Synthesis, structure and reactivity of a new six-membered cycloaurated complex of 2-benzoylpyridine [AuCl2(pcp-C1,N)] [pcp = 2-(2-pyridylcarbonyl)phenyl]. Comparison with the cycloaurated complex derived from 2-benzylpyridine

Article abstract of DOI:10.1039/a706354g

A six-membered cycloaurated complex [AuCl₂(pcp-C¹,N)] [pcp = 2-(2-pyridylcarbonyl)phenyl] has been prepared by the reaction between the adduct [AuCl₃(Hpcp)] (Hpcp = 2-benzoylpyridine) and AgO₂CCF₃, and its structure determined by X-ray diffraction. The boat-like conformation of the six-membered pcp-Au ring has been compared to that of the pmp-Au ring in [AuCl(pmp-C¹,N)(PPh₃)]BF₄ [pmp = 2-(2-pyridylmethyl)phenyl] the structure of which has also been established by X-ray diffraction. The complex [AuCl₂(pcp-C¹,N)] reacts with PPh₃ in a 1:1 molar ratio to give a neutral complex [AuCl₂(pcp)(PPh₃)]. This is further converted into trans-[AuCl(pcp)(PPh₃)₂]BF₄ and [Au(pcp-C¹,N)₂]BF₄ by treating with PPh₃ in the presence of NaBF₄ and excess of AgBF₄, respectively. This reactivity towards triphenylphosphine has been compared with that of the known cycloaurated complex [AuCl₂(pmp-C¹,N]. Temperature-dependent ¹H NMR spectra attributable to inversion of the six-membered pmp-Au ring have been observed and the rates of inversion measured by line shape analysis of the methylene protons in [AuCl(pmp-C¹,N)(PPh₃)]BF₄.

Full text of DOI:10.1039/a706354g

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Synthesis, structure and reactivity of a new six-membered
cycloaurated complex of 2-benzoylpyridine [AuCl2(pcp-C 1,N)]
[pcp ؍ 2-(2-pyridylcarbonyl)phenyl]. Comparison with the
cycloaurated complex derived from 2-benzylpyridine
Yoshio Fuchita,*,†,a Hidenori Ieda,a Yukiko Tsunemune,a Junko Kinoshita-Nagaokab and
Hiroyuki Kawanoc
a Department of Chemistry, Faculty of Science, Kyushu University at Ropponmatsu, Chuo-ku,
Fukuoka 810, Japan
b Department of Applied Chemistry, Faculty of Engineering, Nagasaki University, Bunkyo-machi,
Nagasaki 852, Japan
c Graduate School of Marine Science and Engineering, Nagasaki University, Nagasaki 852, Japan
A six-membered cycloaurated complex [AuCl2(pcp-C1,N)] [pcp = 2-(2-pyridylcarbonyl)phenyl] has been prepared
by the reaction between the adduct [AuCl3(Hpcp)] (Hpcp = 2-benzoylpyridine) and AgO2CCF3, and its structure
determined by X-ray diffraction. The boat-like conformation of the six-membered pcp᎐Au ring has been
compared to that of the pmp᎐Au ring in [AuCl(pmp-C1,N)(PPh3)]BF4 [pmp = 2-(2-pyridylmethyl)phenyl] the
structure of which has also been established by X-ray diffraction. The complex [AuCl2(pcp-C1,N)] reacts with
PPh3 in a 1:1 molar ratio to give a neutral complex [AuCl2(pcp)(PPh3)]. This is further converted into trans-
[AuCl(pcp)(PPh3)2]BF4 and [Au(pcp-C1,N)2]BF4 by treating with PPh3 in the presence of NaBF4 and excess of
AgBF4, respectively. This reactivity towards triphenylphosphine has been compared with that of the known
cycloaurated complex [AuCl2(pmp-C1,N)]. Temperature-dependent 1H NMR spectra attributable to inversion
of the six-membered pmp᎐Au ring have been observed and the rates of inversion measured by line shape analysis
of the methylene protons in [AuCl(pmp-C1,N)(PPh3)]BF4.
In contrast to the rich chemistry of cyclometallation involving
PdII and PtII,1 examples of cycloaurated complexes are limited.
