Mononuclear, dinuclear, and hexanuclear gold(I) complexes with (aza-15-crown-5)dithiocarbamate

Article abstract of DOI:10.1021/ic702252j

The reactions of sodium (aza-15-crown-5)dithiocarbamate with [AuClL] precursors lead to mono-, di-, or hexanuclear derivatives depending on L. The homoleptic hexanuclear gold(I) cluster [Au₆(S₂CNC ₁₀H₂₀O₄)₆] is formed by displacement of the chloride and isocyanide ligands in [AuCl(CN(2,6-Me₂C ₆H3))]. X-ray diffraction studies show a novel geometry in gold cluster chemistry where the six gold atoms display a cyclohexane-like geometry in a chair conformation with Au-Au-Au angles of 117.028(9)°, two short gold-gold distances of 2.9289(5) A, and bidentate bridging dithiocarbamate ligands. The molecular structure shows a crown of gold atoms surrounded by crown ethers. This derivative luminesces at 569 nm at room temperature in the solid state. A dinuclear isomer [AU₂(S₂CNC ₁₀H₂₀O₄)₂] had been reported previously and was obtained by reaction with [AuCl(SMe₂)]. The mechanism to obtain the hexanuclear derivative involves a mononuclear intermediate [Au(S₂CNC₁₀H₂₀O₄)(CNR)] for which the X-ray structure shows a short gold-gold distance of 3.565 A with the two molecules in an anti configuration. Phosphine gold(I) mononuclear derivatives [Au(S₂CNC₁₀H₂₀O₄) (PR₃)] (R = Me, Ph, both characterized by X-ray diffraction) and dinuclear diphosphine derivatives [{Au(S₂CNC₁₀H ₂₀O₄)}₂(μ-P-P)] (P-P = dppm, bis(diphenylphosphinomethane); dppp, 1,3-bis(diphenylphosphinopropane); and dppf, 1,1′-bis(diphenylphosphinoferrocene)) are also reported. In the mononuclear complexes, the molecular structure confirms that the dithiocarbamato ligand is mainly acting as monodentate, with a second longer Au-S distance of 3.197 (PMe₃), 2.944(4) (PPh₃), and 2.968 A (CNR). Three phosphine complexes are emissive at 562 (PMe₃), 528 (PPh ₃), and 605 nm (dppm), at 77 K. X-ray diffraction studies of the dppm derivative show gold-gold intramolecular contacts of 3.0972(9) A (3.2265(10) A for a second independent molecule) and basically monodentate coordination of the dithiocarbamato ligands. All the complexes extract sodium and potassium salts from aqueous solutions. The diphosphine derivatives are noticeably better extractors than the monophosphino derivatives, mainly for potassium salts.

Full text of DOI:10.1021/ic702252j

Inorg. Chem. 2008, 47, 1597-1606
Mononuclear, Dinuclear, and Hexanuclear Gold(I) Complexes with
(aza-15-crown-5)Dithiocarbamate
Javier Arias, Manuel Bardají, and Pablo Espinet*
IU CINQUIMA/Química Inorgánica, Facultad de Ciencias, UniVersidad de Valladolid,
E-47071 Valladolid, Spain
Received November 15, 2007
The reactions of sodium (aza-15-crown-5)dithiocarbamate with [AuClL] precursors lead to mono-, di-, or hexanuclear
derivatives depending on L. The homoleptic hexanuclear gold(I) cluster [Au6(S2CNC10H20O4)6] is formed by
displacement of the chloride and isocyanide ligands in [AuCl(CN(2,6-Me2C6H3))]. X-ray diffraction studies show a
novel geometry in gold cluster chemistry where the six gold atoms display a cyclohexane-like geometry in a chair
conformation with Au-Au-Au angles of 117.028(9)°, two short gold-gold distances of 2.9289(5) Å, and bidentate
bridging dithiocarbamate ligands. The molecular structure shows a crown of gold atoms surrounded by crown
ethers. This derivative luminesces at 569 nm at room temperature in the solid state. A dinuclear isomer
[Au2(S2CNC10H20O4)2] had been reported previously and was obtained by reaction with [AuCl(SMe2)]. The mechanism
to obtain the hexanuclear derivative involves a mononuclear intermediate [Au(S2CNC10H20O4)(CNR)] for which the
X-ray structure shows a short gold-gold distance of 3.565 Å with the two molecules in an anti configuration.
Phosphine gold(I) mononuclear derivatives [Au(S2CNC10H20O4)(PR3)] (R ) Me, Ph, both characterized by X-ray
diffraction) and dinuclear diphosphine derivatives [{Au(S2CNC10H20O4)}2(µ-P-P)] (P-P ) dppm, bis(diphenylphos-
phinomethane); dppp, 1,3-bis(diphenylphosphinopropane); and dppf, 1,1′-bis(diphenylphosphinoferrocene)) are also
reported. In the mononuclear complexes, the molecular structure confirms that the dithiocarbamato ligand is mainly
acting as monodentate, with a second longer Au-S distance of 3.197 (PMe3), 2.944(4) (PPh3), and 2.968 Å
(CNR). Three phosphine complexes are emissive at 562 (PMe3), 528 (PPh3), and 605 nm (dppm), at 77 K. X-ray
diffraction studies of the dppm derivative show gold-gold intramolecular contacts of 3.0972(9) Å (3.2265(10) Å for
a second independent molecule) and basically monodentate coordination of the dithiocarbamato ligands. All the
complexes extract sodium and potassium salts from aqueous solutions. The diphosphine derivatives are noticeably
better extractors than the monophosphino derivatives, mainly for potassium salts.
Introduction
The use of dithiocarbamate and other S ligands in gold
chemistry has been reviewed.5,7 Homoleptic dithiocarbamate
derivatives are dimers with short intramolecular Au···Au
distances, which possess a strong propensity to aggregate to
form chains with short intermolecular Au···Au contacts,8–12
The synthesis of closed-shell polynuclear gold(I) deriva-
tives has attracted considerable attention in recent years
because of the presence of short gold-gold distances, which
have been attributed to correlation effects reinforced by
relativistic effects and electrostatic contributions.1,2 Many
of these derivatives are luminescent in the visible region.3,4
Besides, thiolate gold(I) derivatives have been extensively
studied for their pharmacological applications.5,6
(4) Roundhill, D. M.; Fackler, J. P., Jr. Optoelectronic Properties of
Inorganic Compounds; Plenum Press Ed.: New York and London,
1998; p 195.
