Gold(i)-carbenes derived from 4-pyridylisocyanide complexes: Supramolecular macrocycles supported by hydrogen bonds, and luminescent behavior

Article abstract of DOI:10.1039/b711430c

Monomeric gold(i) carbenes of the type [AuR{C(NR¹R ²)(NHPy-4)}] (Py-4 = 4-pyridyl) have been prepared with R = C ₆F₅, Fmes (2,4,6-tris(trifluoromethyl)phenyl) by reaction of the corresponding isocyanide compounds [AuR(CNPy-4)] with primary or secondary amines. The single crystal X-ray diffraction structures of [Au(C ₆F₅){C(NEt₂)(NHPy-4)}]·OH₂, [Au(Fmes){C(NEt₂)(NHPy-4)}], and [Au(Fmes){C(NHMe)(NHPy-4)}] show that the presence of the NHPy-4 moiety formed induces the formation of supramolecular macrocycles only supported by hydrogen bond interactions, either with N-H groups of other molecules (tetrameric macrocycles), or with water molecules (dimeric macrocycles). Dimeric gold(i) carbenes were also produced using a diamine to form a bridging carbene, or using octafluorobiphenyl to form a Au-C₆F₄-C₆F₄-Au bridge, but the solid state structures of these dimers could not be solved. Most of the complexes herein described display luminescent properties. The Royal Society of Chemistry.

Full text of DOI:10.1039/b711430c

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www.rsc.org/dalton | Dalton Transactions
Gold(I)–carbenes derived from 4-pyridylisocyanide complexes: supramolecular
macrocycles supported by hydrogen bonds, and luminescent behavior†
Camino Bartolome´, Marta Carrasco-Rando, Silverio Coco, Carlos Cordovilla, Pablo Espinet* and
Jose M. Mart´ın-Alvarez
Received 26th July 2007, Accepted 31st August 2007
First published as an Advance Article on the web 14th September 2007
DOI: 10.1039/b711430c
Monomeric gold(I) carbenes of the type [AuR{C(NR1R2)(NHPy-4)}] (Py-4 = 4-pyridyl) have been
prepared with R = C6F5, Fmes (2,4,6-tris(trifluoromethyl)phenyl) by reaction of the corresponding
isocyanide compounds [AuR(CNPy-4)] with primary or secondary amines. The single crystal X-ray
diffraction structures of [Au(C6F5){C(NEt2)(NHPy-4)}]·OH2, [Au(Fmes){C(NEt2)(NHPy-4)}], and
[Au(Fmes){C(NHMe)(NHPy-4)}] show that the presence of the NHPy-4 moiety formed induces the
formation of supramolecular macrocycles only supported by hydrogen bond interactions, either with
N–H groups of other molecules (tetrameric macrocycles), or with water molecules (dimeric
macrocycles). Dimeric gold(I) carbenes were also produced using a diamine to form a bridging carbene,
or using octafluorobiphenyl to form a Au–C6F4–C6F4–Au bridge, but the solid state structures of these
dimers could not be solved. Most of the complexes herein described display luminescent properties.
With these precedents, we planned to prepare and study
Introduction
carbene complexes of the type [AuR{C(NR1R2)(NHPy-4)}], in
The design and synthesis of supramolecular self-organized systems
which the 4-pyridyl (Py-4) group might act as an H-acceptor in
with specific properties and functions in order to obtain advanced
intermolecular hydrogen bonding. Here we report the synthesis
and complete characterization of a family of carbenes of this kind
gineering is the planned synthesis of a crystal structure associated
and study their structures and photophysical properties.
materials has increased in recent years.1,2 In this respect, crystal en-
with a pre-desired property and requires the control of the shape
and the distribution of each individual building block to favor
Results and discussion
intermolecular interactions. Such interactions must be relatively
weak and thermodynamically stable, but kinetically labile, to allow
the specific rearrangement of the discrete molecules in a well
organized supramolecular structure.3 Hydrogen bonding is one
of the forces that provides this flexibility and stability.
Since the discovery of the chromium carbene complexes over
four decades ago,4 metal transition carbene complexes have
attracted much attention due to their properties as useful reagents
and catalysts in organic synthesis,5 and many transition metal
carbene complexes have been reported.6,7 The use of Au carbenes
as catalysts has provided spectacular results recently.8 However
the possibility of using carbene complexes in the construction of
supramolecular assemblies in order to obtain frameworks that
combine the properties of metal carbenes with those associated
with supramolecular structures stabilized by hydrogen bonds
seems to be unexplored.
