Displacement of neutral nitrogen donors by chloride in AuCl 3(3R-py) (3R-py = meta-substituted pyridine): Comparison between meta- and para-substituted pyridines by kinetics and DFT calculations

Article abstract of DOI:10.1002/ejic.200700597

The kinetics of the process AuCl₃(3R-py) + Cl^- → AuCl₄^- + 3R-py (3R-py = one of a number of meta-substituted pyridines covering a wide range of basicity) have been studied in methanol at 25°C. The reactions obey the usual two-term rate law observed in the substitution reactions of square-planar complexes. The second-order rate constants, k₂, are very sensitive to the nature of the leaving group and plots of log k₂ against the pK_a of the conjugate acids are linear with the same slope of ca. -0.6 already found for para-substituted pyridines (4R-py). Until now the two groups of bases have been considered to behave in the same manner in their displacement from Au ^III and Pt^II by various nucleophiles but, on the contrary, the reactivity of the two classes of N donors is slightly different and follows the order: 4R-py > 3R-py. This kinetic result is explained on the basis of an energetic difference between the frontier orbitals of the AuCl ₃(3R-py) and AuCl₃(4R-py) derivatives. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.

Full text of DOI:10.1002/ejic.200700597

FULL PAPER
DOI: 10.1002/ejic.200700597
Displacement of Neutral Nitrogen Donors by Chloride in AuCl3(3R-py)
(3R-py = meta-Substituted Pyridine): Comparison between meta- and
para-Substituted Pyridines by Kinetics and DFT Calculations
Bruno Pitteri*[a] and Marco Bortoluzzi[a]
Keywords: Gold / Kinetics / Nitrogen donors / Reaction Mechanism / DFT
–
The kinetics of the process AuCl3(3R-py) + Cl– Ǟ AuCl4
+
been considered to behave in the same manner in their dis-
placement from AuIII and PtII by various nucleophiles but, on
the contrary, the reactivity of the two classes of N donors is
slightly different and follows the order: 4R-py Ͼ 3R-py. This
kinetic result is explained on the basis of an energetic differ-
ence between the frontier orbitals of the AuCl3(3R-py) and
AuCl3(4R-py) derivatives.
3R-py (3R-py = one of a number of meta-substituted pyr-
idines covering a wide range of basicity) have been studied
in methanol at 25 °C. The reactions obey the usual two-term
rate law observed in the substitution reactions of square-
planar complexes. The second-order rate constants, k2, are
very sensitive to the nature of the leaving group and plots of
logk2 against the pKa of the conjugate acids are linear with
the same slope of ca. –0.6 already found for para-substituted
pyridines (4R-py). Until now the two groups of bases have
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2007)
The k1 term is the first-order rate constant for the nucleo-
philic attack on the substrate by the solvent, whereas k2 is
the second-order rate constant for the nucleophilic attack
on the substrate by the nucleophile. The k2 constants are
remarkably influenced by the nature of R-py, indicating
that the discriminating ability of gold(III) and platinum(II)
complexes is good. In both the forward and reverse reac-
tions a linear free-energy relationship, log k2 = αpKa + con-
stant, occurs between the rate constant and the basicity of
R-py, that is the pKa of the conjugated acid [H(R-py)]+.
Steric retardation is observed for pyridines containing one
or two ortho groups (usually called hindered pyridines) and
these effects are in many cases approximately additive.
Moreover, we studied the kinetics of the reaction AuCl3(nu)
+ Cl– Ǟ AuCl4– + nu (nu = five-membered N-donor hetero-
cycles such as thiazole, oxazole, imidazole and their deriva-
tives)[4] and the results were compared, under the same ex-
perimental conditions, with studies where the leaving
groups are pyridines.[3] It was observed that the reactivity
depends not only upon the ligand basicity but also upon the
nature of the ligand in the order pyridines Ͼ five-membered
heterocycles.
