Gold(III) derivatives with C(4)-aurated 1-phenylpyrazole

Article abstract of DOI:10.1016/S0022-328X(98)00808-0

The reaction of 1-phenylpyrazole (HL), with gold(III) chloride has been studied. Besides a 1:1 adduct [Au(HL)Cl₃] 1, where the ligand is bonded through the nitrogen atom, several C(4) aurated species have been isolated. Thus treatment of [AuCl₃]₂ with HL in dichloromethane solution affords a complex, [Au(L)Cl₂^.HCl]_n, 2, where the gold atom is bonded to the 4-carbon atom of the pyrazole ligand. Deprotonation of complex 2 by means of the not coordinating base 1,8-bis(dimethylamino)naphthalene (proton sponge), B, affords the salt [BH][Au(L)Cl₃], 3, whereas reaction of 2 with 3,5-Me₂py and PPh₃ (molar ratio 1:2) gives the neutral species trans-[Au(L)(3,5-Me₂py)Cl₂], 4, and cis-[Au(L)(PPh₃)Cl₂], 5, respectively. The structure of compound 4 solved by X-ray diffraction, unambiguously shows the anionic ligand L bonded to the gold ion through the C4 atom. Alternatively, compounds 4 and 5 can be obtained in two steps, i.e. deprotonation of 2 with NaOH to give [Au(L)Cl₂]_n, 6, and reaction of 6 with 3,5-Me₂py and PPh₃, respectively. The new species were characterized by elemental analyses, conductivity measurements, IR, NMR and FAB-MS spectroscopy.

Full text of DOI:10.1016/S0022-328X(98)00808-0

Journal of Organometallic Chemistry 568 (1998) 225–232
Gold(III) derivatives with C(4)-aurated 1-phenylpyrazole
Giovanni Minghetti a,*, Maria Agostina Cinellu a, Maria Vittoria Pinna a, Sergio Stoccoro a,
Antonio Zucca a, Mario Manassero b
a Dipartimento di Chimica, Uni6ersita` di Sassari, 6ia Vienna 2, 07100 Sassari, Italy
b Dipartimento di Chimica Strutturale e Stereochimica Inorganica, Uni6ersita` di Milano, Centro CNR, 6ia Venezian 21, 20133 Milano, Italy
Received 5 May 1998
Abstract
The reaction of 1-phenylpyrazole (HL), with gold(III) chloride has been studied. Besides a 1:1 adduct [Au(HL)Cl3] 1, where the
ligand is bonded through the nitrogen atom, several C(4) aurated species have been isolated. Thus treatment of [AuCl3]2 with HL
in dichloromethane solution affords a complex, [Au(L)Cl2. HCl]n, 2, where the gold atom is bonded to the 4-carbon atom of the
pyrazole ligand. Deprotonation of complex 2 by means of the not coordinating base 1,8-bis(dimethylamino)naphthalene (proton
sponge), B, affords the salt [BH][Au(L)Cl3], 3, whereas reaction of 2 with 3,5-Me2py and PPh3 (molar ratio 1:2) gives the neutral
species trans-[Au(L)(3,5-Me2py)Cl2], 4, and cis-[Au(L)(PPh3)Cl2], 5, respectively. The structure of compound 4 solved by X-ray
diffraction, unambiguously shows the anionic ligand L bonded to the gold ion through the C4 atom. Alternatively, compounds
4 and 5 can be obtained in two steps, i.e. deprotonation of 2 with NaOH to give [Au(L)Cl2]n, 6, and reaction of 6 with 3,5-Me2py
and PPh3, respectively. The new species were characterized by elemental analyses, conductivity measurements, IR, NMR and
FAB-MS spectroscopy. © 1998 Elsevier Science S.A. All rights reserved.
Keywords: Gold(III); 1-Phenylpyrazole; Auration
1. Introduction
(L=neutral ligand) [3]. At variance, at least as far as
we know, the reactivity with gold(III) has not been
studied. 1-Phenylpyrazole is known to undergo substiu-
tion at the C4 atom of the heterocyclic ring by elec-
trophiles such as HgCl2 and Hg(OAc)2 [4] and we
wondered whether gold(III) might give ortho-metallated
derivatives or C(4) substituted species.
Recently we have described gold(III) ortho-metal-
lated derivatives arising from 2-benzyl pyridines [1] and
6-benzyl-2,2%-bipyridines [2] and observed some analo-
gies in the behaviour of these ligands towards gold(III)
and palladium(II). It was reported many years ago by
Trofimenko that 1-phenylpyrazole reacts with palladiu-
m(II) to give ortho-metallated derivatives
Here we report the synthesis of an adduct
[Au(HL)Cl3], where the ligand is N-bonded, and several
C(4) aurated derivatives, including an organometallic
* Corresponding author. Fax: +39 79 229559; e-mail:
mingh@ssmain.uniss.it
0022-328X/98/$19.00 © 1998 Elsevier Science S.A. All rights reserved.