Two types of synthetic methods for cycloaurated compounds
have been reported so far. One is by transmetallation from the
corresponding organomercury() compounds and thereby
cycloaurated complexes of azobenzene,2 N,N-dimethylbenzyl-
amine,3,4 4,4-dimethyl-2-phenyl-1,3-oxazoline,4 1-(dimethyl-
or methyl-aminomethyl)naphthalene,4 1,3-bis(dimethylamino-
methyl)benzene4 and 4-butyl-N-(3,4,5-trimethoxybenzylidene)-
aniline5 have been prepared. The other is by direct C᎐H bond
activation. Thereby cycloaurated complexes of 2-phenyl-
pyridine,6 2-benzylpyridine,7 6-benzyl-2,2Ј-bipyridine deriv-
atives8 and 6-tert-butyl-2,2Ј-bipyridine8 have been synthesized
on heating the corresponding adducts [AuCl3L], while those of
2,9-diphenyl-1,10-phenanthroline9 and 4-(4-methoxyphenyl)-
6-phenyl-2,2Ј-bipyridine10 were obtained by reaction with the
[AuCl4]Ϫ–AgI system.
Concerning the synthesis of six-membered cycloaurated
complexes, examples are very rare and limited to benzylpyridine
derivatives.7,8 Here we describe the synthesis and characteriz-
ation of a new type of six-membered cycloaurated complexes
derived from 2-benzoylpyridine. Comparison of the reactivity
towards triphenylphosphine between [AuCl2(pcp-C1,N)] [pcp =
2-(2-pyridylcarbonyl)phenyl] and previously reported [AuCl2-
(pmp-C1,N)] [pmp = 2-(2-pyridylmethyl)phenyl],7 and a line
shape analysis of the temperature-dependent 1H NMR spectra
attributable to the inversion of the six-membered pmp᎐Au ring
are also described.
NMR spectral data are summarized in Scheme 1 and Table 1,
respectively.
Synthesis of [AuCl2(pcp-C 1,N)] and comparison of the six-
membered pcp᎐Au and pmp᎐Au ring structures
2-Benzoylpyridine (Hpcp) reacted with H[AuCl4]ؒ4H2O in
EtOH to give the adduct [AuCl3(Hpcp)] 1a. When complex
1a was refluxed in propionitrile in the presence of silver()
trifluoroacetate a new six-membered cycloaurated complex of
2-benzoylpyridine, [AuCl2(pcp-C1,N)] 2a [pcp = 2-(2-pyridyl-
carbonyl)phenyl], was obtained in 12% yield (Scheme 1). It is
interesting that no reaction occurred when 1a was refluxed in
acetonitrile or in an acetonitrile–water mixed solvent, while
a similar six-membered cycloaurated complex of 2-benzyl-
pyridine, [AuCl2(pmp-C1,N)] 2b [pmp = 2-(2-pyridylmethyl)-
phenyl], was formed just by heating the adduct [AuCl3(Hpmp)]
in an acetonitrile–water mixed solvent.7 Prolonged heating
decreased the recovery of the starting compound 1a but pro-
moted decomposition of the product 2a. Other silver() salts
such as AgBF4 and AgO2CMe did not work well for the form-
1
ation of 2a. The H NMR spectrum of 2a exhibited only eight
and well separated aromatic protons due to the cycloaurated
moiety and the spectral assignment was performed with the aid
of 1H᎐1H correlation spectroscopy (COSY) (Table 1). In the IR
spectrum 2a showed two bands at 362 and 300 cmϪ1 assignable
to ν(Au᎐Cl) trans to a nitrogen-donor ligand and ν(Au᎐Cl)
trans to carbon atoms, respectively.5 On the basis of these
results, elemental analysis and its reactivity (see below), 2a was
assigned to a six-membered cycloaurated complex.