Introduction
The chemical features of (pyridine)gold(III) complexes
are currently of interest from both a catalytic[1] and
mechanistic point of view: in particular, the reactivity of
gold(III)[2–5] in the reactions with N-donor bases has been
widely studied, mainly involving pyridine and substituted
pyridines (R-py) as entering or leaving groups. The same
types of reactions have also been studied for platinum(II)
derivatives[6–10] and it was observed that the substitution
reactions (1), (2) and (3) take place with an associative
mechanism, where the rate constants for the forward and
the reverse reactions obey the general relationship kobs = k1
+ k2[nucleophile], which is usual for nucleophilic substitu-
tions of planar four-coordinate d8 metal complexes.[11]
–
AuCl4 + R-py h AuCl3(R-py) + Cl–
(1)
[LPtCl]+ + R-py h [LPt(R-py)]2+ + Cl–
(2)
[L = 2,6-bis(methylsulfanylmethyl)pyridine,[5] bis(2-pyridylmethyl)
sulfide,[7] 2,2Ј:6Ј,2ЈЈ-terpyridine,[9] biacetylbis(N-methyl-N-phenyl)-
In recent work[5] involving reaction (1) we compared the
lability of three different groups of N donors: (I) 4-substi-
tuted pyridines; (II) 4-substituted pyridines with a more ex-
tended π-system; and (III) sp3 nitrogen-donor bases. The
first group includes pyridine, 4-bromopyridine, 4-chloropyr-
idine, 4-methylpyridine, 4-methoxypyridine, 4-aminopyr-
idine and 4-(dimethylamino)pyridine, while the second
group includes the derivatives of cyanopyridine, isonicotinic
acid, methyl isonicotinate and 4-acetylpyridine. The lability
oxazone[8]
]
LPtCl2 + R-py h [LPt(R-py)Cl]+ + Cl–
[L = 1,2-bis(phenylsulfanyl)ethane[6]
(3)
]
[a] Dipartimento di Chimica,Università “Cà Foscari” di Venezia,
Calle Larga S. Marta 2137, 30123 Venezia, Italy
E-mail: pitteri@unive.it
5138
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2007, 5138–5143

Displacement of Neutral Nitrogen Donors by Chloride in AuCl3(3R-py)
of these pyridines is considerably lower than that of the
Results and Discussion
third group of derivatives, i.e. the sp3 ligands piperidine,
cyclohexylamine and morpholine. Pyridines I and II obey
When a methanolic solution of the neutral AuCl3(3R-py)
the linear relationship logk2 = αpKa + constant with α ≈ substrate was allowed to react with an appropriate excess
–0.6, but the reactivity of the two groups differ by about of chloride, repetitive scanning of the spectrum in the re-
2.3 kJmol–1 in the order: pyridines I Ͼ pyridines II. These gion 240–360 nm showed that the reaction evolves with
differences were attributed to a ground-state stabilization time in a first-order fashion leading to the substitution of
due to the π back-donation from the filled orbitals of the the neutral base by a chloride ion. The presence of well-
metal atom to the antibonding orbitals of the pyridine li- maintained isosbestic points, whose position depends only
gands.
upon the spectrum of the starting compound, and the com-
In some kinetic studies involving reactions (1), (2) and parison of the final spectrum with that of original samples
(3)[2,3,7,8] meta-substituted pyridines (3R-py) were also con- of the substituted products at the same concentration,
sidered and their reactivity appeared similar to that of clearly indicate a single reaction stage. Addition of LiClO4
group I pyridines, but during our latest work regarding re- indicated that primary salt effects were absent and second-
action (1),[5] trying to study meta-substituted pyridines like ary effects were negligible; thus, no further attempt to main-
3-methylpyridine and 3-chloropyridine, we found kinetic tain a constant ionic strength was made. The reactions were
data that was not completely comparable with those of studied in the presence of 0.1 moldm–3 CH3SO3H. Prelimi-
para-substituted pyridines. In order to determine whether nary experiments showed that, at constant chloride concen-
these differences have a chemical meaning, the kinetics of tration, the rate of reaction was not dependent on the con-
the displacement of the nitrogen ligand by chloride from centration of acid over the range 0.02–0.2 moldm–3. The
AuCl3(3R-py) substrates in methanol at 25 °C are reported acid simply serves to protonate the released ligand, to pre-
and the results are compared with those of ref.[5] The dis- vent the reverse reaction and to force the reaction to com-
cussion is supported by ground-state DFT calculations per- pletion. All the reactions were studied in the presence of a
formed on the AuCl3(3R-py) and AuCl3(4R-py) derivatives sufficient excess of chloride over the substrate to provide
and the different reactivity of the coordinated meta- and pseudo-first-order conditions. It is to be noted that these
para-substituted pyridines is correlated with a slight, sys- experimental conditions are the same as those used in ref.[5]
tematic difference between the energies of the frontier orbit- The rate constants were determined in the usual way from
als of the corresponding gold(III) complexes.
the change in absorbance as a function of time at a conve-
Table 1. First-order rate constant, kobs, for the reaction AuCl3(3R-py) + Cl– Ǟ AuCl4 + 3R-py in methanol at 25 °C (0.1 moldm–3
–
CH3SO3H).
