Gold(I) complexes containing the cationic ylide ligand bis(methyldiphenylphosphonio)methylide

Article abstract of DOI:10.1016/S0277-5387(00)00467-8

The ylide Ph₂PCH=PPh₂Me can be selectively P-alkylated by MeI or MeO₃SCF₃ to form the bis(methyldiphenylphosphonio)methylide salts [MePPh₂CHPPh₂Me]A (A=I (1), CF₃SO₃ (2)). The ylidic carbon shows a weak nucleophilicity and does not give typical reactions with common organic electrophiles, including Wittig type reactions, but it is able to displace tetrahydrothiophene in [AuX(tht)] to give the corresponding C-coordinated gold(I) compounds [Au{CH(PPh₂Me)₂}X]CF₃SO₃ (X=Cl (3), C₆F₅ (4)). The crystal structure of (4) displays a linear coordination for the gold atom, single P-C bond lengths and a PCP angle of 119.1(3)°for the ligand. (C) 2000 Elsevier Science Ltd.

Full text of DOI:10.1016/S0277-5387(00)00467-8

www.elsevier.nl/locate/poly
Polyhedron 19 (2000) 1837–1841
Gold(I) complexes containing the cationic ylide ligand
bis(methyldiphenylphosphonio)methylide
Inocencio Romeo, Manuel Bardaj´ı, M. Concepcio´n Gimeno, Mariano Laguna *
Departamento de Qu´ımica Inorga´nica, Instituto de Ciencia de Materiales de Arago´n, Uni6ersidad de Zaragoza-CSIC, 50009 Zaragoza, Spain
Received 9 March 2000; accepted 15 June 2000
Abstract
The ylide Ph2PCHꢀPPh2Me can be selectively P-alkylated by MeI or MeO3SCF3 to form the bis(methyldiphenylphospho-
nio)methylide salts [MePPh2CHPPh2Me]A (AꢀI (1), CF3SO3 (2)). The ylidic carbon shows a weak nucleophilicity and does not
give typical reactions with common organic electrophiles, including Wittig type reactions, but it is able to displace tetrahydroth-
iophene in [AuX(tht)] to give the corresponding C-coordinated gold(I) compounds [Au{CH(PPh2Me)2}X]CF3SO3 (XꢀCl (3), C6F5
(4)). The crystal structure of (4) displays a linear coordination for the gold atom, single PꢁC bond lengths and a PCP angle of
119.1(3)° for the ligand. © 2000 Elsevier Science Ltd. All rights reserved.
Keywords: Gold(I) complexes; Cationic ylide ligand; Bis(methyldiphenylphosphonio)methylide salts; P-alkylation
1. Introduction
X-ray diffraction studies of the pentafluorophenyl
derivative were carried out to fully characterize their
geometry.
Carbodiphosphorane chemistry has attracted much
attention not only because of the synthesis and geome-
try of the PꢀCꢀP fragment [1] but also for the synthesis
of metallic complexes. Therefore several mononuclear
copper, gold, silver [2,3], iridium [4], platinum [5,6],
rhenium [7,8], tungsten [6,8,9], manganese, chromium,
iron and nickel [8] or dinuclear gold [10] and iron [11]
derivatives have been prepared.
On the contrary the mesomeric phosphonium ylides
R3PCHPR3+ have often been overlooked because of
their intermediate position on the carbodiphosphoranes
and not Cylidic-bonded metallic complexes have been
described so far. Some complexes containing the unit
ꢁCH2PR2CHPR2CH2ꢁ have been reported with the lig-
and acting as quelate through the CH2 groups
[10,12,13].
