Organogold(III) complexes derived from auration reactions of thienyl-substituted pyridine derivatives

Article abstract of DOI:10.1039/a906410i

2-(3-Thienyl)pyridine (3-Hthpy) and 2-(2-thienyl)pyridine (2-Hthpy) reacted with Na[AuCl₄]·2H₂O to afford the adducts [AuCl₃(3-Hthpy)] 1a and [AuCl₃(2-Hthpy)] 1b, respectively. The cycloaurated complex [AuCl₂(3-thpy-C²,N)] [3-thpy = 3-(2-pyridyl)thiophen-2-yl] 2a was obtained by warming 1a at 80°C in an acetonitrile-water (1:5) mixed solvent, whereas the cycloaurated complex [AuCl₂(2-thpy-C³,N)] [2-thpy = 2-(2-pyridyl)thiophen-3-yl] 2b was produced by the reaction of 1b with silver(I) tetrafluoroborate in refluxing dichloromethane. Moreover, when 1b was heated at reflux in dichloromethane in the absence of silver(I) tetrafluoroborate, the thiophene-C(5) metallated species [{Au(μ-Cl)Cl[(2-thpy-C⁵)H]}₂]Cl₂ [2-thpy = 2-(2-pyridyl)thiophen-5-yl] 3b was formed. Thermal degradation of 3b in aqueous acetonitrile yielded 2-(5-chloro-2-thienyl)pyridine and 5,5′-bis(2-pyridyl)-2,2′-bithienyl. X-Ray structural analyses of [AuCl(3-thpy-C¹,N)(PPh₃)]BF₄ 4a and [AuCl(3-thpy-C1,N)(PPh₃)]BF₄ 4b, which were obtained by the reactions of 2a and 2b with triphenylphosphine, have been performed. The Royal Society of Chemistry 1999.

Full text of DOI:10.1039/a906410i

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Organogold(III) complexes derived from auration reactions of
thienyl-substituted pyridine derivatives
Yoshio Fuchita,*a Hidenori Ieda,a Shuichi Wada,a Shingo Kamedab and Masahiro Mikuriyab
a Division of Molecular Chemistry, Graduate School of Science, Kyushu University at
Ropponmatsu, Chuo-ku, Fukuoka 810-8560, Japan. E-mail: fuchita@rc.kyushu-u.ac.jp
b Department of Chemistry, School of Science, Kwansei Gakuin University,
Nishinomiya 662-8501, Japan
Received 6th August 1999, Accepted 20th October 1999
2-(3-Thienyl)pyridine (3-Hthpy) and 2-(2-thienyl)pyridine (2-Hthpy) reacted with Na[AuCl4]ؒ2H2O to afford the
adducts [AuCl3(3-Hthpy)] 1a and [AuCl3(2-Hthpy)] 1b, respectively. The cycloaurated complex [AuCl2(3-thpy-C2,N)]
[3-thpy = 3-(2-pyridyl)thiophen-2-yl] 2a was obtained by warming 1a at 80 ЊC in an acetonitrile–water (1:5) mixed
solvent, whereas the cycloaurated complex [AuCl2(2-thpy-C3,N)] [2-thpy = 2-(2-pyridyl)thiophen-3-yl] 2b was
produced by the reaction of 1b with silver() tetrafluoroborate in refluxing dichloromethane. Moreover, when 1b was
heated at reflux in dichloromethane in the absence of silver() tetrafluoroborate, the thiophene-C(5) metallated
species [{Au(µ-Cl)Cl[(2-thpy-C5)H]}2]Cl2 [2-thpy = 2-(2-pyridyl)thiophen-5-yl] 3b was formed. Thermal degradation
of 3b in aqueous acetonitrile yielded 2-(5-chloro-2-thienyl)pyridine and 5,5Ј-bis(2-pyridyl)-2,2Ј-bithienyl. X-Ray
structural analyses of [AuCl(3-thpy-C1,N)(PPh3)]BF4 4a and [AuCl(3-thpy-C1,N)(PPh3)]BF4 4b, which were obtained
by the reactions of 2a and 2b with triphenylphosphine, have been performed.
