1H: δ 7.46 (t, JH-H = 8 Hz,
1 H, meta-H), 7.67 (t, JH-H = 8 Hz, 1 H, meta-H), 7.65 (d,
J
H-H = 8 Hz, 1 H, ortho-H), 7.76 (d, JP-H = 8 Hz, 1 H, ortho-
H); 31P{H}: δ 62.7 (d, JP-P = 62 Hz), 73.5 (d, JP-P = 62 Hz);
Reaction of [Ni(dippe)H]2 with 1,3-Dicyanobenzene (1:2 ratio).
[Ni(dippe)H]2 (10 mg, 0.016 mmol) was dissolved in THF-d8,
transferred into an NMR tube capped with a septum, and
cooled to -78 °C in a dry ice/acetone bath. Then 1,3-dicyano-
benzene (4.2 mg, 0.032 mmol, dissolved in 0.02 mL of THF) was
added while the tube was still in the bath. 1H and 31P{1H} NMR
spectra were recorded once every 10 °C as the reaction mixture
was warmed from -60 to 60 °C in the NMR probe. NMR
spectra for B1 in THF-d8 (-60 °C), 1H: δ 7.60 (t, JH-H = 8 Hz,
1 H, meta-H), 7.79 (d, JH-H = 8 Hz, 1, ortho-H), 7.97 (d,
1
NMR spectra for A2-5 in THF-d8 (-60 °C), H: δ 6.28 (d,
J
P-H = 7 Hz, 2 H, meta-H), 5.83 (d, JP-H = 7 Hz, 2 H, ortho-H);
31P{H}: δ 57.0 (s). See Supporting Information for stacked plots of
VT spectra.
Isolation of (dippe)Ni(CN)(C6H4CN), A6. [Ni(dippe)H]2 (10.2
mg, 0.016 mmol) was dissolved in toluene; then 1,2-dicyano-
benzene (4.5 mg, 0.034 mmol) was added. After heating at 100
°C for 1 h, all species converted to A6 completely. Yellow-
orange crystals were obtained by vapor diffusion of a toluene
solution with hexanes under an N2 atmosphere at room tem-
perature. NMR spectra for A6 in THF-d8 (25 °C), 1H: δ 0.55 (dd,
J = 7.2, 14.4 Hz, 3 H, CH3), 1.11 (dd, J = 6.8, 11.2 Hz, 3 H,
CH3), 1.23-1.29 (m, 6 H, CH3), 1.33-1.45 (m, 9 H, CH3), 1.52
(dd, J = 7.2, 15.6 Hz), 1.73-1.88 (m, 4 H, CH2), 2.0-2.06 (m,
1 H, CH), 2.30 (m, 1 H, CH), 2.39 (m, 1 H, CH), 2.54 (m, 1 H,
CH), 6.83 (t, J = 7.6 Hz, 1 H, meta-H), 7.07 (t, J = 7.6 Hz, 1 H,
meta-H), 7.29 (1 H, ortho-H), 7.46 (t, J = 6 Hz, 1 H, ortho-H);
31P{H}: δ 67.1 (d, JP-P = 25 Hz), 79.1 (d, JP-P = 25 Hz); 13C:
δ 16.88 (d, J = 5.1 Hz, CH3), 17.75 (s, CH3), 18.67 (d, J = 2.1
Hz, CH3), 19.17 (d, J = 2.6 Hz, CH3), 19.59 (s, CH3), 20.23 (d,
J = 2.3 Hz, CH3), 20.48 (s, CH3), 20.51 (dd, J = 14.3, 20.1 Hz,
CH2), 21.27 (d, J = 3.9 Hz, CH3), 22.37 (dd, J = 18.9, 24.1 Hz,
CH2), 22.86 (s, CH), 23.09 (s, CH), 26.84 (s, CH), 27.07 (d, J =
3.0 Hz, CH), 122.8 (s, CN), 122.9 (s, CH), 123.5 (s, C), 129.6 (d,
J = 2.8 Hz, CH), 132.7 (s, CH), 133.2 (dd, J = 30.6, 74.0 Hz,
CN), 138.3 (s, CH), 169.8 (dd, J = 27.6, 72.6 Hz, C). Anal. Calcd
for C22H36N2NiP2: C, 58.83; H, 8.08; N, 6.24. Found: C, 58.55;
H, 8.18; N, 6.14.
