Cycloauration of 2-substituted pyridine derivatives. Synthesis, structure and reactivity of six-membered cycloaurated complexes of 2-anilino-, 2-phenoxy- and 2-(phenylsulfanyl)-pyridine

Article abstract of DOI:10.1039/a807108j

At room temperature and in ethanol 2-anilinopyridine reacted with H[AuCl₄]·4H₂O as well as Na[AuCl₄]·2H₂O to give directly the six-membered cycloaurated complex [AuCl₂(pap-C¹, N)] 1a [pap = 2-(2-pyridylamino)phenyl], whereas 2-phenoxypyridine (Hpop) and 2-(phenylsulfanyl)pyridine (Hptp) produced only the salts [H₂pop][AuCl₄] 2b and [H₂ptp][AuCl₄] 2c, respectively. The adducts [AuCl₃(Hpop)] 3b and [AuCl₃(Hptp)] 3c have separately been prepared by the reactions of Na[AuCl₄]·2H₂O with Hpop and Hptp, respectively, in an acetonitrile-water mixed solvent. The salts 2b and 2c can be converted into the corresponding adducts 3b and 3c when they are stirred in acetonitrile-water at room temperature. The cycloaurated complexes [AuCl₂(pop-C¹, N)] [pop = 2-(2-pyridyloxy)-phenyl] 1b and [AuCl₂(ptp-C¹, N)] [ptp = 2-(2-pyridylsulfanyl)phenyl] 1c have been obtained by heating the salts or the adducts in acetonitrile-water. Moreover, complexes 1b and 1c have been synthesized directly by the reaction of H[AuCl₄]·4H₂O with Hpop and Hptp in refiuxing acetonitrile-water, ethanol-water and propan-2-ol-water. The reaction of 1a with an equimolar amount of PPh₃ in the presence of NaBF₄ gave the cationic complex [AuCl-(pap-C¹, N)(PPh₃)]BF₄ 5a, while two equivalents of PPh₃ or PEt₃ afforded [AuCl(pap-C¹)(PPh₃)₂]Cl 6a or [AuCl-(pap-C¹)(PEt₃)₂]Cl 7a where the pap ligand co-ordinates through only the carbon atom. On the other hand, the C-N chelates in 1b and 1c are easily cleaved with one equimolar amount of PPh₃ to give [AuCl₂(pop-C¹)(PPh₃)] 8b and [AuCl₂(ptp-C¹)(PPh₃)] 8c, respectively. The boat-form structures of the three six-membered auracycles have been confirmed by X-ray diffraction studies of 1b, 1c and 5a. The crystal structure of 7a has also been determined.

Full text of DOI:10.1039/a807108j

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Cycloauration of 2-substituted pyridine derivatives. Synthesis,
structure and reactivity of six-membered cycloaurated complexes
of 2-anilino-, 2-phenoxy- and 2-(phenylsulfanyl)-pyridine
Yoshio Fuchita,*a Hidenori Ieda,a Arata Kayama,a Junko Kinoshita-Nagaoka,b
Hiroyuki Kawano,b Shingo Kamedac and Masahiro Mikuriyac
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 Applied Chemistry, Faculty of Engineering, Nagasaki University,
Bunkyo-machi, Nagasaki 852-8521, Japan
c Department of Chemistry, School of Science, Kwansei Gakuin University,
Nishinomiya 662-8501, Japan
Received 11th September 1998, Accepted 19th October 1998
At room temperature and in ethanol 2-anilinopyridine reacted with H[AuCl4]ؒ4H2O as well as Na[AuCl4]ؒ2H2O to
give directly the six-membered cycloaurated complex [AuCl2(pap-C1, N)] 1a [pap = 2-(2-pyridylamino)phenyl],
whereas 2-phenoxypyridine (Hpop) and 2-(phenylsulfanyl)pyridine (Hptp) produced only the salts [H2pop][AuCl4]
2b and [H2ptp][AuCl4] 2c, respectively. The adducts [AuCl3(Hpop)] 3b and [AuCl3(Hptp)] 3c have separately been
prepared by the reactions of Na[AuCl4]ؒ2H2O with Hpop and Hptp, respectively, in an acetonitrile–water mixed
solvent. The salts 2b and 2c can be converted into the corresponding adducts 3b and 3c when they are stirred in
acetonitrile–water at room temperature. The cycloaurated complexes [AuCl2(pop-C1, N)] [pop = 2-(2-pyridyloxy)-
phenyl] 1b and [AuCl2(ptp-C1, N)] [ptp = 2-(2-pyridylsulfanyl)phenyl] 1c have been obtained by heating the salts
or the adducts in acetonitrile–water. Moreover, complexes 1b and 1c have been synthesized directly by the reaction
of H[AuCl4]ؒ4H2O with Hpop and Hptp in refluxing acetonitrile–water, ethanol–water and propan-2-ol–water.
The reaction of 1a with an equimolar amount of PPh3 in the presence of NaBF4 gave the cationic complex [AuCl-
(pap-C1, N)(PPh3)]BF4 5a, while two equivalents of PPh3 or PEt3 afforded [AuCl(pap-C1)(PPh3)2]Cl 6a or [AuCl-
(pap-C1)(PEt3)2]Cl 7a where the pap ligand co-ordinates through only the carbon atom. On the other hand, the C–N
chelates in 1b and 1c are easily cleaved with one equimolar amount of PPh3 to give [AuCl2(pop-C1)(PPh3)] 8b and
[AuCl2(ptp-C1)(PPh3)] 8c, respectively. The boat-form structures of the three six-membered auracycles have been
confirmed by X-ray diffraction studies of 1b, 1c and 5a. The crystal structure of 7a has also been determined.
