Synthesis and characterization of mononuclear amidogold(III) complexes - Crystal structure of [Au(N2C10H7(CMe2C6 H4)-6](NHC6H3Me2-2,6)] [PF6] - Oxidation of 4-methylaniline to azotoluene

Article abstract of DOI:10.1002/ejic.200200377

Mononuclear amidogold(III) complexes [Au(C,N,N)(NRR′)][PF₆] [C,N,N = N₂C₁₀H₇(CMe₂C₆ H₄)-6, where N₂C₁₀H₈ = 2,2′-bipy; R = H, R′ = p-tolyl (5), o-xylyl (6), isobutyl (7), secbutyl (8), R = R′ = Et (9)], [Au(C,N)(AcO)(NHC₆H₄NO₂-4)] (10) [C,N = NC₅H₄(CH₂C₆H₄)-2, where NC₅H₅ = py] and [Au(N,N)(NHC₆H₄NO₂-4)₂] [PF₆] (11) (N,N = 2,2′-bipy), have been synthesized in fairly good yields by reaction of the hydroxo, methoxo, or acetato complexes 1-4 [[Au(C,N,N)(OR)][PF₆] [R = H (1), Me (2)], [Au(C,N)(AcO)₂] (3), [Au(N,N)(OH)₂][PF₆] (4)} with amines. The structure of [Au(C,N,N)(NHC₆H₃Me₂-2,6)][PF₆] (6) has been determined by X-ray diffraction. Reaction of the hydroxo complex 4 with NH₂C₆H₄Me-4 gives metallic gold, the protonated ligand [N,NH][PF₆] and organic products, the main one being azotoluene. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.

Full text of DOI:10.1002/ejic.200200377

FULL PAPER
Synthesis and Characterization of Mononuclear Amidogold(III) Complexes ؊
Crystal Structure of [Au(N2C10H7(CMe2C6H4)-6](NHC6H3Me2-2,6)][PF6] ؊
Oxidation of 4-Methylaniline to Azotoluene
Maria Agostina Cinellu,*[a] Giovanni Minghetti,[a] Maria Vittoria Pinna,[a]
Sergio Stoccoro,[a] Antonio Zucca,[a] and Mario Manassero[b]
Keywords: Gold / Nitrogen ligands / Metallacycles / Amido complexes / Amine oxidation
Mononuclear amidogold(III) complexes [Au(C,N,N)(NRRЈ)]-
[PF6] [C,N,N = N2C10H7(CMe2C6H4)-6, where N2C10H8
(N,N)(OH)2][PF6] (4)} with amines. The structure of
[Au(C,N,N)(NHC6H3Me2-2,6)][PF6] (6) has been determined
by X-ray diffraction. Reaction of the hydroxo complex 4 with
NH2C6H4Me-4 gives metallic gold, the protonated ligand
[N,NH][PF6] and organic products, the main one being azoto-
luene.
=
2,2Ј-bipy; R = H, RЈ = p-tolyl (5), o-xylyl (6), isobutyl (7), sec-
butyl (8), R = RЈ = Et (9)], [Au(C,N)(AcO)(NHC6H4NO2-4)]
(10) [C,N = NC5H4(CH2C6H4)-2, where NC5H5 = py] and
[Au(N,N)(NHC6H4NO2-4)2][PF6] (11) (N,N = 2,2Ј-bipy), have
been synthesized in fairly good yields by reaction of the
hydroxo, methoxo, or acetato complexes 1−4 {[Au(C,N,N)-
(OR)][PF6] [R = H (1), Me (2)], [Au(C,N)(AcO)2] (3), [Au-
( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2003)
Introduction
[C,N,N
ϭ
N2C10H7(CHMeC6H4)-6 and N2C10H7-
(CMe2C6H4)-6], could be obtained by σ-ligand metathesis
Amido complexes of late transition metals have attracted of the corresponding methoxo complexes with p-nitroanil-
considerable interest[1] because of their involvement as in- ine.
termediates in metal-catalyzed carbonϪnitrogen bond-for-
Our study on amidogold() complexes has been ex-
mation processes.[2] Isolation of such intermediates is often tended to different amines and to different co-ligands to
hampered by their high reactivity. Nevertheless several verify the effectiveness of the synthetic method and the in-
stable late transition metal amides have been synthesized fluence of the ancillary ligand on the reactivity of the ami-
and their structures in the solid state as well as their reactiv- dogold() complex. Here we show that a number of amido-
ity investigated.[3] While gold() (a d8 metal ion) complexes gold() complexes can be isolated with different co-ligands.
with ammonia,[4] bidentate,[5] and terdentate[6] amines, and The terdentate C,N,N ligand arising from 6-(1,1-dimeth-
related amido complexes have been widely studied, mainly ylbenzyl)-2,2Ј-bipyridine is the most effective in stabilizing
from a kinetic point of view, isolated complexes with simple different amido complexes, whereas the bidentate C,N and
amide ligands[7] are still scarcely represented.[8] This short- N,N ligands (deprotonated 2-benzylpyridine and 2,2Ј-bi-
age of data[9] and a report on the intramolecular hydroa- pyridine, respectively) could stabilize only the p-nitroanilide
mination of alkynes catalyzed by gold() salts[10] prompted derivative. The gold complex [Au(N,N)(OH)2][PF6][12] (4)
us to investigate the reactivity of some gold() complexes can promote the oxidation of amines other than p-nitroanil-
with various amines.
ine. With p-toluidine the main product is azotoluene.
