Synthesis of 2-(N-arylimino-κN-methyl)pyrrolide-κN complexes of nickel

Article abstract of DOI:10.1016/j.jorganchem.2008.09.067

2-(N-aryliminomethyl)pyrrole precursors (2,6-R₂-C₆H₃-N{double bond, long}CH-2-C₄H₃NH) (R = Me, IH; R = ⁱPr, IIH) were prepared and transformed into their corresponding sodium salts (Na⁺I^- and Na⁺II^-) by treatment with NaH. Both salts readily react with [NiBr₂(DME)] (DME = 1,2-dimethoxyethane) to give the respective bis{2-(N-arylimino-κN-methyl)pyrrolide-κN}nickel(II) complexes (1, 2) in almost quantitative yields. The oxidative addition of IH to [Ni(COD)₂] (COD = 1,5-cyclooctadiene) results in the formation of 3, which is a mono(iminomethylpyrrolide)-η³-(cyclic-allyl)-type organonickel(II) complex. The crystal structure of compound 1 has been established by X-ray diffraction studies.

Full text of DOI:10.1016/j.jorganchem.2008.09.067

Journal of Organometallic Chemistry 693 (2008) 3902–3906
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Synthesis of 2-(N-arylimino-
jN-methyl)pyrrolide-jN complexes of nickel
*
*
Pilar Pérez-Puente, Ernesto de Jesús , Juan C. Flores , Pilar Gómez-Sal
Departamento de Química Inorgánica, Universidad de Alcalá, Campus Universitario, 28871 Alcalá de Henares, Madrid, Spain
a r t i c l e i n f o
a b s t r a c t
2-(N-aryliminomethyl)pyrrole precursors (2,6-R2-C6H3-N@CH-2-C4H3NH) (R = Me, IH; R = iPr, IIH) were
prepared and transformed into their corresponding sodium salts (Na+Iꢀ and Na+IIꢀ) by treatment with
NaH. Both salts readily react with [NiBr2(DME)] (DME = 1,2-dimethoxyethane) to give the respective
Article history:
Received 9 July 2008
Received in revised form 12 September
2008
Accepted 30 September 2008
Available online 8 October 2008
bis{2-(N-arylimino-
The oxidative addition of IH to [Ni(COD)2] (COD = 1,5-cyclooctadiene) results in the formation of 3, which
is a mono(iminomethylpyrrolide)-
3-(cyclic-allyl)-type organonickel(II) complex. The crystal structure
jN-methyl)pyrrolide-jN}nickel(II) complexes (1, 2) in almost quantitative yields.
g
of compound 1 has been established by X-ray diffraction studies.
Keywords:
N ligands
Chelating ligands
Nickel
Ó 2008 Elsevier B.V. All rights reserved.
Allyl
Imine
Pyrrolide
1. Introduction
2. Results and discussion
The synthesis of new transition-metal complexes containing
chelating imine ligands was stimulated by the reports of Brookhart
[1], Gibson [2], Fujita [3] and Coates [4] regarding their usefulness
in catalysis. Considerable effort has since been made to expand the
number of both late and early transition-metal complexes with dif-
ferent chelating ligand frameworks [5]. For instance, asymmetrical
N/N pyridylimine-type compounds have been synthesised and
used in catalysis [6], organic synthesis [7], and biomedical studies
[8], and we have recently also applied such metal complexes in
dendrimer chemistry [9]. The number of closely related imi-
nomethylpyrrolide metal complexes is, however, relatively scarce,
despite the fact that these complexes contain an isosteric fragment
of pyrromethenes and porphyrins. Significant results have been re-
ported for bis(chelate) group 4 [10], or chromium [11], as well for
mono(chelate) group 10 metal complexes and closely related spe-
cies [12]. Herein we describe the straightforward synthesis and
2.1. Synthesis and characterisation
The 2-(N-aryliminomethyl)pyrrole precursors IH and IIH were
synthesised according to previously described procedures [12]
and deprotonated with NaH in THF (Scheme 1). After filtration
and removal of the solvent in vacuum, Na+Iꢀ and Na+IIꢀ were iso-
lated as white, solvent-free solids which can be stored indefinitely
in a dry-box. However, they are moisture-sensitive in both the so-
lid state and in solution, and hydrolyse back to the protonated pre-
cursors upon exposure to air.
