Formation of the paramagletic Ni(I) π-allyl complex in the Ni(allyl)2 - (2,6-diisopropylphenyl)diazabutadiene system

Article abstract of DOI:10.1016/j.jorganchem.2011.07.023

It has been shown that the reaction of Ni(allyl)₂ with (2,6-diisopropylphenyl)diazabutadiene gives the imino-amide Ni complex (1). The imino-amide moiety of this complex undergoes some complicated rearrangements resulting in spontaneous formati

Full text of DOI:10.1016/j.jorganchem.2011.07.023

Journal of Organometallic Chemistry 696 (2011) 3483e3490
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Formation of the paramagletic Ni(I)
p-allyl complex in the
Ni(allyl)2 e (2,6-diisopropylphenyl)diazabutadiene system
,
a
a
b
Peter B. Kraikivskii a , Vitaly V. Saraev , Victoria V. Bocharova , Galina V. Romanenko ,
*
Stanislav K. Petrovskii a, Dmitrii A. Matveev a
a Irkutsk State University, 664003, Irkutsk, K. Marx str. 1, Russia
b The Institute International Tomography Center of the Siberian Branch of the Russian Academy of Sciences, 630090, Novosibirsk, Institutskaya str., 3A, Russia
a r t i c l e i n f o
a b s t r a c t
Article history:
It has been shown that the reaction of Ni(allyl)2 with (2,6-diisopropylphenyl)diazabutadiene gives the
Received 24 April 2011
Received in revised form
5 July 2011
imino-amide Ni complex (1). The imino-amide moiety of this complex undergoes some complicated
rearrangements resulting in spontaneous formation of a paramagnetic
p-allyl Ni(I) complex. Nickel
complexes formed in the system have been studied with ESR, FTIR, 2D NMR, and mass spectrometry. The
structure of complex 1 was studied with X-ray diffraction.
Accepted 18 July 2011
Ó 2011 Elsevier B.V. All rights reserved.
Keywords:
Monovalent nickel
Diimine ligands
Chelates
Structure elucidation
1. Introduction
the catalytic cycle, that is, it can coordinate to the metal center or
leave its coordination sphere in the unchanged form. Thus, the
The analysis of the literature on transition metal allyl complexes,
from the first obtained compounds [1,2] to the present day [3e6],
possibility of any metamorphosis of the ligand is usually not
considered. In addition, most of works grounds mechanisms of the
catalytic cycle on nickel(0) and nickel(II) complexes, with the Niþ2
form regarded as more stable one, second only to the stability of
colloidal nickel [9,12e14]. Nevertheless, certain papers do state that
Ni(I) species are formed both in the systems based on Ni(II) allyl
complexes [6] and in the systems with diimine ligands [10].
To the above we can add that there are very few papers on nickel
allyl systems in spite of the intensive studies of transition metal
allyl complexes by and large. Most researchers deal with allyl
complexes of palladium [15]. This obviously results from the low
stability of nickel allyl complexes as well as the inefficiency of the
wide used NMR specroscopy for their study [16].
demonstrates that
considerable role in catalytic reactions. A
p
-allyl structures of transition metals play
-allyl fragment can be
p
a part of the starting transition metal complex or formed straightly
in the coordination sphere of a transition metal when complexes
treated with olefins in the course of the catalysis. As a rule, in cata-
lytic systems
p-allyl complex is stabilized by different organo-
elemental ligands. In 1995 Brookhart with coworkers proposed
a catalytic system based on nickel and palladium diimine complexes.
[7] This system had a definite advantage of converting lower olefins
into linear polymers enriched with a-isomers. One of the perspec-
tive ways for the evolution of this type of catalytic systems is the
incorporation of diazabutadiene diimine ligands in starting cationic
or neutral allyl complexes of nickel and palladium [8]. Despite the
intensive investigation of these catalytic systems, the question if N-
bearing ligands can undergo conversions within organometallic
complexes remains open. In the literature almost all proposed
mechanisms for the catalytic cycle do not consider the possibility of
changing the nature of the metaleligand bond as well as the struc-
ture of the diimine ligand itself [9e14]. Up to this moment the ligand
is commonly considered as an inalterable unit acting as a “guest” in
This work reports a detailed spectroscopic (NMR, ESR and IR)
examination of the complexation between Ni(allyl)2 and bis(2,6-
diisopropylphenyl)diazabutadiene, one of the most effective,
widespread and synthetically available ligands.
2. Results and discussion
When a yellowsolution of Ni(allyl)2 in diethyl ether was mixed with
the equimolar amount bis(2,6-diisopropylphenyl)diazabutadiene
(DAB) at ꢀ5 ꢁC, the solution color turned bright red. Addition of some
pentane to the reaction mixture and subsequent cooling to ꢀ30 ꢁC
* Corresponding author. Tel.: þ7 3952 425935.