Cyclometallation has been receiving much interest in organo-
metallic chemistry from the viewpoint of C–H bond activation
by transition metal compounds.1 Although gold() is iso-
electronic with palladium() and platinum() (d8), its chemistry
of cyclometallation is still only poorly explored.2 Moreover, to
date, cyclometallation with gold() (cycloauration) has been
limited to 2-substituted pyridine derivatives with the condition
that the metallation sites are benzene ring-carbons.2 Con-
cerning metallation sites other than benzene ring-carbons,
metallations at thiophene,3 pyrazole,4 pyrrole,5 pyridine6 and
furan ring-carbons7 have been established in cyclometallation
with RuII, RhIII, IrIII, PdII and PtII species.
We have been studying cycloauration of 2-substituted pyr-
idine derivatives in recent years and have reported the successful
synthesis of new cycloaurated complexes derived from 2-
benzoyl-, 2-anilino-, 2-phenoxy- and 2-(phenylsulfanyl)-
pyridine.8 Developing our research interest in cycloauration
chemistry, we have studied the cycloauration of 2-(3-thienyl)-
Scheme 1 (i) Na[AuCl4]ؒ2H2O; (ii) CH3CN–H2O (1:5); (iii) Na-
and 2-(2-thienyl)-pyridine, both of which are potential ligands
to form a C–N chelate ring composed of thiophene ring-carbon
and pyridine nitrogen atoms. Concerning the reaction of 2-(2-
thienyl)pyridine with gold() compounds, Constable and
Sousa9 reported that isolable products from this reaction were
the addition complex [AuCl3(2-Hthpy)], 2-(5-chloro-2-
thienyl)pyridine and 5,5Ј-bis(2-pyridyl)-2,2Ј-bithienyl. How-
ever, our reinvestigation of the above reaction revealed that
auration at C3 (cycloauration) and C5 of the thienyl group in
2-(2-thienyl)pyridine takes place depending upon the reaction
conditions. Here we describe the above results and the novel
cycloauration reaction of 2-(3-thienyl)pyridine as well.
[AuCl4]ؒ2H2O in CH3CN–H2O (1:5); (iv) PPh3, NaBF4.
Auration of 3-Hthpy and 2-Hthpy and characterization of the
resulting gold(III) complexes
At room temperature 2-(3-thienyl)pyridine (3-Hthpy) and 2-(2-
thienyl)pyridine (2-Hthpy) reacted with an equimolar amount
of Na[AuCl4]ؒ2H2O in an acetonitrile–water (1:1) mixed solv-
ent to give the adducts [AuCl3(3-Hthpy)] 1a and [AuCl3(2-
Hthpy)] 1b, respectively, in nearly quantitative yields. In their
far-IR spectra, adducts 1a and 1b showed only one strong band
each, at 367 and 368 cmϪ1, respectively, attributable to the over-
lapping ν(Au–Cl) frequencies trans to the pyridine-nitrogen
and chloro ligand.10 The absence of the characteristic band
Results and discussion
due to ν(Au–Cl) frequencies of the bond trans to sulfur (around
11
The methods for preparation of the new gold() complexes
derived from 2-(3-thienyl)pyridine (3-Hthpy) and 2-(2-
thienyl)pyridine (2-Hthpy) are shown in Scheme 1 and 2,
respectively. Assignment of the 1H NMR spectra was
performed with the aid of 1H–1H correlation spectroscopy
(COSY) and the data are summarized in Table 1.
310 cmϪ1
)
excludes the possibility of thiophene-sulfur co-
ordination in 1a and 1b.
