Three Types of Nickel(II) Complexes Derived from 2-Substituted Benzothiazoline; Formation of a Tetranuclear Complex by a Sterically Induced Orthometallation Reaction

Article abstract of DOI:10.1246/bcsj.77.289

The reaction of 2-(2,4-dichlorophenyl)benzothiazoline with nickel(II) acetate tetrahydrate in ethanol has afforded the monohelical bis[2-(2,4-dichlorophenylmethyleneamino)benzenethiolato]nickel(II) ([Ni(HL ¹)₂] (1)). The X-ray structure of 1 has revealed that ortho-phenyl hydrogen atoms of pendant arms are oriented to the nickel center in a monohelical structure. The low-field resonance for their ortho-protons in the ¹H NMR spectrum indicates that the Ni...H-C interaction is maintained in solution. Heating 1 in toluene gave a square-planar nickel(II) complex with a non-innocent ligand ([Ni(L²)] (2)), and prolonged heating yielded a thiolato-bridged tetranuclear nickel(II) complex ([Ni ₄(L¹)₄] (3)). The tetranuclear complex 3 was formed from activation of the ortho C-H bond, not the C-Cl bond, through sterically controlled Ni...H-C contacts in 1. The molecular structures of 2 and 3 have also been determined by X-ray crystallographic methods.

Full text of DOI:10.1246/bcsj.77.289

Ó 2004 The Chemical Society of Japan
Bull. Chem. Soc. Jpn., 77, 289–294 (2004)
289
Three Types of Nickel(II) Complexes Derived from 2-Substituted
Benzothiazoline; Formation of a Tetranuclear Complex by a Sterically
Induced Orthometallation Reaction
y
ꢀ
Tatsuya Kawamoto and Yoshihiko Kushi
Department of Chemistry, Graduate School of Science, Osaka University,
1-16 Machikaneyama, Toyonaka, Osaka 560-0043
Received June 5, 2003; E-mail: kaw@ch.wani.osaka-u.ac.jp
The reaction of 2-(2,4-dichlorophenyl)benzothiazoline with nickel(II) acetate tetrahydrate in ethanol has afforded
the monohelical bis[2-(2,4-dichlorophenylmethyleneamino)benzenethiolato]nickel(II) ([Ni(HL1)2] (1)). The X-ray struc-
ture of 1 has revealed that ortho-phenyl hydrogen atoms of pendant arms are oriented to the nickel center in a monohelical
structure. The low-field resonance for their ortho-protons in the 1H NMR spectrum indicates that the Ni H–C interaction
ꢁꢁꢁ
is maintained in solution. Heating 1 in toluene gave a square-planar nickel(II) complex with a non-innocent ligand
([Ni(L2)] (2)), and prolonged heating yielded a thiolato-bridged tetranuclear nickel(II) complex ([Ni4(L1)4] (3)). The tet-
ranuclear complex 3 was formed from activation of the ortho C–H bond, not the C–Cl bond, through sterically controlled
Ni H–C contacts in 1. The molecular structures of 2 and 3 have also been determined by X-ray crystallographic methods.
ꢁꢁꢁ
In general, the reactions of 2-substituted benzothiazolines
with metal ions allow the formation of Schiff base complexes
with N,S donor atoms.1–4 The design and synthesis of their
complexes remain a subject of intense activity; changes of
the substituents on the pendant phenyl rings directly influence
the properties and geometry of the metal complexes2,3 and
the observation of cyclometallation, which is undoubtedly
one of the extensively researched areas of organometallic
chemistry.4 The cyclometallation of phenyl-substituted ligands,
termed orthometallation, in particular, is an important area as a
good model for C–H activation. It is well known that palla-
dium(II) complexes readily orthometallate a variety of organic
ligands.5 Several nickel(II) complexes containing orthometal-
lated ligands have also been reported,5–8 but little is known
about orthometallated nickel(II) complexes containing anionic
N–C chelates without the cyclopentadienyl ring as a stabilizing
tion of three types of nickel(II) complexes derived from 2-
(2,4-dichlorophenyl)benzothiazoline, including the formation
of a tetranuclear nickel(II) complex containing anionic N–C
chelate through sterically controlled Ni H–C contacts in the
monohelical nickel(II) complex.
ꢁꢁꢁ
Experimental
General Procedures. All of the synthetic reactions were car-
ried out under an atmosphere of argon or nitrogen using standard
Schlenk techniques. Workup procedures, including column chro-
matography, were performed in air. The reagents were commercial
samples and not purified further.