The nickel complexes 1 and 2 were prepared by treatment of
[NiBr2(DME)] (DME = 1,2-dimethoxyethane) with the correspond-
ing iminomethylpyrrolide ligand in a 1:2 molar ratio in acetonitrile
(Scheme 1). These bis-chelate metal complexes were isolated in
very high yields (>90%) as red, crystalline, air-stable solids which
are soluble in chlorinated solvents and acetonitrile. The Holm
and Barbier groups have described the synthesis of related N-aryl
or N-alkyl bis(iminomethylpyrrolide)nickel(II) complexes by treat-
ment of [NEt4]2[NiBr4] with the appropriate Schiff base (deproto-
nated in situ with KOtBu) in dry THF [13]. However, the yields
reported are below 30% and the workup procedure is more compli-
cated. More recently, Gomes [12b], Dyer [12f] and Bochmann [12g]
have also reported the incidental formation of bis(N-mes-
ityliminopyrrolide)nickel(II) complexes. In fact, the latter author
characterised compound 2 by 1H NMR, which was isolated in much
lower yield (15%) after the reaction of one equivalent of Li+IIꢀ
characterisation of bis{2-(N-arylimino-jN-methyl)pyrrolide-jN}
complexes of nickel, as well as the identification of a mono-chelate
derivative.
* Corresponding authors. Tel.: +34 91 885 4607; fax: +34 91 885 4683 (J.C.
Flores).
E-mail addresses: ernesto.dejesus@uah.es (E. de Jesús), juanc.flores@uah.es
(J.C. Flores).
0022-328X/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2008.09.067

P. Pérez-Puente et al. / Journal of Organometallic Chemistry 693 (2008) 3902–3906
3903
Access to mono(iminomethylpyrrolide) nickel complexes is
more difficult because the formation of bis(chelate) complexes
seems to be favoured, which means that these latter compounds
often appear as impurities or even as the only product during at-
tempts to prepare mono(chelate) complexes [12b,c]. The only
effective procedures reported to date are those by Gomes [12b]
and Li [12c]. We attempted the reaction of equimolar amounts
of Na+Iꢀ or Na+IIꢀ with [NiBr2(DME)] in the presence of PPh3
but only obtained mixtures of the corresponding bis-chelate 1
or 2 together with [NiBr2(PPh3)2]. The reaction of pyrrole IH with
[Ni(COD)2] (COD = 1,5-cyclooctadiene) in an NMR tube proved
more successful however. The spectra of an equimolar mixture
in C6D6 showed no reaction at room temperature or at 60 °C,
but complete transformation into a new compound, subsequently
identified as complex 3, and free COD was observed after heating
at 120 °C for 30 min (Scheme 1). Compound 3 formally results
from decoordination of a COD ligand in [Ni(COD)2], oxidative
addition of IH to the nickel centre, insertion of one double bond
of the coordinated COD ligand into the Ni–H bond, and isomerisa-
R
R
R
R
—
Na+
N
N
N
N
N
N
R
R
1/2 [NiBr2(DME)]
MeCN
Ni
Na+I— (R = Me)
Na+II— (R = iPr)
1 (R = Me)
2 (R = iPr)
NaH THF
R
Me
N
N
N
NH
[Ni(COD)2]
C6D6
Ni
Me
R
IH (R = Me)
IIH (R = iPr)
3
tion of the resulting cyclooctenyl ligand to give an
g
3-allyl-type
Scheme 1.
organonickel complex. Similar species have been proposed as
intermediates in catalytic reactions and have been identified by
NMR spectroscopy from the in situ oxidative addition of phospha-
nylphenols (P, O ligand precursors) to [Ni(COD)2] [14]. Unfortu-
nately, the same reaction carried out on a larger scale at 120 °C
in toluene led to the formation of a Ni(0) mirror and a solution
containing a mixture of 3 (minor) and IH which could not be
separated.
Characterisation of 3 in the C6D6 reaction solution was carried
out by 1H and {1H,1H} COSY NMR experiments. The 1H NMR res-
onances assigned to the pyrrolide (d 6.55, 5.98 and 5.05 for H7, H8
and H9, respectively) and imine protons (d 6.06) in 3 are shifted
to high field upon coordination, in agreement with the CIS effects
discussed above. The resonances at d 5.09, 3.73 and 2.79, together
with several multiplets observed in the aliphatic region, corre-
(generated in situ from IIH and LinBu) and [NiBr2(DME)] in diethyl
ether at 0 °C.