Previously, we have described the synthesis, characteriz-
The selective oxidation of aromatic amines under mild
ation, and reactivity of gold() cyclometallated derivatives conditions is of current interest, as pointed out in a recent
[Au(C,N,N)(Y)][PF6] (C,N,N ϭ 6-benzyl-2,2Ј-bipyridine) paper relevant to oxidation processes catalysed by an
with various anionic ligands Y.[11] Among these, two stable iron() complex.[13]
amido
complexes,
[Au(C,N,N)(NHC6H4NO2-4)][PF6]
[a]
`
Dipartimento di Chimica, Universita di Sassari,
Via Vienna 2, 07100 Sassari, Italy
Fax: (internat.) ϩ 39-079/229559
Results and Discussion
During previous studies on gold() chemistry we had
found that several complexes, [Au(C,N,N)Y]ϩ, containing
both goldϪcarbon and goldϪheteroatom bonds are access-
ible by treatment of acetato, hydroxo, and methoxo com-
E-mail: cinellu@ssmain.uniss.it
[b]
Dipartimento di Chimica Strutturale
e
Stereochimica
`
Inorganica, Universita di Milano, Centro CNR,
via Venezian 21, 20133 Milano, Italy
E-mail: m.manassero@csmtbo.mi.cnr.it
2304
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
DOI: 10.1002/ejic.200200377
Eur. J. Inorg. Chem. 2003, 2304Ϫ2310

Synthesis and Characterization of Mononuclear Amidogold(III) Complexes
plexes with protic reagents at room temperature.[11] In par-
FULL PAPER
Alkylamido complexes 7Ϫ9 were obtained simply in a
ticular, besides alkoxo, thiolato, and acetylide complexes, one-pot reaction in high yields, whereas arylamido com-
two stable gold amides have been synthesized by an ex- plexes 5 and 6 required either the use of molecular sieves
change reaction of p-nitroaniline with [Au(C,N,N)(O- to trap water or further treatment of the crude mixture with
Me)][PF6] [C,N,N
ϭ
N2C10H7(CHMeC6H4)-6 and excess amine (see Exp. Sect.). With complex 2 the trend
observed suggests that the exchange reaction proceeds, at
N2C10H7(CMe2C6H4)-6] in dichloromethane.[11]
New amidogold() complexes with three different ancil- least in this case, by nucleophilic attack of the amine at the
lary ligands, all containing nitrogen donor atoms, have been gold centre followed by proton transfer to the coordinated
obtained by the addition of different amines to hydroxo, methoxide ligand and elimination of methanol. Reaction of
methoxo, or acetato complexes under mild conditions that the more basic amine NHEt2 goes to completion within a
required excess amine to drive the equilibrium reaction to few hours. For complexes 3 and 4 other mechanisms could
completion. The nature of the ancillary ligand dramatically be operative: thus, for the neutral complex 3 dissociation of
affects the outcome of the reaction: with the terdentate the acetato group trans to the carbon atom can be envis-
cyclometallated ligand N2C10H7(CMe2C6H4)-6 both alkyl- aged. Coordination of the amine and successive depro-
and arylamides are obtained in fairly good yields tonation should follow to give the amido species.
(Scheme 1), whereas with the bidentate C,N ligand
Complexes 5Ϫ11 are air-stable compounds with relatively
NC5H4(CH2C6H4)-2 and the N,N ligand 2,2Ј-bipyridine high melting points and good stability in solution: no de-
only p-nitroanilide complexes have been isolated composition was observed even for amides having β-hydro-
(Scheme 2). Addition of even large amounts of p-nitroanil- gen atoms (7Ϫ9). In the FAB mass spectra (positive ions)
ine to complex 3 gives only substitution of one AcO group. of compounds 5, 6, 8, 9, and 11 the molecular ions [Mϩ]
Isolation of stable bis(amido) complexes other than the p- ([M Ϫ H], for 8) have been observed. In the spectrum of the
nitroaniline derivative, at least for complex 4, is probably isobutylamido derivative 7 the major peak (100% intensity)
hampered by their high reactivity.
corresponds to the species [Au(C,N,N)(NBA Ϫ H)], which
is probably formed by an exchange reaction of the nitro-
benzyl alcohol (NBA) with the amido complex. Peaks cor-
responding to this species are also found in the mass spectra
of the alkylamido complexes 8 and 9. The neutral complex
[Au(C,N)(OAc)(NHC6H4NO2-4)] (10) gives a medium-
intensity peak, corresponding to [M Ϫ AcO], as is also ob-
served for the starting bis(acetato) complex. Of the two pos-
sible geometrical isomers, trans-N(am)ϪAuϪN(py) or
trans-N(am)ϪAuϪC (am ϭ amide; py ϭ pyridine), the IR
and NMR spectra, taken together, support a trans-
NϪAuϪN arrangement. Indeed the acetato group stretch-
ing vibrations are observed at values consistent with an ace-
tato group trans to a carbon atom (see Exp. Sect.) and the
chemical shift of the H6 proton at a value similar to that
found for the bis(acetato) complex. The high trans influence
of the deprotonated amine,[6e] with respect to that of the
pyridine nitrogen atom, is probably responsible for making
thermodynamically stable the isomer with high trans-influ-
encing ligands in mutually cis positions. Analogous results
were found for the reaction of the dichloro complexes
[Au(C,N)Cl2] with excess PPh3, where only one chloride ion
was replaced to give [Au(C,N)(PPh3)Cl]ϩ, having a trans-
PϪAuϪN arrangement [C,N ϭ C6H4CH2NMe2-2,[14a]
NC5H4(CRRЈC6H4)-2[14b]].
