Synthesis of neutral nickel-methyl complexes with monodentate imines and their sequential insertion of carbon monoxide and imine

Article abstract of DOI:10.1016/j.ica.2010.12.024

Neutral nickel-imine complexes of the form (NO)Ni(R)(R¹NC(H) R²) (NO = salicylaldiminato; R = CH₃, Ph; R¹ = alkyl; R² = aryl) can be prepared by the reaction of (tmeda)Ni(CH₃)₂,

Full text of DOI:10.1016/j.ica.2010.12.024

Inorganica Chimica Acta 369 (2011) 231–239
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Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Synthesis of neutral nickel–methyl complexes with monodentate imines
and their sequential insertion of carbon monoxide and imine
⇑
Carolyne Stafford, Bruce A. Arndtsen
Department of Chemistry, McGill University, 801 Sherbrooke St., W. Montreal, QC, Canada H3A 2K6
a r t i c l e i n f o
a b s t r a c t
Neutral nickel–imine complexes of the form (N^O)Ni(R)(R1N@C(H)R2) (N^O = salicylaldiminato; R = CH3,
Ph; R1 = alkyl; R2 = aryl) can be prepared by the reaction of (tmeda)Ni(CH3)2, imine and the corresponding
salicylaldiminato ligand. The addition of carbon monoxide to these complexes lead to the in situ gener-
ation of the corresponding nickel–acyl complexes. With N-methyl or N-benzyl substituted imines, these
complexes reductively eliminate the phenolic and acyl ligands to generate esters. However, the less ste-
rically encumbered 3,4-dihydroisoquinoline can couple with the nickel–acyl ligand to form 1,2-diamides
in high yield. In situ 1H NMR analysis suggests this reaction occurs via insertion of imine into the nickel-
acyl bond to form a nickel-bound amide complex.
Article history:
Available online 24 December 2010
Dedicated to Professor Robert Bergman, and
his many contributions to chemistry.
Keywords:
Nickel
Carbon monoxide
Insertion
Imine
Amide synthesis
R
O
N
O
R
N
N
O
R
Ni
O
N
O
R
Ni
N
Ni
CO
6D6
N
R1
N
O
R
O
R1
C
R1
N
15 min
R2
R2
R2
N
Ó 2010 Elsevier B.V. All rights reserved.
1. Introduction
and its replacement with a C–N single bond, which has less of a
driving force than alkene insertion [8]. In addition, stable aldimines
typically have substituents at both nitrogen and carbon, rendering
The migratory insertion reaction of multiply bonded substrates
into transition metal–carbon bonds has significant utility in syn-
thetic chemistry. This reaction has been perhaps most thoroughly
exploited with olefins, as illustrated in metal catalyzed poly(olefin)
syntheses [1]. Additionally, the migratory insertion of alkenes is a
critical step in many organic synthetic transformations (e.g. Heck
reaction [2], alkene–alkyne coupling reactions [3], reductions [4],
and many others [5]). In contrast to olefins, the use of imine
C@N double bonds in migratory insertion into late transition me-
tal–carbon bonds is more limited [6,7]. This difference may result
from a number of factors. The insertion of imines into metal–
these compounds more hindered than
nate to transition metals in a -fashion through the nitrogen lone
pair instead of via -coordination, the postulated requirement for
a-olefins, and often coordi-
r
p
insertion [9]. Despite these features, examples of both catalytic
and stoichiometric processes involving imine insertion into late
transition metal–carbon bonds have been reported [6]. These typ-
ically involve insertion to form metal-nitrogen bonded intermedi-
ates or products.
As an alternative to these approaches, both Sen and co-workers
[10] and ourselves [8] and have demonstrated that cationic Pd(II)
complexes mediate the sequential insertion of carbon monoxide
(CO) and imines to generate metal–amide chelates (Scheme 1).
carbon bonds often involves cleavage of a strong C@N
p-bond,
A
similar reaction can also occur with cationic nickel and
manganese–carbonyl complexes [11]. Notably, imine insertion
proceeds with a regiochemistry to form a new metal–carbon bond,
⇑
Corresponding author. Tel.: +1 514 398 6903; fax: +1 514 398 3797.
E-mail address: bruce.arndtsen@mcgill.ca (B.A. Arndtsen).
0020-1693/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2010.12.024

232
C. Stafford, B.A. Arndtsen / Inorganica Chimica Acta 369 (2011) 231–239
O
C
CH3
R1
O
O
CH3
O
N
O
Cl
O
O
CH3
CH3
R
O
CO
CH3
CO
rt
Pd
Cl Pd
N
L2M
R2
N
R1
4
CH3
CH3
R
L2M
R'
R2
X
L2M
R'
N
R
X
R1
X
R1
N
N
2
H
R2
O
R2
N
H
5
3
2
R'
H
H
H
1
Scheme 2. CO insertion with neutral palladium-chelated amides.
M = Pd; L2 = dppe; 3 atm CO, CHCl3, rt
M = Pd; L2 = bipy; 1 atm CO, PhBr, 70 oC
M = Ni; L2 = bipy; 1 atm CO, CH2Cl2, rt
2. Results and discussion
Scheme 1. The sequential insertion of CO and imines with cationic complexes.
2.1. Synthesis of nickel–imine complexes
Neutral imine-coordinated complexes of the form (N^O)Ni(R)
(R1N@C(H)R2) (N^O = salicylaldiminato; R = CH3; R1 = alkyl; R2 =
aryl) can be synthesised via the reaction of (tmeda)NiMe2
(tmeda = N,N,N0,N0-tetramethylethylenediamine) and the free phe-
nolic ligand in the presence of imine, in analogy to the synthesis of
related (salicylaldiminato)nickel complexes (Table 1) [16,17]. Re-
moval of solvents and washing with pentane yielded complexes
8a–l as orange powders. The 1H and 13C NMR spectra for 8a–l dis-
play a downfield shift in the monodentate imine resonances upon
and thus represent the fundamental steps in a potential CO/imine
co-polymerization. While the strong coordination of the acyl-oxy-
gen to the cationic metal center in 1 inhibits the creation of an
empty coordination site for further insertion steps, Sun and
coworkers have recently reported that neutral cobalt–carbonyl
complexes are not inhibited by chelation, and can mediate the
sequential insertion polymerization of carbon monoxide and imi-
nes to build up polyamides [12]. We have observed that the less Le-
wis acidic neutral Pd(II) complexes 2 (Scheme 2), generated via
oxidative addition of N-acyl iminium salts to Pd(0), can also under-
go further insertion of carbon monoxide to afford a transient six-
membered palladacycle 3. This intermediate lacks any stabilizing
ligand, and undergoes rapid b-hydride elimination to generate an
coordination, consistent with
g
1-binding of the imine through the
nitrogen [e.g. 8g: 1H NMR: d 8.43 (s, CH@N), 13C NMR: d 166.1
(CH@N), versus free p-Tol(H)C@NBn: 1H NMR: d 8.26 ppm (s,
CH@N), 13C NMR: d 159.3 (CH@N)] [10]. 1H-NOE NMR studies on
8g show that the nickel–methyl ligand (d ꢀ0.73) in close proximity
to both the aldimine hydrogen (d 8.43), and the isopropyl units in
the chelated salicylaldiminato ligand [d 4.16 (sept., 2H), d 1.51 (d,
6H), 1.04 (d, 6H)]. All other spectroscopic data are consistent with
the structure shown. While nickel complexes 8a–l can be isolated
in good yields, N-pentafluorophenyl- 8m and N-phenyl 8n substi-
tuted imines, were not isolable, despite being observed in situ by
1H NMR spectroscopy.1 The lower stability of these complexes is
likely the result of a weaker nickel–imine bond between these poorly
basic imines and the neutral nickel complex.
a-amide substituted ketene 4, which is in equilibrium with its
closed heterocyclic form (1,3-oxazolium-5-oxide or Münchnone,
5) [13].
The ability of neutral cobalt and palladium complexes to
mediate sequential insertion, relative to the stable cationic che-
lated-amide complexes 1, is similar to the behavior of late metal
catalysts with polar alkene monomers. In these systems, it is
established that neutral nickel and palladium catalysts are less
inhibited by functional group chelation than their cationic ana-
logs, and can mediate further insertion reactions to build up
polymers with functionalized alkenes [14]. For example, neutral
The phenyl-substituted nickel complex 9 can also be prepared
via reaction of (N^O)Ni(Ph)(PPh3) [18] (N^O = salicylaldiminato)
and 3,4-dihydroisoquinoline, with CuCl as a phosphine scavenger
(Scheme 3). Precipitation of the complex with pentane afforded a
yellow powder. The spectroscopic data observed for 9 are analo-
gous to those for the nickel–methyl complexes.
