Synthesis, spectroscopy and molecular structures of new salicylketiminato nickel(II) complexes

Article abstract of DOI:10.1016/j.poly.2004.03.018

A series of salicylketimines (2-[(2,6-diisopropylphenylimino)ethyl]phenol, 2-[(2,6-diisopropylphenylimino)ethyl]naphthol and 2-[(2,6- diisopropylphenylimino)(phenyl)-methyl]phenol), and their nickel complexes of general forms [(salicylketiminato)-Ni(PPh₃)(Ph)] and [(salicylketiminato)₂Ni] were synthesized and characterized. The formation of monophenyl-nickel(II) complexes versus the corresponding bis(sal)Ni(II) complexes depends on the fine tuning of the reaction work up and is affected by the substituent at the ketimine. Salicylketimines were thus found to form more readily the bis(sal)Ni(II) complexes than salicylaldimines. The molecular structures of the complexes were determined by X-ray crystallography and in all of them Ni has a nearly ideal square-planar coordination sphere.

Full text of DOI:10.1016/j.poly.2004.03.018

Polyhedron 23 (2004) 1649–1656
www.elsevier.com/locate/poly
Synthesis, spectroscopy and molecular structures of new
salicylketiminato nickel(II) complexes
a
b,
b
a,
*
Mika Kettunen , Adnan S. Abu-Surrah *, Hamzeh M. Abdel-Halim , Timo Repo
,
a
Markku Leskela , Maarit Laine , Ilpo Mutikainen , Markku Ahlgren
a
a
c
€
a
Laboratory of Inorganic Chemistry, Department of Chemistry, University of Helsinki, P.O. Box 55, FIN-00014, Finland
b
Department of Chemistry, Hashemite University, P.O. Box 150459, Zarqa 13115, Jordan
c
Department of Chemistry, University of Joensuu, P.O. Box 111, FIN-80101 Joensuu, Finland
Received 10 February 2004; accepted 29 March 2004
Available online 22 April 2004
Abstract
A series of salicylketimines (2-[(2,6-diisopropylphenylimino)ethyl]phenol, 2-[(2,6-diisopropylphenylimino)ethyl]naphthol and
2-[(2,6-diisopropylphenylimino)(phenyl)-methyl]phenol), and their nickel complexes of general forms [(salicylketiminato)-Ni
(PPh3)(Ph)] and [(salicylketiminato)2Ni] were synthesized and characterized. The formation of monophenyl-nickel(II) complexes
versus the corresponding bis(sal)Ni(II) complexes depends on the fine tuning of the reaction work up and is affected by the sub-
stituent at the ketimine. Salicylketimines were thus found to form more readily the bis(sal)Ni(II) complexes than salicylaldimines.
The molecular structures of the complexes were determined by X-ray crystallography and in all of them Ni has a nearly ideal square-
planar coordination sphere.
Ó 2004 Elsevier Ltd. All rights reserved.
Keywords: Nickel(II) complexes; Schiff bases; Salicylketimine ligands; X-ray crystallography
1. Introduction
Moreover, due to their tolerance towards polar func-
tionalities, these systems are viewed as promising alter-
natives to Ziegler-Natta and metallocene catalysts. By
now, late transition metals as olefin polymerization
catalysts have been extensively reviewed, and possibili-
ties to apply them even in acrylate polymerization have
been demonstrated [4].
The MAO-activated cationic catalysts are, anyhow,
electrophilic and hence sensitive to protic solvents and
polar monomers. For this reason, there has been a
substantial interest in developing new, less oxophilic,
catalysts for olefin polymerization [5]. Shell higher olefin
process (SHOP) offers an intriguing insight for catalytic
activity of neutral nickel catalysts used for ethylene
oligomerization [6] and recently novel salicylaldimine
based Ni(II) complexes as catalysts for homo and co-
polymerization of olefins were described by DuPont [7]
and Grubbs and co-workers [8]. The most active systems
contain either electron-withdrawing nitro substituents
on the aromatic ring or bulky substituents at C-3, a 9-
anthracenyl group being the most effective [activity of
Until middle of 1990s, only few reports were intro-
duced utilizing late transition metal complexes as cata-
lyst precursors for polymerization of a-olefins [1]. This
could be due to the fact that these catalysts generally
exhibited low activities for olefin polyinsertion. In ad-
dition, b-hydride elimination steadily competed with the
chain growth resulting in the formation of oligomers [2].