PII S0022-328X(98)00808-0

226
G. Minghetti et al. / Journal of Organometallic Chemistry 568 (1998) 225–232
Table 1
Proton NMR dataa
Compound
Solvent
CDCl3
H(3)+H(5) H(4) Phenyl H(4%)
H(3%) H(2%)
Other
HLb
7.72, 7.87
6.46
6.51
6.89
7.2–7.6
7.31, 7.50, 7.86
7.60–7.71
HLc
(CD3)2CO 7.70, 8.32
[Au(HL)Cl3] 1
CDCl3
8.02, 8.03
[Au(L)Cl.2HCl]n
2
(CD3)2CO 8.55, 8.60d
(CD3)2CO 7.69, 8.08
7.68–7.96
7.25, 7.46, 7.81
K[Au(L)Cl3] 3a
[BH][Au(L)Cl3] 3be
CDCl3
7.84, 8.04
7.86, 8.05
7.23, 7.41, 7.80 BH: 3.33 (d, 12H, JHH 2.7, 4Me), 7.96 [d, 2H,
H(2) and H(7)], 7.68 [t, 2H, H(3) and H(6)], 7.67
(d, 2H, H(4) and H(5)], 19.03 (s, 1H, NH)
3
[Au(L)(3,5-Me2py)Cl2] 4f
CDCl3
7.27 7.44 7.71
3,5-Me2py: 2.45 (s, 6H, 2Me), 7.63 [s (broad), 1H,
H(4)], 8.56 [s, 2H, H(2) and H(6)]
PPh3: g
[Au(L)(PPh3)Cl2] 5a
{Au(L)[P(4-MeC6H4)3]Cl2} 5b
[Au(L)Cl2]n
CDCl3
CDCl3
CDCl3
7.07, 7.08
6.90, 7.18
7.99, 8.02
g
h
P(4-MeC6H4)3: 2.33 (s, 9H, 3Me), h
6
7.26–7.63
a Spectra recorded at room temperature, chemical shifts in ppm from internal SiMe4.
b Data from Katritzky and Rees [6]; J3–4, 1.9; J4–5, 2.5; and J3–5, 0.7 Hz.
c This work.
d J3–5 0.7 Hz.
e B=1,8-bis(dimethylamino)naphtalene
f Assignments based on NOE difference experiment.
g C6H5–N(1)+P(C6H5)3 7.06–7.64 [m, 22H].
h C6H5–N(1)+P(4-MeC6H4)3 7.21–7.49 [m, 19 H].
anion [Au(L)Cl3]−. No ortho-metallated species has
been observed under various experimental conditions.
with respect to H(3) and (5), is missing. Other signifi-
cant differences between 1 and 2 are observed in the IR
spectra: indeed, in complex 2, four strong or very
strong bands are observed in the range 365–270 cm−1
,
2. Results and discussion
where the stretching modes of the Au–Cl vibrations are
usually observed. In addition, the spectrum of 2 ex-
hibits a typical pattern in the range 3150–2760 cm−1
(Nujol mull) indicative of the presence of N–H bonds.
Attempts to attain C,N cyclometallation of 1-
phenylpyrazole (HL) from both Na[AuCl4]·2H2O and
AuCl3 ·xH2O failed, in spite of the different approaches
which were tested. Likewise, unsuccessful were the at-
tempts to promote cyclometallation on the adduct
[Au(HL)Cl3], 1, which can be isolated by reaction of
Na[AuCl4]·2H2O with HL in water at room tem-
perature (yield ca. 75%). According to IR and con-
ductivity data, compound 1 is likely to be a mononu-
clear neutral species, analogous to other adducts with
nitrogen heterocycles previously reported [5]. Neverthe-
less a not negligible ionization occurs in acetone solu-
tion.
1
Taken together, the H-NMR and IR spectra suggest
that electrophilic attack of gold at the 4-carbon atom
and protonation of the nitrogen atom has occurred.
Either dimeric (oligomeric), A, or monomeric, B, spe-
cies can be considered.