Synthesis of gold(I) isocyanide and gold(I) carbene derivatives
The synthesis of the neutral gold isocyanide complexes
[AuR(CNPy-4)] (R = C6F5, 1; Fmes, 2; Fmes = 2,4,6-tris-
(trifluoromethyl)phenyl was carried out from the corresponding
gold tetrahydrothiophene precursors [AuR(tht)] (R = C6F5,11
Fmes12) and [Au2(l-C6F4C6F4)(tht)2]13 by substitution of tht
with 4-(isocyano)pyridine (CNPy-4), as reported for similar gold
compounds.14
The gold carbene derivatives were prepared from the corre-
sponding gold isocyanide complexes by nucleophilic attack of
the appropriate primary or secondary amine or diamine to the
a-carbon atom of the coordinated isocyanide, as described for
related complexes (Scheme 1).15–17
Similar procedures on [Au2(l-C6F4C6F4)(tht)2]18 afforded
the dinuclear complexes containing a bridging perfluorinated
bis(aryl) moiety [Au2(l-C6F4C6F4)(CNPy-4)2] (8) and [Au2(l-
C6F4C6F4){(C(NHMe)(NHPy-4)}2] (9) (Scheme 2).
Additional interest in supramolecular structures of Au(I) com-
plexes is derived from the assumed belief that short d10–d10 contacts
are often responsible for the luminescent properties observed
in these materials,9 although recent work has shown that these
interactions are not always needed, and the luminescence of gold
complexes can also have an intramolecular origin.10
Molecular characterization of the complexes
C, H, N analyses, yields, and relevant IR data for the complexes
are given in the Experimental section. All isocyanide complexes
show one m(C≡N) typical IR absorption of coordinated isocyanide
at higher wavenumbers (ca. 100 cm−1 higher) than for the free
ligands.14 Their 1H NMR spectra display two somewhat distorted
“doublets” (strictly AAꢀXXꢀ systems) in the range 7.8–8.9 ppm,
IU CINQUIMA/Qu´ımica Inorga´nica, Facultad de Ciencias, Universidad
de Valladolid, 47071, Valladolid, Castilla y Leo´n, Spain. E-mail: espinet@
qi.uva.es
† CCDC reference numbers 655314–655316. For crystallographic data in
CIF or other electronic format see DOI: 10.1039/b711430c
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Fig. 1 Conformers observed in solutions for 3–6, and 9.
An exchange process between the carbene hydrogen and free water
was observed in both carbenes.
1
In the 19F and H NMR spectra of the carbenes derived from
methylamine (5, 6 and 9) two groups of signals reveal the presence
of the two isomers B and C in Fig. 1, which were assigned by
irradiation and NOE experiments. The minor signals correspond
to C and the major ones to the less crowded conformer B. As for 3
and 4, an exchange process between the carbene hydrogen atoms
and free water is also observed. The conformer ratio changes with
the polarity of the deuterated solvent, suggesting an exchange
process between B and C in solution.
Scheme 1 Synthesis of aryl gold carbene derivatives.
Complex 7 is poorly soluble and therefore it could be charac-
terized only by C, H, N analysis and IR spectroscopy.
Solid state characterization of the complexes
As stated in the Introduction, the system was designed to produce
carbenes where the Py fragment should generate intermolecular
hydrogen bonding with the carbene H atoms. It was not possible
to grow crystals of 7 due to its insolubility which suggests a
polymeric structure. The crystals obtained for the other binuclear
complex 9 were not suitable for X-ray diffraction. X-Ray quality
crystals for R = C6F5 could be grown only for the gold carbenes
[Au(C6F5){C(NEt2)(NHPy-4)}] (3). Fortunately, for R = Fmes the
two complementary complexes, [Au(Fmes){C(NEt2)(NHPy-4)}]
(4) in which the NHPy-4 fragment can be involved in intermolecu-
lar hydrogen bonding, and [Au(Fmes){C(NHMe)(NHPy-4)}] (6)
which has an additional H atom (the amine hydrogen) also able to
participate in these intermolecular interactions, could be obtained
as good quality single crystals. The X-ray structures of 3, 4 and 6
are shown in Fig. 2. Selected bond lengths and angles are given in
Table 1.
Scheme 2 Synthesis of the bis(aryl) gold carbene complexes.
ꢀ
with apparent coupling constants (strictly N = JAX + JAX ) of 6–
6.5 Hz. The 19F NMR spectra show the typical patterns of the
corresponding fluorinated group. Thus, the C6F5 derivatives show
the three resonances expected from that AAꢀMXXꢀ spin system at
ca. −116 ppm (Fortho), −159 ppm (Fmeta) and −163 ppm (Fpara). The
Fmes complexes show two singlets (2 : 1 ratio) at ca. −60 ppm
(ortho-CF3) and −62 ppm (para-CF3). The 19F NMR spectra of
the 4,4ꢀ-octafluorobiphenyl compounds show two multiplets at ca.