Complexes 1 and 2 were characterised by 1H and 13C NMR spec-
troscopy, elemental analyses and mass spectrometry (see Section 4
for details). The crystal structure of 1 was determined by X-ray dif-
fraction studies (see below). Both bidentate ligands are equivalent
in the 1H and 13C NMR spectra, but the methyl groups of each iso-
propyl substituent in compound 2 are diastereotopic due to slow
rotation around the N-aryl bond on the NMR time scale.
It has been documented that bis(iminomethylpyrrolide) nicke-
l(II) complexes experiment planar M tetrahedral endothermic
equilibria, with topological populations intermediate or at either
of the two extremes, depending on the steric properties of the
N–R substituent [13]. The 1H and 13C chemical shifts observed for
1 and 2 are in the normal diamagnetic range, which is in agree-
ment with a square-planar coordination for nickel in solution sim-
ilar to that observed in the solid state for 1 (see below). On the
other hand, important CIS effects (CIS = coordination-induced
shift) are observed for the proton and carbon-13 resonances of
the coordinated ligands when compared with their protonated pre-
cursors due to factors such as rehybridisation to accommodate the
bite angle of the ligand, charge changes in the monoanionic pyrrol-
yl ring and in the coordinated imine group, or ring current and con-
jugation perturbations. The sign of the CIS effects is opposite for
spond to an allylic
g
3-coordinated C8H13 ring, as evidenced by
selective 1H,1H decoupling and {1H,1H} COSY experiments. In
addition to the corresponding cross-peaks between the pyrrolide
protons, these experiments showed no coupling between the
0
0
doublet of triplets at d 2.79 and 3.73 (H1 and H3 , Fig. 1). How-
ever, clear cross-peaks were0 observed between these resonances
and the triplet at d 5.09 (H2 , J = 8.0 Hz), which appears partially
overlapped by the H9 pyrrolide proton. The chemical inequiva-
lence of the allylic 1,3 protons means that the allyl ligand is
not fluxional (rotation or
ture. Gomes has described the synthesis of two related [Ni(N-
mesityliminomethylpyrrolide)(
3-C3H5)] complexes by treatment
of the sodium salt of the ligand and [Ni( -Br)]2 [12b]. In
3-C3H5)(
p–r–p conversion) at room tempera-
protons (Dd < 0) and carbon atoms (Dd > 0) and, as expected, the
most affected shifts are those of the metallacycle and the proton
in position 9 of the pyrrolide ring (Table 1).
g
g
l
agreement with this work, we tentatively assign the resonance
Table 1
Relevant CIS effects observed by NMR spectroscopy for compounds 1 and 2.a
7
2 R
8
9
3
6
5
4
1
N
N
R = Me (1), Pr (2)
R
Complex
D
db
H5
H7
H8
H9
C5
C6
C7
C8
C9
C1
1
2
ꢀ1.10
ꢀ1.06
ꢀ0.02
ꢀ0.05
ꢀ0.44
ꢀ0.50
ꢀ1.74
ꢀ1.83
+9.1
+9.3
+10.5
+9.8
+1.8
+2.0
+2.5
+2.3
+13.3
+14.3
ꢀ3.4
ꢀ3.6
a
In CDCl3 at 20 °C.
b
D
d in ppm with respect to the corresponding free ligands IH or IIH.

3904
P. Pérez-Puente et al. / Journal of Organometallic Chemistry 693 (2008) 3902–3906
Fig. 2. Molecular structure of complex 1.
Table 2
Selected bond lengths (Å) and angles (°) for compound 1.