An unexpected result was obtained when anhydrous
AuCl3 (as obtained from AuCl3 ·xH2O and SOCl2) was
reacted with HL in dichloromethane. After prolonged
stirring at room temperature (ca. 24 h) a cream solid
was collected and recrystallized, compound 2. The ‘em-
pirical’ formula which best fits the analytical values
(C,H,N,Cl; see Section 3) is C9H8AuCl3N2, i.e. an
isomer of compound 1. A striking evidence for the
Although conductivity measurements, which show
complex 2 to be partially dissociated, at least in acetone
solution, point to A as the more probable species, the
reactivity of compound 2 does not allow to rule out B
completely. In the latter hypothesis the complex pattern
exhibited in the w(Au–Cl) region of the IR spectrum
might be explained taking into account a lowering of
symmetry due to intra- or intermolecular hydrogen
bonds. In order to get an insight in the nature of
1
difference between 1 and 2, is given by the H-NMR
spectrum (Table 1): in the spectrum of 2 the resonance
assigned to H(4) of the pyrazole ring [6], at higher field

G. Minghetti et al. / Journal of Organometallic Chemistry 568 (1998) 225–232
227
Scheme 1. Syntheses of the metallated species 2–6.
compound 2, the reactivity with different bases has been
studied (Scheme 1).
1:1 electrolytes in acetone solution. The FAB-MS spec-
tra (negative ion) confirm the anionic nature of the gold
complexes. In the IR spectra both 3a and 3b show two
Deprotonation of 2 was tried first with strong bases
such as aqueous NaOH or KOH solutions. Compound
6 obtained in these conditions analyses for [Au(L)Cl2].
At variance with 2, the pattern associated with N–H
stretching vibrations is absent in the IR spectrum of 6
confirming deprotonation. The 1H-NMR spectrum
gives evidence for a C(4) aurated ligand.
absorptions in the region 370–360 and 300–295 cm−1
,
respectively, in agreement with a structure having chlo-
ride ions trans to ligands with different trans-influence.
1
In the H-NMR spectra of 3b a signal at very low field,
l 19.03, is assignable to the NH resonance of the
protonated proton sponge; the CH3 signal is split into a
doublet (3JHH=2.7 Hz).
The reaction of compound 6 with two electron donors
such as 3,5-Me2py and PR3 (R=C6H5, 4-MeC6H4) was
found to give the neutral adducts 4 and 5 (a, R=C6H5;
b, R=4-MeC6H4), respectively. The same species 4 and
5 can be obtained from the protonated complex 2
provided an excess of ligand (molar ratio Au:L=1:2) is
used.
Dimers (or oligomers), with bridging chlorides or
bridging C,N bonded pyrazoles can be envisaged.
Afterwards it was found that compound 6 can be
obtained also in the absence of an added base, by
refluxing an aqueous suspension of complex 2. A quan-
titative determination of chlorine on a sample obtained
in this way, identical with that obtained by reaction with
NaOH, confirms that no substitution of hydroxide for
chloride occurs.
In the presence of solid K2CO3 or of a not coordinat-
ing base such as 1,8-bis(dimethylamino)naphthalene
(proton sponge) the deprotonation of 2 goes a different
way to give salts of the complex anion 3.
A trans- and cis- geometry is assigned to compounds
4 and 5, respectively, on the basis of the IR spectra
which show one (complex 4) and two (complex 5)
Au–Cl bands in the region 370–300 cm−1
.
The cis arrangement in complex 5 is likely to be
dictated by the need to avoid an arrangement with two
ligands having high trans-influence, trans to each other.
Complexes 3a and 3b are air and moisture stable,
The structure of complex 4 in the solid state has been
both in the solid state and in solution; they behave as
solved by X-ray diffraction. It consists of the packing of

228
G. Minghetti et al. / Journal of Organometallic Chemistry 568 (1998) 225–232
˚
Table 2
Cl(1)
distance,
2.282(1)
A,
found
in
˚
Selected bond distances (A) and angles (°) with estimated S.D.’s in
parentheses for [Au(3,5-Me2py)(L)C12], compound 4
[Au{NC5H4(CMe2C6H4)-2}Cl2] [1]. The Au–C(4) bond
˚
length, 2.006(4) A, is also normal, and can be compared
˚
with the Au–C distance, 2.009(4) A, found in cation
Au–C11
Au–N3
N1–N2
C3–C4
C5–N1
2.283(1)
2.124(3)
1.350(5)
l.397(7)
1.357(5)
Au–C12
Au–C4
N2–C3
C4–C5
N1–C6
2.278(1)
2.006(4)
1.344(7)
1.345(6)
1.432(5)
[Au{N2C10H7(CMe2C6H4)-6}Cl]+ (7) [2]. The Au–N(3)
˚
bond length, 2.124(3) A, is long but typical for an
Au–N bond trans to an atom having high trans-influ-
ence: compare for instance Au–N(1), 2.121(5) A, in
˚
cation 7, where the Au–N(1) bond is trans to a phenyl
carbon atom.