E-mail address: peter10@list.ru (P.B. Kraikivskii).
0022-328X/$ e see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2011.07.023

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P.B. Kraikivskii et al. / Journal of Organometallic Chemistry 696 (2011) 3483e3490
1.61 and 1.67 ppm correlatewith thatat53.61 ppm. In DEPT-135 these
signals are uniquely identified as belonging to 13C nuclei of CH2
groups. The analysis of the degree of shielding and coupling constants
enables one to identify signals from the syn- and anti-protons of
allyl group at the metal atom and the carbon atoms bound to them
(Table 1). The signals from the terminal protons of the -allyl group of
p-
p
complex 1 are considerably shifted to a weak field in comparisonwith
those for Ni(allyl)2 (Table 1). All the hydrogen and carbon atoms of the
p
-allyl group of complex 1 are not equal in contrast to those for
Ni(allyl)2 [2,17]. The significant nonequivalence of the 13C and 1H
nuclei in CH2 fragments of the -allyl group of complex 1 can be
p
associated with thatthe imineand amidefragments of theligandhave
significantly different shielding effects. It is rather difficult to locate
unambiguously the positions of atoms in the
the ligand. This flows from the absence of selective cross-peaks
between the protons of the -allyl group and those of the iminee
p-allyl group relative to
p
amide ligand in TOCSY and NOESY spectra.
In the 13C DEPT-135 NMR spectrum of complex 1 the only
resonance from CH2 group of sp2 carbon atom is registered at
119.48 ppm. It correlates with a resonance at 5.01 ppm in HSQC.
The mentioned signals are attributable to the terminal CH2 group at
the double bond of a 1-propenyl substituent. Analyzing the array of
the HSQC, HMBC, COSY, NOESY and DEPT-135 data, we assigned the
rest signals from other nuclei of the propenyl fragment (Table 1).
The CH2 group at the nitrogen, which has a valent bond with
nickel, is definitely identified by the presence of doublets at 4.56
and 4.38 ppm from two unequivalent protons in the 1H spectrum.
The doublet at 4.56 ppm gives NOESY cross-peak with a signal at
Fig. 1. Molecular structure of the complex 1 according to the data of X-ray structure
analysis. Lenghts [Å] and angles [ꢁ] of several bonds: NieN1 1.845(3), NieN2 1.922(3),
NieC15 1.955(4), NieC16 1.955(9), NieC17 1.947(13), C25eC26 1.138(2), C24eC25
1.320(4), C8eC24 1.557(3), N1eC7 1.437(9), N2eC8 1.287(9), C7eC8 1.478(2);
N1eNieN2 84.93(12), N2eNieC17 102.76 (16), N1eNieC15 104.01(3), C17eNieC15
68.30(6), NieN1eC7 113.92(3), NieN2eC8 114.92(4), C17eC16eC15 121.16(2).
caused precipitation of bright red lamellar crystals. The obtained
crystals are air-sensitive and if finely powdered can auto ignite.
According to the X-ray structural data (Fig. 1), the obtained
product is an imineeamide
p-allyl complex of nickel (II) 1, its
formation is depicted on the following scheme:
i-Pr
i-Pr
i-Pr
i-Pr
i-Pr
i-Pr
i-Pr
+
N
N
Ni
N
N
Ni
i-Pr
1
Equation 1.
As it is shown on the scheme, the interaction between Ni(allyl)2
and DAB is not a simple ligand exchange, it proceeds through
a complicated imineeamide rearrangement in the diazabutadiene
moiety of the ligand.
According to the X-ray structural data, the planes of phenyl rings
in the diisopropylphenyl ligands are almost perpendicular to the
helate cycle plane. The angles between their planes are 88.1 and
82.4ꢁ. The distances NieN (1.846(3) and 1.921(3) Å) are essentially
different; it is significantly longer for the N atom involved in C]N
bonding. The allyl ligand is disordered in two positions.
3.86 ppm from the proton at the tertiary carbon of the isopropyl
substituent in a phenyl ring of the ligand. We used this signal to
define the mutual location of the phenyl rings and other fragments
of complex 1 (details in experimental section). In HMBC signals at
4.56 and 4.38 ppm correlate with a resonance at 191.36 ppm from
the carbon atom at the nitrogen coordinatively bound to the nickel.
According to the DEPT-135 data, this carbon atom is quaternary.
In the IR spectrum of complex 1 an imine band n(C]N) is
observed at 1602 cmꢀ1. It is shifted by 24 cmꢀ1 to lower frequencies
in comparison with the case of the free ligand. It is quite consistent
with the literature data [18] on shifting the frequency when dii-
mine ligands give nitrogen-metal coordination bond. Bands at
To obtain more information about the structure of the product of
so unusual reaction complex 1 was thoroughly studied with homo-
and heteronuclear two-dimensional NMR spectroscopy.
