The first cyanomethyl complex of gold, synthesized by reaction of a Au I complex with acetonitrile in the presence of a new guanidine N-superbase

Article abstract of DOI:10.1002/ejic.201000691

Herein we report on the synthesis of the new strong N-base and electron donor tdmegb [1,2,4,5-tetrakis(N,N′-dimethylethyleneguanidino)benzene]. Compared to the previously synthesized ttmgb [1,2,4,5- tetrakis(tetramethylguanidino)benzene], this compound turned out to be a slightly better electron donor and a slightly weaker base. In experiments in which [AuCl(PPH₃)] was dissolved in CH₃CN together with tdmegb, we observed the formation of the first cyanomethyl complex of Au, namely [Au(CH₂CN)(PPh₃)] in good yield. This reaction does not take place for ttmgb. Moreover, in CH₂Cl₂ solutions containing the three components [AuCl(PPh₃)], tdmegb and a nitrile (in large excess), only Au^I reduction leading to a [Au ₁₁Cl₃(PPh₃)₇] cluster is observed. Possible reaction mechanisms for this unusual reaction are discussed. The first cyanomethyl complex of gold, synthesized by reaction between an Au^I complex and acetonitrile in the presence of a new guanidine N-superbase C-H bond activation of acetonitrile by Au^I in combination with a newly designed nitrogen base leads to the first structurally characterized (cyanomethyl)gold complex.

Full text of DOI:10.1002/ejic.201000691

FULL PAPER
DOI: 10.1002/ejic.201000691
The First Cyanomethyl Complex of Gold, Synthesized by Reaction of a AuI
Complex with Acetonitrile in the Presence of a New Guanidine N-Superbase
Dimitri Emeljanenko,[a] Anastasia Peters,[a] Viktoriia Vitske,[a] Elisabeth Kaifer,[a] and
Hans-Jörg Himmel*[a]
Keywords: Gold / C–H acidity / C–H activation / Guanidine / Superbase
Herein we report on the synthesis of the new strong N-base
and electron donor tdmegb [1,2,4,5-tetrakis(N,NЈ-dimethyl-
ethyleneguanidino)benzene]. Compared to the previously
synthesized ttmgb [1,2,4,5-tetrakis(tetramethylguanidino)-
benzene], this compound turned out to be a slightly better
electron donor and a slightly weaker base. In experiments in
which [AuCl(PPH3)] was dissolved in CH3CN together with
tdmegb, we observed the formation of the first cyanomethyl
complex of Au, namely [Au(CH2CN)(PPh3)] in good yield.
This reaction does not take place for ttmgb. Moreover, in
CH2Cl2 solutions containing the three components
[AuCl(PPh3)], tdmegb and a nitrile (in large excess), only AuI
reduction leading to a [Au11Cl3(PPh3)7] cluster is observed.
Possible reaction mechanisms for this unusual reaction are
discussed.
synthesis,[6] e. g. for the synthesis of carbamates under mild
and safe conditions.[7] Metal complexes featuring cyano-
methyl ligands are also accessible via oxidative addition re-
actions. Hence oxidative addition of ClCH2CN to Pd0 or
Pt0 complexes such as Pt(PPh3)4 was previously shown to
give the cyanoalkyl PdII or PtII complexes [e. g. Pt(Cl)-
(CH2CN)(Ph3P)2].[8] Stoichiometric oxidative addition of
CH3CN occurs when [Ir(PPh3)4]Cl is dissolved in neat
CH3CN at room temperature.[9,10] On the other hand, oxi-
dative addition reactions of XCH2CN species (e. g., X =
hydrogen or halide) to AuI complexes were up to date not
observed. Moreover, no cyanomethyl complex of Cu, Ag
or Au was previously structurally characterized, although
(cyanomethyl)copper(I), CuCH2CN, can be synthesized by
decarboxylation of CuI or CuII cyanoacetates,[11] or in situ
from a CuI/(MeCN + nBuLi) mixture.[12] Its insolubility in
common organic solvents suggests a high degree of associa-
tion. Catalytic reactions involving nitriles and AuI catalysts
were recently described, but lead to transformation of the
cyano group into amides under mild conditions (a very im-
portant process, but not involving the methyl group).[13]
We recently developed a new class of strong electron do-
nors and N-bases consisting of aromatic systems to which
at least four guanidino groups are attached, and denoted
such compounds GFAs (guanidino-functionalized aromatic
donors).[14–17] Two representatives are ttmgb [1,2,4,5-tetra-
kis(tetramethylguanidino)benzene] and the superbase[18]
ttmgn [1,4,5,8-tetrakis(tetramethylguanidino)naphthalene],
see Scheme 1. In the last years, we studied a number of
transition metal (NiII, CoII, CuI, AgI and ZnII) and main
group element (especially AlIII) complexes of the guanidines
ttmgb and ttmgn and related guanidine ligands.[19] The re-
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Introduction
Deprotonation of an alkyl group is facilitated by reso-
nance and/or inductive effects leading to the stabilization of
the deprotonated species. Prominent examples of such C–
H acidic molecules include cyclopentadiene (C5H6) and β-
diketones (acetylacetone in its keto form). The C–H acidity
of compounds of the general formula CH3X was shown to
decrease in the order X = NO2 Ͼ CHO Ͼ CN Ͼ CCH
Ͼ CHCH2.[1] The cyanomethylene anion, (CH2CN)–, was
already subject of a number of experimental and theoretical
studies, evaluating in detail the inductive and resonance ef-
fects of the cyano moiety.[2] The C–H acidity of CH3CN in
H2O was determined recently by isotopic experiments.[3] In
these experiments, deprotonation of cyanomethyl by deu-
teriooxide ions (OD–) in D2O was followed by tracing the
appearance of deuterium-labeled cyanomethyl in the NMR
spectra, leading to a pKa value of 28.9.