The structures of complex 2a and [AuCl(pmp-C1,N)-
(PPh3)]BF4 7b (see below) were established by X-ray diffraction
and ORTEP11 views of the molecules are shown in Figs. 1 and 2,
respectively. Selected bond distances and angles are summar-
ized in Tables 2 (for 2a) and 3 (for 7b). The co-ordinations
Results and Discussion
The method of preparation of the complexes and selected H
1
† E-Mail: fuchita@rc.kyushu-u.ac.jp
J. Chem. Soc., Dalton Trans., 1998, Pages 791–796
791

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Table 1 Proton NMR spectra of the new cycloaurated complexesa
Cycloaurated moietyb
Complex
2a [AuCl2(pcp-C1,N)]
H6Ј
Other protons
Others
9.48 (1 H, d)c 7.4–7.55 (2 H, m)
7.65–7.73 (2 H, m)
8.56 (1 H, dt, H4Ј)d
7.11 (1 H, t)e
8.09 (1 H, dt, H5Ј)d
8.37 (1 H, dd, H3Ј)d
3a [AuCl2(pcp-C1)(PPh3)]
4a [AuCl(pcp-C1)(PPh3)2]BF4
5a [Au(pcp-C1,N)2]BF4
8.67 (1 H, d)c 7.00 (1 H, dt)d
7.7–7.45 (1 H, m)f
7.40 (2 H, m)
7.7–7.45 (15 H, m, PPh3) f
7.45–7.7 (30 H, m, PPh3) f
7.80 (1 H, d, H3Ј)e
6.97 (1 H, t)e
8.04 (1 H, dt, H4Ј)d
7.31 (1 H, d)e
8.55 (1 H, d)c 6.93 (1 H, t)e
7.45–7.7 (3 H, m)f
7.98 (1 H, t, H4Ј)e
7.40 (2 H, dt, H5)d
7.91 (2 H, dt, H3Ј)d
8.44 (2 H, d)c 6.83 (2 H, d, H6)e
7.79 (2 H, dd, H3)d
7.50 (2 H, dt, H4)d
8.29 (2 H, d, H4Ј)e
8.52 (2 H, dt, H5Ј)d
6b [AuCl2(pmp-C1,N)(PPh3)]
9.14 (1 H, d)c 6.44 (1 H, dt, H5)d
7.17 (1 H, dd, H6)d
6.74 (1 H, d, H3)e
7.5–7.9 (16 H, m)f
6.93 (1 H, t, H4)e
7.94 (1 H, d, H3Ј)e
4.33 (1 H, d, CH2)g
4.94 (1 H, d, CH2)g
8.22 (1 H, dt, H4Ј)d
7b [AuCl(pmp-C1,N)(PPh3)]BF4 9.17 (d)c
6.43 (1 H, dt, H5)d
7.22 (1 H, dd, H6)d
8.26 (1 H, dt, H4Ј)d
6.72 (1 H, dd, H3)d
7.5–7.9 (16 H, m)f
6.95 (1 H, t, H4)e
7.99 (1 H, d, H3Ј)e
4.34 (1 H, d, CH2)g
5.05 (1 H, d, CH2)g
a Measured in (CD3)2SO 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) = 5.4 Hz. d 3J(HH) = 7.8, 4J(HH) = 1.5 Hz. e 3J(HH) = 7.8 Hz. f Overlapping each other with signals due to PPh3 or
cycloaurated moiety. g 2J(HH) = 15.1 Hz.
5'
4'
3'
6'
N
N
Cl
Cl
Cl
Cl
(i )
(v )
N
N
Au
C
O
Au
C
O
Ph
O
C
BF4
Au
C
O
Cl
1a
3
6
5
4
(iv )
2a
5a
(ii )
(vi )
PPh3
C
Cl
C
O
O
C5H4N
C5H4N
Cl
Cl
(iii )
Au
Au
BF4
Ph3P
Ph3P
4a
3a
N
N
Cl
N
Cl
Cl
Cl
(ii )
(vii )
CH2
Au
CH2
Au
CH2
BF4
Au
Cl
Ph3P
Ph3P
6b
2b
7b
(viii )
Scheme 1 (i) AgO2CCF3; (ii) PPh3; (iii) PPh3, NaBF4; (iv) 2PPh3, NaBF4; (v) PPh3, 3AgBF4; (vi) 3AgBF4; (vii) NaBF4; (viii) PPh3, AgBF4
around the gold atoms of both 2a and 7b are essentially planar
and the maximum deviations are 0.062 and 0.037 Å of the N
atoms from the mean planes composed of Au᎐Cl(1)᎐Cl(2)᎐
N᎐C(1) (for 2a) and Au᎐Cl᎐N᎐P᎐C(1) (for 7b), respectively.
In complex 2a the Au᎐Cl(1) bond [2.381(2) Å] is longer than
Au᎐Cl(2) [2.276(2) Å] owing to the greater trans influence of the
aryl carbon atom than the nitrogen atom. The bond angle
C(1)᎐Au᎐N is 89.5(3)Њ, which is wider than those in five-
membered auracycles derived from N,N-dimethylbenzylamine
[82.2(4)Њ],12 4,4-dimethyl-2-phenyl-1,3-oxazoline [81.7(3)Њ],4
Both the pcp᎐Au and the pmp᎐Au six-membered auracycles
have boat-like conformations, with atoms N, C(1), C(6) and
C(8) essentially coplanar [mean deviations from their best
planes are 0.024 Å for 2a and 0.012 Å for 7b]. In complex 7b this
best plane forms dihedral angles with planes C(6)᎐C(7)᎐C(8)
and N᎐Au᎐C(1) of 46.3 and 42.0Њ, respectively. On the other
hand in complex 2a corresponding dihedral angles have smaller
values of 19.0 and 33.9Њ for planes C(6)᎐C(7)᎐C(8)᎐O and
N᎐Au᎐C(1), respectively. Concerning the dihedral angles
between the benzene and pyridine rings, the value of 140.5Њ in
2a is much wider than that of 114.0Њ in 7b. These results
demonstrate that the planarity of the pcp᎐Au ring is higher
than that of the pmp᎐Au ring, which is probably due to the
different hybridization of the carbon atom between the benzene
4-butyl-N-(3,4,5-trimethoxybenzylidene)aniline
[81.41(14)Њ]5
and 4,4Ј-dimethylazobenzene [80.1(2)Њ]13 and is the widest in
six-membered auracycles ever reported {7b, 85.8(4)Њ; [AuCl2-
(C6H4CMe2C5H4N-C1,N)], 85.7(1)Њ7}.
