Synthesis and properties of nickel(II) complexes containing trimethylphosphine and thiophenolato-ligands

Article abstract of DOI:10.1002/zaac.200700205

The reaction of thiophenols with [NiMe₂(PMe₃) ₃] yields thiophenolato nickel(II) complexes trans-[Ni(SAr) ₂(PMe₃)₂] (Ar = phenyl (1), 2-methylphenyl (2) and 4-methoxyphenyl (3)) with tetrac

Full text of DOI:10.1002/zaac.200700205

DOI: 10.1002/zaac.200700205
Synthesis and Properties of Nickel(II) Complexes Containing
Trimethylphosphine and Thiophenolato-Ligands
Ruixia Cao, Xiaoyan Li, and Hongjian Sun*
Jinan / P.R. of China, Shandong University, School of Chemistry and Chemical Engineering
Received April 16th, 2007.
Dedicated to Professor Dieter Fenske on the Occasion of his 65th Birthday
Abstract. The reaction of thiophenols with [NiMe2(PMe3)3] yields
thiophenolato nickel(II) complexes trans-[Ni(SAr)2(PMe3)2]
(Ar ϭ phenyl (1), 2-methylphenyl (2) and 4-methoxyphenyl (3))
with tetracoordinated nickel atoms. The molecular structures of 1
and 2 were determined by X-ray crystallography. The three comple-
xes show trans square planar arrangement of the donor atoms. The
mechanism of formation is proposed and discussed. In addition
the intermediate methyl thiophenolato nickel(II) complex,
[Ni(SAr)(PMe3)2Me] (Ar ϭ phenyl) (4) was isolated in the case
of thiophenol.
Keywords: Nickel; Thiophenol; Trimethylphosphine; Crystal
structure
Introduction
plexes are involved in fundamental catalytic (e.g. hydrode-
sulfurization [6]) and biological (e.g. iron-sulfur proteins
[7]) process.
Although thiophenols have been widely employed as the
sources of ligands for various transition metals [1], the tran-
sition-metal-catalyzed reactions using them as substrates
have been scarcely developed. This is partly due to the wide-
spread belief that organic sulfur compounds often bind
strongly to the catalysts, thus poisoning them and making
catalytic reactions ineffective [2]. However metal thiolato
complexes are different from organic thiophenols, they are
known as ubiquitous biological electron-transfer mediators
[3, 4], yet complexes containing thiophenolato ligands have
received relatively little attention and only a few reports
have been found in this area [5]. Metal thiophenolate com-
In 1998, Klein and co-workers reported the syntheses and
structures of molecular diphenolato nickel compounds con-
taining trimethylphosphine ligands [8]. [Ni(PMe3)4] reacts
with phenols under one mole oxygen to yield the products,
but they are stable for air and show no activity for small
molecules (Eq. (1)). According to the HSAB rule the thio-
phenolato nickel complexes are more active than the phe-
nolato nickel complexes because S-donor is much softer
than O-donor.
In this paper a simple and virtual method of synthesis
of thiophenolato nickel complexes is described which
smoothly affords crystalline bis(trimethylphosphine)nickel
thiolate, using dimethylbis(trimethylphosphine)nickel and
thiophenol as the starting materials. Finally three nickel di-
thiolates 1Ϫ3 and one nickel methyl monothiophenolate
complexe were obtained.
* Dr. Hongjian Sun
School of Chemistry and Chemical Engineering
Shandong University
Shanda Nanlu 27
250100 Jinan / P.R. of China
Fax: ϩ86-531-88564464.
