Gold(I) and Gold(III) trifluoromethyl derivatives

Article abstract of DOI:10.1002/chem.201302142

Trifluoromethylation of AuCl₃ by using the Me ₃SiCF₃/CsF system in THF and in the presence of [PPh ₄]Br proceeds with partial reduction, yielding a mixture of [PPh ₄][Au^I(CF₃)₂] (1′) and [PPh₄][Au^III(CF₃)₄] (2′) that can be adequately separated. An efficient method for the high-yield synthesis of 1′ is also described. The molecular geometries of the homoleptic anions [Au^I(CF₃)₂]^- and [Au ^III(CF₃)₄]^- in their salts 1′ and [NBu₄][Au^III(CF₃)₄] (2) have been established by X-ray diffraction methods. Compound 1′ oxidatively adds halogens, X₂, furnishing [PPh₄][Au ^III(CF₃)₂X₂] (X=Cl (3), Br (4), I (5)), which are assigned a trans stereochemistry. Attempts to activate C-F bonds in the gold(III) derivative 2′ by reaction with Lewis acids under different conditions either failed or only gave complex mixtures. On the other hand, treatment of the gold(I) derivative 1′ with BF₃× OEt₂ under mild conditions cleanly afforded the carbonyl derivative [Au^I(CF₃)(CO)] (6), which can be isolated as an extremely moisture-sensitive light yellow crystalline solid. In the solid state, each linear F₃C-Au-CO molecule weakly interacts with three symmetry-related neighbors yielding an extended 3D network of aurophilic interactions (Au...Au=345.9(1)pm). The high tilde nu _CO value (2194cm^-1 in the solid state and 2180cm^-1 in CH ₂Cl₂ solution) denotes that CO is acting as a mainly σ-donor ligand and confirms the role of the CF₃ group as an electron-withdrawing ligand in organometallic chemistry. Compound 6 can be considered as a convenient synthon of the Au^I(CF ₃) fragment, as it reacts with a number of neutral ligands L, giving rise to the corresponding [Au^I(CF₃)(L)] compounds (L=CNtBu (7), NCMe (8), py (9), tht (10)). Copyright

Full text of DOI:10.1002/chem.201302142

FULL PAPER
DOI: 10.1002/chem.201302142
Gold(I) and GoldACTHNUTRGNEUNG(III) Trifluoromethyl Derivatives
Sonia Martꢀnez-Salvador,[a] Larry R. Falvello,[b] Antonio Martꢀn,[a] and Babil Menjꢁn*[a]
Dedicated to Professor Antonio Laguna on the occasion of his 65th birthday
ꢀ
Abstract:
Trifluoromethylation
of
C F bonds in the gold
(III) derivative
with three symmetry-related neighbors
yielding an extended 3D network of
AuCl3 by using the Me3SiCF3/CsF
system in THF and in the presence of
[PPh4]Br proceeds with partial reduc-
tion, yielding a mixture of [PPh4]
G
2’ by reaction with Lewis acids under
different conditions either failed or
only gave complex mixtures. On the
other hand, treatment of the gold(I)
derivative 1’ with BF3·OEt2 under mild
conditions cleanly afforded the carbon-
aurophilic
interactions
(Au···Au=
345.9(1) pm). The high n˜CO value
(2194 cmꢀ1 in the solid state and
2180 cmꢀ1 in CH2Cl2 solution) denotes
that CO is acting as a mainly s-donor
ligand and confirms the role of the CF3
group as an electron-withdrawing
ligand in organometallic chemistry.
Compound 6 can be considered as a
[AuI-
ACHTUNGTRENNUNG
A
ACHTUNGTRENNUNG
that can be adequately separated. An
efficient method for the high-yield syn-
thesis of 1’ is also described. The mo-
lecular geometries of the homoleptic
yl derivative [AuI
ACTHNUGTRENNG(U CF3)(CO)] (6),
which can be isolated as an extremely
moisture-sensitive light yellow crystal-
line solid. In the solid state, each linear
F3C-Au-CO molecule weakly interacts
anions [AuI
in their salts 1’ and [NBu4]
G
ACHTUNGTRENNUNG
A
U
convenient synthon of the “AuI
ACHTUNGTRENNUNG(CF3)”
(2) have been established by X-ray dif-
fraction methods. Compound 1’ oxida-
tively adds halogens, X2, furnishing
fragment, as it reacts with a number of
neutral ligands L, giving rise to the cor-
ꢀ
Keywords: aurophilicity · C F acti-
responding [AuI
ACTHNUTRGEN(NUG CF3)(L)] compounds
vation · fluorinated compounds ·
gold · metal carbonyl derivatives ·
organogold compounds
[PPh4]
N
N
(L=CNtBu (7), NCMe (8), py (9), tht
(10)).
(4), I (5)), which are assigned a trans
stereochemistry. Attempts to activate
Introduction
ganogold compounds have been prepared by using a ple-
thora of organic groups.[1] The simplest alkyl group, methyl,
was first introduced in gold chemistry by Gibson and
Brain[6] and then thoroughly studied by Gilman and
Woods,[7] Tobias and Rice,[8] and Kochi et al.[9] Representa-
tive methylgold derivatives include the neutral compounds
Organogold chemistry is one of the most interesting and
fruitful areas of current chemistry[1] with deep implications
in both facets of chemical research: basic and applied chem-
istry.[2] Of particular importance is the recently found in-
volvement of organogold derivatives as active catalysts in an
ever-increasing number of chemical transformations under-
gone by organic molecules.[3]
AuI
gands, as well as the homoleptic anions [AuI
[AuIII(CH3)4]ꢀ.[8,9] The unstable compound referred to as
“trimethylgold” is considered to be, in fact, the etherate
[Au(CH3)3A(OEt2)], rather than the actual homoleptic species
“Au (CH3) seems to have been de-
(CH3)3”.[7] Solvent-free Au
(CH3)(L) and AuIII
ACHUTGTNRENNUG CAHTUNGTRENNUNG
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
Gold was the first transition metal, after platinum,[4]
which enabled the isolation of sufficiently stable alkyl metal
compounds. In the first decade of the 20th century, Pope
and Gibson found appropriate synthetic methods to obtain a
number of thermally stable organogold derivatives with
ethyl being the organic group.[5] In the more than one centu-
ry that has elapsed since this pioneering work, countless or-
A
CHTUNGTRENNUNG
A
ACHTUNGTRENNUNG
tected among the products trapped in a matrix after reaction
of methane with laser-ablated, excited gold metal atoms.[10]
According to Kochi et al.,[9b] the stability of these types
of compounds follows the order: AuI
[AuI(CH3)2]ꢀ AuIII
and
(CH3)4]ꢀ within each series.
G
ACHTUNGTRENNUNG
R
G
N
ACHTUNGTRENNUNG
[a] Dr. S. Martꢀnez-Salvador, Dr. A. Martꢀn, Dr. B. Menjꢁn
Instituto de Sꢀntesis Quꢀmica y Catꢂlisis Homogꢃnea (ISQCH)
Universidad de Zaragoza-C.S.I.C., C/Pedro Cerbuna 12
E-50009 Zaragoza (Spain)
The trifluoromethyl group, CF3, was not introduced in
gold chemistry until relatively later dates due to the lack of
suitable sources of that perfluorinated group. In the 1970s,
Johnson and Puddephatt obtained [AuIII
N
ACHTUTGNRENGU(N CH3)2ACHTUNGTRENNUNG(PR3)]
E-mail: menjon@unizar.es
(PR3 =PMe3, PMe2Ph) and [AuI
corresponding methyl derivatives [AuI
ACHUTGTNERN(NUG CF3)ACHTUNGTRENNUNG
[b] Prof. Dr. L. R. Falvello
Instituto de Ciencia de Materiales de Aragꢁn (ICMA)
Universidad de Zaragoza-C.S.I.C., C/Pedro Cerbuna 12
E-50009 Zaragoza (Spain)
G
ACHTUNGTRENNUNG
CF3I.[11] Since then, different synthetic methods have been
devised to prepare just a few trifluoromethylgold deriva-
tives, as recently summarized elsewhere.[12] Focusing on the
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.201302142.
Chem. Eur. J. 2013, 00, 0 – 0
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homoleptic derivatives, solvent-free “Au
G
of this homoleptic species to be established by X-ray diffrac-
tion methods (see below). Compound 2 had already been
detected to form in solution as one of the many components
have been prepared by reaction of gold atoms with CF3 radi-
cals in the gas phase.[13] This unsaturated species decompos-
es at about 08C, but it can be stabilized by coordination of
an additional ligand such as PMe3, giving rise to the four-co-
obtained in the reaction of [NBu4]
CH2Cl2.[12] The pure salt [NBu4][AuIII
be isolated in that case either. 13C and 19F NMR spectro-
scopic data associated with the [Au
(CF3)4]ꢀ anion in solution
ACHTUNGTRENNUNG
A
ACHTUNGTRENNUNG
ordinate compound [AuIII
N
(PMe3)].[13] Tyrra and co-
3ACHTUNGTRENNUNG
A
ACHTUNGTRENNUNG
A
are in keeping with those previously assigned to that homo-
leptic species.[12]
AHCTUNGTRENNUNG
anion have been prepared, some of them showing supercon-
ducting behavior at low temperature.[15] To the best of our
knowledge, however, synthetic procedures to prepare simple
salts of the latter anion have not been reported so far and
unpublished results by T. Roy suggest that such salts are not
By performing the same process as indicated in Equa-
tion (1), but by using [PPh4]Br as the added salt, a similar
mixture of compounds [PPh4]
easily obtained.[16] The homoleptic anion [AuIII
G
[AuI
ACHTUNGTNERNUG AHCUTNGTREN(NUNG CF3)2] (1’) and [PPh4]-
also observed to arise in the reaction of the cyano derivative
N
ACHTUNGTRENNUNG
[AuIII(CN)4]ꢀ with ClF in CH2Cl2 involving transformation
[12]
ꢁ
ꢀ
of the C N triple bond into three C F single bonds. The
process was unfortunately non-selective and competed with
a number of side reactions that resulted in complex reaction
mixtures. Suitable synthetic procedures to afford such com-
pounds would be highly desirable especially considering the
potential use of [AuIII
anion.[17]
(CF3)4]ꢀ as a weakly coordinating
ACHTUNGTRENNUNG
Herein, we report on the synthesis of new, simple salts of
but starting from the gold(I) precursor species [AuClACHTUNGTRENNUNG(tht)]
the homoleptic anions [AuI(CF3)2]ꢀ and [AuIII(CF3)4]ꢀ to-
A
U
(tht=tetrahydrothiophene) [Eq. (2)]. No redox process was
observed to occur in this case. The final yield in isolated 1’
(87% based on Au) is even higher than that reported for
gether with a comparative study of their reactivity towards
halogens and Lewis acids. As a result, a number of new tri-
fluoromethyl gold(I) and gold
cleanly obtained including the unusual carbonyl gold deriva-
tive [Au
(CF3)(CO)] (6).[18] This compound, as well as the
thioether complex [Au(CF3)(tht)] (10), are valuable syn-
thons of the “Au(CF3)” unit, which, unlike its non-fluorinat-
ed homologue Au
(CH3),[10] has never been detected before.