3R-py
[Cl–]/moldm–3
103 kobs/s–1[a]
3R-py
[Cl–]/moldm–3
103 kobs/s–1[a]
3-Chloropyridine
0.0005
0.0010
0.0015
0.0020
0.0025
27.7Ϯ0.1
29.6Ϯ0.1
31.5Ϯ0.1
36.5Ϯ0.2
38.3Ϯ0.1
3-phenylpyridine
0.001
0.002
0.003
0.004
0.005
1.93Ϯ0.03
2.28Ϯ0.01
2.81Ϯ0.01
3.27Ϯ0.02
3.76Ϯ0.04
3-Bromopyridine
3-Iodopyridine
3-Fluoropyridine
0.0005
0.0010
0.0015
0.0020
0.0025
17.0Ϯ0.1
20.2Ϯ0.2
23.0Ϯ0.1
28.0Ϯ0.2
30.5Ϯ0.1
3-hydroxymethylpyridine 0.001
1.05Ϯ0.01
1.26Ϯ0.01
1.60Ϯ0.02
1.94Ϯ0.01
2.22Ϯ0.03
0.002
0.003
0.004
0.005
0.0005
0.0010
0.0015
0.0020
0.0025
10.1Ϯ0.2
12.2Ϯ0.1
14.2Ϯ0.1
15.7Ϯ0.2
18.1Ϯ0.1
3-methoxypyridine
3-methylpyridine
0.001
0.002
0.003
0.004
0.005
1.39Ϯ0.01
1.64Ϯ0.02
2.05Ϯ0.03
2.35Ϯ0.04
2.68Ϯ0.03
0.0005
0.0010
0.0015
0.0020
0.0025
17.2Ϯ0.1
19.9Ϯ0.2
22.5Ϯ0.1
24.9Ϯ0.1
27.9Ϯ0.3
0.001
0.002
0.003
0.004
0.005
0.63Ϯ0.02
0.77Ϯ0.01
0.93Ϯ0.03
1.08Ϯ0.01
1.24Ϯ0.02
[a] The indicated errors were obtained from the nonlinear least-squares fit of the experimental data to Dt = Dϱ + (D0 – Dϱ)exp(–kobst)
(D0 = absorbance after mixing the reactants, Dϱ = absorbance at completion of reaction). Each experimental measurement was repeated
at least twice.
Eur. J. Inorg. Chem. 2007, 5138–5143
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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5139

B. Pitteri, M. Bortoluzzi
FULL PAPER
nient wavelength and the observed rate constants, kobs, are range (see ref.[5] for log k2 and pKa values of these nitrogen
collected in Table 1.
donors).
As depicted in Figure 1, a linear relationship, log k2 =
The observed rate constants, kobs, obey the general rela-
tionship kobs = k1 + k2[nucleophile], usually found for sub- αpKa + constant, is obeyed for both the meta-substituted
stitution in gold(III) complexes. The k1 terms, which refer (3R-py) and para-substituted (4R-py) pyridines, with α ≈
to the pathway in which the rate-determining step is the –0.6. Coordinated meta-substituted pyridines appear to be
nucleophilic attack of the solvent followed by the rapid en- slightly less reactive than the para-substituted ones, even if
try of chloride into the solvento complex,[12] are usually the difference between the reactivity of the two groups of
quite small and contribute little to the reactions. The k2 pyridines is quite small (∆ ≈ 0.18) and corresponds to about
terms are the second-order rate constants for the direct at- 1 kJmol–1. The chemical behaviour of the unsubstituted
tack of the nucleophile, Cl–, at the substrate and were deter- pyridine in its displacement by chloride from AuIII is com-
mined by a linear regression of the kobs values vs. the chlo- parable to that of the para-substituted pyridines.