(5) Mohamed, A. A.; Abdou, H. E.; Chen, J.; Bruce, A. E.; Bruce,
M. R. M. Comments Inorg. Chem. 2002, 23, 321.
(6) Shaw, C. F., III. Gold: Progress in Chemistry, Biochemistry, and
Technology; Schmidbaur, H., Ed.; John Wiley & Sons: Chichester,
U.K., 1999; p 259.
* Author to whom correspondence should be addressed. E-mail:
espinet@qi.uva.es.
(1) Pyykkö, P. Angew. Chem., Int. Ed. 2004, 43, 4412.
(2) Runeberg, N.; Schütz, M.; Werner, H. J. J. Chem. Phys. 1999, 110,
7210.
(7) Fackler, J. P., Jr.; van Zyl, W. E.; Prohoda, B. Gold: Progress in
Chemistry, Biochemistry, and Technology; Schmidbaur, H., Ed.; John
Wiley & Sons: Chichester, U.K., 1999; p 795.
(3) Schmidbaur, H. Gold Bull. 2000, 33, 3.
(8) Åkeström, S. Ark. Kemi 1959, 14, 387.
10.1021/ic702252j CCC: $40.75
Published on Web 02/01/2008
2008 American Chemical Society
Inorganic Chemistry, Vol. 47, No. 5, 2008 1597

Arias et al.
Scheme 1
and show luminescence that has been attributed to these
contacts.12 The dinuclear gold complex with (aza-15-crown-
5)dithiocarbamate (1) was recently reported and displays
short intramolecular Au···Au distances, but no intermolecular
Au···Au interactions. Consistently, the compound is not
emissive.13 We report here a hexanuclear Au(I) cluster,
luminescent at room temperature, which is an isomer of 1,
and a luminescent intermediate derivative, [Au(S2CN-
crown)(CNR)], from which the hexanuclear isomer is
formed. We also report five mononuclear mono- and diphos-
phine dithiocarbamato gold derivatives, three of which are
luminescent at 77 K.
Complexes 1-7 are air- and moisture-stable, yellow (1-6)
or orange (7) solids at room temperature that were character-
ized by elemental analysis, IR and NMR spectroscopy, and
single-crystal X-ray diffraction for 2-5. The main features
observed in the IR spectra are (a) disappearance of the
Au-Cl and (for 2) the isocyanide vibrations of the starting
material and (b) the presence of typical dithiocarbamate
bands for ν(CdN) around 1480 cm-1 and ν(C-S) around
990 cm-1; the latter is split for the phosphino complexes
3-7, as expected for a mostly monodentate bound ligand.14
The 1H NMR dithiocarbamate resonances are quite insensi-
tive to coordination. The 31P{1H} NMR spectra of complexes
3-7 show a singlet at -6.3, 36.9, 28.9, 29.3, and 30.4 ppm,
respectively. Complex 2 is insoluble in common organic
solvents, which precluded its NMR characterization.
X-Ray Crystal Structure Determination of Compounds
2-5 and 8. Crystal Structure of Complex 2. All the
previously reported homoleptic dithiocarbamato gold(I)
derivatives are dimers with very short intramolecular
gold(I)-gold(I) distances of 2.75–2.80 Å (for instance,
2.7820(5) Å for the (aza-15-crown-5)dithiocarbamate), which
aggregate to form chains with short intermolecular Au···Au
contacts around 3 Å, with the planes of the dimers perpen-
dicularly arranged.8–12 Only the (aza-15-crown-5)dithiocar-
bamate dimer 1 does not form chains, probably because the
formation of C-H···O weak nonclassical hydrogen bridges
between the crown ether unit is incompatible with the
formation of chains.13
Results and Discussion
Synthesis and Characterization. The previously reported
homoleptic dinuclear derivative 1 and the new gold dithio-
carbamate derivatives 2-7 are prepared according to Scheme
1. Compounds 1 and 2 react rapidly with phosphines to give
the same complexes 3 and 4, suggesting that 1 and 2 only
differ in the bridging mode of the dithiocarbamate group.
Similarly, in situ prepared 1 reacts with diphosphines,
affording the dinuclear derivatives with bridging diphos-
phines 5-7. The isolation of crystals of the elusive inter-
mediate 8 is discussed later. (Crystallographic data, in the
form of a CIF file, are provided as Supporting Information.)
(9) Hesse, R.; Jennische, P. Acta Chem. Scand. 1972, 26, 3855.
(10) Heinrich, D. D.; Wang, J. C.; Fackler, J. P. Acta Crystallogr., Sect.
C: Cryst. Struct. Commun. 1990, 46, 1444.
(11) Bishop, P.; Marsh, P.; Brisdon, A. K.; Brisdon, B. J.; Mahon, M. F.
J. Chem. Soc., Dalton Trans. 1998, 675.
(12) Mansour, M. A.; Connick, W. B.; Lachicotte, R. J.; Gysling, H. J.;
Eisenberg, R. J. Am. Chem. Soc. 1998, 120, 1329.
(13) Tzeng, B.-C.; Liu, W.-H.; Liao, J.-H.; Lee, G.-H.; Peng, S.-H. Cryst.
Growth Des. 2004, 4, 573.
The structure of the complex 2, established by X-ray
diffraction, is shown in Figure 1, with selected bond lengths
and angles in Table 1. The molecule turns out to be an isomer
(14) Bonati, F.; Ugo, R. J. Organomet. Chem. 1967, 10, 257.
1598 Inorganic Chemistry, Vol. 47, No. 5, 2008

Gold(I) Complexes with (aza-15-crown-5)Dithiocarbamate
Figure 1. Two different views of 2. Displacement ellipsoids are at the 50% (left) or 20% (right) probability level (H atoms omitted for clarity).
Table 1. Selected Bond Lengths [Å] and Angles [deg] for Complex 2a
clusters should be planar.1,17,18 In agreement with this
prediction, in the reported structure for [Au6(S2CC6H4(o-
CH3))6],19 which also has a zigzag system of bridging
dithiocarboxylates, the six gold atoms of the central cluster
are coplanar to within 0.14 Å. Thus, the chairlike structure
observed for 2 is exceptional. A more detailed observation
of the tridimensional molecular packing of 2 in the crystal
gives hints for the origin of the chairlike arrangement of the
gold cluster, as well as for the insolubility of the compound.
As shown in Figure 1, the hexagold cluster is sandwiched
between crown-ether layers, and the three crown ether rings
above and below the gold cluster are disposed as the blades
of a fan. It is this arrangement which pushes the sulfur atoms
and, with them, the gold atoms away from coplanarity,
overcoming the expected tendency to a planar arrangement
of six gold atoms.