Two ways have been established allowing the deproton-
ation of acetonitrile and generation of (CH2CN)– in quanti-
ties sufficient for synthetic chemistry in organic solutions.
The first one includes reaction of nBuLi with CH3CN lead-
ing to LiCH2CN.[4] Metal complexes can then be synthe-
sized by reaction with metal halide complexes such as
[NiCl2(Ph3P)2].[5] The cyanomethyl anion can also be gener-
ated in larger quantities by galvanostatic electrolysis of
CH3CN/Et4NPF6, and was in this form applied in organic
[a] Anorganisch-Chemisches Institut,
Ruprecht-Karls-Universität Heidelberg,
Im Neuenheimer Feld 270, 69120 Heidelberg, Germany
Fax: +49-6221-545707
E-mail: hans-jorg.himmel@aci.uni-heidelberg.de
wileyonlinelibrary.com
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FULL PAPER
Scheme 1. Lewis structures of the N-superbase ttmgb as well as ttmgn and tdmegb.
sults show that the GFA compounds are nucleophilic, and terized by their electron donor capacity. In Figure 1 (b) the
in their properties different to for instance Schwesinger’s P2 CV curves in CH3CN recorded for ttmgb and tdmegb are
phosphazene bases.[20]
compared. The two-electron wave observed at E1/2(CH3CN)
= –0.32 V vs. SCE for ttmgb [14] shifts to –0.36 V for
tdmegb, indicating that the latter is (under the conditions
of the experiment) a slightly superior electron donor. To
further compare the electron donor capacities we carried
out quantum chemical calculations on the gas-phase reac-
tion between (ttmgb)2+ and tdmegb to give ttmgb and
(tdmegb)2+. According to B3LYP/6-311G**, this reaction is
associated with a negative ∆E value of –28 kJmol–1. The
Results and Discussion
Synthesis and Characterization of 1,2,4,5-Tetrakis(N,NЈ-
dimethylethyleneguanidino)benzene (tdmegb)
The new GFA compound tdmegb (see Scheme 1) can be
obtained in good yield as the product of reaction between
1,2,4,5-tetraaminobenzene and activated 1,3-dimethyl-2-
imidazolidinone. The molecular structure as derived from
X-ray diffraction is visualized in Figure 1 (a). The C=N
double bond lengths measure 128.66(16)/129.03(15) pm,
and compare with values of 128.77(16)/129.10(16) pm for
ttmgb.[14] All guanidines of Scheme 1 have in common a
high N-basicity. The pKa value of the superbase btmgn [1,8-
bis(tetramethylguanidino)naphthalene] in CH3CN was esti-
mated to be 25.1 (experimentally derived estimate)[21] or
25.4 (calculated with the help of IPCM-B3LYP/6-
311+G**//HF/6-31G* calculations and an empirical for-
mula, IPCM = isodensity polarized continuum model), be-
ing thus higher than that of guanidine (24.1 in CH3CN ac-
cording to the calculations).[22,23] The calculated pKa value
in CH3CN is lower for the related 1,8-bis(N,NЈ-dimethyleth-
yleneguanidino)naphthalene. We expect pKa values in a
similar range for the three GFA molecules. We carried out
quantum chemical (B3LYP/6-311+G**) calculations to esti-
mate the pKa values of ttmgb and tdmegb [employing the
conductor-like polarisable continuum model (CPCM) to es-
timate the solvent effect]. With the empirical formula pro-
vided by Maksic´ et al.,[24] we arrived at pKa values of 25.3
and 23.8 for ttmgb and tdmegb, respectively, in CH3CN
solutions. For the reference guanidines HNC(NMe2)2 and
MeNC(NMe2)2, our calculated values (23.2 and 24.8,
respectively, also in CH3CN) are in pleasing agreement with
the experimental values in CH3CN (23.3 and 25.0, respec-
tively [25]). We also measured titration curves for tdmegb
(see Supporting Information). However, the individual pro-
tonation steps turned out to be difficult to separate. In ad-
Figure 1. a) Molecular structure of tdmegb as derived from X-ray
diffraction (hydrogen atoms omitted for sake of clarity). Ellipsoids
are drawn at the 50% probability level. Selected structural param-
eters (distances in pm, angles in deg.): N1–C1 141.57(15), N1–C4
128.66(16), N2–C4 138.12(16), N3–C4 139.24(16), N4–C3
141.60(15), N4–C9 129.03(15), N5–C9 138.71(15), N6–C9
137.32(15), C1–C2Ј 139.45(16), C1–C3 141.34(16), C2–C3
139.23(16), C1–N1–C4 123.76(10), C3–N4–C9 122.81(10), N2–C4–
N3 107.95(10), N5–C9–N6 108.42(10); b) CV curves recorded for
ttmgb and tdmegb (in CH3CN, electrode: SCE, scan speed
dition to their high basicity, ttmgb and tdmegb are charac- 100 mV s–1).