J
H-H = 8 Hz, 1 = H, ortho-H), 8.00 (s, 1 H, ortho-H); 31P{H}:
δ 64.8 (d, JP-P = 62 Hz), 76.4 (d, JP-P = 62 Hz); NMR spectra
for B2-4 in THF-d8 (-60 °C); 1H: δ 7.1 (d, JP-H = 4 Hz, 1 H,
meta-H) (other peaks are overlapped by other protons); 31P{H}:
δ 57.0 (d, JP-P = 74 Hz), 61.4 (d, JP-P = 74 Hz). After heating
at 60 °C for 13 h, the oxidative addition product B5 was the only
product left. NMR spectra for B5 in THF-d8 (25 °C), 1H: δ 0.93
(dd, J = 7, 16 Hz, 6 H, CH3), 1.12 (dd, J = 7, 14 Hz, 6 H, CH3),
1.25 (dd, J = 7, 14 Hz, 6 H, CH3), 1.42 (dd, J = 7, 16 Hz, 6 H,
CH3), 1.73-1.92 (m, 4 H, CH2), 2.05 (m, 2 H, CH), 2.39 (m, 2 H,
CH), 7.0 (m, 2 H), 7.64 (m, 2 H); 31P{H}: δ 68.0 (d, JP-P = 24
Hz), 78.9 (d, JP-P = 24 Hz); 13C: δ 18.18 (s, CH3), 19.12 (s,
CH3), 19.4 (d, J = 1.5 Hz, CH3), 20.32 (d, J = 2.9 Hz, CH3),
20.47 (dd, J = 14.6, 21.0 Hz, CH2), 22.76 (dd, J = 19.7, 23.7 Hz,
CH2), 24.82-26.33 (m, CH), 111.3 (s, br, CN), 120.8 (s, C), 126.0
(s, CH), 126.5 (s, CH), 135.0 (br, CN), 140.5 (s, CH), 142.5 (s,
CH), 163.2 (dd, J = 28.3, 74.0 Hz, C). Anal. Calcd for
C22H36N2NiP2: C, 58.83; H, 8.08; N, 6.24. Found: C, 58.58;
H, 7.86; N, 5.98.
Isolation of (dippe)Ni(μ-η2-N,C:η1-C-C6H4CN)Ni(CN)(dippe),
A8. [Ni(dippe)H]2 (10.0 mg, 0.016 mmol) was dissolved in toluene;
Reaction of [Ni(dippe)H]2 with 1,3-Dicyanobenzene (1:1 ratio).
[Ni(dippe)H]2 (13.8 mg, 0.021 mmol) was dissolved in C6D6 at

Article
Organometallics, Vol. 29, No. 11, 2010 2443
room temperature; then 1,3-dicyanobenzene (3.0 mg, 0.023
3 H, CH3), 1.37 (dd, J = 7, 14 Hz, 3 H, CH3), 1.48 (dd, J = 7, 16
Hz, 3 H, CH3), 1.57 (dd, J = 7, 15 Hz, 3 H, CH3), 2.29-2.58 (m,
8 H, CH and CH2), 7.04 (t, J = 7 Hz, 1 H), 7.24-7.29 (m, 3 H),
7.39 (t, J = 6 Hz, 1 H), 7.54 (d, J = 8 Hz, 1 H), 8.54 (d, J = 8 Hz,
1 H); 31P{H}: δ 64.9 (d, JP-P = 20 Hz), 75.0 (d, JP-P = 20 Hz).;
13C: δ 16.75 (s, CH3), 17.02 (s, CH3), 18.78 (s, CH3), 18.92
(s, CH3), 19.91 (s, CH3), 20.44 (s, CH3), 20.48 (s, br, CH3), 21.24
(s, CH3), 21.68 (s, CH2), 22.43 (s, CH2), 22.55 (s, CH), 22.78
(s, CH), 122.6 (s, CH), 123.2 (s, CH), 124.9 (s, CH), 125.3 (s, C),
126.2 (s, CH), 128.7 (s, CH), 129.9 (s, CH), 133.8 (s, C), 135.0 (s,
CN), 135.5 (s, CH), 143.9 (s, C). Anal. Calcd for C25H39NNiP2:
C, 63.32; H, 8.29; N, 2.95. Found: C, 62.85; H, 8.32; N, 2.97.
