Intramolecular oxidative cyclization of alkenes and nitriles with nickel(0)

Article abstract of DOI:10.1021/om2001603

The use of Me₂AlCl as an additive was found to allow the oxidative addition of the Ar-CN bond in 2-(2-methylallyl)benzonitrile on nickel(0) in the presence of PⁿBu₃, giving a trans-arylnickelcyanide complex. In contrast, i

Full text of DOI:10.1021/om2001603

ARTICLE
pubs.acs.org/Organometallics
Intramolecular Oxidative Cyclization of Alkenes and Nitriles with
Nickel(0)
Masato Ohashi,†,‡ Masashi Ikawa,† and Sensuke Ogoshi*,†
†Department of Applied Chemistry, Faculty of Engineering, Osaka University, Suita, Osaka 565-0871, Japan
‡Center for Atomic and Molecular Technologies, Osaka University, Suita, Osaka 565-0871, Japan
S Supporting Information
b
ABSTRACT: The use of Me2AlCl as an additive was found to allow the
oxidative addition of the ArꢀCN bond in 2-(2-methylallyl)benzonitrile
on nickel(0) in the presence of PnBu3, giving a trans-arylnickelcyanide
complex. In contrast, in the presence of PCy3, the intramolecular
oxidative cyclization on nickel(0) took place to afford a nickeladihydro-
pyrrole. Without the addition of Me2AlCl, the quantitative generation of
an η2:η2-5-ene-nitrile Ni(0) species, which was definitely converted to the nickeladihydropyrrole after treatment with Me2AlCl, was
observed. In addition, TfOH also promoted the oxidative cyclization of the η2:η2-5-ene-nitrile complex to yield the corresponding
five-membered aza-nickelacycle. A similar intramolecular oxidative cyclization occurred when 2-allylbenzonitrile was used in the
presence of a Lewis acid, such as Me2AlCl, Me2AlOTf, and Me3SiOTf, or of TfOH to give the corresponding nickeladihydropyrroles
in quantitative yield. The molecular structures of a series of nickeladihydropyrroles were unambiguously determined by means of
X-ray crystallography. The nickeladihydropyrrole derived from (2-methylallyl)benzonitrile and TfOH was found to react with
HSiMe2Ph at 80 °C to furnish a silanamine derivative. The reaction was expanded to a Ni(0)/PCy3/TfOH-catalyzed coupling
reaction of 5-ene-nitrile and HSiMe2Ph, yielding the corresponding silanamine in 84% yield.
’ INTRODUCTION
cleavage of nitriles as a key reaction step have appeared in the last
decades.14ꢀ18
Oxidative cyclization of two π-components with nickel(0)
species is an efficient method for the generation of a heteronick-
elacycle, which has been proposed as a key reaction intermediate
in nickel-catalyzed multicomponent coupling reactions as well as
[2 þ 2 þ 2] cycloaddition reactions to give heterocycles.1 Earlier
studies reported by Hoberg had focused on the formation of
heteronickelacycles by oxidative cyclization with nickel(0) com-
plexes, including carbon dioxide2 or isocyanate3 as one π-com-
ponent. In recent studies, our group reported the formation of
five-membered heteronickelacycles by oxidative cyclization of a
carbonꢀcarbon unsaturated bond and a carbon-heteroatom
double bond with nickel(0), such as alkeneꢀaldehyde, alkeneꢀ
ketone, dieneꢀaldehyde, dieneꢀketone, alkyneꢀaldehyde or
alkyneꢀimine.4 However, the oxidative cyclization of nitriles and
unsaturated hydrocarbons with nickel is very rare (Scheme 1).5
The occurrence of the oxidative cyclization of alkyne and nitrile
with nickel(0) has only been inferred from the formation of an
enone by the protonolysis of a reaction mixture of diphenylace-
tylene and benzonitrile with Ni(0).5a Louie and co-workers
proposed that, in the Ni/NHC-catalyzed formation of pyridines
from alkynes and nitriles, a nickelapyrrole intermediate would be
generated through the oxidative cyclization of an alkyne and a
nitrile with nickel(0).5b,c The reason for the rareness is that the
oxidative addition of the CꢀCN bond of η2-nitrile Ni(0) com-
plexes competes against oxidative cyclization (Scheme 1).6ꢀ13 In
fact, some nickel-catalyzed reactions involving a CꢀCN bond
When all transition metal complexes are included, a significant
number of aza-metalacycles generated by oxidative cyclization of
nitriles and carbonꢀcarbon unsaturated compounds has been
discovered.19ꢀ27 To the best of our knowledge, earlier research
on a series of dihydrotitanapyrroles, generated by the reaction of
(η5-C5Me5)Ti(η2-C2H4) with an equimolar amount of nitriles,
was conducted by Bercaw et al.19 Buchwald and co-workers, around
the same time, engaged in the study on zirconocene-benzyne and
zirconocene-alkyne complexes, both of which were found to
react with nitriles to give the corresponding zirconapyrroles.20
The first structural determination of the aza-metallacycle, derived
from the oxidative cyclization of the in situ generated Cp2Zr(η2-
benzyne) species with butyronitrile, was also achieved.20c They
also demonstrated that treatment of a zirconocene-cyclobutene
complex with nitriles gave the corresponding aza-zirconacycles,21
and a related aza-zirconacycle derived from a zirconocene-cyclo-
butadiene complex with pivalonitrile was structurally determined
by Sharp et al.21b The formation of five-membered aza-zirconacycle
derivatives was also reported by the use of dialkylzirconocenes,
such as Cp2ZrBu2 and Zp2ZrEt2, as a synthetic precursor.22 Further-
more, Fagan and Nugent showed that an aza-zirconacyclopenta-
diene complex, generated by the intramolecular cyclization with
1-cyano-5-heptyne, reacted with S2Cl2 to give an isothiazole,23
Received: February 20, 2011
Published: April 19, 2011
r
2011 American Chemical Society
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Scheme 1. Two Possible Reactions of Nitrile with Nickel(0)
Scheme 3. Oxidative Cyclization of 3 Promoted by either
Me2AlCl or TfOH
Scheme 2. Oxidative Addition of 1 to Nickel(0)
while aza-zirconacycles were well-known to be hydrolyzed to
yield the corresponding carbonyl compounds. A few aza-metalla-
cycles containing a Group 4 metal, in addition, have also been
synthesized and structurally well-defined by means of X-ray
diffraction analysis.24
Although the number of aza-metallacycles generated by the
oxidative cyclization of nitriles and carbonꢀcarbon unsaturated
compounds with Group 4 metal is not relatively small, as
mentioned above, the corresponding aza-metallacycles contain-
ing except for Group 4 metals are still rare. Strickler and Wigley
inferred the generation of aza-tantalacyclopentadiene in the
course of the reaction of tantalum-tolan complex with nitrile.25
Legzdins and co-workers proposed the formation of aza-tung-
stenacyclopentadienyl intermediate from the reaction of an η2-
PhCCH tungsten complex with acetonitrile.26 Roesky et al.
reported a unique reactivity of cyclopropane analogues of
aluminum bearing a bulky β-diketiminato ligand toward benzo-
nitrile to yield an aza-aluminacyclopentadiene, the molecular
structure of which was definitely confirmed by X-ray diffraction
study.27 Here, we report the intramolecular oxidative cyclization
of nitrile and alkene with nickel(0), promoted by a Lewis or
Brønsted Acid. In addition, we observed that the aza-nickelacycle
could act as a key intermediate in a catalytic reaction.