A
the tetramethylammonium salt [NMe4]ACHTNGUTRENNUG ACHTUGNTRENN(NUG CF3)2] (60%),
[AuI
which had been obtained by Tyrra and coworkers starting
ACHTUNGTRENNUNG
from the binary chloride AuCl.[14]
A
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
It is to be hoped that the availability of these convenient
starting materials will stimulate a faster development of tri-
fluoromethylgold chemistry.
ACTHNUTRGNEUNG
The gold atom in the [AuI(CF3)2]ꢀ anion of compound 1’
(Figure 1) resides on an inversion center thus resulting in a
ꢀ
single crystallographically independent Au C bond length, a
strictly linear arrangement of the two CF3 ligands, and a
staggered mutual disposition of these fluorinated groups.
Results and Discussion
Homoleptic gold(I) and goldACTHNUTRGENUGN(III) derivatives: Anhydrous
AuCl3 was reacted in THF at ꢀ808C with CF3SiMe3 in the
presence of CsF [Eq. (1)]. The temperature was allowed to
rise slowly and solid [NBu4]Br was added to the reaction
mixture well before it reached room temperature (by ꢂ
ꢀ208C). During the reaction, partial reduction occurred as
the organogold(I) species [NBu4]
together with the organogold
(CF3)4] (2) in a typical 2:3 molar ratio (19F NMR spectrosco-
A
ACHTUNGTRENNUNG
A
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
py). To our surprise, both ionic compounds were appreciably
soluble even in non-polar toluene and our attempts to sepa-
rate them by fractional crystallization of the reaction mix-
ture failed because of their similar solubilities in the solvents
used. Despite this failure, single crystals of compound 2
were obtained, enabling the crystal and molecular structure
Figure 1. Displacement-ellipsoid diagram (50% probability) of the [AuI-
AHCTUNGTRENNUNG
(CF3)2]ꢀ anion as found in single crystals of compound 1’. Selected bond
ꢀ
lengths [pm] and angles [8] with estimated standard deviations: Au C(1)
ꢀ
203.3(2), average C F 137.8(3); C(1)-Au-C(1’) 180, average Au-C-F
116.0(2), average F-C-F’ 102.3(2). Primed atoms at (ꢀx, ꢀy, ꢀz+1).
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Gold Trifluoromethyl Derivatives
FULL PAPER
ACTHNUGTRNENUG
The overall geometry of the [AuI(CF3)2]ꢀ anion in com-
DFT methods.[17] The AuIII CF3 bond length found in com-
pound 2 (208.0(7) pm average) is again indistinguishable
ꢀ
pound 1’ is similar to yet more symmetric than that found in
ꢀ
the salt [N
(PPh3)2]
[AuI
(CF3)2].[14] The Au C bond
from the AuIII C6F5 one in the homologous perfluorophenyl
ꢀ
(203.3(2) pm) is shorter than that found in the non-fluorinat-
anionic species [AuIII
U
ACTHNUGTRNENUG
ed homologue species [AuI(CH3)2]ꢀ (207.5(6) pm).[9a] This
also comparable to the Pt CF3 bond length found in the
isoelectronic and isoleptic organoplatinum(II) compound
II
ꢀ
ꢀ
shortening of the M C bond has been frequently observed
in organometallic chemistry upon fluorination of a given or-
ganyl group, the effect being most prominent in the case of
CF3 versus CH3.[19] This feature has been usually attributed
to a higher s-orbital contribution to the hybridization of the
[NBu4]2ACHTNUTRGENNGU ACHTUNGTRENNUGN
[PtII(CF3)4] (205.0(4) pm average).[23] Deviations
from the ideal tetrahedral geometry for the C-donor atom
in compound 2—with wider Au-C-F angles (114.2(6)8 aver-
age) and narrower F-C-F’ angles (104.4(8)8 average)—are
similar to those found in compound 1’. These deviations
would once more point to a higher s-orbital character of the
ꢀ
carbon orbital involved in the M C s bond. In line with this
I
ꢀ
reasoning is the fact that the Au CF3 bond length in com-
I
pound 1’ (203.3(2) pm) is indistinguishable from the Au
carbon hybrid orbital responsible for the AuIII C s bond.
ꢀ
ꢀ
C6F5 one in the homologous perfluorophenyl anionic species
However, the presumable departure from the standard sp3
[AuI
(C6F5)2]ꢀ (204.4(4) pm),[20] in which the C-donor atom
hybridization has in this case no appreciable effect on the
corresponding M C interatomic distances, as the Au CF3
has an approximate sp2 hybridization. Furthermore, the Au-
C-F angles (116.0(2)8 average) are wider than expected for a
purely tetrahedral geometry (109.58), whereas the F-C-F’
angles are narrower (102.3(2)8 average).
III
ꢀ
ꢀ
bond length found in compound 2 is indistinguishable from
the AuIII CH3 one in the non-fluorinated homologous spe-
ꢀ
cies [AuIII
A
C
ꢀ
The structural characterization of salts containing [MIII-
distances in the d8 square-planar organogold
(III) derivatives
(CF3)4]ꢀ anions (M=Cu, Ag) has been frequently hampered
[AuIIIR4]ꢀ (R=CH3, CF3, C6F5) are similar to each other,
by severe crystallographic disorder in the anion.[21] In our
case, disorder did not affect the anion of compound 2, but
did affect the cation. Details of the analysis of the single-
crystal diffraction data from compound 2 can be found in
the Supporting Information. A highly symmetric geometry
but consistently longer than the Au C distances in the cor-
I
ꢀ
responding d10 linear organogold(I) derivatives [AuIR2]ꢀ.
This trend is in contrast to the expected contraction of the
metal center upon oxidation and can be attributed to a
higher coordination number in the former case (AuIII) than
in the latter (AuI).
has been found for the square-planar [AuIII
(CF3)4]ꢀ ion
ACHTUNGTRENNUNG
(Figure 2) with two crystallographically independent, virtu-
It is known that the thermal stability of a given organo-
metallic species is generally enhanced upon fluorination of
the metal-bound organyl group.[24] The couple formed by the
methyl versus trifluoromethyl groups is no exception to this
trend.[25] Both compounds 1’ and 2’ show remarkable ther-
mal stabilities. They melt without decomposition at 193 and
1258C, respectively, as determined by visual inspection and
by differential scanning calorimetry (DSC) measurements.
Moreover, they show significant loss of weight only at about
275 and 3708C, respectively, according to their correspond-
ing thermogravimetric analysis (TGA). It is interesting to
note that solid samples of the non-fluorinated homologous
species [Li
tamethyldiethylenetriamine) and [Li
ACHTUNGTREN(GNUN pmdta)]ACHUTNRTGENNUNG ACTUHNGTRENNUNG
[AuI
N
R
ACHTUNGTRENNUNG
have been reported to already show evidence of decomposi-
tion at 1408C.[9b]
Figure 2. Displacement-ellipsoid diagram (50% probability) of the [AuIII
(CF3)4]ꢀ anion as found in single crystals of compound 2. Selected bond
-
Reactivity with halogens: Although the square-planar orga-
ACHTUNGTRENNUNG
noplatinum(II) derivative [NBu4]2ACHTUNTGRENNUG ACHTUNTGERN(NUNG CF3)4] had been
[PtII
ꢀ
lengths [pm] and angles [8] with estimated standard deviations: Au C(1)
ꢀ
ꢀ
207.5(6), Au C(2) 208.5(7), average C F 132(1); C(1)-Au-C(2) 90.0(2),
C(1)-Au-C(1’) 180.0(1), average Au-C-F 114.2(6), average F-C-F’
104.4(8). Primed atoms at (ꢀx+32, ꢀy+21, ꢀz+1).
found to react with halogens, X2 (X=Cl, Br, I), to give the
octahedral organoplatinum(IV) compounds [NBu4]2[trans-
ACTHNUTRGNEUNG
PtIV(CF3)4X2],[23] no evidence of reaction between the iso-
A
ACHTUNGTRENNUNG
ꢀ
ally identical Au C distances. The angles between trans-
standing groups amount to exactly 1808, as required by crys-
tal symmetry and those between cis-standing groups form
been observed to form by reacting [NBu4]ACHTUNGTRENNUNG
ClF in CH2Cl2 solution, either.[12] On the other hand, the or-
ganogold(I) derivative 1’ has been found to react under mild
conditions with Cl2, Br2, or I2 affording the oxidative addi-
ACTHNUTRGNEUNG
right angles. The geometry of the [AuIII(CF3)4]ꢀ anion in
compound 2 is much more symmetric than had been found
in the salt [N(PPh3)2]
[AuIII(CF3)4].[16] It is in excellent agree-
ment with an optimization carried out in the gas phase by
A
E
U
tion products [PPh4]
in good yields [Eq. (3)].
[AuIII
ACHTUNGTRENUNG ACHTUNGTNERN(UNG CF3)2X2] (X=Cl (3), Br (4), I (5))
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B. Menjꢁn et al.
slightly more shielded on decreasing the electronegativity of
the X ligand: dC =133.3 (Cl), 131.7 (Br), and 128.7 ppm (I).