When 1a was heated at 80 ЊC in an acetonitrile–water (1:5)
mixed solvent, the cycloaurated complex [AuCl2(3-thpy-C2,N)]
[3-thpy = 3-(2-pyridyl)thiophen-2-yl] 2a was isolated in 81%
yield. Complex 1b was also obtained directly from the reaction
J. Chem. Soc., Dalton Trans., 1999, 4431–4435
This journal is © The Royal Society of Chemistry 1999
4431

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Table 1 Proton NMR spectra of the organogold() complexes derived from 3-Hthpy and 2-Hthpya
2-Pyridyl moietyb
Thienyl moietyb
H4 or H5
Complex
H6Ј
Other protons
PPh3
1a [AuCl3(3-Hthpy)]
8.88 (1H, dd)c
7.73 (1H, dt, H5Ј)d
8.20 (1H, dt, H4Ј)e
7.88 (1H, dd, H3Ј)e
7.61 (1H, dd, H4)f
7.69 (1H, dd, H5)g
8.13 (1H, dd, H2)h
7.86 (1H, d)j
—
2a [AuCl2(3-thpy-C2,N)]
2b [AuCl2(2-thpy-C3,N)]
9.25 (1H, dd)d
9.29 (1H, dd)d
7.63 (1H, t, H5Ј)i
8.35 (1H, dt, H4Ј)e
7.62 (1H, dt, H5Ј)e
8.29 (1H, dt, H4Ј)e
7.26 (1H, d, H5Ј)e
8.13 (1H, dd, H3Ј)e
8.01 (1H, dd, H3Ј)e
7.85 (2H, H3Ј, H4Ј)l
8.37 (1H, t, H4Ј or 5Ј
—
7.88 (1H, d)j
7.32 (1H, d)j
—
7.99 (1H, d)j
3b [{Au(µ-Cl)Cl[(2-thpy-C5)H]}2]Cl2 8.50 (1H, d)i
6.96 (1H, d)j
—
7.70 (1H, d)j
4a [AuCl(3-thpy-C1,N)(PPh3)]BF4
4b [AuCl(2-thpy-C3,N)(PPh3)]BF4
9.27 (1H, br)k
8.9 (1H, br)
8.20 (1H, d, H3Ј)i
)
7.55–8.0 (2H)l
7.55–8.00 (15H)l
7.3–7.7 (15H)l
i
7.55–8.0 (1H, H4Ј or 5Ј
)
l
7.85 (1H, br, H4Ј or 5Ј
)
6.57 (1H, d)j
7.3–7.7 (2H, H4Ј or 5, H3Ј)l
7.3–7.7 (1H)l
a Measured in DMSO-d6, except for 1a (CD3CN) at 270 MHz and 23 ЊC; δ in ppm with respect to SiMe4; s = singlet, d = doublet, t = triplet,
4
br = broad, dd = double doublet, dt = double triplet. b For numbering see Scheme 1 and 2. c 3J(HH) = 5.9 Hz, J(HH) = 1.0 Hz. d 3J(HH) = 5.9 Hz,
4J(HH) = 1.5 Hz. e 3J(HH) = 7.8 Hz, 4J(HH) = 1.5 Hz. f 3J(HH) = 5.1 Hz, 4J(HH) = 1.5 Hz. g 3J(HH) = 5.1 Hz, 4J(HH) = 2.9 Hz. h 3J(HH) = 2.9 Hz,
4J(HH) = 1.5 Hz. i 3J(HH) = 7.8 Hz. j 3J(HH) = 5.4 Hz. k Apparent triplet. l Overlapping signals.
ordinated 2-Hthpy or 3-Hthpy ligand readily dissociates in
DMSO. Concerning the cycloauration of complexes 2a and 2b,
1
their H NMR spectra both showed only six aromatic protons
and their far-IR spectra each exhibited two bands characteristic
of ν(Au–Cl) frequencies of bonds trans to a pyridyl nitrogen
atom [366 (2a) and 362 cmϪ1 (2b)] and a thienyl carbon atom
[283 (2a) and 281 cmϪ1 (2b)],10 as expected from the cyclo-
aurated structures. The lower field shifts of δ(H6Ј) resonances
(for the numbering scheme, see Scheme 1) in the spectra of 2a
(δ 9.06) and 2b (δ 9.17) compared with those of the free ligands
[3-Hthpy (δ 8.59) and 2-Hthpy (δ 8.52)] and the adducts [1a
(δ 8.88) and 1b (δ 8.95)10 in CD3CN] are also observed in other
cycloaurated complexes containing pyridine ligands.2 This shift
was ascribed to the proximity of the H6Ј proton to chloride
ligand,12 and can be used as a good indicator of cycloauration.