1105 cmꢀ1
(
nsCCC,s) and 532 cmꢀ1
(dCCC,s) correspond to the
The NMR 1H spectrum of complex 1 contains a resolved multiplet
resonancefrom one protonat5.35 ppmwhich istypicalfor thecentral
proton of the allyl groupboundtoa nickelatom [2]. Thissignalhasone
HSQC cross-peak with a resonance from 13C nucleus at 196.39 ppm.
According to the DEPT-135 data, this carbon atom isbound only to one
proton. The COSY spectrum has cross-peaks 5.35e1.40, 5.35e1.48,
5.35e1.61, 5.35e1.67 ppm. In the HSQC spectrum signals at 1.40 and
1.48 ppm correlate with a resonance at 50.62 ppm, whereas signals at
vibrations of carbon skeleton of the
p-allyl group [19].
The mass spectrum of complex 1 contains a pronounced
molecular ion peak (m/z ¼ 516) with intensity of 70% of the
maximum. In paper [20] comparable conditions were used for
recording mass spectra of nickel ethyl complexes, though the
intensities of the molecular ion signals were less 5%. The compar-
ative analysis of
p-allyl group in 1 and that of other organometallic
nickel complexes allows us to say that the former has stronger

P.B. Kraikivskii et al. / Journal of Organometallic Chemistry 696 (2011) 3483e3490
3485
Table 1
NMR chemical shifts
d
(ppm) of nickel allyl complexes.a
Complex
dH15anti
dH17anti
dH16
dH15syn
dH17syn
dC15
dC16
dC17
dC26
dC25
dC24
dC8
dC7
1 (THF-D8)
1.41
1.43
5.34
1.59
1.62
53.6
106.39
50.6
119.48
132.44
37.65
191.36
72.82
69.4
J ¼ 13.0
J ¼ 12.0
J ¼ 6.0
J ¼ 6.8
2 (C6D6)
1.83
1.79
5.46
1.62
2.0
53.75
53.97
106.43
106.7
50.75
50.71
18.47
19.26
139.49
140.88
123.46
124.18
183.13
184.13
J ¼ 13.0
1.61
1.67
J ¼ 13.0
1.43
J ¼ 6.0
1.41
3.76
J ¼ 4.3
1.59
2 (THF-D8)
Ni(allyl)2 [2,18]
5.35
4.9
69.56
J ¼ 14.3
J ¼ 7.6
a
Atom numbering.
26
25
24
8
7
(i-Pr)2Ph
N
N
Ph(i-Pr)2
Ni
16
15
17
bonding with the metal and it is less susceptible to dissociation by
impact ionization.
Thus X-ray structural data are absolutely consistent with the 2D
NMR, vibrational spectroscopy and MS data.
106.43 ppm in the HSQC spectrum which, according to the DEPT-
135 data, belongs to a carbon atom bonded with only one proton.
In the HMBC spectrum resonance at 5.46 ppm correlates with
signals at 50.75 ppm and 53.75 ppm from the terminal carbon
Complex 1 is stable in a crystalline form at least 90 days. Bright-
red THF or benzene solutions of complex 1 sealed in evacuated
ampoules become reddish-brown at 20e25 ꢁC during 3e4 h. The
process is accompanied by significant changes in NMR spectra
which are indicative of a position isomerization of the double bond.
In this regard the NMR 13C DEPT-135 spectra (Fig. 2) are most
revealing. They clearly display the replacement of signals at
119.48 ppm (H2C]), 132.44 ppm (HC])and 37.65 ppm (CH2) of the
CH2-terminated propenyl fragment of complex 1 with signals at
19.26 ppm. (terminal CH3), 140.88 ppm (HC]), 124.16 ppm (HC])
of the CH3-terminated propenyl fragment of new complex 2 (Fig. 2).
On the basis of the NMR data one can contend that in solution
complex 1 transforms spontaneously into complex 2:
atoms of p-allyl group, each of them, according the DEPT-135 data,
is bonded with two protons. The HSQC spectrum contains cross-
peaks at 53.75e1.83, 53.75e1.62 and 50.75e1.79, 50.75e2.0.
Thereby, in the 1H spectrum signals at 1.83, 1.62, 1.79, and 2.0 ppm
can be definitely ascribed to the terminal protons of the allyl group
(Fig. 3).
At the same time according to the HSQC and HMBC data, the
protons with signals at 1.83 and 1.62 ppm are bonded with the
carbon atom having resonance at 53.75 ppm, whereas the protons
with signals at 1.79 and 2.0 are bonded with the carbon having
resonance at 50.75 ppm. All the four signals from the terminal
protons are split into doublets. In COSY the doublets at 1.62 ppm
(13 Hz.) and at 1.79 ppm (13 Hz.) have an intensive cross peak at
i-Pr
i-Pr
i-Pr
i-Pr
i-Pr
i-Pr
i-Pr
i-Pr
N
N
N
N
Ni
Ni
2
1
Equation 2.