The heteronuclear 19F,13C-coupling constants have also com-
1
parable values to those found in compound 3: J
(19F,13C)=
A trans stereochemistry can be assigned to the chloro de-
rivative 3 in view of its spectroscopic properties. The IR
spectrum shows just one weak band at n˜ =377 cmꢀ1 that can
ꢀ
368 (Cl), 364 (Br), 360 Hz (I) and 3J
(19F,13C)=40 (Cl), 39
ACHTUNGTRENNUNG
(Br), 37 Hz (I). Stereochemical information can best be de-
3
rived from the JACTHNUTRGNEUNG
(19F,13C) coupling constant, fairly high value
be assigned to the only IR-active n
(Au Cl) vibration mode
points of which to a trans geometry in all three cases.
An X-ray diffraction study was carried out on single crys-
tals of the iodo derivative 5. Unfortunately, the CF3 and I li-
gands were affected by severe disorder in such a way that it
precluded the stereochemistry of the compound to be estab-
lished by this means.
Oxidative addition of halogens to organogold(I) deriva-
tives has found wide use in synthetic chemistry.[27–29] Some-
times, however, the reaction proceeds with the breaking of
expected in a trans geometry (B2u mode assuming D2h local
symmetry). The 19F NMR spectrum shows a singlet at dF =
ꢀ33.8 ppm and the 13C NMR spectrum shows a quartet cen-
tered at dC =133.3 ppm. Neither the chemical shift values
nor the NMR spectral patterns observed for compound 3 in
solution enable its stereochemistry to be unambiguously de-
cided. However, the values of the heteronuclear coupling
constants, 1J
ACHTUNGTRENNUNG ACHTUNGTRENNUGN
(19F,13C)=368 Hz and especially 3J(19F,13C)=
ꢀ
40 Hz, are higher than those observed in the parent species
Au C bonds and/or with poor stereoselectivity giving rise to
1
3
1’, for which J
ACHTUNGTRENNUNG
G
E
several reaction products.[30] In such cases, the usefulness of
the procedure is greatly diminished. The process depicted in
Equation (3) is quite convenient, because it allows com-
pounds 3–5 to be prepared under mild conditions in high
yields and in a stereoselective way. Both the stereoselectivi-
ty of the process and the stereochemistry of the final prod-
3J(19F,13C) value should be very sensitive to the mutual geo-
metric arrangement of the two coupled CF3 groups, it is rea-
sonable to conclude that the linear arrangement of the CF3-
Au-CF3 unit in compound 1’ (Figure 1) is preserved in the
oxidized species 3 to which we accordingly assign a trans ge-
ometry. Moreover, the 19F and 13C NMR spectroscopic pa-
rameters of compound 3 in solution are in keeping with
those reported for the anionic species [trans-AuIII-
ucts [PPh4][trans-AuIII
sidering the high trans influence of the CF3 group.[31] In fact,
the non-fluorinated homologous species [AsPh4]
[AuIII-
(CH3)2X2] have exclusively the cis structure.1 [32] Halogens
are also known to oxidatively add to the related perfluoro-
ACHTNUGRTEN(NNUG CF3)2X2] (3–5) are remarkable con-
ACHTUNGTRENNUNG
A
ACHTUNGTRENNUNG
reaction of [NBu4]ACHTUNGTRENNUNG
[AuIII(CN)4] with ClF in CH2Cl2 solu-
tion.[12] The latter compound, however, was not isolated
from the complex reaction mixture. It is interesting to note
[AuI
phenyl-derivative [NBu4]ACHTUNRGTNEGNU ACHTNUGTREN(GNUN C6F5)2] in a trans fashion
giving rise to the corresponding [NBu4][trans-AuIII
ACHTNUTRGEN(UNG C6F5)2X2]
that the [cis-AuIII
species.[29]
arise as one of the several components obtained by treat-
ment of the aforementioned reaction mixture with Me3SiCl.
This compound was assigned a signal appearing at a consid-
Reactivity with Lewis acids: One of the most salient fea-
tures in the chemistry of trifluoromethyl metal compounds,
erably higher frequency (dF =ꢀ26.4 ppm) in the 19F NMR
[M] CF3, is the possibility of their undergoing fluoride ab-
ꢀ
3
spectrum. No detectable J
N
straction giving rise to a highly electrophilic metal-bound
[M]=CF2 difluorocarbene unit.[25]The experimental condi-
tions under which such a process takes place vary greatly
from one case to another. Thus, LiCF3 spontaneously elimi-
nates LiF at very low temperature,[34] but in most cases, the
presence of an external acidic promoter is required.[25] We
have found that an acid as weak as water (simple moisture)
been observed for the latter species, thus denoting a signifi-
cant drop in the corresponding value when the coupled CF3
groups adopt a cis arrangement.
No concluding stereochemical information was obtained
from the analysis of the low-frequency absorptions in the IR
spectra of compounds 4 and 5. Moreover, compounds 4 and
5 show singlets in their 19F NMR spectra, a feature that is
compatible with both cis and trans geometries. The chemical
shifts observed for compounds 3–5 follow the reverse order
of electronegativity of the X ligand: dF =ꢀ33.8 (Cl), ꢀ26.5
(Br), and ꢀ13.0 ppm (I). This trend had also been observed
for the series of organoplatinum(IV) derivatives with formu-
ꢀ
is able to promote C F bond activation in the homoleptic
organoplatinum(II) derivative [PtII
G
the monocarbonyl derivative [PtII
ACHTUNGTRENNUNG
A
ACHTUNGTRENNUNG
markably inert. This chemical inertness together with its
marked thermal stability and low nucleophilicity make the
la [trans-PtIV
served in the organogold
N
ACTHNGUTERNNUG
[AuIII(CF3)4]ꢀ anion a convenient weakly coordinating anion
U
as has been theoretically justified[17] and experimentally
creased electron density on the metal with decreasing elec-
tronegativity of X, which would enhance the paramagnetic
contribution to the screening constants of the F nuclei. This
effect was suggested to arise from overlapping between the
F(p) orbitals and the filled M(d) ones.[26] The 13C NMR spec-
tra of compounds 4 and 5 show similar patterns to that
found for the chloro derivative 3 with the C nuclei being
1
Preliminary experiments aimed at preparing the cis isomer of [PPh4]-
ACHUTNGRENUNG AHCTUNGTREN(NNGU CF3)2X2] by reacting compound 1’ with SOCl2 at room tempera-
[AuIII
ture rendered poor results, as the main product was again the trans
isomer 3. This reaction was stimulated by the good results obtained in
platinum chemistry, where SOCl2 was found to be a convenient reagent
to cleanly afford the cis isomer of [NBu4]2ACTHUNGTRENNUG AHCTUNGTREN(NUGN CF3)4Cl2] (see
[PtIV
Ref. [33]).
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Gold Trifluoromethyl Derivatives
FULL PAPER
demonstrated.[15] Following recent theoretic calculations,[17]
and BF3·OEt2, whereas at a sufficiently high temperature
(>ꢀ308C), increasing amounts of the final product 6 were
observed together with still unreacted starting materials.
Compound 6 was eventually formed in a quantitative way
on a spectroscopic basis (19F NMR spectroscopy). It can also
be isolated as a thermally labile, white solid in moderate
yield (34%). Given the similar properties of the PF3 and
CO molecules when acting as ligands in transition-metal
chemistry,[36] there is a formal relationship between com-
the neutral difluorocarbene derivative [AuIII
ACTHUNRGTENNG(U CF3)3ACHTUNGTNER(NUGN =CF2)]
might be experimentally feasible. We therefore aimed to at
least detect it by reacting compound 2’ in CH2Cl2 solution
with BF3·OEt2 or Me3SiOSO2CF3 as potential fluoride-ab-
stractor agents. No reaction was observed after prolonged
treatment of compound 2’ with Me3SiOSO2CF3 in CH2Cl2
solution at room temperature. Gradually raising the temper-
ature to the boiling point of the solvent produced no better
results. Compound 2’ did not react with an equimolar
amount of BF3·OEt2 at room temperature, but it finally re-
acted when treated with an excess reagent, giving rise to a
complex mixture of fluorinated species that were neither
separated nor identified.
pound 6 and the trifluorophosphine derivative [AuI
(PF3)]. The latter substance was obtained by low-tempera-
ture treatment of [AuCl(PF3)] with Cd(CF3)2·dme (dme=di-
ACHTUNGTRENNUNG(CF3)-
AHCTUNGTRENNUNG
A
ACHTUNGTRENNUNG
methoxyethane), but it was poorly characterized due to its
high sensitivity and thermal instability.[37] Compound 6 is
also extremely water-sensitive both in solution and in the
solid state and hence much care must be taken during its
synthesis and handling. Otherwise, in the presence of mois-
ture, massive decomposition is observed under reduction to
metallic gold. This behavior is in keeping with the previous-
ly suggested involvement of the carbonyl derivative 6 as an
In contrast to the unproductive reactivity of the
organogoldACHTUNGTRENNUNG(III) derivative 2’ with Lewis acids, the organo-
gold(I) compound 1’ was found to react with BF3·OEt2
under mild conditions (Scheme 1) giving rise to the mono-
intermediate in the hydrolysis of the salt [NBu4][AuACHTUNGTRENNUNG(CF3)2]
to eventually produce monodispersed gold nanoparticles.[14]
The IR spectrum of compound 6 shows a sharp absorption
at n˜ =2194 cmꢀ1 in the solid state, which can be assigned to
the nCO vibration. This absorption shifts to n˜ =2180 cmꢀ1 in
CH2Cl2 solution. The high nCO frequency observed denotes
that the CO molecule in compound 6 is acting as a mainly
s-donor ligand. It is even higher than that observed for the
chlorocarbonyl derivative [AuCl(CO)], for which n˜CO
2162 cmꢀ1 in CH2Cl2 solution (Table 1).[38,39] This fact is in
keeping with the electronegativity of the CF3 group (cCF
=
Scheme 1. Suggested reaction path for the transformation of compound
1’ ([PPh4]+ being the cation) into compound 6 together with the observed
CO exchange in the latter.
=
3
3.49) being higher than that assigned to chlorine (cCl =
3.16).[40] It is interesting to note that the halocarbonyl deriv-
atives [AuX(CO)] with the remaining halogens, X=F,[41]
Br,[38,41] or I,[42] do not appear to have been isolated hitherto.