Figure 1. ORTEP drawing of 3 with thermal ellipsoids at the 30%
probability level. One of the two independent molecules in a unit cell of
3 is depicted. H atoms are omitted for clarity.
The molecular structure was determined by X-ray crystallogra-
phy (Scheme 3, Figure 1). The coordination geometry of the
nickel center in 3 appeared to be a Y-shaped trigonal-planar
structure, in which the midpoints of the carbonꢀcarbon double
and carbonꢀnitrile triple bonds are assumed to serve as a
coordination center. The C1ꢀN and C2ꢀC3 bond distances
of 1.215(7) and 1.390(9) Å, respectively, were slightly longer
than those observed in uncoordinated PhCN (1.168(3) Å)29 and
ethylene (1.336(3) Å),30 due to the contribution of back-dona-
tion from the nickel(0) center. The η2:η2-coordination structure
of 3 was also observed in solution, as evidenced by the upfield
shift of the 13C resonances attributable to the coordinating alkene
and nitrile moieties (δC 154.9, 76.9, and 50.4 for C1, C2, and C3,
respectively).
The addition of Me2AlCl to a solution of 3 promoted oxidative
cyclization to give a nickeladihydropyrrole (4a) quantitatively
(Scheme 3). The formation of a new carbonꢀcarbon bond
between C1 and C2 (1.508(3) Å) could be observed in the
molecular structure of 4a revealed by X-ray crystallography
(Figure 2). Simultaneous formation of NiꢀN and NiꢀC3 bonds
(1.9164(14) and 1.958(2) Å, respectively) was also confirmed,
and these bond lengths were consistent with those observed in a
’ RESULTS AND DISCUSSION
The reaction of 2-(2-methylallyl)benzonitrile (1) with Ni-
(cod)2 and PnBu3 in C6D6 gave a mixture of 1 and Ni(cod)-
(PnBu3)2. The addition of Me2AlCl to the reaction mixture
promoted the oxidative addition of the aryl-CN bond to nickel-
(0) at room temperature to yield an arylnickelcyanide complex
(2) quantitatively (Scheme 2). The oxidative addition of an
ArꢀCN bond to nickel(0) promoted by Lewis acids has been
reported.6b,14,28 We also reported the oxidative addition of an
ArꢀCN bond of 2-(3-methyl-3-butenyl)benzonitrile by the
addition of Me2AlCl and suggested that the coordination ability
of the nitrile group was enhanced by coordination of nitrile
nitrogen to Me2AlCl.14c Insertion of the intramolecular alkene
into the nickel-arene bond in 2 did not occur, even at 60 °C for
72 h, although the corresponding complex derived from 2-(3-
methyl-3-butenyl)benzonitrile underwent insertion under the
same reaction conditions.14c
In the presence of PCy3, the reaction of 1 with Ni(cod)2
gave an η2:η2-5-ene-nitrile Ni(0) complex (3) quantitatively.
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the N and O2 atoms (2.99 Å) suggests the existence of the
hydrogen bond. The 1H NMR spectrum of 4b exhibited a broad
singlet at δ 8.95 ppm, assignable to the hydrogen adjacent to the
nitrogen atom.
As mentioned above, in the reaction of Ni(0) with 1, the
nature of phosphine ligands apparently influenced a choice of the
two reaction courses, the oxidative addition of the ArꢀCN bond
in the presence of PnBu3 or the oxidative cyclization in the
presence of PCy3. However, the factor determining the reaction
course was found to depend on not only the nature of ligands but
also the chain length of ene-nitrile. Treating of 2-(3-methyl-3-
butenyl)benzonitrile (5) with Ni(cod)2 and PCy3 in the pre-
sence of Me2AlCl followed by protolysis resulted in the quanti-
tative formation of an intramolecular carbocyanation product
(6), which was the product via the oxidative addition of the
ArꢀCN bond (Scheme 4).14c Monitoring of the initial stage of
the reaction before adding Me2AlCl by means of NMR spec-
troscopy indicated the formation of two Ni(0) intermediates
(A and B). These results clearly show that PCy3 promotes
predominantly the oxidative addition of the ArꢀCN bond
when 5, which has a longer alkyl chain than 1, is employed as
a substrate.
Figure 2. ORTEP drawing of 4a with thermal ellipsoids at the 30%
probability level. H atoms are omitted for clarity.
In a similar manner, the reaction of 2-allylbezonitrile (7) with
Ni(cod)2 in the presence of PCy3 led to the qualitative formation
of the corresponding η2:η2-5-ene-nitrile Ni(0) complex (8)
(Scheme 5). The molecular structure of 8 was unambiguously
determined by means of X-ray crystallography, and the ORTEP
drawing is shown in Figure 4. The coordination geometry of the
nickel center as well as the C1ꢀN and C2ꢀC3 bond distances
(1.204(2) and 1.401(3) Å, respectively) of 8 were consistent with
those observed in the analogous η2:η2-5-ene-nitrile complex 3.
The resonance assignable to the coordinating PCy3 ligand ap-
peared as a singlet at δ 37.4 in the 31P{1H} NMR spectrum of 8.
In the presence of Me2AlCl, the oxidative cyclization of 8
occurred faster than that of 3 at room temperature to quantita-
tively yield an aza-nickelacycle (9a) (Scheme 5). In addition, the
oxidative cyclization of 8 proceeded smoothly with the addition
of Me2AlOTf, resulting in the quantitative formation of the
corresponding nickeladihydropyrrole (9b). X-ray diffraction
studies of 9a and 9b clearly demonstrated the formation of the
five-membered NiꢀNꢀC1ꢀC2ꢀC3 framework (Figure 5). In
spite of the similar five-membered framework, however, the
NiꢀN bond distance of 9b (1.9949(19) Å) was slightly longer
than that found in 4aꢀb (1.9164(14) and 1.905(9) Å, re-
spectively) and 9a (1.930(3) Å). The same coordination mode
of Me2AlOTf to the five-membered heteronickelacycle was
previously demonstrated in the reaction of tBuCHO and diphe-
nylacetylene with nickel(0).4h
As with the reaction of 3 with TfOH, the addition of an
equimolar amount of TfOH allowed the oxidative cyclization of 8
to yield a nickeladihydropyrrole (9c) analogous to 4b in quanti-
tative yield (Scheme 6). In contrast, treatment of 8 with
CH3COOH instead of TfOH did not promote the correspond-
ing oxidative cyclization. The interatomic distance between the
N and O2 atoms (2.94 Å) was almost equal to that observed in 4b
(vide supra), which also suggested the existence of the hydrogen
bond (Figure 6). A broad singlet at δ 9.13 ppm observed in the
1H NMR spectrum of 9c was assigned to the OH group
hydrogen-bonding to the nitrogen atom. Furthermore, similar
oxidative cyclization was promoted by the use of Me3SiOTf,
affording 9d in a quantitative yield (Scheme 6). The X-ray
diffraction study of 9d clearly showed that the SiꢀO bond in
Figure 3. ORTEP drawing of 4b with thermal ellipsoids at the 30%
probability level. H atoms are omitted for clarity.
structurally well-defined seven-membered aza-nickelacycle.4d
The chloride atom of 4a bridged between the nickel and
aluminum atoms, so Me2AlCl served not only as a Lewis acid
to promote the oxidative cyclization of 3, but also as a Lewis base
to stabilize the square-planar geometry of the Ni(II) center in 4a
by coordination of the chloride atom to the nickel.31 The
important role of Lewis acid in promoting oxidative addition
has already demonstrated by our group4a,b,h and other groups.32
The C2ꢀC3 and C1ꢀN bond distances (1.534(2) and 1.274(2)
Å, respectively) of 4a were nearly identical to the typical lengths
of carbonꢀcarbon single and carbonꢀnitrogen double bonds,
respectively.