However, in 1995 new nickel(II)- and palladium(II)-
based catalysts bearing bulky diimine ligands were re-
ported for ethene polymerization, and few years later
also iron(II) was successfully applied as a metal centre
with bis(imino)pyridine ligands [3]. These complexes,
after methylaluminoxane (MAO) activation, produced
high molecular weight polymers with a high activity.
* Corresponding authors. Tel.: +962-5-382-6600x4315; fax: +962-5-
382-6613 (A.S. Abu-Surrah). Tel.: +358-9191-50228; fax: +358-9191-
50198 (T. Repo).
E-mail addresses: asurrah@hu.edu.jo (A.S. Abu-Surrah), timo.
repo@helsinki.fi (T. Repo).
0277-5387/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2004.03.018

1650
M. Kettunen et al. / Polyhedron 23 (2004) 1649–1656
1.3 ꢀ 105 mol ethylene/(mol Ni h)]. It has been reported
that the neutral salicylaldiminato nickel(II) complexes
work as a single component catalysts or require only a
phosphine scavenger such as [Ni(COD)2] (COD: 1,5-
cyclooctadiene) to act as catalysts for homo- and copo-
lymerization of ethylene [8]. However, MAO as activator
surprisingly turned out to be essential to initiate the
homopolymerization of norbornene [9].
g of Na2SO4 at 200 °C in a closed steel autoclave for 24
h. The reaction mixture was then cooled, filtered and the
filtrate was evaporated to dryness. The residue was pu-
rified with column chromatography on silica with 1:5
mixture of diethylether/hexane as eluent. Yield: 46%.
Anal. Calc. for C20H25NO: C, 81.31; H, 8.53; N, 4.74.
Found: C, 81.22; H, 8.54; N, 4.75%. 1H NMR (200
MHz, CDCl3): d ¼ 1.15 (dd, 12H, JHH ¼ 1:8 Hz,
3JHH ¼ 7:0 Hz, CHCH3), 2.19 (s, 3H, N@CCH3), 2.78
Recently, we and other research groups have found
that penta-coordinated iron(II) complexes with triden-
tate ketimine ligands (2,6-bis(imino)pyridyl derivatives)
are an order of magnitude more active, as ethylene po-
lymerization catalysts, than their aldimine analogues
[3,10]. As an augmentation to our studies upon both the
coordination chemistry of heteroatom-containing li-
gands [11,12] and their catalytic application [4f,10a,13],
we now report the synthesis of new nickel(II) complexes
with salicylketimine Schiff base ligands. The new com-
pounds were characterized by methods of elemental
3
(sept, 2H, J ¼ 7:0 Hz, CHMe2), 6.91 (m, 1H, H–Ar),
7.05 (m, 1H, H–Ar), 7.18 (b, 3H, H–Ar), 7.41 (m, 1H,
H–Ar), 7.65 (m, 1H, H–Ar), 14.95 (s, 1H, OH) ppm. 13
C
NMR (50 MHz, CDCl3): d ¼ 17:6, 23.1, 23.6, 28.3,
118.0, 118.3, 119.1, 123.2, 125.1, 128.9, 133.1, 138.0,
142.3, 162.4, 172.1 ppm. IR: m ¼ 1608 cmꢁ1 (C@N).
2.3.2. 2-[(2,6-diisopropylphenylimino)ethyl]naphthol (5)
The compound was prepared and purified as de-
scribed above (Section 2.3.1). Yield: 48%. Anal. Calc. for
C24H27ON: C, 83.44; H, 7.87; N, 4.05. Found: C, 83.39;
H, 7.88; N, 4.03%. 1H NMR (200 MHz, CDCl3):
1
analysis, IR-, MS-, H-, 13C- and 31P-NMR spectros-
copy. Furthermore, the complexes were subjects to X-ray
structure analysis.