The two protons in the thiophene ring of 2b appeared as a well-
separated AB pattern at δ 7.32 and 7.99, while those of 2a were
observed at nearly equal chemical shifts, δ 7.86 and 7.88.
The C(5) metallated species 3b showed two bands at 364 and
300 cmϪ1 in its IR spectrum assignable to ν(Au–Cl) frequencies
due to the bonds trans to chloride and carbon, respectively.10
Moreover, bands assignable to ν(NH) and ν(C᎐Nϩ) frequencies
᎐
were observed at 3230 and 1600 cmϪ1 indicating the presence of
1
a pyridinium moiety. The H NMR spectrum of this complex
exhibited six protons in the aromatic region with chemical shifts
quite different from those observed in 2b. The FAB mass
spectrum of 3b gave a parent peak at m/z 893 attributable to
[M Ϫ Cl]ϩ. On the basis of these results and elemental analysis,
Scheme 2 (i) Na[AuCl4]ؒ2H2O; (ii) AgBF4 in dichloromethane; (iii)
3b was tentatively assigned to have the structure shown in
dichloromethane; (iv) CH3CN–H2O (4:3); (v) PPh3, NaBF4.
Scheme 2. However, the conductivity of 3b, measured in acetone
between 3-Hthpy and Na[AuCl4]ؒ2H2O in an acetonitrile–water
(1:5) mixed solvent at 80 ЊC. In contrast, as shown by Con-
stable and Sousa9 under the same reaction conditions adduct 1b
did not afford the cycloaurated complex [AuCl2(2-thpy-C3,N)]
[2-thpy = 2-(2-pyridyl)thiophen-3-yl] 2b and only the starting
material was recovered from the reaction. However, we found
that the 2-(2-thienyl)pyridine ligand in 1b cyclometallated with
gold when 1b was heated at reflux in dichloromethane with
silver() tetrafluoroborate (yield of 2b, 46%). Interestingly, the
above reaction performed in the absence of silver() tetrafluoro-
borate gave another metallation product, [{Au(µ-Cl)Cl[(2-thpy-
C5)H]}2]Cl2 [2-thpy = 2-(2-pyridyl)thiophen-5-yl] 3b, where the
C(5) of the thiophene moiety is metallated.
(ΛM 137 S cm2 molϪ1) and DMSO (68.0 S cm2 molϪ1), showed
lower values than might be expected for a 2:1 electrolyte,13
implying that in solution 3b exists to a considerable degree
as the zwitterionic species [AuϪCl3{(2-thpy-C5)H}ϩ]. Similar
lower molar conductivity (ΛM 85 S cm2 molϪ1 in acetone) has
been observed for [AuCl2(L)ؒHCl] (HL = 1-phenylpyrazole)
formed by the C(4) metallation of 1-phenylpyrazole by
anhydrous AuCl3.14 Such thiophene-C(5) metallated species
have been reported by Constable et al.15 from the reaction
between Na[AuCl4] and 6-(2-thienyl)-2,2Ј-bipyridine. Both our
results and those of Constable indicate that gold() species are
apt to attack upon the most electrophilic C(5) site rather than
C(3) of the thiophene moiety which leads to formation of a
cycloaurated complex. Moreover, it was found that by thermal
degradation of 3b at 84 ЊC in aqueous acetonitrile 2-(5-chloro-
2-thienyl)pyridine (Clthpy) and 5,5Ј-bis(2-pyridyl)-2,2Ј-bithi-
enyl (pttp) were produced in 8 and 18% yields, respectively.