Reaction of [Ni(dippe)H]2 with 2-Cyanonaphthalene. [Ni(dippe)H]2
(9.8 mg, 0.015 mmol) was dissolved in THF-d8, transferred into an
NMR tube capped with a septum, and cooled to -78 °C in a dry ice/
acetone bath. Then 2-cyanonaphthalene (4.9 mg, 0.031 mmol,
dissolved in 0.02 mL of THF) was added while the tube was still in
the bath. 1Hand31P NMR spectra were recorded once every 10 °Cas
the reaction mixture was warmed from -60 to 80 °C in the NMR
probe. NMR spectra for E1 in THF-d8 (-60 °C), 1H: δ7.46(m,2H),
7.84 (d, J=8Hz, 2H), 7.91(d,J=8Hz,2H),8.14(s,1H);31P{H}:
δ 62.0 (d, JP-P = 65 Hz), 73.8 (d, JP-P = 65 Hz). NMR spectra for
E3/5 in THF-d8 (-60 °C), 1H: δ 6.12 (dd, J = 9, 3 Hz, 1 H), 6.46 (d,
J = 9 Hz, 1 H), 6.82 (t, J = 8 Hz, 1 H), 6.84 (s, 1 H), 6.96 (t, J =
6 Hz, 1 H), 7.27 (t, J = 8 Hz, 1 H), 7.84 (t, 1 H); 31P{H}: δ 55.0 (d,
1
mmol) was added. H and 31P NMR spectra were recorded at
25 °C in the NMR probe showing B6. NMR spectra for B6 in
THF-d8 (25 °C), 1H: δ 1.05 (dd, J = 6.8, 15.6 Hz, 12 H, CH3),
1.09-1.17 (overlapped, 24 H, CH3), 1.27 (dd, J = 7.2, 14.8 Hz,
12 H, CH3), 1.66 (m, CH2, 8H), 2.16 (m, 8 H, CH), 7.32 (t, J =
7.6 Hz, 1 H, meta-H), 7.61 (d, JH-H = 8.0 Hz, 2 H, ortho-H),
8.12 (s, 1 H, ortho-H); 31P{H}: δ 61.0 (d, JP-P = 69 Hz), 73.1 (d,
J
P-P = 69 Hz); 13C: δ 19.04 (s, CH3), 19.34 (d, J = 2.6 Hz, CH3),
19.84 (d, J = 7.6 Hz, CH3), 20.50 (d, J = 9.0 Hz, CH3), 20.88
(dd, J = 14.9, 19.1 Hz, CH2), 23.13 (t, J = 27.3 Hz, CH2), 25.46
(dd, J = 3.4, 13.4 Hz, CH), 26.38 (dd, J = 5.1, 17.4 Hz, CH),
128.4 (s, CH), 130.0 (s, C), 130.1 (d, J = 2.5 Hz, CH), 131.7 (s,
CH), 168.7 (dd, J = 8.5, 28.6 Hz, CN). Upon heating at 100 °C
for 1 h, the C-CN cleavage product B7 appeared, but the major
products were from decomposition. NMR spectra for B7 in
C6D6 (25 °C), 1H: δ 7.05 (t, J = 7 Hz, 1 H), 7.15 (m, overlapped,
2 H), 8.04 (d, J = 7 Hz, 1 H); 31P{H}: δ 63.2 (d, JP-P = 68 Hz),
75.3 (d, JP-P = 68 Hz), 67.3 (d, JP-P = 16 Hz), 76.0 (d, JP-P
=
17 Hz). The crystallization of B7 was unsuccessful because of
decomposition and B5 easily deposited from the solution.
Reaction of [Ni(dippe)H]2 with 1,4-Dicyanobenzene. [Ni-
(dippe)H]2 (9.6 mg, 0.015 mmol) was dissolved in THF-d8,
transferred into an NMR tube capped with a septum, and
cooled to -78 °C in a dry ice/acetone bath. Then 1,4-dicyano-
benzene (4.0 mg, 0.030 mmol, dissolved in 0.02 mL of THF) was
JP-P = 61 Hz), 64.1 (d, JP-P = 61 Hz).
1
added while the tube was still in the bath. H and 31P NMR
Isolation of Ni(dippe)(2-naphthyl)(CN). The mixture from the
above reaction, upon standing at room temperature, eventually
converted to a new species, which was the oxidative addition
product Ni(dippe)(2-naphthyl)(CN), E13. Yellow crystals were
obtained by vapor diffusion of a THF solution with hexanes
under an N2 atmosphere at room temperature. NMR spectra for
E13 in THF-d8 (25 °C), 1H: δ 0.933 (dd, J = 7, 15 Hz, 6 H, CH3),
1.13 (dd, J = 7, 14 Hz, 6 H, CH3), 1.21 (dd, J = 7, 14 Hz, 6 H,
CH3), 1.30 (dd, J = 7, 13 Hz, 6 H, CH3), 1.74-1.89 (m, 4 H,
CH2), 2.10 (m, 2 H, CH), 2.43 (m, 2 H, CH), 7.12 (t, J = 7 Hz,
1 H), 7.20 (t, J = 7 Hz, 1 H), 7.39 (d, J = 8 Hz, 1 H), 7.50 (d,
J = 8 Hz, 1 H), 7.57 (d, J = 8 Hz, 1 H), 7.65 (m, 1 H), 7.71
(d, J = 6 Hz, 1 H); 31P{H}: δ 67.0 (d, JP-P = 22 Hz), 77.1 (d,
JP-P = 21 Hz).; 13C: δ 17.70 (s, CH3), 18.72 (s, CH3), 19.07 (s,
CH3), 19.92 (d, J = 3.2 Hz, CH3), 22.49 (t, J = 21.7 Hz, CH2),
25.58 (s, CH), 25.79 (s, CH), 122.8 (s, CH), 124.1 (s, C), 124.5 (s,
CH), 126.2 (s, CH), 127.8 (s, CH), 128.5 (s, CH), 131.5 (s, C),
134.0 (s, CN), 135.1 (s, CH), 136.6 (s, CH), 142.2 (m, C). Anal.
Calcd for C25H39NNiP2: C, 63.32; H, 8.29; N, 2.95. Found: C,
63.08; H, 8.11; N, 2.80.