−116 ppm and −140 ppm, corresponding respectively to the two
types of F atoms (the ortho to Au and the meta to Au).18
The gold carbene complexes were identified by elemental and
spectroscopic analysis. Their infrared spectra do not show the
m(C≡N) absorption and new bands, which correspond to m(N–H)
−1
and m(C N) in the ranges 3400–3300 cm and 1580–1510 cm−1
=
◦
˚
Table 1 Selected bond lengths (A) and angles ( ) for 3·H2O, 4, and 6
3·H2O
4a 6a
2.045(7)
respectively, can be observed.19
The carbene complexes could present four isomers depending
on the arrangement of the Py and the Rꢀ group, for primary amines
(RꢀNH2), or just two for the secondary amine Et2NH. In all cases
the isomers observed have a syn arrangement of the substituents
Py and Au, which reduces the isomers to one (for Et2NH) or two
(for primary amines), which are shown in Fig. 1.
Au(1)–C(1)
2.053(10)
2.045(9)
1.321(13)
1.329(11)
176.4(4)
116.1(9)
122.1(7)
121.1(7)
112.1(9)
2.029(10)
2.049(10)
1.323(13)
1.348(13)
Au(1)–C(21)
C(1)–N(1)
2.051(8)
1.307(9)
1.353(9)
C(1)–N(2)
C(1)–Au(1)–C(21)
N(2)–C(1)–N(1)
N(1)–C(1)–Au(1)
N(2)–C(1)–Au(1)
C(26)–C(21)–C(22)
174.3(2)
175.3(4)
113.5(9)
120.5(8)
126.0(8)
113.2(9)
116.7(6)
122.7(5)
120.3(5)
114.6(7)
Accordingly the carbenes derived from the Et2NH, [Au(C6F5)-
{C(NEt2)(NHPy-4)}] (3) and [Au(Fmes){C(NEt2)(NHPy-4)}] (4),
1
show only one set of signals in their H NMR spectra at room
temperature and a NOE effect between the carbene hydrogen and
the methylene of one of the ethyl groups (at higher field), allows
the identification of the isomer as the one depicted in Fig. 1(A).
a The asymmetric unit consists of two molecules; significant distances and
angles of one of them are given
5340 | Dalton Trans., 2007, 5339–5345
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Fig. 2 X-Ray structures with 30% ellipsoids (most hydrogens omitted for clarity) of the carbenes 3 (left), 4 (center), and 6 (right).
◦
˚
The single crystals obtained for 3 contained water molecules
affording the composition [Au(C6F5){C(NEt2)(NHPy-4)}]·
H2O. The intermolecular hydrogen bonds in 3·H2O lead to
the formation of a 16-membered supramolecular macrocycle
in the solid state. The two water molecules assemble two
monomeric units of 3, an O–H bond making intermolecular
bridges between the Py and amine N atoms. The supramolecular
macrocycle formed is centrosymmetric. The crystal packing of the
complex shows two intermolecular N–H · · · O–H and O–H · · · N
interactions between two molecules of water and two molecules
of the carbene (Fig. 3).
Table 2 Selected distances (A) and angles ( ) of hydrogen bonds in 3·H2O,
4, and 6
3·H2O
H(3A) · · · N(3B)
H(2A) · · · O(1A)
O(1A)–H(3A) · · · N(3B)
N(2A)–H(2A) · · · O(1A)
N(6) · · · H(2)
2.040(8)
2.052(8)
137.3(7)
151.4(7)
2.019(15)
2.180(10)
149.4(12)
150.3(4)
2.336(12)
4
6
N(3) · · · H(5)
N(6) · · · H(2)–N(2)
N(3) · · · H(5)–N(5)
H(1) · · · N(6)
H(2) · · · N(6)
2.057(12)
2.480(12)
2.054(12)
H(4) · · · N(3)
H(5) · · · N(3)
N(1)–H(1) · · · N(6)
N(2)–H(2) · · · N(6)
N(4)–H(4) · · · N(3)
N(5)–H(5) · · · N(3)
151.3(8)
167.0(8)
145.6(8)
149.0(8)
Confirming the assignment made by NOE experiments, the
conformers found for 3 and 4 have the 4-Py group oriented away
from the ethyl groups of the amine, reducing the steric hindrance
of the molecule.
In 6, the conformer with less hindrance, in which the hydrogen
of the amine ligand is oriented toward the hydrogen of the
carbene group, has been found in the solid state (conformer B),
corresponding to the major isomer observed in solution.
The three complexes show a nearly linear environment for gold.
The Au–C distances are similar to those found for other gold(I)
carbenes,9b,20 and aryl gold(I)21 complexes respectively. The two C–
N distances are similar to those observed for related Au(I) carbene
Fig. 3 Hydrogen bonded molecules of [Au(C6F5){C(NEt2)(NHPy-4)}]·
H2O (3·H2O). Hydrogen bonds are shown as dotted lines.
complexes and shorter than the C(sp2)–N theoretical single bond
In 4, there is a hydrogen bond between the carbene nitrogen of
one molecule and the nitrogen of the Py group of another molecule
in the asymmetric unit. Four molecules of 4 are hydrogen bonded
to build the centrosymmetric supramolecular 24-membered ring
shown in Fig. 4.