The folded arrangement of crown ethers has its origin in
the formation of a tridimensional packing that allows for a
closer intermolecular approximation of crown ethers in
successive layers along the c axis (each molecule is
sandwiched by two identical molecules), as well as in the
same layer (each molecule is surrounded by six identical
molecules) (Figure 2). The disorder of some crown ether
atoms in the X-ray structure, and the non-observation of the
corresponding H atoms, precludes an exact determination
of all distances, but it can be calculated that there is a
multitude of C···O distances shorter than 3.5 Å,20 which could
correspond to so-called C-H···O weak nonclassical hydrogen-
bonding interactions. It is this extended network of interac-
tions that would account for the insolubility of 2. The
Au(1)-S(2A)
Au(1)-S(1)
Au(1)-Au(1A)
Au(1)-Au(1B)
S(1)-C(1)
2.286(3)
2.291(3)
S(2A)-Au(1)-S(1)
S(2A)-Au(1)-Au(1A)
S(1)-Au(1)-Au(1A)
S(2A)-Au(1)-Au(1B)
S(1)-Au(1)-Au(1B)
Au(1A)-Au(1)-Au(1B)
C(1)-S(1)-Au(1)
N(1)-C(1)-S(2)
170.53(10)
87.44(7)
96.69(7)
97.69 (8)
88.05(7)
117.028(9)
110.4(3)
116.8(7)
117.9(7)
125.4(6)
122.8(8)
121.8(8)
2.9289(5)
2.9289(5)
1.729(9)
1.720(10)
1.320(11)
1.478(12)
1.602(15)
1.488(14)
1.382(13)
1.349(14)
S(2)-C(1)
C(1)-N(1)
N(1)-C(2)
N(1)-C(11)
C(2)-C(3)
C(3)-O(1)
O(1)-C(4)
N(1)-C(1)-S(1)
S(2)-C(1)-S(1)
C(1)-N(1)-C(2)
C(1)-N(1)-C(11)
a Symmetry transformations used to generate equivalent atoms. A: y -
1/3, -x + y + 1/3, -z + 7/3. B: x - y + 2/3, x + 1/3, -z + 7/3.
of the reported dinuclear complex 1.13 It is a hexanuclear
complex with the six gold atoms arranged in a perfect
chairlike conformation (Figure 1), held together by a zigzag
system of bridging dithiocarbamates. The S(2A)-Au(1)-S(1)
angle is 170.53(10)° and corresponds to a slightly distorted
linear geometry for the gold atom. The hexagold core
displays Au-Au-Au angles of 117.028(9)°, and each gold
is connected to two neighbors at short gold-gold distances
of 2.9289(5) Å. The next gold neighbors in the hexagold
core are at a distance of 4.995 Å, and the farthest one is at
5.791 Å. The shortest intermolecular gold-gold distance is
9.157 Å.
Gold displays a rich cluster chemistry often involving
AuER3+ units (E ) P and As). The typical arrangement for
Au6 clusters is that of dimers of trinuclear derivatives, as in
[{X(AuER3)3}2]n+ (n ) 2, X ) O, S, Se, and Te; n ) 0, X
) N).15 A trigonal prismatic arrangement of six gold atoms
formed by gold-gold interactions between two gold triangles
(n ) 3 × 2) is also the structure of [Au{2-PyNd
C(NH)Me}]n.16 To our knowledge, complex 2 is the first
example of cyclohexane-like geometry in gold cluster
chemistry. Recent theoretical studies predicted, for ligandless
systems, that the lowest energy isomer for hexanuclear gold
(17) Olson, R. M.; Varganov, S.; Gordon, M. S.; Metiu, H.; Chretien, S.;
Piecuch, P.; Kowalski, K.; Kucharski, S. A.; Musial, M. J. Am. Chem.
Soc. 2005, 127, 1049.
(18) Bravo-Pérez, G.; Garzón, I. L.; Novaro, O. THEOCHEM 1999, 493,
225.
(19) Schuerman, J. A.; Fronczek, F. R.; Selbin, J. J. Am. Chem. Soc. 1986,
108, 336.
(15) Gimeno, M. C.; Laguna, A. SilVer and Gold in ComprehensiVe
Coordination Chemistry II; McCleverty, J. A., Meyer, T. J., Fenton,
D. E., Eds.; Elsevier Pergamon: Oxford, U.K., 2004; Vol. 6, p 911.
(16) Bartolomé, C.; Carrasco-Rando, M.; Coco, S.; Cordovilla, C.; Espinet,
P.; Martín-Álvarez, J. M. Organometallics 2006, 25, 2700.
(20) Several C···O intermolecular distances in the range 3.3–3.5 Å, for each
crown ether moiety, are found. In addition, there is a posible weak
C3-H3A···S2 intermolecular contact (six per hexamer) connecting
columns in the xy plane: 2.873 Å (H3A···S2) and 3.677 Å (C3-S2)
and a C3H3AS2 angle of 140.80.
Inorganic Chemistry, Vol. 47, No. 5, 2008 1599

Arias et al.
Table 3. Selected Bond Lengths [Å] and Angles [deg] for Complex 4
Au(1)-P(1)
Au(1)-S(1)
S(1)-C(1)
S(2)-C(1)
C(1)-N(1)
N(1)-C(2)
N(1)-C(11)
C(2)-C(3)
2.253(3)
2.339(3)
1.745(10)
1.696(11)
1.337(13)
1.450(14)
1.480(14)
1.50(2)
P(1)-Au(1)-S(1)
S(2)-Au(1)-S(1)
C(21)-P(1)-Au(1)
C(1)-S(1)-Au(1)
N(1)-C(1)-S(2)
N(1)-C(1)-S(1)
S(1)-C(1)-S(2)
C(1)-N(1)-C(2)
172.80(8)
66.91(10)
111.0(3)
96.7(4)
124.0(7)
117.6(8)
118.3(6)
123.0(9)
The gold atoms display in both complexes a slightly
distorted linear geometry, with a P(1)-Au(1)-S(1) angle
of 170.33(8)° for 3 and 172.80(8)° for 4. The Au-P distance
is 2.247(2) Å for 3 and 2.253(3) Å for 4, close to others
reported for this kind of derivative. The Au(1)-S(1) distance
is 2.332(2) Å for 3 and 2.339(3) Å for 4, slightly shorter
than that in complex 2. In complex 3, the Au(1)-S(2)
distance is 3.197 Å, while complex 4 displays a significantly
different Au(1)-S(2) distance of 2.944(4) Å. Consistently,
the dithiocarbamate ligand shows two different C-S bond
lengths: one shorter at 1.696(8) Å (1.696(11) for 4) for the
dangling sulfur atom and one slightly longer at 1.751(8) Å
(1.745(10) for 4) for the coordinated one. The very dissimilar
Au-S distances support the ditiocarbamate ligands being
essentially monodentate, although the value of the longer
distances suggests a weak contact between the gold atom
and the dangling sulfur atom, as reported, for instance, for
[Au(S2CNEt2)(PPh3)] with Au-S bond distances of 2.338
and 3.015 Å.21 This possible weak interaction looks more
plausible for 4, which has more acceptor phosphine and
shows a noticeably shorter Au(1)-S(2) distance.