The oxidative cyclization of 3 was also promoted by the
addition of a stoichiometric amount of TfOH. A nickeladihy-
dropyrrole (4b) was isolated in 97% yield and its molecular
structure was determined by X-ray crystallography (Scheme 3,
Figure 3). Similar to the chloride atom in 4a, one of the oxygen
atoms in the trifluoromethanesulfonate group of 4b coordinated
to the nickel center to allow it to adopt a 16-electron, square-
planar geometry. The C1ꢀC2 and NiꢀN bond lengths of
1.504(13) and 1.284(11) Å, respectively, of 4b were almost
equal to those observed in 4a. The interatomic distance between
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Table 1. Crystallographic Data of 3, 4aꢀb, 8, and 9aꢀd a,b
complex
3
4a
4b
8
empirical formula
C
29H44NNiP
C31H50AlClNNiP
588.83
C30H45F3NNiO3PS
646.41
C28H42NNiP
482.31
formula weight
color, description
temperature, K
cryst. System
space group
a, Å
496.33
yellow, block
123(2)
orange, block
123(2)
yellow, block
123(2)
yellow, block
123(2)
monoclinic
P2/c (#13)
14.7687(12)
12.0964(10)
30.477(3)
triclinic
monoclinic
P21/n (#14)
9.1579(8)
monoclinic
P21/c (#14)
8.3374(5)
33.3279(17)
9.2706(6)
P1 (#2)
10.4287(5)
12.2964(8)
14.4467(8)
66.299(2)
80.093(2)
67.103(2)
1562.40(15)
2
b, Å
22.3334(17)
15.0975(14)
c, Å
R, deg
β, deg
101.537(2)
93.729(3)
99.118(2)
γ, deg
volume, Å3
5334.6(8)
8
3081.3(5)
2543.4(3)
4
Z
4
calculated density, Mg mꢀ3
2θmax, deg
limiting indices
1.236
50.7
1.252
1.393
1.260
61.0
54.9
50.0
ꢀ17e h e 16, ꢀ14 e k
e 14, ꢀ36 e l e 36
0.804
ꢀ12 e h e 13, ꢀ15 e k
e 15, ꢀ18 e l e 15
0.806
ꢀ10e h e 10, ꢀ26 e k
e 25, ꢀ17 e l e 17
0.799
ꢀ11e h e 11, ꢀ46 e k
e 45, ꢀ13 e l e 13
0.841
absorption coefficient, mmꢀ1
max. and min transmission
F(000)
0.856 (max)/0.795 (min)
2144
0.739 (max)/0.602 (min)
632
0.857 (max)/0.741 (min)
1368
0.679 (max)/0.632 (min)
1040
crystal size, mm
0.30 ꢁ 0.20 ꢁ 0.20
1.013
0.70 ꢁ 0.50 ꢁ 0.40
1.106
0.40 ꢁ 0.30 ꢁ 0.20
1.360
0.60 ꢁ 0.60 ꢁ 0.50
1.035
goodness-of-fit on F2
reflections collected/unique
no. of variables
27633/9523 [R(int) = 0.141] 15159/7028 [R(int) = 0.028] 23332/5312 [R(int) = 0.127] 30975/7653 [R(int) = 0.059]
592
329
364
287
R1, wR2 [I > 2σ(I)]
R1, wR2 (all data)
residual electron density, e Åꢀ3 1.079 (max), ꢀ0.675 (min)
0.0768, 0.1602
0.1611, 0.1984
0.0338, 0.0862
0.0390, 0.0897
0.838 (max), ꢀ0.417 (min)
0.1193, 0.3070
0.1582, 0.3437
2.310 (max), ꢀ0.750 (min)
0.0463, 0.1090
0.0688, 0.1249
1.207 (max), ꢀ0.532 (min)
complex
9a
9b
9c
9d
empirical formula
C30H48AlClNNiP
574.80
C31H48AlF3NNiO3PS
688.42
C29H43F3NNiO3PS
632.38
C32H51F3NNiO3PSSi C7H8
3
formula weight
color, description
temperature, K
cryst. System
space group
a, Å
796.70
yellow, block
296(2)
orange, block
123(2)
yellow, block
123(2)
red, block
123(2)
monoclinic
P21/c (#14)
16.6868(13)
10.2681(8)
18.9795(17)
monoclinic
P21/n (#14)
12.1333(9)
15.7000(11)
19.0696(12)
monoclinic
P21/n (#14)
10.5957(5)
15.5640(8)
18.4190(10)
triclinic
P1 (#2)
9.4279(7)
14.2349(10)
15.7794(10)
74.939(2)
87.102(2)
84.712(2)
2035.5(2)
2
b, Å
c, Å
R, deg
β, deg
113.851(2)
109.714(2)
104.836(2)
γ, deg
volume, Å3
2974.2(4)
3419.7(4)
2936.2(3)
Z
4
4
4
calculated density, Mg mꢀ3
2θmax, deg
limiting indices
1.284
1.337
1.431
1.300
57.0
61.0
50.0
50.0
ꢀ22 e h e 22, ꢀ13 e k
e 13, ꢀ25 e l e 25
0.920 (max)/0.849 (min)
0.845
ꢀ17 e h e 17, ꢀ22 e k
e 22, ꢀ26 e l e 27
0.865 (max)/0.662 (min)
0.748
ꢀ12e h e 12, ꢀ18 e k
e 18, ꢀ21 e l e 21
0.921 (max)/0.851 (min)
0.837
ꢀ11e h e 11, ꢀ16 e k
e 16, ꢀ18 e l e 18
0.830 (max)/0.738 (min)
0.646
max. and min transmission
absorption coefficient, mmꢀ1
F(000)
1232
1456
1336
848
crystal size, mm
goodness-of-fit on F2
0.20 ꢁ 0.20 ꢁ 0.10
1.110
0.60 ꢁ 0.50 ꢁ 0.20
1.082
0.20 ꢁ 0.20 ꢁ 0.10
1.072
0.50 ꢁ 0.30 ꢁ 0.30
1.053
reflections collected/unique
30573/7492 [R(int) = 0.086] 41324/10380 [R(int) = 0.054] 15731/5043 [R(int) = 0.088] 16182/7146 [R(int) = 0.064]
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Table 1. Continued
complex
9a
9b
9c
9d
no. of variables
318
382
354
456
R1, wR2 [I > 2σ(I)]
0.0643, 0.1587
0.0460, 0.1070
0.0574, 0.1097
0.0547, 0.1355
0.0716, 0.1498
R1, wR2 (all data)
0.1142, 0.2048
0.0707, 0.1207
0.1208, 0.1514
residual electron density, e Åꢀ3 1.203 (max), ꢀ1.102 (min)
0.871 (max), ꢀ0.630 (min)
0.901 (max), ꢀ0.826 (min)
0.863 (max), ꢀ0.598 (min)
a R1 = (Σ Fo| ꢀ |Fc )/Σ|Fo|. b wR2 = [Σw(Fo2 ꢀ Fc2)2/Σ(wFo4)]1/2; the function minimized: w(Fo2 ꢀ Fc2)2.