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The First Cyanomethyl-Gold Complex
∆HΘ and ∆GΘ values (at 298 K, 1 bar) are –27 and than in CH3CN. For comparison, in [PtH(CH2CN)-
–33 kJmol–1, respectively. In summary it can be concluded (PPh3)2], the methyl cyano group exhibits C–C and C–N
1
that tdmegb is a slightly weaker Brønsted base than ttmgb bond lengths of 143(2) and 112(3) pm.[30] In the H NMR
in CH3CN. It is, on the other hand, a slightly better electron spectrum, the methylene group of the cyanomethyl ligand
donor.
shows at δ = 1.64 ppm.
Reactions Involving AuI
In a series of experiments we heated mixtures of one of
the GFAs shown in Scheme 1 and [AuCl(PPh3)] in neat
CH3CN to reflux for a period of 2 h. Interestingly, no reac-
tion was observed when [AuCl(PPh3)] and ttmgb (in a 2:1
stoichiometric ratio) were dissolved in acetonitrile and the
reaction mixture heated to 80 °C.
Scheme 2. Product of the reaction between 1,3-dimethyl-2-methyl-
eneimidazoline and [AuCl(PPh3)] in THF.
The thermal stability of the 2 [Au(CH2CN)(PPh3)]/
tdmegb crystals was assessed in TG and DSC experiments.
Figure 3 displays the DSC and TG curves for temperatures
up to 300 °C. The DSC curve contains two peaks; the first
one corresponds to an endothermal process (peak around
170 °C, 68 kJmol–1) and is caused by melting of the solid
material. (The melting point was determined to be 162 °C.)
For comparison, the melting points of [AuCl(PPh3)] and
[Au(OCOCHCl2)(PPh3)] are 233–234 °C and 232 °C,
respectively.[31] From the TG curve it can be seen that there
is no mass loss at this point. However, the material already
changes its colour at this temperature indicating the forma-
tion of Au nanoparticles. It follows a peak due to an exo-
thermal process (peak around 207 °C, ca. –33 kJmol–1).
This peak is clearly associated with a mass loss (maximum
of the first derivative of the TG curve at ca. 215 °C) of ca.
36%. We explain this exothermal process with the elimi-
nation of all the PPh3 units (accounting in total for 34.5%
of the mass) and the formation of Au nanoparticles in an
irreversible exothermic process. This interpretation finds
support by the dark-red colour of the material after the
The guanidine ttmgn also showed no signs of reaction,
and only huge, bar-shaped crystals of the [AuCl(PPh3)] re-
actant precipitated from the reaction mixture. We only ob-
served a colouring of the solution, which we explain by the
formation of small amounts of Au nanoparticles. In con-
trast, the tdmegb/[AuClPPh3]/CH3CN reaction mixture
adopted a bright yellow colour, and upon cooling of the
mixture to room temperature yellow crystals precipitated.
Spectroscopic data in alliance with an XRD analysis of the
crystalline material revealed the formation of the new AuI
complex [Au(CH2CN)(PPh3)], crystallizing together with
0.5 equiv. of the neutral tdmegb molecules. Figure 2 illus-
trates the molecular structure. The tdmegb units separate
the AuI molecules from each other. The Au–C14 bond
length measures 208.5(2) pm. For comparison, in the com-
plex [Au{CH(SiMe3)2}(PPh3)], a Au–C bond length of
204.1(6) pm is realized,[26] being close to the values in
[AuPh(PPh3)] and related molecules in which an sp2 hy-
bridized carbon is bound to AuI (around 205 pm).[27,28]
A
significantly longer Au–C bond [208.7(3) pm] is found in
the Au complex arising from coordination of 1,3-dimethyl-
2-methylene-imidazoline to the [Ph3PAu] fragment (see
Scheme 2).[29] The Au–C bond in [Au(CH2CN)(PPh3)] is in
the same range. The C14–C15 bond [143.7(4) pm] is slightly
shorter, and the C15–N7 bond [115.1(3) pm] slightly longer
1
heat treatment (see Supporting Information) and by the H
and 31P NMR spectra recorded after dissolving the heated
material, which show no more sign of any aromatic protons
or P nuclei after heating. Interestingly, all attempts to sepa-
Figure 2. Molecular structure of 2[Au(CH2CN)PPh3]/tdmegb (hy-
drogen atoms omitted for sake of clarity). Thermal ellipsoids are
drawn at the 50% probability level. Selected structural parameters
(bond lengths in pm, angles in deg.): Au–C14 208.5(2), C14-C15
143.7(4), C15–N7 115.1(3), Au–P 227.22(8), P–C21 182.11(12), P–
C27 182.71(12), P–C33 182.88(11), P–Au–C14 177.25(9), Au–C14– Figure 3. DSC (top) and TG curves (N2 atmosphere, scan speed
C15 111.86(18), C14–C15–N7 179.0(3).