E-mail: hjsun@sdu.edu.cn
Results and Discussion
Synthesis of Nickel Complexes 1, 2 and 3
Supporting information for this article is available on the
WWW under http://www.wiley-vch.de/home/zaac or from the
author
The reaction of [NiMe2(PMe3)3] with two molar equivalents
of substituted thiophenols in diethyl ether gave rise to
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R. Cao, X. Li, H. Sun
1)
Table 1 Crystallographic data of compounds 1 and 2
1
2
Formula
C18H28NiP2
429.17
0.22ϫ0.33ϫ0.52
monoclinic
P21/c
6.4030(13)
19.144(4)
8.645(2)
105.27(3)
1022.3(4)
2
1.394
1.307
100(2)
2.13- 27.10
Ϫ8ՅhՅ7
Ϫ24ՅkՅ24
Ϫ11ՅlՅ11
7415
2228 [R(int) ϭ 0.0298]
162
C20H32NiP2S2
457.23
0.28ϫ0.21ϫ0.12
monoclinic
P21/c
6.4590(13)
19.407(4)
9.389(2)
102.47(3)
1149.1(4)
2
1.321
1.167
150(2)
3.06 -27.06
Ϫ8ՅhՅ7
Ϫ24ՅkՅ24
Ϫ11ՅlՅ9
5779
2356 [R(int) ϭ 0.1043]
174
Formula weight
Crystal size /mm
Crystal system
Space group
˚
a /A
˚
b /A
˚
c /A
β /°
V /A3
Z
D calc /(g/cm3)
µ (MoKͰ) /mmϪ1
Temperature /K
data coll. range /°
h
Fig. 1 Molecular structure of 1.
k
l
˚
Selected bond distances /A and angels /°: Ni1-P1 2.2199(7), Ni1-S1
2.2138(5), S1-C1 1.7611(16), S1-Ni1-P1 93.23(2), C1-S1-Ni1 106.52(5),
C2-C1-S1 123.38(12)
No. reflect. measured
No. unique reflect.
No. parameters refined
R1 [F Ն2σ(F)]
R2 [FՆ2σ(F)]
0.0306
0.0870
0.0498
0.1515
1) Crystallgraphic data have been deposited with the Cambridge Crystallo-
graphic Data Centre, CCDC 645479 (1), CCDC 645480 (2).
methylphosphine ligands is recorded as a singlet at
1.04Ϫ1.25 ppm. In the 13C NMR spectrum of complex 2,
trimethylphosphine is registered at 13.3 ppm as a dublet
2
with the coupling constant J(PC) ϭ 30.2 Hz. All of the
spectroscopic data are in accordance with molecular con-
figurations with a square planar coordination of nickel in
low-spin state [8].
The molecular structures of the complexes 1 and 2 were
confirmed by X-ray diffraction analysis (Fig. 1 and Fig. 2).
The nickel atom displays a square-planar coordination
with two P-donor atoms lying in trans-positions. The
Fig. 2 Molecular structure of 2.
˚
Selected bond distances /A and angels /°: Ni1-P1 2.2141(8), Ni1-S1
˚
Ni(1)-P(1) bond lengths fall in the range 2.212Ϫ2.220(9) A
2.2116(7), S1-C1 1.765(3), S1-Ni1-P1 93.49(3), C1-S1-Ni1 106.18(9),
C6-C1-S1 121.8(2)
˚
(average 2.215 A), and Ni(1)-S(1) bond lengths are
˚
˚
2.214Ϫ2.229 A. (average 2.218 A). The angles of P(1)-
Ni(1)-S(1) and C(1)-S(1)-Ni(1), respectively, are in the range
92.17Ϫ93.49°, 102.15Ϫ106.52°. These structural features
are in accordance with phenolatonickel compounds [9].
Also the bond lengths are normal for transition metal thiol-
ates [10]. In both complexes 1 and 2 the phenyl rings of the
thiophenlato ligands are almost perpendicular to the square
coordination plane.
[Ni(SAr)2(PMe3)2] (Ar ϭ phenyl (1), 2-methylphenyl (2),
4-methoxyphenyl (3)) according to Eq. (2).
Crystallization at 4 °C afforded dark red crystals in
58Ϫ60 % yield, respectively. Complexes 1-3 are stable in the
air for several hours, but rapidly decompose at room tem-
perature in solution. The proton resonance of the tri-
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Nickel(II) Complexes Containing Trimethylphosphine and Thiophenolato-Ligands
The reaction of nickel(II) complex 1 with phenyl
acetylene and carbon monoxide
(1) To a solution of nickel(II) complex 1 in diethyl ether
phenyl acetylene was injected at Ϫ80 °C, it was thought to
proceed via alkyne insertion in to the Ni-S bonds according
to the reported reaction mechanism [11, 12]. No reaction
could be observed.
(2) A solution of complex 1 in ether was stirred in CO
atmosphere at room temperature to give white crystals. In
the IR spectrum the terminal coordinated (Ni-CO) bands
was found at 1999 and 1939 cmϪ1. With the comparison to
the previous literature it could be determined that this is
the tetrahedral nickel complex [Ni(CO)2(PMe3)2] [13]. The
separation of the possible S-S coupling species was unsuc-
cessful.