The attachment of a AuCl3 unit to the Cl ligand in
[AuCl(CO)] to give the chloro-bridging, mixed-valence com-
carbonyl derivative [AuI
ACTHNUTRGENNU(G CF3)(CO)] (6). It is reasonable to
assume that the process takes place through a transient di-
fluorocarbene–gold intermediate species formed upon fluo-
ride abstraction. This highly electrophilic difluorocarbene–
gold intermediate, [Au]=CF2,
could possibly be stabilized by
coordination of a ligand such
as, for instance, the Et2O mole-
Table 1. Spectroscopic and structural data of the gold carbonyl compounds isolated in condensed phase.[a]
ꢀ
ꢀ
Compound
d
G
d
E
n˜(CO)
[cmꢀ1
dC(CO)
[ppm]
Reference
G
]
ACHTUNGTRENNUNG
cule
released
from
the
A
193(2)[b]
111(3)[b]
2162 (CH2Cl2)
2180 (SOCl2)
2195 (solid)
172 (CD2Cl2)
[38,39]
[38,43]
[44]
BF3·OEt2 adduct upon forma-
tion of the complex anion
[BF4]ꢀ. A related donor-stabi-
lized [M]=CF2·L species has
been recently found in platinum
chemistry (M=Pt; L=a substi-
tuted pyridine ligand).[35] The
precise nature of the intermedi-
ate species involved could not
be experimentally determined
because all our attempts to
detect it by 19F NMR spectro-
scopy failed. At low tempera-
ture (ꢀ808C), no reaction was
E
G
–
–
–
–
170.8 (CD2Cl2)
[c]
[Au
[Au
G
–
E
197.7(16)
108(2)
2194 (solid)
183.0 (CD2Cl2)
173 (CDCl3)
174 (HSO3F)
this work
2180 (CH2Cl2)
2144 (solid)
[Au{BH
N
186.2(9)
111(1)
[68]
[61]
2125 (HCy)[g]
[Au(CO)2]
N
197.1(8)[d]
110.8(9)[d]
2251ACTHGNUTERNNUG
(solid)[e]
2210 (HSO3F)
2185 (solid)
2197 (KBr)
2193 (KBr)
[Au
[Au
[Au
N
E
200.8(6)
197.1(5)
–
110.8(7)
111.0(6)
–
182.6
182.7
182.9
[45b]
[45a,c]
[45c]
G
ACHTUNGTRENNUNG
[a] Experimental details for each technique are given where appropriate. [b] Structural parameters taken from
reference [69]. [c] The signal appearing at dC =162 ppm in HSO3F solution is attributable to the dissociated
species [Au(CO)]+ rather than to the neutral compound [Au
ACHTUNGTRENNUNG
parameters corresponding to the double salt [Au(CO)2]
N
ACHTUNGTRENNUNG
observed between compound 1’ thyl)pyrazolyl. [g] Cy=cyclohexyl. [h] Mes=mesityl.
Chem. Eur. J. 2013, 00, 0 – 0
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B. Menjꢁn et al.
pound [Cl3AuIII
(m-Cl)AuI(CO)] seems to diminish the donor
ferent global charge. Apparently, the electron-withdrawing
CF3 group has a similar effect on the Au(CO) unit as a net
positive charge on the complex plus a good-donor ligand,
such as a phosphine or a NHC one.
The crystal and molecular structures of compound 6 were
determined by single-crystal, X-ray diffraction methods. No
interstitial solvent molecules were observed in the crystal
lattice. At molecular level, the CF3-Au-CO unit shows a
strictly linear structure (Figure 4), as the C-Au-C vector co-
ability of the halo ligand, thereby causing an increase of ap-
proximately 20 cmꢀ1 in the corresponding n˜CO value
(Table 1).[38,43] A similar n˜CO frequency (2195 cmꢀ1 in the
solid state) is observed in the neutral compound [Au-
ACHTUNGTRENNUNG(OSO2F)(CO)] containing the hard O-bound fluorosulfato
ligand.[44] Comparable n˜CO values (Table 1) have also been
observed in the solid state for the cationic monocarbonyl
derivatives [Au(CO)(L)]ACTHNUTRGNE[UGN SbF6], where the auxiliary ligand is
a bulky phosphine or an N-heterocyclic carbene (NHC): L=
PMes3 (n˜CO =2185 cmꢀ1),[45a,b] 1,3-bis(2,6-diisopropylpheny-
l)imidazol-2-ylidene (IDipp) (n˜CO =2193 cmꢀ1),[45c] 1,3-
bis(2,6-diisopropylphenyl)imidazolin-2-ylidene
(SIDipp)
(n˜CO =2197 cmꢀ1).[45a,c]
Valuable information can also be obtained from multinu-
clear NMR spectroscopy. For this purpose, the labeled spe-
cies [AuACHTUNGTRENNUNG(CF3)ACHTUNGTRENNUNG
(13CO)] (6*) was prepared by exchange be-
tween metal-bound and free CO molecules undergone by
compound 6 in CD2Cl2 solution under an isotopically pure
13CO(g) atmosphere (Scheme 1). The CO/13CO exchange
process took place rapidly at 08C and in a virtually quantita-
Figure 4. Displacement-ellipsoid diagram (50% probability) of the [Au-
AHCTUNTGREG(NNNU CF3)(CO)] molecule. Selected bond lengths [pm] and angles [8] with es-
ꢀ
ꢀ
timated standard deviations: Au C(1) 204.7(14), Au C(2) 197.7(16),
tive way. As
a result, the singlet appearing at dF =
ꢀ
ꢀ
C(2) O 108(2), C(1) F 132.6(10); C(1)-Au-C(2) 180.0(3), Au-C(2)-O
ꢀ31.1 ppm in the 19F NMR spectrum of compound 6 splits
into a doublet in the corresponding spectrum of the labeled
species 6* (Figure 3a) due to coupling with the 13CO nucleus
180.0(18), average F-C(1)-Au 114.3(7), average F-C(1)-F’ 104.2(8).
incides longitudinally with a crystallographic C3 axis. The
ꢀ
Au CF3 bond length (204.7(14) pm) is indistinguishable
from that reported for [Au
(CF3)
N
and from that observed in the parent species 1’
(203.3(2) pm) in spite of the different global charge on each
complex and the different trans influence of CF3 versus
CO.[47] The Au CO bond length (197.7(16) pm) is in the
ꢀ
ꢀ
upper range of Au CO distances in gold carbonyl com-
pounds for which the molecular structure has been establish-
ed (Table 1), being indistinguishable from those found in the
cationic monocarbonyl derivative [Au(CO)ACTHNUTRGNEUNG
(SIDipp)]+
(197.1(5) pm),[45c] and in the dicarbonyl species [Au(CO)2]+
(197.1(8) pm).[48] The C O bond length in compound 6
ꢀ
(108(2) pm) is, in turn, in the lower range found in any
structurally characterized metal carbonyl species.[49] The
main spectroscopic and structural features of compound 6
Figure 3. Low-temperature a) 13C and b) 19F NMR spectra of compound
6* in CD2Cl2 solution with spectral parameters indicated.
ꢀ
ꢁ
(i.e., high n˜CO, low dC, long M CO, and short C O values)
consistently suggest that the CO molecule is acting as a
mainly s-donor ligand.[50]
3
with J
N
At supramolecular level, each AuI center (closed d10 shell)
is found to establish weak aurophilic interactions (Au···Au
345.9(1) pm) with three other gold neighbor centers, in a
perfectly symmetric way, as imposed by the crystallographic
C3 axis (Figure 5). Thus, the surrounding gold atoms are lo-
cated at the vertices of a regular triangle from whose geo-
metric center the middle gold atom departs by approximate-
ly 40 pm. The whole pattern is repeated across the lattice
building an extended three-dimensional network of auro-
philic interactions. In spite of the rich variety of structural
patterns currently known for aurophilic interactions,[51] the
trigonal arrangement is rarely found in gold chemistry. Ac-
cording to recent theoretical calculations on possible geome-
is associated with the quartet appearing at dC =183.0 ppm in
the 13C NMR spectrum of compound 6* (Figure 3b), thus al-
lowing to unambiguously assign both 13C and 19F signals to
the same spin system. The dC(CO) value observed for com-
pound 6* is virtually the same (Table 1) as those reported
for the cationic species [Au(CO)(L)]+ (L=PMes3, SIDipp,
IDipp),[45] which also show comparable n˜CO values (see
above). The quite similar IR and NMR spectroscopic behav-
ior of the Au(CO) unit in these two kinds of compounds,
[AuACHTUNGTRENNUNG
(CF3)(CO)] and [Au(CO)(L)]+, suggests that the elec-
tronic structure and bonding scheme of the Au C O frag-
ment should also be similar for them, regardless of their dif-
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Gold Trifluoromethyl Derivatives
FULL PAPER
2194 to 2180 cmꢀ1) and by no means uncommon in metal
carbonyl chemistry.[55] It is unfortunate that the thermal in-
stability of compound 6 precludes the determination of the
n˜CO value for isolated (CF3)Au(CO) molecules in the gas
phase.
According to the aforementioned calculations,[45a] it can
be anticipated that stronger aurophilic interactions with the
(CF3)Au(CO) unit, if present in some way, should result in a
more pronounced effect on the n˜CO value.
Substitution reactions on compound 6: The ease with which
compound 6 exchanges coordinated CO with free 13CO(g)
at low temperature (Scheme 1) evidences the high lability of
that ligand and suggests the potential use of complex 6 as a
convenient synthon of the “AuACHTNUGRTENUNG(CF3)” fragment. In order to
confirm this point, complex 6 was reacted with typical repre-
sentatives of neutral monodentate ligands. It was observed
that the CO molecule in compound 6 was replaced under
mild conditions (Scheme 3), giving rise to the corresponding
Figure 5. Near environment of a [AuACHTNUTRGNENG(U CF3)(CO)] molecule in the crystal
lattice of compound 6 with indication of the aurophilic interactions with
the nearest equidistant neighbor molecules.
Scheme 3. Synthesis of the neutral (trifluoromethyl)gold(I) derivatives 7–
10 by replacement of the weakly coordinating CO or THT molecules by
the appropriate ligand L.
Scheme 2. Energetically favored geometric arrangements calculated for
the tetranuclear clusters {AuXACHTUNGTRNEUNG
(PH3)}4 (X=Cl, Br).[52]
neutral derivatives [AuI
ACTHNUTRGENUN(G CF3)(L)] (L=CNtBu (7), NCMe
(8), pyridine (py, 9), tht (10)). Substitution readily occurred
in a quantitative way based on 19F NMR spectroscopy-and
without any trace of decomposition and/or metal reduction.