5 K min–1) measured for crystalline 2[Au(CH2CN)PPh3]/tdmegb.
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D. Emeljanenko, A. Peters, V. Vitske, E. Kaifer, H.-J. Himmel
FULL PAPER
rate the [Au(CH2CN)(PPh3)] complex from the tdmegb mo- not at all in the case of ttmgb (even for prolonged reaction
lecules by column chromatography (silica, MeOH/CH2Cl2, times). The reaction exhibits at least two channels, the first
1:4) were not successful. We observed decomposition of the leading to formation of the cyanomethyl complex (basicity
AuI complex under these conditions.
of the guanidine) and the second to reduction of AuI (elec-
No electron transfer from the tdmegb electron donor tron donor properties of the guanidine) to give Au clusters.
units to the AuI acceptors takes place. However, in solution The cyanomethyl complex is only formed if CH3CN is used
conditions can be found under which redox chemistry is in extremely large excess (as solvent). An Au11 cluster is
observed. Hence when [AuCl(PPh3)] is dissolved in CH2Cl2 formed if tdmegb and AuI are dissolved in CH2Cl2 solu-
solutions together with tdmegb and valeronitrile tions together with a nitrile excess. This poses the question
(C4H9CN), and the reaction mixture heated to a tempera- if the reduction channel is relatively fast in comparison to
ture of 60 °C for a period of 5 h, we observed no nitrile deprotonation in the case of ttmgb but not tdmegb, even
deprotonation but instead formation of the Au cluster if the nitrile is used as solvent. However, our experiments
[Au11Cl3(PPh3)7]. Similar clusters [Au11X3(P(aryl)3)7] (e. g., indicated that Au cluster formation occurs slowly in the
X = SCN, I, or CN) and [Au11(PMePh2)10]3+ were already ttmgb/[AuCl(PPh3)]/CH3CN reaction mixture, and in fact
structurally characterized, and were synthesized by re- the only indication for it is the colouring of the solution. It
duction of the triarylphosphane gold(I) complexes with is therefore unlikely that the reduction channel is much
NaBH4.[32] These Au11 clusters are of interest for several faster for ttmgb compared to tdmegb.
applications.[33]
In the light of these experimental findings, we think that
In preliminary experiments we also analysed with the it is plausible to suggest C–H activation by the AuI com-
help of NMR spectroscopy the reaction between plex.[35] The energy of a possible transition state is lowered
2 [Au(CH2CN)(PPh3)]/tdmegb and PhC(O)Cl, in the hope by interaction with the guanidine base as sketched in
to regain [AuCl(PPh3)] by transfer of the CH2CN group Scheme 3 (leading finally to HCl abstraction). Steric effects
and formation of 3-oxo-3-phenylpropanenitrile, PhC(O)- are then responsible for the differences between tdmegb and
CH2CN. A characteristic signal at δ = 4.1 ppm (due to the ttmgb. The tetramethylguanidino groups of ttmgb are steri-
1
methylene group) in the H NMR spectra indeed indicates cally more demanding, so that the transition state cannot
the formation of PhC(O)CH2CN already at –20 °C (see the be stabilized sufficiently. Interestingly, a similar transition
spectra in the Supporting Information).[34] However, the re- state was very recently suggested for arene-H activation by
action does not stop at this stage. The C–H acidity of the AuI.[36] It is clear that at the present stage we cannot prove
product is larger than that of CH3CN, and therefore further this proposed mechanism. However, this is in line with the
deprotonation reactions occur leading to a product mixture. experimental findings.
More work in this direction is on the way.
Possible Reaction Pathway/Mechanism
How can the formation of the cyanomethyl AuI complex
be explained? The first idea is that the guanidine base
tdmegb simply deprotonates the CH3CN and then the
CH2CN– anions (being present in small concentrations) re-
act with the AuI complex in a ligand-substitution reaction
Scheme 3. Possible transition state of the reaction.
(replacement of chloride by cyanomethyl). However, the ex-
perimental results do not support this simple picture. First
of all the basicity of the tdmegb base is not high enough
to generate significant amounts of the cyanomethyl anion.
Deprotonation of CH3CN by the organometallic base
Conclusions
MeLi can be detected directly, for instance by NMR spec-
With 1,2,4,5-tetrakis(N,NЈ-dimethylethyleneguanidino)-
troscopy. In contrast, the NMR spectrum of a CH3CN benzene (tdmegb), we prepared a new strong N-base and
solution of the guanidine tdmegb showed no signal due to electron donor. This molecule is related to the previously
a reaction product of any sort. Of course, it could be argued reported molecule 1,2,4,5-tetrakis(tetramethylguanidino)-
that only small concentrations of the cyanomethyl anion benzene (ttmgb). The guanidine tdmegb is a slightly weaker
are sufficient. However, even more difficult to explain is the base and a slightly better electron donor than ttmgb. Sur-
fact that the weaker base, tdmegb, promotes the reaction prisingly, if tdmegb is dissolved together with the AuI com-
while the stronger base, ttmgb, does not. One possibility plex [AuCl(PPh3)] in CH3CN, the complex [Au(CH2CN)-
would be that the equilibrium is shifted to the product side (PPh3)] is formed in good yield. On the other hand, the
through precipitation of the Au complex [Au(CH2CN)- guanidine ttmgb, although slightly more basic than tdmegb,
(PPh3)] for reactions with tdmegb, but not ttmgb. On the shows no sign of reaction. Several experiments were carried
other hand, the product can clearly be observed with NMR out to obtain more information about this reaction, and a
already in the reaction mixture in the case of tdmegb, but possible approach to the reaction mechanism is presented
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The First Cyanomethyl-Gold Complex
(1521.28): calcd. C 52.11, H 5.04, N 12.89; found C 51.91, H 5.04,
N 12.82. H NMR (600 MHz, CD2Cl2): δ = 1.64 (s, 4 H, -CH2-),
which is in line with these results. More experiments and
also quantum chemical calculations will be carried out in
the future to support or disprove this idea for the mecha-
nism. We will extend the analysis to other LAuCl com-
plexes. In addition similar reactions of other alkyl com-
pounds (e. g., CH3NO2, CH3CHO or PhCH2CCH) will be
studied. Finally, the new synthetic method might open up
the possibility of designing catalytic C–H activation reac-
tions.