3
d ¼ 1:17 (d, 12H, JHH ¼ 7:0 Hz, CHCH3), 2.28 (s, 3H,
3
CCH3), 2.89 (sept, 2H, J ¼ 7:0 Hz, CHMe2), 7.14 (m,
1H, H–Ar), 7.24 (m, 3H, H–Ar), 7.52 (m, 3H, H–Ar),
7.73 (m, 1H, H–Ar), 8.53 (m, 1H, H–Ar), 17.08 (s, 1H,
OH) ppm. 13C NMR (50 MHz, CDCl3): d ¼ 17:2, 22.8,
23.9, 28.5, 110.56, 115.8, 123.5, 124.7, 126.4, 127.2,
129.1, 136.5, 139.1, 140.6, 167.4, 172.3 ppm. IR:
m ¼ 1596 cmꢁ1 (C@N).
2. Experimental
2.1. Materials
All reactions were carried out under argon by using
standard Schlenk techniques. Reagent grade chemicals
were purchased from commercial suppliers and used as
received unless otherwise stated. trans-[(PPh3)2Ni((Ph)Cl]
was prepared according to literature [14]. The hydro-
carbon and ether solvents were purified by distillation
over LiAlH4.
2.3.3. 2-[(2,6-diisopropylphenylimino)(phenyl)methyl]-
phenol (6)
The compound was prepared as described for 4
(Section 2.3.1). The isolated residue was purified with
column chromatography using petroleum ether/ethylac-
etate (8:1) solvent mixture as eluent. Isolated yield: 6%.
Anal. Calc. for C25H27ON: C, 83.99; H, 7.61; N, 3.92.
Found: C, 82.29; H, 7.66 N, 3.86%. 1H NMR (200 MHz,
CDCl3): d ¼ 1:08 (d, 6H, 3JHH ¼ 8:0 Hz, CHCH3), 1.17
(d, 6H, 3JHH ¼ 8:0 Hz, CHCH3), 2.97 (sept, 2H, 3J ¼ 8:0
Hz, CH Me2), 6.81 (m, 1H, H–Ar), 7.03 (m, 2H, H–Ar),
7.16 (b, 5H, H–Ar), 7.30 (m, 3H, H–Ar), 7.43 (m, 1H, H–
Ar), 14.76 (s, 1H, OH). IR: m ¼ 1605 cmꢁ1 (C@N).
MS(EI): 357 (Mþ), 280 (Mþ ) Ph).
2.2. Physical measurements
Elemental analyses were performed at the Depart-
ments of Chemistry of the Universities of Konstanz and
Ulm or at the Department of Pharmacy at University of
Helsinki with an EA 1110 CHNS-O CE instrument. 1H-,
13C- and 31P-NMR spectra were recorded using a Varian
Gemini 200 or a Bruker AMX 400 spectrometer. Infra-
red spectra were measured on a Perkin–Elmer Spectrum
One spectrometer using ATR sampling assessor. Mass
spectra were acquired using a JEOL JMS-SX102 mass
spectrometer (EI) or Bruker ion trap 3000+ MS equip-
ped with Agilent’s AP-MALDI ion source (proto 3).
2.4. Synthesis of complexes
2.4.1. {Phenyl)(triphenylphosphine)(2-[(2,6-diisopropyl-
phenylimino) ethyl]phenoxy)}-nickel(II) (7)
A solution of ligand 4 (0.65 g, 2.2 mmol) in THF
was added to excess amount of NaH (0.18 g, 7.5 mol)
at 0 °C. The mixture was stirred for 1 h at room
temperature, filtered and evaporated. The pale yellow
residue was washed with n-pentane and dried. Yield of
the sodium salt Na-4 was 98%. To a solid mixture of
2.3. Synthesis of ligands
2.3.1. 2-[(2,6-Diisopropylphenylimino)ethyl]phenol (4)
A solution of 2-hydroxyacetophenone (3.2 g, 23.9 mmol),
2,6-diisopropylaniline (4.7 g, 23.9 mmol) and five drops
of HCOOH in methanol were stirred together with ca. 5

M. Kettunen et al. / Polyhedron 23 (2004) 1649–1656
1651
Na-4 (0.30 g, 0.94 mmol) and trans-[(PPh3)2Ni((Ph)Cl]
(0.62 g, 0.90 mmol), 20 ml of benzene was added at
0 °C. The mixture was stirred at room temperature for
6 h and then filtered. After concentrating the filtrate to
ca. 3 ml, the product was precipitated as orange powder
upon addition of n-pentane (30 ml). The solid was
isolated by cannula filtration, then washed with pen-
tane and dried. Isolated yield: 30%. Anal. Calc. for
C44H44NNiOP: C, 76.31; H, 6.40; N, 2.02. Found: C,
2.4.4. Bis[(2-(2,6-diisopropylphenylimino)ethyl)phenoxy]-
nickel(II) (10)
The compound was prepared as described in Section
2.4.3. Crystals suitable for single crystal X-ray analysis
were formed upon recrystallization from benzene/n-
pentane (1:5) solvent mixture. 1H NMR (200 MHz,
C6D6): d ¼ 1:13 (d, 12H, 3JHH ¼ 7:0 Hz, iPr–CH3), 1.73
(m, 18H, iPr–CH3, N@CCH3), 4.08 (sept, 4H,
3JHH ¼ 7:0 Hz, iPr–CH), 5.77 (m, 2H, Ar–H), 6.33 (m,
2H, Ar–H), 6.83–7.25 (m, 10H, Ar–H) ppm. MS(EI):
647 (Mþ), 358 (Mþ ) (N\O)). IR: m ¼ 1602 cmꢁ1
(C@N).