The four molecules are conformationally different by pairs, as
they are arranged in a nearly planar macrocycle in which the Py
groups make with the macrocycle average plane a dihedral angle of
53◦ for two molecules and 61◦ for the other two. The macrocycles
are packed in layers and are tilted 63◦ with respect to the vector
perpendicular to the layer.
The structure found for complex 6 is somewhat similar to
that of 4, but the second N–H gets also involved (at a larger
distance) in the hydrogen bonding to the Py nitrogen. In other
words, the nitrogen atoms of Py are asymmetric bifurcated
acceptors of the two N–H donors available in the monomer. Again
the supramolecular tetramer contains also two conformationally
22
˚
distance of 1.45 A, indicating considerable p-bonding between
C and N. As usually observed in fluorinated aryl complexes,
the C–C–C angles at the ipso carbon are significantly less than
120◦ due to electronic effects of the electropositive metal and the
12,24
electronegative F23 or CF3
substituents at the ortho positions.
None of the three crystal structures exhibit aurophilic inter-
actions between the carbene molecules. In fact, the shortest non
˚
˚
bonding Au · · · Au distances are 7.770 A in 3, 6.382 A in 4, and
˚
5.568 A in 6. However, as expected, the three structures display
intermolecular hydrogen bonding. None of the hydrogen atoms
involved in hydrogen bonding were located in the Fourier map
and their positions were calculated with a riding model. A N–H
˚
distance of 1.009 A was imposed, a value that has been observed by
neutron diffraction.25 The N · · · H distances and N · · · H–N angles
are gathered in Table 2. All the interactions observed are within
the range of moderate strength H · · · N hydrogen bonds.26
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The extra weak interaction could help to stabilize the crystal
network. As observed for 4, the supramolecular macrocycle is
nearly planar and there are two different pairs of Py groups making
dihedral angles of 59◦ and 28◦ with the macrocycle average plane.
The macrocycles are arranged in layers with each macrocycle
making an angle of 66◦ with the vector perpendicular to the layer.
Photophysical properties
The absorption and luminescence spectroscopic data of the
gold(I) complexes have been studied. The three parent isocyanide
gold complexes are not luminescent in the solid state, nor in
solution. However, many of the carbenes prepared show intense
luminescence in the solid state and in dichloromethane solution at
room temperature. The data for these are summarized in Table 3.
All electronic spectra are very similar, and show one intense
absorption band at ca. 250 nm in dichloromethane solution.
The wavelengths together with the large extinction coefficients
of 104 M−1 cm−1 are typical, in all cases studied, of ligand-centered
p–p* transitions associated with the aromatic groups.27
In the solid state the pentafluorophenyl gold carbene com-
pounds, 3, 5 and 7, and that of octafluorobiphenyl, 9, exhibit a
yellow-green luminescence visually observed under UV irradiation
at 365 nm, and produce similar emission spectra consisting
of one strong emission band in the range 482–560 nm. In
dichloromethane solution, they show similar luminescence spectra
revealing the intramolecular nature of the emission band observed.
This is consistent with the fact that the single-crystal X-ray
diffraction of 3 demonstrates the absence of Au · · · Au contacts.
The lifetime values28 found in the solid state for 3 appear to be
bi-exponential with long values that support the phosphorescent
nature of the emission process (15 and 429 ls). A similar result
was found in dichloromethane solution with lifetime values of 13
and 597 ls.
Fig. 4 Hydrogen bonded 24-membered macrocycle present in crystalline
[Au(Fmes){C(NEt2)(NHPy-4)}] (4). Hydrogen bonds are shown as dotted
lines.
different molecules of monomer and the tetrameric aggregates are
made of four molecules of 6 (two of each type, in a centrosymmetric
arrangement) bonded through one moderate and one weaker
hydrogen bond (Fig. 5).
In contrast, the fluoromesityl derivatives 4 and 6 are not
luminescent at room temperature neither in the solid state nor
in solution. After freezing a solid sample of 4 at 77 K, a weak
emission band was observed at 430 nm. Although it is not
simple to rationalize this behavior, fluoromesityl complexes can be
regarded as formal derivatives of the pentafluorophenyl complexes
by substitution of a C6F5 by a Fmes group. Considering that C6F5
is more electronegative than Fmes (this is shown by the order
of m(C≡N) frequencies in [Au(aryl)(4-PyNC)] complexes, C6F5 >
Fmes), one might expect any p backbonding contribution from
gold to the metal–carbene bond to be somewhat higher for the
Fmes compounds 4 and 6 compared to the C6F5 complexes 3 and
5, which might provide higher intersystem crossing. According
to that, the loss of the luminescent behavior of Fmes carbenes
could be attributed to the higher probability for intramolecular
Fig. 5 Tetrameric hydrogen bonded rings in crystalline [Au(Fmes)-
{C(NHMe)(NHPy-4)}] (6). Hydrogen bonds are shown as dotted lines.