1
2.63 (s, 24 H, -CH3), 3.15 (s, 16 H, -CH2-), 6.06 (s, 2 H, Ar-H),
7.52 (m, 30 H, P-Ar-H). 13C NMR (150 MHz, CD2Cl2): δ = 5.59
(s, -CH2-CN) 35.28 (s, -CH3), 49.18 (s, -CH2-), 116.41 (s, CAr),
2/3
127.97, 129.71 (d,
J
C,P
= 11.06 Hz), 130.63 (d, 1JC,P = 52.89 Hz),
132.04 (d, 4J = 2.40), 134.75 (d,
J
C,P
= 13.72), 135.82, 154.01.
2/3
31P NMR (242 MHz, CD Cl ): δ = 41.96. IR (Nujol): ν = 2193
˜
2
2
(m), 1626 (s), 1273 (w), 1091 (w), 1036 (w) cm–1. IR (CsI): ν = 2858
˜
(s), 2201 (s), 1618 (s), 1388 (s), 1288 (s), 1143 (m), 1036 (s), 972 (s),
757 (s), 638 (w), 538 (s) cm–1. UV/Vis (CH3CN, c = 4.94ϫ10–4):
λmax(ε, dm3 mol–1 cm–1) = 340 (9898), 423 (155) nm. MS (FAB+):
m/z (%) = 459.0 (80) [AuPPh3]+, 500.1 (40) [Au(CH2CN)PPh3
+
Experimental Section
H]+, 523.3 (100) [tdmegb + H]+, 721.2 (10) [tdmegb + 2H + Au]+,
1022.3 (2) [tdmegb + H + Au(CH2CN)PPh3]+. MS (ESI–): m/z
(%) = 249.29 (100) [Au(CH2CN)PPh3]2–, 521.59 (45) [tdmegb-
General: All synthetic work was carried out under inert gas atmo-
sphere using standard Schlenk techniques. [AuCl(PPh3)] was pur-
chased from ChemPur. The guanidines ttmgb and ttmgn were pre-
pared as described in the literature.[14,16] NMR spectra were mea-
sured on a Bruker AVII-400 or a Bruker AVIII-600 spectrometer
at a temperature of 23 °C and referenced to known standards, and
IR spectra were recorded with a BIORAD Excalibur FTS 3000. A
Perkin–Elmer Lambda 19 spectrometer was used for UV/Vis mea-
surements.
H]–. Crystal data for C66H76Au2N14P2, Mr
=
1521.28,
¯
0.30ϫ0.30ϫ0.27 mm3, monoclinic, space group P1,
9.3030(19), b = 10.893(2), c = 15.311(3) Å, α = 85.28(3), β =
89.43(3)°, γ = 89.72(3), V = 1546.2(5) Å3, Z = 1, dcalc
a
=
=
1.634 Mgm–3, Mo-Kα radiation (graphite-monochromated, λ =
0.71073 Å), T = 100 K, θrange 2.19 to 29.99°. Reflections measd.
16331, indep. 8942, Rint = 0.0187. Final R indices [IϾ2σ(I)]: R1 =
0.0223, wR2 = 0.0537.
tdmegb: To a solution of 1,3-dimethylimidazolidin-2-one (2.0 mL,
18.7 mmol) in anhydrous CH3Cl (15 mL) was slowly added via sy-
ringe oxalyl chloride (7.9 mL, 92.0 mmol, 4.9 equiv.). The mixture
was refluxed for 20 h at 80 °C. After solvent removal in vacuo, the
residue was washed with dry Et2O. The remaining pale yellow salt
was dissolved in CH3CN (12 mL) and added dropwise to a CH3CN
solution (25 mL) containing 1,2,4,5-tetraaminobenzene (0.83 g,
2.9 mmol) and triethylamine (3.5 mL, 43.0 mmol) at a temperature
of 0 °C. Subsequently the reaction mixture was stirred for 1.5 h
at 0 °C. Removal of the solvent in vacuo led to a brown-greenish
precipitate which was then redissolved in water. After addition of
NaOH (20%) a white precipitate was formed. The precipitate was
filtered and washed three times with cold water and dried under
vacuum to afford tdmegb (1.14 g, 2.2 mmol, 74%) as a white pow-
der. C26H42N12 (522.70): calcd. C 59.74, H 8.10, N 32.16; found C
58.08, H 8.09, N 31.21. 1H NMR (600.13 MHz, CD3CN): δ = 5.95
(s, 2 H, CHAr), 3.13 (s, 16 H, -CH2-), 2.58 (s, 24 H, -CH3). 13C
NMR (150.92 MHz, CD3CN): δ = 154.13, 136.19, 116.76 (CAr),
[Au11Cl3(PPh3)7]: The guanidine tdmegb (52.8 mg, 101 µmol) was
dissolved in 6 mL CH2Cl2. Then 100 mg (202 µmol) [AuCl(PPh3)]
and a large excess of valeronitrile (83.9 mg, 1010 µmol) were added,
and the reaction mixture stirred for a period of 5 h at a temperature
of 60 °C. Subsequently the solvent was partially removed leaving
ca. ca. 1 mL. The crude product was purified by column
chromatography (silica gel, EtOH/CH2Cl2, 1:4). After removal of
the solvent, one obtains 100 mg solid. NMR spectra show that this
solid consists of a 1:1 mixture of the cluster [Au11Cl3(PPh3)7] and
[AuCl(PPh3)]. The yield of [Au11Cl3(PPh3)7] can thus be estimated
to be 12 µmol (65.2%). NMR spectra measured at several stages
of the reaction show that the valeronitrile is not deprotonated.