Scheme 1 The possible reaction mechanism
The possible reaction mechanism has been proposed in
Scheme 1. In the first step, substituted thiophenols react
with [NiMe2(PMe3)3] by evolution of methane and elimin-
ation of one trimethylphosphine molecule yielding an inter-
mediate with a tetracoordinated nickel(II) atom. The inter-
mediate can react with another thiophenol molecule
through oxidative addition generating an unstable species
with hexacoordinated nickel(IV) atom, which gives rise to
the end product (1 and 2) by reductive elimination of meth-
ane as by-product.
In order to verify the mechanism stoichiometric reaction
was carried out. Adding thiophenol to a solution of
[NiMe2(PMe3)3] in diethyl ether in 1:1 ratio, the complex 4
with tetracoordinate nickel(II) atom, [NiMe(SPh)(PMe3)2],
could be isolated according to Eq. (3).
Experimental Section
General procedures and materials
Standard vacuum techniques were used in manipulations of volatile
and air sensitive material. Infrared spectra (4000Ϫ400 cmϪ1), as
obtained from Nujol mulls between KBr disks, were recorded on
a Nicolet 5700. 1H, 13C, and 31P NMR (300, 75, and 121 MHz,
respectively) spectra were recorded on a Bruker Avance 300 spec-
trometer. Elemental analyses were carried out on an Elementar
Vario EL III. Melting point and decomposition temperature were
obtained from sealed capillaries and are uncorrected. Literature
procedures were followed in the preparation of phenylethyne [14]
and dimethyltris(trimethylphosphine)nickel [15]. Other chemicals
were used by purchased.
Crystallization at 4 °C generated orange-red crystals in
63 % yield. Complex 4 in the crystal state was easily efflor-
escent and rapidly decomposed in solution at room tem-
perature in the air. The two trans-trimethylphosphine mol-
1. trans-Di(thiophenolato)bis(trimethylphosphine)-
nickel(II) (1)
An ether solution (10 mL) containing thiophenol (0.75 g,
6.80 mmol) was added to a stirred solution of [NiMe2(PMe3)3]
(1.08 g, 3.40 mmol) in diethyl ether (50 mL) at Ϫ80 °C. The reac-
tion mixture was allowed to warm to ambient temperature and
stirred for 18 h. During this period the wine-red mixture turned
dark red. A slight turbidity was filtered off, red crystals (0.88 g) of
1 were obtained from the filtrate at 4 °C. Yield: 60.2 %, m. p.:
1
ecules in H NMR spectrum are recorded at 0.81 ppm as a
singlet, while the signal of Ni-CH3 can be found at
Ϫ0.50 ppm. The resonance of the trimethylphosphine mol-
ecules in the 13C NMR spectrum is registered at 13.2 ppm
2
as a doublet with the coupling constant J(PC) ϭ 23.4 Hz.
The resonance of the (Ni-CH3) is registered at Ϫ10.5 ppm.
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R. Cao, X. Li, H. Sun
125 °C. Anal. Calcd for C18H28NiP2S2 (429.17 g/mol): C, 50.35; H,
6.53. Found: C, 50.23; H, 6.48 %.
This solution was allowed to warm to 20 °C and stirred for 18 h.
After work-up the starting materials could be ioslated.
1H NMR (300 MHz, CDCl3, 294 K, ppm):
δ 1.25 (s, 18H, PCH3);
δ 6.97Ϫ7.29 (m, 10H, CHarom). 31P NMR (121 MHz, CDCl3, 295 K, ppm):
δ Ϫ17.50 (s, PCH3).