Ni(1)–N(1)
Ni(1)–N(3)
Ni(1)–N(2)
Ni(1)–N(4)
N(1)–C(1)
N(1)–C(4)
N(2)–C(5)
N(2)–C(11)
C(4)–C(5)
N(3)–C(6)
N(3)–C(9)
N(4)–C(10)
N(4)–C(21)
C(9)–C(10)
1.914(2)
1.916(2)
1.929(2)
1.932(3)
1.365(4)
1.379(4)
1.313(4)
1.454(4)
1.411(4)
1.367(4)
1.385(4)
1.316(4)
1.439(4)
1.402(4)
N(1)–Ni(1)–N(3)
N(2)–Ni(1)–N(4)
N(1)–Ni(1)–N(2)
N(3)–Ni(1)–N(4)
N(2)–Ni(1)–N(3)
N(1)–Ni(1)–N(4)
Ni(1)–N(1)–C(4)
Ni(1)–N(2)–C(5)
N(1)–C(4)–C(5)
C(4)–C(5)–N(2)
C(5)–N(2)–C(11)
C(9)–N(3)–Ni(1)
C(10)–N(4)–C(21)
C(10)–N(4)–Ni(1)
C(21)–N(4)–Ni(1)
N(3)–C(9)–C(8)
N(3)–C(9)–C(10)
N(4)–C(10)–C(9)
173.11(11)
173.28(11)
83.53(10)
83.48(11)
97.34(10)
96.47(11)
113.00(19)
112.8(2)
113.3(3)
117.3(3)
116.7(3)
112.27(19)
118.5(3)
113.0(2)
Fig. 1. {1H,1H} COSY spectrum of the
g
3-allyl region for 3.
128.2(2)
110.5(3)
113.8(3)
116.9(3)
found at d 3.73 to the allylic syn-proton closest to the pyrrolide
ring (H3).
Complexes 1 and 2, activated by IPMAO, and 3 were evaluated
as ethylene polymerisation catalysts (room temp., 2 bar, toluene,
24 h, Al/Ni = 1000). Only traces of sticky polymer were observed
in the case of the bis(chelate) compounds.
which is consistent with a somewhat greater nickel-to-ligand
p-
back-donation in the bis-chelate compound. Gomes has analysed
the structural differences between free and coordinated ligands
and has found that coordination results in an acute N–Ni–N an-
gle (ca. 83°) at the expense of different angle accommodations
observed for the imine-pyrrolide moiety [12b]. Since the ligand
bite angle in 1 [N(1)–Ni(1)–N(2) 83.52(10)° and N(3)–Ni(1)–
N(4) 83.48(11)°] and the other angles in the -N@CH-C4H3N- moi-
ety are fairly similar [e.g., C(1)–N(1)–C(4) 105.7(3)°], we conclude
that ligand distortion upon coordination also occurs in the
bis(chelate)nickel(II) complexes described here.
2.2. Crystal structure of complex 1
The molecular structure of complex 1 in the solid state, as
determined by single-crystal X-ray diffraction studies, is shown
in Fig. 2; selected bond lengths and angles are listed in Table
2. The molecule is monomeric, has non-crystallographic C2 sym-
metry, and resembles that found for similar Cr(II) [11], Pd(II)
[12a] or Ni(II) [12f] bis-chelate complexes. The geometry at the
Ni atom is approximately square-planar, with cis angles in the
range 83.48(11)–97.34(10)°. The four nitrogen atoms deviate
slightly from the mean plane [N(1) and N(3) 0.11, N(2) ꢀ0.10,
and N(4) ꢀ0.12 Å] with Ni(1) lying in the plane. The complex
adopts a trans configuration, probably due to steric constraints,
3. Conclusions
An efficient and simple procedure for the synthesis of bis(imi-
nopyrrolide)nickel(II) complexes, which involves treatment of the
sodium salt of the N,N0-ligand with [NiBr2(DME)], is reported in
this work. The N-aryl-iminopyrrolide compounds 1 and 2 are found
to be in a square-planar geometry both in the solid state and in
solution. The mono(iminopyrrolide) complex 3 has been identified
from the reaction of [Ni(COD)2] and N-(2,6-dimethylphenyl)imino-
pyrrole, and its characterisation indicates the formal oxidative
with
N(1)–Ni(1)–N(3)
and
N(2)–Ni(1)–N(4)
angles
of
173.11(11)° and 173.28(11)°, respectively. The pyrrolide ring
and the metallacycle of each ligand are co-planar to within
0.07 and 0.027 Å but have a dihedral angle of 13.13° between
them. The 2,6-dimethylphenyl rings tend to lie orthogonal
(76.05° and 73.60°) to the molecular plane, with Ni(1)–N(4)–
C(21)–C(22) and Ni(1)–N(2)–C(11)–C(12) torsion angles of
ꢀ66.2° and ꢀ71.3°, respectively. The Ni–N distances in complex
1 are slightly shorter than those of related mono-chelate com-
plexes [12b,c], whereas the imine double bond is slightly longer,
addition of the pyrrole to [Ni(COD)2] to give an
g
3-(cyclic allyl)-
type organonickel(II) complex. This compound also displays a
pseudo-planar symmetry with some rigidity of the coordinated
cyclic allyl ligand.