Table 3 UV-VIS and luminescence data of the carbenes
UV-VIS (CH2Cl2)/nm (e/M−1 cm−1
)
kex (KBr)/nm
kem (KBr)/nm
kex (CH2Cl2)/nm
330
kem (CH2Cl2)/nm
3
4
5
6
7
9
249 (2.04 × 104)
240 (2.08 × 104)
247 (0.62 × 104)
245 (1.09 × 104)
346
333 (77 K)
354
482
430 (77 K)
505
400
481
306, 347
365
356
560
498
258.5 (0.29 × 104), 225.5 (0.30 × 104)
307, 343
520
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radiationless transitions through intersystem crossings with Fmes
compared to C6F5.
m(C≡N), 684 m m(Au–R). 1H NMR (300 MHz): d 8.89 (part A of
a AAꢀXXꢀ system, N 6.1, CNC5H4N, 2H), 8.05 (s, 2H, Fmes), 7.52
(part A of a AAꢀXXꢀ system, N 6.1, CNC5H4N, 2H). 19F NMR
(282.5 MHz): d −60.52 (s, 6 F, ortho-CF3), −63.28 (s, 3 F, para-
CF3). Anal. calcd for C15H6N2F9Au: C, 30.95; H, 1.04; N, 4.81.
Found: C, 30.93; H, 1.04; N, 4.80%.
Conclusions
Carbenes of the type [AuR{C(NR1R2)(NHPy-4)}], easily ob-
tained from reaction of primary or secondary amines with
[AuR(CNPy-4)] adopt preferentially a conformation with the
smallest substituents in the carbene taking syn positions. As a
consequence the anti NHPy-4 fragment is ideally suited to make
intermolecular hydrogen bonds giving tetrameric supramolecular
macrocycles in the solid state. In the presence of water, dimeric
systems are preferred with two water molecules bridging two
[AuR{C(NR1R2)(NHPy-4)}] units. Many of these complexes are
luminescent despite the fact that they lack any aurophilic contacts,
showing that their luminescence has an intramolecular origin.
[Au(C6F5){C(NHPy-4)(NEt2)}] (3). Diethylamine (0.38 mmol,
39.5 lL) was added to a solution of 1 (0.089 g, 0.19 mmol)
in dichloromethane (15 mL). After 15 min stirring at room
temperature the IR of the solution did not show a CN absorption.
The volatiles were pumped off and the white solid was decanted,
washed with hexane (3 × 5 mL) and dried in vacuum yielding
0.074 g (72%). 1H NMR (300 MHz): d 8.59 (m, 2H, NHC5H4N),
7.75 (m, 2H, NHC5H4N), 7.63 (br, 1H, NHC5H4N), 4.21 (q, J 7.2,
4H, N(CH2CH3)2), 3.54 (q, J 7.4, 4H, N(CH2CH3)2), 1.47 (t, J 7.2,
6 H, N(CH2CH3)2), 1.40 (t, J 7.4, 3H, N(CH2CH3)2). 19F NMR
(282.5 MHz): d −116.95 (m, 2 Fortho), −159.92 (t, 1 Fpara), −163.30
(m, 2 Fmeta). Anal. calcd for C16H15N3F5Au: C, 35.50; H, 2.79; N,
7.76. Found: C, 35.65; H, 2.69; N, 7.43%. UV-VIS (CH2Cl2): k
249 nm (e 2.04 × 104 M−1 cm−1). kex (KBr): 346 nm. kem (KBr):
482 nm. kex (CH2Cl2): 330 nm. kem (CH2Cl2): 400 nm.
Experimental
General remarks
All reactions were carried out under dry N2. The solvents were
purified according to standard procedures.29 [Au(C6F5)(tht)],11
[Au(Fmes)(tht)],12 and [Au2(l-C6F4C6F4)(tht)2]13 were prepared
according to literature procedures. 4-PyNC was prepared from 4-
pyridylamine, as described by Ugi et al. for other isocyanides,30
in 20% yield. The rest of the reactants were purchased from
commercial suppliers and used as received. Infrared spectra
from 4000 to 200 cm−1 were recorded in Perkin-Elmer 883 or
1720X apparatus, as Nujol mulls between polystyrene films.
Luminescence spectra were recorded with a Perkin-Elmer LS-55
spectrometer. NMR spectra were recorded with Bruker AC300 or
ARX 300 instruments. 1H, and 19F NMR spectra are referenced to
TMS, and CFCl3 respectively. Elemental analyses were performed
with a Perkin-Elmer 2400B microanalyzer.