Reaction of [Ni(dippe)H]2 with 1-Cyano-4-methylnaphthalene.
[Ni(dippe)H]2 (10.2 mg, 0.016 mmol) was dissolved in THF-d8,
transferred into an NMR tube capped with a septum, and
cooled to -78 °C in a dry ice/acetone bath. Then 1-cyano-4-
methylcyanonaphthalene (5.3 mg, 0.031 mmol, dissolved in 0.02
mL of THF) was added while the tube was still in the bath. 1H
and 31P NMR spectra were recorded once every 10 °C as the
reaction mixture was warmed from -60 to 60 °C in the NMR
probe. NMR spectra for F1 in THF-d8 (-60 °C), 1H: δ 2.75 (s,
3 H, CH3-arene), 7.39 (d, J = 7 Hz, 1 H), 7.55 (m, 2 H), 7.82 (d,
J = 7 Hz, 1 H), 8.01 (d, J = 8 Hz, 1 H), 9.61 (d, J = 8 Hz, 1 H);
31P{H}: δ 61.4 (d, JP-P = 70 Hz), 72.7 (d, JP-P = 70 Hz); NMR
spectra for F3/5 in THF-d8 (-60 °C), 1H: δ 2.93 (s, 3 H, CH3-
arene), 6.27 (d, J = 5 Hz, 1 H), 6.90 (t, J = 8 Hz, 1 H), 7.07 (m, 2
H), 7.61 (d, J = 8 Hz, 1 H), 8.18 (t, J = 9 Hz, 1 H); 31P{H}: δ 56.1
(d, JP-P = 62 Hz), 60.2 (d, JP-P = 62 Hz). Upon heating, F13
appeared as well as decomposition. After one week at room
temperature, single crystals of F13 were formed in THF-d8
solution. Yellow needle-shaped crystals could also be obtained
by vapor diffusion of a THF solution with hexanes under an
N2 atmosphere at room temperature. NMR spectra for F13
in THF-d8 (25 °C) 1H: δ 0.059 (dd, J = 7.2, 14 Hz, 3 H,
CH3), 0.9391 (dd, J = 7.2, 16 Hz, 3 H, CH3), 1.05 (dd, J =
6.8, 11.2 Hz, 3 H, CH3), 1.29 (dd, J = 7.2, 12.4 Hz, 3 H, CH3),
spectra were recorded once every 10 °C as the reaction mixture
was warmed from -60 to 60 °C in the NMR probe. NMR
spectra for C1 in THF-d8 (-60 °C), 1H: δ 7.81 (s, 4 H, ortho-H);
31P{H}: δ 62.8 (d, JP-P = 62 Hz), 74.5 (d, JP-P = 62 Hz); NMR
spectra for C2 in THF-d8 (-60 °C), 1H: δ 5.91 (s, br, 4 H, ortho-
H); 31P{H}: δ 55.9 (d, JP-P = 71 Hz), 60.1 (d, JP-P = 72 Hz).
NMR spectra for C1 in THF-d8 (25 °C), 1H: δ 1.05-1.18 (m, 18
H), 1.23-1.29 (m, 6 H), 1.65-1.73 (m, 4 H), 2.06-2.22 (m, 4 H),
7.69 (d, J = 8 Hz, 2 H), 7.75 (d, J = 8.0 Hz, 2 H); 31P{H}: δ 67.5
(d, J = 63 Hz), 79.3 (d, J = 63 Hz). NMR spectra for C3 in
THF-d8 (25 °C), 1H: δ 0.92 (m, 6 H), 1.13 (m, 6 H), 1.27 (m, 6 H),
1.44 (m, 6 H), 1.72-1.82 (m, 4 H), 2.06-2.10 (m, 2 H),
2.38-2.41 (m, 2 H), 7.14 (d, J = 8 Hz, 2 H), 7.6 (d, br, J = 8
Hz, 2 H); 31P{H}: δ (ppm) 73.1 (d, J = 24 Hz), 83.6 (d, J = 24
Hz). NMR spectra for C4 in THF-d8 (25 °C), 31P{H}: δ (ppm)
66.4 (d, J = 68 Hz), 78.7 (d, J = 68 Hz).5b C1-C4 were reported
previously.6b IR data for C4 were recorded in the solid state
(νCN = 1739 cm-1) and in THF solution (νCN = 1738 cm-1),
indicating the same structure as seen in the X-ray study.6b
Reaction of [Ni(dippe)H]2 with 1-Cyanonaphthalene. [Ni(dippe)H]2
(9.8 mg, 0.015 mmol) was dissolved in THF-d8, transferred into an
NMR tube capped with a septum, and cooled to -78 °C in a dry ice/
acetone bath. Then 1-cyanonaphthalene (4.9 mg, 0.031 mmol,
dissolved in 0.02 mL of THF) was added while the tube was still in
the bath. 1Hand31P NMR spectra were recorded once every 10 °Cas
the reaction mixture was warmed from -60 to 80 °C in the NMR
probe. NMR spectra for D1 in THF-d8 (-60 °C), 1H: δ 7.50 (m,
3H), 7.54(t, J= 8 Hz, 1 H), 7.86 (t, J= 8 Hz, 2 H), 9.51 (d, JP-H
=
8Hz,1H);31P{H}: δ61.5(d,JP-P =68Hz),72.6(d,JP-P =68Hz).