Infrared spectra were obtained on a Perkin-Elmer 983G Infrared
Spectrophotometer (4000–180 cmꢂ1) using the Nujol mulls, NMR
spectra on a JEOL EX 270 instrument with tetramethylsilane as an
internal standard (ꢀ 0) and UV/vis spectra on a JASCO V-570
spectrophotometer. Cyclic voltammograms were performed in a
three-electrode cell with a glassy carbon disk as the working elec-
trode, platinum wire as a counter electrode, and a Ag/AgCl refer-
ence electrode. They were measured in CH2Cl2 containing 0.1 M
tetra-n-butylammonium tetrafluoroborate. Elemental analyses
were performed at Osaka University.
Synthesis of 2-(2,4-Dichlorophenyl)benzothiazoline. 2-(2,4-
Dichlorophenyl)benzothiazoline was prepared according to a liter-
ature procedure for 2-substituted benzothiazolines.9 2-Aminothio-
phenol (0.36 g, 2.9 mmol) and 2,4-dichlorobenzaldehyde (0.50 g,
2.9 mmol) in ethanol (20 cm3) were refluxed for 30 min. The sol-
vent was removed, the residue washed with n-hexane and the white
solid dried in vacuo. Yield 0.48 g, 60%. Found: C, 55.21; H, 3.29;
N, 5.00%. Calcd for C13H9Cl2NS: C, 55.33; H, 3.21; N, 4.96%. IR
(Nujol) ꢁmax/cmꢂ1 3334 (NH) and 1582 (aromatic C=C). 1H NMR
(270 MHz, CDCl3) ꢀ 7.68 (1H, d, J ¼ 8:2 Hz, aryl CH), 7.38 (1H,
d, J ¼ 2:0 Hz, aryl CH), 7.23 (1H, dd, J ¼ 8:7 and 1.8 Hz, aryl
CH), 7.04 (1H, d, J ¼ 7:6 Hz, aryl CH), 6.97 (1H, td, J ¼ 7:7
and 1.2 Hz, aryl CH), 6.82–6.75 (2H, m, aryl CH), 6.59 (1H, d, J ¼
ligand, except for potentially tridentate N–C–N ligands.7
A
very small number of nickel(II) complexes with anionic N–C
chelates have been prepared by the reactions of nickel(0) com-
plex, [Ni(cod)2], with ortho halo-substituted amines or imines.8
We have reported that a thiolato-bridged tetranuclear palla-
dium(II) complex was formed by orthometallation of the mon-
ohelical palladium(II) complex with 1-naphthyl groups as
pendant arms through a three-center four-electron M H–C in-
ꢁꢁꢁ
teraction, like the conventional hydrogen bond,4 but the forma-
tion of a corresponding nickel(II) complex was not observed.
We have mainly reported on three types of metal complexes
for Group 10 metals: a mononuclear Schiff base complex,2,4
a
mononuclear complex with a non-innocent ligand,2b,4b and a
thiolato-bridged tetranuclear complex.4 However, such three
types of complexes have not been simultaneously isolated so
far. In this paper, we report on the synthesis and characteriza-
y Emeritus professor of Osaka University
Published on the web February 10, 2004; DOI 10.1246/bcsj.77.289

290 Bull. Chem. Soc. Jpn., 77, No. 2 (2004)
Three Types of Nickel(II) Complexes
4:3 Hz, aryl CH), and 4.43 (1H, d, J ¼ 2:6 Hz, NH). 13C NMR
(67.8 MHz, CDCl3) ꢀ 145.59, 138.54, 134.14, 131.90, 129.12,
128.15, 127.38, 126.06, 125.37, 121.77, 121.17, 110.55, and 64.92.
Synthesis of Bis[2-(2,4-dichlorophenylmethyleneamino)ben-
zenethiolato]nickel(II) ([Ni(HL1)2] (1)). To a solution of 2-(2,4-
dichlorophenyl)benzothiazoline (1.00 g, 3.54 mmol) in ethanol (50
cm3) was added nickel(II) acetate tetrahydrate (0.44 g, 1.77 mmol).