ride concentration. As expected from previous studies on
To explain the experimental data obtained from the ki-
gold(III) substitution reactions,[2–5] the pseudo-first-order netic measurements, ground-state DFT B3PW91 calcula-
rate constant values, kobs, mainly depend upon the k2 val- tions were performed on AuCl3(py), AuCl3(3R-py) and
ues, which are reported in Table 2 together with the pKa AuCl3(4R-py) derivatives. Particular interest was devoted to
values of H[(3R-py)]+ taken from ref.[13]
the frontier orbitals of the gold complexes and Table 3 re-
In Figure 1 the plots of log k2 vs. pKa of the leaving 3R- ports the energy values of the HOMOs and LUMOs for all
py are shown, together with the data for the simple pyridine
and the para-substituted pyridines 4R-py in the same pKa
Table 3. Energy values of the frontier orbitals of the AuCl3(py),
AuCl3(3R-py) and AuCl3(4R-py) complexes.
Table 2. Second-order rate constants, k2, and pKa values of [H(3R-
R-py
HOMO [eV]
LUMO [eV]
–
py)]+ for the reaction AuCl3(3R-py) + Cl– Ǟ AuCl4 + 3R-py in
methanol at 25 °C (0.1 moldm–3 CH3SO3H).
AuCl3(4-methoxypyridine)
AuCl3(4-chloropyridine)
AuCl3(4-methylpyridine)
AuCl3(4-bromopyridine)
AuCl3(pyridine)
AuCl3(3-bromopyridine)
AuCl3(3-methoxypyridine)
AuCl3(3-chloropyridine)
AuCl3(3-methylpyridine)
AuCl3(3-iodopyridine)
AuCl3(3-fluoropyridine)
AuCl3(3-phenylpyridine)
–0.27672
–0.28573
–0.27872
–0.28541
–0.28183
–0.28584
–0.27946
–0.28629
–0.27759
–0.28525
–0.28619
–0.27953
–0.14997
–0.16001
–0.15209
–0.15964
–0.15564
–0.16068
–0.15314
–0.16108
–0.15129
–0.15992
–0.16087
–0.15325
–0.15274
3R-py
k2/dm3mols–1[a]
pKa of [H(3R-py)]+
AuCl3(3-chloropyridine)
AuCl3(3-bromopyridine)
AuCl3(3-iodopyridine)
AuCl3(3-fluoropyridine)
AuCl3(3-methylpyridine)
AuCl3(3-phenylpyridine)
5.6Ϯ0.6
6.9Ϯ0.4
3.9Ϯ0.1
5.28Ϯ0.09
0.153Ϯ0.002
0.46Ϯ0.02
2.84
2.84
3.25
2.97
5.52
4.80
5.00
4.91
AuCl3(3-hydroxymethylpyridine) 0.30Ϯ0.01
AuCl3(3-methoxypyridine) 0.33Ϯ0.01
[a] Errors were obtained from the linear regression of kobs values
vs. chloride concentration.
AuCl3(3-hydroxymethylpyridine) –0.27917
–
Figure 1. Plots of log k2 for the reaction AuCl3(R-py) + Cl– Ǟ AuCl4 + R-py against pKa of [H(R-py)]+: (᭡) R-py = pyridine; (᭺) R-
py = 4-chloropyridine, 4-methoxypyridine, 4-methylpyridine, 4-bromopyridine; (᭹) R-py = 3-chloropyridine, 3-bromopyridine, 3-fluoro-
pyridine, 3-iodopyridine, 3-methylpyridine, 3-phenylpyridine, 3-hydroxymethylpyridine, 3-methoxypyridine.
5140
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Eur. J. Inorg. Chem. 2007, 5138–5143

Displacement of Neutral Nitrogen Donors by Chloride in AuCl3(3R-py)
Figure 2. Plots of the (R-py) HOMO and LUMO energies against the pKa of [H(R-py)]+: (᭡) R-py = pyridine; (᭺) R-py = 4-chloropyr-
idine, 4-methoxypyridine, 4-methylpyridine, 4-bromopyridine; (᭹) R-py = 3-chloropyridine, 3-bromopyridine, 3-fluoropyridine, 3-iodopyr-
idine, 3-methylpyridine, 3-phenylpyridine, 3-hydroxymethylpyridine, 3-methoxypyridine.
the considered species, while in Figure 2 the plots of nucleophilic attack. Using a pseudo-Valence-Bond descrip-
HOMO and LUMO vs. pKa of the leaving 3R-py are tion to better explain this last conclusion regarding the re-
shown.