From the reaction media, however, the corresponding solid
compounds 7–10 were isolated in only moderate yield
(PH3)}4 clusters (X=Cl, Br),[52]
tries of tetranuclear {AuXACHTUGNTERNUNGN a
trigonal arrangement (Scheme 2a) similar to that found in
compound 6 should not significantly differ in energy from
tetrahedral (Scheme 2b) or quadro-ring (Scheme 2c) struc-
tures. To the best of our knowledge, the only experimental
precedent for such a structural pattern was found for [Au-
(ꢂ50%). Aside from the nitrile compound [AuI
ACHTUNGTRENNUNG(CF3)-
AHCTUNGTREG(NNNU NCMe)] (8), which is also thermally labile and nearly as
ꢁ
G
(CNtBu)].[53] In that case, however, discrete tet-
moisture-sensitive as the starting material 6, the remaining
compounds 7, 9, and 10 were found to be moisture-stable
(at least in the short term) and to show enhanced thermal
stabilities. They can be handled in air at room temperature
without any sign of decomposition. Their formulation is
based on analytical and spectroscopic data. Furthermore,
the crystal and molecular structures of the least stable com-
pound 8 was established by single-crystal X-ray diffraction
methods.
ranuclear aggregates were formed showing considerably
stronger aurophilic interactions (Au···Au 312.4(1) pm). The
weak nature of the aurophilic interactions in compound 6 is
in keeping with the hard character of the CF3 group and the
poor s-donating ability of the CO ligand that should jointly
result in a diminished electron density on the gold center.[54]
High-level theoretical calculations on [AuACHTUNRGTNEUNG(CF3)(CO)] (6)
carried out by G. Frenking and coworkers[45a] reveal that the
vibrational behavior of this molecule can be affected by in-
termolecular aurophilic interactions. Given the weak nature
of the aurophilic interactions experimentally observed in
compound 6 (substantially weaker than those postulated in
the calculations), their effect on the n˜CO value would not be
expected to be large in magnitude. In fact, the shift observed
for the n˜CO value in CH2Cl2 solution is only moderate (from
The trifluoromethyl derivative [Au
known to be “much more stable both thermally and photo-
chemically than [Au(CH3)
(CNMe)].”[56] In a similar way,
compound 7 has been found to decompose at 1198C, where-
as its non-fluorinated homologous species [Au(CH3)-
(CNtBu)] had been previously reported to melt with decom-
position at 628C.[57] Following this trend, and considering
ACHUTGTNNERNUG(CF3)AHCTUNGTRENN(UGN CNMe)] is
A
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
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B. Menjꢁn et al.
the related nature of CO and CNR molecules as typical s-
donor/p-acceptor ligands, the unknown species [Au-
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
A
highly electrophilic neutral fragment.
A
The molecular structure of the neutral species [AuI
ACHTUNGTRENNUNG(CF3)-
A
R
ACHTUNGTREN(NUGN NCMe)] (8) is depicted in Figure 6. The coordination envi-
starts to decompose at approximately 658C being, therefore,
ronment of the gold atom is virtually linear (C(1)-Au-N
ꢁ
significantly less stable than the known isomeric species
176.0(3)8) as is also the whole C-Au-N C-C framework.
[Au
(gas phase) was determined.[56] We are not aware of the exis-
tence of the non-fluorinated homologues [Au(CH3)-
(NCMe)], [Au(CH3)(py)], or [Au(CH3)
(tht)].2 The thermal
ACHTUNGTRENNUNG(CF3)ACHTUNGTRENNUNG(CNMe)] for which a half-life of 30 min at 2508C
AHCTUNGTRENNUNG
A
E
N
ACHTUNGTRENNUNG
stabilities of compounds 9 and 10, however, compare quite
well with those reported for their corresponding chloro de-
rivatives. Thus, compound [Au
higher thermal stability (1208C decomp) than [AuCl(py)]
(928C decomp).[58] Furthermore, compound [Au
(CF3)(tht)]
(10) decomposes at 1158C, whereas the analogous chloro
ACHTUNGRTEN(NUNG CF3)(py)] (9) has a slightly
A
ACHTUNGTRENNUNG
Figure 6. Displacement-ellipsoid diagram (50% probability) of the [Au-
A
ACHTUNGTREN(NUNG NCMe)] molecule as found in single crystals of compound 8 with
derivative [AuClACHTUNGTRENNUNG(tht)] does so at a slightly higher tempera-
ꢀ
ꢀ
angles [8] with estimated standard deviations: Au C(1) 200.2(8), Au N
ture (ꢂ1408C).
ꢀ
ꢀ
ꢀ
202.6(7), N C(2) 113(1), C(2) C(3) 143.4(10), average C F 136.5(9);
C(1)-Au-N 176.0(3), Au-N-C(2) 179.4(6), N-C(2)-C(3) 179.0(8), average
F-C(1)-Au 114.8(5), average F-C(1)-F’ 103.6(6). Primed atoms at (x, ꢀy,
z).
The IR spectrum of [AuACTHNUTRGENN(UG CF3)ACHTUNGTERN(NUGN CNtBu)] (7) shows a sharp
single absorption at n˜ =2247 cmꢀ1 that can be assigned to
the nCN mode. This value is considerably higher than that re-
ported for the analogous methyl derivative [Au
ACHTUNGTNER(NUGN CH3)-
ACHTUNGTRENNUNG
the higher group electronegativity of CF3 (3.49) versus CH3
(2.28).[40] For the same reason, a considerably lower n˜CO
value would also be expected for the unknown [Au-
This five-atom chain together with the F(1) atom are con-
tained in a mirror plane, thus yielding the other two fluorine
substituents, F(2) and F(2’), related by symmetry. The hy-
drogen atoms of the CH3 group are disordered over two
equally populated gauche conformations with respect to the
distal CF3 group. The gold center is almost equidistant from
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
interesting to note that the n˜CN value observed for the neu-
tral compound 7 does not differ significantly from that re-
ꢀ
the C-donor atom of the CF3 group (Au C(1) 200.2(8) pm)
ported for the cationic derivative [Au
G
(SIDipp)
E
and from the N-donor atom of the neutral nitrile ligand
[SbF6], for which n˜CN =2244 cmꢀ1.[45a] Following this virtual
(Au N 202.6(7) pm). The Au C bond length in compound 8
does not significantly differ from those found in the trifluor-
omethyl gold precursor species 1’ (203.3(2) pm) and 6
ꢀ
ꢀ
coincidence, it becomes apparent that the unexpected elec-
tronic similarity already noted between complex fragments
ꢀ
as seemingly disparate as “Au
wards CO (see above) also applies towards CNtBu.
The IR spectrum of [Au(CF3)(NCMe)] (8) exhibits two
A
N
(204.7(14) pm). The Au N bond length is comparable to
that found in the homoleptic cationic derivative [Au-
[SbF6] (197(1) pm).[61] The N C bond length (N
ACHUTGTNNERNUG(NCMe)2]ACHTUNGTRENNUGN
C(2) 113(1) pm) does not significantly depart from that cor-
ꢁ
ꢁ
A
U
sharp absorptions of medium, approximately equal intensity
at n˜ =2338 and 2310 cmꢀ1. The former absorption can be as-
signed to the n2 fundamental of mainly nCN character,
whereas the latter can be attributed to a combination
(n3+n4) mode.3 The frequency values observed for com-
pound 8 are almost as high as those reported for the homo-
responding to the free ligand (115.6(2) pm).[62]
At supramolecular level, weak aurophilic interactions are
observed between neighbor gold atoms (Au···Au
345.3(1) pm) resulting in infinite zigzag chains of antiparallel
[AuI
ACTHNUTRGNEN(UG CF3)ACHTUNTGREN(NUNG NCMe)] molecules (Figure 7). Furthermore, a
leptic cationic derivative [Au
(NCMe)2]
E
network of hydrogen bonds arises between fluorine atoms
of the CF3 groups and hydrogen atoms of near CH3 groups.
The supramolecular arrangement is quite similar to that
found in the chloro derivative of methyl isocyanide, [AuCl-
and 2312 cmꢀ1 (n3+n4).[59] Although “nitriles are generally
considered to be relatively moderate s-donors and p-accept-
ors toward transition metals”,[60] the significant increase in
the value for n2 for compound 8 with respect to the free
ligand (n˜ =2253 cmꢀ1 in the liquid state)[59] suggests that
NCMe, much like the unsaturated molecules CO and
CNtBu, acts as a mainly s-donor ligand towards the “Au-
AHCTUNGTREG(NNNU CNMe)], which exhibits even weaker aurophilic interac-
tions (Au···Au 363.7(1) pm).[63] In contrast, and despite the
geometric pattern in compound 8 being quite different from
that found in the parent species 6 (Figure 5), the closest in-
termetallic distance is the same in both cases, thus suggest-
ing a similar degree of aurophilic interaction.
ACHTUNGTRENNUNG(CF3)” moiety. On the basis of the IR data of these [Au-
2
We have found no record on the existence of the chloro derivative
[AuCl(NCMe)] either.
The 19F NMR spectrum of compound 7 shows a singlet at
dF =ꢀ29.2 ppm, evidencing that the fluorine atoms of the
CF3 group are slightly less shielded than in the starting ma-
ACHTUNGTRENNUNG
3
No correction for Fermi resonance effects was applied to the raw ex-
perimentally observed frequency values.
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Gold Trifluoromethyl Derivatives
FULL PAPER
Conclusion
Simple procedures to prepare tetraphenylphosphonium salts
of the homoleptic trifluoromethyl-aurate anions [AuI-
ACHUTNGRENNUG CAHTUNGTRENNUGN
(CF3)2]ꢀ and [AuIII(CF3)4]ꢀ (compounds 1’ and 2’, respective-
ly) are described [Eqs. (1) and (2)]. Both compounds show
enhanced thermal stability over their non-fluorinated homo-
logues.[9b] A comparative study of the reactivity of com-
pounds 1’ and 2’ towards halogens and towards Lewis acids
is also presented. The inertness of the d8 homoleptic [AuIII-
AHCTUNGTRENNUNG
(CF3)4]ꢀ anion towards halogens, its reluctance to react with
Lewis acids and its low nucleophilicity validate its role as a
weakly coordinating anion.[15,17] Hence, the square-planar,
ACTHNUTRGNEUNG
singly charged [AuIII(CF3)4]ꢀ anion provides an alternative
ACTHNUTRGNEUNG
to the isoleptic tetrahedral species [BIII(CF3)4]ꢀ that may
find potential use in structural and supramolecular chemis-
try wherever a planar anion should be preferred.