Cyclometallation is an elegant method used to activate C–H
bonds in heterosubstituted molecules.1 However, cycloauration
is generally hard to achieve and until now examples have been
in principle limited to 2-substituted pyridine derivatives,
i.e. 2-phenylpyridine,2 2,9-diphenyl-1,10-phenanthroline,3 4-(4-
methoxyphenyl)-6-phenyl-2,2Ј-bipyridine,4 2-benzylpyridine,5,6
6-benzyl-2,2Ј-bipyridine derivatives7 and 6-tert-butyl-2,2Ј-
bipyridine.7 With other ligands such as azobenzene,8
complexes derived from 2-anilino- (Hpap), 2-phenoxy- (Hpop)
and 2-(phenylsulfanyl)-pyridine (Hptp) is shown in Scheme 1.
1
Assignment of the H NMR spectra was performed with the
aid of 1H–1H correlation spectroscopy (COSY) and the data are
summarized in Table 1.
Reactions of the 2-substituted pyridines, Hpap, Hpop and Hptp,
with [AuCl4]؊, resulting in the formation of salts, adducts and
six-membered cycloaurated complexes
N,N-dimethylbenzylamine,9,10
4,4-dimethyl-2-phenyl-1,3-ox-
azoline,10 1-(dimethyl- or methyl-aminomethyl)naphthalene,10
1,3-bis(dimethylaminomethyl)benzene10 and 4-butyl-N-(3,4,5-
trimethoxybenzylidene)aniline,11 stable cycloaurated com-
plexes have been synthesized by transmetallation from the
corresponding organomercury() compounds.
2-Anilinopyridine reacted at room temperature in ethanol with
an equimolar amount of H[AuCl4]ؒ4H2O or Na[AuCl4]ؒ2H2O
to give directly the six-membered cycloaurated complex
[AuCl2(pap-C1, N)] 1a [pap = 2-(2-pyridylamino)phenyl] in 27
or 62% yield, respectively. It should be noted that the cycloaur-
ation proceeds under very mild conditions at room temperature,
while Nonoyama et al.12 reported previously that 1a was
obtained only when an aqueous mixture containing equimolar
amounts of Hpap and Na[AuCl4]ؒ2H2O was heated under
reflux. It was found that the yields of 1a depend upon the molar
ratio between Hpap and [AuCl4]Ϫ, and the highest yields, 88 and
93%, were obtained when the ratio was 3:1 for H[AuCl4]ؒ4H2O
and 2:1 for Na[AuCl4]ؒ2H2O, respectively. These facts indicated
that an excess of Hpap accelerates the cycloauration probably
by trapping hydrogen chloride generated during the course of
the reaction.
We have been challenging the development of new cycloaur-
ations in recent years and have succeeded in the cycloauration
of 2-benzoylpyridine.6 As an extension of this work, we wish to
report here the cycloauration of 2-anilino-, 2-phenoxy- and
2-(phenylsulfanyl)-pyridine by tetrachloroaurate ion and the
X-ray crystallographic analysis of the resulting six-membered
cycloaurated complexes. While the present work concerning the
cycloauration of 2-anilinopyridine was nearly established,
Nonoyama et al.12 reported isolation of the cycloaurated com-
plexes [AuCl2(C–N)] derived from 2-anilino-, 2-(4-toluidino)-
and 2-(N-methylanilino)-pyridine.
On the contrary, in ethanol 2-phenoxypyridine and 2-
(phenylsulfanyl)pyridine did not cyclometallate by H[AuCl4]ؒ
4H2O at room temperature and even at refluxing temperature,
Results and discussion
The method of preparation of the six-membered cycloaurated
J. Chem. Soc., Dalton Trans., 1998, 4095–4100
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complexes containing pyridine ligands2,5–7 and usually observed
when a chlorine is in the proximity of the pyridine ring.13
E
N
(iii)
(ii)
E=NH a; O b; S c
Reactivity of the cycloaurated complexes 1a, 1b and 1c towards
triphenylphosphine
E
(iv)
N
Cl
Cl
Complex 1a reacted with an equimolar amount of PPh3 in the
presence of NaBF4 to give a cationic complex 5a (ΛM 169 S cm2
molϪ1 in acetone). The IR spectrum exhibited a strong band
AuCl4
HN
2b, 2c
Au
PhE
Cl
(i)
3b, 3c
Ϫ
due to BF4 at 1060 cmϪ1 and only one band at 313 cmϪ1
(iv)
(iv)
3'
6'
3
assignable to the ν(Au–Cl) frequency trans to the phenylene
group.11 Moreover, in the 1H NMR spectrum the H6Ј proton in
the pyridine moiety resonated at δ 8.79 which is essentially the
same chemical shift as that of 1a (δ 8.82), indicating that the six-
membered pap–Au ring remains unchanged. On the basis of
these data and elemental analysis 5a was assigned as a cationic
four-co-ordinate complex [AuCl(pap-C1, N)(PPh3)]BF4. The
similar complex [AuCl(pap-C1, N){P(C6H4CH3-4)3}]Cl has
been prepared by Nonoyama et al.12 On the other hand, when a
two-fold excess of PPh3 was treated with 1a another cationic
complex [AuCl(pap-C1)(PPh3)2]Cl 6a (ΛM 123 S cm2 molϪ1 in
MeOH) was obtained. A v(Au–Cl) band at 295 cmϪ1 in the far-
IR spectrum was characteristic of a frequency trans to carbon,
supporting the presence of a Au–C bond. The H6Ј proton res-
onance observed significantly upfield (δ 8.20) compared to
δ 8.82 for 1a and δ 8.79 for 5a confirmed that the second incom-
ing PPh3 cleaved the C–N chelate by dissociating the pyridine–
nitrogen co-ordination. Such an upfield shift of δ(H6Ј) caused
by C–N bond cleavage was also observed for cycloaurated
complexes of 2-benzoylpyridine.6 A triethylphosphine analogue
[AuCl(pap-C1)(PEt3)2]Cl 7a was also prepared for the X-ray
diffraction study (see below).