The reaction mixture was refluxed for 20 min and then cooled to
room temperature. The dark reddish-brown precipitate was isolated
by filtration and dried in vacuo. Yield 0.94 g, 86%. Single crystals
suitable for an X-ray crystal structure analysis were obtained by the
diethyl ether diffusion of a chloroform solution. Found: C, 50.53;
H, 2.70; N, 4.56%. Calcd for C26H16Cl4N2NiS2: C, 50.28; H,
2.60; N, 4.51%. IR (Nujol) ꢁmax/cmꢂ1 1588 (C=N) and 1578
Found: C, 50.55; H, 2.81; N, 4.56%. Calcd for C26H16Cl4N2NiS2:
C, 50.28; H, 2.60; N, 4.51%. IR (Nujol) ꢁmax/cmꢂ1 1585, 1570,
and 1557 (aromatic C=C). 1H NMR (270 MHz, CDCl3) ꢀ 7.72
(2H, dd, J ¼ 7:6 and 1.0 Hz, aryl CH), 7.50 (2H, d, J ¼ 2:0 Hz,
aryl CH), 7.02–7.23 (8H, m, aryl CH), 6.91 (2H, dd, J ¼ 8:6 and
2.3 Hz, aryl CH), and 6.61 (2H, s, CH–CH). 13C NMR (67.8
MHz, CDCl3) ꢀ 162.40, 160.16, 138.94, 134.63, 134.10, 131.67,
129.34, 128.71, 128.18, 128.06, 123.27, 119.55, and 76.93. UV–
vis (CHCl3) ꢂmax=103 cmꢂ1 [log("/dm3 molꢂ1 cmꢂ1)]: 8.73
(3.43), 10.16 (3.39), 11.90 (4.53), 13.59sh (3.89), 16.86 (3.09),
18.42 (3.07), 21.10 (3.09), 28.25 (3.63), and 31.06 (3.75). CV
(CH2Cl2, 0.1 M [(n-Bu)4N]BF4; E vs Ag/AgCl [V]): E1=2
ꢂ0:09 (ꢀEp/mV = 96) and Epc ¼ ꢂ1:00 (irreversible).
¼
Synthesis of Tetrakis[2-N-(2,4-dichlorobenzylidene-ꢀC2-
1
and 1570 (aromatic C=C). H NMR (270 MHz, CDCl3) ꢀ 10.79
amino-ꢀN)benzenethiolato]tetranickel(II) ([Ni4(L1)4] (3)).
A
(2H, d, J ¼ 8:2 Hz, aryl CH), 8.12 (2H, s, N=CH), 7.41 (2H, s, aryl
CH), 7.40 (2H, dd, J ¼ 8:6 and 1.0 Hz, aryl CH), 7.08 (2H, t, J ¼
7:4 Hz, aryl CH), 6.82 (2H, dd, J ¼ 8:2 and 2.0 Hz, aryl CH), 6.74
(2H, t, J ¼ 7:8 Hz, aryl CH), and 6.39 (2H, d, J ¼ 7:6 Hz, aryl
CH). 13C NMR (67.8 MHz, CDCl3) ꢀ 162.69, 149.65, 146.62,
138.58, 134.95, 132.75, 130.86, 129.55, 129.04, 128.85, 127.92,
122.10, and 116.38. UV–vis (CHCl3) ꢂmax=103 cmꢂ1 [log("/
dm3 molꢂ1 cmꢂ1)]: 19.31sh (3.63), 21.37 (3.69), and 30.03sh
(4.24). CV (CH2Cl2, 0.1 M [(n-Bu)4N]BF4; E vs Ag/AgCl [V]):
Epc ¼ ꢂ0:99 (irreversible).
suspension of 1 (0.324 g, 0.522 mmol) in toluene (20 cm3) was re-
fluxed for 1.5 h and then cooled to room temperature. The yellow-
ish-brown precipitate formed (0.214 g) was filtered off.10 The fil-
trate was purified by chromatography on a silica gel (230–400
mesh) with CH2Cl2 as the eluent. The first dark green band con-
taining 2 and 3 was collected and dried; crystallization from
CHCl3–diethyl ether gave 3 with a diamond shape. While this is
a reproducible synthetic method of 3, the crystallized 3 was quite
insoluble in common solvents. This property and the yield
(<5%) prevented any characterization beyond a crystal structural
determination. The formation of 3 by heating of 2 (0.050 g,
0.081 mmol) in toluene (20 cm3) for 1.5 h was not observed.
X-ray Crystallography. All crystals were mounted on the end
of glass fibers with epoxy. X-ray diffraction data for all complexes
were collected on a Mac Science MXC3 diffractometer equipped
Synthesis of [Bis-2,20-{1,2-bis(2,4-dichlorophenyl)ethylene-
diimine}benzenethiolato]nickel(II) ([Ni(L2)] (2)). A suspension
of 1 (0.156 g, 0.251 mmol) in toluene (20 cm3) was refluxed for 30
min and then cooled to room temperature. After filtration, the sol-
vent was removed on a rotary evaporator. The black crystalline
product was dissolved in CH2Cl2 (20 cm3) and filtered. The filtrate
was purified by chromatography on a silica gel (230–400 mesh)
column. The following products were separated, in order of elu-
tion, with CH2Cl2: the desired complex 2 as a violet band, the start-
ing complex 1 as a reddish-brown band, and a small amount of un-
identified material as a brown band that did not move. Yield 0.068
g, 44%. Single crystals suitable for X-ray crystal structure analysis
were obtained by n-pentane diffusion of a chloroform solution.