792
J. Chem. Soc., Dalton Trans., 1998, Pages 791–796

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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 2a
Table 3 Selected bond distances (Å) and angles (Њ) with e.s.d.s. in
parentheses for complex 7b
Au᎐C(1)
Au᎐Cl(1)
C(1)᎐C(6)
C(7)᎐O
2.033(7)
2.381(2)
1.395(9)
1.213(8)
1.355(8)
Au᎐N
2.035(5)
2.276(2)
1.486(10)
1.501(10)
Au᎐C(1)
Au᎐Cl
C(1)᎐C(6)
C(7)᎐C(8)
2.03(1)
Au᎐N
Au᎐P
C(6)᎐C(7)
C(8)᎐N
2.079(10)
2.311(3)
1.50(2)
Au᎐Cl(2)
C(6)᎐C(7)
C(7)᎐C(8)
2.362(3)
1.38(2)
1.47(2)
1.33(1)
C(8)᎐N
C(1)᎐Au᎐N
C(1)᎐Au᎐Cl
N᎐Au-P
85.8(4)
175.2(3)
176.4(3)
C(1)᎐Au᎐P
N᎐Au᎐Cl
Cl᎐Au᎐P
94.8(3)
89.4(3)
89.9(1)
C(1)᎐Au᎐N
C(1)᎐Au᎐Cl(1) 177.4(2)
N᎐Au᎐Cl(2) 176.2(2)
89.5(3)
C(1)᎐Au᎐Cl(2)
N᎐Au᎐Cl(1)
Cl(1)᎐Au᎐Cl(2)
90.3(2)
92.0(2)
88.29(7)
a neutral complex 3a (ΛM 3.9 S cm2 molϪ1). In the far-IR spec-
trum of 3a two bands characteristic of ν(Au᎐Cl) frequencies
trans to PPh3 and phenylene were observed at 325 and 301
cmϪ1, respectively.5 Moreover, the resonance of the H6Ј proton
in the pyridine moiety of 3a (see Scheme 1) significantly shifted
to upfield at δ 8.67 compared to δ 9.48 for 2a. These data
together with elemental analysis clearly showed that PPh3
cleaved the C᎐N chelate by dissociating the pyridine-nitrogen
co-ordination. Concerning the ν(CO) band, this appeared
at 1638 cmϪ1 for 3a which is lower than 1674 cmϪ1 for 2a and
1669 cmϪ1 for the free 2-benzoylpyridine. So, there may be some
possibility that 3a is a five-co-ordinate complex, but reported
five-co-ordinate species of AuIII, such as [AuCl3L] (L = 2,2Ј-
biquinolyl),14 [AuX3L] [L = 2,9-dimethyl-1,10-phenanthroline
or 2-(2-pyridyl)quinoline];16 X = Cl, Br and {Au(2-Me2NCH2-
C6H4-C1,N)(phen)(PPh3)[BF4]2},17 usually contain rigid biden-
tate ligands. Considering that the pcp ligand has more degrees
of freedom, 3a was tentatively assigned to the normal four-co-
ordinate complex [AuCl2(pcp-C1)(PPh3)]. Further treatment of
PPh3 with 3a in the presence of NaBF4 gave a cationic complex
4a. This complex resembled 3a in IR [ν(CO) 1635 cmϪ1] and 1H
NMR (H6Ј, δ 8.55) spectra except for incorporation of 2 mol-
ecules of PPh3 confirmed to be mutually trans on the basis of
the observation of only one signal at δ 35.43 in the 31P-{1H}
NMR spectrum. Moreover, the far-IR spectrum exhibited only
one ν(Au᎐Cl) at 317 cmϪ1 and the electric conductivity showed
a typical value for a 1:1 electrolyte (ΛM 108 S cm2 molϪ1 in
acetone). Similarly to 3a, a four-co-ordinate structure, trans-
[AuCl(pcp-C1)(PPh3)2]BF4, was tentatively assigned for 4a.