Scheme 4. Reaction of 5 with Ni(0) in the Presence of PCy3
and Me2AlCl
Figure 4. ORTEP drawing of 8 with thermal ellipsoids at the 30%
probability level. H atoms are omitted for clarity.
Scheme 5. Oxidative Cyclization of 8 Promoted by Me2AlX
(X = Cl and OTf)
role in this transformation, and that this stoichiometric formation
of 10 from 1 and HSiMe2Ph via the nickeladihydropyrrole inter-
mediate 4b may be applied to the catalytic reaction. In fact, in the
presence of Ni(cod)2 and PCy3 (10 mol % each) and TfOH (5
mol %), the reaction of HSiMe2Ph with 1 at 80 °C afforded 10 in
84% isolated yield (Scheme 8). As shown in Scheme 8, this
catalytic reaction probably proceeded via the TfOH-promoted
intramolecular oxidative cyclization of 1 with Ni(0), followed by
hydrosilylation of the resulting NiꢀN bond.
In conclusion, we demonstrated the Me2AlCl-mediated in-
tramolecular oxidative cyclization of 5-ene-nitrile with nickel(0)
in the presence of PCy3 as a ligand. Me2AlCl played two important
roles for the oxidative cyclization of 5-ene-nitrile, as a Lewis acid
to promote the cyclization reaction and as a Lewis base to stabilize
the resulting square-planner structure of the Ni(II) product. In
contrast, when PnBu3 was used as a ligand, oxidative addition of
the CꢀCN bond of the 5-ene-nitrile to Ni(0) took place under
the same reaction conditions. The oxidative cyclization of 5-ene-
nitrile was also observed with the addition of a Brønsted acid such
as TfOH. The nickeladihydropyrrole product reacted with HSi-
Me2Ph to give a silanamine derivative in the presence of 5-ene-
nitrile. We also achieved the catalytic formation of silanamine.
This catalytic reaction is the first example of a Ni(0)-catalyzed
transformation reaction obviously involving the formation of an
aza-nickelacycle intermediate via the oxidative cyclization of a
nitrile and a carbonꢀcarbon unsaturated molecule.
Me3SiOTf was completely cleaved (Figure 6).4a As a result,
unlike the other nickeladihydropyrroles 4b, 9b, and 9c, the
triflate in 9d was coordinated to the nickel center as a mono-
anionic monodentate ligand. In addition, a new SiꢀN bond was
formed with a distance of 1.783(3) Å, whereas the NꢀC1 bond
distance of 1.282(4) Å was the typical length of the CdN double
bond. Therefore, the slight elongation of the NiꢀN bond
distance (1.997(3) Å) may be due to the formation of a NiꢀN
coordination bond.
Finally, the reaction of aza-nickelacycles with HSiMe2Ph was
examined. Only 4b was found to react with HSiMe2Ph at 80 °C in
the presence of 1 to afford a silanamine derivative (10) in 81%
yield (Scheme 7). However, in the absence of 1, the silanamine
10 was not generated. This observation suggests that the
existence of 1, which has alkene and nitrile moieties that can
coordinate to stabilize a Ni(0) species, might play an important
’ EXPERIMENTAL SECTION
General. All manipulations were conducted under a nitrogen atmo-
sphere using standard Schlenk or drybox techniques. 1H, 31P and
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Figure 5. ORTEP drawings of 9a (left) and 9b (right) with thermal ellipsoids at the 30% probability level. H atoms are omitted for clarity.
99%). The attempt to purify the crude product by recrystallization failed
due to its high solubility. 1H NMR (400 MHz, C6D6): δ ꢀ0.25 (s, 6H,
-AlMe2), 0.70ꢀ1.60 (m, 54H, PnBu3), 1.78 (s, 3H, CH2dC(CH3)-),
3.57 (s, 2H, -C6H4CH2-), 4.87 (s, 1H, CHHdC(CH3)-), 4.94 (s, 1H,
CHHdC(CH3)-), 6.80ꢀ7.13 (m, 4H, -C6H4-). 31P{1H} NMR (109
Hz, C6D6): δ 13.2 (s). 13C{1H} NMR (100 MHz, C6D6): δ ꢀ6.8
(s, -AlMe2), 14.0 (s, PnBu3), 23.8 (d, JCP = 6.0 Hz, PnBu3), 23.9 (s,
Scheme 6. Oxidative Cyclization of 8 Promoted by ROTf
(R = H and Me3Si)
CH2dC(CH3)-), 24.0 (d, JCP = 14.0 Hz, PnBu3), 24.9 (d, JCP
=
6.0 Hz, PnBu3), 25.0 (d, JCP = 6.0 Hz, PnBu3), 26.9 (s, PnBu3), 48.9
(s, -C6H4CH2-), 113.1 (s, CH2dC(CH3)-), 123.2 (s, -C6H4-), 125.5
(s, -C6H4-), 128.5 (s, -C6H4-), 135.4 (t, JCP = 4.0 Hz, -C6H4-), 143.4
13C NMR spectra were recorded at room temperature on JEOL GSX-270S,
JEOL AL-400 and BRUKER DPX-400 spectrometers. The chemical
shifts in 1H and 13C NMR spectra were recorded relative to Me4Si (δH =
δC = 0) or residual C6D5H (δH and δC = 7.16 and 128.0, respectively).
The chemical shifts in 31P NMR spectra were recorded using 85%
H3PO4aq as an external standard. Assignment of the resonances
(t, JCP = 3.0 Hz, -C6H4-), 144.2 (s, CH2dC(CH3)-), 154.9 (t, JCP
24.5 Hz, -CtN), 157.7 (t, JCP = 27.5 Hz, -C6H4-).
=
Generation of (PCy3)Ni(η2:η2-CH2dC(CH3)CH2C6H4CtN)-
(PCy3) (3). To a solution of Ni(cod)2 (6.9 mg, 0.025 mmol) and PCy3
(7.0 mg, 0.025 mmol) in 0.5 mL of C6D6 was added 1 (4.1 mg, 0.026
mmol) at room temperature. The color of the solution immediately
changed from orange to light yellow, resulting in the quantitative
formation of 3.
observed in H and 13C NMR spectra was based on Hꢀ H COSY,
HMQC, and HMBC experiments. Elemental analyses were performed
at Instrumental Analysis Center, Faculty of Engineering, Osaka University.
X-ray crystal data were collected with a Rigaku RAXIS-RAPID Imaging Plate
diffractometer. Crystallographic data are summarized in Table 1. Several
nickel complexes containing aluminum atom as a component are too
sensitive toward oxygen or moisture to obtain accurate elemental analysis.
Materials. The degassed and distilled solvents (benzene, toluene,
and hexane) used in this work were commercially available. C6D6 was
distilled from sodium benzophenone ketyl. All commercially available
reagents were distilled and degassed prior to use.