ꢁ
with graphite-monochromated Mo Kꢃ (ꢄ ¼ 0:71073 A) radiation
at room temperature; ꢅ–2ꢅ scans were employed. Three standard
reflections, measured after every 100 scans, showed a non-appreci-
able loss in intensity during the data collection process. An empir-
ical absorption correction was made on the basis of -scans. The
solution and refinement procedures were made by applying the
CRYSTAN-GM software package.11 The structures of 1 and 2
were solved by direct methods using SIR 9212 and that of 3 was
Table 1. Crystallographic Data for Complexes 1, 2, and 3
1
2
3
Formula
M
C26H16Cl4N2NiS2
621.06
Triclinic
C26H16Cl4N2NiS2
621.06
Triclinic
C52H28Cl8N4Ni4S4
1355.47
Monoclinic
C2=c
Crystal system
Space group
ꢂ
P1
ꢂ
P1
ꢁ
a/A
10.181(7)
12.98(1)
10.179(8)
107.06(6)
97.83(6)
73.06(6)
1229(2)
2
1.415
2730
2232 (I > 2:0ꢂðIÞ)
0.070
0.087
10.188(4)
15.316(5)
8.291(5)
93.12(4)
102.58(4)
85.34(3)
1258(1)
2
1.383
5405
4767 (I > 2:0ꢂðIÞ)
0.078
0.100
14.651(7)
27.14(1)
13.374(6)
ꢁ
b/A
ꢁ
c/A
ꢃ/ꢃ
ꢆ/ꢃ
ꢇ/ꢃ
113.91(3)
ꢁ 3
V/A
Z
4861(4)
4
2.188
3372
ꢈ/mmꢂ1
No. unique reflections measured
No. reflections in refinement
1822 (I > 2:0ꢂðIÞ)
R
Rw
0.087
0.107
2
2
2
1=2
R ¼ ꢃjjFoj ꢂ jFcjj=ꢃjFoj, Rw ¼ ½ꢃwðjFoj ꢂ jFcjÞ =ꢃwðFoÞ ꢄ , weighting scheme: 1=½ꢂ2ðFoÞ þ 0:01Fo
ꢄ
2
for 1 and 3 and 1=½ꢂ2ðFoÞ þ 0:001Fo ꢄ for 2.

T. Kawamoto et al.
Bull. Chem. Soc. Jpn., 77, No. 2 (2004)
291
solved by PATTY in DIRDIF 92,13 followed by successive cycles
of least-squares refinement and difference Fourier synthesis. All
non-hydrogen atoms were refined anisotropically by full-matrix
least-squares. Hydrogen atoms were calculated with a C–H dis-
plexes were prepared by the oxidative addition of Ni(0) to
the ortho C–X bonds (X = Cl or Br), not activation of the ortho
C–H bond. In contrast, 3 was obtained by the activation of C–H
bonds, not C–Cl bonds. This behavior can be related to a differ-
ence in the reactivity between the Ni(0) and Ni(II) species for
the C–X and C–H bonds. In addition, the nickel(II) complex de-
rived from 2-phenylbenzothiazoline with the unsubstituted
phenyl group did not give the corresponding thiolato-bridged
tetranuclear nickel(II) complex under identical experimental
conditions. This suggests that chlorine-substituted phenyl
pendant arms are necessary to yield the orthometallated prod-
uct.
ꢁ
tance of 0.96 A. The hydrogen atoms of 1 and 2 were refined iso-
tropically, but those of 3 were not refined. Crystallographic data
are listed in Table 1. Crystallographic data have been deposited
at the CCDC, 12 Union Road, Cambridge CB2 1EZ, UK and cop-
ies can be obtained on request, free of charge, by quoting the pub-
lication citation and the deposition numbers 153392–153394.