1
76.86; H, 6.41; N, 2.04%. H NMR (200 MHz, C6D6):
3
d ¼ 1:05 (d, 6H, JHH ¼ 6:8 Hz, iPr–CH3), 1.21 (d, 6H,
3JHH ¼ 6:8 Hz, iPr–CH3), 1.83 (s, 3H, N@CCH3), 3.84
3
(sept, 2H, JHH ¼ 6:8 Hz, iPr–CH), 6.29–7.70 (m, 27H,
Ar–H). 31P NMR (200 MHz, C6D6): d ¼ 23.8 ppm. IR:
m ¼ 1598 cmꢁ1 (C@N).
2.4.5. Bis[(2-(2,6-diisopropylphenylimino)ethyl)naphtoxy]-
nickel(II) (11)
A solution of Na-5 (0.52 g, 1.42 mmol) in benzene
(30 ml) was added to a suspension of trans-[(PPh3)2Ni-
((Ph)Cl] (0.88 g, 1.27 mmol) in the same solvent (20 ml).
The reaction took soon a deep red color and was stirred
at room temperature for 6 h, after which it was treated
as in Section 2.4.3. Yield 86%. Anal. Calc. for
C48H52N2O2Ni: C, 77.11; H, 7.01; N, 3.74. Found: C,
2.4.2. {Phenyl)(triphenylphosphine)(2-[(2,6-diisopropyl-
phenylimino)ethyl]naphthoxy)}-nickel(II) (8)
The sodium salt of the ligand (Na-5) and the corre-
sponding complex were prepared following the same
procedure used above (Section 2.4.1). The product was
purified by recrystallization from 1:5 benzene/n-pentane
solvent mixture at )20 °C and collected as orange crys-
tals. Isolated yield: 39%. Anal. Calc. for C48H46NNiOP:
C, 77.63; H, 6.24; N, 1.89. Found: C, 77.64; H, 5.90; N,
1
75.02; H, 6.93; N, 3.65%. H NMR (200 MHz, C6D6):
3
d ¼ 1:13 (d, 12H, JHH ¼ 7:0 Hz, iPr–CH3), 1.39 (d,
3
12H, JHH ¼ 7:0 Hz, iPr–CH3), 1.72 (s, 3H, N@CCH3),
1
3
1.54%. H NMR (200 MHz, C6D6): d ¼ 1:10 (d, 6H,
4.60 (sept, 2H, JHH ¼ 7:0 Hz, iPr–CH), 6.14 (m, 2H,
3
3JHH ¼ 7:0 Hz, iPr–CH3), 1.24 (d, 6H, JHH ¼ 7:0 Hz,
H–Ar), 6.76–7.46 (m, 16H, H–Ar) ppm. MS(AP-
MALDI): 746 (Mþ). IR: m ¼ 1591 cmꢁ1 (C@N).
iPr–CH3), 1.97 (s, 3H, N@CCH3), 3.89 (sept, 2H,
3JHH ¼ 7:0 Hz, iPr–CH), 6.25–7.69 (m, 29H, Ar–H). 13
C
NMR (50 MHz, CDCl3): d ¼ 23.6, 24.7, 25.1, 29.4, 114.2,
116.7, 121.8, 124.0, 124.5, 125.8, 126.4, 127.1, 127.3,
127.8, 128.3, 128.5, 128.7, 130.2, 131.7, 131.9, 132.2,
135.0, 135.1, 137.4, 138.7, 140.8, 147.9, 164.2, 169.5 ppm.