Unfortunately, we have not succeeded in getting crystals suit-
able for X-ray crystal analysis.
Fig. 1 An ORTEP view of complex [AuCl2(pcp-C1,N)] 2a
On the other hand, complex 2b reacted with an equimolar
1
amount of PPh3 to give 6b. In the H NMR spectrum the
methylene protons appeared as an AB quartet and the H6Ј pro-
ton in the pyridine moiety resonated at δ 9.14 which is essen-
tially the same chemical shift as that of 2b (δ 9.17). The data
strongly indicated that the six-membered pmp᎐Au chelate
remains unchanged. Concerning the far-IR spectrum, medium
and strong bands due to ν(Au᎐Cl) were observed at 316 and 295
cmϪ1, respectively, suggesting the co-ordination of the two
chloride ions. On the basis of these spectroscopic data, 6b was
assigned as a five-co-ordinate complex [AuCl2(pmp-C1,N)-
(PPh3)]. As for the molar conductivity, a slightly higher value
than for a non-electrolyte was obtained (16 S cm2 molϪ1), which
threw doubt on the five-co-ordination, but similar values have
been reported for other five-co-ordinate complexes [AuCl2-
Fig. 2 An ORTEP view of complex [AuCl(pmp-C1,N)(PPh3)]BF4 7b
and pyridine rings (sp2 in pcp᎐Au and sp3 in pmp᎐Au). Con-
sidering the fact that all the atoms constructing 2-benzoyl-
pyridine have sp2 hybridization, it is reasonable to think that the
pcp᎐Au ring has a strong tendency to have a planar conform-
ation. From this standpoint, in the ideal planar six-membered
pcp᎐Au ring the bond angle C(1)᎐Au᎐N in 2a should be 120Њ.
The actual value [89.5(3)Њ] is ideal for the square-planar
configuration, but much smaller for the planar six-membered
pcp᎐Au ring indicating the presence of strain in it.
(C H N᎐NPh-C1)(phen)] (Λ 17 S cm2 molϪ1)18 and [AuCl-
᎐
6
4
M
(C4Ph4)(phen)] (ΛM 13 S cm2 molϪ1).19 Unlike 4a, in the pres-
ence of NaBF4 6b did not react further with PPh3, but afforded
a cationic four-co-ordinate complex [AuCl(pmp-C1,N)(PPh3)]-
BF4 7b. Its molar conductivity showed a typical value for a 1:1
electrolyte (ΛM 139 S cm2 molϪ1 in acetone). Complex 7b could
be also prepared by the reaction between 2b, PPh3 and AgBF4
in a molar ratio of 1:1:1.
In order to get [AuCl(pcp-C1,N)(PPh3)]BF4, a pcp analogue
of 7b, the reaction of 2a with an equimolar amount of PPh3
was investigated in the presence of AgBF4. When equimolar
AgBF4 was used the reaction products were complicated and
Reactivity of [AuCl2(pcp-C 1,N)] 2a and [AuCl2(pmp-C 1,N)] 2b
towards triphenylphosphine
Complex 2a reacted with an equimolar amount of PPh3 to give
J. Chem. Soc., Dalton Trans., 1998, Pages 791–796
793

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quartet from the geminal CH2 protons. Fig. 3 shows the
H
a (ax)
experimental and simulated spectra together with the exchange
rate kobs. Activation parameters calculated from the Arrhenius
and Eyring equations were Ea = 78.2 kJ molϪ1, ∆G‡ (300
K) = 70.5 kJ molϪ1, ∆H‡ = 75.2 kJ molϪ1 and ∆S‡ = 15.8 J KϪ1
molϪ1. The comparatively small value of ∆S‡ indicates that
the transition state for the inversion does not involve bond
breaking.
Hb
Au
(eq)
N
N
Ha
Au
(eq)
Hb(ax)
A
B
Scheme 2 Inversion of the six-membered pmp᎐Au ring
Experimental
General
The IR spectra were measured on a JASCO FT/IR-420 spec-
trophotometer, 1H and 31P-{1H} NMR spectra on JEOL JNM
GX-270 and GX-400 spectrometers using tetramethylsilane as
an internal standard and trimethyl phosphite as an external
standard, respectively. 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. The
FAB mass spectrum was recorded on a JEOL-SX102A spec-
trometer. The complex [AuCl2(pmp-C1,N)] 2b was prepared by
a published procedure7 or by the reaction of [AuCl3(Hpmp)]
with AgBF4 in refluxing acetonitrile (yield 58%). Other
reagents were obtained commercially and used without
purification.