Results and Discussion
The reaction of Ni(CH3COO)2 4H2O with 2-(2,4-dichloro-
A general view of 1 which defines the atom numbering
scheme is shown in Fig. 1. Selected bond distances and angles
are listed in Table 2. Complex 1 comprises of a slightly distort-
ed square-planar nickel(II) site with cis nitrogen and cis sulfur
atoms (dihedral angle between S–Ni–N planes is 25(3)ꢃ), and
shows a monohelical geometry accompanying the crossing of
pendant arms. The Ni–S and Ni–N bond distances are nor-
mal.2,3 Once the rotation of pendant arms in the complex 1 is
restricted, there is a possibility of three isomers as shown in
Scheme 2. Complex 1 forms an isomer (I), where ortho-phenyl
ꢁ
phenyl)benzothiazoline in ethanol yielded a dark reddish-
brown precipitate of nickel(II) complex ([Ni(HL1)2] (1)). Heat-
ing of 1 in toluene for 30 min gave a square-planar nickel(II)
complex with a non-innocent ligand ([Ni(L2)] (2)) through car-
bon–carbon bond formation, and prolonged heating afforded
the thiolato-bridged tetranuclear nickel(II) complex ([Ni4(L1)4]
(3)) (Scheme 1). Complex 3 was contaminated with 2 even after
column chromatography, and obtained in a low yield only by
crystallization from CHCl3–diethyl ether. It is presumed that
3 is directly derived from 1 because the formation of 3 by heat-
ing of 2 was not observed. Muller et al. have reported the syn-
thesis of [NiX(C–N–N0)], [Ni(C–N–N0)L]þ, and [NiX(C–N)L]
containing anionic N–C chelates by the reactions of [Ni(cod)2]
with ortho halo-substituted amines or imines.8 These com-
S
N
S
N
H
N
Ni
2+
Ni , ∆
H
EtOH
S
Cl
Cl
Cl
Cl
Cl
Cl
Cl
1 (86%)
Fig. 1. Molecular structure of complex 1.
S
N
S
N
Ni
-
-
∆, 30 min
ꢁ
Table 2. Selected Bond Distances (A) and Angles (deg) of
Complexes 1 and 2
1
toluene
*
*
Cl
1
2
Ni1–S1
Ni1–S2
Ni1–N1
Ni1–N2
S1–C1
S2–C21
N1–C2
N1–C7
N2–C14
N2–C22
2.184(5)
2.181(5)
2.130(2)
2.128(2)
1.805(5)
1.824(4)
1.735(6)
1.706(5)
1.356(6)
1.453(7)
1.448(6)
1.361(6)
Cl
Cl
1.928(12)
1.939(12)
1.761(16)
1.765(16)
1.454(18)
1.282(18)
1.299(18)
1.434(18)
2 (44%)
Cl
Cl
N
Ni
S
∆, 1.5 h
S
1
N
Ni
toluene
S1–Ni1–S2
S1–Ni1–N1
S1–Ni1–N2
S2–Ni1–N1
S2–Ni1–N2
N1–Ni1–N2
Dihedral angle between
NiNS planes
94.7(2)
86.3(4)
162.8(4)
162.7(4)
86.0(4)
98.2(5)
25(3)
94.6(1)
89.4(2)
175.5(2)
176.0(2)
89.7(2)
86.2(2)
1(3)
Cl
Cl
2
3 (< 5%)
Scheme 1.

292 Bull. Chem. Soc. Jpn., 77, No. 2 (2004)
Three Types of Nickel(II) Complexes
S
N
S
N
S
S
N
S
N
S
N
Ni
Ni
Ni
N
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
(I)
(II)
Scheme 2.
(III)
Fig. 3. Molecular structure of complex 3. Hydrogen atoms
are omitted for clarity.
Fig. 2. Molecular structure of complex 2.
hydrogen atoms are oriented to the nickel center. In addition,
the Ni(1) H–C(13) and Ni(1) H–C(20) in 1 have short con-
ꢁꢁꢁ
ꢁꢁꢁ
ꢁ
Table 3. Selected Bond Distances (A) and Angles (deg) of
Complex 3
ꢁ
ꢁ
tacts of 2.46(2) A and 2.48(2) A, showing some interactions be-
tween these atoms.3,4,14 The low-field shift of the ortho-phenyl
protons in the 1H NMR spectrum of 1 confirms this interaction
(vide infra).