ACTHNUTRGNEUNG
The linear d10 anionic species [AuI(CF3)2]ꢀ has proven, in
Figure 7. Near environment of the [AuACTHNUTRGENNGU(CF3)ACHTUNTGREN(NUNG NCMe)] molecules in the
crystal lattice of compound 8 with indication of the aurophilic interac-
tions with the nearest equidistant neighbor molecules.
turn, to be much more reactive. It undergoes oxidative addi-
tion of halogens to give the corresponding organogold(III)
derivatives [trans-AuIII(CF3)2X2]ꢀ (X=Cl, Br, I) in excellent
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
yields and in a stereoselective way [Eq. (3)]. It also reacts
terial 6, for which dF =ꢀ31.1 ppm. Even less shielded are
the fluorine atoms in compounds 8–10, for which dF =ꢀ24.2,
ꢀ24.0 and ꢀ26.2 ppm, respectively. During the careful study
with the etherate BF3·OEt2 giving rise to the neutral mono-
carbonyl derivative [AuI
ACTHNUTRGENNU(G CF3)(CO)] (6). Relevant spectro-
scopic (IR and 13C NMR) and structural data consistently
suggest that the CF3 group is acting as a hard ligand with a
high electron-withdrawing ability, and that the CO molecule
acts as a mainly s-donor ligand. The ease with which the
metal-coordinated CO molecule can be replaced by other li-
gands qualifies compound 6 as a useful synthon of the “Au-
of the hydrolysis of [NMe4][AuACHTUNGTRNE(NUG CF3)2] in a CD3CN/H2O
mixture (3:1), a singlet at dF =ꢀ21.0 ppm had been tenta-
tively assigned to the nitrile compound [Au(CF3)-
(NCCD3)].[14] This assignment, however, seems unlikely in
AHCTUNGTRENNUNG
ACHTUNGTRENNUNG
view of the significantly different chemical shift found for
compound 8, that is, dF =ꢀ24.2 ppm.
ACHUTNRGENNUG ACHTUNGTREN(NUGN CF3)(L)]
(CF3)” fragment. Thus, the neutral species [AuI
Metal complexes containing labile ligands, such as nitriles
or thioethers are particularly valuable in chemical synthe-
sis.[60,64] Gold complexes with thioethers, SR2, have been
known for more than a century.[65] Cyclic THT is one of the
most widely used thioethers in gold chemistry.[29,66,67] In the
present work, for instance, we have already exploited its
labile behavior in the procedure used to prepare compound
1’ [Eq. (2)]. We have also found that the THT molecule in
compound 10 is, in fact, readily replaced by CNtBu or py,
giving rise to compounds 7 and 9, respectively (Scheme 3).
The lability of the THT molecule qualifies compound 10 as
(L=CNtBu (7), NCMe (8), py (9), tht (10)) are readily ob-
tained by treating compound 6 with the appropriate amount
of the free ligand L. For most synthetic purposes, the ther-
mally robust and well-behaved compound [AuI
ACTHNUTRGNNEG(U CF3)ACHTUNGTRENNUNG(tht)]
(10) may be used as a convenient substitute for the thermal-
ly labile and extremely water-sensitive carbonyl derivative
[AuI
ACTHNUGTRENNG(U CF3)(CO)] (6).
Experimental Section
an alternative synthon of the “AuACHTNUTRGNEUNG(CF3)” fragment. Because
General procedures and materials: Unless otherwise stated, the reactions
and manipulations were carried out under purified argon by using
Schlenk techniques. Solvents were dried by using a MBraun SPS-800
complex 10 has a higher thermal stability and is much less
sensitive to moisture than the carbonyl derivative 6, com-
pound 10 can be the reagent of choice wherever a better
ligand than THT should be used. This is, however, not the
case of NCMe, which is not able to replace THT
(Scheme 3): compound 10 dissolved for longer than a week
in acetonitrile at room temperature gave no sign of ligand
substitution at all. Thus, any of the compounds (Au-
System. Compound [AuClACHTNUTGRNEUNG
(tht)] was obtained as described elsewhere.[67]
Other chemicals such as CsF (Acros Organics), CF3SiMe3 (Apollo Scien-
tific Ltd.), and BF3·OEt2 (Fluka) were purchased and used as received.
Solutions of Cl2 or Br2 in CCl4 were prepared by passing a slow stream of
dry Cl2(g) through cold CCl4 or by diluting a measured volume of Br2 in
CCl4, respectively; the solutions were titrated before use. Elemental anal-
yses were carried out by using a Perkin–Elmer 2400 CHNS/O Series II
microanalyzer. Except where indicated, IR spectra were recorded on
KBr discs by using the following Perkin–Elmer spectrophotometers: 883
(n˜ =4000–200 cmꢀ1) or Spectrum One (n˜ =4000–350 cmꢀ1). The IR spec-
tra of samples with poor thermal stability and/or containing highly labile
ligands were recorded by using an attenuated total reflectance (ATR)
device. Melting points were determined by visual inspection on samples
placed in sealed glass capillaries by using a Gallenkamp (Electronic)
melting point apparatus. Mass spectra were registered by MALDI-TOF
ACHTUNGTRENNUNG(CF3)(L’)] [L’=CO (6), NCMe (8), tht (10)) provide a con-
venient entry into the chemistry of trifluoromethylgold de-
rivatives with the following lability order: CO>NCMe>
THT.
Chem. Eur. J. 2013, 00, 0 – 0
ꢄ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
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B. Menjꢁn et al.
techniques on Bruker MicroFlex or AutoFlex spectrometers. NMR spec-
tra were recorded on any of the following spectrometers: Varian Gemini-
300, Bruker ARX 300, or Bruker ARX 400. Unless otherwise stated, the
spectroscopic measurements were carried out at room temperature.
Chemical shifts of the measured nuclei (d in [ppm]) are given with re-
spect to the standard references in use: SiMe4 (1H and 13C) and CFCl3
(19F). NMR parameters associated with the cations are unexceptional and
are therefore omitted.
pound 1’ (0.20 g, 0.30 mmol) at ꢀ788C. The resulting mixture was stirred
while allowing it to slowly reach room temperature. The solution was
concentrated to dryness. Treatment of the resulting residue with Et2O
(3 cm3) rendered a white solid, which was identified as compound 3
(0.17 g, 0.23 mmol, 77%). M.p. 1908C; 13C NMR (100.577 MHz, CD2Cl2):
d=133.3 ppm (qq, 1J(19F,13C)=368, 3J(19F,13C)=40 Hz); 19F NMR
ACTHNUTRGENNUG CAHTUNGTRENNUGN
(376.308 MHz, CD2Cl2): d=ꢀ33.84 ppm; IR (KBr): n˜ =1588 (w), 1485
(w), 1436 (m), 1263 (m), 1187 (w), 1112 (vs), 1099 (vs), 1080 (vs), 1060
ꢀ
(vs), 997 (w), 804 (m), 751 (w), 723 (s), 689 (s), 527 (s), 378 (m, Au Cl),
Trifluoromethylation of AuCl3
257 cmꢀ1 (m); MS (MALDIꢀ): m/z: 405 [Au
G
Workup of the [NBu4]+ salts: CF3SiMe3 (1.6 cm3, 10.90 mmol) was added
to a suspension of CsF (1.50 g, 9.9 mmol) in THF (15 cm3) at ꢀ788C and
the mixture was stirred for 1 h. After the subsequent addition of AuCl3
(0.6 g, 1.97 mmol) suspended in THF (5 cm3) and previously cooled at
ꢀ788C, the reaction medium was allowed to warm slowly. When the tem-
perature reached ꢀ208C, [NBu4]Br (0.63 g, 1.97 mmol) was added, and
then the system was allowed to reach room temperature overnight during
stirring. The resulting slate blue suspension was filtered and the brown
filtrate was observed to contain a mixture of compounds 1 and 2 in a typ-
ical 2:3 molar ratio, by 19F NMR spectroscopy. The filtrate was concen-
trated to dryness affording a residue from which we were not able to sat-
isfactorily separate compounds 1 and 2. However, while attempting to
separate them by crystallization in a CH2Cl2/n-hexane mixture at 48C,
single crystals of 2 were obtained that were suitable for X-ray diffraction
purposes (see below as well as the Supporting Information). 13C and
ACHUTNGRENNUG CAHTUNGTRENNUGN
(CF3)2]ꢀ, 301 [Au(CF3)Cl]ꢀ; elemental analysis calcd (%) for
C26H20AuCl2F6P: C 41.9, H 2.7; found: C 41.4, H 2.8.
Synthesis of [PPh4][trans-Au(CF3)2Br2] (4): By using the procedure just
A
ACHTUNGTRENNUNG
described for synthesizing compound 3, compound 4 was prepared start-
ing from compound 1’ (0.20 g, 0.30 mmol) and a solution of Br2 in CCl4
(1.57 cm3, 0.37 mmol). Complex 4 was obtained as a yellow solid (0.19 g,
0.23 mmol, 77%). M.p. 1908C (decomp); 13C NMR (100.577 MHz,
CD2Cl2): d=131.7 ppm (qq, 1J(19F,13C)=364, 3J(19F,13C)=39 Hz);
ACTHNUTRGENNUG CAHTUNGTRENNUGN
19F NMR (376.308 MHz, CD2Cl2): d=ꢀ26.48 ppm; IR (KBr): n˜ =1588
(w), 1484 (s), 1437 (s), 1339 (w), 1314 (w), 1191 (m), 1162 (m), 1109 (vs),
1096 (vs), 1080 (vs), 1027 (vs), 996 (s), 926 (s), 838 (m), 752 (s), 724 (vs),
689 (vs), 615 (w), 557 (w), 527 (vs), 457 (w), 309 (w), 256 (w), 240 cmꢀ1
(CF3)2Br2]ꢀ, 355 [AuBr2]ꢀ,
ACHTUNGTRENNUNG
ꢀ
(w, Au Br); MS (MALDIꢀ): m/z: 493 [Au
345 [Au
(CF3)Br]ꢀ, 335 [Au(CF3)2]ꢀ; elemental analysis calcd (%) for
C26H20AuBr2F6P: C 37.4, H 2.4; found: C 37.15, H 2.2..