All attempts to obtain crystalline complex 2 have failed.
Conventional and zonal crystallization from different solvents gave
only amorphous reddish-brown powders extremely unsteady in
air. In this connection our view about the structure of complex 2 is
essentially based upon correlation NMR spectroscopy data.
5.46 ppm that in combination with the values of the coupling
constants allows definite assignment of these doublets to the anti-
protons of allyl group (Fig. 4).
Accordingly, the doublets at 1.83 ppm (6 Hz.) and 2.0 ppm
(4.3 Hz.) are attributed to the syn-protons. The spin-spin interac-
tion of these protons with each other and the central proton of the
The multiplet of the central proton of
p-allyl group in complex 2
is registered at 5.46 ppm, and it correlates with signal at
p-allyl is registered in COSY. The intensities of the cross-peaks are

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P.B. Kraikivskii et al. / Journal of Organometallic Chemistry 696 (2011) 3483e3490
Fig. 2. DEPT-135 NMR 13C spectra: (a) complex 1 immediately after dissolving; (b) in 4 hours after signal a registration. THF-D8 as a solvent, NMR ampoule is sealed under vacuum.
Fig. 3. NMR HSQC and HMBC correlation spectra of the complex 2 (C6D6). Insertions into the base spectrum are made in a field without cross-peaks.

P.B. Kraikivskii et al. / Journal of Organometallic Chemistry 696 (2011) 3483e3490
3487
Fig. 4. Spectra of exchange 2D NOESY spectroscopy and heteronucleous COSY correlation of complex 2 (C6D6). Insertions into the base spectrum are made in a field without cross-
peaks.
significantly lower, than those for COSY cross-peaks between the
central and anti-protons.
data are in good agreement with our data. Thereby we can say that
complex 2 exists in solution both in the h3
-p
-allyl and h1
-
s-allyl
Analyzing the NMR data for the
unusual inversion of the chemical shifts for the syn- and anti-
p
-allyl group of complex 2, an
-allyl
forms.
p
The IR spectrum of complex 2 contains the imine band n
(C]N)
protons should be noted. As a rule, anti-protons are more shielded
in allyl complexes of transition metals than syn-protons [1,17]. For
the protons at C15 carbon atom (Table 1) in complex 2 the reverse
was observed due to the fact that the signal of the syn-proton is
located in a stronger field than that of the anti-proton. The NOESY
spectrum demonstrates the distinct combined cross-peaks for all
at 1641 cmꢀ1 which is shifted to higher frequencies by 39 cmꢀ1
relative to the corresponding bond of complex 1. This situation is
quite consistent with the formation of conjugated double bond
system during isomerization of the propenyl substituent. The band
at 1076 cmꢀ1
(nsCCC,s), corresponding to the vibrations of p-allyl
carbon backbone, is broadened and shifted to lower frequencies by
four terminal protons of the
p-allyl group (Fig. 4) that indicates the
29 cmꢀ1 as compared with that for complex 1; the band
dCCC,s has
presence of chemical exchange processes between the syn- and
anti-protons [21]. The chemical exchange can be realized only
through rotation of the terminal CH2 groups that is possible if there
almost the same location (532 cmꢀ1).
The mass spectrum of complex 2 has the quite intensive (65% of
the maximum) molecular ion peak with m/z ¼ 516 that is also
is a dynamic equilibrium between the h3
group in complex 2:
-
p
- and h1
-s
-forms of allyl
indicative of insignificant dissociation of the p-allyl moiety by
impact ionization.
N
N
N
N
N
N
Ni
Ni
16
Ni
16
15
17
17
15
17
15
16
Equation 3.
A similar exchange in allyl complexes of palladium was thor-
oughly studied by NOESY NMR spectroscopy [4,5], and the reported
A solution of complex 2 sealed in an evacuated NMR ampoule is
stable during several hours according to NMR data. Then the

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P.B. Kraikivskii et al. / Journal of Organometallic Chemistry 696 (2011) 3483e3490
registered 1H and 13C NMR signals became broader and finally
disappear leaving only signals of the solvent on the second day.
During this the solution color changes from reddish-brown to dark-
brown. The ESR spectrum of the resulted dark-brown solution has
an intensive signal (Fig. 5) typical for Ni(I) compounds [22].
Consequently, in the course of time allyl complex 2 spontane-
ously decomposes in solution with reduction of Ni(II) to Ni(I). It is
important to note that the resulted paramagnetic complex is stable
in a sealed ampoule at room temperature during a year. The change
of nickel oxidation state is possible through breakup of either NieC
or NieN valent bonds. The absence of hyperfine structure from 14N
nuclei makes impossible unambiguous definition of the NieN bond
type for the paramagnetic complex. The analysis of the g-tensor
(gx ¼ 2.186, gy ¼ 2.143, gz ¼ 2.024) provides some information about
the complex structure. The ratio between its components (gx,
gy > gz) corresponds with a trigonal structure of the complex [23].