NMR spectra for D3/D5 in THF-d8 (-60 °C), 1H: δ4.66 (dd, J = 5,
10 Hz, 1 H), 5.93 (d, J = 8 Hz, 1H), 6.15(dd, J = 6, 8 Hz, 1 H), 6.84
(t, J = 8 Hz, 1 H), 6.92 (d, J = 8 Hz, 1 H), 7.02 (t, J = 8 Hz, 1 H),
7.91 (d, J = 7 Hz, 1 H); 31P{H}: δ 57.4 (d, JP-P = 60 Hz), 60.7
(d, JP-P = 61 Hz).
Isolation of Ni(dippe)(1-naphthyl)(CN). The mixture from the
above reaction, upon standing at room temperature, eventually
converted to a new species, which is the oxidative addition
product Ni(dippe)(1-naphthyl)(CN), D13. Yellow crystals were
obtained by vapor diffusion of a benzene solution with hexanes
under an N2 atmosphere at room temperature. NMR spectra for
D13 in THF-d8 (25 °C), 1H: δ 0.051 (dd, J = 7, 14 Hz, 3 H, CH3),
0.927 (dd, J = 7, 16 Hz, 3 H, CH3), 1.050 (dd, J = 7, 12 Hz, 3 H,
CH3), 1.29 (dd, J = 7, 12 Hz, 3 H, CH3), 1.34 (dd, J = 7, 16 Hz,

2444 Organometallics, Vol. 29, No. 11, 2010
Li et al.
1.35 (dd, J = 7.2, 16 Hz, 3 H, CH3), 1.40 (dd, J = 7.2, 14 Hz,
3 H, CH3), 1.48 (dd, J = 7.2, 16 Hz, 3 H, CH3), 1.58 (dd, J = 7.6,
15.2 Hz, 3 H, CH3), 1.65-1.79 (m, 4 H, CH2), 2.35-2.58 (m,
4 H, CH), 2.53 (s, 3 H, CH3(naphthalene)), 6.94 (d, J = 6.8 Hz,
1 H), 7.24-7.28 (m, 3 H), 7.77 (m, 1 H), 8.60 (m, 1 H); 31P{H}: δ
64.8 (d, JP-P = 20 Hz), 75.1 (d, JP-P = 20 Hz); 13C: δ 16.70 (d,
J = 5.1 Hz, CH3), 17.04 (s, CH3), 18.82 (d, J = 14.5 Hz, CH3),
19.29 (s, CH3), 19.85 (s, CH3), 20.43 (d, J = 13.5 Hz, CH3), 21.22
(d, J = 3.9 Hz, CH3), 20.36-20.69 (m, CH2), 22.44 (t, J = 21.6
Hz, CH2), 22.49 (s, CH), 22.73 (s, CH), 26.55-26.68 (m, CH3),
26.88 (s, nap-CH3), 123.0 (s, CH), 124.6 (s, CH), 124.8 (s, CH),
126.7 (s, C), 127.5 (s, C), 129.1 (s, CH), 129.2 (s, CH), 133.6 (s,
C), 134.3 (s, CN), 136.1 (s, CH), 143.9 (s, C). Anal. Calcd for
C26H41NNiP2: C, 63.96; H, 8.46; N, 2.87. Found: C, 63.86; H,
8.50; N, 2.86.
6.75 (m, 2 H), 7.32 (m, 2 H); 31P{H}: δ 50.7 (dd, JP-P = 57, 12
Hz), 63.2 (dd, JP-P = 57, 12 Hz); 13C: δ 17.64 (d, J = 4.3 Hz,
CH3), 18.05 (s, CH3), 19.39 (s, CH3), 19.28-19.39 (m, CH3),
19.98-20.15 (m, CH3), 20.69 (d, J = 7.6 Hz, CH3), 20.91-21.39
(m, CH2), 21.90 (d, J = 7.5 Hz, CH3), 21.82-22.18 (m, CH2),
24.63 (m, CH), 26.86-27.01 (m, CH), 34.75 (d, J = 17.3 Hz, C),
55.32 (d, J = 20.7 Hz, CH), 123.7 (s, CH), 125.0 (s, br, CN),
125.5 (s, CH), 133.6 (s, C).