Considering the previous observation by Constable and Sousa,9
1
The H NMR spectrum of the adduct 1b in CD3CN was
identical with that reported,9 but in DMSO-d6 it showed the
same spectrum as that of free 2-Hthpy. Moreover, signals due to
1
free 3-Hthpy were observed in the H NMR spectrum of the
adduct 1a in DMSO-d6. These results indicated that the co-
4432
J. Chem. Soc., Dalton Trans., 1999, 4431–4435

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Table 2 Crystallographic data for complexes 4a and 4b
4aؒCH2Cl2
4b
Formula
M
C28H23AuBCl3F4NPS
826.67
C27H21AuBCl3F4NPS
741.73
T/K
Crystal system
Space group
293(1)
193(1)
Monoclinic
P21/n
Triclinic
¯
P1
a/Å
b/Å
c/Å
α/Њ
10.473(3)
11.501(3)
13.235(4)
99.45(2)
13.585(3)
9.3107(9)
20.572(5)
90
β/Њ
107.93(1)
85.49(2)
1495.6(7)
2
93.65(1)
90
2596.9(9)
4
γ/Њ
U/Å3
Fig. 1 An ORTEP view of [AuCl(3-thpy-C1,N)(PPh3)]BF4ؒCH2Cl2
[3-thpy = 3-(2-pyridyl)thiophen-2-yl] 4aؒCH2Cl2. Hydrogen atoms and
the tetrafluoroborate anion are omitted for clarity.
Z
Crystal dimensions/
mm
0.60 × 0.45 × 0.21
0.60 × 0.42 × 0.13
µ(Mo-Kα)/cmϪ1
No. measured
reflections
No independent
reflections
R
53.44
5636
59.42
4868
5052
4293
0.026
0.031
0.032
0.037
RЈ
Table 3 Selected bond distances (Å) and angles (Њ) with estimated
standard deviations (e.s.d.s) in parentheses for complex 4aؒCH2Cl2
Au–C(1)
Au–Cl
C(1)–C(4)
C(5)–N
C(2)–S
2.022(5)
2.322(1)
1.379(7)
1.361(7)
1.718(6)
1.428(8)
Au–N
Au–P
C(4)–C(5)
C(1)–S
C(2)–C(3)
2.112(4)
2.307(1)
1.454(8)
1.711(5)
1.353(9)
C(3)–C(4)
Fig. 2 An ORTEP view of [AuCl(2-thpy-C3,N)(PPh3)]BF4 [2-thpy = 2-
(2-pyridyl)thiophen-3-yl] 4b. Hydrogen atoms and the tetrafluoro-
borate anion are omitted for clarity.
C(1)–Au–N
N–Au–P
N–Au–Cl
80.0(2)
175.0(1)
92.2(1)
C(1)–Au–P
P–Au–Cl
C(1)–Au–Cl
97.2(1)
90.26(5)
171.5(2)
where Clthpy and pttp were obtained by warming the adduct 1b
at 80 ЊC in aqueous acetonitrile, it is reasonable to regard 3b as
an intermediate for the formation of Clthpy and pttp.