Synthesis of [PPh4][trans-Au(CF3)2I2] (5): By using the procedure just
N
ACHTUNGTRENNUNG
19F NMR data associated with the [Au(CF3)2]ꢀ and [Au(CF3)4]ꢀ anions in
ACTHNUTRGENNUG CAHTUNGTRENNUGN
solution are in keeping with those previously assigned to those homolep-
A
ACHTUNGTRENNUNG
tic species.[12, 14]
described for synthesizing compound 3, compound 5 was prepared start-
ing from complex 1’ (0.20 g, 0.30 mmol) and I2 (75 mg, 0.30 mmol). Com-
plex 5 was obtained as an orange solid (0.22 g, 0.24 mmol, 80%). M.p.
1788C (decomp); 13C NMR (100.577 MHz, CD2Cl2): d=128.7 ppm (qq,
Workup of the [PPh4]+ salts: CF3SiMe3 (1.6 cm3, 10.90 mmol) was added
to a suspension of CsF (1.50 g, 9.9 mmol) in THF (20 cm3) at ꢀ788C and
the mixture was stirred for 1 h. After the subsequent addition of AuCl3
(0.5 g, 1.64 mmol) and [PPh4]Br (0.69 g, 1.64 mmol), the reaction medium
was maintained for 1 h under ꢀ608C and then allowed to reach room
temperature overnight during stirring. The resulting light brown suspen-
sion was filtered and the brown filtrate was concentrated to dryness af-
fording a residue, which by treatment with Et2O (2ꢅ10 cm3) gave a white
solid identified as compound 1’ (0.55 g, 0.81 mmol, 49%). The Et2O ex-
tract was also concentrated to dryness furnishing another residue, which
on treatment with iPrOH (5 cm3) gave a different white solid identified
as compound 2’ (0.30 g, 0.37 mmol, 22%). The analytical and spectro-
scopic properties of compound 1’ are given in the next experimental
entry.
1J(19F,13C)=360, 3J(19F,13C)=37 Hz); 19F NMR (376.308 MHz, CD2Cl2):
ACTHNUTRGENNUG CAHTUNGTRENNUGN
d=ꢀ13.04 ppm; IR (KBr): n˜ =1588 (w), 1484 (w), 1435 (m), 1339 (w),
1314 (w), 1260 (w), 1192 (w), 1161 (w), 1110 (vs), 1089 (vs), 1063 (vs),
997 (m), 927 (w), 846 (w), 751 (m), 723 (s), 689 (s), 615 (w), 527 (s),
255 cmꢀ1 (m); MS (MALDIꢀ): m/z: 589 [Au
(CF3)2I2]ꢀ, 451 [AuI2]ꢀ, 393
ACHTUNGTRENNUNG
[AuACTHNUGRTNENUG ACHUTNGTRENNUGN
(CF3)I]ꢀ, 335 [Au(CF3)2]ꢀ; elemental analysis calcd (%) for
C26H20AuF6I2P: C 33.6, H 2.2; found: C 33.3, H 1.95.
Synthesis of [Au
(CF3)(CO)] (6): BF3·OEt2 (38 mm3, 0.30 mmol) was
AHCTUNGTRENNUNG
added to a solution of compound 1’ (0.20 g, 0.30 mmol) in CH2Cl2
(10 cm3) at ꢀ788C under light exclusion and the mixture was allowed to
react for 4 h while the temperature rose to 08C and the initially yellow
solution gradually faded. Addition of pre-cooled n-hexane (20 cm3) to
the, by then, colorless solution caused the precipitation of a white solid
that was filtered off.—The filtrate at 08C was suitable for most synthetic
purposes if immediately used.—By allowing the filtrate to stand at
ꢀ608C, light yellow crystals of compound 6 were obtained, which were
filtered, washed with cold n-pentane, and vacuum dried, while maintain-
ing the temperature at ꢀ788C to avoid decomposition (0.03 g, 0.10 mmol,
34%). Crystals of compound 6 quickly darken at room temperature and/
or when exposed to moist air. No satisfactory elemental analyses were
obtained due to the instability of the substance. 13C NMR (100.577 MHz,
Compound 2’: M.p. 1258C; 13C and 19F NMR data associated with the
[AuACHTUNGTRENNUNG
(CF3)4]ꢀ anion in solution are in keeping with those reported for the
[NBu4]+ salt 2;[12] IR (KBr): n˜ =3046 (w), 1588 (w), 1486 (w), 1438 (s),
1114 (vs), 1065 (vs), 996 (m), 754 (m), 723 (s), 689 (s), 531 (s), 311 cmꢀ1
(w); MS (MALDIꢀ): m/z: 473 [Au
(CF3)4]ꢀ; elemental analysis calcd (%)
ACHTUNGTRENNUNG
for C28H20AuF12P: C 41.4, H 2.5; found: C 41.0, H 2.4.
Synthesis of [PPh4][AuACHTUNGTRENNUNG
(CF3)2] (1’): CF3SiMe3 (1.41 cm3, 9.41 mmol) was
added to a suspension of CsF (1.30 g, 8.56 mmol) in THF (20 cm3) at
ꢀ788C and the mixture was stirred for 1 h. After subsequent addition of
[AuClACHTUNGTRENNUNG(tht)] (0.91 g, 2.85 mmol) and [PPh4]Br (1.20 g, 2.85 mmol) the re-
CD2Cl2, ꢀ108C): d=183.0 ppm (q, 3J
(19F,13C)=15.7 Hz; CO); 19F NMR
ACHTUNGTRENNUNG
action medium was maintained for 1 h under ꢀ608C and then allowed to
reach room temperature overnight during stirring. The resulting light
brown suspension was filtered and the brown filtrate was concentrated to
dryness affording a residue, which by treatment with Et2O (2ꢅ5 cm3)
gave a white solid identified as compound 1’ (1.67 g, 2.48 mmol, 87%).
(376.308 MHz, CD2Cl2, ꢀ108C): d=ꢀ31.12 ppm (d, 3J
(19F,13C)=15.7 Hz;
ACHTUNGTRENNUNG
CF3Au13CO; D(12/13C)=0.007 ppm); IR (CH2Cl2): n˜ =2180 cmꢀ1 ( C O);
3
12
ꢁ
IR (ATR): n˜ =2194 (vs, 12CꢁO), 2151 (w, C O), 1128 (vs), 1020 (s),
13
ꢁ
998 (vs), 707 cmꢀ1 (m).
ACTHNUTRGNEUNG
M.p. 1938C; 13C and 19F NMR data associated with the [Au(CF3)2]ꢀ anion
Synthesis of [AuACHTNUTRGENN(UG CF3)ACHTUNGTRENN(UGN CNtBu)] (7)
in solution are in keeping with those found for the [NMe4]+ salt;[14] IR
(KBr): n˜ =3046 (w), 1585 (w), 1525 (m), 1483 (m), 1437 (s), 1402 (w),
1339 (w), 1315 (m), 1161 (w), 1104 (vs), 978 (vs), 927 (m), 759 (s), 749
(m), 723 (vs), 689 (vs), 616 (w), 528 (vs), 449 (w), 281 (w), 267 cmꢀ1 (m);
Method A: A slight excess tBuNC (42 mm3, 0.37 mmol) was added to a
solution of compound 6 (0.30 mmol), prepared as described above, in
CH2Cl2/n-hexane (10 and 20 cm3, respectively) at 08C. The resulting solu-
tion was immediately concentrated to dryness affording a white solid,
which was identified as compound 7 (52 mg, 0.15 mmol, 50%). M.p.
1198C; 1H NMR (300 MHz, CD2Cl2): d=1.57 ppm (s; CMe3);
MS (MALDIꢀ): m/z: 335 [Au
(CF3)2]ꢀ; elemental analysis calcd (%) for
ACHTUNGTRENNUNG
C26H20AuF6P: C 46.3, H 3.0; found: C 46.8, H 2.9.
ACTHNUTRGNEUNG
13C{1H} NMR (100.577 MHz, CD2Cl2): d=156.2 (q, 1J(19F,13C)=341 Hz;
Single crystals suitable for X-ray diffraction purposes were obtained by
slow diffusion of a n-hexane (10 cm3) layer into a solution of 10 mg of
compound 1’ in Me2CO (3 cm3) at 48C.
CF3), 144.5 (1:1:1 triplet, 1J
ACTHNUTRGNEN(UG N, C)=21.5 HzM; C N), 59.2 (br; CMe3),
14
13
ꢁ
29.4 ppm (s; CH3); 19F NMR (376.308 MHz, CD2Cl2): d=ꢀ29.20 ppm; IR
ꢁ
Synthesis of [PPh4]
G
(CF3)2Cl2] (3): Cl2 dissolved in CCl4
(KBr): n˜ =2290 (w), 2247 (s, C N), 1637 (w), 1477 (w), 1397 (w), 1374
(1.77 cm3, 0.60 mmol) was added to a CH2Cl2 solution (15 cm3) of com-
(m), 1256 (w), 1235 (w), 1196 (m), 1132 (vs), 1083 (w), 1001 (vs), 847 (w),
&
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ꢄ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 0000, 00, 0 – 0
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Gold Trifluoromethyl Derivatives
FULL PAPER
805 (w), 729 (w), 531 (w), 324 cmꢀ1
(w); MS: no clear peaks were detected
by using either positive or negative
MALDI techniques; elemental analy-
sis calcd (%) for C6H9AuF3N: C 20.6,
H 2.6, N 4.0; found: C 20.8, H 2.3, N
4.2;
Table 2. Crystal data and structure refinement for complexes 1’, 2, 6 and 8.
1’
2
6
8
formula
Mw [gmolꢀ1
T [K]
C26H20AuF6P
674.36
100(1)
C20H36AuF12N
715.46
100(1)
C20AuF3O
293.99
100(1)
71.073
cubic
C3H3AuF3N
307.03
100(2)
71.073
monoclinic
C2/m
1720.4(5)
584.27(16)
563.99(15)
99.625(3)
0.5589(3)
4
3.649
26.272
536
4.80–56.26
1780
]
l [pm]
71.073
71.073
crystal system
space group
a [pm]
b [pm]
c [pm]
orthorhombic
Pbcn
1551.98(3)
727.72(1)
2038.15(4)
90
2.30192(8)
4
1.946
monoclinic
C2/c
Method B:
tBuNC
(40 mm3,
I213
0.35 mmol) was added to a solution of
compound 10 (0.10 g, 0.28 mmol) in
CH2Cl2 (5 cm3) at room temperature.