31P NMR (200 MHz, C6D6): d ¼ 24.3 ppm. IR: m ¼
1597 cmꢁ1 (C@N).
2.5. X-ray crystal structure determination for the com-
plexes 7–10
Single crystals of the compounds were selected for the
X-ray measurements and mounted on the glass fibre
using the oil drop method [15a]. Data were collected at
120(2) (7, 10) and 173(2) (8, 9) K using Nonius Kap-
paCCD diffractometer. The intensity data were cor-
rected for Lorentz and polarization [15b] effects and for
absorption by multi-scan method [16]. The structures
were solved by direct methods (SHELXS 97). The re-
finements and graphics were done using SHELXL 97 and
2.4.3. Bis[{2-(2,6-diisopropylphenylimino)(phenyl)meth-
yl}phenoxy]nickel(II) (9)
The sodium salt of the ligand 6 was prepared as de-
scribed above (Section 2.4.1). A solution of Na-6 (0.53 g,
1.40 mmol) in benzene (30 ml) was added to a suspen-
sion of trans-[(PPh3)2Ni((Ph)Cl] (0.88 g, 1.27 mmol) in
the same solvent (20 ml). The reaction took soon a deep
red color and was stirred at room temperature for 6 h
and then filtered. After concentrating the filtrate to ca. 3
ml, the product was precipitated upon addition of n-
pentane (30 ml). The solid was isolated by cannula fil-
tration then washed with n-pentane and dried. The iso-
lated product was crystallized from toluene/n-hexane 1:5
mixture to give orange crystals suitable for X-ray
structure analysis. Isolated yield was 32%. 1H NMR
(200 MHz, C6D6): d ¼ 1.24 (d, 12H, 3JHH ¼ 6:6 Hz, iPr–
SHELXTL/PC program package, respectively. All non-
hydrogen atoms were refined anisotropically. The H
atoms were introduced in calculated positions and re-
fined with fixed geometry with respect to their carrier
atoms. The cell parameters and the specific data col-
lections parameters are summarized in Table 1.
3. Results and discussion
3.1. Ligand and complex synthesis
3
CH3), 2.13 (d, 12H, JHH ¼ 6:6 Hz, iPr–CH3), 3.87
(sept, 4H, 3JHH ¼ 6:6 Hz, iPr–CH), 5.68 (m, 2H, H–Ar),
6.11 (m, 2H, H–Ar), 6.56–7.20 (m, 10H, H–Ar) ppm.
IR: m ¼ 1599 cmꢁ1 (C@N).
The synthesis of the ligands (4–6) and their nickel
complexes (7–11) are shown in Scheme 1. Preparation of
the desired salicylketimines turned out to proceed with

1652
M. Kettunen et al. / Polyhedron 23 (2004) 1649–1656
Table 1
Crystal data and structure refinement for 7–10
7
8
9
10
Formula
Formula weight
T (K)
C
44H44NNiOP
C48H46NNiOP
742.54
173(2)
C50H52N2NiO2
771.65
173(2)
C40H48N2NiO2
647.51
120(2)
692.48
120(2)
triclinic
Crystal system
Space group
Unit cell dimensions
monoclinic
P21=c
monoclinic
P21=c
triclinic
ꢀ
ꢀ
P1
P1
ꢁ
a (A)
11.6450(1)
11.7285(1)
14.1484(2)
99.491(1)
96.400(1)
109.777(1)
1764.13(3)
2
14.1440(11)
13.681(2)
22.128(4)
90.000(11)
114.726(9)
90.000(8)
3889.3(10)
4
10.3310(19)
11.577(3)
19.815(3)
90.000(16)
121.123(15)
90.000(16)
2028.8(8)
2
8.36340(10)
9.9331(2)
11.5502(2)
112.6720(1)
100.1010(10)
99.0720(10)
844.43(2)
1
ꢁ
b (A)
ꢁ
c (A)
a (°)
b (°)
c (°)
3
ꢁ
V (A )
Z
Dcalc (Mg mꢁ3
)
1.304
0.631
1.268
0.577
1.263
0.521
1.273
0.612
Absorption coefficient (mmꢁ1
Crystal dimensions (mm)
h range (°)
)
0.30 ꢀ 0.30 ꢀ 0.10
2.13–27.48
31 239
0.25 ꢀ 0.20 ꢀ 0.15
5.02–27.50
47 797
0.20 ꢀ 0.20 ꢀ 0.06
3.52–27.52
139 71
0.20 ꢀ 0.15 ꢀ 0.05
3.96–27.45
10 310
Number of data collected
Number of unique data
Number of data refined
Number of parameters
Ra½I > 2rðIÞꢂ
8063 ½Rint ¼ 0:0437ꢂ
8063
438
8855 ½Rint ¼ 0:0759ꢂ
8855
469
4622 ½Rint ¼ 0:0775ꢂ
4622
250
3838 ½Rint ¼ 0:0293ꢂ
3838
210
0.0366
0.0789
0.0436
0.0828
0.0533
0.1023
0.0317
0.0710
b
wR2
Residual density (e Aꢁ3
)
0.369 and )0.437
0.328 and )0.397
0.439 and )0.476
0.282 and )0.313
P
P
a R ¼ kFoj ꢁ jFck= jFoj.