As previously noted for the analogous nickel–acetonitrile com-
plex 6 [16], imine complexes 8 decompose in benzene at ambient
temperature to generate uncoordinated imine and bis-(salicylal-
diminato)nickel (II) complexes 10 (Table 2) [19]. This decomposi-
tion is accelerated by steric bulk (entries 1 and 2), and electron
withdrawing groups (entries 4, 5) on the salicylaldiminato ligand,
as well as by polar solvents (entry 3). Notably, imine insertion into
the nickel-methyl bond is not observed under any conditions.
j
2-N,O-salicylaldiminato nickel complexes (e.g. 6) are known to
catalyze the co-polymerization of polar alkenes with substituted
norbornenes, carbon monoxide, and functional olefins [15].
a-x
These features suggest that neutral late metal complexes might
also be viable systems to mediate the sequential insertion of car-
bon monoxide and imines. However, the lower Lewis acidity in
these complexes will presumably create a less electrophilic nick-
el–acyl ligand, which we have previously postulated is important
for imine insertion into a metal–acyl bond [11b]. To probe the
ability of these neutral complexes to mediate imine insertion,
we describe below the synthesis and reactivity of the imine-coor-
dinated nickel complexes (N^O)Ni(R)(R1N@C(H)R2) (N^O = sali-
cylaldiminato; R = CH3, Ph; R1 = alkyl; R2 = aryl). These
complexes have been found to undergo rapid insertion of carbon
monoxide, followed by coupling of the nickel–acyl ligand with
sterically unencumbered cis-tethered imines, leading to the for-
mation of 1,2-diamides.
2.2. Carbon monoxide insertion with nickel complexes 8
The addition of 1 atm carbon monoxide to complexes 8a–l in
the presence of imine (3 equivalents) results in the rapid insertion
of CO to generate the analogous Ni–acyl complexes (Table 3) [20].
While these complexes are not sufficiently stable to be isolated,
in situ 1H NMR data is consistent with the structures of 11a–l as
H3C
1
1H NMR spectrum of 8m (400 MHz, C6D6) (listing distinctive signals only): d 9.80
CH3
N
(d, 2H, J = 7.7 Hz), 7.90 (s, 1H), 7.71 (d, 2H, J =7.7 Hz), 7.54 (s, 1H), 6.43 (t, 2H,J = 7.3
Hz), 4.20 (sept., 1H, J = 6.6 Hz), 3.83 (sept., 1H, J = 6.6 Hz), 2.03 (s, 3H), 1.42 (d, 3H,
J = 6.6 Hz), 1.24 (d, 3H, J = 6.6 Hz), 1.17 (d, 3H, J = 6.2 Hz), 0.90 (d, 3H, J = 6.2 Hz),
ꢀ1.04 (s, 3H). (b) 1H NMR spectrum of 8n (400 MHz, C6D6) (listing distinctive signals
only): d 9.77 (d, 2H, J = 7.7 Hz), 8.14 (s, 1H), 7.75 (d, 2H, J = 7.7 Hz), 7.56 (s, 1H), 6.42 (t,
2H, J = 7.7 Hz), 4.35 (sept., 1H, J = 6.8 Hz), 3.87 (sept., 1H, J = 6.8 Hz), 2.02 (s, 3H), 1.42
(d, 3H, J = 7.0 Hz), 1.33 (d, 3H, J = 6.2 Hz), 1.19 (d, 3H, J = 6.6 Hz), 0.94 (d, 3H, J = 6.6
Hz), ꢀ0.96 (s, 3H).
Ni
O
N
6

C. Stafford, B.A. Arndtsen / Inorganica Chimica Acta 369 (2011) 231–239
233
Table 1
The synthesis of (
Table 2
j
2-N,O-salicylaldiminato)nickel–imine complexes.
Formation of bis(salicylaldiminato)nickel complexes 10a–d.
R3
R2
H
R3
H
N
CH3
N
N
Bn
H
R4
Ni
H3C
Ni
CH3
N
N
CH3
N
R4
C6H6
r.t., 3 h
R1
N
O
OH
R2
CH3
CH3
p-Tol
H3C
+
Ni
R1
R1
N
N
O
O
N
H3C
rt
O
R1
Ni
C6D6
- ethane
R2
R1
Bn
N
-
7, 8a-o
Yield (%)a
R2
R1
R2
H
p-Tol
H
Cpd
Imine
R2
8e-h
7
Ph
60
N
10a (R1 = Ph, R2 = H)
b (R1 = H, R2 = H)
c (R1 = H, R2 = F)
8a
Ph
H
91
Me
N
N
N
N
N
N
N
N
d (R1 = H, R2 = NO2)
p-Tol
p-Tol
p-Tol
p-Tol
p-Tol
p-Tol
p-Tol
p-Tol
H
Me
Entry
Cpd
R1
R2
Time (h)
Yield 10 (%)a
8b
8c
8d
8e
8f
H
H
H
Ph
H
H
H
H
81
73
83
88
76
74
87
1
2
3
4
5
8e
8f
8f
8g
8h
Ph
H
H
H
H
H
H
H
F
6
61
5
39
10
84b
96
H
Me
88b,c
91
F
NO2
95
H
Me
General conditions: 0.02 M of 9 in d6-benzene at 25 °C, monitored in situ by 1
H
a
NO2
H
NMR.
b
Isolated yield.
H
Bn
c
In d3-acetonitrile.
H
Bn
H
Ni–COCH3 singlets at d 1.92 ppm (11j) and d 2.49 ppm (12b) in a
7–1 ratio. Complex 11j also contains a coordinated monodentate
imine ligand [1H NMR: d 8.63 (s, 1H)], which 1H-NOE NMR studies
confirm is cis to the nickel-acyl ligand. The CO-coordinated com-
plex 12b is observed regardless of the monodentate imine in the
starting material, consistent with CO occupying the fourth coordi-
nation site.
The ratio of complexes 11 and 12 varies with the coordination
ability of the imine, and the steric and electronic properties of
the salicylaldiminato ligand (Table 3). Increasing the steric bulk
on the salicylaldiminato ligand favors the generation of 12 (e.g. en-
tries 1, 5, 9). However, electron withdrawing substituents on the
ligand framework, which presumably increases the Lewis acidity
of the metal center, favors imine coordination (entries 3, 4). In gen-
eral, the cis-tethered imine dihydroisoquinoline more strongly fa-
vors imine coordination relative to the more sterically
encumbered trans-disubstituted imines (entries 9–12). As antici-
pated from a dynamic equilibrium between 11 and 12, the ratio
of imine coordinated complex 11 increased with the addition of ex-
cess imine (entries 13–15).
H
Bn
8g
8h
F
H
Bn
NO2
H
N
8i
Ph
H
H
89
81
78
92
–
8j
H
N
N
8k
8l
H
F
H
NO2
H
N
8m
Ph
C6F5
N
N
p-Tol
p-T o l
H
Ph
8n
Ph
H
–
H
a
Isolated yields.
2.3. Imine insertion with neutral nickel–acyl complexes
The in situ generation of nickel–acyl imine complexes 11a–l
provides the ability to compare their insertion propensity to the
analogous cationic nickel complexes 1, which have been previously
shown to undergo insertion of imine into the nickel–acyl bond to
afford chelated amides (Scheme 1). As shown in Table 4, the neu-
tral nickel-acyl complexes of N-methyl and N-benzyl substituted
imines 11a–h do not undergo imine insertion, and instead elimi-
nate the acyl and phenolic salicylaldiminato ligands over the
course of 5 h at ambient temperature to form esters 13a–d (Table
4). The latter are observed along with uncoordinated imine and the
bis(salicylaldiminato)nickel complexes 10 [21]. This reaction oc-
curs regardless of the substituents on the chelating salicylaldimi-
nato ligand. The addition of excess imine is found to partially
inhibit the formation of esters 13 (entries 9 and 10), suggesting
Ph3P
Ni
Ph
N
N
Ph
N
CuCl
C6H6, r.t.