Table 4 Selected bond distances (Å) and angles (Њ) with estimated
standard deviations (e.s.d.s) in parentheses for complex 4b
Synthesis and X-ray structural analysis of [AuCl(3-thpy-C1,N)-
(PPh3)]BF4 and [AuCl(2-thpy-C1,N)(PPh3)]BF4
Au–C(1)
Au–Cl
C(1)–C(4)
C(5)–N
C(3)–S
2.025(8)
2.349(2)
1.36(1)
1.35(1)
1.70(1)
1.42(1)
Au–N
Au–P
C(4)–C(5)
C(4)–S
C(2)–C(3)
2.103(6)
2.304(2)
1.45(1)
1.71(1)
1.36(1)
In the presence of NaBF4, complexes 2a and 2b reacted with an
equimolar amount of PPh3 to give cationic complexes 4a (ΛM
145 S cm2 molϪ1 in acetone) and 4b (ΛM 128 S cm2 molϪ1 in
acetone), respectively. The IR spectra of both complexes exhib-
ited a strong band due to BF4Ϫ at 1055 cmϪ1 and only one band
assignable to the ν(Au–Cl) frequency trans to a phenylene group
at 327 (4a) and 320 cmϪ1 (4b).10 In the 1H NMR spectrum of 4b,
the H4 signal appeared at considerably higher field (δ 6.57)
which is caused by the ring current of the adjacent benzene
ring of the triphenylphosphine ligand co-ordinated cis to the
C–Au bond. On the basis of these data together with elemental
analyses, 4a and 4b were identified as the cationic four-
coordinate complexes [AuCl(3-thpy-C1,N)(PPh3)]BF4 and
[AuCl(2-thpy-C1,N)(PPh3)]BF4, respectively.
The structures of 4a and 4b were established by X-ray diffrac-
tion and ORTEP16 views of the molecules are shown in Fig. 1
and 2. Crystal data are listed in Table 2, and selected bond
distances and angles are presented in Tables 3 and 4. The gold
atom in complex 4a displays square-planar co-ordination with
very slight pyramidal distortion: thus the C, N, Cl and P atoms
are coplanar (mean deviation from the best plane of 0.0044 Å),
with the gold atom lying 0.0769(2) Å below the best plane. On
the other hand, in complex 4b the gold atom displays a dis-
torted square-planar co-ordination, with the Au, C, P and Cl
atoms essentially coplanar [maximum deviation from their best
plane being ϩ0.0474(80) and Ϫ0.0940(3) Å for C and Au,
respectively], whereas the N atom is displaced 0.5191(66) Å out
C(1)–C(2)
C(1)–Au–N
N–Au–P
N–Au–Cl
80.7(3)
168.8(2)
93.0(2)
C(1)–Au–P
P–Au–Cl
C(1)–Au–Cl
93.7(2)
93.98(7)
169.2(2)
of this plane. The dihedral angle between the Au–P–Cl and
Au–C–N planes is 12.77(71)Њ. A similar distortion has been
previously found in [Au(L)Cl] [HL = 6-(α,α-dimethyl)benzyl-
2,2Ј-bipyridine], where the dihedral angle between Au–N–N
and Au–Cl–C is 11.2(6)Њ.2e The Au–C and Au–P bond distances
in 4a and 4b are normal for gold() complexes.2b,d,e,8,10,17,18 The
bite angles of the cycloaurated ligands are 80.0 (4a) and 80.7Њ
(4b), values which are comparable to those in five-membered
auracycles derived from N,N-dimethylbenzylamine [82.2(4)Њ],19
4,4-dimethyl-2-phenyl-1,3-oxazoline [81.7(3)Њ],17 4-butyl-N-
(trimethoxybenzylidene)aniline [81.41(14)Њ]10 and 4,4Ј-dimeth-
ylazobenzene [80.1(2)Њ],20 and smaller than the values found
in six-membered auracycles such as [AuCl(C6H4CH2C5H4N-
C1,N)(PPh3)]BF4 [85.8(4)Њ],8a [AuCl2(C6H4CMe2C5H4N-C1,N)]
[85.7(1)Њ],2e [AuCl2(C6H4COC5H4N-C1,N)] [89.5(3)Њ],8a [Au-
Cl(C6H4NHC5H4N-C1,N)(PPh3)]BF4 [85.2Њ],8b [AuCl2(C6H4-
OC5H4N-C1,N)] [86.6Њ]8b and [AuCl2(C6H4SC5H4N-C1,N)]
[88.3Њ].8b The slightly longer Au–Cl [2.322(1) (2a) and 2.349(2)
Å (2b)] and Au–N bond distances [2.112(4) (2a) and 2.103(6) Å
J. Chem. Soc., Dalton Trans., 1999, 4431–4435
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(2b) ] are caused by the greater trans influences of the carbon
donor and phosphine ligand, respectively.