E
4
5
4'
N
5'
6
Au
Cl
Cl
1a, 1b, 1c
(v)
(vii)
(vi)
L
Ph3P
Cl
Cl
N
Au
Au
Cl
Cl
BF4
HN
Au
L
Cl
PPh3
NH
E
C5H4N
C5H4N
8b, 8c
6a L=PPh3
7a L=PEt3
5a
Scheme 1 (i) H[AuCl4]ؒ4H2O or Na[AuCl4]ؒ2H2O; (ii) H[AuCl4]ؒ4H2O
in ethanol; (iii) Na[AuCl4]ؒ2H2O in CH3CN–water (1:5); (iv) CH3CN–
water (1:5); (v) PPh3, NaBF4; (vi) 2PPh3 or 2PEt3; (vii) PPh3.
only producing the tetrachloroaurate salts, [H2pop][AuCl4] 2b
and [H2ptp][AuCl4] 2c, respectively. Interestingly, in an
acetonitrile–water (1:5) mixed solvent the same reaction
carried out at room temperature afforded the adducts
[AuCl3(Hpop)] 3b and [AuCl3(Hptp)] 3c. It was also found that
the salts could be converted into the corresponding adducts
almost quantitatively at room temperature in acetonitrile–water
(1:5). Although Nonoyama et al.12 demonstrated that both
2-(p-tolyloxy)- and 2-(p-tolylsulfanyl)-pyridine do not cyclo-
metallate, novel six-membered cycloaurated complexes
[AuCl2(pop-C1, N)] 1b [pop = 2-(2-pyridyloxy)phenyl] and
[AuCl2(ptp-C1, N)] 1c [ptp = 2-(2-pyridylsulfanyl)phenyl] could
be obtained in about 70 and 20% yields respectively by heating
the salts or the adducts at 105 ЊC in acetonitrile–water (1:5). It
seems reasonable that the cycloauration from the salts proceeds
via the formation of the adducts. Moreover, it was also found
that cycloaurations of Hpop and Hptp by H[AuCl4]ؒ4H2O
occur in refluxing alcohol (ethanol or propan-2-ol) in the
presence of water. In addition to this fact, the result that the
salts and the adducts did not produce the cycloaurated com-
plexes by refluxing in water-free acetonitrile clearly showed the
necessity of water for the cycloauration of Hpop and Hptp.
However, the role of water is not clear at the moment. It is also
noted that a yellow complex 4c was always obtained in the
course of the isolating procedures for 1c. The yield of 4c was
about two thirds by weight of that of 1c. However, in spite
In contrast to the C–N chelate in complex 1a, those in the
cycloaurated complexes 1b and 1c were easily cleaved by only
one equimolar amount of PPh3 giving neutral complexes
[AuCl2(pop-C1)(PPh3)] 8b (ΛM 1.4 S cm2 molϪ1 in acetone) and
[AuCl2(ptp-C1)(PPh3)] 8c (ΛM 7.3 S cm2 molϪ1 in acetone),
respectively. Two v(Au–Cl) frequencies of 8b [301 and 325 cmϪ1
]
and 8c [301 and 316 cmϪ1] lacked the characteristic bands due
to chlorine trans to pyridine nitrogen.11 The H6Ј protons of 8b
and 8c appeared significantly upfield δ 7.99 and 8.30, respect-
ively, compared with those for 1b (δ 9.06) and for 1c (δ 9.17).
Such different reactivity towards PPh3 of the three cycloaurated
complexes 1a, 1b and 1c is probably associated with the stability
of the Au–N bonds judging from the basicity of the nitrogen
donors in the pyridyl moiety [pKa values:14 2-MeNHC5H4N
(7.30), 2-MeOC5H4N (3.55) and 2-MeSC5H4N (4.36)].
Crystal structures of complexes 1b, 1c, 5a and 7a
The structures of complexes 1b, 1c, 5a and 7a were established
by X-ray diffraction and ORTEP15 views of the molecules are
shown in Figs. 1–4. Selected bond distances and angles are
summarized in Tables 2–5. In complexes 1b, 1c and 5a the gold
atoms have essentially square-planar AuCNCl2 and AuCNClP
co-ordination with the mean deviation from the best planes of
0.017, 0.017, 0.019 Å, respectively, whereas in 7a the gold atom
displays a square-planar AuCClP2 co-ordination with a very
slight pyramidal distortion with deviations from the best
plane of Ϫ0.089, ϩ0.033 and ϩ0.038 Å at Au, Cl(1) and C(1),
respectively. The Au–C, Au–N, Au–Cl and Au–P bond dis-
tances are very similar to those reported for other gold()
complexes.3,5,7,10,11,16
In complexes of 1b, 1c and 5a the pop–Au, ptp–Au and pap–
Au six-membered auracycles have boat conformations, with
atoms N, C(1), C(6) and C(8) essentially coplanar [mean devi-
ations from their best planes of 0.012, 0.020 0.009 Å, respect-
ively]. These best planes form dihedral angles with planes
C(6)–O–C(7) and N–Au–C(1) of 47.2 and 34.8Њ for 1b, with
planes C(6)–S–C(7) and N–Au–C(1) of 42.5 and 43.4Њ for 1c
1
of the simple H NMR and far-IR spectra (see Experimental
section), the structure could not be assigned.