Moreover, the NMR spectra signal decomposition of the
1
[Au11Cl3(PPh3)7] cluster for prolonged reaction times at 60 °C. H
NMR (400 MHz, CD2Cl2): δ = 6.69 (2 H, Ar-H), 6.94 (1 H, Ar-
H), 7.32 (2 H, Ar-H). 13C NMR (100 MHz, CD2Cl2): δ = 129.08,
130.39, 134.81. 31P NMR (161 MHz, CD2Cl2): δ = 52.32. RFCluster
(EtOH/CH2Cl2, 1:4): 0.42.
49.21 (-CH -), 35.12 (-CH ). IR (CsI): ν = 2932 (w), 2834 (w), 1644
˜
2
3
(vs), 1483 (s), 1443 (m), 1391 (m), 1274 (m), 1244 (m), 1152 (w),
1037 (m), 973 (w), 897 (w), 804 (w), 718 (w), 633 (w) cm–1.
UV/Vis (CH3CN, c = 1.80ϫ10–5 molL–1): λmax (ε, dm3 mol–1 cm–1):
X-ray Crystallographic Study: Suitable crystals were taken directly
out of the mother liquor, immersed in perfluorinated polyether oil,
and fixed on top of a glass capillary. Measurements were made on
a Nonius-Kappa CCD diffractometer with low-temperature unit
using graphite-monochromated Mo-Kα radiation. The temperature
was set to 100 K. The data collected were processed using the stan-
dard Nonius software.[37] All calculations were performed using the
SHELXT-PLUS software package. Structures were solved by direct
methods with the SHELXS-97 program and refined with the
SHELXL-97 program.[38,39] Graphical handling of the structural
data during solution and refinement was performed with
XPMA.[40] Atomic coordinates and anisotropic thermal parameters
of non-hydrogen atoms were refined by full-matrix least-squares
calculations.
253 (2.99ϫ104), 345 (1.08ϫ104) nm. CV (CH3CN,
c =
1.80ϫ10–3 molL–1, vs. SCE). E1/2 = –0.36 V. MS (FAB+): m/z (%)
= 523 (100) [tdmegb(H)]+. Crystal data for C26H42N12·4H2O, Mr
= 594.78, 0.40ϫ0.40ϫ0.35 mm3, monoclinic, space group C2/c, a
= 20.994(4), b = 10.119(2), c = 16.139(3) Å, β = 113.97(3)°, V =
3132.9(13) Å3, Z = 4, dcalc = 1.261 Mgm–3, Mo-Kα radiation
(graphite-monochromated, λ = 0.71073 Å), T = 100 K, θrange 2.12
to 30.04°. Reflections measd. 9118, indep. 4591, Rint = 0.0299. Fi-
nal R indices [IϾ2σ(I)]: R1 = 0.0455, wR2 = 0.1313.
2[Au(CH2CN)(PPh3)]/tdmegb: To a solution of 200 mg (362 µmol)
tdmegb in 18 mL acetonitrile 358 mg (724 µmol) [AuClPPh3] were
added. The reaction mixture was stirred for a period of 2 h at
80 °C. Subsequently it was allowed to cool to room temp. and fil-
tered. Half of the solvent was removed from the solvent, and the
appearing precipitate re-dissolved by mild heating. Over night crys-
tals were formed. After filtration and drying under vacuum 303 mg
(199 µmol) 2[Au(CH2CN)(PPh3)]/tdmegb were obtained as yellow-
golden shining crystals (52% yield). M. p. 162 °C. C66H76Au2N14P2
CCDC-770432 (for tdmegb) and -779106 (for 2[Au(CH2CN)PPh3]/
tdmegb) contain the supplementary crystallographic data for this
paper. These data can be obtained free of charge from The Cam-
bridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
Supporting Information (see also the footnote on the first page of
this article): It includes a titration curve for tdmegb in water, pho-
Eur. J. Inorg. Chem. 2010, 4783–4789
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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4787

D. Emeljanenko, A. Peters, V. Vitske, E. Kaifer, H.-J. Himmel
FULL PAPER
tos before and after heating 5 to a temperature of 300 °C, 1H NMR
spectra (200 MHz, CD2Cl2) for the reaction between 5 and PhC-
(O)Cl and the results of the quantum chemical calculations on the
basicity and electron donor capacity of ttmgb and tdmegb
C. Neuhäuser, E. Kaifer, H. Wadepohl, H.-J. Himmel, Eur. J.
Inorg. Chem. 2009, 2170–0178; f) A. Peters, C. Trumm, M. Re-
inmuth, D. Emeljanenko, E. Kaifer, H.-J. Himmel, Eur. J. Inorg.
Chem. 2009, 3791–3800; g) M. Reinmuth, U. Wild, E. Kaifer,
M. Enders, H. Wadepohl, H.-J. Himmel, Eur. J. Inorg. Chem.
2009, 4795–4808; h) V. Vitske, C. König, E. Kaifer, O. Hübner,
H.-J. Himmel, Eur. J. Inorg. Chem. 2010, 115–126; i) P. Ro-
quette, A. Maronna, A. Peters, E. Kaifer, H.-J. Himmel, Ch.