Ni1–S1
Ni1–S20
Ni1–N1
Ni1–C9
Ni2–S1
Ni2–S2
Ni2–N2
Ni2–C22
S1–C1
2.215(16)
2.207(16)
1.91(5)
S1–Ni1–S20
S1–Ni1–N1
S1–Ni1–C9
S20–Ni1–N1
S20–Ni1–C9
N1–Ni1–C9
S1–Ni2–S2
S1–Ni2–N2
S1–Ni2–C22
S2–Ni2–N2
S2–Ni2–C22
N2–Ni2–C22
95.0(6)
87.5(15)
166.6(17)
176.1(14)
94.1(17)
84.0(22)
95.7(6)
176.2(15)
93.0(16)
87.8(15)
169.1(16)
83.4(21)
A molecular view of 2 with the atomic numbering scheme is
displayed in Fig. 2. The nickel atom is in a square-planar envi-
ronment with a dihedral angle between the S–Ni–N planes of
1.93(6)
2.179(17)
2.235(16)
1.91(5)
1.92(6)
1.77(6)
1.75(6)
1.42(8)
1.45(8)
3.101(9)
3.629(10)
3.745(10)
3.093(9)
ꢃ
ꢁ
1(3) . The Ni–S bond distances (2.130(2) and 2.128(2) A)
ꢁ
and the Ni–N bond distances (1.805(5) and 1.824(4) A) are
shorter than those observed in Ni–thiolato and Ni–imine com-
plexes, such as 1, but are comparable to those reported for nick-
el(II) complexes with non-innocent ligands (Table 2).2b Indeed,
ꢁ
the S–C bond distances of 1.735(6) and 1.706(5) A and the N–C
ꢁ
bond distances of 1.356(6) and 1.361(6) A are strongly indica-
tive of the charge distribution nature of the non-innocent nick-
el(II) complexes.2b,15b Thus, the structure determination unam-
biguously shows that the 2-aminothiophenol moieties result in
a non-innocent ligand. The UV–vis absorption spectrum and
cyclic voltammogram of 2 support this result (vide infra).
Wieghardt et al. have shown that the electronic structures of
analogous species containing a diamagnetic d8 central ion are
best described as singlet diradicals based on structural and
spectroscopic criteria.15 It is thought that the spins in 2 are also
intramolecularly antiferromagnetically coupled, as shown in
the 1H NMR spectrum without any detectable paramagnetic
shifts or line broadening (vide infra).16
S2–C14
N1–C2
N2–C15
Ni1 Ni10
ꢁꢁꢁ
Ni1 Ni2
ꢁꢁꢁ
ꢁꢁꢁ
Ni1 Ni20
Ni2 Ni20
ꢁꢁꢁ
Symmetry operator for primed atoms: ꢂx, y, ꢂ1=2 ꢂ z.
are given in Table 3. This molecular structure has a crystallo-
graphically imposed twofold axis. This structure is very similar
to that of the palladium(II) complex previously studied; also,
the core consists of a Ni4S4 eight-membered ring bridged by
sulfur atoms.4 To our knowledge, 3 is the first nickel(II) com-
plex with orthometallated the C,N,S-tridentate ligand that has
been confirmed by X-ray crystallography. Each nickel atom
is in a slightly distorted square-planar coordination environ-
The brown crystals of 3 were of poor quality; nevertheless, it
was possible to confirm the structural arrangement by X-ray
crystallography. A perspective drawing with the adopted num-
bering scheme is shown in Fig. 3 and selected bond parameters
ꢁ
ment. The Ni–C bond distances of 1.93(6) and 1.92(6) A and
ꢁ
the Ni–N bond distances of 1.91(5) A in the five-membered or-

T. Kawamoto et al.
Bull. Chem. Soc. Jpn., 77, No. 2 (2004)
293
thometallacycle compare with those found in other Ni(II) com-
plexes with anionic N–C chelates.8 The Ni–S distances of
References
a) L. F. Lindoy and S. E. Livingstone, Inorg. Chim. Acta, 1,
365 (1967). b) L. F. Lindoy and S. E. Livingstone, Inorg. Chem., 7,
1149 (1968). c) L. F. Lindoy, D. H. Busch, and V. Goedken, J.
Chem. Soc., Chem. Commun., 1972, 683. d) A. P. Koley, R.
Nirmala, L. S. Prasad, S. Ghosh, and P. T. Manoharan, Inorg.
Chem., 31, 1764 (1992).
1
ꢁ
2.179(17)–2.235(16) A are relatively longer than those of 1
and other related complexes.2,3 Furthermore, the trans influ-
ence of the metalated carbon can be reflected in the lengthening
of the Ni–S distances trans to the carbon atom (2.215(16) and
ꢁ
2.235(16) A) with respect to the Ni–S distances trans to the
ꢁ
imine nitrogen (2.207(16) and 2.179(17) A). A long Ni Ni sep-
ꢁꢁꢁ
2
a) T. Kawamoto, H. Kuma, and Y. Kushi, Chem. Commun.,
ꢁ
aration (3.09–3.75 A) suggests that there is no Ni–Ni interac-
1996, 2121. b) T. Kawamoto, H. Kuma, and Y. Kushi, Bull. Chem.