30 min
Ni
O
+
N
O
9
Scheme 3. The synthesis of the j
2-N,O-salicylaldiminatonickel(II) complex 9.
shown, in equilibrium with CO-coordinated complexes 12a–d. For
example, monitoring the reaction of 8j by 1H NMR spectroscopy
reveals the disappearance of the Ni–CH3 resonance after 15 min
at ambient temperature, along with the appearance of two new

234
C. Stafford, B.A. Arndtsen / Inorganica Chimica Acta 369 (2011) 231–239
Table 3
Table 4
In situ Generation of nickel–acyl complexes.a
Ester Formation from imine nickel–acyl complexes.a
3 O
R3
H
R4
R1
R
N
H
R3
N
O
H
R3
N
Ni
N
CH3
N
OC
CH3
CH3
O
CH3
N
R4
R4
H
Ni
Ni
Ni
N
O
O
N
p-Tol
R3
H
H3C
R1
O
N
O
O
N
O
N
CO
N
1 atm CO
C6D6
+
Ni
1 atm CO
C6D6
15 min, rt
N
+
O
R1
R1
R3
H
R1
p-Tol
5 h, rt
R4
R2
8a-l
R2
R2
R2
R2
8a-h
11a-l
12a (R1 = Ph, R2 = H)
b (R1 = H, R2 = H)
c (R1 = H, R2 = F)
13a (R1 = Ph, R2 = H)
b (R1 = H, R2 = H)
c (R1 = H, R2 = F)
10a-d
d (R1 = H, R2 = NO2)
d (R1 = H, R2 = NO2)
Entry
1
Cpd
R1
R2
H
Imine
[Imine] (M)
0.15
Ratio 11:12b
Entry
R1
R2
R3
[Imine] (M)
Yield 13 (%)b
Yield 10b (%)
8a
8b
8c
8d
8e
8f
Ph
1.2:1
Me
1
2
3
4
5
6
7
8
9
10
Ph
H
H
H
Ph
H
H
H
H
H
H
H
F
NO2
H
H
F
NO2
H
H
Me
0.15
0.15
0.15
0.15
0.15
0.15
0.15
0.15
2.5
89
86
84
41
90
87
78
76
33
40
–
N
N
N
N
N
N
N
N
Me
Me
Me
Bn
Bn
Bn
Bn
Me
Bn
13
13
42
–
11
21
23
62
56
p-Tol
p-Tol
p-Tol
p-Tol
p-Tol
p-Tol
p-Tol
p-Tol
H
Me
2
3
4
5
6
7
8
H
H
0.15
0.15
0.15
0.15
0.15
0.15
0.15
1.9:1
7.8:1
5.5:1
1.2:1
2.0:1
3.1:1
3.2:1
H
Me
H
F
H
Me
2.5
H
NO2
H
a
1 atm of CO at 25 °C in d6-benzene with 0.05 M 8.
Yields determined by in situ 1H NMR analysis.
b
H
Bn
Ph
H
H
Bn
ated nickel-acyl complex 11j in the presence of 3,4-dihydroiso-
quinoline forms only small amounts of ester 13a (14%, entry 1).
In addition, a second organic product is observed forming in 77%
yield, which has been characterized to be the 1,2-diamide 14.
1,2-Diamide 14 formation presumably arises via the formation of
an amide-bound nickel complex such as 16, which can dispropor-
tionate to generate 14 and the observed nickel complex 10b (80%
yield). This disproportionation is analogous to established bimolec-
ular coupling of nickel-alkyl ligands to form alkanes [22]. The other
3,4-dihydroisoquinoline complexes 8i,k,l show similar results,
with each forming 1,2-diamide 14 as the major product. The nick-
el-phenyl substituted complex 9 also forms the benzoyl-substi-
tuted diamide 15 (entry 9).
In order to further probe for the intermediacy of the imine
insertion product 16 in diamide formation, the reaction of 8j was
monitored in situ by 1H NMR spectroscopy in d6-benzene. This
shows the build-up of an intermediate to a maximum of 30% yield
over the course of the reaction. This compound displays a new
methyl resonance at d 0.65 (s, 3H), and along with signals for both
the salicylaldiminato and dihydroisoquinoline units.2 However, the
methine hydrogen in the dihydroisoquinoline is shifted upfield (d
H
H
Bn
8g
8h
H
F
H
Bn
H
NO2
H
N
9
8i
Ph
H
H
0.15
0.15
0.15
0.15
2.5
5.4:1
7.3:1
11.5:1
6.9:1
>20:1
10
11
12
13
8j
H
N
N
8k
8l
H
F
H
NO2
H
N
8b
H
Me
N
N
p-Tol
p-Tol
H
Bn
14
15
8f
8j
H
H
H
H
2.5
2.5
>20:1
>20:1
5.42, from d 8.63 in 8j), suggesting reduction of the C@N
p-bond.
H
N
The latter is similar to related signals of imine insertion products
[11], and consistent with the preliminary assignment of this inter-
mediate as the nickel-chelated amide complex 16j. Further monitor-
ing the reaction by 1H NMR spectroscopy shows the disappearance
of 16j coincides with the growth of 14. The disproportionation of
complex 16j to for the diamide could proceed via a number of path-
ways, including radical, ionic or bimetallic mechanisms. While at
present we have no conclusive data on the mechanism of 1,2-dia-
mide formation, it is notable that the addition of radical traps [23]
does not alter product distribution, arguing against a radical path-
way (Scheme 4).
a
General conditions: 0.05 M 8, 1 atm of CO at 25 °C in d6-benzene, 15 min, rt.
In situ ratio measured by 1H NMR.
b
that the formation of esters 13 may proceed via the equilibrium
generation CO-coordinated complex 12.
The lack of imine insertion with in situ generated nickel-acyl
complexes 11a–l may result from the lower electrophilicity of
the acyl ligand inhibiting reaction with the imine [11]. However,
it is also plausible that these bulky trans-disubstituted imines sim-
ply cannot complete with the less sterically encumbered phenolic
unit for coupling with the nickel–acyl ligand. In considering the
latter, we postulated that the less sterically encumbered cis-teth-
ered imines in 11i–l may be able to more effectively complete with
ester formation. As shown in Table 5, the reaction of in situ gener-
The generation of 1,2-diamides 14 suggests that, provided the
imine is sufficiently nucleophilic to compete with ester reductive
NMR data for complex 16j: 1H NMR (400 MHz, C6D6): d 7.61 (s, 1H, HC@N), 5.42
(s, 1H, NiC(H)NCOCH3), 4.05 (m, 2H, CH(CH3)2), 2.35-2.20 (m, 2H, NCH2CH2), 2.10-
1.97 (m., 2H, NCH2CH2), 1.43 (d, 3H, CH(CH3)2), 1.28 (d, 3H, CH(CH3)2), 1.14–1.10 (m,
6H, CH(CH3)2), 0.65 (s, 3H, NiC(H)NCOCH3).
2

C. Stafford, B.A. Arndtsen / Inorganica Chimica Acta 369 (2011) 231–239
235
Table 5
Imine Insertion with neutral nickel–acyl complexes.a
N
R
Ni
O
O
O
N
R
OC
R1
N
O
R
Ni
Ni
CO
O
N
CO
N
8i-l, 9
R1
N
R1
R2
+
12
R2
11
R2
N
R
N
O
N
O
O
N
O
O
N
Ni
N
Ni
+
R
R
O
N
O
R
O
R1
R1
N
R2
R2
14 (R = CH3)
15 (R = Ph)
13
16
10a-d
Entry
Cpd
R1
R2
[Imine] (M)
Yield 14 (15) (%)b
Yield 13 (%)
Yield 10 (%)
1
2
3
4
5
6
8j
8i
8k
8l
8j
8i
8j
8j
9
H
Ph
H
H
H
Ph
H
H
H
H
F
NO2
H
H
H
H
H
0.15
0.15
0.15
0.15
0.50
0.50
0.15
0.15
0.50
77
74
75
82
97
94
63
40
25
14
15
15
15
3
80
–
c
85
84
95
c
5
–
7d
8e
9
28
53
14
72
f
–
Ph
78
a
b
c
d
e
f
General conditions: 1 atm of CO at 25 °C in d6-benzene with 0.05 M of 8.
1H NMR yield.
Nickel complex is paramagnetic.
3 atm CO.
d3-Acetonitrile.
Precipitates in acetonitrile.
elimination, sequential CO/imine insertion is viable with neutral
nickel complexes. It is notable that diamide formation, and the
in situ generation of complex 16j, are rapid relative to imine inser-
tion with cationic palladium complexes (70 °C, 6 h) and similar in
rate to what has been observed with cationic nickel complexes
[8,11a]. The addition of excess imine increases the yield of diamide
14 (Table 5, entries 5, 6). Considering the dynamic equilibrium
between 11 and 12, this data suggests that imine insertion and
1,2-diamide product forms via imine-coordinated complexes 11.
Consistent with the latter, both increased CO pressure (entry 7),
or more coordinating solvents (entry 8) favor reductive elimination
to generate esters 13.
is a viable process, and that inhibition of disproportionation could
allow these products to be used in subsequent chemistry.