1
1
1
Isolation of 3. To a toluene solution of Ni(cod)2 (165.0 mg, 0.60
mmol) and PCy3 (168.3 mg, 0.60 mmol) was added 1 (94.3 mg, 0.60
mmol) at room temperature. The color of the solution changed
immediately from orange to light yellow. The reaction mixture was
stirred for 15 min, and then all volatiles were removed in vacuo to give
yellow solids. The solids were washed with hexane to give 3 (271 mg,
91% yield). Further purification was achieved by recrystallization from
toluene/hexane at ꢀ35 °C. 1H NMR (400 MHz, C6D6): δ 1.22ꢀ2.31
(m, 33H, Cy), 1.41 (obscured by Cy, 3H, CH2dC(CH3)-), 2.30
(obscured by Cy, 1H, CHHdC(CH3)-), 2.58 (d, J = 9.6 Hz, 1H,
CHHdC(CH3)-), 2.79 (d, J = 15.6 Hz, 1H, -C6H4CHH-), 3.42 (dd, J =
10.2, 15.6 Hz, 1H, -C6H4CHH-), 6.94 (dd, J = 6.8, 6.8 Hz, 1H, -C6H4-),
7.05ꢀ7.11 (m, 2H, -C6H4-), 8.10 (d, J = 7.2 Hz, 1H, -C6H4-). 31P{1H}
NMR (109 Hz, C6D6): δ 37.5 (s). 13C{1H} NMR (100 MHz, C6D6): δ
21.9 (d, JCP = 2.0 Hz, CH2dC(CH3)-), 26.1 (s, Cy), 27.2 (d, JCP = 3.0
Hz, Cy), 27.3 (d, JCP = 3.0 Hz, Cy), 29.8 (d, JCP = 3.0 Hz, Cy), 33.7 (d,
JCP = 15.0 Hz, Cy), 41.9 (s, -C6H4CH2-), 50.4 (d, JCP = 4.0 Hz,
CH2dC(CH3)-), 76.9 (d, JCP = 11.0 Hz, CH2dC(CH3)-), 115.7
(s, -C6H4-), 126.6 (s, -C6H4-), 127.6 (s, -C6H4-), 129.6 (s, -C6H4-),
Generation of trans-(PnBu3)2Ni(C6H4-CH2C(CH3)dCH2)-
(CtN Al(CH3)2Cl) (2). To a solution of Ni(cod)2 (6.9 mg, 0.025
3
mmol) and PnBu3 (12.5 μL, 0.050 mmol) in 0.5 mL of C6D6 was added
2-(2-methylallyl)benzonitrile (1) (3.9 mg, 0.025 mmol) at room
temperature. After 15 min, generation of Ni(cod)(PnBu3)2 was observed
and 1 remained intact. The color of the solution changed gradually from
yellow to light yellow by addition of Me2AlCl (1.08 M solution in hexane,
23.0 μL, 0.025 mmol) to the mixture. After 45 h, the title complex 2 was
generated quantitatively.
Isolation of 2. To a solution of Ni(cod)2 (110 mg, 0.40 mmol) and
PnBu3 (200 μL, 0.80 mmol) in 3.0 mL of toluene at room temperature was
added 1 (62.8 mg, 0.40 mmol) and Me2AlCl (1.08 M solution in hexane,
370 μL, 0.40 mmol). The reaction mixture was thermostatted at 60 °C
for 1 h and the color of the solution changed gradually from yellow to light
yellow. All volatiles were removed in vacuo to give yellow oil (283 mg,
130.1 (s, -C6H4-), 147.1 (d, JCP = 6.0 Hz, -C6H4-), 154.9 (d, JCP
8.0 Hz, -CtN). Anal. Calcd for C29H44NNiP: C, 70.18; H, 8.94; N, 2.82.
Found: C, 69.40; H, 8.69; N, 2.75.
Reaction of 3 with AlMe2Cl. To a solution of 3 (9.9 mg, 0.02 mmol) in
0.5 mL of C6D6 was added Me2AlCl (1.08 M solution in hexane, 19.0 μL,
=
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Figure 6. ORTEP drawings of 9c (left) and 9d (right) with thermal ellipsoids at the 30% probability level. H atoms and solvated molecules in 9d (C7H8)
are omitted for clarity.
Scheme 7. Reaction of 4b with HSiMe2Ph in the Presence
of 1
Scheme 8. Ni(0)/PCy3/TfOH-Catalyzed Reaction of 1 with
HSiMe2Ph
0.02 mmol) at room temperature. The color of the solution gradually
changed from yellow to orange, resulting in the quantitative formation of
a nickeladihydropyrrole (4a).
Isolation of 4a. To a toluene solution of Ni(cod)2 (110.0 mg, 0.40
mmol), PCy3 (112.2 mg, 0.40 mmol) and 1 (62.8 mg, 0.40 mmol) was
added Me2AlCl (1.08 M solution in hexane, 370 μL, 0.40 mmol) at room
temperature. The color of the solution changed from yellow to reddish
orange. The reaction mixture was stirred for 2 h, and then all volatiles
were removed in vacuo to give orange solids. The solids were washed
with hexane to give 4a (223 mg, 95%). Further purification was achieved
Isolation of 4b. To a toluene solution of Ni(cod)2 (137.5 mg, 0.50
mmol), PCy3 (140.2 mg, 0.50 mmol) and 1 (87.5 mg, 0.56 mmol) was
added TfOH (44 μL, 0.50 mmol) at room temperature. The color of the
solution changed from yellow to reddish orange. The reaction mixture
was stirred for 15 min, and then all volatiles were removed in vacuo to
give yellow solids. The solids were washed with hexane to give 4b (315
mg, 97%). Further purification was achieved by recrystallization from
THF/hexane at ꢀ35 °C. 1H NMR (400 MHz, THF-d8): δ 0.59 (m, 1H,
-Ni-CHH-), 1.20ꢀ2.20 (m, 33H, Cy), 1.33 (obscured by Cy, 1H,-Ni-
CHH-), 1.72 (obscured by Cy, 3H, -NiCH2C(CH3)-), 2.72 (d, J = 16.2
Hz, 1H, -C6H4CHH-), 2.77 (d, J = 16.2 Hz, 1H, - C6H4CHH-), 7.29 (d,
J = 7.6 Hz, 1H, -C6H4-), 7.34 (dd, J = 7.6, 7.6 Hz, 1H, -C6H4-), 7.49 (dd,
J = 7.6, 7.6 Hz, 1H, -C6H4-), 7.62 (brs, 1H, -C6H4-), 8.95 (brs, 1H, -NH).
31P{1H} NMR (109 MHz, THF-d8): δ 27.1 (s). 13C{1H} NMR (100
MHz, THF-d8): δ 17.4 (brs, -NiCH2-), 27.6 (s, Cy), 28.6 (s, Cy), 28.8 (s,
Cy), 30.8 (d, JCP = 9.2 Hz, Cy), 32.0 (brs, -NiCH2C(CH3)-), 33.1 (d, JCP
= 20.7 Hz, Cy), 41.7 (s, -C6H4CH2-), 63.3 (s, -NiCH2C(CH3)-), 124.0
(brs, -C6H4-), 128.1 (s, -C6H4-), 128.7 (s, -C6H4-), 131.7 (d, JCP = 9.2
Hz, -C6H4-), 155.1 (s, -C6H4-), 202.3 (s, -CdNH-Ni-). Anal. Calcd for
C30H45F3NNiO3PS: C, 55.74; H, 7.02; N, 2.17. Found: C, 55.30; H,
7.09; N, 2.12.