6. Reaction of nickel(II) complex 1 with carbon
monoxide
2. trans-Di(2-methylthiophenolato)bis(trimethyl-
phosphine)nickel(II) (2)
A
solution of trans-di(thiophenolato)bis(trimethylphosphine)-
nickel(II) 1 in diethyl ether was stirred in the presence of CO at
room temperature. After 48 h a lot of white powder formed, which
was filtered. Recrystallization afforded white crystals which is
dicarbonylbis(trimethylphosphine)nickel(0) identified by IR (Nu-
To the solution of NiMe2(PMe3)3 (1.08 g, 3.40 mmol) in 50 mL of
diethyl ether was added 2-methylthiophenol (0.884 g, 6.80 mmol)
at Ϫ80 °C, a dark red suspension formed rapidly. After stirring at
room temperature for 16 h the reaction solution was filtrated, then
the red solid residue was extracted with THF (50 mL). Crystalliza-
tion at 4 °C afforded dark red crystals suitable for X-ray diffraction
analysis. Yield: 0.92 g of 2 (59.0 %), m. p.: 135 °C. Anal. Calcd for
C20H32NiP2S2 (457.23 g/mol): C, 52.52; H, 7.00. Found: C, 52.49;
H, 7.12 %.
1H NMR (300 MHz, CDCl3, 294 K, ppm): δ 1.08 (s, 18H, PCH3); δ 2.35 (s,
6H, C-CH3), δ 6.80Ϫ8.47 (m, 8H, CHarom). 13C NMR (75 MHz, CDCl3,
297 K, ppm): δ 13.29 (t, 2J(PC) ϭ 30.2 Hz, PCH3); δ, 22.32 (s, NiϪCH3); δ
146.9; 137.7; 133.7; 128.8; 125.4; 122.4 (s, Carom). 31P NMR (121 MHz,
CDCl3, 295 K, ppm): δ Ϫ16.68 (s, PCH3).
jol): ν ϭ 1999, 1939 (Ni-CO) cmϪ1
.
Conclusion
Dithiophenolatobis(trimethylphosphane)nickel complexes
(1-3) can be prepared in high yields starting from the thio-
phenols and [NiMe2(PMe3)3]. The possible reaction mecha-
nism has been proposed, and the intermediate was success-
fully isolated through controlling the quantity of the thio-
phenols.
3. trans-Di(2-methoxythiophenolato)bis(trimethyl-
phosphine)nickel((II) (3)
Acknowledgment. We gratefully acknowledge support by NSFC
No. 20572062 and the Doctoral Program of Ministry of Education
of China (MOE) Nos. 20050422010 and 20050422011 as well as
Shandong Scientific Plan 032090105, Natural Science Foundation
of Shandong (Y2006B18) and cordially thank Prof. Dr. Dieter
Fenske (Technische Universität Karlsruhe, Germany) for the crys-
tal structure determinations.
A solution of 4-methoxythiophenol (0.954 g, 6.8 mmol) in 10 mL
of diethyl ether was combined with a solution of NiMe2(PMe3)3
(1.08 g, 3.40 mmol) in diethyl ether (50 mL) at Ϫ80 °C. This mix-
ture was allowed to warm to 20 °C and stirred for 18 h to form a
dark red solution, which was filtered. Then the red solid residue
was extracted with THF (50 mL). Crystallization from ether and
THF at 4 °C yielded dark red crystals. Yield: 0.9 g of 3 (58.7 %),
m. p.: 130 °C. Anal. Calcd for C20H32NiO2P2S2 (489.23 g/mol): C,
49.08; H, 6.54. Found: C, 49.16; H, 6.67 %.
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295 K, ppm): δ Ϫ18.58 (s, PCH3).
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A diethyl ether solution (10 mL) containing thiophenol (0.375 g,
3.40 mmol) was added to a stirred solution of NiMe2(PMe3)3
(1.2 g, 3.40 mmol) in diethyl ether (50 mL) at Ϫ80 °C. The reaction
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Found: C, 46.33; H, 7.68 %.
1H NMR (300 MHz, CDCl3, 294 K, ppm): δ 0.807 (s, 18H, PCH3); δ Ϫ0.50
(s, 3H, Ni-CH3), δ 6.65Ϫ7.96 (m, 5H, CHarom).13C NMR (75 MHz, CDCl3,
297 K, ppm): δ 13.17 (d, 2J(PC) ϭ 23.4 Hz, PCH3); δ Ϫ10.45 (s, NiϪCH3);
δ 152.2 (s, S-C); δ 132.4; 138.6; 120.9 (s, Carom); 31P NMR (121 MHz, CDCl3,
295 K, ppm): δ Ϫ13.80 (s, PCH3).
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Nickel(II) Complexes Containing Trimethylphosphine and Thiophenolato-Ligands
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