P. Pérez-Puente et al. / Journal of Organometallic Chemistry 693 (2008) 3902–3906
3905
procedure to that described for 1, starting from Na+IIꢀ
(361 mg, 1.31 mmol) and [NiBr2(DME)] (202 mg, 0.65 mmol) in
MeCN (30 mL). Yield: 338 mg (92%). Anal. Calc. for C34H42N4Ni
(565.43): C, 72.22; H, 7.49; N, 9.91. Found: C, 72.28; H, 7.40;
4. Experimental
4.1. Reagents and general techniques
i
N, 9.85%. 1H NMR (CDCl3): d 1.19 (d, JH,H = 6.9 Hz, 6H, Pr), 1.23
All operations were performed under argon using Schlenk or
dry-box techniques. Unless otherwise stated, reagents were ob-
tained from commercial sources and used as received. Com-
pounds IH and IIH and their sodium salts (Na+Iꢀ and Na+IIꢀ)
were synthesised by adapting reported procedures [12], and
[NiBr2(DME)] (DME = 1,2-dimethoxyethane) [15] was prepared
as described in the literature. Solvents were dried prior to use
and distilled under argon as described elsewhere [16]. NMR spec-
tra were recorded with Varian Unity VR-300 or Varian Unity 200
NMR spectrometers. Chemical shifts (d) are reported in ppm rel-
ative to SiMe4, and were measured relative to the 13C and residual
1H resonances of the deuterated solvents. Assignments for the
aryl-iminopyrrolide fragments are given according to the num-
bering depicted in Table 1. Elemental analyses and APCI mass
spectra were performed by the Microanalytical Laboratories of
the University of Alcalá with a Heraeus CHN-O-Rapid microana-
lyzer and a Thermo Quest Finningan Automass Multi mass spec-
trometer, respectively.
(d, JH,H = 6.9 Hz, 6H, iPr), 4.41 (sept, JH,H = 6.9 Hz, 2H, iPr), 4.68
(broad s, 1H, H9), 5.71 (dd, J8,7 = 3.7, J8,9 = 1.8 Hz, 1H, H8), 6.54
(dd, J7,8 = 3.7, J7,9 = 0.9 Hz, 1H, H7), 6.87 (s, 2H, H5), 7.13 (m,
1H, H4), 7.28 (m, 4H, H3). 13C{1H} NMR (CDCl3): d 22.7 and
24.7 (CHMe2), 28.8 (CHMe2), 112.3 (C8), 118.0 (C7), 123.8 (C3),
127.2 (C4), 137.6 (C9), 140.0 (C6), 143.5 (C2), 145.0 (C1),
161.5 ppm (C5). MS (APCI in CH3CN): m/z 566 [M+H]+, 394
[MꢀII+2MeCN]+, 354 [MꢀII+MeCN+H]+, 296 [IIH+MeCN+H]+,
255 [IIH+H]+.
Spectroscopic data for Na+IIꢀ: 1H NMR (CDCl3): d 1.08 (d,
i
i
JH,H = 6.9 Hz, 12H, Pr), 3.01 (sept, JH,H = 6.9 Hz, 2H, Pr)), 6.29 (dd,
J8,9 = 3.3, J8,7 = 2.2 Hz, 1H, H8), 6.65 (dd, J7,8 = 3.3, J7,9 = 1.0 Hz, 1H,
H7), 6.91 (broad s, 1H, H9), 7.11 (overlapped m, 3H, H3,4), 7.91 (s,
1H, H5).
4.4. Identification of [(1–3-g)cycloocta-2-en-1-yl]{2-[N-(2,6-
dimethylphenyl)imino- N-methyl]pyrrolide-
j
j
N}nickel (3)
Compound
[Ni(COD)2] (10 mg, 36.3
36.3 mol) were weighed in a dry-box and combined with C6D6
3
was prepared in an NMR-scale experiment.