C11–Au–C12
C11–Au–C4
C12–Au–C4
Au–C4–C3
N2–N1–C5
N2–C3–C4
C4–C5–N1
C5–N1–C6
178.9(1)
89.4(1)
89.9(1)
123.8(3)
111.5(3)
111.6(4)
108.0(4)
129.7(4)
C11–Au–N3
C12–Au–N3
N3–Au–C4
Au–C4–C5
N1–N2–C3
C3–C4–C5
N2–N1–C6
89.7(1)
91.0(1)
178.7(1)
131.3(3)
104.0(4)
104.9(4)
118.7(3)
Bond lengths and angles within the pyrazole moiety
compare well with the corresponding average values
reported by F. Bonati in 1989 for a series of substituted
pyrazoles [7]: the only large difference is in the C(4)–
˚
˚
C(5) distance, 1.345(6) A here, and 1.379 A in Bonati’s
paper. (The values reported by Bonati are the averages
of a large number of crystal structure determinations
and estimated S.D. are not given). Bonati found out
various trends in the internal and external angles of
pyrazoles and pyrazole derivatives. In particular, he
observed that in N(1)-substituted pyrazoles the N(2)–
N(1)–R angle (119.1° in Bonati’s paper, 118.7(3)° here)
is always much smaller than the C(5)–N(1)–R one
(129.0 and 129.7(4)°, respectively), and explained this
trend with a higher amount of p character in the N(1)
sp2 hybrid orbital pointing towards the more elec-
tronegative N(2) atom with respect to the N(1) sp2
orbital pointing towards C(5). He also found out that
in C(4)-substituted pyrazoles the C(3)–C(4)–R and
trans-[Au(L)(3,5-Me2py)Cl2] molecules with no unusual
van der Waals contacts. Principal bond lengths and
angles are reported in Table 2. An ORTEP view of the
molecule is shown in Fig. 1. The coordination around
the gold atom is square planar, with a very slight
pyramidal distortion: thus, atoms Cl(1), Cl(2), N(3) and
C(4) are strictly coplanar, with the gold atom lying
˚
0.016(1) A above their best plane. The Au–Cl(1) and
˚
Au–Cl(2) bond lengths, 2.283(1) and 2.278(1) A, re-
spectively, are normal and can be compared with the
average Au–Cl distance, 2.275 A, found in
[Au{N2C10H7(CHMePh)-6}Cl3] [2], and with the Au–
˚
Fig. 1. A perspective view of compound 4. Thermal ellipsoids are drawn at the 30% probability level.

G. Minghetti et al. / Journal of Organometallic Chemistry 568 (1998) 225–232
229
Fig. 2. A projection down the b-axis of the packing in compound 4, showing the quasi-parallel stacking of phenylpirazole and 3,5-1utidine
moieties.
C(5)–C(4)–R angles are usually very similar (126.9 and
127.2°, respectively). At variance, in the present C(4)-
metallated phenylpyrazole the C(3)–C(4)–Au angle,
123.8(3)°, is much smaller than the C(5)–C(4)–Au one,
131.3(3)°, and in the absence of more evidence on other
C(4)-metallated pyrazoles, we believe that it can be
ascribed to packing forces. Actually, the crystal packing
is dictated by the quasi-parallel stacking of alternating
3,5-lutidine (3,5-Me2py) and phenylpyrazole moieties
belonging to different molecules, as shown in Fig. 2.
Because the stacking planes are not exactly parallel, we
cannot refer to their distance. Instead, we report the
shortest intermolecular contacts, which are C(12)···C(5%)
3.502(6) A, and C(14)···C(6%%) 3.473(6) A, where primed
and double primed atoms are obtained through the
symmetry operations −x, 1/2+y, 1/2−z, and −x,
−y, −z, respectively.
Within a single molecule, each of the three (het-
ero)aromatic rings is strictly planar, and the dihedral
angles between their best planes are: pyrazole-phenyl
3.5(4)°, pyrazole-lutidine 3.3(5)°, phenyl-lutidine
6.2(3)°. The dihedral angles of the metal coordination
best plane with the three (hetero)aromatic rings are
50.4(2), 50.6(1), and 52.9(1)° for pyrazole, phenyl, and
lutidine, respectively.
