Chalcogeno[bis(phosphaalkenyl)] germanium and tin compounds

Article abstract of DOI:10.1021/ic300810q

The first diphosphaalkenylstannylene stabilized through complexation with a carbene NHC-Sn[C(Cl)=PMes*]₂1 (Mes* = 2,4,6-tri-tert-butylphenyl; NHC =:C{N(iPr)C(Me)}₂) was isolated and fully characterized including single crystal X-ray diffraction analysis. Its reaction with elemental sulfur rapidly gives the cyclic Sn₂S ₂ (dithiadistannetanne) derivative 3, presumably formed by dimerization of a stannathione intermediate. By contrast, its germanium analogue NHC-Ge[C(Cl)=PMes*]₂7 leads to the corresponding monomeric germathione 4 and germaselenone 5. The germaselenone was more stable than the germathione and could be structurally characterized. An unusual thermal cyclization reaction of the last one occurs with an excess of selenium to give the Ge₂Se₃ (triselenadigermolane) ring derivative 6.

Full text of DOI:10.1021/ic300810q

Article
pubs.acs.org/IC
Chalcogeno[bis(phosphaalkenyl)] Germanium and Tin Compounds
Tibor-Gabor Kocsor,†,‡ Dimitri Matioszek,† Gabriela Nemes,*,‡ Annie Castel,*,† Jean Escudie,†
̧
́
Petronela M. Petrar,‡ Nathalie Saffon,§ and Ionel Haiduc‡
†Universite
́
de Toulouse, UPS, CNRS, LHFA, UMR 5069, 118 Route de Narbonne, F-31062 Toulouse cedex 09, France
̆
Facultatea de Chimie si Inginerie Chimica, Universitatea Babes-Bolyai, Str. M. Kogalniceanu,
‡Departamentul de Chimie Anorganica,
̆
̧
̆
̧
Nr: 1, RO-400084, Cluj-Napoca, Romania
§Universite
France
́
de Toulouse, UPS, Service Commun Rayons X, ICT-FR2599, 118 Route de Narbonne, F-31062 Toulouse cedex 09,
S
* Supporting Information
ABSTRACT: The first diphosphaalkenylstannylene stabilized
through complexation with a carbene NHC−Sn[C(Cl)
PMes*]2 1 (Mes* = 2,4,6-tri-tert-butylphenyl; NHC =
:C{N(iPr)C(Me)}2) was isolated and fully characterized
including single crystal X-ray diffraction analysis. Its reaction
with elemental sulfur rapidly gives the cyclic Sn2S2 (dithiadistannetanne) derivative 3, presumably formed by dimerization of a
stannathione intermediate. By contrast, its germanium analogue NHC−Ge[C(Cl)PMes*]2 7 leads to the corresponding
monomeric germathione 4 and germaselenone 5. The germaselenone was more stable than the germathione and could be
structurally characterized. An unusual thermal cyclization reaction of the last one occurs with an excess of selenium to give the
Ge2Se3 (triselenadigermolane) ring derivative 6.
germanium and tin compounds with double bond to
chalcogens have been isolated using kinetic or thermodynamic
stabilization,15 the examples of ME stabilized by NHC are
rare. To the best of our knowledge, only few derivatives of the
type NHC−SiR2E (E = O, S, Se, Te) and NHC−GeR2O,
stable at room temperature, were described.16
We have recently reported the synthesis of the bis-
(phosphaalkenyl)germylene NHC−Ge[C(Cl)PMes*]2
(Mes* = 2,4,6-tri-tert-butylphenyl; NHC = :C{N(iPr)C-
(Me)}217), the first representative of a new class of germylenes
using the phosphaalkenyl −PC⟨ unit as ligands and the
stabilizing coordination properties of the NHC; such a
derivative with a CPMes* moiety is particularly interesting
since due to multiple possibilities of reaction or coordination
(lone pair on phosphorus, divalent germanium atom and PC
double bonds) it can potentially present an unexpected and rich
reactivity which was proved by its reaction with transition-metal
complexes.18
INTRODUCTION
■
Low-valent group 14 compounds have attracted much attention
in fundamental chemistry because of their particular structures
and high reactivities.1 Since the discovery of the Arduengo-type
carbene in 1991,2 the rapid development of the chemistry of N-
heterocyclic carbenes (NHC), their use in transition metal
catalysis3 and more recently as organocatalysts4 have increased
interest in their higher congeners of group 14 elements.5
Among the stabilization strategies of germylenes or
stannylenes, the intermolecular coordination has aroused a
great interest in the last decades particularly with the use of
NHC as stabilizing coligand.6 In the germanium series, after the
isolation of the first carbene-germanium(II) adducts, (NHC−
7
GeI2 and a NHC−heterocyclic germylene8), a large variety of
transient germanium(II) species has been isolated by employ-
ing electron-donating NHC.9 In contrast, there are few
examples of tin analogues. Both carbene−tin complexes
NHC−SnCl2 and NHC−SnAr2 (Ar = 2,4,6-iPr3C6H2) were
prepared and structurally characterized in the same year.10
Later, a zwitterionic carbene-stannylene adduct was obtained by
cleavage of a dibenzotetraazafulvalene by a diaza-stannylene.11
To the best of our knowledge, there are only two examples of
unstable entities stabilized by coordination to NHC: the tin(II)