2. Experimental
All the reactions were carried out under a dry nitro-
gen atmosphere at room temperature (r.t.). IR spectra
were recorded on a Perkin–Elmer 883 spectrophotome-
ter, over the range 4000–200 cm−1, by using Nujol
1
mulls between polyethylene sheets. H, 19F and 31P{1H}
NMR spectra were recorded on a Varian UNITY 300
or Bruker ARX-300 apparatus in CDCl3 solutions;
chemical shifts are quoted relative to SiMe4 (external,
1H), CFCl3 (external, 19F) and 85% H3PO4 (external,
31P). C, H, N and S analyses were performed with a
Perkin–Elmer 2400 microanalyzer. Mass spectra were
recorded on a VG Autospec using LSIMS technique
(with cesium gun) and 3-nitrobenzyl alcohol as matrix.
In this paper, the synthesis of the phosphoranium
salts [MePPh2CHPPh2Me]A (AꢀI, CF3SO3) and their
first metallic complexes [Au[CH(PPh2Me)2)X]CF3SO3
(XꢀCl, C6F5) are reported, which in spite of the weak
nucleophilic character of the ylidic carbon are stable.
2.1. Preparation of the ligands
2.1.1. [MePh2PCHPPh2Me]I (1)
* Corresponding author. Tel.: +34-976-761-181; fax: +34-976-
761-187.
To
a
diethyl ether suspension (10 ml) of
E-mail address: mlaguna@posta.unizar.es (M. Laguna).
[Ph2PCH2PPh2Me]I [14] (0.54 g, 1 mmol) was added an
0277-5387/00/$ - see front matter © 2000 Elsevier Science Ltd. All rights reserved.
PII: S0277-5387(00)00467-8

1838
I. Romeo et al. / Polyhedron 19 (2000) 1837–1841
2.1.2. [MePh2PCHPPh2Me]CF3SO3 (2)
excess of sodium hydride (1.2 g of a 60% paraffin
suspension, 3 mmol). After stirring for 5 h, the excess
of NaH and the formed NaI are filtered off, obtaining
a yellow solution of the ylide. The addition of MeI
(0.142 g, 1 mmol) immediately afforded a white solid
which was filtered off and washed with diethyl ether
As stated for (1) but adding drop by drop MeO3SCF3
instead of MeI till all the white solid has precipitated.
Yield of 2: 65%. 1H NMR: 8 7.8–7.2 (m, 20H, Ph), 2.04
2
2
(d, 6H, JHP=12.3, MeꢁP), 1.30 (t, 1H, JHP=5.6 Hz,
PꢁCHꢁP); 31P{1H} NMR:
l
16.5. Anal. Calc.
1
C28H27F3O3P2S: C, 59.8; H, 4.85;S, 5.7. Found: C, 60.0;
H, 4.65; S, 5.55.
(3×5 ml). Yield of 1: 55%. H NMR: l 7.8–7.2 (m,
2
20H, Ph), 2.13 (d, 6H, JHP=12.0, MeꢁP), 1.39 (t, 1H,
2JHP=4.6 Hz, PꢁCHꢁP); 31P{1H} NMR: l 16.5. Anal.
Calc. C27H27IP2: C, 60.0; H, 5.05. Found: C, 59.85; H,
4.9.
2.2. Preparation of the gold(I) complexes
2.2.1. [Au{CH(PPh2Me)2}X]CF3SO3; XꢀCl (3), C6F5
(4)
Table 1
To a dichloromethane solution (20 ml) of 2 (0.11 g,
0.2 mmol) was added 0.2 mmol of [AuX(tht)] (XꢀCl
0.064 g, C6F5 0.09 9) [15,16]. The mixture was stirred
for 90 min, then concentrated to ca. 5 ml and the
addition of diethyl ether (15 ml) afforded complexes
3–4 as white solids, which were washed with diethyl
Details of data collection and structure refinement for complex 4
Compound
4
Chemical formula
Crystal habit
Crystal size (mm)
Crystal system
Space group
C34H27AuF8O3P2S
colourless needle
0.65×0.20×0.10
triclinic
1
ether (3×5 ml). Yield of (3): 88%. H NMR: 6 7.8–7.2
(
P1
2
,
a (A)
9.641(2)
11.538(2)
16.696(3)
77.91(3)
77.69(3)
81.05(3)
1762.3(6)
2
(m, 20H, Ph), 4.66 (t, 1H, JHP=16.8, PꢁCHꢁP), 2.14
2
(d, 6H, JHP=12.4 Hz, MeꢁP); 31P{1H} NMR: l 22.1.
