Transfer of organic groups to gold using organotin compounds

Article abstract of DOI:10.1016/j.jorganchem.2010.10.060

PhSnMe₃ undergoes transmetallation with [AuCl(EPh₃)] (E = P, As) in refluxing toluene forming [AuPh(EPh₃)] and Me ₃SnCl. The analogous ⁿBu derivative does not transmetallate, even under forcing conditions. Similarly, 1-(trimethylstannyl) naphthalene and 1-(trimethylstannyl)-8-iodonaphthalene react with [AuCl(PPh ₃)] to give good yields of the corresponding naphthylgold(I) complexes which were spectroscopically and structurally characterised.

Full text of DOI:10.1016/j.jorganchem.2010.10.060

Journal of Organometallic Chemistry 696 (2011) 1244e1247
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Transfer of organic groups to gold using organotin compounds
*
Nadine Meyer, Sivatharushan Sivanathan, Fabian Mohr
Fachbereich C - Anorganische Chemie, Bergische Universität Wuppertal, 42119 Wuppertal, Germany
a r t i c l e i n f o
a b s t r a c t
Article history:
PhSnMe3 undergoes transmetallation with [AuCl(EPh3)] (E ¼ P, As) in refluxing toluene forming [AuPh
(EPh3)] and Me3SnCl. The analogous nBu derivative does not transmetallate, even under forcing condi-
tions. Similarly, 1-(trimethylstannyl)naphthalene and 1-(trimethylstannyl)-8-iodonaphthalene react with
[AuCl(PPh3)] to give good yields of the corresponding naphthylgold(I) complexes which were spectro-
scopically and structurally characterised.
Received 28 September 2010
Received in revised form
26 October 2010
Accepted 28 October 2010
Ó 2010 Elsevier B.V. All rights reserved.
Keywords:
Transmetallation
Organotin compounds
Arylgold(I) compounds
X-ray structure
1. Introduction
the 1,8-naphthalenediyl unit to a dinuclear gold(I) centre in good
yields under mild conditions (Fig. 1) [18]. It should be mentioned
Traditionally, organolithium compounds or Grignard reagents
are used as transmetallating agents in the synthesis of organogold
compounds [1e3]. Especially reactions involving organolithium
species tend to cause problems with gold precursors, as the
reducing properties of the organolithiums lead to formation of
metallic gold thus lowering yields. Furthermore, organolithium
compounds and Grignard reagents are not compatible with several
functional groups and also require rigorous exclusion of moisture
and air. From the late 1970’s Eaborn and Pidcock published a series
of papers in which the use of organotin compounds as aryl-transfer
agents to various platinum precursors under mild conditions was
described [4e10]. Some years later the group of Brune used the
same approach to transfer various naphthyl derivatives to a plat-
inum(II) centre [11e13]. It was also shown that organotin reagents
can transfer organic groups to palladium, although not always the
desired aryl unit was transferred [14,15]. There is also precedence
for the use of an organotin compound as transmetallating agent in
gold(III) chemistry (Fig. 1) [16]. One report also details the transfer
of a metal-alkyne unit via the tin compound to a gold(I) centre (as
an example an iron derivative is shown in Fig. 1) [17]. Based on
these results, we wondered if readily accessible and air- and
moisture-stable aryltin compounds would also undergo trans-
metallation with gold(I) species. Indeed, we recently communi-
cated that 1,8-bis(trimethylstannyl)naphthalene readily transfers
here, that boronic acids have also been used to transfer aryl groups
to gold under reasonably mild but albeit time consuming condi-
tions (iPrOH reflux for a minimum of 24 h) [19e21].
Herein we report further results of reactions of aryltin
compounds with gold(I) precursors to learn more about the scope
and generality of this process. Furthermore, we report the successful
transmetallation of a halide-functionalised aryltin compound to
a gold(I) centre, something which is not possible using organo-
lithium species or Grignard reagents.
2. Results and discussion
Initially we examined the reaction of PhSnMe3 and PhSnnBu3
with [AuCl(PPh3)] and [AuCl(AsPh3)] to study the effect of the alkyl
substituents on the transmetallation process (Scheme 1). Since
many nBu3SnR type compounds are commercially available and
they are less toxic than their methyl counterparts, a successful
transmetallation to gold would give convenient access to a variety
of structurally diverse organogold(I) compounds.