3. Experimental
All reactions were carried out in the dark. The sol-
1
vents were dried and distilled before use. H-, 31P{1H}-
and 13C{1H}-NMR spectra were recorded with a
Varian VXR 300 spectrometer operating at 299.9 (1H),
121.4 (31P) and 75.4 MHz (13C), respectively. Chemical
shifts are given in ppm relative to internal TMS (1H
and 13C) and external 85% H3PO4 (31P). IR spectra
were recorded with Perkin Elmer spectrophotometers
983 and 1310 using Nujol mulls. Mass spectra were
obtained with a VG 7070 instrument operating under
FAB conditions, with 3-nitrobenzyl alcohol as support-
ing matrix. Conductivity measurements were obtained
using a Philips PW 9505 conductimeter at 25°C. Ele-
mental analyses were performed with a Perkin-Elmer
elemental analyzer 240 B by Mr A. Canu (Diparti-
mento di Chimica, Universita` di Sassari) [C,H,N] and
Mikroanalytisches Labor Pascher (Germany) [Cl].
˚
˚

230
G. Minghetti et al. / Journal of Organometallic Chemistry 568 (1998) 225–232
3.1. Synthesis of compounds 1–6
Anal. calc. for C23H26AuCl3N4: C, 41.74; H, 3.96; N,
8.47%. Lm (5.4×10−4 M, acetone): 119.5 V−1 cm2
mol−1, Lm (5×10−4 M, dichloromethane): 29 V−1
cm2 mol−1. IR (Nujol, cm−1) w: 1593 m, 691 m, 363 s,
295 s. FAB mass spectrum (m/z): 215 [M+], 445 [M−],
375 [M–2Cl].
3.1.1. [Au(HL)Cl3] (1)
To an aqueous solution of Na[AuCl4]·2H2O, (397.8
mg, 1.49 mmol) were added 0.20 cm3 of HL (d=1.091
g.cm−3, 97%, 1.47 mmol), the resulting yellow-green
suspension was stirred for 5 days at room temperature.
The solid product was filtered off and then extracted
with benzene. The filtered solution was concentrated
under vacuum to give the analytical sample. Yield 75%,
m.p. 225°C (dec.). Anal. found: C, 24.34; H, 2.01; N,
6.01%. Anal. calc. for C9H8AuCl3N2: C, 24.16; H, 1.80;
N, 6.26%. Lm (5×10−4 M, acetone): 46 V−1 cm2
mol−1, (5×10−4 M, dichloromethane): 1.4 V−1 cm2
mol−1. IR (Nujol, cm−1) w: 1591 m, 693 s, 380 m, 366
s. FAB mass spectrum (m/z): 341 [(HL)Au+].
3.1.5. [Au(L)(3,5-Me2py)Cl2] (4)
(1) Addition of 3,5-Me2py (0.04 cm3, 0.34 mmol) to a
suspension in dichloromethane of complex 2 (71 mg,
0.08 mmol) gave a yellow solution which was stirred for
2 h at room temperature. After this period it was
concentrated to a small volume and diethyl ether was
added to give a yellow solid. Recrystallization from
dichloromethane/diethyl ether gave the analytical sam-
ple. Yield 72%.
(2) To a solution of 6 (44 mg, 0.053 mmol) in
dichloromethane, 3,5-Me2py (0.012 cm3, 0.103 mmol)
was added. The resulting yellow solution was stirred for
2 h and then concentrated to a small volume. Addition
of diethyl ether gave a yellow precipitate of 4. Yield
51%. m.p. 184°C. Anal. found: C, 37.14; H, 3.29; N,
7.77%. Anal. calc. for C16H16AuCl2N3: C, 37.08; H,
3.11; N, 8.11%. IR (Nujol, cm−1) w: 1593 s, 688 s, 368
s. FAB mass spectrum (m/z): 517 [M+], 481 [M–HCl],
410 [M–L%] (L%=3,5-Me2py). 13C-NMR (CDCl3) l:
18.5 (CH3), 119.0, 126.2, 126.4, 129.3, 141.6, 141.9 and
146.5 (10 C, aromatic CH), 97.9, 136.1, and 140.2 (4 C,
aromatic C).
3.1.2. [Au(L)Cl.2HCl]n (n=2) (2)
To a solution of [AuCl3]2 (352 mg, 0.58 mmol) in
dichloromethane were added 0.16 cm3 of HL (d=1.091
g.cm−3, 97%, 1.17 mmol), the resulting yellow solution
was stirred for 24 h at room temperature. During this
period a pale yellow precipitate was formed. It was
filtered off and recrystallyzed from acetone/diethyl
ether to give the analytical sample (380 mg) as a cream
solid. Yield 73%, m.p. 198°C (dec.). Anal. found: C,
24.27; H, 1.93; N, 6.02; Cl, 23.3%. Anal. calc. for
C18H16Au2Cl6N4: C, 24.16; H, 1.80; N, 6.26; Cl,
23.77%. Lm (5×10−4 M, acetone): 85 V−1 cm2 mol−1
.
IR (Nujol, cm−1) w: 3150 s, 3080 s, 3040 s, 2800 s, 2760
s, 1590 m, 1530 m, 690 s, 365 vs, 335 s, 300 vs, 270 s.