The greatest g-tensor component (2.186) is worth comparing with
similar parameters for the typical Ni(I) amide complexes of the
Scheme 1.
which in the course of two days is fully transformed into the final
product e paramagnetic complex 3.
The obtained results can be summarized as scheme (Scheme 2) of
the all studied transformations:The first step of the interaction
between the bis-
intermediate complex a haing at leastone h3
-form. Then the coordination sphere of complex a undergoes
p
-allyl complex and DAB is most likely to give
-p
-allyl groupin the h1
-
s
composition (Nacnac)NiL, where (Nacnac) is b-diketaminate, L is
a rearrangement which can be viewed as insertion of activated
unsaturated C]N bond into metalecarbon bond to form interme-
bis(diphenylphosphine)methane [24], tricyclohexylphosphine [24],
tetrahydrofurane [25]. Thus one can see that the greatest compo-
diate imineeamide
transfer, which can be regarded as conventional
intermediate hydride complexc. It seems to be in the h1
p
-allyl complex b. The following hydrogen atom
-transfer, gives
-allyl form
nents of the g-tensor for Ni(I)
b-diketaminate complexes
b
(2.43e2.54) differ significantly from the fair spin value despite the
fact that these complexes contain specrtochemically “stronger”
ligands as bis(diphenylphosphine)methane and tricyclohex-
ylphosphine. On the other hand, the same parameter, e.g. for Ni(I)
cyclopentadiene complex with bipyridine CpNi(bipy) (2.184 [26]),
is almost equal to the g-tensor component of the analyzed
substance. The above data allow us to assume that the spontaneous
decomposition of complex 2 and reduction of Ni(II) to Ni(I) are
associated with the transformation of NieN valent bond into
coordination one without allyl group elimination from the coor-
dination sphere. In this (Scheme 1) case structure 3 seems to be
most reasonable for the paramagnetic complex.
The assumption that diamagnetic nickel (II) complex 2 trans-
forms into paramagnetic nickel (I) complex 3 retaining the allyl
group in its structure is supported by the absence of any NMR
signals, other than those of the solvent, in the system when the ESR
signal is maximal. In the case of elimination of the allyl fragment,
NMR signals from propylene or its conversion products would be
registered (the transformation of 2 into 3 was examined in a sealed
NMR ampoule).
-s
taking into account the coordination numbers and geometry of its
ligands. At the same time it is especially important to note that the
formed intermediate hydride complex does not undergo the inter-
action between its hydride and allyl moieties to release propylene
into solution. Instead of this the hydrogen atom migrates to the
carbon atom of the amide fragment to form relatively stable nickel
(II) amide complex 1. This reverse hydrogen transfer from metal to
carbon is formally can be considered as hydrogenation of NeC bond
activated by nickel. In the course of time the 1-propenyl substituent
of complex 1 undergoes isomerization into the 2-propenyl form
with the formation of the stable system of conjugated double bonds
(imineeimide complex 2). The spontaneous formation of nickel (I)
complex 3 from nickel (II) complex 2 can be explained by the
equilibrium between the imineeamide h3
and hydride h1
-allyl form d. And as soon as it formed complex d is
spontaneously and irreversibly transformed into h3
-allyl nickel(I)
-p-allyl form of complex 2
-s
-p
complex 3. Note that at this step the formed hydride moiety also
does not react with allyl fragment in the nickel coordination sphere.
Thus the data obtained by us bear witness to the profound
transformation of the nitrogen-containing ligands in the coordina-
tion sphere of nickel allyl complexes. It is difficult to conceive of the
reported processes as not involving hydrogen migration and
formation of intermediate nickel hydride-organometallic complexes.
Besides, in our point of view it is of especial interest that the hydride
and olefin moieties can coexist in the nickel coordination sphere
without interaction via the reductive elimination of propylene and
formation of a nickel(0) complex. As can be seen from our data, the
system, initially formed from “hydrogen-deficient” nickel (II)
diamagnetic allyl complexes and containing no potential one-
electron reducers, spontaneously evolves toward the formation of
nickel (I) paramagnetic complexes which proved to be the final
products of the complicated and multistep route of spontaneous
transformations of the nickel (II) individual organometallic complex.
Thus diamagnetic nickel complex 1, sealed in an ampoule as
a THF solution, quiet readily isomerizes into diamagnetic complex 2
3. Experimental section
3.1. General procedures and materials
Standard vacuum techniques were used in manipulations of
volatile and air-sensitive materials. All solvents including deuteried
ones were produced by Merck.
Fig. 5. Experimental (a) and model (b) EPR spectra of the Ni(I) complex 3 (THF-D8, 77 K).