[Au(Fmes){C(NHPy-4)(NEt2)}] (4). Diethylamine (0.24 mmol,
25 lL) was added to a solution of 2 (0.070 g, 0.12 mmol)
in dichloromethane (10 mL). After 10 min stirring at room
temperature the IR of the solution did not show a CN absorption.
The volatiles were pumped off and the white solid thus obtained
was decanted, washed with hexane (3 × 5 mL) and dried under
vacuum yielding 0.050 g (68%). 1H NMR: d 8.52 (m, 2H,
NHC5H4N), 7.97 (s, 2H, Fmes), 7.85 (br, 1H, NHC5H4N), 7.60
(m, 2H, NHC5H4N), 4.20 (q, J 7.2, 2H, N(CH2CH3)2), 3.55 (q,
J 7.4, 2H, N(CH2CH3)2), 1.41 (t, J 7,2, 3H, N(CH2CH3)2), 1.39
(t, J 7.4, 3H, N(CH2CH3)2). 19F NMR: d −60.43 (s, 6 F, ortho-
CF3), −63.13 (s, 3 F, para-CF3). Anal. calcd for C19H17N3F9Au:
C, 34.82; H, 2.61; N, 6.41. Found: C, 35.05; H, 2.41; N, 6.19%.
UV-VIS (CH2Cl2): k 240 nm (e 2.08 × 104 M−1 cm−1). kex (KBr, 77
K): 333 nm. kem (KBr, 77 K): 430 nm.
Synthesis
[Au(C6F5)(CNPy-4)] (1). 4-PyNC (0.021 g, 0.2 mmol) was
added to a solution of [Au(C6F5)(tht)] (0.090 g, 0.2 mmol)
in dichloromethane (10 mL). After 15 min stirring at room
temperature the volatiles were pumped off and the white residue
was washed with n-hexane (3 × 5 mL) and crystallized from
dichloromethane–n-hexane. The white solid obtained was de-
canted, washed with n-hexane (3 × 5 mL) and vacuum dried
[Au(C6F5){C(NHPy-4)(NHMe)}]
(5). Methylamine
(0.32 mmol, 28.2 lL, 40% solution in water) was added to
a solution of 1 (0.077 g, 0.16 mmol) in dichloromethane
(15 mL). After 10 min stirring at room temperature a white
solid precipitated. Then the volatiles were pumped off and the
white solid washed with n-hexane (3 × 5 mL) and vacuum dried
1
yielding 0.068 g (83%). H NMR (Me2CO-d6): d 10.02 (br, 1H,
1
yielding 0.074 g (80%). IR: 2222 vs m(C≡N). H NMR: d 8.89
NHC5H4N), 9.65 (br, 1H, NHC5H4N, minor), 9.03 (br, 1H,
NHMe, minor), 8.51 (m, 5H, NHCH3 + NHC5H4N), 7.89 (m,
2H, NHC5H4N), 7.82 (m, 2H, NHC5H4N, minor), 3.50 (d, J
3.8, 3H, NHCH3), 3.12 (d, J 3.5, 3H, NHCH3, minor). 19F
NMR (Me2CO-d6): d −115.2 (m, 2 Fortho), −115.4 (m, 2 Fortho),
−116.9 (t, J 20.1, 2 Fpara), −116.2 (t, J 20.4, 2 Fpara), −163.6
(m, 2 Fmeta), −163.8 (m, 2 Fmeta). Isomers ratio 3 : 2. Anal.
calcd for C13H9N3F5Au: C, 31.28; H, 1.82; N, 8.42. Found: C,
31.15; H, 1.63; N, 8.14%. UV-VIS (CH2Cl2): k nm 247 (e 0.62 ×
104 M−1 cm−1). kex (KBr): 354 nm. kem (KBr): 505 nm. kex (CH2Cl2):
306, 347 nm. kem (CH2Cl2): 481 nm.
(part A of a AAꢀXXꢀ system, N 6.1, NC5H4N, 2H), 7.48 (part X
of a AAꢀXXꢀ system, N 6.1, NC5H4N, 2H). 19F NMR: d − 116.42
(m, 2 Fortho), −157.20 (t, J 20.1, 1 Fpara), −162.55 (m, 2 Fmeta). Anal.
calcd for C12H4N2F5Au: C, 30.79; H, 0.86; N, 5.98. Found: C,
30.88; H, 1.11; N, 5.80%.
[Au(Fmes)(CNPy-4)] (2). A solution of 4-PyNC (0.040 g,
0.38 mmol) in 10 mL of dichloromethane was added to a solution
of [Au(Fmes)(tht)] (0.200 g, 0.35 mmol) in dichloromethane
(15 mL). After 5 min stirring at room temperature the volatiles
were pumped off and the white residue was washed with n-hexane
(3 × 5 mL) and crystallized from dichloromethane–n-hexane. The
colorless crystals obtained were decanted, washed with n-hexane
(3 × 5 mL) and vacuum dried yielding 0.179 g (88%). IR: 2220 s
[Au(Fmes){C(NHPy-4)(NHMe)}]
(6). Methylamine
(0.24 mmol, 21 lL, 40% solution in water) was added to a
solution of 2 (0.070 g, 0.12 mmol) in dichloromethane (20 mL).