4. Experimental section
All manipulations were carried out in dried glassware under a
dry, dioxygen-free (O2), dinitrogen (N2) atmosphere, using stan-
dard Schlenk or glovebox techniques and a Vacuum Atmosphere
553-2 drybox. Unless otherwise noted, all reagents were purchased
from commercial sources and used without purification: carbon
monoxide (Matheson, 99.98%), 9,10-dihydroanthracene (Aldrich,
97%), benzyl benzoate (Aldrich, 99 + %). All solvents were freshly
distilled and de-gassed before use and stored under nitrogen over
activated molecular sieves. Diethyl ether was distilled using so-
dium benzophenone. Pentane, benzene and toluene were distilled
using CaH2. Acetonitrile was distilled using P4O10. Deuterated sol-
vents were dried as their protonated analogs, but vacuum
3. Conclusions
In conclusion, we have found that neutral nickel complexes of
the form (N^O)Ni(R)(R2(H)C@NR1) can be prepared, and undergo
rapid insertion of carbon monoxide to afford the analogous nick-
el-acyl complexes. The latter is in dynamic equilibrium with the
CO-coordinated (N^O)Ni(COCH3)(CO). The reductive elimination
of the nickel–acyl and -phenolic ligands to form esters is the dom-
inant reaction with bulky trans-disubstituted imines. However,
with the cis-substituted 3,4-dihydroisoquinoline, imine insertion
is quite rapid, leading to the formation of an intermediate (16)
which ultimately disproportionates to form 1,2-diamides. Overall,
this suggests that imine insertion into neutral nickel–acyl bonds
N
O
CH3
N
O
1 atm
CO
O
O
N
N
N
O
Ni
CH3
H3C
O
N
Ni
H3C
O
+
+
C6D6
r.t.
N
9,10-dihydro-
anthracene
(1 equiv.)
14
79%
10b
75%
13b
20%
8j
Scheme 4. Reaction of 8j with CO in the presence of 9,10-dihydroanthracene.

236
C. Stafford, B.A. Arndtsen / Inorganica Chimica Acta 369 (2011) 231–239
transferred from the drying agent. Tolualdimines [24], 3,4-dihy-
droisoquinoline [25], (tmeda)Ni(CH3)2 [26], and (6-phenyl-2-
((2,6-diisopropylphenyl)iminomethyl)phenoxide)Ni(Ph)(PPh3) [19]
were prepared via literature procedures. Salicylaldimines [16,19]
and their salicylaldehyde precursors were also prepared as
described in the literature.
Nuclear magnetic resonance (NMR) characterization was ob-
tained on JEOL 270 MHz, Varian Mercury 200 MHz, 300 MHz,
400 MHz and Varian Unity 500 MHz spectrometers. Electrospray
ionization-high resolution mass spectrometry (ESI-HRMS) analyses
were preformed by Alain Lesimple, Ph.D. at the Department of
Medicine, Mass Spectrometry Unit, McGill University, Montréal,
Canada. 10b [16], 14 and 15 [27] are previously reported
compounds.
ESI-HRMS: calculated for C29H37N2ONi+ (M+H+) 487.22518;
found 487.22539.
4.1.4. (4-Fluoro-2-((2,6-diisopropylphenyl)iminomethyl)phenoxide)-
Ni(CH3)(N-methyltolualdimine) (8c)
Yield: 73%. 1H NMR (300 MHz, C6D6): d 9.41 (d, 2H, JHH = 8.2 Hz),
7.37 (s, 1H), 7.07–6.98 (m, 6H), 6.80–6.72 (m, 2H), 6.57 (dd, 1H,
JHH = 9.2 Hz, JHF = 3.0 Hz), 4.16 (sept., 1H, JHH = 6.9 Hz), 3.97 (sept.,
1H, JHH = 6.9 Hz), 3.56 (s, 3H), 2.04 (s, 3H), 1.51 (d, 3H, JHH = 6.9 Hz),
1.30 (d, 3H, JHH = 6.9 Hz), 1.14 (d, 3H, JHH = 6.9 Hz), 1.02 (d, 3H,
JHH = 6.9 Hz), ꢀ1.09 (s, 3H).
13C NMR (300 MHz, C6D6): d 165.9, 165.1, 165.0, 154.2, 151.2,
149.8, 142.0, 140.9 (d, JCF = 13.4 Hz), 131.7, 131.0, 129.3, 126.5,
123.8 (d, JCF = 6.9 Hz), 123.5 (d, JCF = 12.0 Hz), 123.1, 122.8, 117.9
(d, JCF = 7.8 Hz), 116.2 (d, JCF = 21.2 Hz), 50.3, 28.5, 28.4, 25.1,
24.8, 23.3, 23.1, 21.4, ꢀ10.9.
4.1. General procedure for the synthesis of nickel complexes 7 and 8
19F NMR (400 MHz, C6D6): d ꢀ137.9.
ESI-HRMS: calculated for C29H36N2ONiF+ (M+H+) 505.21554;
found 505.21597.
(tmeda)Ni(CH3)2 (50.0 mg, 0.244 mmol) was dissolved in a
20 mL scintillation vial in benzene (5 mL) to give a yellow brown
solution. In a separate vessel, imine (0.732 mmol) and salicylaldi-
mine (0.244 mmol) were dissolved in benzene (10 mL) and the
mixture was added to the nickel solution, dropwise, while stirring.
The resulting dark red–brown mixture was left to stir at ambient
temperature for 3 h. The solution was then filtered through Celite,
the filtrate concentrated in vacuo, and the solid triturated with
pentane (ca. 5 mL). The orange solid was collected by filtration
and washed with pentane (3 ꢁ 2 mL) to afford orange powder
product.
4.1.5. (4-Nitro-2-((2,6-diisopropylphenyl)iminomethyl)phenoxide)-
Ni(CH3)(N-methyltolualdimine) (8d)
Yield: 83%. 1H NMR (500 MHz, C6D6): d 9.29 (d, 2H, JHH = 7.8 Hz),
1
2
7.96 (s, 1H), 7.88 (dd, 1H, JHH = 9.6 Hz, JHH = 2.7 Hz), 7.22 (s, 1H),
7.09–6.92 (m, 6H), 6.46 (d, 1H, JHH = 9.1 Hz), 4.02 (sept, 1H,
JHH = 6.9 Hz), 3.79 (sept, 1H, JHH = 6.9 Hz), 3.42 (s, 3H), 2.03 (s,
3H), 1.48 (d, 3H, JHH = 6.9 Hz), 1.27 (d, 3H, JHH = 6.9 Hz), 1.08 (d,
3H, JHH = 6.9 Hz), 0.99 (d, 3H, JHH = 6.9 Hz), ꢀ1.05 (s, 3H).
13C NMR (500 MHz, C6D6): d 171.7, 166.6, 166.1, 161.5, 148.9,
142.4, 140.4, 140.3, 136.2, 131.9, 131.3, 130.7, 129.3, 129.2,
128.7, 128.4, 128.2, 128.0, 127.8, 126.7, 123.6, 123.5, 122.5,
118.4, 49.8, 48.0, 28.5, 28.4, 25.0, 24.6, 23.2, 22.9, 21.3, 21.2–10.2.
ESI-HRMS: calculated for C29H36N3O3Ni+ (M+H+) 532.21090;
found 532.21047.
4.1.1. (6-Phenyl-2-((2,6-diisopropylphenyl)iminomethyl)phenoxide)-
Ni(CH3)(pyridine) (7)
Yield: 60%. 1H NMR (400 MHz, C6D6): d 8.43 (d, 2H, JHH = 8.2 Hz),
7.57 (s, 1H), 7.40–7.38 (m, 3H), 7.31–6.88 (m, 7H), 6.59 (br, 1H),
6.51 (t, 1H, 2JHH = 7.3 Hz), 6.13 (s, 2H), 4.20 (sept., 2H, JHH = 6.6 Hz),
1.49 (d, 6H, JHH = 6.6 Hz), 1.06 (d, 6H, JHH = 6.6 Hz), ꢀ0.71 (s, 3H).
13C NMR (500 MHz, C6D6): d 166.4, 165.2, 151.8, 150.1, 141.1,
140.6, 135.4, 134.5, 133.8, 133.3, 131.8, 129.8, 127.4, 126.4,
125.6, 123.5, 122.9, 120.6, 114.0, 28.5, 24.8, 23.1, ꢀ7.5.
4.1.6. (6-Phenyl-2-((2,6-diisopropylphenyl)iminomethyl)phenoxide)-
Ni(CH3)(N-benzyltolualdimine) (8e)
Yield: 88%. 1H NMR (500 MHz, C6D6): d 9.57 (d, 2H, JHH = 7.3 Hz),
7.57 (s, 1H), 7.51 (s, 2H), 7.33 (d, 1H, JHH = 7.3 Hz), 7.10–7.02 (m,
11H), 6.93 (d, 2H, JHH = 6.4 Hz), 6.85 (d, 2H, JHH = 6.9 Hz), 6.43 (t,
4.1.2. (6-Phenyl-2-((2,6-diisopropylphenyl)iminomethyl)phenoxide)-
Ni(CH3)(N-methyltolualdimine) (8a)
2
Yield: 91%. 1H NMR (300 MHz, C6D6): d 9.47 (d, 2H, JHH = 8.2 Hz),
7.61 (s, 1H), 7.55–7.52 (m, 2H), 7.35 (d, 1H, JHH = 5.5 Hz), 7.10–6.89
(m, 9H), 6.86 (d, 1H, JHH = 1.7 Hz), 6.45 (t, 1H, JHH = 7.7 Hz), 4.22
(sept., 1H, JHH = 6.9 Hz), 4.02 (sept., 1H, JHH = 6.9 Hz), 3.35 (s, 3H),
2.03 (s, 3H), 1.51 (d, 3H, JHH = 6.9 Hz), 1.35 (d, 3H, JHH = 6.9 Hz),
1.19 (d, 3H, JHH = 6.9 Hz), 1.04 (d, 3H, JHH = 6.9 Hz), ꢀ1.09 (s, 3H).