action studied, Cl– appears to interact with the gold(III)
Linear correlations between the frontier orbital energies complexes using a hybrid atomic orbital with a strong s
and pKa values were found, in particular for the para-sub- character and, consequently, an energy value lower than
stituted pyridine (4R-py) derivatives where the equations those of the LUMOs of the gold complexes, as depicted in
are E(HOMO) = 0.0032Ϯ0.0002 pKa – 0.2979Ϯ0.0008 Figure 3.
and E(LUMO) = 0.0036Ϯ0.0002 pKa – 0.1737Ϯ0.0008,
while for the meta-substituted pyridine (3R-py) complexes
the same equations are E(HOMO) = 0.0031Ϯ0.0001 pKa –
0.2957Ϯ0.0004 and E(LUMO) = 0.0038Ϯ0.0001 pKa
–
0.1719Ϯ0.0005. As depicted in Figure 2, the gradients of
the plots of the HOMO or LUMO energies vs. pKa are al-
most the same for both the 3R- and 4R-pyridines, while
there is a significant difference (about 0.002 eV) in their in-
tercepts. The computational results for the pyridine com-
plex AuCl3(py) are comparable to those of the AuCl3(4R-
py) derivatives, as was also the case with the chemical be-
haviour (see Figure 1). The comparison of Figure 1 and
Figure 2 appears to indicate a relation between the kinetic
and theoretical data, suggesting that the different reactivity
of the two groups of ligands considered, 3R-py and 4R-py,
could be ascribed to the different energies of the frontier
orbitals depicted in Figure 2.
In the reaction studied, i.e. the nucleophilic attack of Cl–
on AuCl3(R-py) and the consequent displacement of the
nitrogen ligand, a large role should be played by the lowest
unoccupied molecular orbitals of the gold complexes and
the filled atomic orbitals of the chloride ion. All the calcu-
lated LUMO energy values fall in the range –0.14997 eV
to –0.16108 eV and the AuCl3(3R-py) LUMOs are about
0.002 eV higher than those of the AuCl3(4R-py) complexes.
The three 3p atomic orbitals of Cl– have a calculated energy
Figure 3. Plot of the Cl– 3s and 3p AOs and the AuCl3(R-py) (R-
py = 3R-py and 4R-py) LUMO energy levels.
Concluding Remarks
The comparison of the results of the kinetic measure-
–
of –0.02709 eV, while the 3s atomic orbital corresponds to ments on the process AuCl3(R-py) + Cl– Ǟ AuCl4 + R-
an energy value of –0.47949 eV (see Figure 3). On suppos- py, where R-py are para-substituted pyridines 4R-py and
ing that the observed minor reactivity of the AuCl3(3R-py) meta-substituted pyridines 3R-py, enabled the observation
complexes, compared to that of the AuCl3(4R-py) deriva- of a slightly different behaviour for these two types of pyr-
tives, corresponds to a greater energy difference between the idines, the latter type being less reactive. Moreover, by
LUMOs of the AuCl3(3R-py) species and the interacting means of DFT calculations the kinetic results were corre-
Cl– atomic orbital, it is to be concluded that the 3s atomic lated to a small energy difference of the frontier orbitals of
orbital of the chloride ion plays an important role in the the AuCl3(4R-py) and AuCl3(3R-py) derivatives.
Eur. J. Inorg. Chem. 2007, 5138–5143
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B. Pitteri, M. Bortoluzzi
FULL PAPER
Table 4. Analytical data for the complexes (calcd. values in paren-
theses).
Experimental Section
Materials: Compound KAuCl4·2H2O was prepared from pure
gold foil (99.99%). Pure reagent-grade products [LiCl, LiClO4,
CH3SO3H (Aldrich)] were used without further purification. Pyr-
idines were recrystallized or distilled before use when necessary.
Anhydrous MeOH was obtained by distillation from Mg wires, but
traces of water did not appear to have any appreciable effect upon
the reactions. Acetone and dimethylformamide were pure reagent-
grade products (Aldrich and BDH, respectively).