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After 10 min stirring at room temperature the IR of the solution
did not show any isocyanide absorption. Then the volatiles were
pumped off and the white residue was washed with n-hexane
(3 × 5 mL) yielding 0.047 g (60%). H NMR: d 9.96 (br, 1H,
−116.09 [m, (C6F4)2, 4 F], −139.00 [m, (C6F4)2, 4 F]. Anal. calcd
for: C24H8N4Au2F8: C, 32.09; H, 0.90; N, 6.24. Found: C, 31.52;
H, 1.13; N, 6.18%.
1
[Au2(l-C6F4C6F4){(C(NHMe)(NHPy-4)}2] (9). Methylamine
(0.21 mmol, 18.2 lL, 40% solution in water) was added to a
solution of 3 (0.090 g, 0.1 mmol) in acetone (50 mL). After 10 min
stirring at room temperature the solution was concentrated and
n-hexane was added. The yellow precipitate thus obtained was
washed with n-hexane (3 × 5 mL) and vacuum dried yielding
0.063 g (66%). 1H NMR (300 MHz, Me2CO-d6): d 10.11 (br,
NHCH3, 2H, minor), 9.68 (br, NHCH3, 2H, major), 9.08 (br,
2-NHC5H4N, 2H, major), 8.52 (m, NHC5H4N, 4H, two isomers),
7.94 (m, NHC5H4N, 4H, major), 7.86 (br, NHC5H4N, 2H, minor),
3.53 (d, J 4, NHCH3, 6H, minor), 3.14 (d, J 4, NHCH3, 6H,
major). 19F NMR (282.5 MHz, Me2CO-d6): d −116.38 (m, (C6F4)2,
4 F, major), −116.46 (m, (C6F4)2, 4 F, minor), −141.27 (m, (C6F4)2,
4 F, two isomers). Anal. calcd for: C26H18N6Au2F8: C, 32.52;
H, 1.89; N, 8.75. Found: C, 32.19; H, 1.77; N, 8.48%. UV-VIS
(CH2Cl2): k 258.5 nm (e 0.29 × 104 M−1 cm−1), 225.5 nm (e 3.00 ×
103 M−1 cm−1). kex (KBr): 356 nm. kem (KBr): 498 nm. kex (CH2Cl2):
307, 343. kem (CH2Cl2): 520 nm.
NHC5H4N), 9.58 (br, 1H, NHC5H4N, minor), 8.80 (br, 1H,
NHCH3, minor), 8.46 (m, 5H, NHCH3 + NHC5H4N, NHC5H4N
two isomers), 8.08 (s, 2H, Fmes), 8.02 (s, 2H, Fmes, minor), 7.84
(m, 2H, NHC5H4N), 7.75 (m, 2H, NHC5H4N minor), 3.49 (d, J
3.9, 3H, NHCH3) 3.12 (d, J 3.7, 3H, NHCH3, minor). Isomers
ratio 3 : 1. 19F NMR (282.5 MHz, Me2CO-d6): d −59.22 (s, 6
F, ortho-CF3), −59.30 (s, 6 F, ortho-CF3, minor), −62.13 (s, 3
F, para-CF3, minor), −62.15 (s, 3 F, para-CF3). Anal. calcd for
C16H11N3AuF9: 31.34; H, 1.81; N, 6.85. Found: C, 31.51; H, 1.64;
N, 6.74%. UV-VIS (CH2Cl2): k 245 nm (e 1.09 × 104M−1 cm−1).
[Au(C6F5 ){C(NHPy-4)(NHC6H4NH)(NHPy-4)C}Au(C6F5 )]
(7). 1,4-Phenylendiamine (0.15 mmol, 1.5 mL, 0.1 M in acetone)
was added to a solution of 1 (0.140 g, 0.3 mmol) in acetone
(100 mL) and stirred for 5 h at room temperature. Then, the
volatiles were removed and the solid was washed with n-hexane
(3 × 5 mL) and dried under vacuum yielding 0.112 g of a pale
yellow solid (64%). Anal. calcd for C30H16N6Au2F10: C, 34.5; H,
1.54; N, 8.05. Found: C, 34.26; H, 1.86; N, 7.23%. kex (KBr):
365 nm. kem (KBr): 560 nm.