Scheme 1
In the IR spectra, weak to medium ν˜(NϪH) absorptions
are observed in the range 3200Ϫ3336 cmϪ1. In the 1H
NMR spectra the NH resonance could be assigned due to
exchange with D2O. In complexes 5Ϫ8 the NH resonance
is shifted downfield with respect to the free ligand with
∆δ ϭ 1.5, 1.5, 2, and 1.6 ppm, respectively. In complexes 7
and 8 HϪNϪCϪH spinϪspin coupling, not present in the
free amines, is observed. HϪNϪCϪH spinϪspin coupling
has been reported in amine solutions when either the nitro-
gen atom is weakly basic or the nitrogen lone pair is coordi-
nated with a Lewis acid.[15] Thus, it appears that substi-
Scheme 2
Eur. J. Inorg. Chem. 2003, 2304Ϫ2310
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 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2305

M. A. Cinellu, G. Minghetti, M. V. Pinna, S. Stoccoro, A. Zucca, M. Manassero
FULL PAPER
tution of a hydrogen ion with an [Au(C,N,N)] group lowers
the basicity of the nitrogen atom of the amine.
The gold atom in the cation displays a distorted square-
planar coordination, with atoms Au(1), N(2), N(3), and
Because the NHCHMeEt ligand in complex 8 has a stere- C(13) essentially coplanar [maximum distances from their
˚
˚
ogenic carbon atom β to the metal atom, the methylene best plane being ϩ0.005(2) A for N(3) and Ϫ0.011(1) A for
˚
protons are diastereotopic, giving rise to two sets of mul- Au], whereas atom N(1) is displaced by 0.484(2) A out of
tiplets. Also, in complex 9 the two hydrogen atoms on each the best plane. The distortion from the ideal square-planar
methylene group of the NEt2 ligand are diastereotopic: the geometry is probably due to the limited flexibility of the
two signals are very broad at ambient temperature but a tridentate substituted bipyridine ligand. A similar distor-
well-resolved ABX3 pattern is observed at Ϫ20 °C. As re- tion has been found in [Au(C,N,N)Cl]ϩ, which differs from
ported previously for other N,N,C aurated derivatives,[11] the present one only in the substitution of the amido ligand
the six-membered C,N ring is fluxional on the NMR time with a chloride.[16] Bond lengths and angles in the present
scale. Thus, one resonance alone is observed for the methyl cation can be compared with those found in
protons on the benzylic carbon atom of complexes 5Ϫ9: no [Au(C,N,N)Cl]ϩ. Thus, the AuϪN(1) and AuϪC(13) bond
˚
significant variation is observed on lowering the tempera- lengths [2.128(2) and 2.018(2) A, respectively] reported here
ture from 20 to Ϫ80 °C.
are very similar to those in [Au(C,N,N)Cl]ϩ [2.121(5) and
˚
A diffraction study of suitable crystals of complex 6 re- 2.009(6) A, respectively]. The slight elongation of the pre-
˚
vealed
a
structure that consists of [Au(C,N,N)- sent AuϪN(2) distance [2.056(2) A] with respect to that of
Ϫ
(NHC6H3Me2-2,6)]ϩ cations and PF6 anions packed in a [Au(C,N,N)Cl]ϩ [2.009(4) A] indicates that the trans influ-
molar ratio 1:1 with normal van der Waals contacts. An ence of the amide ligand is stronger than that of the chlo-
ORTEP view of the cation with the atom labelling scheme ride ligand. In the absence of suitable structural data[17] the
˚
˚
is shown in Figure 1. Selected bond lengths and angles are Au(1)ϪN(3) bond length [2.015(2) A] can be compared to
reported in Table 1.
the PtϪN distance found in trans-[PtCl(NHC6H4I-
˚
4)(PEt3)2] [2.006(4) A] and in a number of other (amido)Pt
complexes (ref.[3l] and refs. therein). The six-membered
metallacycle is in a boat conformation, with atoms N(2),
C(10), C(12), and C(13) essentially coplanar, maximum
deviations from their best plane being ϩ0.025(2) and
˚
Ϫ0.025(2) A for C(12) and C(10), respectively, whereas Au
˚
and C(11) lie 0.543(1) and 0.641(2) A, respectively, above
their best plane.
Reaction of complex 3 with amines other than p-nitro-
aniline led to mixtures of unidentified products and a small
amount of gold. In contrast, complex 4 was quickly decom-
posed by the addition of amines and, with p-toluidine, it
was possible to identify the main reaction products
(Scheme 3). In addition to gold, which separated as a dark
powder, 2,2Ј-bipyridine was recovered almost quantitatively
(80%) as the salt [N,NH][PF6]. Chromatography on silica
gel of the organic fraction allowed us to isolate azotoluene
(trans isomer) in 43% yield, based on the gold complex.