,
b (A)
,
c (A)
Anal. Calc. C28H27CIF3O3P2SAu: C, 42.3; H, 3.4; S,
h (°)
i (°)
4.05. Found: C, 42.35; H, 3.75; S, 4.0. Yield of (4):
1
87%. H NMR: l 7.8–7.2 (m, 20H, Ph), 4.28 (t, 1H,
k (°)
3
,
U (A )
Z
2JHP=16.7, PꢁCHꢁP), 2.22 (d, 6H, 2JHP=11.9 Hz,
MeꢁP); 19F NMR: l −78.0 (s, 3F, CF3), −117.0 (m,
2Fo), −161.3 (t, 1Fp), −164.8 (m, 2Fm); 31P{1H}
NMR: l 22.7. Anal. Calc. C34H27F8O3P2SAu: C, 44.1;
H, 2.95; S, 3.45. Found: C, 44.35; H, 3.0; S, 3.3.
Dcalc (Mg m−3
M
)
1.746
926.52
904
F(000)
T(°C)
25
2qmax (°)
50
v (Mo Ka) (mm−1
)
4.400
0.649–0.970
7767
2.3. X-ray crystallography
Transmission
Number of reflections measured
Number of unique reflections
The crystal was mounted in inert oil on a glass fibre
and transferred to the cold gas stream of a Siemens P4
diffractometer equipped with an Oxford low tempera-
ture attachment. Data were collected using monochro-
mated Mo Ka radiation (u=0.71073). Scan type
theta-2theta. Absorption correction was applied based
on C-scans. The structure was solved by the heavy-
atom method, and refined on F2 using the program
SHELXL-93 [17]. Non hydrogen atoms were refined an-
isotropically. Hydrogen atoms were included using a
riding model. Further details are given in Table 1.
6179
Rint
R
0.023
0.040
0.098
442
a
(F, F\4|(F))
wR (F2, all reflections)
Number of parameters
Number of restraints
b
0
c
S
0.959
1.81
−3
,
Max. Dz (eA
)
a R(F)=ꢀ ꢁꢁFoꢁ−ꢁFcꢁꢁ/ꢀꢁFo.
b wR
(F2)=[ꢀ{w(Fo2−F2c)2}/ꢀ{w(F2o)2}]0.5
;
w
−1=|2(F2o)+
(aP)2+bP, where P=[Fo2+2F2c]/3 and a and b are constants adjusted
by the program.
c S=[ꢀ{w(Fo2−Fc2)2}/(n−p)]0.5, where n is the number of data and
p the number of parameters.
3. Results and discussion
3.1. Ligand synthesis
The phosphoranium salts were prepared following
the Scheme 1. First it was carried out the reaction of
bis(diphenylphosphino)methane (dppm) with MeI to
give the monomethylated product. This compound was
deprotonated in the presence of an excess of sodium
hydride to afford a yellow solution of the mono-ylide
Scheme 1.

I. Romeo et al. / Polyhedron 19 (2000) 1837–1841
1839
position [21,22]. That is why to our knowledge there is
no metallic complexes containing the ligand
R3PꢀCHꢁPR3+. On the contrary and as stated before
for the corresponding carbodiphosphorane ligands
R3PꢀCꢀPR3, of which the ylidic carbon is a stronger
nucleophile, coordination compounds are well known,
although most of them are only mononuclear C-coordi-
nated complexes. Reactions of ylides with electrophiles
such as benzaldehyde, acetyl chloride, benzoyl chloride,
benzyl chloride and carbon disulfide gave no reaction.
Scheme 2.