P
P
2
2 1=2
b wR2 ¼ ½ ½wðFo2 ꢁ Fc2Þ ꢂ= ½wðFo2Þ ꢂꢂ
.
negligible yields, even with extended refluxing periods.
Therefore, ligands 4, 5 and 6 were prepared in methanol
at 200 °C in a closed steel autoclave in the presence of
Na2SO4 and a catalytic amount of formic acid. After
purification by column chromatography, ligands 4 and 5
were isolated with nearly 50% yields, but with only 6%
yield for ligand 6. After deprotonation of the ligands
with an excess of NaH in THF, the corresponding so-
dium salts were allowed to react with trans-[(PPh3)2-
Ni((Ph)Cl], either by addition of the reaction solvent
(benzene) to a solid mixture of the two reactants at low
temperature or by addition of a solution of the corre-
sponding sodium salt to a suspension of the nickel
precursor. The former method favours the formation of
monophenyl-nickel(II) complexes 7 and 8, while the
latter method leads to the formation of the bis(sal)Ni(II)
complexes 9–11.
1H NMR spectra of the ligands are similar to those of
the corresponding salicylaldimines [8], except for a singlet
(4 and 5) which appears at 2.19–2.28 ppm that can be
attributed to the ketimine methyl group. Upon com-
plexation, this singlet is shifted upfield to 1.83–1.97 ppm.
The septet which is due to CH protons of the isopropyl
groups is shifted down field (from that in the spectra of
ligands 4 and 5 (2.78 and 2.89 ppm)) to 3.84–3.89 ppm as
observed for 7 and 8. In the case of the bis(sal) complexes,
this septet is further shifted to 3.87, 4.08 and 4.60 ppm for
9, 10 and 11, respectively. The signals of the triphenyl-
phosphine ligand in the 31P NMR spectra of complexes 7
and 8 are observed at 23.8–24.3 ppm. The IR spectra of 4,
5 and 6 show bands at 1608, 1596 and 1605 cmꢁ1, re-
spectively, which are ascribed to C@N group. After
complexation, these bands are correspondingly found at
1598 and 1597 cmꢁ1 for the monophenyl complexes (7
and 8) and 1599, 1602 and 1591 cmꢁ1 for the bis(sal)-
Ni(II) complexes (9–11), respectively. The IR spectra of
all the studied complexes are in good agreement with
previous reports of analogous compounds [9].
The reaction of Na-5 with trans-[(PPh3)2Ni((Ph)Cl]
1
was monitored by H NMR. When benzene was added
to a solid mixture of the reacting materials, only the
monophenyl complex 8 was detected. This complex was
purified by recrystallization from 1:5 benzene/n-pentane
solvent mixture at )20 °C which gave orange crystals.
However, when a slight excess of a solution of the so-
dium salt of 5 in benzene was added to a suspension of
nickel precursor at ambient temperature, the bis(sal)-
Ni(II) complex 11 was obtained as a major product and
1
only a trace amount of 8 was observed in H NMR.
Ligand 4 behaved similarly upon complexation, both the
monophenyl complex (7) and the bis(sal)Ni(II) (10)
could be isolated.