Syntheses
[AuCl3(Hpcp)] 1a. An ethanol (15 cm3) solution of 2-benzoyl-
pyridine (0.358 g, 1.95 mmol) was added to a solution of
HAuCl4ؒ4H2O (0.400 g, 0.971 mmol) in the same solvent (15
cm3) and the resulting solution was stirred at room temperature.
After 8 h the yellow precipitate was filtered off and washed with
diethyl ether to give complex 1a (0.297 g, 63%), m.p. 188 ЊC
(decomp.) (Found: C, 29.0; H, 2.1; N, 2.8. C12H9AuCl3NO
requires C, 29.6; H, 1.85; N, 2.9%); ν max/cmϪ1 (KBr) 1671 (CO)
1
Fig. 3 Methylene region of the H NMR spectra of complex 7b. (a)
Observed spectra, (b) simulated curves
no complexes could be isolated. However, when a three-fold
excess of AgBF4 was used the reaction proceeded cleanly and
a bis-chelated complex [Au(pcp-C1,N)2]BF4 5a was isolated.
In this reaction AgBF4 is considered to act as an abstracting
3
and 353 (Au᎐Cl); δH[(CD3)2SO] 8.73 [1 H, d, J(HH) 7.8, H6Ј],
8.15–7.95 (4 H, aromatic protons) and 7.75–7.5 (4 H, aromatic
protons).
20
reagent for PPh3 as well as chloride ions. Separately, 5a
[AuCl2(pcp-C 1,N)] 2a. A propionitrile (5 cm3) solution of
AgO2CCF3 (0.232 g, 1.05 mmol) was added to a solution
of complex 1a (0.400 g, 0.971 mmol) in the same solvent
(10 cm3). After refluxing for 38 h the resulting mixture was
filtered while hot. The yellow filtrate was concentrated to give
white crystals, which were filtered off and washed with diethyl
ether to yield 2a (0.052 g, 12%), m.p. 248 ЊC (decomp.)
(Found: C, 31.8; H, 1.75; N, 3.25. C12H8AuCl2NO requires C,
32.0; H, 1.8; N, 3.1%); ν max/cmϪ1 (KBr) 1674 (CO), 362 (Au᎐Cl)
and 300 (Au᎐Cl).
was also obtained by treating 3a with a three-fold excess of
AgBF4, but the reaction of 2a with only a two-fold excess
of AgBF4 (without PPh3) again formed an intractable
1
mixture. The H NMR spectrum of 5a exhibited no signals
due to PPh3 but showed completely separated eight aro-
matic protons owing to the chelated pcp ring in the range
δ 6.83–8.44. The FAB mass spectrum gave a parent peak
at m/z 561 attributable to [Au(pcp-C1,N)2]ϩ. The conductivity
in acetone revealed that 5a was a 1:1 electrolyte (ΛM 137 S
cm2 molϪ1). These data together with elemental analysis con-
firmed the formation of 5a. The mechanism is not clear at
[AuCl2(pcp-C 1)(PPh3)] 3a. An acetone (5 cm3) solution of
PPh3 (0.029 g, 0.111 mmol) was added to an acetone (10 cm3)
suspension of complex 2a (0.050 g, 0.111 mmol), and then
the mixture was stirred at room temperature for 18 h. The
resulting solution was filtered and the filtrate concentrated.
Addition of diethyl ether afforded white microcrystals of
3a (0.077 g, 98%), m.p. 176 ЊC (decomp.) (Found: C, 51.0;
H, 3.45; N, 2.0. C30H23AuCl2NOP requires C, 50.6; H,
3.25; N, 1.95%); ΛM(1 x 10Ϫ3 mol dmϪ3, acetone) 3.9 S cm2
molϪ1; ν max/cmϪ1 (KBr) 1638 (CO), 325 (Au᎐Cl) and 301
(Au᎐Cl); 31P-{1H} NMR [161.9 MHz, 303 K, (CD3)2SO] δ
29.8 (s).
this stage. Similar bis-chelated gold() complexes have been
reported for [Au(C H N᎐NPh-C1,N) ]X (X = ClO or AuCl )21
Ϫ
᎐
6
4
2
4
4
and [Au(C H N᎐NPh-C1,N)(C H CH NMe -C1,N)]X (X =
᎐
6
4
Ϫ
6
4
2
2
ClO4 or AuCl4 ),22 the structures of which were determined
by X-ray diffraction study to involve a cis geometry of the two
chelated rings.
Line shape analysis of [AuCl(pmp-C 1,N)(PPh3)]BF4 7b
1
Temperature-dependent H NMR spectra attributable to the
inversion of the six-membered pmp᎐Au ring between the con-
formations A and B (Scheme 2) were observed for 7b. In the
low-temperature limiting spectrum of 7b at 25 ЊC in (CD3)2SO
the methylene protons were observed as an AB quartet (Fig.