Figure 1. ORTEP view of the cation in compound 6; ellipsoids are
drawn at the 30% probability level
˚
Table 1. Selected bond lengths [A] and angles [°] with e.s.d.s in
parentheses for the complex cation in compound 6
AuϪN(1)
AuϪN(3)
N(3)ϪC(20)
2.128(2) AuϪN(2)
2.015(2) AuϪC(13)
1.401(3) N(3)ϪH(1)
2.056(2)
2.018(2)
0.84(3)
N(1)ϪAuϪN(2)
N(1)ϪAuϪC(13)
N(2)ϪAuϪC(13)
AuϪN(3)ϪC(20)
79.1(1)
164.1(1)
91.4(1)
N(1)ϪAuϪN(3)
90.9(1)
169.4(1)
99.1(1)
99(2)
Scheme 3
N(2)ϪAuϪN(3)
N(3)ϪAuϪC(13)
AuϪN(3)ϪH(1)
126.1(2)
The formation of azobenzene, as the main by-product,
was observed in the oxidative carbonylation of amines cata-
C(20)ϪN(3)ϪH(1) 112(2)
2306
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Eur. J. Inorg. Chem. 2003, 2304Ϫ2310

Synthesis and Characterization of Mononuclear Amidogold(III) Complexes
FULL PAPER
[Au(C,N)(AcO)2] (3): Solid AcOAg (0.339 g, 2.03 mmol) was added
to a suspension of [Au(C,N)Cl2] (0.401 g, 0.92 mmol) in acetone
(20 mL). The resulting suspension was stirred at room temperature
for 8 h and then filtered through Celite. Addition of diethyl ether
to the concentrated solution afforded a creamy solid product.
Recrystallization from chloroform/diethyl ether gave an analytical
sample. Yield: 0.300 g (67%), m.p. 152 °C (dec.). C16H16AuNO4
(483.30): calcd. C 39.76, H 3.34, N 2.90; found C 39.23, H 3.14, N
2.92. IR (Nujol): ν˜ ϭ 1668 vs and 1627 vs (CϭO), 1568 m, 1307
vs and 1278 vs (CϪO), 1042 m, 1031 m, 1007 m, 762 s, 704 m, 679
lyzed by gold complexes, in particular when HAuCl4 was
employed in the reaction with aniline.[18] Azobenzene de-
rivatives are also by-products in the FeCl2py4ϩ-catalyzed
transformation of aromatic amines by H2O2,[13] as well as
the main products of the ferrate oxidation of anilines, both
in homogeneous[19] and in heterogeneous phases.[20] Differ-
ent reaction mechanisms for the formation of azo com-
pounds in the homogeneous phase have been claimed.[13,19]
In our case a bis(amido) intermediate can be envisaged
for the formation of azotoluene. N,NЈ-Di-p-tolylhydrazine s cmϪ1 1H NMR (CDCl3): δ ϭ 9.02 (d, 3J ϭ 5.1 Hz, 1 H, H6),
.
8.03Ϫ7.01 (m, 7 H, other aromatic H), 4.38 (s, 2 H, CH2), 2.11 (s,
3 H, Me), 2.04 (s, 3 H, Me) ppm. MS (FABϩ): m/z (%) ϭ 533 (20)
[Au(C,N)2], 424 (100) [M Ϫ CH3CO2].
could form by NϪN coupling of the bis(amido) complex
[Au(N,N)(NHC6H4Me2-4)2][PF6], analogous to 11, and
then be oxidized to azotoluene.[21] This implies an unstable
gold() intermediate [Au(N,N)(solv)][PF6] (solv ϭ H2O,
MeCN). In an attempt to trap it, the reaction was carried
out in the presence of PPh3 (Scheme 3). Indeed, a gold()
intermediate (12) was isolated, although not quantitatively,
[Au(N,N)(OH)2][PF6] (4): This was prepared according to ref.[12]
[Au(C,N,N)(NH-p-tol)][PF6] (5). Method (a): Solid p-toluidine
(0.064 g, 0.6 mmol) was added to a solution of 1 (0.126 g,
0.2 mmol) in dichloromethane (20 mL). The resulting redϪorange
solution was stirred at room temperature for 15 h in the presence
of activated molecular sieves. The filtered solution was then con-
centrated to a small volume and diethyl ether added to give a
redϪorange solid product. Yield: 0.118 g (82%). Method (b): Solid
p-toluidine (0.042 g, 0.39 mmol) was added to a solution of 2
(0.082 g, 0.13 mmol) in dichloromethane (15 mL). The resulting
redϪorange solution was stirred for 23 h at room temperature and
then concentrated to a small volume. Addition of diethyl ether gave
a redϪorange precipitate of the equilibrium mixture (1H NMR cri-
terion) which was treated with excess p-toluidine in dichlorometh-
ane solution for 24 h to give complete conversion of 2. Yield:
0.072 g (76%), m.p. 193Ϫ194 °C. C26H25AuF6N3P (721.46): calcd.
C 43.28, H 3.49, N 5.83; found C 42.80, H 3.35, N 5.61. ΛM (5·10Ϫ4
mol·dmϪ3, Me2CO) ϭ 120 ΩϪ1·cm2·molϪ1. IR (Nujol): ν˜ ϭ 3300
w (NH), 1600 s, 1560 m, 1500 s, 1250 s, 1160 m, 1100 m, 1070 m,
and
identified
as
the
known
complex
[(N,N)Au(PPh3)][PF6].[22] The isolobal analogy between the
cations [(N,N)H]ϩ and [(N,N)Au(PPh3)]ϩ is notable.