3.2. Gold(I) complexes synthesis
We have previously reported several gold(I) com-
plexes with C-coordination to ylides coming from the
dppm [23]. For instance we have prepared the corre-
sponding C-bonded gold complexes by coordination to
[Au(C6F5)SPPh2CH(PPh2Me)] [24] or to [Au(C6F5)-
PPh2CH(PPh2Me)] [25] which are very close to ligands
1–2 (equals by substituting the P- or S-coordinated
gold(I) fragment for methyl) and they also are very
stable ylides. Therefore we carried out the same reac-
tions between the phosphoranium salts 1–2 and gold(I)
complexes (see Scheme 2). The reactions evolve with
displacement of tetrahydrothiophene (tht) to afford
complexes 3–4 as white solids air and moisture stable.
Their IR spectra show absorptions at 335 cm−1 (3)
due to w(AuꢁCl) [26], 955 and 797 cm−1 from the
pentafluorophenyl groups (4) [27], and 1265, 1222, 638
(3), 1250,1224 and 638 cm−1 (4) from triflate anions.
Fig. 1. Structure of the cation of complex 4 in the crystal with the
numbering scheme. Radii are arbitrary; hydrogen atoms except at C1
are omitted for clarity.
Ph2PCHꢀPPh2Me, air and moisture sensitive, which
had been already prepared by a transylidation reaction
[14]. Ylides can be easily alkylated although a mixture
of the C-alkylated and the P-alkylated derivatives are
usually obtained [18,19]. The alkylation of our ylide
affords purely the P-alkylated derivative, by using MeI
or methyl triflate as reagents, which is probably due to
the stability of the bisphosphonium fragment. Even by
adding 100% excess of MeI the P-alkylated derivative
was the only compound obtained. However the addi-
tion of methyltriflate to the ylide in a 2:1 molar ratio
leads mainly to a mixture of the P-alkylated derivative
(2) and the phosphonium salt PPh2Me2+ coming from
the cleavage of (2).
1
The H NMR spectra show an almost unchanged dou-
blet around 2.1 ppm for the methyl group and a triplet
at 4.66 ppm for (3) and 4.28 ppm for (4) due to the
methylide bridge, clearly low-field shifted from (2) (Dl
is 3.36 ppm for (3) and 2.98 ppm for (4)). The 31P{1H}
NMR spectra show a singlet around 22 ppm and again
about 6 ppm low-field shifted after gold coordination.
The 19F NMR spectrum of (4) shows the pattern of a
pentafluorophenyl group besides of the triflate counter-
ion. The LSIMS mass spectra show the base peak at
m/z=413 due to the bis(phosphonium)methylide lig-
and and at 645 (20%, for (3)) and at 777 (65%, for (4))
corresponding to [MꢁCF3SO3]+.
These derivatives are air- and moisture-stable white
solids at room temperature. The IR spectrum of (2)
shows absorptions at 1266, 1222 and 638 cm−1 from
1
the triflate anion [20]. The H NMR spectra of (1) and
(2) are very similar showing a doublet around 2 ppm
for the methyl group and a higher field triplet (about
1.35 ppm) for the methylide bridge. In the 31P{1H}
NMR spectra it can be observed, in both cases, a
singlet at 16.5 ppm as expected for two equivalent
phosphorus atoms.
These phosphoranium salts are very stable, which has
been explained by the very weak nucleophilicity of the
ylidic carbon which prevents nucleophilic substitution
or addition reactions. In fact, typical Wittig reactions
for these ylides are only known if hydrogen is replaced
by fluor in the carbanion, that has been explained
because fluor destabilizes negative charges in an alfa
3.3. Crystal structure of
[Au{CH(PPh2Me)2}(C6F5)]CF3SO3
The structure of the cation is shown in Fig. 1, with
selected bond lengths and angles in Table 2. It consists
of a gold(I) center bonded to two kinds of carbon
atoms, one coming from a pentafluorophenyl group
and the other from an ylidic ligand. Both distances
AuꢁC are very different; AuIꢁC6F5 is 2.029(6), which is
of the same order as that found in related complexes
,
such as [Au(C6F5)2{(PPh2)2CH}Au(C6F5)] (2.048(8) A)

1840
I. Romeo et al. / Polyhedron 19 (2000) 1837–1841
Table 2
AuꢁC6F5 unit compared to a methyl group. The
PꢁCꢁAu angles, 109.1(3) and 105.7(3)°, are close to a
tetrahedral disposition.