P.B. Kraikivskii et al. / Journal of Organometallic Chemistry 696 (2011) 3483e3490
3489
H
H
H
H
HC
N
CH
N
C
C
C
C
C
C
Ni(allyl)2
DAB
+
H
R
R
H
N
R
N
R
N
R
R
N
R
N
R
N
Ni
Ni
Ni
Ni
c
b
1
a
H
H
H
H
C
C
C
C
C
C
1/2H2
+
N
R
R
N
N
R
R
N
N
R
R
N
Ni
Ni
Ni
H
d
2
3
Scheme 2.
Infrared spectra were recorded for specimens pressed in KBr
tablets under argon with an Infralum FT-801 FT spectrometer. Mass
spectra were obtained with a Varian MAT spectrometer.
Decomp. 60e65 ꢁC. C32H46N2Ni (517.41): calc. C 74.28, H 8.96, N
5.41, Ni 11.34; found C 75.16, H 8.20, N 4.92.
HRMS
: C32H46N2Ni Calculated e 516.3014, Measured e
1H and 13C NMR spectra were obtained from a Bruker AVANCE
500. Assignment of 13C and 1H signals was supported by APT, DEPT,
COSY, NOESY, TOCSY, HMQC, HSQC, HMBC spectra. Melting points
were measured in capillaries sealed under argon and are uncor-
rected. The elemental analysis of the complexes was performed on
a FLACH 1112 analyzer (EA series).
EPR spectra were recorded with a CMS-8400 spectrometer
(operating frequency 9.6 GHz) at the temperature of boiling
nitrogen. The free radical diphenylpicrylhydrazyl (DPPH) and Mn2þ
in MgO were used for the calibration of the spectrometer. Simula-
tion of ESR spectra was done using WIN-EPR SimFonia, version 1.2.
A red single crystal of complex 1 (size 0.22 ꢂ 0.18 ꢂ 0.05 mm)
was used to obtain an array of experimental data with an automatic
diffractometer Smart Apex II, MoKa radiation. The structure was
solved by direct and conventional Fourier methods. All non-
hydrogen atoms were treated with a riding model in idealised
positions. Crystal data are presented in Table 2. The complete tables
of basis atom coordinates, bond lengths, and valent angles are
deposited in Cambridge Crystallographic Data Centre (# 819771,
deposit@ccdc.cam.ac.uk or http://www.ccdc.cam.ac.uk) and can be
obtained from the authors.
516.29939 (ꢀ2 mmu).
MS (70 eV): m/z (%) ¼ 41(24.9), 59(13.9), 186(13.0), 228(43.2),
418(33.4), 434(42.9), 476(100.0), 516(74.8).
IR (KBr) cmꢀ1: 3052(m), 3012(s), 2960(s), 2923(s), 2865(s),
2740(m), 2688(s), 1932(s), 1913(s), 1872(s), 1847(s), 1812(s), 1783(s),
1762(s), 1602(N]C,s) 1571(s), 1461(d), 1363(s), 1355(s), 1313(vs),
1253(s), 1105(nsCCC,s), 1076(vs), 987(vs), 919(s), 892(s), 794(s),
754(d), 568(s), 532(dCCC,s).
1H NMR (500 MHz, [D8]THF, 297 K):
d
¼ 6.9 (d, 1H, CH3,
3JH3eH4 ¼ 7.1 Hz), 6.8 (m,1H, CH4), 6.9 (d,1H, CH5, 3JH5eH4 ¼ 6.87 Hz),
4.3(d,1H, CH27, 2JH7 eH7 ¼ 26.5 Hz), 4.5(d,1H, CH270, JH7eH7 ¼ 27 Hz),
7.20 (m, 3H, CH11e13),1.67 (d,1H, CH215, 3JH15eH16 ¼ 5.98 Hz),1.61 (d,
1H, CH2150, 3JH15eH16 ¼ 13.2 Hz), 5.35 (m,1H, CH16),1.48 (d,1H, CH217,
3JH17eH16 ¼ 5.98 Hz), 1.40 (d, 1H, CH2170, 3JH17eH16 ¼ 14.3 Hz), 4.50 (m,
1H, CH18),1.38 (m, 6H, CH319, CH320), 3.86 (m,1H, CH21),1.31 (m, 6H,
CH322, CH323), 2.88 (m, 2H, CH224’), 5.73 (m, 1H, CH25), 5.01 (m, 2H,
2
0
0
Table 2
Crystal data for compound 1.
1
The Ni(allyl)2 complex and bis(2,6 -diisopropylphenyl)dia-
zabutadiene were prepared according to [2] and [27], respectively.
