COMMUNICATION
Figure 2. Thermal ellipsoid drawing of 2. Selected distances (Å)
and angles (deg): Au(1)-N(1) 2.035(7), Au(1)‚‚‚Au(2) 2.711(3);
N(1)-Au(1)-N(3) 170.2(3).
Figure 1. Thermal ellipsoid drawing of 1. Selected distances (Å)
and angles (deg): Au(3)-Cl(1) 2.258(6), Au(3)‚‚‚Au(2) 3.0181(10),
Au(1)-N(1) 2.044(16), Au(1)-S(1) 2.245(6), Au(1)‚‚‚Au(2) 3.0132(12),
N(3)-Au(2)-N(2) 167.5(7).
chemistry, a trinuclear species forms when methyl groups
are in the ortho position. Similar results are obtained when
ortho isopropyl groups are used.12 In gold(I) carbeniate and
imidazolate chemistry, the trinuclear species are the only
neutral complexes isolated to date.13
chloride in THF (Scheme 1). The base-stabilized tetranuclear
gold(I) 3,5-diphenylpyrazolate cluster [(dppm)2Au4(Ph2pz)2]-
(NO3)2 also has been reported.5 The four gold atoms are
located at the corners of a rhomboid with the amidinate
ligands bridging above and below the near plane of the four
Au(I) atoms. The average Au‚‚‚Au distance is ∼3.0 Å,
typical of Au(I)‚‚‚Au(I) aurophilic interactions. Similar
structural arrangements have been found in the tetrameric
1,3-diphenyltriazenidogold(I) complex, [Au4(PhNNNPh)4]
(Au‚‚‚Au ) 2.85 Å),4 and the tetranuclear gold pyrazo-
late complex [Au4(µ-4-tBu-pz)4] (Au‚‚‚Au ) 3.1155(7)-
3.1886(7) Å).6
The dinuclear complex, 2, [Au2(2,6-Me2-form)2], is iso-
lated in quantitative yield by the reaction of (THT)AuCl and
the potassium salt of 2,6-Me2-form in a 1:1 stoichiometric
ratio (Supporting Information). The Au‚‚‚Au distance is
2.711(3) Å, and the N-Au-N angle is 170.2(3)° (Figure
2). To our knowledge, there is only one other example of a
symmetrically bridged dinuclear gold(I) nitrogen complex,
{Au2[(Me3SiN)2C(Ph)]2} with Au‚‚‚Au ) 2.646 Å.14
Few nitrogen ligand complexes of gold(II) are known
compared with the more common gold(I) and gold(III)
species. The gold(II) complexes generally are synthesized
by oxidative addition of halogens or pseudo-halogens to the
dinuclear gold(I) species, often forming darkly colored
products.15-17 The dihalide amidinate species (vida infra)
release the halogen upon gentle heating.
When 1 mmol of Cl2, Br2, or I2 is added to 1 mmol of
[Au2(2,6-Me2-form)2] in THF at room temperature, an
immediate color change from colorless to a very dark green
or brown occurs. Well-shaped dark orange or brown block
crystals grow out of the solution by slow evaporation.
Thermal gravimetric analysis and differential thermal analysis
show the release of solvent of crystallization followed by
the loss of the halogen. X-ray structures of the products (X
) Cl, Br, I) show slight differences in the Au‚‚‚Au distances,
from 2.71 Å in 2 to 2.51-2.57 Å in the gold(II) species.
The Au-X distances, Au-Cl ) 2.36 Å, Au-Br ) 2.47 Å,
Au-I ) 2.68 Å, are normal. The oxidized products also can
A trinuclear species [Au3(2,6-Me2-form)2(THT)Cl] is
isolated when a sterically bulky formamidinate ligand is used
such as the 2,6-dimethyl derivative (Supporting Information).
By the reaction of the potassium salt of the formamidinate
ligand and (THT)AuCl in a (1:1.5) stoichiometric ratio,
the trinuclear species forms and is isolated as monoclinic
(P21/n), prismatic crystals.11 Attempts to obtain a tetranuclear
gold species with this ligand, using different stoichiometric
ratios, were not successful, and instead, a dinuclear species
1
is isolated (vide infra). H NMR of the trinuclear species
shows the characteristic resonances of the tetrahydrothiophene
ligand. The complex is stable at room temperature and in
light for months. The structure contains two short Au‚‚‚Au
distances of ∼3.01 Å and a long Au‚‚‚Au distance of 3.55
Å (Figure 1). The Au-S distance is 2.245(6) Å, and
Au-Cl is 2.258(6) Å.
The chemistry of gold(I) pyrazolates includes various
species such as trinuclear, tetranuclear, and hexanuclear com-
pounds, with the trinuclear product being the most common.
A tetranuclear gold(I) pyrazolate compound forms when a
bulky group such as tert-butyl is used.6 In the amidinate
(12) Abdou, H. E.; Mohamed, A. A.; Fackler, J. P., Jr. Unpublished results.
(13) Burini, A.; Mohamed, A. A.; Fackler, J. P., Jr. Comments Inorg. Chem.
2003, 24, 253-280.
(14) Fenske, D.; Baum, G.; Zinn, A.; Dehnicke, K. Z. Naturforsch., B:
Chem. Sci. 1990, 45, 1273-1278
(11) Crystal data for 1, C38H46Au3ClN4S: Mr ) 1217.22, monoclinic, space
group P21/n, a ) 10.8294(6) Å, b ) 21.4450(13) Å, c ) 16.7756(10)
Å, â ) 99.5270(10)°, V ) 3842.2(4) Å3, Z ) 4, R1 ) 0.0858, and
wR2 ) 0.1671. Crystal data for 2, C34H38Au2N4: Mr ) 896.62,
triclinic, space group P1h, a ) 7.354(6) Å, b ) 9.661(7) Å, c ) 11.421-
(10) Å, R ) 81.74(5)°, â ) 99.5270(10)°, γ ) 86.07(9)°, V ) 760.1-
(4) Å3, Z ) 1, R1 ) 0.0465, and wR2 ) 0.1243. Crystal data for 3,
C34H38Au2Cl2N4‚1.5C6H12: Mr ) 1093.76, monoclinic, space group
P21/c, a ) 11.012(2) Å, b ) 18.464(4) Å, c ) 19.467(4) Å, â )
94.86(3)°, V ) 3943.7(14) Å3, Z ) 4, R1 ) 0.0689, wR2 ) 0.1707.
(15) (a) Murray, H. H.; Raptis, R. G.; Fackler, J. P., Jr. Inorg. Chem. 1988,
27, 26-33. (b) Raptis R. G.; Fackler J. P., Jr. Inorg. Chem. 1988, 27,
4179-4182. (c) Laguna, A.; Laguna, M. Coord. Chem. ReV. 1999,
193-195, 837-856.
(16) (a) Mazany, A. M.; Fackler, J. P., Jr. J. Am. Chem. Soc. 1984, 106,
801. (b) Dudis, D. S. Ph.D. Thesis, Case Western Reserve University,
Cleveland, OH, 1984. (c) Raptis, R. G.; Porter, L. C.; Emrich, R. J.;
Murray, H. H.; Fackler, J. P., Jr. Inorg. Chem. 1990, 29, 4408 and
references therein.
(17) Fackler, J. P., Jr. Polyhedron 1997, 16, 1-17.
Inorganic Chemistry, Vol. 44, No. 2, 2005 167