Figure 2. Crystal packing containing three layers, almost down the c axis.
Displacement ellipsoids are at the 50% probability level.
Crystal Structure of Complex 5. Complex 5 crystallizes
with two independent but rather similar molecules in the
asymmetric unit. One molecule is shown in Figure 4, and a
selection of bond lengths and angles is given in Table 4.
The P-Au-S angles (ranging from 168.89(11) to
176.31(10)°) confirm a linear geometry around the gold
atoms, although slightly distorted for Au(2), Au(3), and
Au(4). The main difference between the two independent
molecules is the intramolecular Au-Au distance, 3.0972(9)
Å for Au(1)-Au(2) and 3.2265(10) Å for Au(3)-Au(4),
Figure 3. Structures of 3 (up) and 4 (down), showing displacement
ellipsoids at the 50% probability level (H atoms and crystallization CH2Cl2
for 3 omitted for clarity).
Table 2. Selected Bond Lengths [Å] and Angles [deg] for Complex 3
Au(1)-P(1)
Au(1)-S(1)
S(1)-C(1)
C(1)-N(1)
C(1)-S(2)
N(1)-C(2)
N(1)-C(11)
C(2)-C(3)
2.247(2)
2.332(2)
1.751(8)
1.321(10)
1.696(8)
1.472(11)
1.479(11)
1.516(11)
P(1)-Au(1)-S(1)
C(12)-P(1)-C(13)
C(13)-P(1)-Au(1)
C(14)-P(1)-Au(1)
C(1)-S(1)-Au(1)
N(1)-C(1)-S(2)
N(1)-C(1)-S(1)
S(2)-C(1)-S(1)
170.33(8)
104.4(5)
113.6(4)
116.6(3)
102.5(3)
123.2(6)
117.3(6)
119.5(4)
hexagonal tunnels apparently suggested by Figure 2 are
somewhat deceptive, as the distances between the nonplanar
crown ether rings are far too long (around 8 Å).
Crystal Structures of Complexes 3 and 4. The mono-
nuclear structures of 3 and 4 were confirmed by X-ray
diffraction studies and are shown in Figure 3. A selection
of bond lengths and angles is given in Tables 2 and 3. The
nonbonding shortest intermolecular Au/Au distances are
6.379 and 7.654 Å, for derivatives 3 and 4, respectively.
Figure 4. One of the two independent molecules of complex 5 in the crystal,
showing displacement ellipsoids at the 50% probability level (H atoms
omitted for clarity).
1600 Inorganic Chemistry, Vol. 47, No. 5, 2008

Gold(I) Complexes with (aza-15-crown-5)Dithiocarbamate
Table 4. Selected Bond Lengths [Å] and Angles [deg] for Complex 5
Au(1)-P(1)
Au(1)-S(1)
Au(1)-Au(2)
Au(2)-P(2)
Au(2)-S(3)
S(1)-C(1)
2.250(3)
2.322(3)
3.0972(9) Au(3)-Au(4)
2.247(3)
2.335(3)
1.758(11) S(5)-C(70)
1.662(13) S(6)-C(70)
1.324(12) C(70)-N(3)
1.743(11) S(7)-C(71)
1.669(13) S(8)-C(71)
1.348(15) C(71)-N(4)
1.459(16) N(4)-C(83)
Au(3)-P(3)
Au(3)-S(5)
2.254(3)
2.334(4)
3.2265(10)
2.256(4)
Au(4)-P(4)
Au(4)-S(7)
2.329(4)
1.735(12)
1.690(14)
1.335(15)
1.712(13)
1.665(15)
1.358(17)
1.501(16)
173.49(12)
88.04(8)
S(2)-C(1)
C(1)-N(1)
S(3)-C(2)
S(4)-C(2)
C(2)-N(2)
N(2)-C(23)
P(1)-Au(1)-S(1)
P(1)-Au(1)-Au(2)
176.31(10)
82.37(7)
P(3)-Au(3)-S(5)
P(3)-Au(3)-Au(4)
S(5)-Au(3)-Au(4)
P(4)-Au(4)-S(7)
P(4)-Au(4)-Au(3)
S(7)-Au(4)-Au(3)
N(3)-C(70)-S(6)
N(3)-C(70)-S(5)
S(6)-C(70)-S(5)
N(4)-C(71)-S(8)
N(4)-C(71)-S(7)
S(8)-C(71)-S(7)
S(1)-Au(1)-Au(2) 101.29(8)
94.83(8)
170.10(12)
83.48(8)
P(2)-Au(2)-S(3)
P(2)-Au(2)-Au(1)
S(3)-Au(2)-Au(1)
N(1)-C(1)-S(2)
N(1)-C(1)-S(1)
S(2)-C(1)-S(1)
N(2)-C(2)-S(4)
N(2)-C(2)-S(3)
S(4)-C(2)-S(3)
168.89(11)
93.00(7)
86.03(8)
122.3(8)
116.5(9)
121.1(7)
121.9(9)
117.7(9)
120.4(7)
87.13(9)
121.1(10)
118.5(10)
120.4(8)
122.6(10)
115.7(11)
121.7(9)
Figure 5. (Top) Structure of complex 8, showing displacement ellipsoids
at the 50% probability level (H atoms omitted for clarity). (Bottom) Dimer
formed by short gold-gold intermolecular interactions.
which in both cases indicates metal-metal interaction. The
diphosphine adopts a cis conformation, with torsion angles
Au(1)-P(1)····P(2)-Au(2) ) -20.8° and Au(3)-P(3)····
P(4)-Au(4) ) 24.5° that show that the two P-Au-S
moieties in each molecule are slightly twisted with respect
to each other. The cis conformation is usually preferred to
the trans conformation as a result of the formation of Au-Au
interactions. Only with bulky ligands such as 2,4,6-tris(tri-
fluoromethyl)phenyl has the trans conformation been ob-
served, with an intramolecular Au-Au distance of 7.041 Å.22
There are no short gold-gold intermolecular contacts, and
the shortest Au/Au intermolecular distance is 6.544 Å. The
Au-P bond distances (2.247(3)-2.254(3)) are typical for
this type of complex, as found also for 3 and 4. The Au-S
bond distances are similar (from 2.322(3) to 2.335(3)),
comparable to those found in 3 and 4, and slightly shorter
than in complex 2. The dithiocarbamate ligands are es-
sentially monodentate, with Au-S distances of 3.135, 3.022,
3.075, and 3.265 Å respectively for each gold center and
the corresponding second sulfur atom. As observed also for
derivatives 3 and 4, there are two slightly different C-S bond
lengths (one shorter at 1.662(13)-1.690(14) Å and one
longer at 1.712(13)-1.758(11) Å) and one short C-N bond
length (1.324(12)-1.358(17) Å).