Unfortunately, we found that when using the nBu derivative no
transmetallation occurs, even under harsh conditions (refluxing
toluene for 18 h). Only starting materials and some decomposition
(elemental gold) could be observed. The methyl analogue in
contrast, readily transfers the phenyl group to gold in refluxing
toluene in only 2 h. Based on these results, we focused on trime-
thyltin derivatives for our subsequent studies.(Scheme 2)
Given our previous success of transferring the 1,8-naph-
thalenediyl unit to gold(I), we now examined some mononuclear
* Corresponding author.
E-mail address: fmohr@uni-wuppertal.de (F. Mohr).
0022-328X/$ e see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2010.10.060

N. Meyer et al. / Journal of Organometallic Chemistry 696 (2011) 1244e1247
1245
PPh3
Au
R
Cl
R
SnMe3
1. [AuCl3(tht)]
2. Ph3P
n
Sn Pr2
[AuCl(PPh3)]
Au
PPh3
1
R = H ( )
R = I (2)
3
R = H ( )
R = I (4)
Scheme 2.
[AuCl(PPh3)]
Pd cat.
Fe
PPh2
Fe
C
In summary, we have shown that Me3SnAr derivatives readily
undergo transmetallation with gold(I) species under mild condi-
tions. With this methodology it was possible to prepare a iodo-
functionalised naphthylgold(I) compound, which is not accessible
by other methods.
C
Ph2P
Ph2P
C
Ph2P
C
AuPPh3
SnPh3
PPh2
PPh2
Me3Sn
SnMe3
[Au2Cl2(µ-dppe)]
3. Experimental
Au Au
3.1. General
1H, 13C and 31P{1H} NMR spectra were recorded on a 400 MHz
Bruker Avance or 600 MHz Bruker Avance III spectrometer.
Chemical shifts are quoted relative to external SiMe4 (1H, 13C) and
85% H3PO4 (31P). Elemental analyses were performed by staff of the
microanalytical laboratory of the University of Wuppertal. All
reactions were carried out under dinitrogen using standard Schlenk
techniques. 1,8-Diiodonaphthalene and 1-(trimethystannyl)naph-
thalene (1) were prepared as described in the literature [24,25].
[AuCl(PPh3)] and [AuCl(AsPh3)] were prepared by reacting [AuCl
(tht)] (tht ¼ tetrahydrothiophene) [26] with Ph3P or Ph3As,
respectively. All other chemicals and solvents (anhydrous or extra
dry grade) were sourced commercially and used as received.
Fig. 1. Examples of organotin species used as transmetallating agents in gold
chemistry.
naphthalene derivatives. 1-(Trimethylstannyl)naphthalene (1)
reacts with [AuCl(PPh3)] in toluene at 70ꢀ for 2 h to give the gold(I)
naphthyl complex [Au(nap)(PPh3)] (3) in 88% yield. The compound
was previously prepared using 1-lithionaphthalene in a yield of
68% [22]. Similarly, the 8-iodo derivative (4) was also prepared by
reacting 1-(trimethylstannyl)-8-iodonaphthalene (2) with [AuCl
(PPh3)] in hexane at room temperature for 2 h. It is worth noting
here, that such a halide-functionalised organogold(I) complex
cannot be prepared using organolithium compounds or Grignard
reagents. Compounds 2e4 were characterised spectroscopically
(see Experimental part for details) and also by single crystal X-ray
diffraction; the molecular structures are shown in Figs. 2e4.
The organotin compound 2 shows the expected tetrahedral
environment about the tin centre, with typical distances and angles
for aryl-trimethyl tin compounds. Although the IeSn separation in
2 of 3.46 Å is less than the sum of the Van der Waals radii (4.15 Å),
the Me3Sn unit is bent out of the plane of the naphthyl backbone by
ca. 0.4 Å, while the iodine atom is bent by ca. 0.3 Å in the opposite
direction. This deviation from the naphthalene plane of the peri
substituents is however very small when compared to that of other
1,8-dimetallated naphthalenes [23]. The gold complexes 3 and 4 are
structurally very similar; the AueC and AueP bond lengths differ
only slightly from each other. Similarly, the expected linear angle
(174.8ꢀ) about the gold centre is practically identical in both
compounds. The distance between the gold and iodine atoms in
complex 4 [3.1317(7) Å] is less than the sum of the Van der Waals
radii (3.64 Å) but longer than a gold-iodine bond (typically around
2.5 Å). This weak attractive interaction between the two peri
substituents may be responsible for the only very slight buckling of
the molecule: the gold atom lies 0.4 Å above the naphthalene plane,
whilst the iodine atom is located less than 0.2 Å below this plane.