X-Ray crystallography
[Au2(l-C6F4C6F4)(4-PyNC)2]
(8). 4-PyNC
(0.052
g,
Suitable single crystals of 3·H2O, 4 and 6 were mounted in glass
fibers, and diffraction measurements were made using a Bruker
SMART CCD area-detector diffractometer with Mo-Ka radiation
0.50 mmol) was added to a solution of [Au2(l-C6F4C6F4)(tht)2]
(0.2165 g, 0.25 mmol) in dichloromethane (40 mL). After 5 min
stirring at room temperature the volatiles were pumped off and
the yellow residue was washed with n-hexane (3 × 10 mL) and
31
˚
(k = 0.71073 A). Intensities were integrated from several series
of exposures, each exposure covering 0.3◦ in x, the total data
set being a hemisphere.32 Absorption corrections were applied,
based on multiple and symmetry-equivalent measurements.33 The
structure was solved by direct methods and refined by least squares
on weighted F2 values for all reflections (see Table 4).34 Complex
1
vacuum dried yielding 0.187 g (83%). IR: 2218 s, m(C≡N). H
NMR (300 MHz, Me2CO-d6): d 8.80 (part A of an AAꢀXXꢀ
system, N 6.1, NHC5H4N, 4H), 7.48 (part B of an AAꢀXXꢀ system,
N 6.1, NHC5H4N, 4H). 19F NMR (282.5 MHz, Me2CO-d6): d
Table 4 Crystal data and structure refinement for 3·H2O, 4, and 6
3·H2O
4
6
Empirical formula
Formula weight
T/K
C16H17AuF5N3O
559.29
298(2)
Triclinic
¯
P1
C19H17AuF9N3
655.32
298(2)
Triclinic
¯
P1
10.714(3)
12.890(4)
19.055(6)
98.662(7)
103.113(6)
105.187(7)
2411.0(12)
4
1.805
6.180
1248
0.40 × 0.09 × 0.03
1.13 to 23.32
11430
C16H11AuF9N3
613.24
298(2)
Triclinic
¯
P1
9.4570(8)
14.2139(13)
15.7496(14)
63.952(2)
89.816(2)
79.969(2)
1866.5(3)
4
2.182
7.975
1152
0.17 × 0.07 × 0.01
1.44 to 23.36
8911
Crystal system
Space group
˚
a/A
9.757(2)
˚
b/A
10.193(2)
11.011(2)
95.063(4)
109.391(4)
115.267(3)
899.6(3)
˚
c/A
a/◦
b/◦
c /◦
3
˚
V/A
Z
2
D
calc/g cm−3
2.065
8.235
532
0.36 × 0.09 × 0.08
2.04 to 23.28
4202
Absorption coefficient/mm−1
F(000)
Crystal size/mm
h range for data collection/◦
Reflections collected
Independent reflections [R(int)]
Absorption correction
Maximum and minimum transmission factor
Data/restraints/parameters
Goodness-of-fit on F2
R1 [I > 2r(I)]
2561 [0.0297]
SADABS
1.000000 and 0.376755
2561/3/244
1.080
0.0299
0.0864
6929 [0.0315]
SADABS
1.000000 and 0.364399
6929/100/677
1.071
0.0413
0.1365
5385 [0.0430]
SADABS
1.000000 and 0.314669
5385/0/525
1.009
0.0390
0.1072
wR2 (all data)
5344 | Dalton Trans., 2007, 5339–5345
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neutral-atom scattering factors were used.35 The molecule of water
14 R. Bayo´n, S. Coco, P. Espinet, C. Ferna´ndez-Mayordomo and J. M.
´
Mart´ın-Alvarez, Inorg. Chem., 1997, 36, 2329–2334.
found in the structure of 3 was refined constraining the distance
15 H. C. Clark and M. H. Chisholm, Inorg. Chem., 1971, 10, 1711–
˚
˚
O–H to be 0.972 A and the distance H · · · H to be 1.542 A.
Two molecules were refined in the asymmetric unit of 4 and both
of them had some groups disordered. In the first molecule the CF3
group in para position was refined with two components, the major
one with a 60% occupancy. In the second molecule the para CF3
group was also disordered having the major component with a 65%
occupancy. An ethyl group of the diethylamino moiety was refined
with three components with 41%, 31% and 28% occupancies,
ISOR, SIMU and DELU restraints had to be applied to avoid
non-positive-definite atoms. The asymmetric unit in 6 also consists
of two molecules but no restraints were applied in the refinement.
All the hydrogen atoms in the three structures, including those
involved in hydrogen bonding, were refined using the riding model.
1716.
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=
19 Although the appearance of previously inexistent m(C N) absorptions
is easily observed, they cannot be assigned unambiguously because
=
other bands due to m(C C) appear in the same region.
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The authors are grateful for financial support by the Direccio´n
General de Investigacio´n (Project CTQ2005-08729/BQU) and
the Junta de Castilla y Leo´n (Project VA099A05). C. Cordovilla
recognises a grant from the MEC.
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©