Table 5. Selected Bond Lengths [Å] and Angles [deg] for Complex 8
Au(1)-S(1)
Au(1)-C(1)
C(1)-N(1)
N(1)-C(2)
S(1)-C(10)
S(2)-C(10)
C(10)-N(2)
N(2)-C(11)
2.352(4)
C(1)-Au(1)-S(1)
N(1)-C(1)-Au(1)
C(1)-N(1)-C(2)
C(10)-S(1)-Au(1)
N(2)-C(10)-S(2)
N(2)-C(10)-S(1)
S(2)-C(10)-S(1)
C(10)-N(2)-C(11)
161.0(5)
172.3(14)
168.2(15)
96.8(5)
123.5(12)
117.6(12)
118.8(8)
120.2(13)
1.936(15)
1.136(17)
1.412(17)
1.740(16)
1.672(16)
1.343(17)
1.490(19)
from linear than for the previous derivatives (168.89(11)-
176.31(10)°). The Au(1)-S(1) distance is longer than in
complex 2 but similar to those found in derivatives 3–5.
Moreover, it displays a Au(1)-S(2) distance of 2.968 Å,
close to that observed for the derivative with PPh3. This again
suggests that the dithiocarbamate ligand is essentially mono-
dentate, but some weak S···Au interaction is not discarded.
The Au(1)-C(1) and C(1)-N(1) distances are normal.23
Factors Controlling the Nuclearity of the Products. It
is interesting to analyze why the chemical system constituted
by a gold(I) center, a neutral ligand, and an (aza-15-crown-
5)dithiocarbamate anion can give rise to three different
results: a homoleptic dimer (1), a homoleptic hexanuclear
compound (2), and heteroleptic mononuclear complexes (3
and 4). The dinuclear isomer, 1, was obtained by displace-
ment of a thioether (SMe2,13 or tht) from a putative
intermediate A formed in situ by metathesis with the sodium
salt of (aza-15-crown-5)dithiocarbamate (Scheme 2). The
formation of 1 versus A is favored for a number of reasons:
The overall increase in entropy, the gain in S-C-S
resonance, and the volatility of the free thioether, which can
be total or partially pumped off during evaporation of the
solvent. In contrast, ligands with a higher Au-L bond
energy, such as phosphines, maintain the monomeric struc-
ture A.
Crystal Structure of [Au(S2CNC10H20O4)(CN(2,6-
Me2C6H3))] (8). Although with higher than usual error, due
to the low quality of the crystals, the structure of 8 was
established by X-ray diffraction and is shown in Figure 5,
with selected bond lengths and angles in Table 5. The
molecule crystallizes forming pairs with a second identical
molecule in an anti configuration, at a short Au···Au distance
of 3.565 Å. Each gold atom has three other neighbor gold
atoms at ca. 7.50 Å. The C(1)-Au(1)-S(1) angle of
161.0(5)° corresponds to a gold coordination more distorted
The reasons leading to the hexanuclear derivative 2 are
less obvious. In fact, the isomerization of 1 to 2 is
(21) Wijnhoven, J. G.; Bosman, W. J. P. H.; Beursken, P. T. J. Cryst. Mol.
Struct. 1972, 2, 7.
(22) Bardají, M.; Jones, P. G; Laguna, A.; Moracho, A.; Fischer, A. K. J.
Organomet. Chem. 2002, 648, 1.
(23) Coco, S.; Cordovilla, C.; Espinet, P.; Martín-Álvarez, J. M.; Muñoz,
P. Inorg. Chem. 2006, 45, 10180.
Inorganic Chemistry, Vol. 47, No. 5, 2008 1601

Arias et al.
Scheme 2
(identified by X-ray diffraction). However, some crystals of
8 could be obtained from these solutions (mixed with crystals
of 2) when a large excess of isocyanide was added to prevent
extensive crystallization of 2 (see Experimental Section). The
crystals of 8 could be picked up from the mixture, and this
made the unambiguous identification of 8 possible.
Assuming that integration of ν(Ct N) in solution is a
reasonable measure of concentration, the equilibrium constant
in Scheme 3 is Keq ) 2[CNcoord]2/[CNfree]3 ) 2.7 × 104 M-1.
This approximate value affords concentrations of CNcoord and
CNfree in the NMR solution at the same order of magnitude
(e.g., 9 × 10-2 M in CNR gives 91% coordinated CNR),
which should make the NMR of 8 observable. However, as
the 1H chemical shifts of the signal of the isocyanide hardly
move from free to coordinated, the 1H NMR spectra results
are uninformative in detecting this reaction. Hexanuclear 2
can be equally prepared using other isocyanides. It was also
formed when a solution of derivative 4 was left to evaporate
slowly (several months). This led to a yellow powder
containing 4, triphenylphosphine oxide (by 31P NMR), and
yellow microcrystals of 2 (by X-ray diffraction) as shown
in Scheme 3.
Scheme 3
Complex 2 is insoluble once it is formed and does not
dissolve to revert to 1 with thioethers, but it is solubilized
in the presence of PPh3 to give 4 or, slowly, in the presence
of a large excess of CNR (R ) 2,6-Me2C6H3NC), to give
the equilibrium of 2 and 8 discussed above.
In order to asses whether this reaction depends on the
specific features of the crown dithiocarbamate, the reaction
of [AuCl(CNR)] with other dithiocarbamates that are known
to give well-characterized dinuclear derivatives was studied,
affording only the corresponding dinuclear complex
[Au2(S2CNR′2)2] (R′ ) Et, n-pentyl).26,12 This confirms that
the presence of the crown ether is critical for the formation
of 2.