3). The signals began to broaden near 55 ЊC, reached coales-
cence point near 80 ЊC, and changed into a singlet at 115 ЊC.
The rate of exchange of the two equally populated forms of
complex 7b was measured by line shape analysis of the AB
[AuCl(pcp-C 1)(PPh3)2]BF4 4a. Method (a). To a methanol (10
cm3) solution of complex 3a (0.052 g, 0.073 mmol) was added
successively a methanol (5 cm3) solution of PPh3 (0.021 g, 0.079
mmol) and NaBF4 (0.041 g, 0.372 mmol). The resulting mixture
was evaporated to dryness and the residue extracted with
794
J. Chem. Soc., Dalton Trans., 1998, Pages 791–796

View Article Online
dichloromethane. The extract was concentrated and diluted
with diethyl ether to give white microcrystals of 4a (0.049 g,
66%), m.p. 165 ЊC (decomp.) (Found: C, 56.55; H, 3.85; N, 1.4.
C48H38AuBClF4NOP2 requires C, 56.2; H, 3.75; N, 1.35%);
ΛM(1 × 10Ϫ3 mol dmϪ3, acetone) 108 S cm2 molϪ1; ν max/cmϪ1
(KBr) 1635 (CO), 1060 ([BF4]Ϫ) and 317 (Au᎐Cl); 31P-{1H}
NMR [161.9 MHz, 303 K, (CD3)2SO] δ 35.4 (s).
Table 4 Crystallographic data for complexes 2a and 7bؒCH2Cl2*
2a
7bؒCH2Cl2
Formula
M
C12H8AuCl2NO
450.07
C31H27AuBCl3F4NP
834.66
Crystal system
Space group
Triclinic
P1
Monoclinic
P21/c
¯
Method (b). Triphenylphosphine (0.058 g, 0.222 mmol) was
added to an acetone (10 cm3) suspension of complex 2a (0.051
g, 0.112 mmol). After the resulting mixture changed into a solu-
tion, NaBF4 (0.062 g, 0.563 mmol) was added. The resulting
mixture was stirred for 4 h at room temperature and then the
volatile materials were evaporated. The residue was extracted
with dichloromethane and the extract concentrated to yield 4a
(0.070 g, 61%).
a/Å
b/Å
c/Å
α/Њ
8.594(5)
10.427(6)
7.635(6)
109.86(5)
111.23(5)
88.79(5)
595.7(7)
2
13.382(7)
10.935(3)
22.611(3)
β/Њ
100.59(2)
γ/Њ
U/Å3
3252(1)
4
1642
1.705
Z
F(000)
416
2.510
Dc/g cmϪ3
[Au(pcp-C 1,N)2]BF4 5a. Method (a). To an acetone (15 cm3)
suspension of complex 2a (0.051 g, 0.112 mmol) was added
PPh3 (0.033 g, 0.126 mmol) and then AgBF4 (0.074 g, 0.382
mmol). The resulting mixture was stirred for 7 h at room
temperature and then filtered. The filtrate was concentrated
to give crude product as white microcrystals (0.023 g, 32%).
This crude product was recrystallized from MeCN–diethyl
ether to yield 5aؒH2O (0.016 g, 22%), m.p. 242 ЊC (decomp.)
(Found: C, 43.05; H, 2.6; N, 4.35. C24H18AuBF4N2O3 requires
C, 43.25; H, 2.7; N, 4.2%); ΛM(1.0 × 10Ϫ3 mol dmϪ3, acetone)
137 S cm2 molϪ1; ν max/cmϪ1 (KBr) 1671 (CO) and 1060
([BF4]Ϫ).
Crystal dimensions/mm
µ(Mo-Kα)/cmϪ1
Scan range/Њ
No. measured reflections
No. unique observed
reflections [I > 3σ(I)]
R, RЈ
0.20 × 0.30 × 0.40 0.15 × 0.35 × 0.55
128.23
1.84 ϩ 0.30 tan θ
2916
48.80
1.52 ϩ 0.30 tan θ
8196
4588
2379
0.029, 0.030
0.053, 0.050
* Details in common: scan speed 16Њ minϪ1; 2θmax 55Њ; R = Σ Fo| Ϫ |Fc
/
¹
Σ|Fo|, R1 = (Σw Fo| Ϫ |Fc /Σw|Fo| ) , w = 1/σ (Fo).