Soc. Jpn., 70, 1599 (1997). c) T. Kawamoto and T. Konno, Bull.
Chem. Soc. Jpn., 76, 127 (2003).
tion.
In the 1H NMR spectrum of complex 1, the azomethine pro-
tons appear as one singlet at 8.12 ppm. In addition, the 2-imi-
nothiophenolato protons appear as two doublets and two triplets
and the pendant arms exhibit two doublets and one singlet.
These results indicate the C2 symmetrical structure of 1 in
CDCl3. The most striking feature is the extremely low-field
shift (10.79 ppm) of the pendant ortho-phenyl protons. This
low-field resonance can be attributed to the three-center four-
3
E. Bouwman, R. K. Henderson, A. K. Powell, J. Reedijk,
W. J. J. Smeets, A. L. Spek, N. Veldman, and S. Wocadlo, J. Chem.
Soc., Dalton Trans., 1998, 3495.
4
a) T. Kawamoto, I. Nagasawa, H. Kuma, and Y. Kushi,
Inorg. Chem., 35, 2427 (1996). b) T. Kawamoto, I. Nagasawa,
H. Kuma, and Y. Kushi, Inorg. Chim. Acta, 265, 163 (1997).
5
a) J. Dehand and M. Pfeffer, Coord. Chem. Rev., 18, 327
(1976). b) M. I. Bruce, Angew. Chem., Int. Ed. Engl., 16, 73
(1977). c) E. C. Constable, Polyhedron, 3, 1037 (1984). d) G. R.
Newkome, W. E. Puckett, V. K. Gupta, and G. E. Kiefer, Chem.
Rev., 86, 451 (1986). e) I. Omae, Coord. Chem. Rev., 83, 137
(1988). f) A. D. Ryabov, Chem. Rev., 90, 403 (1990).
6 a) J. P. Kleiman and M. Dubeck, J. Am. Chem. Soc., 85,
1544 (1963). b) I. V. Barinov, T. I. Voyevodskaya, and Yu. A.
Ustynyuk, J. Organomet. Chem., 30, C28 (1971). c) G. K.
electron Ni H–C interaction, which suggests that the isomer
ꢁꢁꢁ
(I) in Scheme 2 for 1 is also predominant in solution. The
1H NMR spectrum of 2 gives one sharp singlet due to the pro-
tons of the asymmetric carbon atoms, which were generated by
carbon–carbon bond formation, at 6.61 ppm. The UV–vis ab-
sorption spectrum of 1 is dominated by two large charge trans-
fer transitions at ca. 20 ꢅ 103 cmꢂ1, which obscure the d–d
transition. In contrast to 1, the spectrum of 2 reveals a very
strong absorption band at ca. 12 ꢅ 103 cmꢂ1, which is the char-
acteristic absorption for metal complexes with non-innocent li-
gands.2b,15 The cyclic voltammograms of 1 and 2 display irre-
versible reduction waves at ꢂ0:99 and ꢂ1:00 V, respectively,
´
Anderson, R. J. Cross, K. W. Muir, and L. Manojlovic-Muir, J.
Organomet. Chem., 362, 225 (1989). d) J. Campora, E. Carmona,
´
´
E. Gutierrez, P. Palma, M. L. Poveda, and C. Ruiz, Organometal-
lics, 11, 11 (1992). e) G. Muller, D. Panyella, M. Rocamora, J.
´
Sales, M. Font-Bardıa, and X. Solans, J. Chem. Soc., Dalton
which are expected to be a metal-centered reduction (NiII
!
´
´
Trans., 1993, 2959. f) M. Font-Bardıa, J. Gonzalez-Platas, G.
Muller, D. Panyella, M. Rocamora, and X. Solans, J. Chem.
Soc., Dalton Trans., 1994, 3075. g) J. J. Schneider, D.
Spickermann, D. Blaser, R. Boese, P. Rademacher, T. Labahn, J.
Magull, C. Janiak, N. Seidel, and K. Jacob, Eur. J. Inorg. Chem.,
NiI).2b The most significant feature in the cyclic voltammetric
studies is that 2 exhibits one reversible redox wave at E1=2
¼
ꢂ0:09 V. This process is a ligand-centered one-electron redox
change, which is a characteristic feature for non-innocent li-
gands.2b,15 The corresponding redox wave was not observed
for 1 without a non-innocent ligand. Thus, these features of 1
and 2 were consistent with the proposed structures, which were
confirmed by the X-ray analysis of single crystals. Complexes 1
and 2, which have the same chemical compositions, can be cor-
related in a valence isomerism.