(1.0 × 10Ϫ3 mol dmϪ3, acetone), 68.0 S cm2 molϪ1 (5.0 × 10Ϫ4
mol dmϪ3, DMSO).
2-(5-Chloro-2-thienyl)pyridine (Clthpy) and 5,5Ј-bis(2-
pyridyl)-2,2Ј-bithienyl (pttp). An acetonitrile–water (4:3) sus-
pension (7 cm3) containing 3b (0.185 g, 0.199 mmol) was heated
at 84 ЊC for 2 d, and the resulting mixture was filtered while hot.
The filtered solution was cooled to ambient temperature and
Experimental
General
The IR spectra were measured on a JASCO FT/IR-420 spec-
trophotometer, and 1H NMR spectra were recorded on a JEOL
JNM-GX-270 spectrometer using tetramethylsilane as an
internal standard. Melting points were determined on a Yanaco
MP-500D micro melting-point apparatus and are uncorrected.
Conductivity measurements were carried out at 25 ЊC on a
Toa Electronics CM-20E conductometer. FAB mass spectra
were recorded on a JEOL-SX102A mass spectrometer. 2-(2-
Thienyl)pyridine was prepared according to the literature.21
Other reagents were obtained commercially and used without
further purification.
1
the precipitated solids were collected. The H NMR spectrum
showed that these solids were composed of two compounds.
These two compounds were identified as Clthpy and pttp by
comparing the 1H NMR spectrum in acetone-d6 (for Clthpy) or
DMSO-d6 (for pttp).9 The yields of Clthpy (8%) and pttp (18%)
were determined using 2-methylpropan-2-ol as an internal
standard.
[AuCl(3-thpy-C2,N)(PPh3)]BF4 4a. Triphenylphosphine
(0.194 g, 0.738 mmol) and then sodium tetrafluoroborate (0.387
g, 3.521 mmol) were added to a dichloromethane solution (30
cm3) of 2a (0.300 g, 0.701 mmol). The resulting solution was
stirred for 1 d and then filtered. The filtrate was evaporated to
dryness under reduced pressure and the residue was extracted
with acetonitrile. The extract was concentrated and diluted with
diethyl ether to yield yellow microcrystals of 4a (0.435 g, 84%);
mp 185 ЊC (decomp.) (Found: C, 43.65; H, 2.9; N, 2.05.
Syntheses
[AuCl3(3-Hthpy)] 1a. An acetonitrile solution (5 cm3) of 3-
Hthpy (0.223 g, 1.38 mmol) was added to a water solution
(5 cm3) of Na[AuCl4]ؒ2H2O (0.501 g, 1.32 mmol), and the
resulting mixture was stirred at room temperature. After 2 h,
the precipitated orange solids were filtered off and washed with
water and diethyl ether to give 1a (0.572 g, 94%); mp 215 ЊC
(decomp.) (Found: C, 23.5; H, 1.6; N, 3.05. C9H7AuCl3NS
requires C, 23.25; H, 1.5; N, 3.0%); νmax/cmϪ1 (KBr) 367
(Au–Cl); ΛM (1.0 × 10Ϫ3 mol dmϪ3, acetone) 1.52 S cm2 molϪ1.
C27H21AuBClF4NPS requires C, 43.7; H, 2.85; N, 1.9%); νmax
/
Ϫ
cmϪ1 (KBr) 1055 (BF4 ), 327 (Au–Cl); ΛM(1.0 × 10Ϫ3 mol dmϪ3,
acetone) 145 S cm2 molϪ1.