The far-IR spectra of the cycloaurated complexes 1a, 1b and
1c showed two bands characteristic of v(Au–Cl) frequencies
trans to pyridyl nitrogen atom [356 (1a),12 361 (1b) and 360 (1c)]
and phenylene carbon atom [284 (1a),12 303 (1b) and 295 (1c)].11
1
Each H NMR spectrum of 1a, 1b and 1c exhibited only eight
well separated aromatic protons due to the cycloaurated
moiety, and a significant feature of all is the lower field shifts of
δ(H6Ј) (numbering scheme in Scheme 1) compared with those of
the ‘free’ ligands [Hpap (δ 8.14), Hpop (8.15) and Hptp (8.40)],
the salts (2b and 2c) and the adducts (3b and 3c). Such lower
field shifts of δ(H6Ј) have been reported for other cycloaurated
4096
J. Chem. Soc., Dalton Trans., 1998, 4095–4100

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Table 1 Proton NMR spectral data of the gold() complexesa
2-Substituted pyridine ligandb
Complex
H6Ј
Other protons
Phosphine
1a [AuCl2(pap-C1, N)]
8.82 (1 H, d)c
7.02 (1 H, t, H5)d
7.40 (1 H, d, H3Ј)d
10.69 (1 H, s, NH)
7.23 (1 H, t, H5)d
7.69 (1 H, t, H5Ј)e
7.25 (2 H, m, H4, H5)
7.78 (1 H, dt, H5Ј)g,h
7.02 (1 H, d, H3Ј)e
7.4 (2 H, m, Ph)
7.1 (2 H, m, H3, H5Ј)
7.56 (1 H, d, H6)d
7.26 (1 H, t, H4)d
7.97 (1 H, t, H4Ј)d
—
1b [AuCl2(pop-C1, N)]
1c [AuCl2(ptp-C1, N)]
2b [H2pop][AuCl4]
2c [H2ptp][AuCl4]
3b [AuCl3(Hpop)]
3c [AuCl3(Hptp)]
9.06 (1 H, d)c
9.17 (1 H, d)f
8.15 (1 H, d)i
8.41 (1 H, d)i
7.35 (2 H, m, H3, H4)
7.86 (1 H, d, H3Ј)e
7.45 (1 H, d, H3)
7.59 (1 H, d, H6)e
8.43 (1 H, t, H4Ј)e
7.58 (1 H, d, H6)c
—
—
8.25 (2 H, m, H3Ј, H4Ј)g
7.15 (3 H, m, Ph)
7.85 (1 H, t, H4Ј)e
7.16 (1 H, dt, H5Ј)h,i
7.66 (1 H, dt, H4Ј)e,h
7.1 (3 H, m, Ph)
7.21 (1 H, dt, H5Ј)e,h
7.5 (3 H, m, Ph)
—
6.95 (1 H, d, H3Ј)e
7.6 (2 H, m, Ph)d
—
8.15 (1 H, dd)h,i 7.02 (1 H, d, H3Ј)d
7.4 (2 H, m, Ph)
7.21 (1 H, dt, H5Ј)d,h
7.5 (3 H, m, Ph)
—
7.86 (1 H, dt, H4Ј)d,h
7.19 (1 H, dt, H5Ј)d,h
7.66 (1 H, dt, H4Ј)d,h
6.71 (1 H, d, H3)e
7.19 (1 H, t, H5Ј)e
10.55 (1 H, s, NH)
6.68 (1 H, d, H3)e
7.12 (1 H, d, H6)e
10.13 (1 H, s, NH)
6.92 (1 H, t, H5)e
7.36 (1 H, d, H6)e
9.13 (1 H, s, NH)
6.63 (1 H, t, H5)d
7.06 (1 H, t, H5Ј)d
8.42 (1 H, dd)h,i 6.97 (1 H, d, H3Ј)d
7.6 (2 H, m, Ph)
—
5a [AuCl(pap-C1, N)(PPh3)]- 8.79 (1 H, d)c
BF4
6.22 (1 H, t, H4)e
7.12 (1 H, d, H6)e
7.99 (1 H, t, H4Ј)e
6.12 (1 H, t, H4)e
6.95 (1 H, t, H5Ј)d
7.76 (1 H, t, H4Ј)d
6.99 (1 H, t, H5)e
7.46 (1 H, d, H3Ј)e
7.5–7.85 (15 H, m)
6a [AuCl(pap-C1)(PPh3)2]Cl
7a [AuCl(pap-C1)(PEt3)2]Cl
8b [AuCl2(pop-C1)(PPh3)]
8c [AuCl2(ptp-C1)(PPh3)]
8.20 (1 H, br)
6.86 (1 H, t, H5)e
7.31 (1 H, d, H3Ј)d
7.45–7.55 (30 H, m)
7.4–7.7 (15 H, m)
8.08 (1 H, dd)h,i 6.85 (1 H, t, H5Ј)d
7.23 (1 H, t, H4)e
7.06 (1 H, d, H3Ј)d
7.48 (1 H, d, H3)e
7.65 (1 H, d, H4Ј)d
7.99 (1 H, d)i
6.57 (1 H, dd, H3)d,h
6.90 (1 H, t, H4)d
7.81 (1 H, t, H4Ј)d
6.82 (1 H, d, H3Ј)d
7.17 (1 H, d, H6)d
8.30 (1 H, dd)h,j 6.9 (2 H, m, H5, H3Ј)
7.17 (1 H, d, H6)e
6.99 (1 H, dt, H4)e,h
7.45–7.65 (1 H, H4Ј)j
7.1 (2 H, m, H3, H5Ј) 7.45–7.65 (15 H, m)j
a Measured in DMSO-d6 at 270 MHz and at 23 ЊC; δ in ppm with respect to SiMe4; s = singlet, d = doublet, t = triplet, br = broad, m = multiplet.
b For numbering see Scheme 1. c 3J(HH) = 6.4 Hz. d 3J(HH) = 7.5 Hz. e 3J(HH) = 7.8 Hz. f 3J(HH) = 5.9 Hz. g 3J(HH) = 6.8 Hz. h 4J(HH) = 1.0 Hz.
i 3J(HH) = 4.9 Hz. j Overlapping signals.
Fig. 3 An ORTEP view of complex [AuCl(pap-C1, N)(PPh3)]BF4 5a.
Fig. 1 An ORTEP view of complex [AuCl2(pop-C1, N)] 1b. Hydrogen
Hydrogen atoms and tetrafluoroborate anion are omitted for clarity.
atoms are omitted for clarity.
Fig. 2 An ORTEP view of complex [AuCl2(ptp-C1, N)] 1c. Hydrogen
atoms are omitted for clarity.
and with planes C(6)–N(2)–C(7) and N(1)–Au–C(1) of 35.9
and 43.2Њ for 5a. The dihedral angles between benzene and
pyridine rings are 130.0 (1b), 118.8 (1c) and 133.1Њ (5a). The
bite angles of the cycloaurated ligands are 86.6 (1b), 88.3 (1c)
and 85.2Њ (5a), whose values are wider than those in five-
Fig. 4 An ORTEP view of complex [AuCl(pap-C1)(PEt3)2]Cl 7a.