´
2001, 1371. h) J. Campora, J. A. Lopez, C. Maya, P. Palma, E.
Carmona, and P. Valerga, J. Organomet. Chem., 643–644, 331
(2002).
7
a) D. M. Grove, G. van Koten, P. Mul, R. Zoet, J. G. M. van
der Linden, J. Legters, J. E. J. Schmitz, N. W. Murrall, and A. J.
Welch, Inorg. Chem., 27, 2466 (1988). b) J. A. M. van Beek, G.
van Koten, M. J. Ramp, N. C. Coenjaarts, D. M. Grove, K.
Goubitz, M. C. Zoutberg, C. H. Stam, W. J. J. Smeets, and A. L.
Spek, Inorg. Chem., 30, 3059 (1991). c) A. W. Kleij, H. Kleijn,
J. T. B. H. Jastrzebski, A. L. Spek, and G. van Koten, Organome-
tallics, 18, 277 (1999).
In conclusion, by using 2-(2,4-dichlorophenyl)benzothiazo-
line as a starting material, three types of nickel(II) complexes
were completed. The monohelical nickel(II) complex 1 is first
isolated by the reaction of nickel(II) acetate tetrahydrate with 2-
(2,4-dichlorophenyl)benzothiazoline. X-ray and 1H NMR stud-
ies of 1 indicate that the ortho-phenyl hydrogen atoms lie over
´
a) R. M. Ceder, J. Granell, G. Muller, M. Font-Bardıa, and
X. Solans, Organometallics, 14, 5544 (1995). b) R. M. Ceder, J.
8
the nickel center, and that the Ni H–C interaction is main-
ꢁꢁꢁ
´
Granell, G. Muller, M. Font-Bardıa, and X. Solans, Organometal-
tained even in solution. The heating of 1 gives a square-planar
nickel(II) complex with a non-innocent ligand 2. Furthermore,
a prolonged heating of 1 leads to orthometallation by activation
of the ortho C–H bond, not the C–Cl bond, of the pendant arm
to give the thiolato-bridged tetranuclear nickel(II) complex 3.
This behavior is in contrast to the formation of five-membered
nickelocycles through the oxidation addition of the ortho C–X
bonds (X = Cl or Br) by the reaction of Ni(0) species with ortho
halo-substituted ligands. It can be assumed from these results
lics, 15, 4618 (1996). c) R. M. Ceder, J. Granell, and G. Muller, J.
Chem. Soc., Dalton Trans., 1998, 1047. d) R. M. Ceder, G. Muller,
´
M. Ordinas, M. A. Maestro, J. Mahıa, M. F. Bardia, and X. Solans,
J. Chem. Soc., Dalton Trans., 2001, 977.
9 P. J. Palmer, R. B. Trigg, and J. V. Warrington, J. Med.
Chem., 14, 248 (1971).
10 All attempts to isolate a pure main product (yellow brown
precipitate) via repeated recrystallization failed.
11 CRYSTAN-GM, A Computer Program for the Solution and
Refinement of Crystal Structures for X-ray Diffraction Data, MAC
Science Corporation, Yokohama, 1994.
that the sterically induced Ni H–C contacts allow the forma-
tion of 3 by activation of the ortho C–H bond.
ꢁꢁꢁ

294 Bull. Chem. Soc. Jpn., 77, No. 2 (2004)
Three Types of Nickel(II) Complexes
Weyhermuller, and K. Wieghardt, J. Am. Chem. Soc., 123, 2213
(2001). b) D. Herebian, E. Bothe, E. Bill, T. Weyhermuller, and
¨
K. Wieghardt, J. Am. Chem. Soc., 123, 10012 (2001). c) X. Sun,
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¨
13 DIRDIF 92: ‘‘Technical Report,’’ Crystallography Labora-
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14 L. Brammer, J. M. Charnock, P. L. Goggin, R. J.
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H. Chun, K. Hildenbrand, E. Bothe, T. Weyhermuller, F. Neese,
¨
and K. Wieghardt, Inorg. Chem., 41, 4295 (2002).
16 In agreement with this interpretation solid of 2 at room
temperature was ESR silent.
15 a) P. Chaudhuri, C. N. Verani, E. Bill, E. Bothe, T.