Empirical formula
Formula mass
Crystal size [mm]
Crystal system
Space group
a [Å]
C32 H46 N2 Ni
517.42
0.22 ꢂ 0.18 ꢂ 0.05
Monoclinic
P21/c
16.832(6)
10.939(4)
18.470(7)
116.46(2)
3044.7(19)
4
3.1.1. Complex 1 synthesis
A
cold solution (ꢀ5 ꢁC) of (2,6-diisopropylphenyl)dia-
b [Å]
zabutadiene (1.50 g, 4 mmol) in 100 ml of diethyl ether was slowly,
during 30 minutes, added by drops to a vigorously stirred solution
of Ni(allyl)2 (0.564 g, 4 mmol) in 100 ml of diethyl ether keeping
the temperature at ꢀ5 ꢁC. The resulting bright red reaction mixture
was kept at this temperature for additional 2 h followed by filtra-
tion. The filtrate was evaporated to give a bright red powder. This
was dissolved in 50 ml of pentane at ꢀ5 ꢁC. The solution was kept in
a refrigerator at ꢀ30 ꢁC for five days to obtain a crystalline
precipitate as thin bright red plates. The crystals were filtered off
at ꢀ30 ꢁC and dried in vacuum for 6 h at 10ꢀ2 mbar, 20 ꢁC. The
product is stable in argon but air-sensitive.
c [Å]
b
[ꢁ]
V [Å3]
Z
Dcalcd. [g/cm3]
1,129
0.658
240
m
(Mo-Ka)[mmꢀ1
]
Temperature [K]
Data coll. range [ꢁ]
h, k ,l max
No. reflect. measured
No. unique data
2.30 ꢃ ꢃ 28.05
q
21, 14, 24
20928
7168 (Rint ¼ 0.1354)
R1 [I ꢄ 2
s(I)]
wR2 (all data)
0.0520
0.1056
Yield 1.07 g (2.08 mmol), 52%.

3490
P.B. Kraikivskii et al. / Journal of Organometallic Chemistry 696 (2011) 3483e3490
CH226), 3.32 (m, 1H, CH27), 1.29 (m, 6H, CH328, CH329), 3.67 (m, 1H,
CH30), 1.22 (m, 6H, CH331, CH332) ppm.
139.06 (C10), 123.84 (C13), 139.53 (C14), 53.75 (C15), 106.43 (C16),
50.75 (C17), 28.02 (C18), 24.74 (C19), 26.07 (C20), 27.88 (C21),
25.02e25.9 (C22e23),123.46 (C24),139.49 (C25),18.47 (C26), 28.48
(C27), 23.95 (C28), 23.55 (C29), 28.67 (C30, HSQC 3.75), 23.37 (C31),
24.28 (C32) ppm.
13C NMR (125 MHz, [D8]THF, 297 K):
d
¼ 157.84 (C1), 147.87 (C2),
123.06 (C3), 123.54 (C4), 123.43 (C5), 146.33 (C6), 72.82 (C7), 191.36
(C8), 146.67 (C9), 124.41 (C11), 127.33 (C12), 124.67 (C13), 53.61
(C15), 106.39 (C16), 50.62 (C17), 28.44 (C18), 26.16; 26.34 (C19,
C20), 28.30 (C21), 24.49; 25.16 (C22, C23), 37.65 (C24), 132.44 (C25),
119.48 (C26), 29.09 (C27), 24.23; 24.14 (C28, C29), 29.29 (C30),
24.42; 24.57 (C31, C32) ppm.
(b) A solution of complex 1 in THF-D8 sealed in an NMR-tube was
monitored with NMR-DEPT 13C method using the signals of the
C27 atom (Fig. 2) as distinctive ones. After 3 h at 25 ꢁC the
signal at 119.48 ppm (complex 1) was completely replaced by
the signal at 19.27 ppm (complex 2). The transformation of
complex 1 into complex 2 is almost 100%.
3.1.2. Complex 2 synthesis
(a) A solution of complex 1 (2.58 g, 5 mmol) in 100 ml of diethyl
ether was kept in a Schlenk flask at 20e25 ꢁC for 5 h and then
evaporated to give a reddish-brown powder. This was dissolved
in 50 ml of pentane and kept in a refrigerator at ꢀ30 ꢁC for five
days to obtain an amorphous reddish-brown precipitate which
was filtered off and dried for 6 h at 10ꢀ2 mbar, 20 ꢁC. The
product is stable in argon but air-sensitive. Yield 1.99 g
(3.85 mmol), 77%. m.p. 97e100 ꢁC 60e65 ꢁC. C32H46N2Ni
(517.41): calc. C 74.28, H 8.96, N 5.41, Ni 11.34; found C 73.42, H
8.05, N 4.70. MS (70 eV): m/z (%) ¼ 31(12.1), 41(29.8), 59(18.8),
74(30.0), 186(13.56), 228(43.4), 418(32.4), 434(40.7),
476(100.0), 516(65.2).
Acknowledgements
This work was supported by the Federal Target Program
“Research and Training Specialists in Innovative Russia,
2009e2013”, (The contract # 14.740.11.0619 for 05.10. 2010). We
thank Vsevolod Sorokin for the design and making of exclusive
glass equipment for the experiments.