13C NMR (300 MHz, C6D6): d 166.2, 165.4, 165.2, 149.9, 142.0,
141.2, 141.0, 140.7, 134.5, 133.9, 133.4, 131.8, 130.8, 129.8,
129.3, 127.3, 126.4, 126.0, 123.6, 123.4, 120.6, 114.0, 50.1, 28.5,
28.4, 25.3, 24.9, 23.4, 23.1, 21.5, ꢀ11.6.
1H, JHH = 7.3 Hz), 5.14 (d, 1H, JHH = 15.1 Hz), 4.82 (d, 1H,
2JHH = 15.1 Hz), 4.03 (sept., 2H, JHH = 6.4 Hz), 2.03 (s, 3H), 1.42 (d,
2
2
3H, JHH = 6.9 Hz), 1.40 (d, 3H, JHH = 6.9 Hz), 1.19 (d, 3H,
JHH = 6.9 Hz), 1.06 (d, 3H, JHH = 6.9 Hz), ꢀ1.10 (s, 3H).
13C NMR (500 MHz, C6D6): d 166.1, 165.0, 164.8, 161.1, 149.8,
142.0, 141.1, 140.9, 135.7, 134.3, 133.7, 133.6, 132.0, 130.9,
130.6, 129.9, 129.4, 129.2, 128.6, 127.9, 127.4, 126.9, 126.3,
125.8, 123.4, 123.3, 120.3, 113.7, 65.7, 65.1, 28.3, 25.2, 24.9, 23.3,
23.1, 22.6, 21.4, 21.2, ꢀ11.1.
ESI-HRMS: calculated for C41H45N2ONi+ (M+H+) 639.28774;
found 639.28799.
ESI-HRMS: calculated for C35H41N2ONi+ (M+H+) 563.25614;
found 563.25585.
4.1.7. (2-((2,6-Diisopropylphenyl)iminomethyl)phenoxide)Ni(CH3)(N-
benzyltolualdimine) (8f)
4.1.3. (2-((2,6-Diisopropylphenyl)iminomethyl)phenoxide)Ni(CH3)(N-
methyltolualdimine) (8b)
Yield: 76%. 1H NMR (500 MHz, C6D6): d 9.39 (d, 2H, JHH = 7.8 Hz),
7.55 (s, 1H), 7.37 (d, 1H, JHH = 6.9 Hz), 7.13–6.96 (m, 11H), 6.92 (d,
2H, JHH = 6.4 Hz), 6.42 (t, 1H, JHH = 6.9 Hz), 5.40 (d, 1H,
Yield: 81%. 1H NMR (300 MHz, C6D6): d 9.41 (d, 2H, JHH = 8.0 Hz),
7.58 (s, 1H), 7.09–6.99 (m, 8H), 6.92 (d, 1H, JHH = 7.0 Hz), 6.40 (t,
1H, JHH = 7.0 Hz), 4.22 (sept., 1H, JHH = 7.0 Hz), 4.04 (sept., 1H,
JHH = 7.0 Hz), 3.61 (s, 3H), 2.05 (s, 3H), 1.53 (d, 3H, JHH = 6.6 Hz),
1.31 (d, 3H, JHH = 7.0 Hz), 1.17 (d, 3H, JHH = 7.0 Hz), 1.03 (d, 3H,
JHH = 6.6 Hz), ꢀ1.09 (s, 3H).
2
2JHH = 14.2 Hz), 4.97 (d, 1H, JHH = 14.2 Hz), 4.00 (sept., 1H,
2
2JHH = 6.9 Hz), 3.94 (sept., 1H, JHH = 6.9 Hz), 2.03 (s, 3H), 1.34 (d,
2
2
3H, JHH = 6.9 Hz), 1.32 (d, 3H, JHH = 6.9 Hz), 1.13 (d, 3H,
JHH = 6.9 Hz), 1.05 (d, 3H, JHH = 6.9 Hz), ꢀ1.27 (s, 3H).
13C NMR (300 MHz, C6D6): d 168.4, 166.1, 165.8, 150.1, 141.8,
141.2, 141.0, 134.3, 134.1, 131.9, 131.0, 129.3, 126.4, 123.6,
123.4, 122.9, 119.9, 113.7, 50.3, 28.5, 28.4, 25.2, 24.8, 23.3, 23.1,
21.4, ꢀ11.2.
13C NMR (500 MHz, C6D6): d 168.1, 166.1, 165.4, 149.8, 141.8,
141.1, 140.9, 136.6, 134.2, 134.0, 132.1, 131.0, 130.4, 129.4,
129.1, 128.7, 126.9, 126.2, 123.4, 123.2, 122.8, 119.8, 113.6, 66.4,
28.2, 25.2, 25.0, 23.3, 23.2, 21.4, ꢀ9.9.

C. Stafford, B.A. Arndtsen / Inorganica Chimica Acta 369 (2011) 231–239
237
ESI-HRMS: calculated for C35H41N2ONi+ (M+H+) 563.25689;
found 563.25669.
4.1.12. (4-Fluoro-2-((2,6-diisopropylphenyl)iminomethyl)phenoxide)-
Ni(CH3)(3,4-dihydroisoquinoline) (8k)
Yield: 78%. 1H NMR (500 MHz, C6D6): d 8.39 (s, 1H), 7,33 (s, 1H),
1
2
7.10–7.05 (m, 3H), 6.90 (dt, 1H, JHH = 4.6 Hz, JHF = 1.4 Hz), 6.83
1
2
4.1.8. (4-Fluoro-2-((2,6-diisopropylphenyl)iminomethyl)phenoxide)-
Ni(CH3)(N-benzyltolualdimine) (8g)
(dt, 1H, JHH = 8.7 Hz, JHF = 1.4 Hz), 6.76–6.70 (m, 2H), 6.57 (dd,
1
2
1H, JHH = 8.9 Hz, JHF = 3.2 Hz), 6.51 (d, 1H, JHH = 6.9 Hz), 6.46 (d,
1H, JHH = 7.3 Hz), 4.10 (sept., 2H, JHH = 6.9 Hz), 3.73 (t, 2H,
JHH = 7.8 Hz), 2.08 (t, 2H, JHH = 7.8 Hz), 1.50 (d, 6H, JHH = 6.9 Hz),
1.03 (d, 6H, JHH = 6.9 Hz), ꢀ0.73 (s, 3H).
Yield: 74%. 1H NMR (200 MHz, C6D6): d 9.38 (d, 2H, JHH = 7.3 Hz),
7.34 (s, 1H), 7.06–7.00 (m, 11H), 6.80–6.72 (m, 2H), 6.57 (d, 1H,
JHH = 7.3 Hz), 5.32 (d, 1H, 2JHH = 14.3 Hz), 4.91 (d, 1H,
2JHH = 14.3 Hz), 3.91 (sept., 2H, JHH = 7.3 Hz), 2.03 (s, 3H), 1.31 (t,
13C NMR (500 MHz, C6D6): d 165.1, 164.6, 164.3, 153.5, 151.7,
150.0, 140.8, 135.6, 131.7, 127.1 (d, JCF = 24.5 Hz), 126.4, 123.7,
123.6, 123.5, 123.0, 122.8 (d, JCF = 24.0 Hz), 118.0 (d, JCF = 8.2 Hz),
116.3 (d, JCF = 21.6 Hz), 49.7, 29.1, 28.4, 25.5, 24.7, 24.3, 23.6,
23.1, ꢀ9.0.
2
6H, JHH = 7.7 Hz), 1.10 (d, 3H, JHH = 6.6 Hz), 1.05 (d, 3H,
2JHH = 6.6 Hz), ꢀ1.26 (s, 3H).
13C NMR (300 MHz, C6D6): d 165.5, 165.1, 164.7, 153.5, 151.7,
149.6, 141.9, 140.8 (d, JCF = 28.7 Hz), 136.5, 132.0, 131.0, 130.4,
129.1, 128.7, 128.4, 126.3, 123.7, 123.3 (d, JCF = 17.7 Hz), 122.8 (d,
JCF = 24.4 Hz), 117.7, 116.2 (d, JCF = 21.1 Hz), 66.4, 28.2, 25.1, 24.9,
23.3, 23.2, 21.4, ꢀ9.8.
19F NMR (400 MHz, C6D6): d ꢀ132.6.
ESI-HRMS: calculated for C29H33FN2ONi+ (M+) 502.19304; found
502.19362.