Hydrogen atoms and chloride anion are omitted for clarity.
J. Chem. Soc., Dalton Trans., 1998, 4095–4100
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Table 2 Selected bond distances (Å) and angles (Њ) with estimated
standard deviations (e.s.d.s) in parentheses for complex 1b
Experimental
General
Au–C(1)
Au–Cl(1)
C(1)–C(6)
C(7)–O
2.03(2)
2.275(4)
1.37(2)
1.41(2)
Au–N
2.02(1)
2.369(5)
1.41(2)
1.35(2)
The IR spectra were measured on a JASCO FT/IR-420 spectro-
photometer, 1H NMR spectra 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. 2-Phenoxypyridine19 and 2-(phenyl-
sulfanyl)pyridine20 were prepared according to the literature.
Other reagents were obtained commercially and used without
purification.
Au–Cl(2)
C(6)–O
C(7)–N
C(1)–Au–N
C(1)–Au–Cl(2)
N–Au–Cl(1)
86.6(6)
177.7(4)
175.2(3)
C(1)–Au–Cl(1)
N–Au–Cl(2)
Cl(1)–Au–Cl(2)
89.5(4)
91.7(4)
92.1(2)
Table 3 Selected bond distances (Å) and angles (Њ) with e.s.d.s in
parentheses for complex 1c
Syntheses
Au–C(1)
Au–Cl(1)
C(1)–C(6)
C(7)–S
2.04(2)
2.277(4)
1.41(3)
1.76(2)
Au–N
2.07(1)
2.384(4)
1.77(2)
1.36(2)
[AuCl2(pap-C1, N)] 1a. An ethanol (5 cm3) solution of 2-
anilinopyridine (0.128 g, 0.752 mmol) was added to a solution
of H[AuCl4]ؒ4H2O (0.104 g, 0.251 mmol) in the same solvent (5
cm3) and the resulting solution stirred at room temperature.
After 15 h, the yellow precipitates obtained were filtered off and
washed with diethyl ether to give complex 1a (0.096 g, 88%), mp
253 ЊC (decomp.) (Found: C, 30.1; H, 2.1; N, 6.35. C11H9Au-
Cl2N2 requires C, 30.25; H, 2.1; N, 6.4%); νmax/cmϪ1 (KBr) 356,
284 (Au–Cl).
Au–Cl(2)
C(6)–S
C(7)–N
C(1)–Au–N
C(1)–Au–Cl(2)
N–Au–Cl(1)
88.3(6)
178.4(5)
176.8(5)
C(1)–Au–Cl(1)
N–Au–Cl(2)
Cl(1)–Au–Cl(2)
89.6(5)
90.2(4)
91.9(1)
Table 4 Selected bond distances (Å) and angles (Њ) with e.s.d.s in
parentheses for complex 5a
Complex 1a was also prepared in a similar way using Na-
[AuCl4]ؒ2H2O (0.100 g, 0.252 mmol) and 2-anilinopyridine
(0.091 g, 0.535 mmol) (yield of 1a: 0.107 g, 93%).
Au–C(1)
Au–Cl
C(1)–C(6)
C(7)–N(2)
2.06(1)
2.347(4)
1.37(2)
1.40(2)
Au–N(1)
Au–P
C(6)–N(2)
C(7)–N(1)
2.09(1)
2.319(3)
1.42(2)
1.33(2)
[AuCl2(pop-C1, N)] 1b. Method (a). An ethanol solution
(5 cm3) of 2-phenoxypyridine (0.045 g, 0.264 mmol) was added
to a solution of H[AuCl4]ؒ4H2O (0.102 g, 0.248 mmol) in water
(25 cm3), whereupon yellow precipitates appeared. When the
resulting suspension was heated at 105 ЊC for 14 h the precipi-
tates turned to white. They were collected and recrystallized
from dichloromethane and hexane to give complex 1b (0.077 g,
71%) as white microcrystals, mp 240 ЊC (decomp.) (Found: C,
30.15; H, 1.85; N, 3.15. C11H8AuCl2NO requires C, 30.15; H,
1.85; N, 3.2%); νmax/cmϪ1 (KBr) 361, 303 (Au–Cl). Complex 1b
was also prepared similarly in 81% yield in propan-2-ol–water
(1:5).
C(1)–Au–N(1)
C(1)–Au–Cl
N–Au–P
85.2(5)
174.9(4)
176.5(3)
C(1)–Au–P
N–Au–Cl
Cl(1)–Au–P
94.5(4)
90.3(3)
89.8(1)
Table 5 Selected bond distances (Å) and angles (Њ) with e.s.d.s in
parentheses for complex 7a
Au–C(1)
Au–P(2)
C(1)–C(6)
C(7)–N(2)
2.039(8)
2.361(3)
1.40(1)
1.37(1)
Au–P(1)
Au–Cl
C(6)–N(2)
C(7)–N(1)
2.365(3)
2.371(3)
1.40(1)
1.32(1)
Method (b). An acetonitrile–water suspension (1:5, 24 cm3)
containing the salt [H2pop][AuCl4] 2b (0.199 g, 0.389 mmol)
was heated at 105 ЊC for 40 h. The resulting precipitates were
collected and extracted with hot acetone (20 cm3). The extract
was concentrated to give white microcrystals of complex 1b
(yield 0.112 g, 66%).