Experimental Section
General: The gold complexes [Au(C,N,N)Cl][PF6] and
[Au(C,N)Cl2] were obtained according to ref.[11] and ref.[14b]
,
respectively. All the amines were used as received from commercial
sources; the solvents were purified and dried according to standard
˚
methods. Celite (filter agent) and molecular sieves (4 A) were pur-
chased from Aldrich, and silica gel (70Ϫ230 mesh ASTM) from
Merck. Elemental analyses were performed with a PerkinϪElmer
Elemental Analyzer 240B by Mr. A. Canu (Dipartimento di Chim-
1040 m, 1025 vs, 846 vs (broad), 780 s, 640 w cmϪ1 1H NMR
.
`
ica, Universita di Sassari). Conductivities were measured with a
(CD2Cl2): δ ϭ 9.24 (dd, 3J ϭ 5.4, 4J ϭ 1.0 Hz, 1 H, H6Ј), 8.66Ϫ7.06
(m, 10 H, other aromatic H), 6.97 (d, 3J ϭ 8.4 Hz, 2 H, Hortho),
Philips PW 9505 conductimeter. Infrared spectra were recorded
with a PerkinϪElmer 983 spectrophotometer; the values are given
3
6.89 (d, J ϭ 8.4 Hz, 2 H, Hmeta), 5.07 (s, 1 H, NH), 2.23 (s, 3 H,
in cmϪ1 1H and 31P{1H} NMR spectra were recorded with a
.
Me), 2.12 (s, 6 H, Me) ppm. MS (FABϩ): m/z (%) ϭ 576 (100)
Varian VXR 300 spectrometer operating at 299.9 and 121.4 MHz,
respectively. Chemical shifts are given in ppm relative to internal
TMS (1H) or external H3PO4 (31P). Mass spectra were obtained
with a VG 7070 instrument operating under FAB conditions, with
3-nitrobenzyl alcohol (NBA) as supporting matrix or EI con-
ditions. GC/MS analyses were conducted with a Hewlett-Packard
G1800B Gas Chromatograph Electron Ionization Detector (GCD
System).
[Mϩ], 470 (45) [Au(C,N,N)], 273 (40) [C,N,N].
[Au(C,N,N)(NH-o-xylyl)][PF6] (6): Liquid o-xylidine (0.073 g,
0.6 mmol) was added to a solution of 1 (0.126 g, 0.2 mmol) in di-
chloromethane (20 mL). The resulting dark red solution was stirred
at room temperature for 15 h in the presence of activated molecular
sieves. The solution was then filtered and concentrated to a small
volume and diethyl ether added to give a dark red solid product.
Yield: 0.115 g (78%), m.p. 192 °C. C27H27AuF6N3P (735.45): calcd.
C 44.09, H 3.70, N 5.71%; found C 44.00, H 4.04, N 5.61. ΛM
(5·10Ϫ4 mol·dmϪ3, Me2CO) ϭ 125 ΩϪ1·cm2·molϪ1. IR (Nujol): ν˜ ϭ
3300 w (NH), 1590 s, 1220 s, 1080 m, 1038 s, 1020s, 840 vs (broad),
[Au(C,N,N)(OH)][PF6] (1): An aqueous solution of KOH (0.033 g,
0.59 mmol) was added to an aqueous suspension of
[Au(C,N,N)Cl][PF6] (0.179 g, 0.27 mmol). The mixture was heated
under reflux for 1 h whilst stirring and then filtered. The volume
of the colourless filtrate was reduced in a rotary evaporator until
crystallization was observed. The resultant white product was col-
lected by filtration and dried in vacuo. Yield: 0.128 g (75%), m.p.
170 °C. C19H18AuF6N2OP (632.32): calcd. C 36.09, H 2.87, N 4.43;
found C 35.91, H 2.71, N 4.33. ΛM (5·10Ϫ4 mol·dmϪ3, Me2CO) ϭ
106 ΩϪ1·cm2·molϪ1. IR (Nujol): ν˜ ϭ 3360 m (broad) (OH), 1599
s, 1561 m, 1082 m, 1025 s, 846 vs (broad) cmϪ1. 1H NMR ([D6]ace-
3
770 vs, 640 m cmϪ1. 1H NMR (CD2Cl2): δ ϭ 9.12 (d, J ϭ 5.4 Hz,
3
1 H, H6Ј), 8.61Ϫ6.84 (m, 10 H, other aromatic H), 7.03. (d, J ϭ
3
7.3 Hz, 2 H, Hmeta), 6.92 (t, J ϭ 7.3 Hz, 1 H, Hpara), 5.04 (s, 1 H,
NH), 2.31 [s, 6 H, 2 Me (xylydine)], 2.12 [s, 6 H, 2 Me (bipy)] ppm.
MS (FABϩ): m/z (%) ϭ 590 (100) [Mϩ], 470 (65) [Au(C,N,N)], 273
(30) [C,N,N]. Crystals suitable for a diffraction study were obtained
by slow diffusion of diethyl ether into a dichloromethane solution
of 6.