19F NMR (400 MHz, C6D6): d ꢀ132.9.
ESI-HRMS: calculated for C35H40N2ONiF+ (M+H+) 581.24635;
found 581.24727.
4.1.13. (4-Nitro-2-((2,6-diisopropylphenyl)iminomethyl)phenoxide)-
Ni(CH3)(3,4-dihydroisoquinoline) (8l)
Yield: 92%. 1H NMR (500 MHz, C6D6): d 8.21 (s, 1H), 8.04 (d, 1H,
JHH = 9.2 Hz), 7.98 (s, 1H), 7.18–7.02 (m, 4H), 6.84 (t, 1H,
JHH = 6.9 Hz), 6.71 (t, 1H, JHH = 7.3 Hz), 6.50–6.45 (m, 3H), 3.96
(sept., 2H, JHH = 6.4 Hz), 3.59 (t, 2H, JHH = 7.8 Hz), 2.03 (t, 2H,
JHH = 8.2 Hz), 1.47 (d, 6H, JHH = 6.4 Hz), 1.00 (d, 6H, JHH = 6.4 Hz),
ꢀ0.70 (s, 3H).
4.1.9. (4-Nitro-2-((2,6-diisopropylphenyl)iminomethyl)phenoxide)-
Ni(CH3)(N-benzyltolualdimine) (8h)
Yield: 87%. 1H NMR (300 MHz, C6D6): d 9.31 (d, 2H, JHH = 8.2 Hz),
7.95–7.90 (m, 2H), 7.32–7.30 (m, 3H), 7.14–6.94 (m, 9H), 6.40 (d,
2
1H, JHH = 10.4 Hz), 4.98 (d, 1H, JHH = 14.0 Hz), 4.77 (d, 1H,
13C NMR (500 MHz, C6D6): d 171.5, 166.1, 164.8, 149.2, 140.4,
136.2, 135.5, 132.1, 131.9, 128.7, 127.7, 127.2, 127.1, 126.8,
123.6, 122.5, 118.5, 49.6, 28.5, 25.4, 24.6, 23.1, ꢀ8.2.
ESI-HRMS: calculated for C29H33N3NiO3+ (M+) 529.18754; found
529.18743.
2JHH = 14.0 Hz), 3.78 (sept., 1H, JHH = 6.9 Hz), 3.69 (sept., 1H,
JHH = 6.9 Hz), 2.01 (s, 3H), 1.32–1.26 (m, 6H), 1.03 (d, 3H,
JHH = 6.9 Hz), 0.99 (d, 3H, JHH = 6.9 Hz), ꢀ1.19 (s, 3H).
13C NMR (300 MHz, C6D6): d 171.6, 166.2, 148.9, 142.6, 140.6,
140.3, 136.2, 131.9, 131.7, 131.0, 130.4, 129.3, 128.8, 128.7,
127.9, 126.7, 123.6, 123.5, 122.6, 118.4, 66.7, 28.4, 25.1, 24.9,
23.4, 23.3, 21.5, ꢀ9.2.
4.2. Synthesis of complex 9
ESI-HRMS: calculated for C35H40N3O3Ni+ (M+H+) 608.24184;
found 608.24177.
(6-Phenyl-2-((2,6-diisopropylphenyl)iminomethyl)phenox-
ide)Ni(Ph)(PPh3) (150.0 mg, 0.199 mmol) and 3,4-dihydroisoquin-
oline (31.4 mg, 0.239 mmol) were dissolved in benzene (ca.
10 mL). In a second vessel, a slurry of CuCl (29.6 mg, 0.239 mmol)
in benzene (ca. 2 mL) was prepared, and added to the mixture with
stirring. After 30 min at room temperature, the solution was fil-
tered through Celite. The filtrate was concentrated in vacuo, then
dissolved in minimal pentane for crystallization at ꢀ40 °C. Yellow
crystals were then collected by filtration and washed with cold
pentane (3 ꢁ 2 mL) (104.2 mg, 84% yield).
4.1.10. (6-Phenyl-2-((2,6-diisopropylphenyl)iminomethyl)-
phenoxide)Ni(CH3)(3,4-dihydroisoquinoline) (8i)
Yield: 89%. 1H NMR (400 MHz, C6D6): d 8.27 (s, 1H), 7.59–7.57
1
2
(m, 3H), 7.41 (dd, 2H, JHH = 4.9 Hz, JHH = 2.2 Hz), 7.14–7.05 (m,
3H), 6.92–6.72 (m, 6H), 6.52–6.47 (m, 3H), 4.18 (sept., 2H,
JHH = 6.9 Hz), 3.58 (t, 2H, JHH = 6.3 Hz), 1.91 (t, 2H, JHH = 8.0 Hz),
1.52 (d, 6H, JHH = 6.9 Hz), 1.07 (d, 6H, JHH = 6.9 Hz), ꢀ0.74 (s, 3H).
13C NMR (300 MHz, C6D6): d 166.4, 165.3, 164.5, 150.2, 141.1,
141.0, 135.8, 134.5, 133.9, 133.5, 131.7, 129.9, 128.2, 127.9,
127.5, 127.2, 126.9, 126.5, 125.8, 123.6, 120.8, 113.9, 49.8, 28.5,
25.3, 24.9, 23.2, ꢀ9.8.
1H NMR (400 MHz, C6D6): d 8.35 (s, 1H), 7.67–7.59 (m, 5H), 7.42
(d, 2H, JHH = 4.9 Hz), 6.93–6.39 (m, 13H), 4.13 (sept., 2H,
JHH = 6.9 Hz), 3.42 (t, 2H, JHH = 6.3 Hz), 1.81 (t, 2H, JHH = 6.6 Hz),
1.39 (d, 6H, JHH = 6.9 Hz), 1.01 (d, 6H, JHH = 6.9 Hz).
ESI-HRMS: calculated for C35H38N2ONi+ (M+) 560.23376; found
560.23391.
13C NMR (300 MHz, C6D6): d 167.5, 165.1, 164.8, 150.9, 150.8,
140.7, 140.6, 136.7, 135.8, 134.8, 134.7, 134.5, 134.1, 133.8,
133.7, 133.5, 131.9, 129.9, 129.7, 128.8, 128.7, 128.2, 127.5,
127.1, 126.8, 126.4, 125.0, 124.9, 123.0, 122.2, 120.7, 114.4, 49.8,
28.8, 25.6, 25.2, 22.8.
4.1.11. (2-((2,6-Diisopropylphenyl)iminomethyl)phenoxide)-
Ni(CH3)(3,4-dihydroisoquinoline) (8j)
ESI-HRMS: calculated for C40H40N2NiO+ (M+) 622.24941; found
622.24933.
Yield: 81%. 1H NMR (300 MHz, C6D6): d 8.43 (s, 1H), 7.53 (s, 1H),
7.18 (dt, 1H, 1JHH = 5.2 Hz, 2JHH = 1.6 Hz), 7.09–7.06 (m, 3H), 7.00 (d,
1
2
1H, JHH = 8.5 Hz), 6.91 (dd, 1H, JHH = 7.3 Hz, JHH = 1.6 Hz), 6.84 (t,
1H, JHH = 7.1 Hz), 6.72 (t, 1H, JHH = 7.1 Hz), 6.53–6.42 (m, 3H), 4.16
(sept., 2H, JHH = 6.9 Hz), 3.78 (t, 2H, JHH = 7.4 Hz), 2.10 (t, 2H,
JHH = 7.7 Hz), 1.51 (d, 6H, JHH = 6.9 Hz), 1.04 (d, 6H, JHH = 6.9 Hz),
ꢀ0.73 (s, 3H).
4.3. Stability of complexes 8e–h in benzene
A typical experiment is as follows. A.J. Young tube was charged
with a 0.02 M solution of nickel complex 8e (6.4 mg, 0.010 mmol)
in C6D6 (0.50 mL). Benzyl benzoate was added as the internal stan-
dard. The formation of bis-salicylaldiminatonickel(II) complexes
10a was monitored by 1H NMR spectroscopy at 25 °C. The decom-
position time was determined by measuring both the disappear-
ance of 8e and the appearance of uncoordinated imine.
13C NMR (300 MHz, C6D6): d 168.1, 166.1, 164.3, 150.3, 141.2,
135.7, 134.3, 134.1, 131.8, 127.3, 127.1, 126.4, 123.6, 122.9,
120.1, 113.7, 49.8, 28.5, 25.7, 24.9, 23.2, ꢀ9.1.
ESI-HRMS: calculated for C29H34N2ONi+ (M+) 484.20246; found
484.20286.

238
C. Stafford, B.A. Arndtsen / Inorganica Chimica Acta 369 (2011) 231–239
4.3.1. Bis(6-phenyl-2-((2,6-diisopropylphenyl)iminomethyl)-
phenoxide)nickel (10a) [16]
13C NMR (300 MHz, CDCl3): d 169.0, 157.5, 149.3, 148.0, 137.6,
137.1, 136.2, 133.7, 128.9, 128.4, 127.9, 127.8, 126.7, 124.3,
123.1, 27.9, 23.5, 20.5.