C(1)–Au–P(1)
C(1)–Au–Cl
P(1)–Au–P(2)
89.9(2)
173.1(3)
175.2(1)
C(1)–Au–P(2)
P(1)–Au–Cl
Cl–Au–P(2)
88.9(3)
87.45(9)
93.2(1)
Method (c). A yellow suspension of [AuCl3(Hpop)] 3b (0.077
g, 0.163 mmol) in acetonitrile–water (1:5, 24 cm3) was heated
at 105 ЊC for 18 h. The resulting white precipitates were
collected and recrystallized from dichloromethane and hexane
to give complex 1b (0.055 g, 78%).
membered auracycles derived from N,N-dimethylbenzylamine
[82.2(4)Њ],17 4,4-dimethyl-2-phenyl-1,3-oxazoline [81.7(3)Њ],10 4-
butyl-N-(3,4,5-trimethoxybenzylidene)aniline[81.41(14)Њ]11 and
4,4Ј-dimethylazobenzene [80.1(2)Њ]18 and are comparable to the
values in the six-membered auracycles [AuCl(C6H4CH2C5H4N-
C1, N)(PPh3)]BF4 [85.8(4)Њ],6 [AuCl2(C6H4CMe2C5H4N-C1,
N)] [85.7(1)Њ],7 [AuCl2(C6H4COC5H4N-C1, N)] [89.5(3)Њ]6 and
[AuCl2(pap-C1, N)] [87.3(9)Њ].12 The pap–Au ring structure in 5a
was quite similar to that of [AuCl2(pap-C1, N)].12 In complexes
1b and 1c the Au–Cl(2) bond [2.369(5) (1b) and 2.384(4) Å (1c)]
is longer than Au–Cl(1) [2.275(4) (1b) and 2.277(4) Å (1c)]
owing to the greater trans influence of the aryl carbon atom
than the nitrogen atom.
Concerning the structure of complex 7a, as expected from
spectroscopic data it was confirmed that two PEt3 ligands are
located trans to each other and the 2-(2-pyridylamino)phenyl
ligand is co-ordinated to Au only through the C(1) atom,
forming a neutral complex. The phenyl ring in the 2-(2-
pyridylamino)phenyl moiety is located nearly perpendicular to
the gold() square plane (dihedral angle between two planes
is 78.8Њ). There are no gold–nitrogen bonding interactions
[N(1), 3.218(8); N(2), 5.109(9) Å], excluding a five-co-ordinate
gold() configuration.
[AuCl2(ptp-C1, N)] 1c. Method (a). An ethanol solution
(5 cm3) of 2-(phenylsulfanyl)pyridine (0.048 g, 0.256 mmol) was
added to a solution of H[AuCl4]ؒ4H2O (0.102 g, 0.248 mmol)
in water (25 cm3), and the resulting mixture heated at 105 ЊC for
14 h. The resulting yellow suspension was filtered while hot.
From the filtrate yellow microcrystals of complex 4c (0.010 g)
were precipitated on standing at room temperature. The filter
cake was extracted with dichloromethane and the extract con-
centrated and diluted with hexane to give 1c (0.014 g, 12%).
Complex 4c (Found: C, 25.2; H, 1.55; N, 2.65%); νmax/cmϪ1
(KBr) 357 (Au–Cl); δH(DMSO-d6) 7.95 (2 H), 8.16 [1 H, t, 3JHH
=
6.8], 8.53 (2 H, m), 8.91 (2 H, m), 10.10 [1 H, d, 3JHH = 6.4 Hz].
Complex 1c: mp 239 ЊC (decomp.) (Found: C, 29.1; H, 1.8; N,
3.1. C11H8AuCl2NS requires C, 29.0; H, 1.85; N, 3.05%); νmax
/
cmϪ1 (KBr) 360, 295 (Au–Cl). Complex 1c was also prepared
similarly in 13% yield in propan-2-ol–water (1:5).
Method (b). An acetonitrile–water suspension (1:5, 30 cm3)
4098
J. Chem. Soc., Dalton Trans., 1998, 4095–4100

View Article Online
containing the salt [H2ptp][AuCl4] 2c (0.200 g, 0.379 mmol) was
heated at 105 ЊC for 20 h. The resulting mixture was filtered
while hot. From the filtrate yellow microcrystals of complex 4c
(0.023 g) were precipitated, while from the filter cake after wash-
ing with hot water using a Soxhlet extraction apparatus yellow
microcrystals of 1c were obtained (0.035 g, 20%).
the extract concentrated and diluted with diethyl ether to yield
yellow microcrystals of 5a (0.139 g, 80%), mp 153 ЊC (decomp.)
(Found: C, 46.7; H, 3.35; N, 3.75. C29H24AuBClF4N2P requires
C, 46.4; H, 3.2; N, 3.65%); νmax/cmϪ1 (KBr) 1060 (BF4Ϫ), 313
(Au–Cl); ΛM(1.0 × 10Ϫ3 mol dmϪ3, acetone) 169 S cm2 molϪ1
.
Method (c). An acetonitrile–water suspension (1:5, 30 cm3)
containing the adduct [AuCl3(Hptp)] 3c (0.201 g, 0.409 mmol)
was heated at 105 ЊC for 20 h and then the mixture was filtered
while hot. From the filtrate yellow microcrystals of complex 4c
(0.022 g) were obtained. The filter cake was extracted with
dichloromethane and the extract concentrated and diluted with
hexane to give 1c (0.034 g, 18%).
[AuCl(pap-C1)(PPh3)2]Cl 6a. Triphenylphosphine (0.288 g,
1.10 mmol) was added to an acetone solution (10 cm3) of com-
plex 1a (0.201 g, 0.460 mmol). After the mixture was stirred at
room temperature for 1 d the volatile materials were evaporated
in vacuo. The residue was extracted with dichloromethane and
the extract concentrated and diluted with diethyl ether to afford
yellowish white microcrystals of 6aؒH2O (0.287 g, 90%), mp
131 ЊC (Found: C, 57.5; H, 4.25; N, 2.85. C47H41AuCl2N2-
OP2 requires C, 57.6; H, 4.2; N, 2.85%); νmax/cmϪ1 (KBr) 295
[H2pop][AuCl4] 2b. An ethanol (5 cm3) solution of 2-
phenoxypyridine (0.171 g, 0.999 mmol) was added to a solution
of H[AuCl4]ؒ4H2O (0.203 g, 0.493 mmol) in the same solvent (5
cm3) and the resulting solution stirred at room temperature
for 1 d. The resulting mixture was evaporated to dryness and
the residue extracted with dichloromethane. The extract was
concentrated and diluted with hexane to give yellow micro-
crystals of complex 2b (0.233 g, 92%), mp 108 ЊC (decomp.)