Supplementary material
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.jorganchem.2011.07.023.
IR (KBr) cmꢀ1: 3052(m), 3012(s), 2960(s), 2923(s), 2865(s),
2740(m), 2688(s), 1932(s), 1913(s), 1872(s), 1847(s), 1812(s), 1783(s),
1762(s), 1641(N]C, s), 1490(s), 1384(d), 1313(vs), 1253(s), 1218(s),
1205(s), 1076(nsCCC, vs), 987(vs), 919(s), 873(s), 794(s), 754(d),
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568(s), 532(
dCCC, s).
1H NMR (500 MHz, [D8]THF, 297 K):
d
¼ 6.97 (m, 1H, CH3), 6.84
(m, 1H, CH4), 6.94 (m, 1H, CH5), 4.79 (d, 1H, CH7), 4.57 (d, 1H, CH7’),
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3
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3
5.7 (d, 1H, CH24, JH24eH25 ¼16.4 Hz), 6.51 (dk, 1H, CH25,
3JH25eH26 ¼ 7.0 Hz; JH25eH24 ¼16.1 Hz), 1.64 (d, 3H, CH326,
3
3JH26eH24 ¼ 7.0 Hz), 3.37 (m, 1H, CH27, COSY 1.35; 1.37), 1.35 (m, 3H,
CH328), 1.37 (m, 3H, CH329), 3.66 (m, 1H, CH30), 1.11 (m, 3H,
CH331), 1.16 (m, 3H, CH332) ppm.
13C NMR (125 MHz, [D8]THF, 297 K):
d
¼ 158.17 (C1), 123.02 (C3),
123.53 (C4), 123.43 (C5), 146.54 (C6), 69.56 (C7), 184.13 (C8), 147.17
(C9), 139.71 (C10), 124.17 (C11), 127.13 (C12), 124.43 (C13), 140.20
(C14), 53.97 (C15), 106.7 (C16), 50.71 (C17), 28.45 (C18), 26.10 (C19),
26.26 (C20), 28.28 (C21), 24.89; 25.15 (C22, C23), 124.18 (C24),
140.88 (C25), 19.26 (C26), 29.22 (C27), 23.78 (C28), 24.00 (C29),
29.42 (C30), 24.28 (C31), 24.62 (C32) ppm.
1H NMR (500 MHz, [D8] C6D6, 297 K):
d
¼ 7.28 (d, 1H, CH3,
3JH3eH4 ¼7.3 Hz), 7.23 (m, 1H, CH4), 1.62 (d, 1H, CH5,
JH5eH4 ¼7.2 Hz), 4.67 (d, 1H, CH27, 2JH7 eH7 ¼ 25.30 Hz), 4.90 (d, 1H,
3
0
2
CH270, JH7eH7 ¼ 25.0 Hz), 7.06 (m, 3H, CH11-CH13), 1.83 (d, 1H,
0
CHa2nti15,
3JH15eH16 ¼ 13 Hz),
1.62
(d,
1H,
CHs2yn15,
ꢀ
(b) G. Wilke, B. Bogdanovic, P. Hardt, P. Heimbach, W. Keim, M. Kröner,
W. Oberkirch, K. Tanaka, E. Steinrücke, D. Walter, H. Zimmermann, Angew.
Chem. Int. Edit. 5 (1966) 151.
3JH15eH16 ¼ 6.0 Hz), 5.46 (m, 1H, CH16), 2.00 (d, 1H, CHs2yn17,
3JH17eH16 ¼ 4.3 Hz), 1.79 (d, 1H, CHa2nti17, JH17eH16 ¼ 13.0 Hz), 4.81
3
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3
(m, 1H, CH18), 1.47 (d, 3H, CH319, JH19eH18 ¼ 6.7 Hz), 1.53 (d, 3H,
3
CH320, JH20eH18 ¼ 6.7 Hz), 4.14 (m, 1H, CH21), 1.41 (m, 6H, CH322,
3
CH323), 5.64 (d, 1H, CH24, JH24eH25 ¼16.0 Hz), 5.87 (dk,
3JH25eH26 ¼ 6.45 Hz, 1H, CH25, JH25eH24 ¼16.2 Hz), 0.94 (d, 2H,
3
CH226, 3JH26eH25 ¼ 6.54 Hz), 3.46 (m, 1H, CH27), 1.1 (m, 3H, CH328),
1.28 (m, 3H, CH329), 3.75 (m, 1H, CH30), 1.27 (m, 3H, CH331), 1.15
(m, 3H, CH332) ppm.
13C NMR (125 MHz, [D8] C6D6, 297 K):
d
¼ 157.63 (C1), 123.23
(C3), 123.25 (C5), 146.0 (C6), 69.4 (C7), 183.13 (C8), 146.47 (C9),
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