Reaction of [Ni(dippe)H]2 with 9-Cyanoanthracene. [Ni-
(dippe)H]2 (11.0 mg, 0.017 mmol) was dissolved in THF-d8,
transferred into an NMR tube capped with a septum, and
cooled to -78 °C in a dry ice/acetone bath. Then 9-cyanoan-
thracene (7.2 mg, 0.034 mmol, dissolved in 0.02 mL of THF) was
1
added while the tube was still in the bath. H and 31P NMR
spectra were recorded once every 10 °C as the reaction mixture
was warmed from -60 to 80 °C in the NMR probe. NMR
=
Reaction of [Ni(dippe)H]2 with 1,4-Dicyanonaphthalene. [Ni-
(dippe)H]2 (10.2 mg, 0.016 mmol) was dissolved in THF-d8,
transferred into an NMR tube capped with a septum, and
cooled to -78 °C in a dry ice/acetone bath. Then 1,4-dicyano-
naphthalene (5.6 mg, 0.031 mmol, dissolved in 0.02 mL of THF)
was added while the tube was still in the bath. 1H and 31P NMR
spectra were recorded once every 10 °C as the reaction mixture
was warmed from -60 to 70 °C in the NMR probe. NMR
spectra for H1 in THF-d8 (-60 °C), 31P{H}: δ 61.4 (d, JP-P
70 Hz), 69.5 (d, JP-P = 70 Hz). NMR spectra for H4/6 in THF-
d8 (-60 °C), 1H: δ 5.34 (t, J = 6 Hz, 1 H), 5.58 (t, J = 6 Hz, 1 H),
5.65 (s, br, 1 H), 5.80 (s, br, 1 H), 6.93 (s, br, 1 H), 6.98 (t, J = 8
Hz, 1 H), 7.13 (t, J = 8 Hz, 1 H), 7.26 (d, J = 8 Hz, 1 H), 7.47
(d, J = 8 Hz, 1 H); 31P{H}: δ 52.5 (d, JP-P = 33 Hz), 71.5 (d,
JP-P = 33 Hz). The mixture was dissolved in benzene and
allowed to slowly evaporate under a nitrogen atmosphere,
producing dark purple crystals. NMR spectra for H4 in THF-
d8 (25 °C), 1H: δ 0.611 (dd, J = 7.2, 15.2 Hz, 3 H, CH3),
0.915-1.18 (m, 21 H, CH3), 1.47-1.57 (m, 4 H, CH2), 1.703-
1.79 (m, 2 H, CH), 1.94-2.03 (m, 2 H, CH), 5.49 (s, 1 H), 5.60 (s,
1 H), 5.72 (s, 1 H), 5.88 (s, 1 H), 7.03 (t, J = 7.2 Hz, 1 H) 7.08 (s,
1 H), 7.17 (t, J = 7.2 Hz, 1 H), 7.32 (t, J = 8 Hz, 1 H), 7.62 (d,
J = 8.4 Hz, 1 H); 31P{H}: δ 53.1 (d, JP-P = 42 Hz), 69.1 (d,
JP-P = 42 Hz); 13C: δ 18.61 (s, CH3), 18.95 (s, CH3), 19.03 (s,
CH3), 19.36 (s, CH3), 19.73 (s, CH3), 19.81 (s, CH3), 19.88 (s,
CH3), 20.14 (d, J = 6.6 Hz, CH3), 21.39-22.28 (m, CH2),
24.83-26.74 (m, CH), 73.12 (d, J = 11.1 Hz, CH), 78.28 (d,
J = 5.8 Hz, CH), 94.15 (d, J = 8.2 Hz, CH), 94.89 (s, CN), 97.35
(s, CH), 119.8 (s, C), 120.2 (s, CH), 123.8 (s, CH), 124.4 (s, CH),
125.9 (s, CH), 127.2 (s, CH), 132.4 (s, C), 133.3 (s, C), 138.6 (s,
C), 147.5 (s, C). Anal. Calcd for C25H39NNiP2: C, 66.44; H, 7.88;
N, 2.67. Found: C, 66.09; H, 7.18; N, 3.14.