In its isolated form complex 8 was found to be quite
stable in solution at room temperature. According to
1H NMR, no decomposition or transformation to the
corresponding bis(sal)–Ni(II) species was detected even
after 8 h room temperature and after 50 h the molar
ratio of 11:8 was found to be 1:15. In the case of the

M. Kettunen et al. / Polyhedron 23 (2004) 1649–1656
1653
N
C
O
C
OH
OH
NH2
R`
+
R’
R’
MeOH
H /
R
R
+
200˚C
R`
(4 - 6)
(1 - 3)
Ph
Ph3P
O
Ni
N
C
1. NaH
R'
R'
(4, 5)
CH3
2. t-(PPh3)2Ni(Ph)Cl
R'
R'
(7 , 8)
R
C
N
O
1. NaH
(4 - 6)
Ni
2. t-(PPh3)2Ni(Ph)Cl
N
C
O
1 , 4 , 7 , 10 : R = CH3 , R` = H
R'
R'
R
2 , 5 , 8 , 11 : R = CH3 and R`, R` = 5,6-benzo
3 , 6 , 9 : R = Ph , R` = H
(9 - 11)
Scheme 1. Synthesis of ligands (4–6) and complexes (7–11).
salicylaldimines, the formation of bis(sal)Ni(II) com-
plexes usually require more harsh reaction conditions
[17]. In order to form the desired bis(sal)Ni(II) complex
[17b], the neutral phenyl substituted salicylaldiminato
Ni(II) complex had to be stirred at 50 °C first with vinyl
chloride (VC) for four days in toluene and then to
continue stirring for another four days in n-hexane at
50 °C. The complexation occurred via tetrahedral Ni
complex bearing a Cl instead of the Ph ligand, where Cl–
Ni bond was formed by 1,2-insertion of VC into Ni–Ph
bond followed by b-Cl elimination.
With the salicylketimine ligands, the formation of the
bis(sal) complexes can take place spontaneously.
Moreover, in the reaction of Na-6 with trans-[(PPh3)2-
Ni((Ph)Cl], the bis(sal)Ni(II) complex (11) was the pre-
dominant product. It seems that the presence of the
phenyl group on the ketimine carbon of the ligand in-
creased the tendency to form a bis(sal) complex. The
reason for this particular behaviour remains unclear but
it could be due to trans influence of the ketimine site,
thus allowing a faster dissociation of the second PPh3
ligand. So, in addition to fine tuning of the reaction
conditions, also different substituents on the ketimine
carbon may affect on the complexation behaviour of
these salicylketimine ligands.
Surprisingly, the monophenyl salicylketiminato based
Ni(II) complexes 7 and 8 turned out to be catalytically
inactive in homopolymerization of ethene or norborn-
ene when [Ni(COD)2] or BF3 were applied as phosphine
scavengers, even at elevated temperatures (up to 60 °C)
and pressures (up to 40 bar).
3.2. Crystal structures of the complexes
For further investigation of structural features of the
complexes, crystals of complexes 7 and 8, suitable for
X-ray structure determination, were grown from 1:5
benzene/n-pentane mixture at )20 °C and crystals of
complexes 9 and 10 were obtained at ambient temper-
ature. The coordination sphere of complex 8 was found
to be similar to that of 7. Also, the coordination
spheres of bis(sal)Ni(II) complexes 9 and 10 were found
to be alike. Data collection and the refinement of data
1
of 7–10 (Figs. 1–4) are summarized in Table 1.
In the solid state, complex 7 has a square-planar ge-
ꢁ
ometry. The Ni atom is approximately 0.01 A out of the
1
The molecular structure of 11 was also determined. It was found
similar to that of 10 and is thus left from discussion here but the data is
included in the supplementary material.

1654
M. Kettunen et al. / Polyhedron 23 (2004) 1649–1656
Fig. 1. ORTEP plot of the molecular structure of compound 7. Dis-
placement ellipsoids are drawn at 50% probability level.
Fig. 3. ORTEP plot of the molecular structure of compound 9. Dis-
placement ellipsoids are drawn at 50% probability level.
Fig. 2. ORTEP plot of the molecular structure of compound 8. Dis-
placement ellipsoids are drawn at 50% probability level.
plane of the donor atoms. The bulky 2,6-diisopropyl-
phenylimine occupies the trans position to the triphe-
nylphosphine ligand with almost a linear N1–Ni–P1
angle (172.17(5)° ) (Table 2). The phenyl group attached
to Ni lies in trans position to O1 with an O1–Ni–C21
angle of 171.73(7)°. The Ni–O1, Ni–N1 and Ni–C21
bond distances in complex 7 are similar to those for
known nickel complexes [18].