3.2. Transmetallation experiments
Equimolar amounts (ca. 0.19 mmol) of the appropriate organotin
compound and [AuCl(EPh3)] (E ¼ P, As) were heated in toluene for
different periods of time. The volatiles were subsequently removed
and the residue examined by NMR spectroscopy. The identity of the
formed [AuPh(PPh3)] was confirmed by comparison to literature
data [19]. The arsenic derivative was characterised as follows: 1H
NMR (400 MHz, CDCl3):
3 H, m and p-Ph), 7.42e7.37 (m, 15 H, AsPh3). 13C NMR (101 MHz,
CDCl3):
¼ 141.22 (C-Au), 137.45 (C-As), 133.60 (o-AsPh3), 129.18
d
¼ 7.64e7.61 (m, 2 H, o-Ph), 7.50e7.44 (m,
d
EPh3
Au
SnR3
[AuCl(EPh3)]
- R3SnCl
Fig. 2. Molecular structure of 2. Ellipsoids show 50% probability levels. Hydrogen
atoms have been omitted for clarity. Selected bond distances [Å]: Sn1-C1 2.182(4), Sn-
C11 2.147(5), Sn1-C12 2.135(4), Sn1-C13 2.147(5), I1-C9 2.118(5). Selected angles [ꢀ]:
C12-Sn1-C13 118.6(2), C12-Sn1-C1 102.94(19), C13-Sn1-C11 102.5(2), C12-Sn1-C1
114.47(17), C13-Sn1-C1 111.76(18), C11-Sn1-C1 104.09(17).
n
R = Me, Bu
E = P, As
Scheme 1.

1246
N. Meyer et al. / Journal of Organometallic Chemistry 696 (2011) 1244e1247
7.46e7.41 (m, 1 H, nap-H3), 7.18e7.13 (m, 1 H, nap-H6), 0.57 (s, 9 H,
SnMe3). 13C NMR (101 MHz, CDCl3):
d
¼ 139.69 (1 C, nap-C7),138.92
(1 C, nap-C2), 130.73 (1 C, nap-C5), 130.28 (1 C, nap-C4), 126.28 (1 C,
nap-C6),125.40 (1 C, nap-C5), ꢁ0.88 (3 C, SnMe3). The signals of the
quaternary carbon atoms could not be detected. Anal. calc. for
C13H15ISn (417.92): C, 37.45; H, 3.63. Found: C, 37.57; H, 3.12%. X-ray
quality crystals were selected directly from the bulk sample.
3.4. [Au(nap)(PPh3)](3)
To a solution of 1 (0.200 g, 0.687 mmol) in toluene (10 mL) was
added [AuCl(PPh3)] (0.324 g, 0.653 mmol). The mixture was stirred
at 70 ꢀC for 2 h. Removal of the solvent and recrystallisation from
ethanol gave 0.337 g (88%) of complex 3 as a yellow solid. 1H NMR
(600 MHz, CDCl3):
d
¼ 8.60e8.56 (m,1 H, nap-H8), 7.86e7.82 (m,1 H,
nap-H5), 7.79e7.75 (m, 1 H, nap-H3), 7.72e7.68 (m, 7 H, nap-H4,
o-PPh3), 7.57e7.50 (m, 9 H, m-PPh3, p-PPh3), 7.51e7.47 (m, 1 H, nap-
H2), 7.46e7.40 (m, 2 H, nap-H6, naph-H7). 13C NMR (151 MHz,
CDCl3):
d
¼ 175.20 (d, J ¼ 114.5 Hz,1 C, nap-C1),142.75 (d, J ¼ 3.2 Hz,
1 C, nap-C4a), 136.36 (1 C, nap-C3), 134.43 (1 C, nap-C8a), 134.43 (d,
J ¼ 13.7 Hz, 6 C, o-PPh3), 133.85 (d, J ¼ 0.9 Hz,1 C, nap-C8),131.22 (d,
J ¼ 2.2 Hz, 3 C, p-PPh3), 131.09 (d, J ¼ 49.3 Hz, 3 C, P-C), 129.13
(d, J ¼ 10.7 Hz, 6 C, m-PPh3), 128.26 (1 C, nap-C5), 125.49 (d,
J ¼ 6.6 Hz, 1 C, nap-C2), 125.28 (1 C, nap-C4), 124.58 (1 C, nap-C6 or
nap-C7),124.03 (1 C, nap-C6 or nap-C7). 31P NMR (243 MHz, CDCl3):
Fig. 3. Molecular structure of 3. Ellipsoids show 50% probability levels. Hydrogen
atoms have been omitted for clarity. Selected bond distances [Å]: C1-Au1 2.082(15),
P1-Au1 2.294(4). Selected angles [ꢀ]: C1-Au1-P1 174.8(4).