spectra for G1 in THF-d8 (-60 °C), 31P{H}: δ 64.5 (d, JP-P
=
64 Hz), 75.0 (d, JP-P = 64 Hz). NMR spectra for G3/5 in THF-
d8 (-60 °C), 1H: δ 0.79 (dd, J = 7, 16 Hz, 6 H, CH3), 0.94 (dd,
J = 7, 13 Hz, 6 H, CH3), 1.06-1.14 (12 H, CH3), 1.59 (m, 2 H,
CH2), 1.90 (m, 2 H, CH2), 2.14 (m, 2 H, CH), 5.90 (s, 2 H), 7.12
(m, 2 H), 7.38 (m, 2 H); 31P{H}: δ 59.3 (d, JP-P = 47 Hz), 62.8 (d,
JP-P = 46 Hz). Yellow crystals were obtained by vapor diffu-
sion of a toluene solution with hexanes under an N2 atmosphere
at room temperature. NMR spectra for G3/5 in THF-d8 (25 °C),
1H: δ 0.879 (dd, J = 6.8, 15.2 Hz, 6 H, CH3), 0.973 (dd, J = 7.2,
13.2 Hz, 6 H, CH3), 1.11-1.21 (m, 12 H, CH3), 1.56-1.66 (m,
4 H, CH2), 1.83 (m, 2 H, CH), 2.13 (m, 2 H, CH), 5.83 (s, 2 H,
ortho-H), 7.11 (m, 2 H), 7.44 (m, 2 H); 31P{H}: δ 61.2 (d, JP-P
=
48 Hz), 63.4 (d, JP-P = 48 Hz); 13C: δ 18.93 (s, CH3), 19.30 (s,
CH3), 19.52 (d, J = 5.3 Hz, CH3), 19.96 (d, J = 5.5 Hz, CH3),
20.85 (dd, J = 14.9, 22.4 Hz, CH2), 21.99 (dd, J = 15.8, 38.7 Hz,
CH2), 25.30-25.71 (m, CH), 66.38 (d, J = 11.7 Hz, C), 96.76 (d,
J = 3.6 Hz, CH), 121.6 (s, CN), 124.8 (s, CH), 126.7 (s, CH),
132.8 (s, C). Anal. Calcd for C26H38N2NiP2: C, 62.55; H, 7.67;
N, 5.61. Found: C, 62.68; H, 7.55; N, 5.44. Upon heating a THF
solution of G1 þ G3-5 to 80 °C for 36 h, G13 formed and was
crystallized from solution. NMR spectra for G13 in THF-d8
(25 °C), 1H: δ 0.096 (dd, J = 7.2, 14.4 Hz, 3 H, CH3), 0.968 (dd,
J = 7.2, 16.0 Hz, 3 H, CH3), 1.07 (dd, J = 7.2, 12 Hz, 3 H, CH3),
1.31 (dd, J = 7.2, 13.2 Hz, 3 H, CH3), 1.37 (dd, J = 7.2, 16.8 Hz,
3 H, CH3), 1.41 (dd, J = 7.2, 14.4 Hz, 3 H, CH3), 1.49 (dd, J =
7.2, 16 Hz, 3 H, CH3), 1.58 (dd, J = 7.2, 15.2 Hz, 3 H, CH3), 2.04
(m, 2H, CH2), 2.40 (m, 2H, CH2), 2.49-2.58 (m, 4 H, CH),
7.44-7.53 (overlapped, 3 H), 7.64 (m, 1 H), 7.99 (d, J = 8 Hz,
1 H), 8.69 (d, J = 8 Hz, 1 H); 31P{H}: δ 68.3 (d, JP-P = 24 Hz),
78.7 (d, JP-P = 24 Hz); 13C: δ 16.72 (d, J = 5 Hz, CH3), 17.15 (s,
CH3), 18.79 (s, CH3), 18.95 (s, CH3), 19.82 (s, CH2), 20.40 (s,
CH3), 20.50 (s, CH3), 20.63 (s, CH2), 21.15 (d, J = 5 Hz, CH3),
22.33 (m, CH2), 22.81 (s, CH), 23.04 (s, CH), 26.79 (s, CH), 26.93
(s, CH), 104.5 (s, C), 119.8 (s, C), 125.0 (s, CH), 125.9 (s, CH),
127.8 (s, CH), 128.5 (s, C), 129.8 (s, CH), 132.1 (s, C), 133.4 (s,
CH), 136.6 (s, CH), 143.1 (s, C). Anal. Calcd for C26H38N2NiP2:
C, 62.55; H, 7.67; N, 5.61. Found: C, 62.29; H, 7.85; N, 5.43.
Reaction of [Ni(dippe)H]2 with 1,4-Dicyanonaphthalene (1:1
ratio). [Ni(dippe)H]2 (11.4 mg, 0.018 mmol) was dissolved
in THF-d8 at room temperature; then 1,4-dicyanonaphthalene
(2.6 mg, 0.014 mmol) was added. 1H and 31P NMR spectra were
recorded at 25 °C. NMR spectra for G14 in THF-d8 (25 °C), 1H:
δ 0.495 (dd, J = 7, 15 Hz, 6 H, CH3), 0.798 (dd, J = 7, 10 Hz,
6 H, CH3), 1.02-1.30 (overlapped, 36 H, CH3), 1.43-1.55 (m,
8 H, CH2), 1.57-1.62 (m, 2 H, CH), 2.01 (m, 4 H, CH), 2.10 (m,
2 H, CH), 2.26 (m, 2 H, CH), 3.88 (d, J = 6 Hz, 2 H, ortho-H),
Reaction of [Ni(dippe)H]2 with 9-Cyanophenanthrene. [Ni-
(dippe)H]2 (10.6 mg, 0.016 mmol) was dissolved in THF-d8,
transferred into an NMR tube capped with a septum, and
cooled to -78 °C in dry ice/acetone bath. Then 9-cyanonphe-