,
Selected bond lengths (A) and angles (°) for complex 4
Au(1)ꢁC(2)
Au(1)ꢁC(1)
C(1)ꢁP(2)
C(1)ꢁP(1)
P(1)ꢁC(8)
2.029(6)
2.112(6)
1.781(6)
1.792(6)
1.788(7)
P(1)ꢁC(21)
P(1)ꢁC(11)
P(2)ꢁC(9)
P(2)ꢁC(41)
P(2)ꢁC(31)
1.795(6)
1.799(7)
1.794(7)
1.794(7)
1.797(7)
4. Supplementary material
C(2)ꢁAu(1)ꢁC(1)
P(2)ꢁC(1)ꢁP(1)
P(2)ꢁC(1)ꢁAu(1)
P(1)ꢁC(1)ꢁAu(1)
C(8)ꢁP(1)ꢁC(1)
C(8)ꢁP(1)ꢁC(21)
C(1)ꢁP(1)ꢁC(21)
C(8)ꢁP(1)ꢁC(11)
C(1)ꢁP(1)ꢁC(11)
175.9(2)
C(1)ꢁP(2)ꢁC(31)
C(9)ꢁP(2)ꢁC(31)
C(41)ꢁP(2)ꢁC(31)
C(16)ꢁC(11)ꢁP(1)
C(12)ꢁC(11)ꢁP(1)
C(22)ꢁC(21)ꢁP(1)
C(26)ꢁC(21)ꢁP(1)
C(36)ꢁC(31)ꢁP(2)
C(32)ꢁC(31)ꢁP(2)
C(42)ꢁC(41)ꢁP(2)
C(46)ꢁC(41)ꢁP(2)
C(3)ꢁC(2)ꢁAu(1)
C(7)ꢁC(2)ꢁAu(1)
106.6(3)
Crystallographic data for complex 4 (excluding struc-
ture factors) have been deposited with the Cambridge
Crystallographic Data Centre, CCDC No. 141436.
Copies can be obtained free of charge from The Direc-
tor, CCDC, 12 Union Road, Cambridge, CB2 1EZ,
UK (Fax: +44-1123-336033; e-mail: deposit @ccdc.
cam.ac.uk or www: http://www.ccdc.cam.ac.uk).
119.1(3)
109.1(3)
105.7(3)
111.4(3)
108.5(3)
112.6(3)
108.9(4)
108.4(3)
106.6(3)
110.4(3)
121.2(5)
119.9(7)
123.2(5)
118.1(5)
119.7(5)
121.3(6)
120.7(5)
119.9(5)
125.9(5)
120.3(5)
C(21)ꢁP(1)ꢁC(11) 107.0(3)
C(1)ꢁP(2)ꢁC(9)
C(1)ꢁP(2)ꢁC(41)
C(9)ꢁP(2)ꢁC(41)
112.3(3)
111.8(3)
109.0(4)
Acknowledgements
We thank the Direccio´n General de Ensen˜anza Supe-
rior (Project PB98-0542) for financial support.
References
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[(F5C6)AuCH(PPh2AuPPh2)2CHAu(C6F5)]
,
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,
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,
,
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[FeCl4] (1.822(4) and 1.816(4) A) [33].
The PꢁCꢁP angle is 119.1(3)°, slightly smaller than
that found in MePPh2PꢀCꢀPPh2Me (121.8°) or
[Au(C6F5)PPh2CH(PPh2Me)] (126.0(4)°) due to hy-
bridization state, also smaller than that found in
[PPh3CH2PPh3][FeC14] (123.4(2)°), probably because of
electrostatic repulsion in the latter [33] but bigger than
that in [(F5C6)AuPPh2CH(PPh2Me)AuC6F5] 114.9(6)°
presumably because the major steric repulsion of an
,
,
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