3
4
tone): δ ϭ 9.21 (dd, J ϭ 5.4, J ϭ 1.9 Hz, 1 H, H6Ј), 8.92Ϫ7.18
(m, 10 H, other aromatics), 4.58 (s, 1 H, OH), 2.11 (s, 6 H, CH3)
[Au(C,N,N)(NH-iBu)][PF6] (7): Liquid isobutylamine (0.102 g,
1.4 mmol) was added to a solution of 2 (0.092 g, 0.14 mmol) in
dichloromethane (15 mL). The resulting greenish solution was
stirred at room temperature for 6 h and then concentrated to a
ppm. MS (FABϩ): m/z (%)
ϭ
487 (100) [Mϩ], 470 (30)
[Au(C,N,N)], 393 (10) [M Ϫ OH Ϫ C6H5], 273 (50) [C,N,N].
[Au(C,N,N)(OMe)][PF6] (2): This was prepared according to ref.[11]
Eur. J. Inorg. Chem. 2003, 2304Ϫ2310
www.eurjic.org
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2307

M. A. Cinellu, G. Minghetti, M. V. Pinna, S. Stoccoro, A. Zucca, M. Manassero
FULL PAPER
small volume. Addition of diethyl ether gave a greenish-yellow pre-
[Au(N,N)(NHC6H4NO2-4)2][PF6]
(11):
Solid
p-nitroaniline
cipitate of the analytical sample. Yield: 0.095 g (97%), m.p. 153 °C. (0.341 g, 2.44 mmol) was added to a solution of 4 (0.130 g,
C23H27AuF6N3P (687.45): calcd. C 40.18, H 3.96, N 6.11; found
0.24 mmol) in acetone (20 mL); the resulting yellow solution was
stirred at room temperature for 53 h. During this period the solu-
C 40.26, H 3.81, N 5.79. ΛM (5·10Ϫ4 mol·dmϪ3, Me2CO) ϭ 128
Ω
Ϫ1·cm2·molϪ1. IR (Nujol): ν˜ ϭ 3300 w (NH), 1596 s, 1562 m, tion turned deep red. Addition of diethyl ether to the concentrated
1064 m, 1042 s, 850 vs (broad) cmϪ1. 1H NMR (CD2Cl2): δ ϭ 9.25 solution gave a red product, which was washed with methanol to
(dd, J ϭ 5.4, J ϭ 1.0 Hz, 1 H, H6Ј), 8.62Ϫ7.32 (m, 10 H, other
give an analytical sample. Yield: 0.037 g (20%), m.p. 163 °C.
3
4
3
aromatic H), 3.30 (t, JHNϪCH ϭ 9.0 Hz, 1 H, NH), 2.98 (dd, C22H18AuF6N6O4P (772.39): calcd. C 34.20, H 2.35, N 10.88;
3JH,CϪCH ϭ 6.6, 3JH,CϪNH ϭ 9.0 Hz, 2 H, CH2), 2.09 (s, 6 H, Me),
found C 33.98, H 2.22, N 10.45. ΛM (5·10Ϫ4 mol·dmϪ3, Me2CO) ϭ
3
1.96 (m, 1 H, CH), 1.10 (d, J ϭ 6.8, 6 H, Me) ppm. FABϩ: m/z 120 ΩϪ1·cm2·molϪ1. IR (Nujol): ν˜ ϭ 3336 m (NϪH), 1602 s, 1585
(%) ϭ 622 (100) [Au(C,N,N)(NBA Ϫ H)], 470 (35) [Au(C,N,N)], vs (NO2), 1342 vs (broad) (NO2), 1251 s, 1113 vs, 846 vs (broad)
273 (40) [C,N,N].
cmϪ1. 1H NMR ([D6]acetone): δ ϭ 9.35 (d, 3J ϭ 5.6 Hz, 2 H, H6),
3
3
4
9.06 (d, J ϭ 7.6 Hz, 2 H, H3), 8.79 (td, J ϭ 7.8, J ϭ 1.5 Hz, 2
3
3
H, H4), 8.29 (t, J ϭ 7.1 Hz, 2 H, H5), 7.78 (d, J ϭ 9.0 Hz, 4 H,
[Au(C,N,N)(NH-sBu)][PF6] (8): Liquid sec-butylamine (0.102 g,
1.4 mmol) was added to a solution of 2 (0.092 g, 0.14 mmol) in
dichloromethane (15 mL). The resulting orange solution was
stirred at room temperature for 23 h and then concentrated to a
small volume. Addition of diethyl ether gave an orange precipitate
of the analytical sample. Yield: 0.086 g (89%), m.p. 150 °C (dec.).
C23H27AuF6N3P (687.45): calcd. C 40.18, H 3.96, N 6.11; found
C 40.06, H 3.72, N 5.83. ΛM (5·10Ϫ4 mol·dmϪ3, Me2CO) ϭ 126
3
Hmeta), 7.10 (d, J ϭ 9.0 Hz, 4 H, Hortho), 6.03 (s, 2 H, NH) ppm.
MS (FABϩ): m/z (%)
ϭ Ϫ
627 (20) [Mϩ], 490 (82) [M
NHC6H4NO2-4], 353 [Au(N,N)].
Reaction of [Au(N,N)(OH)2][PF6] (4) with NH2C6H4Me-4: Solid p-
toluidine (0.098 g, 0.92 mmol) was added to a stirred solution of 4
(0.122 g, 0.23 mmol) in MeCN (20 mL); the resulting solution was
stirred for 24 h at room temperature. During this period the solu-
tion turned dark red, and separation of a dark powder was ob-
served. After filtration through Celite, the solution was concen-
trated to a small volume; subsequent addition of diethyl ether af-
forded a dirty white precipitate that was filtered off and identified
as [N,NH][PF6][23] (0.056 g, 80%). The mother liquor was concen-
trated to dryness to give a dark red solid, which was taken up with
benzene and eluted through a column (15 ϫ 1 cm) of silica gel.