FAB mass spectrum (m/z): 822 [M–2Cl], 375 [LAuCl],
341 [(HL)Au].
3.1.6. [Au(L)(PPh3)Cl2] (5a)
(1) To a suspension of 2 (87.3 mg, 0.097 mmol) in
dichloromethane, PPh3 (51.7 mg, 0.197 mmol) was
added. The resulting yellow solution was stirred for 1 h,
concentrated to a small volume and added with diethyl
ether to give a yellow precipitate of 5a (104 mg), yield
80%.
(2) To a solution of 6 (61.5 mg, 0.075 mmol) in
dichloromethane was added PPh3 (39.8 mg, 0.150
mmol). The resulting solution was stirred for 1h, con-
centrated to a small volume and added with diethyl
ether to give 5a as a yellow solid. Yield 72%, m.p.
118°C. Anal. found: C, 48.88; H, 3.44; N, 4.35%. Anal.
calc. for C27H22PAuCl2N2: C, 48.16; H, 3.29; N, 4.16%.
Lm (6.2×10−4 M, dichloromethane): 6.45 V−1 cm2
mol−1. IR (Nujol, cm−1) w: 1598 m, 1100 s, 690 vs, 319
vs, 302 s. FAB mass spectrum (m/z): 673 [M+], 637
[M–HCl], 602 [M–H–2Cl], 459 [AuPPh3]. 31P-NMR
(CDCl3) l: 34.3.
3.1.3. [Au(L)Cl3]K (3a)
To a solution of complex 2 (47 mg, 0.052 mmol) in
acetone, solid K2CO3. was added. The mixture was
stirred for 15 h at room temperature. The filtered
solution was concentrated to a small volume and di-
ethyl ether was added to give a yellow precipitate of 3a.
Recrystallization from acetone/diethyl ether gave the
analytical sample. Yield 78%, m.p. 172°C. Anal. found:
C, 23.09; H, 1.87; N, 5.80%. Anal. calc. for
C9H7AuCl3KN2: C, 22.26; H, 1.45; N, 5.77%. Lm (5×
10−4 M, acetone): 84.6 V−1 cm2 mol−1. IR (Nujol,
cm−1) w: 1593 m, 690 m, 370 m, 300 m. FAB mass
spectrum (m/z): 445 [M−], 375 [M–2Cl].
3.1.4. [Au(L)Cl3][BH] (3b)
To a solution of complex 2 (172 mg, 0.19 mmol) in
acetone, 83.7 mg (0.39 mmol) of proton sponge (B) was
added and the resulting solution was stirred for 5 h at
room temperature and then concentrated to a small
volume. Addition of diethyl ether gave the analytical
sample as a yellow solid (203 mg), yield 80%, m.p.
102°C (dec.). Anal. found: C, 41.70; H, 3.87; N, 8.10%.
3.1.7. [Au(L){P(4-MeC6H4)3}Cl2] (5b)
To a suspension of 2 (59.3 mg, 0.07 mmol) in
dichloromethane, P(4-MeC6H4)3 (43 mg, 0.138 mmol)
was added. The resulting yellow solution was stirred for
1 h and then concentrated to a small volume: addition
of diethyl ether gave a yellow precipitate of 5b. Yield

G. Minghetti et al. / Journal of Organometallic Chemistry 568 (1998) 225–232
231
74%, m.p. 123°C. Anal. found: C, 50.63; H, 4.41;
N,3.92%. Anal. calc. for C30H28PAuCl2N2: C, 50.37; H,
3.94; N, 3.92%. Lm (6.4×10−4 M, dichloromethane):
9.40 V−1 cm2 mol−1. IR (Nujol, cm−1) w: 1596 s, 1097
s, 693 m, 325 s, 304 vs. 31P-NMR (CDCl3) l: 33.7.
w and 249 w. FAB mass spectrum (m/z): 821 [MH+],
750 [M–2Cl], 605 [M–L–2HCl], 340 [LAu].
3.2. Crystallography
Crystal data and other experimental details are sum-
marized in Table 3. The diffraction experiment was
carried out on a Siemens SMART CCD area-detector
diffractometer at room temperature using Mo–Kh radi-
3.1.8. [Au(L)Cl2]2 (6)
(1) To a solution of 2 (106 mg, 0.118 mmol) in
acetone, an aqueous solution of NaOH (9.1 mg, 0.227
mmol) was added. The resulting solution was stirred for
6 h and then evaporated to dryness. The residue was
taken up with dichlorometane, filtered and concen-
trated to a small volume: addition of diethyl ether gave
a pale yellow compound. Yield 48%.