(p-AsPh3), 128.88 (m-AsPh3), 128.73 (m-Ph), 127.23 (p-Ph), 127.15
(o-Ph). ES-MS (m/z): 603.03 [M þ Na]þ.
d
¼ 44.22. Anal. calc. for C28H22PAu$CH2Cl2 (671.35): C, 51.88; H,
3.60. Found: C, 52.69; H, 3.42%. X-ray quality crystals were obtained
byslow diffusion of hexanes into a CH2Cl2 solution of the compound.
3.3. 1-(Trimethylstannyl)-8-iodonaphthalene (2)
3.5. [Au(8-IC10H6)(PPh3)](4)
A solution of 1,8-diiodonaphthalene (1.5 g, 3.95 mmol) in diethyl
ether (20 mL) was treated at room temperature with nBuLi (2.5 mL
1.6 M in hexane). After 15 min a solution of Me3SnCl (0.79 g,
3.96 mmol) in diethyl ether (10 mL) was added and the mixture was
left to stir overnight. The reaction mixture was hydrolysed with sat.
NH4Cl solution and the organic phase was separated. The remaining
aqueous phase was extracted 3 times with Et2O (10 mL). The
combined organic phases were dried and the solvent evaporated to
give a pale brown solid. This was recrystallised from hexanes to
afford 1.28 g (72%) of the compound as colourless needles. 1H NMR
To a solution of 3 (0.200 g, 0.479 mmol) in dichloromethane
(20 mL) was added [AuCl(PPh3)] (0.237 g, 0.479 mmol). The mixture
was stirred at room temperature for 2 h. Hexane was subsequently
added to the solution and the resulting solid was isolated by filtration
togive0.242g(71%) of complex 4 asayellowsolid.1HNMR (400 MHz,
CDCl3):
d
¼ 8.32e8.28 (m, 1 H, nap-H7), 8.07e8.03 (m, 1 H, nap-H3),
7.87e7.83 (m,1 H, nap-H5), 7.77e7.71 (m, 6 H, o-PPh3), 7.55e7.47 (m,
11 H, nap-H2, nap-H4, m-PPh3, p-PPh3), 7.12e7.08 (m, 1 H). 13C NMR
(101 MHz, CDCl3):
d
¼ 177.67 (d, J ¼ 108.9 Hz, 1 C, nap-C1), 141.50 (d,
(400 MHz, CDCl3):
d
¼ 8.29e8.25 (m,1 H, nap-H7), 7.91e7.88 (m,1 H,
J ¼ 4.4 Hz,1 C, nap-C4a),141.29 (d, J ¼ 2.3 Hz,1 C, nap-C3),138.47 (1 C,
nap-C7),136.15 (d, J ¼ 5.0 Hz,1 C, nap-C8a),134.39 (d, J ¼ 13.9 Hz, 6 C,
o-PPh3), 131.98 (d, J ¼ 49.7 Hz, 3 C, P-C), 131.06 (3 C, p-PPh3), 130.73
(1 C, nap-C5),128.97 (d, J ¼ 10.7 Hz, 6 C, m-PPh3),126.01 (1 C, nap-C4),
125.41 (d, J ¼ 4.8 Hz, 1 C, nap-C2), 125.29 (1 C, nap-C6), 109.21 (d,
nap-H2), 7.88e7.85 (m, 1 H, nap-H5), 7.79e7.75 (m, 1 H, nap-H4),
J ¼ 5.3 Hz, 1 C, nap-C8). 31P NMR (162 MHz, CDCl3):
¼ 44.03. Anal.
d
calc. for C28H21IPAu (712.31): C, 47.21; H, 2.97. Found: C, 46.51; H,
2.36%. X-ray quality crystals were obtained by slow diffusion of
hexanes into a CH2Cl2 solution of the compound.