Removal of the solvent from the first eluate gave an orange crystal-
line product that was identified as trans-azotoluene. Yield: 0.021 g
(43.4% with respect to complex 4), m.p. 140 °C. MS (EIϩ): m/z ϭ
211 [MHϩ], 119 [M Ϫ C6H5CH2], 92 [C6H5Me]. 1H NMR
Ω
Ϫ1·cm2·molϪ1. IR (Nujol): ν˜ ϭ 3280 w (NH), 1590 s, 1520 m,
1080 s, 1040 s, 846 vs (broad) cmϪ1. H NMR (CD2Cl2): δ ϭ 9.50
1
(dd, J ϭ 5.4, J ϭ 1.0 Hz, 1 H, H6Ј), 8.58Ϫ7.27 (m, 10 H, other
3
4
3
aromatics), 3.35 (d, JHNϪCH ϭ 4.0 Hz, 1 H, NH), 3.15 (m, 1 H,
CH), 2.12 (s, 6 H, Me), 1.79 (m, 1 H, CHAHB), 1.64 (m, 1 H,
CHAHB), 1.35 (d, 3J ϭ 6.3 Hz, 3 H, CH3CH), 1.03 (t, 3J ϭ 7.3,
7.6 Hz, 3 H, CH3CH2) ppm. MS (FABϩ): m/z (%) ϭ 622 (100)
[Au(C,N,N)(NBA Ϫ H)], 541 (10) [M Ϫ H], 470 (40) [Au(C,N,N)],
273 (75) [C,N,N].
[Au(C,N,N)(NEt2)][PF6] (9): Liquid diethylamine (0.095 g,
1.3 mmol) was added to a solution of 2 (0.083 g, 0.13 mmol) in
dichloromethane (15 mL). The resulting red solution was stirred at
room temperature for 2 h then concentrated to a small volume.
Addition of diethyl ether gave a dark orange precipitate of the ana-
lytical sample. Yield 0.086 g (96%), m.p. 160 °C. C23H27AuF6N3P
(687.45): calcd. C 40.18, H 3.96, N 6.11; found C 39.87, H 3.81, N
5.86. ΛM (5·10Ϫ4 mol·dmϪ3, Me2CO) ϭ 120 ΩϪ1·cm2·molϪ1. IR
3
3
(CDCl3): δ ϭ 7.81 (d, J ϭ 8.1 Hz, 2 H), 7.30 (d, J ϭ 8.1 Hz, 2
H), 2.42 (s, 3 H, Me) ppm.
Reaction of [Au(N,N)(OH)2][PF6] (4) with NH2C6H4Me-4 and
PPh3: A solution of PPh3 (0.131 g, 0.5 mmol) in MeCN was added
to a stirred solution of complex 4 (0.266 g, 0.5 mmol) and p-tol-
uidine (0.214 g, 2 mmol) in MeCN (20 mL). The reaction mixture
was stirred for 24 h at room temperature, filtered through Celite
and concentrated to a small volume. Addition of diethyl ether af-
forded a dirty white product that was recrystallized from dichloro-
methane/diethyl ether to give an analytical sample, which was
identified as [(N,N)Au(PPh3][PF6] (12) (0.195 g, 51%), m.p. 195 °C
(dec.). C28H23AuF6N2P2 (760.39): calcd. C 44.22, H 3.05, N 3.68;
found C 44.38, H 3.22, N 3.62. 1H NMR (CD2Cl2): δ ϭ 8.63 (d,
3J ϭ 4.1 Hz, 2 H, H6), 8.33 (d, 3J ϭ 8.0 Hz, 2 H, H3), 8.19 (t, 3J ϭ
(Nujol): ν˜ ϭ 1595 s, 1576 m, 1082 s, 1021 s, 846 vs (broad) cmϪ1
.
1H NMR (CD2Cl2, Ϫ20 °C): δ ϭ 9.37 (d, J ϭ 4.8 Hz, 1 H, H6Ј),
3
8.57Ϫ7.29 (m, 10 H, other aromatics), 3.04 (m, 2J ϭ 14.3 Hz, 3J ϭ
2
3
7.0 Hz, 2 H, CHAHB), 2.62 (m, J ϭ 14.3 Hz, J ϭ 7.0 Hz, 2 H,
CHAHB), 2.12 (s, 6 H, Me), 1.24 (t, J ϭ 7.0 Hz, 6 H, CH3ϪCH2)
3
ppm. MS (FAB): m/z (%) ϭ 622 (37) [Au(C,N,N)(NBA Ϫ H)], 542
(82) [Mϩ], 470 (90) [Au(C,N,N)], 273 (64) [C,N,N].