˚
ation (u=0.71073 A) with
a
graphite crystal
monochromator in the incident beam and the generator
working at 50 kV and 35 mA. Cell parameters and
orientation matrix were obtained from the least-squares
refinement of 88 reflections measured in three different
sets of 15 frames each, in the range 2Bq B23°. At the
end of data collection the first 50 frames, containing
277 reflections, were recollected to have a monitoring of
crystal decay, which was not observed, so that no
time-decay correction was needed. The 2500 collected
frames were processed with the software SAINT [8],
and an empirical absorption correction was applied
(SADABS [9]) to the 15457 collected reflections, 4144
of which are unique with Rint=0.050 (Rint=ꢀꢁF20−
F2meanꢁ/ꢀF20). The calculations were performed on an
AST Power Premium 486/33 computer using the Per-
sonal Structure Determination Package [10] and the
physical constants tabulated therein. Scattering factors
and anomalous dispersion corrections were taken from
the International Tables for X-ray Crystallography [11].
The structure was solved by Patterson and Fourier
methods and refined by full-matrix least-squares, mini-
(2) An aqueous suspension of 2 (132 mg, 0.147
mmol) was refluxed for 16 h. During this period the
precipitate darkened. It was filtered off and recrystal-
lized from dichlorometane/diethyl ether to give 46 mg
of a pale yellow product. Yield 38%, m.p. 183°C. Anal.
found: C, 26.88; H, 1.56; N, 6.98; Cl, 15.9%. Anal. calc.
for C18H14Au2Cl4N4: C, 26.29; H, 1.72; N, 6.81; Cl,
17.25%. Lm (5×10−4 M, acetone): 12 V−1 cm2 mol−1
Lm (5×10−4 M, dichlorometane): 1 V−1 cm2 mol−1
,
.
IR (Nujol, cm−1) w: 1591 m, 691 s, 373 s (broad), 302
Table 3
Crystallographic data
Compound
Formula
Mr
4
C16H16AuCl2N3
518.20
Colour
Yellow
Monoclinic
P21/c (no. 14)
14.715(2)
8.142(1)
14.267(2)
90.42(1)
1709.3(4)
4
984
2.014
0.14×0.39×0.45
89.1
0.49–1.00
ꢀ
Crystal system
Space group
Table 4
˚
a (A)
Fractional atomic coordinates with estimated S.D.’s in parentheses
for the non-hydrogen atoms of [Au(3,5-Me2py)(L)C12], compound 4.
˚
b (A)
˚
c (A)
i (°)
U (A )
Z
Atom
x
y
z
3
˚
Au
−0.00683(1)
0.04283(8)
−0.05414(8)
0.2450(2)
0.2735(3)
−0.1403(2)
0.1966(4)
0.1203(3)
0.1533(3)
0.3113(3)
0. 4022(3)
0.4673(4)
0.4421(3)
0.3522(4)
0.2854(3)
−0.1552(3)
−0.2403(3)
−0.3123(3)
−0.2985(3)
−0.2107(3)
−0.2538(4)
−0.3762(3)
0.09149(2)
0.2578(1)
−0.0730(1)
−0.1372(4)
0.0203(5)
0.1862(4)
0.1084(6)
0.0072(5)
−0.1467(5)
−0.2657(5)
−0.2242(6)
−0.3474(7)
−0.5093(7)
−0.5485(6)
−0.4276(6)
0.3479(5)
0.4145(5)
0.3053(5)
0.1389(6)
0.0819(5)
0.12622(1)
0.00839(8)
0.24543(9)
0.1562(2)
0.1598(4)
0.1080(2)
0.1505(5)
0.1433(3)
0.1463(3)
0.1606(3)
0.1657(4)
0.1677(5)
0.1637(4)
0.1592(5)
0.1578(4)
0.1083(3)
0.0961(3)
0.0818(3)
0.0821(3)
0.0955(3)
0.0960(5)
0.0678(4)
F(000)
C11
C12
N1
N2
N3
C3
C4
C5
C6
Dcalc. (g cm−3
)
Crystal dimensions (mm)
v (Mo–Kh) (cm−1
)
Max/min transmission factors
Scan mode
Frame width (°)
Time per frame (s)
No. of frames
0.30
20
2500
5.50
Detector-sample distance (cm)
q-range (°)
C7
C8
C9
2–25
Reciprocal space explored
No. of reflections (total; independent)
Unique observed reflections with I\3|(I)
Final R and R% indicesa
No. of variables
9h, 9k, 9l
15 457; 4144
3182
0.024, 0.030
199
C10
C11
C12
C13
C14
C15
C16
C17
C18
Goodness-of-fitb
1.17
a R=[ꢀ(ꢁFo−kꢁFcꢁꢁ)/ꢀFo], R%=[ꢀw(Fo−kꢁFcꢁ)2/ꢀwF2o]1/2
.
b [ꢀw(Fo−kꢁFcꢁ)2/(No−Nv)]1/2
,
where w=1/[|(Fo)]2, |(Fo)=
0.5982(5)
0.0174(7)
[|2(Fo2)+(0.04Fo2)2]1/2/2Fo, No is the number of observations and Nv
the number of variables.