2
2
2
²
dichloromethane–diethyl ether, respectively. Details of the
crystal data, data collection and refinement are summarized
in Table 4. All measurements were made on a Rigaku AFC7S
diffractometer with graphite-monochromated Mo-Kα radi-
ation (λ = 0.710 69 Å) at 20 ЊC. Cell constants were obtained
from a least-squares refinement of the setting angles of 23
reflections in the range 39.39 < 2θ < 40.39Њ for 2a and 25
reflections in the range 35.98 < 2θ < 39.29Њ for 7b. During the
data collection the intensities of three representative reflec-
tions were measured after every 150 and an absorption correc-
tion based on azimuthal scans of several reflections was applied
for 2a (transmission range 0.70–1.00) and 7b (transmission
range 0.45–1.00). The observed data were corrected for
Lorentz–polarization effects. All the calculations were per-
formed using the TEXSAN software package.23 Complex 7b
includes a CH2Cl2 molecule as solvent. The structures were
solved by direct methods, expanded using Fourier techniques
and refined by full-matrix least squares on F2. The non-
hydrogen atoms were refined anisotropically. While for 2a
hydrogen atoms were refined isotropically, for 7b they were
included but not refined.
Method (b). To an acetone (8 cm3) solution of complex 3a
(0.079 g, 0.111 mmol) was added an acetone (8 cm3) solution
of AgBF4 (0.065 g, 0.335 mmol). The resulting mixture was
stirred overnight at ambient temperature. After the volatile
materials were evaporated, the residue was extracted in prop-
ionitrile. Addition of diethyl ether gave 0.024 g (63%) of
5aؒH2O.
[AuCl2(pmp-C 1,N)(PPh3)] 6b. Triphenylphosphine (0.030 g,
0.115 mmol) was added to an acetonitrile (10 cm3) suspension
of complex 2b (0.050 g, 0.115 mmol). The resulting solution
was stirred at room temperature for 18 h and then the volatile
materials were removed in vacuo. The residue was extracted
with acetone and the extract concentrated. Addition of
diethyl ether gave 6bؒH2O (0.077 g, 94%), m.p. 123 ЊC (decomp.)
(Found: C, 50.65; H, 3.95; N, 1.9. C30H27AuCl2NOP requires
C, 50.3; H, 3.8; N, 1.95%); ΛM(1 × 10Ϫ4 mol dmϪ3, acetone)
16 S cm2 molϪ1; ν max/cmϪ1 (KBr) 316 (Au᎐Cl) and 295
(Au᎐Cl).
CCDC reference number 186/839.
[AuCl(pmp-C 1,N)(PPh3)]BF4 7b. Method (a). Sodium tetra-
fluoroborate (0.039 g, 0.354 mmol) was added to an acetone
(10 cm3) solution of complex 6b (0.051 g, 0.071 mmol). The
resulting suspension was stirred for 5 h and then evaporated to
dryness. The residue was extracted with dichloromethane and
the extract concentrated. Addition of hexane gave 7b (0.049 g,
92%), m.p. 161 ЊC (decomp.) (Found: C, 47.6; H, 3.5; N, 1.95.
C30H25AuBClF4NP requires C, 48.05; H, 3.35; N, 1.85%);
ΛM(1 × 10Ϫ3 mol dmϪ3, acetone) 139 S cm2 molϪ1; ν max/cmϪ1
(KBr) 1060 ([BF4]Ϫ) and 310 (Au᎐Cl).
Line shape analysis of [AuCl(pmp-C 1,N)(PPh3)]BF4 7b
Experimental line shapes for the methylene proton signals of
the pmp-C1,N moiety were measured in the temperature range
298–388 K, and matched against those calculated for different
exchange rate constants kobs, using the modified Bloch equa-
tion24 and Binsch’s25 computer program QUABEX. The
Arrhenius and Eyring equations were used to evaluate Ea, ∆H‡
and ∆S‡ from kobs
.
Method (b). To an acetonitrile (10 cm3) suspension of
complex 2b (0.100 g, 0.230 mmol) was added PPh3 (0.061 g,
0.232 mmol) and AgBF4 (0.046 g, 0.237 mmol). The resulting
mixture was stirred at room temperature and then evaporated
to dryness. The residue was extracted with acetone and the
extract concentrated. Addition of diethyl ether afforded 7b
(0.162 g, 94%). A similar procedure was reported by Cinellu
et al.7
Acknowledgements
The authors are grateful to Miss Mie Tomonou of Kyushu
University for her help with FAB mass measurement and also
thank Mr. Yushichiro Ohama of Nagasaki University for his
31P NMR measurement.
References
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J. Chem. Soc., Dalton Trans., 1998, Pages 791–796
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Received 1st September 1997; Paper 7/06354G
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J. Chem. Soc., Dalton Trans., 1998, Pages 791–796