3.6. X-ray crystallography
Diffraction data were collected at 150 K using an Oxford
Diffraction Gemini E Ultra diffractometer, equipped with an EOS
CCD area detector and a four-circle kappa goniometer. For the data
collection the Mo source emitting graphite-monochromated Mo-
Ka
radiation (
l
¼ 0.71073 Å) was used. Data integration, scaling and
empirical absorption correction was carried out using the CrysAlis
Pro program package [27]. The structures were solved using Direct
Methods or Patterson Methods and refined by Full-Matrix-Least-
Squares against F2. The non-hydrogen atoms were refined aniso-
tropically and hydrogen atoms were placed at idealised positions
and refined using the riding model. All calculations were carried
out using the program Olex2 [28]. Important crystallographic data
and refinement details are summarised in Table 1.
Fig. 4. Molecular structure of 4. Ellipsoids show 50% probability levels. Hydrogen
atoms have been omitted for clarity. Selected bond distances [Å]: Au1-C1 2.055(6),
Au1-P1 2.2878(17), I1-C9 2.111(6), Au1-I1 3.1317(7). Selected angles [ꢀ]: C1-Au1-P1
174.8(2), C1-Au1-I1 81.42(19), P1-Au1-I1 103.50(5).

N. Meyer et al. / Journal of Organometallic Chemistry 696 (2011) 1244e1247
1247
Table 1
Crystal data and refinement details of compounds 2e4.
References
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sciences, Wiley-VCH, Weinheim, 2009.
[2] H. Schmidbaur, A. Grohmann, M.E. Olmos, Organogold chemistry. in: H. Schmidbaur
(Ed.), Gold Progress in Chemistry, Biochemistry and Technology. John Wiley & Sons,
Chichester, 1999, pp. 647e746.
2
3
4
Empirical formula
Colour
C13H15ISn
yellow
416.84
orthorhombic
P212121
7.5712(4)
11.4793(5)
15.5552(7)
90.0
1351.93(11)
4
2.048
4.142
784
C28H22PAu
colourless
586.39
orthorhombic
P212121
6.5547(2)
15.4548(6)
22.0636(9)
90.0
2235.09(15)
4
C28H21IPAu
colourless
712.28
monoclinic
C2/c
25.4881(17)
14.0072(4)
18.872(2)
135.5677(4)
4716.7(7)
8
Mr, g molꢁ1
Crystal system
Space group
a, Å
[3] H. Schmidbaur, A. Grohmann, E. Olmos, A. Schier, Synthesis and uses of
organogold compounds. in: S. Patai, Z. Rappoport (Eds.), The chemistry of
organic derivatives of gold and silver. John Wiley
1999.
& Sons, Chichester,
b, Å
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c, Å
b ꢀ
,
V, Å3
Z
Dcalc., g cmꢁ3
1.743
6.666
1136
2.006
7.628
2688
m
, mmꢁ1
F(000)
Crystal size, mm3
0.02 ꢂ 0.05
0.01 ꢂ 0.08
0.05 ꢂ 0.10
ꢂ 0.17
ꢂ 0.08
ꢂ 0.21
q
range for data
collection
2.99e29.14ꢀ
3.21e58.79ꢀ
2.88e29.54ꢀ
Refl. collected
Independent refl.
Abs. corr.
4422
2895
multi-scan
1.00000/
0.65304
139
6919
4659
multi-scan
1.00000/
0.61909
271
10747
5504
multi-scan
1.00000/
0.23836
280
0.972
0.0617
0.1038
2.131/e2.291
Max/min. trans.
Parameters
GOF
R1 (all data)
wR2 (all data)
Largest diff. peak/
hole, e Åꢁ3
0.951
1.029
0.0306
0.0485
0.502/e0.587
0.0801
0.1404
5.942/e1.954
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(2006) 8188e8191.
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(2007) 3279e3282.
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tallics 28 (2009) 1666e1674.
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We thank the DFG for support of this project and also for a grant
to purchase the diffractometer.
[24] H.H. Hodgson, J.S. Whitehurst, J. Chem. Soc. (1947) 80e81.
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Appendix A. Supplementary material
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[27] CrysAlis Pro 171.33.42. Oxford Diffraction Ltd, 2009.
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Cryst. 42 (2009) 339e341.
Full crystallographic details of compounds 2-4 (CIF file format)
are available from the CCDC, 12 Union Road, Cambridge, CB2 1EZ,
UK by quoting the deposition codes CCDC 795023-795025.