[AuCl(2-thpy-C3,N)(PPh3)]BF4 4b. This complex was pre-
pared similarly as described for 4a as yellow microcrystals in
82% yield; mp 187 ЊC (decomp.) (Found: C, 46.25; H, 3.1; N,
1.75. C27H21AuBClF4NPS requires C, 43.7; H, 2.85; N, 1.9%);
[AuCl3(2-Hthpy)] 1b. This complex was obtained in a similar
manner as described for 1a as brick-red microcrystals in 96%
yield and was identified as [AuCl3(2-Hthpy)] on the basis of
comparisons with the reported data.9
Ϫ
νmax/cmϪ1 (KBr) 1055 (BF4 ), 320 (Au–Cl); ΛM (1.0 × 10Ϫ3 mol
dmϪ3, acetone) 128 S cm2 molϪ1.
[AuCl2(3-thpy-C2,N)] 2a. Method (a). An acetonitrile–water
suspension (1:5, 6 cm3) containing the adduct [AuCl3(3-
Hthpy)] 1a (0.100 g, 0.215 mmol) was heated at 80 ЊC for 2 h.
The resulting mixture was filtered off and washed successively
with water and diethyl ether to give orange-brown solids. These
solids were further washed with a dichloromethane–hexane
mixed solvent (5:2, 7 cm3) to afford complex 2a (0.074 g, 81%);
mp 226 ЊC (decomp.) (Found: C, 25.55; H, 1.45; N, 3.3.
C9H6AuCl2NS requires C, 25.25; H, 1.4; N, 3.25%); νmax/cmϪ1
(KBr) 366, 283 (Au–Cl); ΛM (0.5 × 10Ϫ3 mol dmϪ3, DMSO)
1.91 S cm2 molϪ1.
X-Ray crystallography
Suitable crystals of [AuCl(3-thpy-C1,N)(PPh3)]BF4ؒCH2Cl2
4aؒCH2Cl2 and [AuCl(2-thpy-C3,N)(PPh3)]BF4 4b were grown
from dichloromethane–diethyl ether and chloroform–diethyl
ether, respectively. Each crystal was sealed in a glass capillary
and mounted on an Enraf-Nonius CAD4 diffractometer using
graphite-monochromated Mo-Kα radiation. Crystal data and
details of the data collection are given in Table 2. Intensity data
were collected by the ω–2θ scan technique and corrected for
Lorentz-polarization effects and absorption. The structure was
solved by direct methods and the computer program MolEN22
was used for structure solution and refinement. All the non-
hydrogen atoms were treated anisotropically. The hydrogen
atoms were inserted in their calculated positions and fixed
at these positions. The weighing scheme, w = 1/[σ2(|Fo|) ϩ
(0.02|Fo|)2 ϩ 1.0], was employed.
Method (b). An acetonitrile solution (3 cm3) of 3-Hthpy
(0.050 g, 0.309 mmol) was added to a water solution (15 cm3) of
Na[AuCl4]ؒ2H2O (0.102 g, 0.270 mmol), and the resulting
mixture was heated at 80 ЊC for 7 h. After a work-up similar to
that described in method (a), complex 2a was obtained in 83%
yield.
CCDC reference number 186/1704.
[AuCl2(2-thpy-C3,N)] 2b. Silver() tetrafluoroborate (0.132 g,
0.679 mmol) was added to a dichloromethane suspension (150
cm3) of 1b (0.300 g, 0.646 mmol), and then the resulting mixture
was refluxed for 2 h. After filtration, the filtrate was evaporated
to dryness and the residue was washed with acetonitrile to
remove silver salts, giving 2b (0.127 g, 46%); mp 240 ЊC
(decomp.) (Found: C, 25.35; H, 1.4; N, 3.35. C9H6AuCl2NS
requires C, 25.25; H, 1.4; N, 3.25%); νmax/cmϪ1 (KBr) 362, 281
(Au–Cl); ΛM (0.5 × 10Ϫ3 mol dmϪ3, DMSO) 1.97 S cm2 molϪ1.
Acknowledgements
The authors are grateful to Miss Mie Tomonou of Kyushu
University for her help with FAB mass measurement.
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