Complex
C
H
N
Cl
AuCl3(3-fluoropyridine)
15.2
1.27
3.51
26.5
(15.0)
12.8
(13.0)
14.3
(14.4)
18.1
(18.2)
11.7
(1.01)
0.62
(0.87)
1.10
(0.97)
1.63
(1.78)
0.69
(3.50)
3.11
(3.04)
3.34
(3.36)
3.72
(3.53)
2.91
(26.6)
23.3
(23.1)
(34.2)
(34.0)
27.0
(26.8)
20.7
(20.9)
22.7
AuCl3(3-bromopyridine)
AuCl3(3-chloropyridine)
AuCl3(3-methylpyridine)
AuCl3(3-iodopyridine)
AuCl4(3-phenylpyridine)
Instruments: Electronic spectra and kinetic measurements were ob-
tained with a Perkin–Elmer Lambda 15 spectrophotometer. 1H
NMR spectra were obtained with Bruker Avance 300 and/or
Bruker AC 200 spectrometers. COSY, NOESY and homonuclear
decoupling experiments were performed to improve the characteri-
zation of the complexes. The conductivity of 1ϫ10–3 moldm–3
solutions in dimethylformamide at 25 °C was measured with a Ra-
diometer CDM 83 instrument. Elemental analyses were performed
by the Microanalytical Laboratory of the Faculty of Pharmaceuti-
cal Sciences of the University of Padua.
(11.8)
41.7
(0.79)
2.11
(2.76)
3.12
(41.9)
(1.93)
1.76
(2.97)
3.41
(22.6)
25.9
AuCl3(3-hydroxymethylpyridine) 17.3
(17.5)
17.6
(17.5)
(1.71)
1.51
(1.71)
(3.40)
3.44
(3.39)
(25.8)
26.0
(25.8)
AuCl3(3-methoxypyridine)
Preparation of the Complexes: Trichloro(3-methylpyridine)gold(III)
was first characterized by Cattalini and Tobe,[3] but the preparation
of the complexes of 3-fluoropyridine, 3-bromopyridine, 3-chloro-
pyridine, 3-iodopyridine, 3-phenylpyridine, 3-(hydroxymethyl)pyr-
idine and 3-methoxypyridine is described here for the first time. All
the complexes were prepared by the following method:
been brought to the reaction temperature (25 °C) in a thermostat-
ted cell in the spectrophotometer. The concentration of the entering
group was always large enough to provide pseudo-first-order condi-
tions. After preliminary repetitive scan experiments in the range
240–360 nm to search for isosbestic points and spectral changes,
KAuCl4·2H2O (0.415 g, 1 mmol) was dissolved in water (20 mL) the kinetics were studied by measuring the changing absorbance at
and an equimolar amount of the nitrogen-donor base, dissolved in
a small volume of water (3 mL), was added dropwise whilst stirring.
The yellow precipitate that formed almost immediately was filtered
off, washed three times with water (10 mL) and dried in vacuo. The
complexes were nonconductive in organic solvents. Yields were in
all cases nearly quantitative (Ͼ95%). Analytical and 1H NMR data
are collected in Tables 4 and 5, respectively.
a suitable wavelength (320 nm) as a function of time. Pseudo-first-
order rate constants (kobs [s–1]) were obtained either from the gradi-
ent of plots of log(Dt – Dϱ) vs. time or from a nonlinear least-
squares fit of the experimental data to Dt = Dϱ + (D0 – Dϱ)exp
(–kobst), where D0, Dϱ and kobs are the parameters that have to
be optimized (D0 = absorbance after mixing the reactants, Dϱ
=
absorbance at completion of reaction).
Kinetics: Reactions were initiated by adding a 0.015 moldm–3 ace-
tone solution (10–20 µL) of the substrate complex, AuCl3(3R-py),
to a methanolic solution of chloride ion (3 mL) that had previously
Computational Details: The computational geometry optimizations
of the AuCl3(3R-py) and AuCl3(4R-py) complexes were performed
in vacuo using the hybrid DFT B3PW91 method[14] without sym-
1
Table 5. H NMR spectroscopic data for the complexes.