1
by recrystallization from toluene/hexane at ꢀ35 °C. H NMR (400
MHz, C6D6): δ 0.04 (s, 3H, -AlMe2), 0.13 (s, 3H, -AlMe2), 0.81 (dd, J =
9.0, 9.0 Hz, 1H, -Ni-CHH-), 1.11ꢀ2.03 (m, 33H, Cy), 1.73 (obscured
by Cy, 1H, -Ni-CHH-), 1.78 (obscured by Cy, 3H, -Ni-CH2C(CH3)-),
2.46 (d, J = 15.8 Hz, 1H, -C6H4CHH-), 2.55 (d, J = 15.8 Hz, 1H,
-C6H4CHH-), 6.88 (d, J = 7.0 Hz, 1H, -C6H4-), 6.96 (dd, J = 6.2, 7.0 Hz,
1H, -C6H4-), 7.06 (dd, J = 6.2, 7.0 Hz, 1H, -C6H4-), 7.69 (d, J = 7.0 Hz,
1H, -C6H4-). 31P{1H} NMR (109 MHz, C6D6): δ 26.7 (s). 13C{1H}
NMR (100 MHz, C6D6): δ ꢀ7.2 (s, -AlMe2), ꢀ5.9 (s, -AlMe2), 24.0 (d,
J
J
CP = 26.0 Hz, -NiCH2-), 26.9 (s, Cy), 28.0 (s, Cy), 28.1 (s, Cy), 30.3 (d,
CP = 12.0 Hz, Cy), 32.1 (s, -NiCH2C(CH3)-), 33.9 (d, JCP = 18.0 Hz,
Cy), 40.5 (s, -C6H4CH2-), 68.0 (d, JCP = 8.0 Hz, -NiCH2C(CH3)-),
122.7 (s, -C6H4-), 127.5 (s, -C6H4-), 127.8 (s, -C6H4-), 131.5 (s, -C6H4-),
134.6 (s, -C6H4-), 154.5 (s, -C6H4-), 202.2 (s, -CdN(AlMe2)Ni-). Anal.
Calcd for C31H50AlClNNiP: C, 63.23; H, 8.56; N, 2.38. Found: C,
62.63; H, 8.40; N, 2.36.
Reaction of 3 with TfOH. To a solution of 3 (19.9 mg, 0.04 mmol) in
0.5 mL of C6D6 was added TfOH (3.5 μL, 0.04 mmol) at room temperature.
The color of thesolutionimmediatelychangedfromyellowto lightyellow,
resulting in the quantitative formation of a nickeladihydropyrrole (4b).
Reaction of 2-(3-Methyl-3-butenyl)benzonitrile (5) with Ni(cod)2 in
the Presence of PCy3. To a solution of Ni(cod)2 (11.0 mg, 0.04 mmol)
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and PCy3 (11.2 mg, 0.04 mmol) in 0.5 mL of C6D6 was added 5 (6.8 mg,
0.04 mmol) at room temperature. Monitoring of the reaction by means
of NMR spectroscopy revealed that the conversion of the starting
materials (Ni(cod)2 and 5) is 44% for 10 min and that generation of a
mixture of η2:η2-6-ene-nitrile nickel(0) complex (A) and η2-nitrile
nickel(0) complex (B) is found to be generated in 9 and 35% yield,
respectively. The resulting reaction mixture was treated with an equi-
molar amount of Me2AlCl (1.08 M solution in hexane, 38.0 μL, 0.041
mmol) to give a complicated mixture. After 5 h, the reaction mixture was
exposed to air for the sake of decomposition of nickel species, and then
GC-Mass analysis of the crude product clearly showed that all of 5 were
consumed and 2-(1-methyl-2,3-dihydro-1H-inden-1-yl)acetonitrile (6)
was formed as a solo product. These nickel(0) complexes A and B were
tentatively identified based on the characteristic resonances observed in
the 1H and 31P NMR spectra.
(dd, J = 8.0, 16.8 Hz, 1H, -Ni-CHH-), 1.08ꢀ2.00 (m, 33H, Cy), 1.60
(obscured by Cy, 1H, -Ni-CHH-), 2.23 (dd, J = 8.0, 16.0 Hz, 1H, -
C6H4CHH-), 2.60 (dd, J = 6.4, 16.0 Hz, 1H, -C6H4CHH-), 3.49 (m, 1H,
-NiCH2CH-), 6.83 (d, J = 7.6 Hz, 1H, -C6H4-), 6.95 (dd, J = 7.0, 7.6 Hz,
1H, -C6H4-), 7.03 (dd, J = 7.0, 7.6 Hz, 1H, -C6H4-), 7.66 (d, J = 7.6 Hz,
1H, -C6H4-). 31P{1H} NMR (109 MHz, C6D6): δ 26.8 (s). 13C{1H}
NMR (100 MHz, C6D6): δ ꢀ7.1 (s, -AlMe2), ꢀ5.8 (s, -AlMe2), 15.2 (d,
JCP = 27.0 Hz, -NiCH2-), 26.8 (s, Cy), 27.9 (d, JCP = 3.0 Hz, Cy), 28.0 (d,
JCP = 3.0 Hz, Cy), 30.3 (d, Jcp = 27.0 Hz, Cy), 33.1 (s, -NiCH2CHCH2-),
33.2 (d, Jcp = 19.0 Hz, Cy), 64.1 (d, JCP = 8.0 Hz, -NiCH2CH-), 122.0
(s, -C6H4-), 127.1 (s, -C6H4-), 128.6 (s, -C6H4-), 131.4 (s, -C6H4-), 135.6
(s, -C6H4-), 155.8 (s, -C6H4-), 198.6 (s, -CdN(AlMe2)Ni-). Anal. Calcdfor
C30H48AlClNNiP: C, 62.69; H, 8.42; N, 2.44. Found: C, 61.99; H, 8.31;
N, 2.34.
Reaction of 8 with Me2AlOTf. To a solution of 8 (19.3 mg, 0.04
mmol) in 0.5 mL of C6D6 was added Me2AlOTf (THF adduct, 10.0 μL,
0.04 mmol) at room temperature. The color of the solution changed
immediately from yellow to reddish orange to give a nickeladihydro-
pyrrole (9b) in quantitative yield.
Selected spectral data for A: 1H NMR (400 MHz, C6D6): δ 2.48 (m,
1H, CHHdC(CH3)-), 2.66 (m, 1H, CHHdC(CH3)-), 7.63 (d, J = 7.2
Hz, 1H, -C6H4-). 31P{1H} NMR (109 Hz, C6D6): δ 36.6 (s, 1P).
Selected spectral data for B: 1H NMR (400 MHz, C6D6): δ 1.80 (s, 3H,
CH2dC(CH3)-), 2.56 (m, 2H, CH2dC(CH3)CH2CH2-), 3.02 (m, 2H,
CH2dC(CH3)CH2CH2-), 4.88 (s, 1H, CHHdC(CH3)-), 4.97 (s, 1H,
CHHdC(CH3)-), 7.42 (br s, 1H, -C6H4-). 31P{1H} NMR (109 Hz,
C6D6): δ 33.0 (d, JPP = 41.5 Hz, 1P), 47.9 (d, JPP = 41.5 Hz, 1P).
Spectral data of 6 were identical to that previously reported.14c
Generation of (PCy3)Ni(η2:η2-CH2dCHCH2C6H4CtN) (8).
To a solution of Ni(cod)2 (5.5 mg, 0.02 mmol) and PCy3 (5.6 mg, 0.02
mmol) in 0.5 mL of C6D6 was added 2-allylbenzonitrile (7) (2.9 mg,
0.02 mmol) at room temperature. The color of the solution changed
immediately from orange to yellow, resulting in the quantitative forma-
tion of 8.