In view of all these results, the following observations
seem to be apparent: (i) The formation of 1 is favored by
the use of weak ligands (thioethers) because these are totally
dissociated in solution, and the equilibrium mononuclear/1
is totally displaced toward 1 at any concentration of the
solution. Since this will not change noticeably upon evapora-
tion (except favoring the displacement toward 1, if the ligand
is volatile), the only species virtually existing in the solution,
1, will crystallize when its solubility limit is reached. (ii)
Strong ligands (such as PPh3), keeping the dissociation
equilibrium totally displaced toward the monomer at any
concentration (e.g., ratio 4/1 very high at all concentrations),
will prevent the formation of any significant concentration
of 1 or 2, and the monomer will crystallize. (iii) Ligands of
moderate strength (CNR) produce 1, free CNR, and 8 in
equilibrium, with not very disparate concentrations of each
of them. Because of the mathematical expression of the
dissociation constant, as the overall concentration in total
gold of the solution increases, the equilibrium is less and
less displaced toward 1, preventing early saturation in 1. The
solubility of 2 being extremely low and the solubilities of 8
entropically disfavored, and experimentally, 1 in solution
does not isomerize to 2. Complex 2 was first obtained
serendipitously according to Scheme 1, while trying to
prepare the monomeric derivative 8. It is known that chloro
isocyanide complexes are easily obtained by ligand displace-
ment from the corresponding tht precursors;24 therefore,
isocyanides are much better ligands for gold(I) than tht. The
question is then: why and when is 2 formed, and not 1 or 8?
The reaction of [AuClCNR] with sodium (aza-15-crown-
5)dithiocarbamate was monitored by IR spectroscopy. The
starting material, [AuClCNR], showed a ν(Ct N) band at
2214 cm-1. Five minutes after adding the dithiocarbamate
salt, two bands were observed at 2122 (free isocyanide) and
2197 cm-1. The latter band is assigned to [Au(S2CN-
crown)(CNR)] 8, and therefore we propose (Scheme 3) an
equilibrium in solution of 8 and 1 (soluble), plus free
isocyanide, plus 2 in unobservable concentration (it is
practically insoluble).25 Crystallization of this mixture af-
forded yellow microcrystals of the insoluble pure complex
2 in good yield, which points to a shift of the equilibrium
due to the crystallization of 2 when the solubility limit of 2
(very low) is reached before those of 1 or 8 (comparatively
high).
The reaction of 1 with isocyanide, monitored by IR
spectroscopy, afforded the same equilibrium mixture, from
which microcrystals of derivative 2 were also obtained
(24) Benouzzane, M.; Coco, S.; Espinet, P.; Martín-Álvarez, J. M. J. Mater.
Chem. 1995, 5, 441.
(25) A similar equilibrium does not operate for [AuClCNR)], which does
not dissociate isocyanide. This shows that the ligand (crownNCS2)-
labilizes the bond of the isocyanide to Au(I). Probably some weak
interaction of the appended sulfur with gold (in a three-coordinated
complex) helps this labilization.
(26) Hong, M.-C.; Lei, X.-J.; Huang, Z.-Y. Chin. Sci. Bull. 1993, 38, 912.
1602 Inorganic Chemistry, Vol. 47, No. 5, 2008

Gold(I) Complexes with (aza-15-crown-5)Dithiocarbamate
Figure 6. Excitation and emission spectra at 77 K in the solid state: (a) complex 2 and (b) complex 4.
Table 6. Excitation and Emission Data for 1-5 and 8 in the Solid
and it was found that it emits at wavenumbers very close to
those of 2. The spectra of 3 at 77 K are quite similar to
those of 1 and 2, while those of 4 are clearly blue-shifted,
and the emission spectrum of 5 is red-shifted. The spectra
of derivative 8 are very close to those of 1-3.
State
298 K
exc/nm
77 K
exc/nm
complex
λ
λemis/nm
λ
λemis/nm
1
2
3
4
5
355sh, 413, 447a
353sh, 412, 447,a 469
346sh, 411, 438, 451a
357, 423a
570
566
562
528
605
563
475,a 491
569
The emission observed in gold(I) thiolate complexes has
been assigned as a S(π) to Au(6p) ligand-to-metal charge
transfer (LMCT). The presence of Au···Au interactions
strongly influences the emission bands, which become
LMMCT in nature,4,27 although multiple state emissions
(MC, LMCT, and LMMCT) have been proposed to explain
the spectral behavior of dialkyldithiophosphonate dinuclear
derivatives.28 The presence of Au···Au interactions in 1 and
2 does not change the emission wavelength, although for
complex 2, it facilitates the emission (it is the only product
to emit at room temperature). Moreover, the emission
maxima are quite similar to those observed for derivatives
3 and 8. Therefore, the emission measured for complexes
1-3 and 8 can be assigned to LMCT transitions. The
emission of 4 can also be assigned as LMCT transitions
mixed with a LLCT transition due to the presence of the
phenyl rings in the ligands, as reported for other derivatives.29
The red shift found for 5 is typically observed when going
from a LMCT to a LMMCT transition.
Extraction Experiments. Except for the insoluble com-
pound 2, measurements were carried out on the extraction
efficiency of sodium picrate from aqueous solutions by
solutions of compounds 3-7 in dichloromethane (Table 7;
see also Experimental Section). The results show that the
three diphosphino complexes are clearly better and faster
extractors than the two monophosphino derivatives. Looking
at the X-ray structure of 5, where the crown ethers are
brought close in the space by the Au···Au bond, these results
strongly suggest that the two crown ethers in 5-7 are
cooperating to bind the cation in a chelating way, although
probably not involving all the oxygen atoms of each crown.
In other words, in a way very similar to the well-known
chelate and macrocyclic effects, the coordination process of
442
8
350, 414, 424,a 431
a
Most intense peak.
Table 7. Extraction Efficiency of Derivatives 3-7
,
extractor
% extracteda b
% extracted (time)
3
4
5
6
25
69
76
78
73
45c
84c
41 (80 min)
79 (80 min)
99 (30 min)
94 (45 min)
96 (15 min)
50c (80 min)
96c (15 min)
7
4c
7c
a Measured after 5 min. b Calculated as follows: (Ao - A)/Ao × 100; Ao
c
) starting absorbance; A ) final absorbance. Data for potasium picrate
(extractor concentration is half that of the sodium picrate experiments).
and 1 higher, and having shown that CNR is not so efficient
at dissolving 2, it is perfectly possible for the unobserved in
solution 2 to be the first to become saturated and, therefore,
the first that crystallizes. Only a high excess of CNR
prevents, in part, this preference and leads to conditions
where 8 and 2 crystallize together. (iV) Finally, starting from
a concentrated solution of a complex with a strong ligand
(e.g., 4, with L ) PPh3), if the strong ligand is slowly
removed (e.g., by oxidation to give a weak ligand OPPh3
unable to dissolve 2), crystallization of the insoluble 2 at
that high concentration of total gold is favored, as observed.