4.2. Preparation of bis{2-[N-(2,6-dimethylphenyl)imino-
jN-
l
mol) and iminopyrrole IH (7.2 mg,
methyl]pyrrolide- N}nickel (1)
j
l
(0.8 mL) at room temperature. The solution was transferred to an
NMR tube with PTFE valve, the tube was sealed, and the 1H NMR
spectrum of the sample was recorded soon after. This spectrum
showed peaks corresponding to the unreacted starting materials.
The tube was then immersed in an oil bath at 120 °C for 30 min
and the spectrum was recorded again. The initial yellow solution
turned dark orange during heating, and the new spectrum indi-
cated the total consumption of IH and [Ni(COD)2] and the presence
of free 1,5-COD and a new complex characterised as compound 3.
1H NMR (C6D6): d 1.0–1.2 (m, 4H, CH2), 1.3–1.6 (m, 4H, CH2), 1.6–
1.7 (m, 2H, CH2), 2.20 (s, 12H, Me), 2.44 (broad s, free COD), 2.79
NaH (60% in mineral oil; 202 mg, 5.05 mmol) was washed with
pentane (2 ꢁ 10 mL) in a Schlenk tube and then treated with a THF
solution (20 mL) of ligand IH (1000 mg, 5.04 mmol) at room tem-
perature. A bubbler was fitted to the tube and, after gas evolution
had ceased, the mixture was stirred for an additional 5 h. The
resulting colourless solution was filtered, pumped to dryness un-
der vacuum, and the crude residue washed with pentane
(2 ꢁ 15 mL) to afford Na+Iꢀ as a white solid, which was stored in
a dry-box. [NiBr2(DME)] (375 mg, 1.22 mmol) was added to an or-
ange solution of Na+Iꢀ (537 mg, 2.44 mmol) in MeCN (50 mL) at
room temperature. The mixture changed instantaneously to a
brownish colour and was stirred for 24 h. After filtration of the
NaCl by-product, the red solution was concentrated to half of its
initial volume and cooled to ꢀ20 °C overnight to afford complex
1 as a red-brown crystalline solid. Concentration and cooling of
the mother liquor gave a second crop of crystals. Yield: 517 mg
(94%, relative to Ni). Anal. Calc. for C26H26N4Ni (453.21): C,
68.90; H, 5.78; N, 12.36. Found: C, 68.97; H, 5.78; N, 12.31%. 1H
NMR (CDCl3): d 2.63 (s, 6H, Me), 4.65 (broad s, 1H, H9), 5.74 (dd,
J8,7 = 3.7, J8,9 = 1.6 Hz, 1H, H8), 6.57 (dd, J7,8 = 3.7, J7,9 = 1.0 Hz, 1H,
H7), 6.87 (s, 1H, H5), 7.0–7.2 (overlapped m, 3H, H3,4). 13C{1H}
NMR (CDCl3): d 19.2 (Me), 112.5 (C8), 118.2 (C7), 126.5 (C4),
128.4 (C3), 133.4 (C2), 136.9 (C9), 140.6 (C6), 147.3 (C1), 162.0
ppm (C5). MS (APCI in CH3CN): m/z 454 [M+H]+, 338
[MꢀI+2MeCN]+, 297 [MꢀI+MeCN+H]+, 255 [MꢀI]+, 240 [IH+
MeCN+H]+, 199 [IH+H]+.
(dt, 3JH,Hcentral = 8.0, 3JH,H = 8.0 Hz, 1H, allyl-H), 3.73 (dt, 3JH,Hcentral
=
3
8.0, JH,H = 8.0 Hz, 1H, allyl-H), 5.05 (broad s, 1H, H9), 5.09 (t,
3JH,Hsyn 3JH,Hsyn = 8.0 Hz, 1H, allyl-Hcentral), 5.57 (broad s, free
,
COD), 5.98 (dd, J8,7 = 3.8, J8,9 = 1.8 Hz, 1H, H8), 6.06 (s, 1H, H5),
6.55 (dd, J7,8 = 3.8, J7,9 = 0.9 Hz, 1H, H7), 6.8–7.0 (overlapped m,
3H, H3,4).
4.5. X-ray crystallographic studies
Suitable single crystals of 1 were obtained by cooling a concen-
trated solution in acetonitrile to ꢀ20 °C overnight. A summary of
crystal data and data collection and refinement parameters for
the structural analysis is given in Table 3.