Isolation of 9b. To a toluene solution of 8 (289.2 mg, 0.60 mmol) was
added Me2AlOTf (THF adduct, 150 μL, 0.60 mmol) at room tempera-
ture. The color of the solution changed from yellow to red. The reaction
mixture was stirred for 15 min, and then all volatiles were removed in
vacuo to give dark orange solids. The solids were washed with hexane to
give 9b as yellow microcrystalline (355 mg, 86%). Further purification
1
was achieved by recrystallization from toluene/hexane at ꢀ20 °C. H
NMR (400 MHz, C6D6): δ ꢀ0.05 (s, 3H, -AlMe2), ꢀ0.01 (s, 3H,
-AlMe2), 0.43 (m, 1H, -Ni-CHH-), 1.00ꢀ2.00 (m, 33H, Cy), 1.10
(obscured by Cy, 1H, -Ni-CHH-), 2.19 (dd, J = 6.4, 16.0 Hz, 1H,
-C6H4CHH-), 2.57 (dd, J = 8.6, 16.0 Hz, 1H, -C6H4CHH-), 3.49 (m, 1H,
-NiCH2CH-), 6.82 (d, J = 6.8 Hz, 1H, -C6H4-), 6.97 (dd, J = 7.4, 7.6 Hz,
1H, -C6H4-), 7.02 (dd, J = 6.8, 7.4 Hz, 1H, -C6H4-), 8.04 (d, J = 7.6 Hz,
1H, -C6H4-). 31P{1H} NMR (109 MHz, C6D6): δ 24.7 (s). 13C{1H}
NMR (100 MHz, C6D6): δ ꢀ8.4 (s, -AlMe2), ꢀ6.6 (s, -AlMe2), 10.4 (d,
Isolation of 8. To a toluene solution of Ni(cod)2 (328.9 mg, 1.20
mmol) and PCy3 (336.8 mg, 1.20 mmol) was added 7 (172.0 mg, 1.20
mmol) at room temperature. The color of the solution changed
immediately from orange to yellow. The reaction mixture was stirred
for 15 min, and then all volatailes were removed in vacuo to give yellow
solids. The solids were washed with hexane to give 8 (572 mg, 99%
yield). Further purification was achieved by recrystallization from
toluene/hexane at ꢀ20 °C. 1H NMR (400 MHz, C6D6): δ 1.14ꢀ2.33
(m, 33H, Cy), 2.30 (obscured by Cy, 1H, CHHdCH-), 2.49 (dd, J =
13.0, 14.4 Hz, 1H, -C6H4CHH-), 2.67 (dd, J = 8.4, 8.8 Hz, 1H,
CHHdCH-), 3.31 (m, CH2dCH-), 3.52 (dd, J = 13.0, 12.8 Hz, 1H,
-C6H4CHH-), 6.93 (dd, J = 6.8, 6.8 Hz, 1H, -C6H4-), 7.04ꢀ7.06 (m, 2H,
-C6H4-), 8.08 (d, J = 7.2 Hz, 1H, -C6H4-). 31P{1H} NMR (109 Hz, C6D6):
J
J
CP = 32.0 Hz, -NiCH2-), 26.8 (s, Cy), 27.9 (d, JCP = 9.0 Hz, Cy), 28.0 (d,
CP = 9.0 Hz, Cy), 30.0 (s, Cy), 30.3 (s, Cy), 33.0 (d, Jcp = 19.0 Hz, Cy),
33.4 (d, JCP = 5.0 Hz, -NiCH2CHCH2-), 63.8 (d, JCP = 6.0 Hz,
-NiCH2CH-), 124.9 (s, -C6H4-), 126.9 (s, -C6H4-), 127.0 (s, -C6H4-), 131.6
(s, -C6H4-), 135.6 (d, JCP = 4.0 Hz, -C6H4-), 155.1 (s, -C6H4-), 199.5 (d,
JCP = 5.0 Hz, -CdN(AlMe2OTf)Ni-). Anal. Calcd for C31H48AlF3-
NNiO3PS: C, 54.08; H, 7.03; N, 2.03. Found: C, 51.51; H, 6.93; N, 2.17.
Reaction of 8 with TfOH. To a solution of 8 (9.6 mg, 0.02 mmol) in
0.5 mL of C6D6 was added TfOH (1.8 μL, 0.02 mmol) at room
temperature. The color of the solution immediately changed from
yellow to orange, resulting in the quantitative formation of a nickeladi-
hydropyrrole (9c).
Isolation of 9c. To a toluene solution of 8 (241.2 mg, 0.50 mmol) was
added TfOH (44.0 μL, 0.50 mmol) at room temperature. The color of
the solution changed from orange to dark red. The reaction mixture was
stirred for 20 min, and then insoluble was filtered to remove by passing
through a pad of Celite. The filtrate was concentrated in vacuo to give
yellow solids. The solids were washed with hexane to give 9c (306 mg,
97%). Further purification was achieved by recrystallization from THF/
hexane at ꢀ20 °C. 1H NMR (400 MHz, C6D6): δ 0.44 (dd, J = 8.8, 17.6
Hz, 1H, -Ni-CHH-), 0.87 (dd, J = 8.8, 8.8 Hz, 1H, -Ni-CHH-), 1.10ꢀ
2.10 (m, 33H, Cy), 1.95 (obscured by Cy, 1H, -C6H4CHH-), 2.42 (dd,
J = 8.4, 16.0 Hz, 1H, -C6H4CHH-), 2.98 (m, 1H, -NiCH2CH-), 6.67 (d,
J = 7.6 Hz, 1H, -C6H4-), 6.73 (dd, J = 7.6, 7.6 Hz, 1H, -C6H4-), 6.81 (d,
J = 7.6 Hz, 1H, -C6H4-), 6.94 (dd, J = 7.6, 7.6 Hz, 1H, -C6H4-), 9.13 (brs,
1H, -NH). 31P{1H} NMR (109 MHz, C6D6): δ 27.2 (s). 13C{1H} NMR
(100 MHz, C6D6): δ 17.4 (d, Jcp = 32.0 Hz, -NiCH2-), 26.6 (s, Cy), 27.6
(d, Jcp = 5.0 Hz, Cy), 27.7 (d, Jcp = 5.0 Hz, Cy), 29.7 (s, Cy), 30.0 (s, Cy),
32.2 (d, Jcp = 20.0 Hz, Cy), 33.0 (d, JCP = 5.0 Hz, -NiCH2CHCH2-),57.4
(d, JCP = 5.0 Hz, -NiCH2CH-),122.5 (s, -C6H4-), 126.2 (s, -C6H4-),
δ37.4 (s). 13C{1H} NMR (100 MHz, C6D6):δ27.0 (s, Cy), 28.1 (d, JCP
=
4.0 Hz, Cy), 28.2 (d, JCP = 2.0 Hz, Cy), 30.7 (s, Cy), 34.8 (d, JCP = 15.0 Hz,
Cy), 37.1 (s, CH2dCHCH2-), 46.4 (d, JCP = 4.0 Hz, CH2dCHCH2-),
69.6 (d, JCP = 11.0 Hz, CH2dCHCH2-), 117.9 (s, -C6H4-), 127.7 (s,
-C6H4-), 129.8 (s, -C6H4-), 130.6 (d, JCP = 2.0 Hz, -C6H4-), 131.0 (s, -C6H4-),
148.8 (d, JCP = 6.0 Hz, -C6H4-), 153.4 (d, JCP = 6.0 Hz, -CtN). Anal.
Calcd for C28H42NNiP: C, 69.73; H, 8.78; N, 2.90. Found: C, 68.54; H,
8.75; N, 2.95.