Photophysical Studies. The solid-state emission and
excitation spectra of the isolated complexes were determined
at 298 and 77 K. The results are summarized in Table 6,
and the spectra of complexes 2 and 4 are shown in Figure
6. Neither the dithiocarbamate ligand nor derivatives 6 and
7 emit. Complex 2 shows a weak emission at 298 K (in
contrast with the reported non-emissive character of 1 at
room temperature),13 and an intense photoluminescence at
77 K. The emission maximum at ca. 565 nm does not change
with the temperature, while the excitation maxima are blue-
shifted upon lowering the temperature. For comparison, the
emission spectra of 1 were measured at low temperatures,
(27) Mohamed, A. A.; Kani, I.; Ramirez, A. O.; Fackler, J. P., Jr. Inorg.
Chem. 2004, 43, 3833.
(28) Lee, Y. A.; McGarrah, J. E.; Lachicotte, R. J.; Eisenberg, R. J. Am.
Chem. Soc. 2002, 124, 10662.
(29) Bardají, M.; Calhorda, M. J.; Costa, P. J.; Jones, P. G.; Laguna, A.;
Pérez, M. R.; Villacampa, M. D. Inorg. Chem. 2006, 45, 1059.
Inorganic Chemistry, Vol. 47, No. 5, 2008 1603

Arias et al.
1604 Inorganic Chemistry, Vol. 47, No. 5, 2008

Gold(I) Complexes with (aza-15-crown-5)Dithiocarbamate
3
(t, 4H, JHH ) 6.1 Hz, OCH2CH2N), 4.17 (d, 4H, OCH2CH2N),
the three diphosphine complexes benefits from a lower
unfavorable entropy contribution, because these gold com-
plexes have the crown ethers prearranged for chelation. This
effect is even sharper when the experiment is carried out
with potassium picrate because, as expected, this cation will
be more effectively extracted as a sandwich by 15-crown
ethers. Actually, the dinuclear derivative 7 extracts K+ better
and faster than the mononuclear derivative 4, and the
difference is bigger than that for Na+.
7.39–7.63 (m, 15H, Ph). 31P{1H} NMR: δ 36.86 (s). IR (KBr):
1479 ν(CdN), 998, 987 ν(C-S) cm-1
. Anal. calcd for
C29H35AuNO4PS2: C, 46.22; H, 4.68; N, 1.86. Found: C, 45.83; H,
4.34; N, 2.05.
Preparation of [(µ-P-P){Au(S2CNC10H20O4)}2] (P-P ) dppm,
5; dppp, 6; dppf, 7). To a dichloromethane solution (20 mL) of
[AuCl(tht)]33 (64 mg, 0.2 mmol) was added Na(S2CNC10H20O4)
(64 mg, 0.2 mmol). The yellow solution was stirred for about 1 h
and filtered through kieselgur. Then, the bisphosphine was added
(0.1 mmol; P-P ) 38.5 mg dppm, 41 mg dppp, 57 mg dppf). The
solution was stirred for about 30 min, and the solvent was
evaporated. The residue was washed with diethyl ether (3 × 5 mL)
to afford the corresponding complexes as yellow (5 and 6) or orange
Experimental Section
General. All reactions were carried out under a N2 atmosphere
at room temperature. Spectroscopic and analytical data were
obtained as reported elsewhere.30
1
(7) solids. Yield of 5: 112 mg, 82%. H NMR: δ 3.65 (s, 26H,
OCH2CH2O and PCH2P), 3.97 (t, 8H, 3JHH ) 5.7 Hz, OCH2CH2N),
4.20 (brs, 8H, OCH2CH2N), 7.24–7.74 (m, 20H, Ph). 31P{1H} NMR:
δ 28.9 (s). IR (KBr): 1467 ν(CdN), 998, 989 ν(C-S) cm-1. Anal.
calcd for C47H62Au2N2O8P2S4: C, 41.29; H, 4.57; N, 2.05. Found:
Extraction Experiments. To a dichloromethane solution (10
mL) of the extracting gold compound (10-3 M in crown ether; 5
× 10-4 M in crown ether for the potasium experiments) was added
an aqueous solution of sodium picrate (10 mL, 5 × 10-5 M)
prepared in situ by mixing solutions of picric acid and sodium
hydroxide. The mixture was vigorously stirred, and samples were
taken every 5 min to monitor the diminution of sodium picrate
concentration in the aqueous phase by UV–vis spectrophotometry
(λ ) 356 nm), until successive determinations showed no
variation. This was taken as an indication that equilibrium had
been reached.
Preparation of [Au6(S2CNC10H20O4)6] (2). To a dichloro-
methane solution (10 mL) of [AuCl(CNR)] (R ) 2,6-Me2C6H3; 73
mg, 0.2 mmol)24 was added Na(S2CNC10H20O4) (63 mg, 0.2
mmol).31 The solid dissolved rapidly. The resulting yellow solution
was stirred for about 15 min and then filtered through kieselgur.
Yellow crystals were obtained by slow diffusion of hexane into
the dichloromethane solution, after standing at -18 °C. Yield of
2: 64 mg, 65%. IR (KBr): 1483 ν(CdN), 991 ν(C-S) cm-1. Anal.
calcd for C66H120Au6N6O24S12: C, 26.89; H, 4.1; N, 2.85. Found:
C, 26.84; H, 3.8; N, 2.82.
1
C, 41.69; H, 4.3; N, 2.14. Yield of 6: 68 mg, 50%. H NMR: δ
2.10 (m, 2H, PCH2CH2CH2P), 2.88 (m, 4H, PCH2CH2CH2P), 3.66
(s, 24H, OCH2CH2O), 3.97 (t, 8H, JHH ) 6.15 Hz, OCH2CH2N),
3
3
4.19 (t, 8H, JHH ) 6.15 Hz, OCH2CH2N), 7.40–7.83 (m, 20H,
Ph). 31P{1H} NMR: δ 29.3 (s). IR (KBr): 1467 ν(CdN), 998, 987
ν(C-S) cm-1. Anal. calcd for C49H66Au2N2O8P2S4: C, 42.18; H,
4.77; N, 2.01. Found: C, 41.84; H, 4.57; N, 1.72. Yield of 7: 109
mg, 71%. 1H NMR: δ 3.66 (s, 24H, OCH2CH2O), 3.98 (t, 8H, 3JHH
) 6.2 Hz, OCH2CH2N), 4.19 (t, 8H, 3JHH ) 6.2 Hz, OCH2CH2N),
3
4.28 (t, 4H, JHP ) 3.3 Hz, P-C-CH in Cp), 4.85 (brs, 4H,
P-C-CH-CH in Cp), 7.34–7.59 (m, 20H, Ph). 31P{1H} NMR: δ
30.4 (s). IR (KBr): 1468 ν(CdN), 997, 987 ν(C-S) cm-1. Anal.
calcd for C56H68Au2FeN2O8P2S4: C, 43.76; H, 4.46; N, 1.82. Found:
C, 43.38; H, 3.98; N, 2.09.