A red crystal of suitable size was glued to a glass fibre using an
inert polyfluorinated oil and mounted in the N2 stream of a Bruker-
Nonius Kappa-CCD diffractometer equipped with an area detector
and an Oxford Cryostream 700 unit; data were collected using
Spectroscopic data for Na+Iꢀ: 1H NMR (CDCl3): d 2.04 (s, 6H,
Me), 6.28 (t, J8,7 ꢂ J8,9 ꢂ 3.0 Hz, 1H, H8), 6.60 (d, J7,8 = 3.0 Hz, 1H,
H7), 6.91 (m, 1H, H4), 6.95 (broad s, 1H, H9), 7.03 (overlapped m,
2H, H3), 7.94 (s, 1H, H5).
graphite-monochromated Mo Ka radiation (k = 0.71073 Å). Inten-
sities were collected at 200 K, with an exposure time of 6 s per
frame [6sets; 568frames; phi and omega scan (1.3° scan width)]
and were corrected for Lorenz and polarisation effects in the usual
manner. No extinction or absorption corrections were made. The
structure was solved by direct methods, completed by subsequent
difference Fourier techniques, and refined by full-matrix least-
4.3. Preparation of bis{2-[N-(2,6-diisopropylphenyl)imino-
methyl]pyrrolide- N}nickel (2)
jN-
j
The sodium salt Na+IIꢀ was prepared as described above for
Na+Iꢀ, starting from NaH (60% in mineral oil; 157 mg,
3.93 mmol) and ligand IIH (1000 mg, 3.39 mmol), and isolated
as a white solid, which was stored in a dry-box. Compound 2
was isolated as a red microcrystalline solid following a similar
squares procedures on F2
(SHELXL-97) [17]. Anisotropic thermal
parameters were used in the last cycles of refinement for the
non-hydrogen atoms. Some of the hydrogen atoms were located
in the Fourier map and refined isotropically; the remainder were

3906
P. Pérez-Puente et al. / Journal of Organometallic Chemistry 693 (2008) 3902–3906
Table 3
References
Crystal data and structure refinement for compound 1.
[1] L.K. Johnson, C.M. Killian, M. Brookhart, J. Am. Chem. Soc. 117 (1995) 6414.
[2] G.J.P. Britovsek, V.C. Gibson, B.S. Kimberley, P.J. Maddox, S.J. McTavish, G.A.
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Tsuru, M. Nitabaru, T. Nakano, H. Tanaka, N. Kashiwa, T. Fujita, J. Am. Chem.
Soc. 123 (2001) 6847. and references cited therein.
[4] J. Tian, P.D. Hustand, G.W. Coates, J. Am. Chem. Soc. 123 (2001) 5134. and
references cited therein.
[5] (a) V.C. Gibson, S.K. Spitzmesser, Chem. Rev. 103 (2003) 283;
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Organomet. Chem. 606 (2000) 112;
(b) A. Köppl, H.G. Alt, J. Mol. Catal. A: Chem. 154 (2000) 45;
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(b) K. Heinze, V. Jacob, C. Feige, Eur. J. Inorg. Chem. (2004) 2053.
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J.E. Enman, S.J. Scales, H. Zhang, C.M. Vogels, M.T. Saleh, A. Decken, S.A.
Westcott, Inorg. Chim. Acta 358 (2005) 63;
(b) G. García-Friaza, A. Fernández-Botello, J.M. Pérez, M.J. Prieto, V. Moreno, J.
Inorg. Biochem. 100 (2006) 1368.