Fig. 4. ORTEP plot of the molecular structure of compound 10.
Displacement ellipsoids are drawn at 50% probability level.
Complex 9 forms a square planar complex, at which
nickel lays in the symmetry centre of the molecule and
thus in the plane of the four donor atoms (Table 1,
Fig. 3). The bond angles and distances are similar to
those found for 10 (Table 1, Fig. 4), where the average
ꢁ
The Ni–P1 bond distance (2.185(1) A) is only a bit
longer than those in Grubbs’ nickel-based complex
ꢁ
(2.172(2) A) and in Cavell’s [Ni(PPh3)(o-tolyl)(N–O)]
complexes with N–O bidentate pyridinecarboxylate li-
ꢁ
gands (d(Ni–P) 2.1653(2) A) [18d]. But, it is clearly
shorter than that in nickel(II) salicylaldiminato com-
plexes bearing naphthyl instead of phenyl group cis to
ꢁ
Ni–O distance (1.808 A) is somewhat shorter, and the
Ni–N distance (1.926) is somewhat longer than those in
the bis(salicylaldiminato) complexes which were re-
ꢁ
ported by Jordan and co-workers (Ni–O 1.846 A, Ni–N
ꢁ
PPh3 (2.200(1) and 2.198(2) A) [9].
ꢁ
1.899 A) [17b] and Knoch et al. (1.856, 1.899 A) [17a].
ꢁ

M. Kettunen et al. / Polyhedron 23 (2004) 1649–1656
1655
Table 2
Selected bond lengths (A) and angles (°) for 7–10 (symmetry transformations were used to generate equivalent atoms)
ꢁ
7 (x ¼ 21)
8 (x ¼ 26)
9
10
Bond lengths
Ni–C(x)
Ni–O(1)
1.8957(18)
1.9050(12)
1.9582(15)
2.1845(5)
1.905(2)
1.8890(14)
1.9498(16)
2.1907(7)
1.809(2)
1.933(2)
1.8081(10)
1.9262(11)
Ni–N(1)
Ni–P(1)
Bond angles
C(x)–Ni–O(1)
C(x)–Ni–N(1)
O(1)–Ni–N(1)
O(1)–Ni–P(1)
N(1)–Ni–P(1)
C(x)–Ni–P(1)
O(1A)–Ni–O(1)
O(1)–Ni–N(1A)
N(1A)–Ni–N(1)
171.73(7)
95.96(7)
89.75(6)
84.19(4)
172.17(5)
90.60(5)
167.92(8)
97.00(8)
90.07(6)
87.71(4)
173.27(5)
86.31(6)
92.04(9)
91.88(5)
180.00(13)
87.96(9)
180.000(1)
180.00(10)
88.12(5)
180.00(10)
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4. Conclusions
A method for the synthesis of salicylketimine ligands
was developed by condensation of a ketone with an
amine in methanol at 200 °C in a closed steel-autoclave.
The complexation behaviour of these ligands towards
trans-[(PPh3)2Ni((Ph)Cl] was investigated. Two types of
Ni(II) complexes could be isolated and characterized,
the monophenyl(salicylketimine)Ni(II) complexes and
the corresponding bis(salicylketimine) Ni(II) complexes.
It was found that salicylketimine ligands form readily
the bis(sal)Ni(II) complexes.
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5. Supplementary material
ꢂ
€
(f) P.M. Castro, K. Lappalainen, M. Ahlgren, M. Leskela,
T. Repo, J. Polym. Sci. Part A: Polym. Chem. 41 (2003) 1380;
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Crystallographic data for the structures reported in
this paper have been deposited at the Cambridge Crys-
tallographic Data Centre as supplementary publication
numbers CCDC 230868 (7), CCDC 230869 (8), CCDC
230871 (9), CCDC 230870 (10) and CCDC 230872 (11).
Copies of the data can be obtained on application to the
Director, CCDC, 12 Union Road, Cambridge CB2 1EZ,
UK (fax: +44-1223-336-033; e-mail: deposit@ccdc.cam.
ac.uk or www:http://www.ccdc.cam.ac.uk).
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