nanthrene (6.2 mg, 0.030 mmol, dissolved in 0.02 mL of THF)
was added while the tube was still in the bath. 1H and 31P NMR
spectra were recorded once every 10 °C as the reaction mixture
was warmed from -60 to 60 °C in the NMR probe. NMR
spectra for I1 in THF-d8 (-60 °C), 1H: δ 7.61 (d, J = 7 Hz, 1 H),
7.69 (m, 3 H), 7.99 (d, J = 8 Hz, 1 H), 8.26 (s, 1 H), 8.84 (m, 2 H),
9.76 (s, br, 1 H); 31P{H}: δ 61.7 (d, JP-P = 68 Hz), 72.5 (d,
J
P-P = 68 Hz); NMR spectra for I2 in THF-d8 (-60 °C), 1H: δ
7.01 (m, 2 H), 7.07 (t, J = 7 Hz, 1 H), 7.20 (t, J = 8 Hz, 1 H), 7.37
(d, J = 8 Hz, 1 H), 7.74 (d, J = 8 Hz, 1 H), 7.83 (m, 2 H), 7.99
(d, J = 8 Hz, 1 H); 31P{H}: δ 55.6 (d, JP-P = 57 Hz), 62.6 (d,
JP-P = 58 Hz). Single crystals of I2 were obtained by vapor
diffusion of a toluene solution with pentane under an N2 atmo-
sphere at room temperature. NMR spectra for I2 in THF-d8
(25 °C), 1H: δ 0.209 (dd, J = 6.8, 16.4 Hz, 3 H, CH3), 0.350 (dd,
J = 7.2, 15.6 Hz, 3 H, CH3), 0.754 (dd, J = 7.2, 10.8 Hz, 3 H,
CH3), 0.858 (dd, J = 7.2, 10 Hz, 3 H, CH3), 1.08-1.21 (m, 6 H,
CH3), 1.33-1.39 (m, 6 H, CH3), 1.41-1.66 (m, 6 H, CH and
CH2), 2.03-2.08 (m, 2 H, CH2), 4.67 (t, J = 5.6 Hz, 1 H), 7.0 (q,
J = 8, 16.8 Hz, 2 H), 7.08 (t, J = 7.2 Hz, 1 H), 7.20 (t, J = 7.6 Hz,
1 H) 7.40 (d, J = 7.6 Hz, 1 H), 7.82 (d, J = 5.6 Hz, 2 H), 7.88
(d, J = 8 Hz, 1 H); 31P{H}: δ 55.2 (d, JP-P = 59 Hz), 61.8 (d,
J
P-P = 59 Hz); 13C: δ 17.18 (d, J = 5.1 Hz, CH3), 17.89 (s, CH3),
19.34 (d, J = 5.8 Hz, CH3), 19.78 (d, J = 7.4 Hz, CH3),
19.95-20.13 (m, CH3), 20.97 (d, J = 6.2 Hz, CH3), 21.27
(dd, J = 3.8, 27.4 Hz, CH), 20.94-21.59 (m, CH2), 24.14 (dd,

Article
Organometallics, Vol. 29, No. 11, 2010 2445
J = 3.7, 15.8 Hz, CH), 26.63-26.92 (m, CH), 34.74 (d, J = 18.5
Hz, C), 50.68 (d, J = 21.8 Hz, CH), 122.9 (s, CH), 123.0 (s, CH),
123.1 (s, CH), 123.3 (s, CH), 123.9 (s, br, CN), 126.2 (s, CH),
126.5 (s, CH), 127.8 (d, J = 3.2 Hz, CH), 128.4 (s, CH), 128.6 (s,
CH), 130.3 (d, J = 2.5 Hz, C), 135.8 (d, J = 3.6 Hz, C), 140.0 (d,
J = 4.5 Hz, C). Irradiation of the sample for 36 h producted
∼27% I18. NMR spectra for I18 in THF-d8 (25 °C), 1H: δ 0.034
(dd, J = 7, 14 Hz, 3 H, CH3), 7.33 (m, 1 H), 7.42 (m, 1 H), 7.53 (t,
J = 7 Hz, 2 H), 7.71 (s, 1 H), 7.59 (t, J = 7 Hz, 2 H), 8.52 (d, J =
Acknowledgment. We would like to acknowledge the
U.S. Department of Energy, Office of Basic Energy Sciences,
grant DE-FG02-86ER13569, for financial support.
Supporting Information Available: NMR spectra at ambient
temperature, VT NMR spectra, tables and pictures of calculated
stable structures and transition states, and Cartesian coordinates of
the optimized geometries from DFT calculations are available.
Movies showing the fluxional processes and C-CN cleavage reac-
tions. Full details of the X-ray structure determinations. This mate-
rial is available free of charge via the Internet at http://pubs.acs.org.
The structures are available from the Cambridge Crystallographic
Database as CCDC 759830-759839 and 772709.
7 Hz, 1 H), 8.72 (d, J = 8 Hz, 1 H); 31P{H}: δ 52.7 (dd, JP-P
=
56, 13 Hz), 65.2 (dd, JP-P = 56, 13 Hz). Anal. Calcd for
C29H41NNiP2: C, 66.44; H, 7.88; N, 2.67. Found: C, 66.25; H,
7.76; N, 2.65.