(Found: C, 26.05; H, 1.9; N, 2.7. C11H10AuCl4NO requires C,
25.85; H, 1.95; N, 2.75%); νmax/cmϪ1 (KBr) 360 (Au–Cl);
(Au–Cl); ΛM(1.0 × 10Ϫ3 mol dmϪ3, MeOH) 123 S cm2 molϪ1
.
[AuCl(pap-C1)(PEt3)2]Cl 7a. Complex 7a was obtained as
beige microcrystals in a similar way to that described above by
the reaction between 1a (0.105 g, 0.239 mmol) and PEt3 (0.118
g, 1.00 mmol) in acetone (10 cm3), yield 0.128 g (80%), mp
139 ЊC (Found: C, 41.15; H, 5.9; N, 4.15. C23H39AuCl2N2P2
requires C, 41.0; H, 5.85; N, 4.1%); νmax/cmϪ1 (KBr) 300
(Au–Cl); ΛM(1.0 × 10Ϫ3 mol dmϪ3, acetone) 24 S cm2 molϪ1
.
ΛM(1.0 × 10Ϫ3 mol dmϪ3, acetone) 157 S cm2 molϪ1
.
[AuCl2(pop-C1)(PPh3)] 8b. Triphenylphosphine (0.031 g,
0.118 mmol) was added to a dichloromethane solution (10 cm3)
of complex 1b (0.050 g, 0.114 mmol). The resulting solution
was stirred at room temperature for 18 h and then filtered. The
filtrate was concentrated and diluted with diethyl ether to give
white microcrystals of 8b (0.068g, 84%), mp 146 ЊC (Found: C,
49.75; H, 3.45; N, 2.15. C29H23AuCl2NOP requires C, 49.75; H,
3.3; N, 2.0%); νmax/cmϪ1 (KBr) 325, 301 (Au–Cl); ΛM(1.0 × 10Ϫ3
[H2ptp][AuCl4] 2c. Complex 2c was obtained as orange
microcrystals in a similar way to that described above by the
reaction between 2-(phenylsulfanyl)pyridine (0.185 g, 0.990
mmol) and H[AuCl4]ؒ4H2O (0.196 g, 0.475 mmol) in ethanol
(10 cm3), yield 0.182 g (73%), mp 149 ЊC (decomp.) (Found: C,
25.3; H, 1.95; N, 2.7. C11H10AuCl4NS requires C, 25.05; H, 1.9;
N, 2.65%); νmax/cmϪ1 (KBr) 360 (Au–Cl); ΛM(1.0 × 10Ϫ3 mol
dmϪ3, acetone) 166 S cm2 molϪ1
.
mol dmϪ3, MeOH) 1.4 S cm2 molϪ1
.
[AuCl3(Hpop)] 3b. Method (a). An acetonitrile (5 cm3) solu-
tion of 2-phenoxypyridine (0.023 g, 0.134 mmol) was added to
a solution of Na[AuCl4]ؒ2H2O (0.051 g, 0.127 mmol) in water
(25 cm3), whereupon bright yellow microcrystals were precipi-
tated. After the resulting suspension was stirred for 15 h at
room temperature, the crystals were filtered off to give complex
3b (0.060 g, 74%), mp 167 ЊC (decomp.) (Found: C, 27.95; H,
1.95; N, 2.95. C11H9AuCl3NO requires C, 27.85; H, 1.9; N,
[AuCl2(ptp-C1)(PPh3)] 8c. Complex 8c was obtained as white
microcrystals in a similar way to that described above by the
reaction between 1c (0.062 g, 0.137 mmol) and PPh3 (0.038 g,
0.144 mmol), yield 0.084 g (86%), mp 170 ЊC (Found: C, 48.8;
H, 3.2; N, 1.9. C29H23AuCl2NPS requires C, 48.6; H, 3.25; N,
1.95%); νmax/cmϪ1 (KBr) 316, 301 (Au–Cl); ΛM(1.0 × 10Ϫ3 mol
dmϪ3, acetone) 7.3 S cm2 molϪ1
.
2.95%); νmax/cmϪ1 (KBr) 365 (Au–Cl); ΛM(1.0 × 10Ϫ3 mol dmϪ3
,
X-Ray crystallography
acetone) 1.3 S cm2 molϪ1
.
Method (b). Water (25 cm3) was added to an acetonitrile
solution of complex 2b (0.125 g, 0.245 mmol) and the resulting
suspension stirred for 16 h at 25 ЊC. Yellow precipitates were
collected and washed with water to give 3b (0.106 g, 91%).
Suitable crystals of [AuCl2(pop-C1, N)] 1b, [AuCl2(ptp-C1, N)]
1c, [AuCl(pap-C1, N)(PPh3)]BF4 5a and [AuCl(pap-C1)-
(PEt3)2]Cl 7a were grown from dichloromethane and hexane
except for 1b (dichloromethane and diethyl ether). Details of
the crystal data, data collection and refinement are summarized
in Table 6. Measurements were made on Rigaku AFC7S (for
1b, 5a and 7a) and Enraf-Nonius CAD4 (for 1c) diffract-
ometers with graphite-monochromated Mo-Kα radiation
(λ = 0.71069 Å) at 23 ЊC except for 1c (20 ЊC). Cell constants
were obtained from a least-squares refinement of the setting
angles of 25 reflections in the range 29.2 < 2θ < 30.1Њ for 1b,
20.0 < 2θ < 30.0Њ for 1c, 27.0 < 2θ < 29.23Њ for 5a and
33.7 < 2θ < 34.8Њ for 7a. Intensity data were collected by the
ω–2θ scan technique and corrected for Lorentz-polarization
effects and absorption. All the calculations for 1b, 5a and 7a
were performed using the TEXSAN software package,21 where-
as those for 1c were carried out on a VAX station 4000 90A
computer using a MO1EN program package.22 The structures
of 1b and 1c were solved by direct methods and expanded using
Fourier techniques. The non-hydrogen atoms were refined
anisotropically, and the hydrogen atoms included but not
refined. The structure of 5a was solved by heavy-atom
Patterson methods and expanded using Fourier techniques. All
non-hydrogen atoms except for the tetrafluoroborate anion
were refined anisotropically. The position of NH was freely
[AuCl3(Hptp)] 3c. Method (a). Complex 3c was obtained as
bright orange microcrystals in a similar way to that described
above by the reaction between 2-(phenylsulfanyl)pyridine
(0.075 g, 0.402 mmol) and Na[AuCl4]ؒ2H2O (0.151 g, 0.380
mmol) in acetonitrile–water (1:5, 30 cm3, yield 0.145 g (78%),
mp 168 ЊC (decomp.) (Found: C, 27.0; H, 1.9; N, 2.85.