[Au(C,N)(OAc)(NHC6H4NO2-4)]
(10):
Solid
p-nitroaniline
3
7.3 Hz, 2 H, H4), 7.72 (t, J ϭ 7.6 Hz, 2 H, H5), 7.67Ϫ7.52 [m, 15
(0.138 g, 1 mmol) was added to a solution of complex 3 (0.120 g,
0.25 mmol) in dichloromethane (20 mL); the resulting yellow solu-
tion was then stirred for 24 h at room temperature. During this
period the solution turned redϪorange. Addition of diethyl ether
to the concentrated solution caused precipitation of the equilibrium
mixture (1H NMR criterion). The mixture was then subjected to
the procedure described above until complete conversion of 3 oc-
curred. Yield: 0.085 g (60%), m.p. 157 °C (dec.). C20H18AuN3O4
H, P(C6H5)3] ppm. 31P{1H} NMR (CD2Cl2): δ ϭ 31.3 (s, PPh3),
Ϫ144.06 (sept, JPϪF ϭ 711.1 Hz, PF6) ppm. The mother liquor,
containing organic products, was concentrated to dryness. The resi-
due was then taken up with benzene and eluted through a column
(20 ϫ 1 cm) of silica gel. Removal of the solvent from the first
eluate gave an orange crystalline product, which was identified as
trans-azotoluene, yield 0.027 g (25.7%).
(561.37): calcd. C 42.79, H 3.23, N 7.49; found C 42.68, H 3.15, N X-ray Data Collection and Structure Determination: Crystal data
7.27. IR (Nujol): ν˜ ϭ 3330 m (NϪH), 1624 s (CϭO), 1583 vs and other experimental details are summarized in Table 2. The dif-
(NO2), 1299 vs (broad) (CϪO) ϩ (NO2), 1182 s, 1111 vs, 834 m,
fraction experiment was carried out with a Bruker SMART CCD
753 m cmϪ1 1H NMR (CDCl3): δ ϭ 8.94 (d, 3J ϭ 5.6 Hz,1 H, area-detector diffractometer at 223 K using Mo-Kα radiation (λ ϭ
.
3
H6), 8.02Ϫ7.01 (m, 7 H, other aromatic H), 7.89 (d, J ϭ 9.3 Hz, 0.71073 A) with a graphite crystal monochromator in the incident
˚
3
2 H, Hmeta), 6.65 (d, J ϭ 9.3 Hz, 2 H, Hortho), 4.75 (s, 1 H, NH), beam. Cell parameters and orientation matrix were obtained from
4.38 (s, 2 H, CH2), 2.00 (s, 3 H, Me) ppm. MS (FABϩ): m/z (%) ϭ the least-squares refinement of 141 reflections measured in three
533 (100) [Au(C,N)2], 502 (68) [M Ϫ MeCO2], 366 (40) [Au(C,N)]. different sets of 15 frames each, in the range 3° Ͻ θ Ͻ 23°. At the
2308
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
Eur. J. Inorg. Chem. 2003, 2304Ϫ2310

Synthesis and Characterization of Mononuclear Amidogold(III) Complexes
FULL PAPER
end of data collection the first 50 frames, containing 325 reflec-
Cambridge Crystallographic Data Centre, 12 Union Road, Cam-
tions, were recollected to monitor crystal decay, which was not ob- bridge CB2 1EZ, UK; Fax: (internat.) ϩ 44-1223/336-033; E-mail:
served, so that no time-decay correction was needed. The collected
frames were processed with the software SAINT,[24a] and an ab-
sorption correction was applied (SADABS)[24b] to the 19993 col-
lected reflections, 7461 of which are unique, with Rint ϭ 0.0307
(Rint ϭ Σ|F2o Ϫ Fm2 ean|/ΣF2o). Calculations were performed with a
Pentium III PC using the Personal Structure Determination Pack-
age,[25] and the physical constants tabulated therein. Scattering fac-
tors and anomalous dispersion corrections were taken from ref.[26]
The structure was solved by direct methods (SHELXS 86)[27] and
refined by full-matrix least squares using all reflections and minim-
izing the function Σw(F2o Ϫ k|Fc|2)2 (refinement on F2). Anisotropic
thermal factors were refined for all non-hydrogen atoms. The seven
hydrogen atoms bonded to N(3) and to the two methyl groups of
the 2,6-xylidine ligand were detected in the final Fourier maps and
refined with fixed thermal parameters. The other hydrogen atoms
deposit@ccdc.cam.ac.uk].
Acknowledgments
We are grateful to the University of Sassari for financial support
(60%) and to the Regione Autonoma della Sardegna (RAS) for a
grant to M. A. C. (L.R.9/8/1950, n. 43).
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735.47
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11.234(1)
12.429(1)
107.44(1)
95.64(1)
92.74(1)
1291.1(2)
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V [A ]
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1.892
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Crystal dimensions [mm]
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58.11
0.41/1.00
ω
0.30
20
2650
4.00
3Ϫ26
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[7]
2
2
2 2
2 2 1/2
[a] R2 ϭ [Σ(|Fo2 Ϫ kFc |)/ΣFo ], R2w ϭ [Σw(Fo2 Ϫ kFo ) /Σw(Fo ) ]
.
2 2
2
2 2
2
[8] [8a]
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Eur. J. Inorg. Chem. 2003, 2304Ϫ2310
www.eurjic.org
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2309

M. A. Cinellu, G. Minghetti, M. V. Pinna, S. Stoccoro, A. Zucca, M. Manassero
FULL PAPER
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M. A. Cinellu, G. Minghetti, M. V. Pinna, S. Stoccoro, A.
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4612Ϫ4615.
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references therein.
The identity of this compound was confirmed by preparing it
independently from bipy and an aqueous solution of HPF6.
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To the best of our knowledge, X-ray data relevant to AuϪN
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Eur. J. Inorg. Chem. 2003, 2304Ϫ2310