Reaction of 8 with AlMe2Cl. To a solution of 8 (9.6 mg, 0.02 mmol) in
0.5 mL of C6D6 was added Me2AlCl (1.04 M solution in hexane, 19.0 μL,
0.02 mmol) at room temperature. The color of the solution changed
immediately from yellow to reddish orange to give a nickeladihydro-
pyrrole (9a) in quantitative yield.
Isolation of 9a. To a toluene solution of 8 (96.5 mg, 0.20 mmol) was
added Me2AlCl (1.04 M solution in hexane, 190 μL, 0.20 mmol) at room
temperature. The color of the solution changed from yellow to reddish
orange. The reaction mixture was stirred for 10 min, and then all volatiles
were removed in vacuo to give reddish orange solids. The solids were
washed with hexane to give 9a (110 mg, 96%). Further purification was
achieved by recrystallization from toluene/hexane at ꢀ20 °C. 1H NMR
(400 MHz, C6D6): δ 0.06 (s, 3H, -AlMe2), 0.11 (s, 3H, -AlMe2), 0.92
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128.2 (s, -C6H4-), 131.7 (s, -C6H4-), 132.5 (s, -C6H4-), 154.5 (s, -C6H4-),
197.4 (s, -CNHNi-). Anal. Calcd for C29H43F3NNiO3PS: C, 55.08; H,
6.85; N, 2.21. Found: C, 55.31; H, 6.91; N, 2.27.
Reaction of 8 with TMSOTf. To a solution of 8 (9.6 mg, 0.02 mmol) in
0.5 mL of C6D6 was added TMSOTf (3.6 μL, 0.02 mmol) at room
temperature. The color of the solution immediately changed from
yellow to orange, resulting in the quantitative formation of a nickeladi-
hydropyrrole (9d).
’ ACKNOWLEDGMENT
This work was supported by a Grant-in-Aid for Scientific
Research (No. 21245028) and Encouragement for Young Scientists
(B) (No. 21750102) from MEXT. S.O. and M.O. acknowledge
NAGASE Science and Technology Foundation and the Japan
Petroleum Institute, respectively, for the Grant for Research.
Isolation of 9d. To a toluene solution of 8 (192.9 mg, 0.40 mmol) was
added TMSOTf (72.0 μL, 0.40 mmol) at room temperature. The color
of the solution changed from yellow to red. The reaction mixture was
stirred for 15 min, and then all volatiles were removed in vacuo to give
vermillion solids. The solids were washed with hexane to give 9d (278 mg,
99%). Further purification was achieved by recrystallization from toluene/
hexane at ꢀ20 °C. 1H NMR (400 MHz, C6D6): δ 0.34 (dd, J = 8.4, 11.2
Hz, 1H, -Ni-CHH-), 0.69 (s, 9H, -TMS), 0.83 (m, 1H, -Ni-CHH-),
1.20ꢀ2.40 (m, 33H, Cy), 2.05 (obscured by Cy, 1H, -C6H4CHH-), 2.49
(dd, J = 8.4, 16.4 Hz, 1H, -C6H4CHH-), 4.21 (m, 1H, -NiCH2CH-), 6.76
(d, J = 7.8 Hz, 1H, -C6H4-), 6.84 (dd, J = 7.6, 7.8 Hz, 1H, -C6H4-), 7.00
(dd, J = 7.6, 7.8 Hz, 1H, -C6H4-), 7.54 (d, J = 7.8 Hz, 1H, -C6H4-). 31P{1H}
NMR (109 MHz, C6D6): δ 24.5 (s). 13C{1H} NMR (100 MHz, C6D6):
δ 2.20 (s, -TMS), 9.9 (d, Jcp = 33.0 Hz, -NiCH2-), 27.0 (s, Cy), 28.1
(m, Cy), 30.6 (s, Cy), 33.8 (d, Jcp = 19.0 Hz, Cy), 34.3 (s, -C6H4CH2-),
61.2 (s, -NiCH2CH-), 126.2 (s, -C6H4-), 127.0 (s, -C6H4-), 127.9
(s, -C6H4-), 132.9 (s, -C6H4-), 133.7 (s, -C6H4-), 156.2 (s, -C6H4-),
199.9 (s, -CN(TMS)Ni-). Anal. Calcd for C32H51F3NNiO3PSSi: C,
54.55; H, 7.30; N, 1.99. Found: C, 55.00; H, 7.33; N, 2.10.
Reaction of 4b with HSiMe2Ph in the Presence of 1. A solution of 4b
(38.8 mg, 0.06 mmol), HSiMe2Ph (9.2 μL, 0.06 mmol) and 1 (9.4 mg, 0.06
mmol) in 0.5 mL of C6D6 was heated at 80 °C for 3 h. The yellow
suspension changed to a red solution along with precipitation of a little
amount of Ni black. Monitoring the reaction by means of 1H NMR revealed
that HSiMe2Ph and 1 were fully consumed after 3 h. Then, all volatiles were
removed in vacuo to give yellow solids. Extraction with hexane followed by
concentration under N2 atmosphere gave a silanamine (10) in 81% yield.
Catalytic Reaction of HSiMe2Ph with 1 in the Presence of TfOH. To a
solution of Ni(cod)2 (5.5 mg, 0.02 mmol) and PCy3 (5.6 mg, 0.02
mmol) in 0.5 mL of C6D6 was added 1 (31.4 mg, 0.20 mmol), TfOH
(0.9 μL, 0.01 mmol) and HSiMe2Ph (31.0 μL, 0.20 mmol) sequentially.
The solution was heated at 80 °C for 4 h. The color of the solution
changed from yellow to red with a small amount of Ni black. All volatiles
were removed in vacuo to give yellow solids. Extraction with hexane
followed by concentration under N2 atmosphere gave 10 (48mg, 84%). 1H
NMR (400 MHz, C6D6): δ 0.65 (s, 6H, -SiMe2Ph), 1.13 (s, 6H,
(CH3)2C-), 2.65 (s, 2H, -C6H4CH2-), 6.96 (dd, J = 7.4, 7.4 Hz, 1H,
-C6H4-), 7.05 (d, J = 7.6 Hz, 1H, -C6H4-), 7.10ꢀ7.28 (m, 1H of -C6H4-
and 3H of -Ph), 7.63 (d, J = 7.6 Hz, 1H, -C6H4-), 7.82 (d, J = 6.8 Hz, 2H,
-Ph). 13C{1H} NMR (100 MHz, C6D6): δ 1.4 (s, -SiMe2Ph), 27.3 (s,
(CH3)2C-), 44.3 (s, -C6H4CH2-), 46.3 (s, (CH3)2C-), 124.8 (s, -C6H4-),
126.6 (s, -C6H4-), 127.1 (s, -C6H4-), 128.0 (s, m-Ph), 129.3 (s, p-Ph),
132.1 (s, -C6H4-), 134.0 (s, o-Ph), 138.5 (s, -C6H4-), 141.0 (s, ipso-Ph),
150.2 (s, -C6H4-), 187.3 (s, -CN-). HRMS Calcd for C19H23NSi
293.1600, Found m/z 293.1595.
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’ ASSOCIATED CONTENT
S
Supporting Information. Crystallographic data (CIF)
b
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charge via the Internet at http://pubs.acs.org.
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’ AUTHOR INFORMATION
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Corresponding Author
*ogoshi@chem.eng.osaka-u.ac.jp.
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