Complex
1H NMR, (CD3)2CO, 298 K
3
4
3
AuCl3(3-fluoropyridine)
δ = 9.30 (dd, 1 H, JH,F = 2.8 Hz, JH,H = 2.2 Hz, 2-H), 9.10 (d, 1 H, JH,H = 5.8 Hz, 6-H), 8.39
3
3
4
3
(ddd, 1 H, JH,H = 8.4 Hz, JH,F = 8.2 Hz, JH,H = 2.2 Hz, 4-H), 8.16 (ddd, 1 H, JH,H = 5.8 Hz,
3JH,H = 8.4 Hz, JH,F = 5.0 Hz, 5-H) ppm
3
4
3
4
AuCl3(3-bromopyridine)
AuCl3(3-chloropyridine)
δ = 9.42 (d, 1 H, JH,H = 2.1 Hz, 2-H), 9.21 (dd, 1 H, JH,H = 6.0 Hz, JH,H = 1.0 Hz, 6-H), 8.67
3
4
4
3
(ddd, 1 H, JH,H = 8.4 Hz, JH,H = 2.1 Hz, JH,H = 1.0 Hz, 4-H), 8.03 (dd, 1 H, JH,H = 6.0 Hz,
3JH,H = 8.4 Hz, 5-H) ppm
4
3
4
δ = 9.34 (d, 1 H, JH,H = 2.3 Hz, 2-H), 9.17 (dd, 1 H, JH,H = 6.0 Hz, JH,H = 1.1 Hz, 6-H), 8.55
3
4
4
3
(ddd, 1 H, JH,H = 8.3 Hz, JH,H = 2.3 Hz, JH,H = 1.1 Hz, 4-H), 8.09 (dd, 1 H, JH,H = 6.0 Hz,
3JH,H = 8.3 Hz, 5-H) ppm
3
3
AuCl3(3-methylpyridine)
AuCl3(3-iodopyridine)
δ = 8.96 (s, 1 H, 2-H), 8.93 (d, 1 H, JH,H = 6.0 Hz, 6-H), 8.24 (d, 1 H, JH,H = 7.9 Hz, 4-H),
7.88 (dd, 1 H, JH,H = 6.0 Hz, JH,H = 7.9 Hz, 5-H), 2.58 (s, 3 H, CH3) ppm
δ = 9.50 (d, 1 H, JH,H = 1.8 Hz, 2-H), 9.20 (dd, 1 H, JH,H = 5.8 Hz, JH,H = 1.0 Hz, 6-H), 8.79
3
3
4
3
4
3
4
4
3
(ddd, 1 H, JH,H = 8.4 Hz, JH,H = 1.8 Hz, JH,H = 1.0 Hz, 4-H), 7.87 (dd, 1 H, JH,H = 5.8 Hz,
3JH,H = 8.4 Hz, 5-H) ppm
4
3
4
AuCl4(3-phenylpyridine)
δ = 9.50 (d, 1 H, JH,H = 2.1 Hz, 2-H), 9.11 (dd, 1 H, JH,H = 6.0 Hz, JH,H = 1.0 Hz, 6-H), 8.69
3
4
4
3
(ddd, 1 H, JH,H = 6.2 Hz, JH,H = 2.1 Hz, JH,H = 1.0 Hz, 4-H), 8.09 (dd, 1 H, JH,H = 6.0 Hz,
3JH,H = 6.2 Hz, 5-H), 7.97–7.79 (m, 3 H, Ph), 7.75–7.52 (m, 2 H, Ph) ppm
3
3
AuCl3(3-hydroxymethylpyridine)
AuCl3(3-methoxypyridine)
δ = 9.06 (s, 1 H, 2-H), 8.99 (d, 1 H, JH,H = 6.0 Hz, 6-H), 8.35 (d, 1 H, JH,H = 7.9 Hz, 4-H),
7.95 (dd, 1 H, JH,H = 6.0 Hz, JH,H = 7.9 Hz, 5-H), 5.17 (br. s, 1 H, OH), 4.90 (s, 2 H, CH2)
3
3
ppm
4
3
4
δ = 8.90 (d, 1 H, JH,H = 2.4 Hz, 2-H), 8.71 (dd, 1 H, JH,H = 5.4 Hz, JH,H = 1.0 Hz, 6-H), 7.99
3
4
4
3
(ddd, 1 H, JH,H = 8.2 Hz, JH,H = 2.4 Hz, JH,H = 1.0 Hz, 4-H), 7.92 (dd, 1 H, JH,H = 8.2 Hz,
3JH,H = 5.4 Hz, 5-H), 4.09 (s, 3 H, CH3) ppm
5142
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Eur. J. Inorg. Chem. 2007, 5138–5143

Displacement of Neutral Nitrogen Donors by Chloride in AuCl3(3R-py)
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Acknowledgments
We sincerely thank the Ca’ Foscari University of Venice for finan-
cial support (Ateneo fund 2006).
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Received: June 8, 2007
Published Online: September 18, 2007
Eur. J. Inorg. Chem. 2007, 5138–5143
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
5143