Due to the paramagnetic nature of this complex, NMR charac-
terization could not be achieved.
ESI-HRMS: calculated for C27H30NO2+ (M+H+) 400.22686; found
400.22711
ESI-HRMS: calculated for C50H53N2O2Ni+ (M+H+) 771.34593;
found 771.34550.
4.4.2. Acetic acid 2-((2,6-diisopropylphenyl)iminomethyl)-phenyl
4.3.2. Bis(2-((2,6-diisopropylphenyl)iminomethyl)phenoxide)nickel
(10b)
ester (13b)
1
1H NMR (300 MHz, CDCl3): d 8.29 (s, 1H), 8.17 (dd, 1H, JHH
=
1H NMR (300 MHz, C6D6): d 7.19 (t, 2H, JHH = 2.1 Hz), 7.06 (m,
6H), 6.75 (t, 2H, JHH = 4.9 Hz), 6.65 (d, 2H, JHH = 6.4 Hz), 6.22 (t,
2H, JHH = 6.7 Hz), 5.92 (d, 2H, JHH = 8.5 Hz), 4.38 (sept., 4H,
JHH = 6.7 Hz), 1.46 (d, 12H, JHH = 7.0 Hz), 1.11 (d, 12H, JHH = 7.0 Hz).
13C NMR (300 MHz, C6D6): d 164.6, 164.2, 146.4, 142.3, 134.4,
132.8, 126.3, 123.1, 121.5, 119.7, 115.2, 29.3, 24.4, 23.7.
ESI-HRMS: calculated for C38H45N2O2Ni+ (M+H+) 619.28288;
found 619.28290.
7.9 Hz, JHH = 1.5 Hz), 7.53 (dt, 1H, JHH = 7.3 Hz, JHH = 1.8 Hz),
7.39 (t, 1H, JHH = 6.2 Hz), 7.19–7.12 (m, 4H), 2.95 (sept., 2H,
JHH = 7.0 Hz), 2.27 (s, 3H), 1.16 (d, 12H, JHH = 7.0 Hz).
13C NMR (300 MHz, CDCl3): d 169.0, 157.2, 150.6, 149.3, 137.6,
132.1, 128.7, 128.0, 126.4, 124.3, 123.1, 123.0, 27.8, 23.4, 20.7.
ESI-HRMS: calculated for C21H26NO2+ (M+H+) 324.19577; found
324.19581.
2
1
2
4.4.3. Acetic acid 2-((2,6-diisopropylphenyl)iminomethyl)-4-fluoro-
phenyl ester (13c)
4.3.3. Bis(4-fluoro-2-((2,6-diisopropylphenyl)iminomethyl)-
phenoxide)nickel (10c)
1H NMR (300 MHz, CDCl3): d 8.24 (d, 1H, JHF = 2.2 Hz), 7.90 (dd,
1
2
1H NMR (300 MHz, C6D6): d 7.16 (t, 2H, JHH = 7.7 Hz), 7.00 (d,
4H, JHH = 7.7 Hz), 6.82 (s, 2H), 6.47 (dt, 2H, JHH = 8.7 Hz,
JHF = 3.0 Hz), 6.28 (dd, 2H, JHH = 8.7 Hz, JHF = 3.0 Hz), 5.69 (dd, 2H,
JHH = 9.2 Hz, JHF = 4.4 Hz), 4.28 (sept., 4H, JHH = 6.7 Hz), 1.43 (d,
12H, JHH = 6.9 Hz), 1.09 (d, 12H, JHH = 6.9 Hz).
1H, JHH = 8.9 Hz, JHH = 3.0 Hz), 7.26–7.13 (m, 5H), 2.92 (sept., 2H,
JHH = 6.9 Hz), 2.28 (s, 3H), 1.17 (d, 12H, JHH = 6.9 Hz).
13C NMR (300 MHz, CDCl3): d 169.2, 162.1, 158.9, 156.1, 148.9,
146.5, 137.5, 129.6 (d, JCF = 7.8 Hz), 124.6 (d, JCF = 5.1 Hz), 124.5,
123.1, 119.0 (d, JCF = 23.5 Hz), 114.4 (d, JCF = 24.4 Hz), 27.9, 23.5,
20.7.
13C NMR (300 MHz, C6D6): d 163.9, 160.6, 155.0, 151.9, 146.0,
142.0, 126.5, 123.2, 123.1, 122.9, 122.3 (d, JCF = 7.4 Hz), 118.1 (d,
JCF = 8.3 Hz), 115.5 (d, JCF = 22.1 Hz), 29.3, 24.3, 23.7.
19F NMR (400 MHz, C6D6): d ꢀ130.4.
19F NMR (400 MHz, CDCl3): d ꢀ115.3 (s).
ESI-HRMS: calculated for
found 342.18638.
C
21H25NO2F+ (M+H+) 342.18631;
ESI-HRMS: calculated for C38H43N2O2NiF2 (M+H+) 655.26400;
+
found 655.26406.
4.4.4. Acetic acid 2-((2,6-diisopropylphenyl)iminomethyl)-4-nitro-
phenyl ester (13d)
4.3.4. Bis(4-nitro-2-((2,6-diisopropylphenyl)iminomethyl)phenoxide)-
nickel (10d)
1H NMR (300 MHz, CDCl3): d 9.05 (d, 1H, JHH = 2.9 Hz), 8.37 (dd,
1
2
1H, JHH = 9.0 Hz, JHH = 2.9 Hz), 8.32 (s, 1H), 7.40 (d, 1H,
JHH = 8.8 Hz), 7.17 (s, 3H), 2.90 (sept., 2H, JHH = 7.0 Hz), 2.32 (s,
3H), 1.17 (d, 12H, JHH = 7.0 Hz).
1H NMR (300 MHz, C6D6): d 7.57 (d, 2H, JHH = 2.7 Hz), 7.45 (dd,
2H, JHH1 = 9.2 Hz, JHH2 = 2.7 Hz), 7.14 (m, 4H), 6.95 (m, 4H), 6.56 (s,
2H), 4.00 (sept., 4H, JHH = 7.0 Hz), 1.35 (d, 12H, JHH = 7.0 Hz), 1.06
(d, 12H, JHH = 7.0 Hz).
13C NMR (300 MHz, CDCl3): d 168.2, 155.2, 154.6, 148.6, 146.1,
137.5, 129.2, 126.7, 124.9, 124.3, 124.2, 123.2, 28.0, 23.5, 20.8.
13C NMR (300 MHz, C6D6): d 167.4, 165.0, 144.7, 141.6, 137.8,
130.5, 129.0, 127.1, 118.0, 29.3, 24.1, 23.5.
ESI-HRMS: calculated for
found 369.18088.
C
21H25N2O4 (M+H+) 369.18077;
+
ESI-HRMS: calculated for
23506; found 731.23501.
C
38H42N4O6NiNa+ (M+Na+) 731.
4.4.5. Benzoic acid 3-((2,6-diisopropylphenyl)iminomethyl)-biphenyl-
2-yl ester (13e)
4.4. Reactions of 8 with carbon monoxide
1H NMR (400 MHz, C6D6):
d 8.58 (s, 1H), 8.40 (d, 1H,
JHH = 8.1 Hz), 7.89 (d, 2H, JHH = 7.0 Hz), 7.39 (d, 2H, JHH = 7.0 Hz),
7.26 (d, 1H, JHH = 7.7 Hz), 7.09–6.89 (m, 8H), 6.83 (t, 2H,
JHH = 7.7 Hz), 3.23 (sept., 2H, JHH = 7.0 Hz), 1.13 (d, 12H,
JHH = 7.0 Hz).
A 25 mL reaction bomb was charged with the appropriate
amount of complex 8 (0.0618 mmol) and imine (0.185 mmol) dis-
solved in benzene (10 mL). The solution was placed under 1 atm of
carbon monoxide and stirred at ambient temperature for 5 h. The
carbon monoxide atmosphere was removed by a freeze–pump–
thaw process. The resulting solution was concentrated in vacuo
and then stirred in acetonitrile, causing the bis-salicylaldiminato-
nickel complex 10 to precipitate. The solids were removed by fil-
tration and the filtrate was concentrated in vacuo. Purification of
the organic products was achieved via silica gel chromatography
using a 60:40 hexanes/dichloromethane mixture as the eluent.
When 3,4-dihydroisoquinoline is the reaction substrate, a mixture
of 60:40 hexanes/dichloromethane incorporating 3% triethylamine
and 3% methanol was used as the eluent.
13C NMR (300 MHz, CDCl3): d 164.8, 157.2, 149.2, 137.6, 136.9,
136.3, 133.8, 133.6, 130.0, 129.2, 128.9, 128.5, 128.4, 128.3, 127.7,
127.6, 124.2, 123.0, 27.8, 23.5.