After 10 min of stirring, the solution
was concentrated to dryness giving
rise to a white solid, which was collect-
919.72(1)
1680.34(6)
1771.79(6)
98.751(3)
2.7063(2)
4
1.756
5.5269
1400
968.17(1)
968.17(1)
968.17(1)
90
0.907517(16)
8
4.303
32.361
1008
b [8]
V [nm3]
Z
ed and identified as compound
(80 mg, 0.23 mmol, 82%).
7
1 [gcmꢀ3
]
m [mmꢀ1
(000)
]
6.522
1296
Synthesis of [Au
slight excess
G
ACHTUNGTRENNUNG(NCMe)] (8): A
F
A
(20 mm3,
2q range [8]
no. of reflns collected
7.9–57.8
13639
8.5–57.7
7282
8.4–57.2
2912
376
0.37 mmol) was added to a solution of
compound 6 (0.30 mmol), prepared as
described above, in CH2Cl2/n-hexane
(10 and 20 cm3, respectively) at 08C.
The resulting solution was concentrat-
ed to dryness affording a bluish solid,4
which was identified as compound 8
(45 mg, 0.15 mmol, 50%). M.p. 658C
(onset of decomposition); 1H NMR
(400 MHz, CD2Cl2): d=2.39 ppm (s;
Me); 13C{1H} NMR (100.577 MHz,
CD2Cl2, ꢀ308C): d=139.8 (q, 1J-
no. of unique reflns
2780
2974
715
0.0147
Rint
0.0177
0.0257
0.0760
final R indices [I>2s(I)][a]
R1
wR2
0.0208
0.0708
0.0304
0.0784
0.0252
0.0645
0.0188
0.0472
R indices (all data)
R1
wR2
0.0269
0.0732
1.005
–
0.0480
0.0829
1.059
–
0.0253
0.0645
1.056
0.0198
0.0478
1.033
–
goodness-of-fit on F2[b]
Abs. str. par.
0.01(6)
[a] R1 =ꢀ(jFo|ꢀjFcj)/ꢀjFoj; wR2 =[ꢀw(F2oꢀFc2)2/ꢀw(F2o)2]1/2. [b] Goodness-of-fit=[ꢀw(Fo2ꢀF2c)2/
ACHTUNGTRENNUNG
19 13
ꢁ
G
N), 3.5 ppm (s; CH3); 19F NMR
(282.231 MHz,
CD2Cl2):
d=
10 min of stirring, the solution was concentrated to dryness affording a
white solid that was collected and identified as compound 9 (83 mg,
0.24 mmol, 85%).
Synthesis of [AuCAHTUNGTERNU(NNG CF3)AHCTUNGTRENNG(UN tht)] (10): A
slight excess THT (33 mm3,
ꢁ
ꢀ24.24 ppm; IR (ATR): n˜ =2338 (m; n2: C N), 2310 (m; n3+n4), 1436
(w), 1406 (w), 1364 (w), 1310 (w), 1261 (w), 1226 (w), 1118 (s), 996 (vs),
961 (s), 803 (w), 750 (w), 723 (w), 706 (w), 690 (w), 639 (w), 616 (w), 526
(m), 401 cmꢀ1 (s); MS: no clear peaks were detected by using either posi-
tive or negative MALDI techniques; elemental analysis calcd (%) for
C3H3AuF3N: C 11.7, H 1.0, N 4.6; found: C 12.2, H 1.1, N 4.8.
0.37 mmol) was added To a solution of compound 6 (0.30 mmol), pre-
pared as described above, in CH2Cl2/n-hexane (10 and 20 cm3, respective-
ly) at 08C. The resulting solution was immediately concentrated to dry-
ness affording a white solid, which was identified as compound 10
(56 mg, 0.16 mmol, 53%). M.p. 1158C (decomp); 1H NMR (300 MHz,
CD2Cl2): d=3.24 (mc, 4H; a-CH2), 2.07 ppm (mc, 4H; b-CH2);
Synthesis of [Au
Method A: A slight excess py (30 mm3, 0.37 mmol) was added to a solu-
tion of compound (0.30 mmol), prepared as described above, in
ACHTUNGTRENNUNG(CF3)(py)] (9)
6
CH2Cl2/n-hexane (10 and 20 cm3, respectively) at 08C. The resulting solu-
tion was immediately concentrated to dryness affording a white solid that
was collected and identified as compound 9 (57 mg, 0.16 mmol, 55%).
M.p. 1208C (decomp); 1H NMR (400 MHz, CD2Cl2): d=8.55 (centered
multiplet (mc), 2H; Hortho), 8.06 (tt, 1H; Hpara), 7.64 ppm (mc, 2H,
Hmeta);513C{1H} NMR (100.577 MHz, CD2Cl2): d=151.3 (s, Cmeta), 140.6 (s,
ACTHNUTRGNEUNG
13C{1H} NMR (100.577 MHz, CD2Cl2): d=149.4 (q, 1J(19F,13C)=347 Hz;
CF3), 38.21 (s; a-CH2), 30.82 ppm (s; b-CH2); 19F NMR (282.231 MHz,
CD2Cl2): d=ꢀ26.18 ppm; IR (KBr): n˜ =1438 (w), 1310 (w), 1271 (w),
1257 (w), 1120 (vs), 993 (vs), 881 (w), 806 (w), 703 (w), 662 cmꢀ1 (w);
MS: no clear peaks were detected by using either positive or negative
MALDI techniques; elemental analysis calcd (%) for C5H8AuF3S: C
16.9, H 2.3, S 9.05; found: C 17.0, H 2.1, S 9.0.
ACHTUNGTRENNUNG
Cpara), 140.4 (q, 1J(19F,13C)=338 Hz; CF3), 124.7 ppm (s, Cortho); 19F NMR
(376.308 MHz, CD2Cl2): d=ꢀ24.02 ppm; IR (KBr): n˜ =1608 (s), 1485
(w), 1453 (s), 1402 (w), 1358 (w), 1243 (w), 1215 (w), 1133 (vs), 1120 (vs),
1072 (s), 1020 (s), 996 (vs), 975 (vs), 759 (s), 693 (s), 652 (m), 431 (m),
279 cmꢀ1 (s); MS: no clear peaks were detected by using either positive
or negative MALDI techniques; elemental analysis calcd (%) for
C6H5AuF3N: C 20.9, H 1.5, N 4.1; found: C 21.1, H 1.4, N 4.1.
X-Ray structure determinations: Crystal data and other details of the
structure analyses are presented in Table 2. Suitable crystals for X-ray
diffraction studies, obtained as indicated in the corresponding experimen-
tal entry, were mounted at the end of a quartz fiber. The radiation used
in all cases was graphite monochromated MoKa (l=71.073 pm). X-ray in-
tensity data were collected on the following CCD diffractometers:
Oxford Diffraction Xcalibur or (for compound 8) Bruker Smart APEX-
II. The diffraction frames were integrated and corrected for absorption
by using the CrysAlis RED[71] or (for compound 8) the SADABS[72] pro-
grams.
Method B: Py (28 mm3, 0.35 mmol) was added to a solution of compound
10 (0.10 g, 0.28 mmol) in CH2Cl2 (5 cm3) at room temperature. After
4
The bluish color of microcrystalline samples of compound 8 seems to
be due to some surface effect (probably loss of superficial MeCN mole-
cules). Single crystals of compound 8 are colorless while in contact with
the mother liquor, but turn bluish on drying. Moreover, the bluish solid
regenerate perfectly clear solutions, and hence the presence of polydis-
perse reduced metal particles can be ruled out.
The structures were solved by direct methods and refined by full-matrix
least squares on F2 with SHELXL-97.[73] All non-hydrogen atoms were
assigned anisotropic displacement parameters and refined without posi-
tional constraints, except as noted below. All hydrogen atoms were con-
strained to idealized geometries and assigned isotropic displacement pa-
rameters equal to 1.2 times the Uiso values of their attached parent atoms
(1.5 times for the CH3 hydrogen atoms). In the structure of compound 2,
several C atoms of the Bu fragments of the [NBu4]+ cation are heavily
5
The experimental 1H NMR spectrum of compound 9 was satisfactorily
analyzed as a AA’MM’X system with the following homonuclear cou-
pling constants: 3J
(1Ho,1Hm)=5.6, 3J
(1Hm,1Hp)=7.8, 4J
N
4
5
A
(1Hm,1Hm’)=1.8, J
A
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B. Menjꢁn et al.
disordered, and for them a model involving a 50:50 occupancy was used
(see the Supporting Information for details). Full-matrix least-squares re-
finement of these models against F2 converged to final residual indices
given in Table 2.
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1995, 1311, and references therein.
CCDC-941399 (1’), 941400 (2), 813000 (6), and 941401 (8) contain the
supplementary crystallographic data for this paper. These data can be ob-
tained free of charge from The Cambridge Crystallographic Data Centre
via www.ccdc.cam.ac.uk/data_request/cif.
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This work was supported by the Spanish MICINN (DGPTC)/FEDER
(Project CTQ2008-06669-C02-01/BQU), MINECO/FEDER (Project
CTQ2012-35251) and the Gobierno de Aragꢁn (Grupo Consolidado E21:
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Gold Trifluoromethyl Derivatives
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Received: June 5, 2013
Published online: && &&, 0000
Chem. Eur. J. 2013, 00, 0 – 0
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www.chemeurj.org
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B. Menjꢁn et al.
Gold Chemistry
S. Martꢁnez-Salvador, L. R. Falvello,
A. Martꢁn, B. Menjꢂn* ...... &&&& — &&&&
Gold(I) and Gold
Derivatives
ACHTUNGTRENNUNG(III) Trifluoromethyl
Race for gold! First the highly sensi-
tive carbonyl compound, second the
acetonitrile solvate, and third the well-
behaved thioether derivative (tht=te-
trahydrothiophene; see scheme)
depicted nearby are ranked, in that
order, as convenient synthons of the
“AuACTHUNGRTENUNG(CF3)” fragment.
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These are not the final page numbers!