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Commun. (2005) 5217;
Empirical formula
Formula weight
Color
Temperature (K)
Wavelength (Å)
Crystal system, space group
Unit cell dimensions
a (Å)
C26H26N4Ni
453.22
Red
200.0(2)
0.71073
Orthorhombic, P212121
11.1326(3)
8.4240(7)
24.529(3)
2300.4(3)
4, 1.309
0.863
952
b (Å)
c (Å)
Volume (Å3)
Z, Calculated density (g/cm3)
Absorption coefficient mmꢀ1
F(000)
Crystal size (mm3)
h range (°)
0.35 ꢁ 0.25 ꢁ 0.25
3.03–27.54
Limiting indices
ꢀ14 ꢃ h ꢃ 14, ꢀ10 ꢃ k ꢃ 10,
ꢀ31 ꢃ l ꢃ 31
46074/5277 [0.1302]
99.8%
Reflections collected/unique [R(int)
Completeness to h = 27.54°
Refinement method
]
Full-matrix least-squares on F2
5277/0/308
Data/restraints/parameters
Goodness of fit on F2
0.912
(b) J.M. Benito, E. de Jesús, F.J. de la Mata, J.C. Flores, R. Gómez, P. Gómez-Sal,
Organometallics 25 (2006) 3876;
(c) J.M. Benito, E. de Jesús, F.J. de la Mata, J.C. Flores, R. Gómez,
Organometallics 25 (2006) 3045;
(d) J.M. Benito, E. de Jesús, F.J. de la Mata, J.C. Flores, R. Gómez, J. Organomet.
Chem. 683 (2008) 278.
Final Ra indices [I > 2
R indices (all data)
r
(I)]
R1 = 0.0439, wR2 = 0.0823
R1 = 0.0846, wR2 = 0.0908
ꢀ0.015(15)
Absolute structure parameter
Largest difference peak and hole (e/Å3) 0.434 and ꢀ0.322
P
P
2
1=2
a
[10] (a) For leading references see: K.P. Bryliakov, E.A. Kravtsov, L. Broomfield, E.P.
Talsi, M. Bochmann, Organometallics 26 (2007) 288;
(b) Y. Yoshida, S. Matsui, T. Fujita, J. Organomet. Chem. 690 (2005) 4382.
[11] V.C. Gibson, C. Newton, C.R. Redshaw, G.A. Solan, A.J.P. White, D.J. Williams, J.
Chem. Soc., Dalton Trans. (2002) 4017.
R1
=
R
||Fo| ꢀ |Fc||/
R
|Fo|; wR2 ¼ ½
x
ðF2o ꢀ F2c Þꢄ=½
x
ðF2oÞ ꢄ
.
included from geometrical calculations and refined using a riding
model. All the calculations were made using the WINGX system
[18].
[12] (a) For leading references see: H. Liang, J. Liu, X. Li, Y. Li, Polyhedron 23 (2004)
1619;
(b) R.M. Bellabarba, P.T. Gomes, S.I. Pascu, Dalton Trans. (2003) 4431;
(c) Y.-S. Li, Y.-R. Li, X.-F. Li, J. Organomet. Chem. 667 (2003) 185;
(d) G. Tian, P.D. Boyle, B.M. Novak, Organometallics 21 (2002) 1462;
(e) G. Tian, H.W. Boone, B.M. Novak, Macromolecules 34 (2001) 7656;
(f) C.E. Anderson, A.S. Batsanov, P.W. Dyer, J. Fawcett, J.A.K. Howard, Dalton
Trans. (2006) 5362;
Supplementary material
CCDC 694280 contains the supplementary crystallographic
data for 1. These data can be obtained free of charge from The Cam-
bridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/da-
ta_request/cif.
(g) D.M. Dawson, D.A. Walker, M. Thornton-Pett, M. Bochmann, Dalton Trans.
(2000) 459.
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(b) A. Mohamadou, J.-P. Barbier, R. Hugel, Polyhedron 11 (1992) 2697.
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Am. Chem. Soc. 126 (2004) 14960;
(b) J. Heinicke, M. Köhler, N. Peulecke, M. He, M.K. Kindermann, W. Keim, G.
Fink, Chem. Eur. J. 9 (2003) 6093.
Acknowledgments
[15] L.G.L. Ward, Inorg. Synth. 13 (1972) 154.
[16] D.P. Perrin, W.L.F. Armarego, Purification of Laboratory Chemicals, 3rd ed.,
Pergamon Press, Oxford, 1988.
[17] G.M. Sheldrick, SHELXL-97. Program for Crystal Structure Refinement, University
of Göttingen, Germany, 1997.
We gratefully acknowledge financial support from the Spanish
Ministerio de Educación y Ciencia (Project CTQ2005-00795/BQU),
the Comunidad de Madrid (Project S-0505/PPQ/0328-03), and the
Factoria de Cristalización, Consolider-Ingenio 2010.
[18] L.J. Farrugia, J. Appl. Cryst. 32 (1999) 837.