Hauf, V. Herz, E.-W. Scheidt, W. Scherer, Chem. Eur. J. 2010,
16, 1336–1350; j) D. Emeljanenko, A. Peters, N. Wagner, J.
Beck, E. Kaifer, H.-J. Himmel, Eur. J. Inorg. Chem. 2010, 1839–
1846; k) C. Trumm, O. Hübner, E. Kaifer, H.-J. Himmel, Eur.
J. Inorg. Chem. 2010, 3102–3108.
a) R. Schwesinger, H. Schlemper, C. Hasenfratz, J. Willaredt,
T. Dambacher, T. Breuer, C. Ottaway, M. Fletschinger, J. Boele,
H. Fritz, D. Putzas, H. W. Rotter, F. G. Bordwell, A. V. Satish,
G.-Z. Ji, E.-M. Peters, K. Peters, H. G. von Schnering, L. Walz,
Liebigs Ann. 1996, 1055–1081; b) I. A. Koppel, R. Schwesinger,
T. Breuer, P. Burk, K. Herodes, I. Koppel, I. Leito, M. Mis-
hima, J. Phys. Chem. A 2001, 105, 9575–9586.
V. Raab, J. Kipke, R. M. Gschwind, J. Sundermeyer, Chem.
Eur. J. 2002, 8, 1682–1693.
B. Kovacˇevic´, Z. B. Maksic´, Chem. Eur. J. 2002, 8, 1694–1702.
D. Margetic, in: Superbases for Organic Synthesis (Ed.: T. Ishi-
kawa), chapter 2, p. 9–48, Wiley 2009, and references given
therein.
B. Kovac´evic´, Z. B. Maksic´, Org. Lett. 2001, 3, 1523–1526.
R. Schwesinger, Nachr. Chem. Tech. Lab. 1990, 38, 1214–1226,
and references given therein.
S. Bommers, H. Beruda, N. Dufour, M. Paul, A. Schier, H.
Schmidbaur, Chem. Ber. 1995, 128, 137–142.
Acknowledgments
The authors gratefully acknowledge continuous financial support
by the Deutsche Forschungsgemeinschaft (DFG).
[1] A. Pross, D. J. DeFrees, B. A. Levi, S. K. Pollack, L. Radom,
W. J. Hehre, J. Org. Chem. 1981, 46, 1693–1699.
[2] D. A. Dixon, P. A. Charlier, P. G. Gassman, J. Am. Chem. Soc.
1980, 102, 3957–3959.
[3] J. P. Richard, G. Williams, J. Gao, J. Am. Chem. Soc. 1999, 121,
715–726.
[4] E. M. Kaiser, C. R. Hauser, J. Org. Chem. 1968, 33, 3402–3404.
[5] P. R. Albuquerque, A. R. Pinhas, J. A. Krause-Bauer, Inorg.
Chim. Acta 2000, 298, 239–244.
[6] See, for example: a) L. Rossi, M. Feroci, A. Inesi, Mini-Rev.
Org. Chem. 2005, 2, 343–357; b) M. Feroci, M. Orsini, L. Pal-
ombi, L. Rossi, A. Inesi, Electrochim. Acta 2005, 50, 2029–
2036.
[7] M. Feroci, M. A. Casadei, M. Orsini, L. Palombi, A. Inesi, J.
Org. Chem. 2003, 68, 1548–1551.
[8] a) K. Suzuki, H. Yamamoto, S. Kanie, J. Organomet. Chem.
1974, 73, 131 –136; b) R. Ros, R. A. Michelin, R. Bataillard,
R. Roulet, J. Organomet. Chem. 1977, 139, 355–359; c) R.
McCrindle, G. Ferguson, A. J. McAlees, M. Parvez, P. J. Rob-
erts, J. Chem. Soc., Dalton Trans. 1982, 1699–1708.
[9] A. D. English, T. Herskovitz, J. Am. Chem. Soc. 1977, 99,
1648–1649.
[10] M. G. Crestani, A. Steffen, A. M. Kenwright, A. S. Batsanov,
J. A. K. Howard, T. B. Marder, Organometallics 2009, 28,
2904–2914.
[20]
[21]
[22]
[23]
[24]
[25]
[26]
[27]
[28]
M. E. Olmos, Adv. Organomet. Chem. 2005, 52, 77–141.
A. S. K. Hashmi, T. D. Ramamurthi, F. Rominger, J. Or-
ganomet. Chem. 2009, 694, 592–597.
A. Fürstner, M. Alcarazo, R. Goddard, C. W. Lehmann, An-
gew. Chem. 2008, 120, 3254–3258; Angew. Chem. Int. Ed. 2008,
47, 3210–3214.
[29]
[30]
[31]
[32]
A. Del Pra, E. Forsellini, G. Bombieri, R. A. Michelin, R. Ros,
J. Chem. Soc., Dalton Trans. 1979, 1862–1866.
[11] T. Tsuda, T. Nakatsuka, T. Hirayama, T. Saegusa, J. Chem.
Soc., Chem. Commun. 1974, 557–558.
[12] E. J. Corey, I. Kuwajima, Tetrahedron Lett. 1972, 13, 487–489.
[13] R. S. Ramón, N. Marion, S. P. Nolan, Chem. Eur. J. 2009, 15,
8695–8697.
J. Skoweranda, W. Wieczorek, M. Bukowska-Strzyzewska, A.
˙
Grodzicki, J. Crystallogr. Spectrosc. Res. 1991, 22, 527–531.
See, for example: a) M. McPartlin, R. Mason, L. Malatesta, J.