232
G. Minghetti et al. / Journal of Organometallic Chemistry 568 (1998) 225–232
mizing the function Sw(F0−kꢁFcꢁ)2. Anisotropic ther-
mal factors were refined for all the non-hydrogen
atoms. The hydrogen atoms of the two CH3 groups
were detected in the final Fourier maps and included in
the calculations but not refined. All the other hydrogen
atoms were placed in their ideal positions (C–H=0.97
della Ricerca Scientifica e Tecnologica (MURST) (40%)
and Consiglio Nazionale delle Ricerche (CNR) is grate-
fully acknowledged.
References
˚
A, B 1.15 times that of the carbon atom to which they
[1] M.A. Cinellu, A. Zucca, S. Stoccoro, G. Minghetti, M. Man-
assero, M. Sansoni, J. Chem. Soc. Dalton Trans. (1995) 2865.
[2] M.A. Cinellu, A. Zucca, S. Stoccoro, G. Minghetti, M. Man-
assero, M. Sansoni, J. Chem. Soc. Dalton Trans. (1996) 4217.
[3] S. Trofimenko, Inorg. Chem. 12 (1973) 1215.
[4] (a) K. Schofield, M.R. Grimmett, B.T.R. Keene, in: Heteroaro-
matic Nitrogen Compounds: The Azoles, Cambridge University
Press, Cambridge, 1976. (b) A.N. Kost, I.I. Grandberg, Adv.
Heterocycl. Chem. 6 (1966) 347.
are attached) and also not refined. The final difference
−3
˚
Fourier map shows a maximum peak of 1.52(12) eA
˚
at 1.20 A from the gold atom. The atomic coordinates
of the structure are listed in Table 4.
Molecular and packing drawings were produced with
ORTEP [12] and SCHAKAL [13] programs.
[5] (a) G. Minghetti, M.L. Ganadu, C. Foddai, M.A. Cinellu, F.
Cariati, F. Demartin, M. Manassero, Inorg. Chim. Acta 86
(1984) 93. (b) M.S. Holowczak, M.D. Stancl, G.B. Wong, J. Am.
Chem. Soc. 107 (1985) 5789. (c) B. Bruni, M. Ferraroni, P.
Orioli, G. Speroni, Acta Cryst. C52 (1996) 1423.
[6] A.R. Katritzky, C.W. Rees, Comprehensive Heterocyclic Chem-
istry, vol. 5 part 4A, Pergamon Press, Oxford, 1984, pp. 185.
[7] F. Bonati, Gazz. Chim. Ital. 119 (1989) 291.
[8] Saint, reference manual, 1994–1996, Siemensenergy and Au-
tomation, Madison, Wisconsin.
[9] G.M. Sheldrick, SADABS, Empirical Absorption Corrections
Program, University of Go¨ttingen, 1997.
[10] (a) B.A. Frenz, Comput. Phys. 2 (1988) 42. (b) B.A. Frenz,
Crystallographic Computing 5, Oxford University Press, Oxford,
1991, pp. 126.
[11] International Tables for X-ray Crystallography, vol. 4, Kynoch
Press, Birmingham, 1974.
[12] C.K. Johnson, ORTEP: A Fortran Thermal-Ellipsoid-Plot Pro-
gram for Crystal Structure Illustrations, Oak Ridge National
Laboratory, Oak Ridge, TN, 1971.
[13] E. Keller, SCHAKAL 92: A Computer Program for The Graph-
ical Representation of Crystallographic Models, University of
Freiburg, Germany, 1992.
4. Conclusions
The results of the above study show that 1-
phenylpyrazole reacts with gold(III) chloride in protic
solvents to give an adduct. At variance, anhydrous
gold(III) chloride, in aprotic media, gives an aurated
derivative. Of the two possible products, i.e. a five-
membered cyclometallated derivative arising from acti-
vation of a C–H bond of the phenyl substituent, or a
metallated species due to electrophilic substitution by
gold(III) at the most electron-rich carbon atom of the
pyrazole ring, only the latter is obtained. In addition,
salts of the organometallic anion [Au(L)Cl3]− have
been isolated which are unusually air and moisture
stable.
Acknowledgements
Financial support from Ministero dell’Universita` e
.
.