C11H9AuCl3NS requires C, 26.95; H, 1.85; N, 2.85%); νmax/cmϪ1
(KBr) 362 (Au–Cl); ΛM(1.0 × 10Ϫ3 mol dmϪ3, acetone) 0.8 S cm2
molϪ1
.
Method (b). Water (25 cm3) was added to an acetonitrile
solution of complex 2c (0.103 g, 0.196 mmol) and the resulting
suspension stirred for 13 h at 25 ЊC. Yellow precipitates
were collected and washed with water to give 3c (0.106 g, 92%).
[AuCl(pap-C1, N)(PPh3)]BF4 5a. Triphenylphosphine (0.063
g, 0.241 mmol) and then sodium tetrafluoroborate (0.028 g,
0.255 mmol) were added to an acetone solution (10 cm3) of
complex 1a (0.100 g, 0.230 mmol). The resulting solution was
stirred for 15 h and then the volatile materials were evaporated
in vacuo. The residue was extracted with dichloromethane and
J. Chem. Soc., Dalton Trans., 1998, 4095–4100
4099

View Article Online
Table 6 Crystallographic data for complexes 1b, 1c, 5a and 7a
1b
1c
5a
7a
Formula
M
C11H8AuCl2NO
438.06
C11H8AuCl2NS
454.13
C29H24AuBClF4N2P
750.72
C23H39AuCl2N2P2
673.39
Crystal system
Space group
Orthorhombic
P212121
Monoclinic
P21/n
Orthorhombic
Pbca
Orthorhombic
P212121
a/Å
b/Å
c/Å
8.22(2)
18.15(2)
7.76(1)
8.488(3)
14.363(3)
10.618(4)
103.74(2)
1257.3(7)
4
20.899(3)
18.940(2)
14.319(2)
15.181(3)
15.873(1)
11.535(2)
β/Њ
U/Å3
1157(2)
4
2.513
5667(2)
8
1.759
2779.6(7)
4
1.609
Z
Dc/g cmϪ3
2.40
Crystal dimensions/mm
0.20 × 0.40 × 0.40
131.84
1577
0.41 × 0.32 × 0.22
122.4
2301
0.35 × 0.20 × 0.30
54.08
7169
0.20 × 0.15 × 0.45
56.31
3596
µ(Mo-Kα)/cmϪ1
No. measured reflections
No. unique observed reflections [I > 3σ(I )]
R
1410
0.039
1617
0.036
3249
0.046
2708
0.028
RЈ
0.048
0.045
0.062
0.029
8 J. Vicente, M. T. Chicote and M. D. Bermudez, Inorg. Chim. Acta,
1982, 63, 35.
9 J. Vicente, M. T. Chicote and M. D. Bermudez, J. Organomet.
Chem., 1984, 268, 191.
10 P. A. Bonnardel, R. V. Parish and R. G. Pritchard, J. Chem. Soc.,
Dalton Trans., 1996, 3185.
11 J. Vicente, M. D. Bermudez, F. J. Carrion and P. G. Jones, Chem.
Ber., 1996, 129, 1301.
refined but its isotropic thermal parameter was fixed. The other
hydrogen atoms were included but not refined. As for the
refinement of the tetrafluoroborate anion, the atom B(1) was
refined isotropically; F(1), F(2), F(3) and F(4) were treated as
an idealized rigid group with a common isotropic atomic dis-
placement parameter because the refinement of individual
parameters of those atoms failed. The structure of 7a was
solved by direct methods and expanded using Fourier tech-
niques. All the non-hydrogen atoms were refined anisotropic-
ally. The position of NH was freely refined but its isotropic
parameters were fixed. The other hydrogen atoms were included
but not refined.
12 M. Nonoyama, K. Nakajima and K. Nonoyama, Polyhedron, 1997,
16, 4039.
13 P. K. Byers and A. J. Canty, Organometallics, 1990, 9, 210.
14 D. Rasala, Bull. Soc. Chim. Fr., 1992, 129, 79.
15 C. K. Johnson, ORTEP, Report ORNL-5138, Oak Ridge National
Laboratory, Oak Ridge, TN, 1976; H. O Liu, T. C. Cheung, S. M.
Peng and C. M. Che, J. Chem. Soc., Chem. Commun., 1995, 1787.
16 J. Vicente, M. D. Bermudez, M. P. Carrillo and P. G. Jones,
J. Organomet. Chem., 1993, 456, 305.
17 J. Vicente, M. T. Chicote, M. D. Bermudez, P. G. Jones and G. M.
Sheldrick, J. Chem. Res., 1985, (S) 72; (M) 954.
18 J. Vicente, M. D. Bermudez, M. P. Carrillo and P. G. Jones, J. Chem.
Soc., Dalton Trans., 1992, 1975.
19 K. Fujiwara, K. Kondo, I. Yokomichi, F. Kimura, T. Haga and
R. Nishiyama, Agr. Biol. Chem., 1970, 34, 68.
20 S. Kondo, M. Nakanishi and K. Tsuda, J. Heterocycl. Chem., 1984,
21, 1243.
21 TEXSAN, Crystal Structure Analysis Package, Molecular
Structure Corporation, Houston, TX, 1985 and 1992.
22 C. K. Fair, MOLEN Structure Determination System, Delft
Instruments, Delft, 1990.
CCDC reference number 186/1206.
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J. Chem. Soc., Dalton Trans., 1998, 4095–4100