ESI-HRMS: calculated for C32H32NO2+ (M+H+) 462.24245; found
462.24276.
4.4.6. Meso-N,N0-diacyl-1,10,2,20,3,30,4,40-octahydro-1,
10-biisoquinoline (14a) [27]
1H NMR (300 MHz, 25 °C, CDCl3): (two conformers: A ca. 67%,
and B ca. 33%) d 7.56 (d, 2H, JHH = 7.1 Hz, A), 7.30–7.07 (m, 10H),
7.01–6.94 (m, 2H), 6.47 (d, 2H, JHH = 7.7 Hz, A), 6.03 (s, 2H, B),
5.86 (d, 2H, JHH = 5.2 Hz, A), 5.36 (d, 2H, JHH = 5.0 Hz, B), 4.89 (s,
1
2
4.4.1. Acetic acid 3-((2,6-diisopropylphenyl)iminomethyl)-biphenyl-2-
yl ester (13a)
2H, B), 4.62–4.53 (dt, JHH = 11.8 Hz, JHH = 5.2 Hz, B), 4.41–4.36
(m, 2H, A), 3.94–3.87 (m, 2H), 3.66–3.51 (m, 4H), 3.36–3.28 (m,
2H), 3.12–2.95 (m, 4H), 2.94–2.68 (m, 8H), 2.58–2.52 (m, 2H),
2.39–2.25 (m, 2H), 2.10 (d, 6H, JHH = 11.5 Hz, A), 1.81 (s, 3H, B).
13C NMR (300 MHz, C6D6): d 171.2, 170.6, 170.5, 170.4, 135.6,
135.0, 134.9, 134.7, 134.5, 133.7, 133.5, 133.1, 129.2, 128.7,
1H NMR (300 MHz, CDCl3): d 8.28 (s, 1H), 8.18 (dd, 1H,
2
1JHH = 8.2 Hz, JHH = 1.6 Hz), 7.55–7.36 (m, 6H), 7.18–7.10 (m, 4H),
2.96 (sept., 2H, JHH = 6.9 Hz), 1.98 (s, 3H), 1.16 (d, 12H,
JHH = 6.9 Hz).

C. Stafford, B.A. Arndtsen / Inorganica Chimica Acta 369 (2011) 231–239
239
128.4, 128.2, 127.7, 127.5, 127.4, 126.9, 126.8, 126.5, 126.1, 60.7,
60.1, 59.4, 57.2, 44.0, 42.4, 38.0, 36.6, 28.9, 28.8, 28.0, 27.9, 22.6,
22.4, 21.1, 21.0.
[6] For examples of direct observation of imine insertion: (a) F. Muller, G. van
Koten, K. Vrieze, D. Heijdenrijk, Organometallics 8 (1989) 33;
(b) M.D. Fryzuk, W.E. Piers, Organometallics 9 (1990) 986;
(c) A.C. Reduto, L.S. Hegedus, Organometallics 14 (1995) 1586;
(d) J.D. Debad, P. Legzdins, S.A. Lumb, R.J. Batchelor, F.W.B. Einstein,
Organometallics 14 (1995) 2543;
ESI-HRMS: calculated for C22H24N2O2Na+ (M+Na+) 371.17354;
found 371.17268.
(e) Y. Obora, T. Ohta, C.L. Stern, T.J. Marks, J. Am. Chem. Soc. 119 (1997) 3745;
(f) C. Krug, J.F. Hartwig, J. Am. Chem. Soc. 126 (2004) 2694;
(g) C. Krug, J.F. Hartwig, Organometallics 23 (2004) 4594.
[7] For examples: palladium catalyzed: (a) H. Nakamura, H. Iwama, Y. Yamamoto,
J. Am. Chem. Soc. 118 (1996) 6641;
4.4.7. Dl-N,N0-diacyl-1,10,2,20,3,30,4,40-octahydro-1,10-biisoquinoline
(14b) [27]
1H NMR (400 MHz, C6D6): d 6.96 (t, 2H, JHH = 7.3 Hz), 6.90 (d,
2H, JHH = 7.3 Hz), 6.65 (t, 2H, JHH = 7.3 Hz), 5.99 (d, 2H, JHH = 7.3 Hz),
5.69 (s, 2H), 3.84–3.79 (m, 2H), 3.67–3.59 (m, 2H), 2.81 (dt, 2H,
1JHH = 10.6 Hz, 2JHH = 5.9 Hz), 2.40 (dt, 2H, 1JHH = 15.7 Hz,
2JHH = 5.5 Hz), 1.79 (s, 6H).
(b) H. Nakamura, K. Aoyagi, J.G. Shim, Y. Yamamoto, J. Am. Chem. Soc. 123
(2001) 372;
. Rhodium catalyzed:(c) S. Oi, M. Moro, H. Fukuhara, T. Kawanishi, Y. Inoue,
Tetrahedron Lett. 40 (1999) 9259;
(d) M. Ueda, N. Miyaura, J. Organomet. Chem. 595 (2000) 31;
(e) T. Hayashi, M. Ishigedani, J. Am. Chem. Soc. 122 (2000) 976;
(f) K. Ueura, S. Miyamura, T. Satoh, M. Miura, J. Organomet. Chem. 691 (2006)
2821;
(g) M. Ueda, A. Saito, N. Miyaura, Synlett (2000) 1637;
(h) T. Ishiyama, J.F. Hartwig, J. Am. Chem. Soc. 122 (2000) 12043;
(i) M.A. Beenen, D.J. Weix, J.A. Ellman, J. Am. Chem. Soc. 128 (2006) 6304;
. Stoichiometric in rhodium:(j) C. Krug, J.F. Hartwig, J. Am. Chem. Soc. 126
(2004) 2694.
13C NMR (300 MHz, C6D6): d 170.8, 135.4, 134.3, 129.7, 127.6,
127.5, 127.4, 125.3, 57.0, 44.2, 28.0, 22.3.
ESI-HRMS: calculated for C22H24N2O2Na+ (M+Na+) 371.17354;
found 371.17273.meso, dl-N,N0-dibenzoyl-1,10,2,20,3,30,4,40-octahy-
dro-1,10-biisoquinoline (15) [27a].
1H NMR (500 MHz, CDCl3): d 7.47–7.07 (m, 22H, meso & dl), 7.00
(d, 2H, JHH = 6.9 Hz, meso), 6.93 (d, JHH = 6.9 Hz, meso), 6.75 (d, 2H,
JHH = 6.9 Hz, dl), 6.69 (d, 2H, JHH = 6.4 Hz, dl), 6.48 (s, 2H, dl), 6.41 (d,
2H, JHH = 6.0 Hz, dl), 6.08 (d, 2H, JHH = 7.8 Hz, meso), 5.25 (d, 2H,
JHH = 7.3 Hz, meso), 5.07 (s, 2H, meso), 4.54–4.37 (m, 2H, dl),
3.64–3.55 (m, 4H, meso & dl), 3.34–3.15 (m, 5H, meso & dl), 2.93–
2.75 (m, 5H, meso & dl), 2.53–2.35 (m, 2H, dl).
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13C NMR (500 MHz, CDCl3): d 171.6, 171.3, 170.7, 137.1, 136.3,
135.9, 135.4, 134.4, 134.1, 133.6, 133.3, 129.6, 129.5, 129.4,
129.3, 129.0, 128.8, 128.6, 128.5, 128.4, 128.1, 127.9, 127.5,
127.0, 126.9, 126.8, 126.7, 126.5, 126.5, 126.2, 126.0, 61.3, 60.1,
57.5, 55.1, 43.0, 38.5, 38.1, 29.2, 28.7, 27.6, 27.1.
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(b) R. Dhawan, R.D. Dghaym, B.A. Arndtsen, J. Am. Chem. Soc. 125 (2003) 1474;
(c) Y. Lu, B.A. Arndtsen, Angew. Chem., Int. Ed. 47 (2008) 5430;
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ESI-HRMS: calculated for C32H28N2O2Na+ (M+Na+) 495.20430;
found 495.20489.
Acknowledgments
We thank NSERC Discovery and Accelerator Programs, DuPont,
and CFI for funding of this project.
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[19] Liberation of ethane is observed. 1H NMR (400 MHz, C6D6): d 0.77 ppm (6H,
s). Reference: M. Hesse, H. Meier, B. Zeeh, Spectroscopic Methods in Organic
Chemistry, G. Thieme, Stuttgart, 1997.
Appendix A. Supplementary material
1H and 13C NMR spectra of isolated products are available. These
data can be obtained free of charge from The Cambridge Crystallo-
graphic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.ica.2010.12.024
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room temperature. Examples with Ni–CH3: (a) C.S. Shultz, J.M. DeSimone, M.
Brookhart, J. Am. Chem. Soc. 123 (2001) 9172;
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