Preparation of [Au(S2CNC10H20O4)(CNR)] (R ) 2,6-Me2-
C6H3, 8). To a dichloromethane solution (5 mL) of [AuCl(CNR)]
(62 mg, 0.17 mmol) was added Na(S2CNC10H20O4) (54 mg, 0.17
mmol). The solid dissolved rapidly, and the resulting yellow solution
was stirred for about 15 min and then filtered through kieselgur. The
clear solution was concentrated to ca. 1 mL, from which yellow crystals
were obtained by slow diffusion of 10 mL of a hexane solution of
0.05 M isocyanide (molar ratio of dithiocarbamate/CNR 1:4), after
standing at -18 °C. Two differently shaped crystals were found: cubes,
corresponding to compound 2, and plates, corresponding to compound
8. The latter were selected by hand for X-ray diffraction and to record
an FTIR spectrum. IR (KBr): 2179 ν(Ct N).
Crystal Structure Determination of 2–5 and 8. The crystals
were mounted on glass fibers and transferred to a Bruker SMART
CCD diffractometer. Cell parameters were retrieved using SMART34
software and refined with SAINT35 on all observed reflections. Data
reduction was performed with the SAINT software and corrected for
Lorentz and polarization effects. Absorption corrections were based
on multiple scans (program SADABS).36 The structures were solved
by direct methods and refined anisotropically on F2.37 All non-
hydrogen atomic positions were located in difference Fourier maps
Preparation of [Au(S2CNC10H20O4)(PR3)] (R ) Me, 3; Ph,
4). These derivatives were prepared in two different ways. Method
A: To a dichloromethane solution (20 mL) of [AuCl(PR3)] (0.2
mmol; R ) Me, 62 mg; Ph, 99 mg)32 was added Na(S2CNC10H20O4)
(63 mg, 0.2 mmol). The white solid dissolved rapidly, and the
resulting yellow solution was stirred for about 1 h and then filtered
through kieselgur and concentrated to ca. 2 mL. The addition of
diethyl ether (20 mL) afforded complexes 3 and 4 as yellow solids,
which were washed with diethyl ether (2 × 5 mL). Method B: To
a dichloromethane suspension of 1 or 2 (98 mg; 0.1 or 0.033 mmol,
respectively) was added the corresponding amount of phosphine
(0.2 mmol: PMe3,15 mg; PPh3, 52 mg). The resulting clear solution
was stirred for 1 h and concentrated to ca. 2 mL. The addition of
diethyl ether (20 mL) afforded complexes 3 and 4. Yield of 3: 73
1
2
mg, 65%. H NMR: δ 1.59 (d, 9H, JPH ) 10.5 Hz, Me), 3.65 (s,
12H, OCH2CH2O), 3.94 (t, 4H, 3JHH ) 6.1 Hz, OCH2CH2N), 4.15
(t, 4H, OCH2CH2N). 31P{1H} NMR: δ -6.32 (s). IR (KBr): 1473
ν(CdN), 985, 965 ν(C-S) cm-1. Anal. calcd for C14H29AuNO4PS2:
C, 29.63; H, 5.15; N, 2.47. Found: C, 29.44; H, 4.81; N, 2.49. Yield
(33) Usón, R.; Laguna, A.; Laguna, M. Inorg. Synth. 1989, 26, 85.
(34) SMART V5.051, software for the CCD Detector System; Bruker
Analytical X-ray Instruments Inc.; Madison, WI, 1998.
(35) SAINT V6.02, integration software; Bruker Analytical X-ray Instru-
ments Inc.; Madison, WI, 1999.
(36) Sheldrick, G. M. SADABS: A program for absorption correction with
the Siemens SMART system; University of Göttingen: Göttingen,
Germany, 1996.
(37) SHELXTL program system, version 5.1; Bruker Analytical X-ray
Instruments Inc.; Madison, WI, 1998.
1
of 4: 102 mg, 68%. H NMR: δ 3.64 (s, 12H, OCH2CH2O), 3.96
(30) Arias, J.; Bardají, M.; Espinet, P. J. Organomet. Chem. 2006, 691,
4990.
(31) Granell, J.; Green, M. L. H.; Lowe, V. J.; Marder, S. R.; Mountford,
P.; Saunders, G. C.; Walker, N. M. J. Chem. Soc., Dalton Trans. 1990,
605.
(32) Schmidbaur, H.; Wohlleben, A.; Wagner, F.; Orama, O.; Huttner, G.
Chem. Ber. 1977, 110, 1748.
Inorganic Chemistry, Vol. 47, No. 5, 2008 1605

Arias et al.
and refined anisotropically, with some exceptions for derivative 5 (see
below). The hydrogen atoms were placed in their geometrically
generated positions. Crystal data and details of data collection and
structure refinement are given in Table 8. In complex 2, the atoms
O2, O3, and C9 are disordered in two positions, with the following
occupancy: O2A ) 0.33(7), O3A ) 0.32(5), and C9A ) 0.65(4); only
the major component is shown in the figures. The structure of 3 is a
solvate with disordered dichloromethane. The highest residual density
peak is very close to the gold center. In complex 4, there are high
residual density peaks very close to the gold center. The structure of
5 shows high residual density peaks very close to the four independent
gold centers. Moreover, two flapping crown ethers have been solved
by considering the atoms O6, C18, C78, and O11 as disordered (they
are not refined anisotropically) in two positions with the following
occupancy: O6A ) 0.55(5), C18A ) 0.41(7), C78A ) 0.58(8), and
O11A ) 0.40(6); the third ring was refined as a rigid group. In complex
8, there is a high residual density peak very close to the gold center.
Acknowledgment. We thank the Spanish Comisión In-
terministerial de Ciencia y Tecnología (Project CTQ2005-
08729) and the Junta de Castilla y León (Project VA099A05)
for financial support. J.A. thanks the Ministerio de Edución
y Ciencia (Spain) for a grant. We also thank Dr. J. M. Martín-
Alvarez for taking X-ray data of complex 2 and Dr. D.
Miguel for structural discussions.
Supporting Information Available: A crystallographic infor-
mation file (CIF) containing structural data for 2-5 and 8 is
provided. This material is available free of charge via the Internet
at http://pubs.acs.org.
IC702252J
1606 Inorganic Chemistry, Vol. 47, No. 5, 2008