Chem. Soc. C 1969, 334; b) F. Cariati, L. Naldini, Inorg. Chim.
Acta 1971, 5, 172–174; c) P. A. Bartlett, B. Bauer, S. J. Singer,
J. Am. Chem. Soc. 1978, 100, 5085–5089; d) R. C. B. Copley,
D. M. P. Mingos, J. Chem. Soc., Dalton Trans. 1996, 479–489.
See, for example, for some recent work: a) R. K. Smith, S. U.
Nanayakkara, G. H. Woehrle, T. P. Pearl, M. M. Blake, J. E.
Hutchison, P. S. Weiss, J. Am. Chem. Soc. 2006, 128, 9266–
9267; b) S. Ariyasu, A. Onoda, R. Sakamoto, T. Yamamura,
Dalton Trans. 2009, 3742–3747; c) S. Ariyasu, A. Onoda, R.
Sakamoto, T. Yamamura, Bioconjugate Chem. 2009, 20, 2278–
2285.
[14] A. Peters, E. Kaifer, H.-J. Himmel, Eur. J. Org. Chem. 2008,
5907–5914.
[15] A. Peters, C. Trumm, M. Reinmuth, D. Emeljanenko, E.
Kaifer, H.-J. Himmel, Eur. J. Inorg. Chem. 2009, 3791–3800.
[16] V. Vitske, C. König, O. Hübner, E. Kaifer, H.-J. Himmel, Eur.
J. Inorg. Chem. 2010, 115–126.
[33]
[17] A. Peters, M. Reinmuth, U. Wild, S. Leingang, P. D. Marzenell,
E. Kaifer, H.-J. Himmel, Eur. J. Inorg. Chem. 2010, submitted.
[18] There is an approved and clear definition of the term “su-
perbase” from Caubère, see: Chem. Rev. 1993, 93, 2317–2334,
and also the first chapter of the comprehensive book Su-
perbases for Organic Synthesis (Ed.: T. Ishikawa, Wiley, 2009).
It reads: The term “superbase” should only be applied to bases
resulting from a mixing of two (or more) bases leading to a
new basic species possessing inherent new properties. The term
“superbase” does not mean a base is thermodynamically and/or
kinetically stronger than another; instead it means that a basic
reagent is created by combining the characteristics of several dif-
ferent bases. The guanidine ttmgn combines the basicity of gua-
nidino groups with Alder’s concept of a proton sponge. There-
fore ttmgn clearly is a “superbase”.
[19] a) U. Wild, P. Roquette, E. Kaifer, J. Mautz, H. Wadepohl, H.-
J. Himmel, Eur. J. Inorg. Chem. 2008, 1248–1257; b) A. Peters,
U. Wild, O. Hübner, E. Kaifer, J. Mautz, H.-J. Himmel, Chem.
Eur. J. 2008, 14, 7813–7821; c) U. Wild, O. Hübner, A. Ma-
ronna, M. Enders, E. Kaifer, H. Wadepohl, H.-J. Himmel, Eur.
J. Inorg. Chem. 2008, 4440–4447; d) A. Peters, E. Kaifer, H.-J.
Himmel, Eur. J. Org. Chem. 2008, 5907–5914; e) D. Domide,
[34]
[35]
R. Barhdadi, J. Gal, M. Heintz, M. Troupel, J. Périchon, Tetra-
hedron 1993, 49, 5091–5098.
C–H activation with molecular gold complexes was reported
previously, see: a) S. Komiya, T. Sone, Y. Usui, M. Hirano, A.
Fukuoka, Gold Bull. 1996, 29, 131–136; b) A. S. K. Hashmi,
R. Salathé, T. M. Frost, L. Schwarz, J.-H. Choi, Appl. Catal.
A 2005, 291, 238–246; c) A. S. K. Hashmi, S. Schäfer, M.
Wölfle, C. D. Gil, P. Fischer, A. Laguna, M. C. Blanco, M. C.
Gimeno, Angew. Chem. 2007, 119, 6297–6300; Angew. Chem.
Int. Ed. 2007, 46, 6184–6187; d) I. I. F. Boogaerts, S. P. Nolan,
J. Am. Chem. Soc., DOI: 10.1021/ja103429q.
P. Lu, T. C. Boorman, A. M. Z. Slawin, I. Larrosa, J. Am.
Chem. Soc., DOI: 10.1021/ja101525w.
DENZO-SMN, Data processing software, Nonius 1998; http://
www.nonius.com.
[36]
[37]
[38]
a) G. M. Sheldrick, SHELXS-97, Program for Crystal Struc-
ture Solution, University of Göttingen, Germany, 1997; http://
4788
www.eurjic.org
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2010, 4783–4789

The First Cyanomethyl-Gold Complex
shelx.uni-ac.gwdg.de/SHELX/index.html ; b) G. M. Sheldrick,
SHELXL-97, Program for Crystal Structure Refinement,
University of Göttingen, Germany, 1997; http://shelx.uni-
ac.gwdg.de/SHELX/index.html.
[40]
L. Zsolnai, G. Huttner, XPMA, University of Heidelberg, Ger-
many, 1994; http://www.uni-heidelberg.de/institute/fak12/AC/
huttner/software/software.html.
Received: June 24, 2010
Published Online: August 26, 2010
[39] International Tables for X-ray Crystallography, vol. 4, Kynoch
Press, Birmingham, U.K., 1974.
Eur. J. Inorg. Chem. 2010, 4783–4789
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
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