dihydride in the form of the carbene-tungsten bis-adduct
These results prompted us to investigate the synthesis of its
tin analogue NHC−Sn[C(Cl)PMes*]2 and to explore the
reactivity of these new germylene and stannylene with
elemental chalcogens; all of which is presented herein.
RESULTS AND DISCUSSION
■
12
Synthesis and Structure of the Bis(phosphaalkenyl)-
tin(II) Compound 1. The addition of NHC−SnCl2 to a
freshly prepared solution of Mes*PC(Li)Cl in THF at low
temperature afforded the novel stannylene NHC−Sn[C(Cl)
NHC−SnH2W(CO)5 and the hypermetallyl stannylenes
NHC−Sn[M(SiMe3)3]2, (M = Si, Ge, Sn)].13 One of the
most characteristic feature of group 14 divalent derivatives is
their high potential as building blocks in organometallic
chemistry; for example, their oxidation by elemental chalcogens
constitutes an usual and clean route to double bonded species
ME (M = Si, Ge, Sn; E = S, Se, Te).14 Although numerous
Received: April 20, 2012
Published: June 29, 2012
© 2012 American Chemical Society
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Article
PMes*]2 1, which was isolated as a light brown air-sensitive
powder in a good yield. In the 31P NMR spectrum, only one
signal appeared at 277.4 ppm indicating the formation of one
isomer. As previously observed in the case of the germanium
analogue,18 the free disubstituted stannylene 2, obtained from
the dichlorostannylene SnCl2, was not stable and decomposed
after some hours in solution. However, it was unambiguously
characterized by adding NHC to a freshly prepared solution in
THF by formation of its carbene adduct 1 (Scheme 1).
Table 1. Selected Bond Lengths (Å) and Angles (deg) for
Compounds 1, 3, 5, and 6
1
3
Sn1−C1
Sn1−C2
Sn1−Ccarbene
Sn1−S1
P1−C1
P2−C2
P1−S2
P2−S3
2.230(2)
2.239(2)
2.316(2)
2.1384(15)
2.1428(16)
2.4134(4)
1.6497(17)
1.6512(17)
1.9187(6)
1.9350(6)
120.49(6)
110.35(5)
111.02(4)
6
1.674(2)
1.672(2)
Scheme 1. Synthesis of Compounds 1 and 2
C1−Sn1−C2
C1−Sn1−S1
C2−Sn1−S1
98.24(8)
5
Ge1−C1
Ge1−C2
Ge2−C3
Ge2−C4
1.986(5)
1.972(5)
1.945(4)
1.956(4)
1.945(4)
1.953(4)
Ge1−Ccarbene
Ge1−Se1
Ge1−Se2
Ge2−Se1
Ge2−Se3
Se2−Se3
2.048(5)
2.2426(7)
2.3482(6)
2.3584(7)
2.3497(7)
2.3529(6)
2.3508(7)
1.666(4)
P1−C1
P2−C2
1.673(5)
1.660(5)
The stannylene 1 is stable up to 60 °C in tetrahydrofuran or
in toluene but a rapid decomposition is observed in
dichloromethane or in chloroform. It was fully characterized
by NMR spectroscopy and single-crystal X-ray structure
analysis. The 1H and 13C NMR spectra show typical resonances
expected for the carbenic moiety10a and for the phosphaalkenyl
group.18 The 119Sn NMR spectrum displays a singlet at −130.8
ppm upfield-shifted compared to that of NHC−SnCl2 (−59.4
ppm)10a but in the range of three-coordinate tin(II)
derivatives.13 The X-ray structure analysis shows an E/E
configuration around the PC double bond and a
tricoordinate tin center which exhibits a flattened pyramidal
geometry (Figure 1, Table 1). The Sn−Ccarbene distance
(2.316(2) Å) suggests a similar strength as for the donor/
acceptor interaction in NHC−SnCl2 (2.290(5) Å)10a but
1.655(4)
P3−C3
P4−C4
C1−Ge1−C2
C3−Ge2−C4
Se1−Ge1−Se2
Se1−Ge2−Se3
1.668(4)
1.657(4)
109.0(2)
110.52(15)
111.70(15)
108.87(2)
108.61(2)
Sn−Ccarbene distance is longer than the Sn1−C1 and Sn1−C2
bond lengths corresponding to simple covalent bonds.
Oxidation Reactions with Sulfur and Selenium. The
reactivity of the stannylene 1 was studied toward chalcogens
and compared to that of the corresponding germylene NHC−
Ge[C(Cl)PMes*]2 7 previously prepared.18 Addition of an
excess of sulfur to the stannylene 1 led exclusively to the
dithiadistannetanne 3 with elimination of the carbene. The
four-membered ring is probably obtained by dimerization of the
transient stannathione SSn[C(Cl)PMes*]2 and sulfur
oxidative addition to the phosphorus atoms.
weaker than the one in the recently reported coordinative
9h
derivative IPr−SnH2W(CO)5
(2.230(6) Å) (IPr =
(HCNAr′)2C:, Ar′ = 2,6-iPr2C6H3). We should note that the
The 31P NMR spectrum of 3 displayed only one signal at
117/119
189.2 ppm (2JP−
= 258.8/270.6 Hz) showing that the
Sn
four phosphorus atoms are magnetically equivalent. The low
field chemical shift is characteristic of a λ5σ3 phosphorus atom;
similar chemical shifts have been reported for derivatives with a
Mes*P(S)CGe moiety.19 The H and 13C NMR data
1
clearly indicate the absence of the carbenic moiety and the
perfect symmetry of the molecule. In addition, a triplet of
triplet at −95.3 ppm with two coupling constants (2JSn−P
=
270.7 Hz and 4JSn−P = 7.5 Hz) was observed in the 119Sn NMR
spectrum in agreement with the formation of such metal-
loheterocycles.
The structure of 3 was unambiguously determined by single
crystal X-ray diffraction analysis (Figure 2). Compound 3 has a
dinuclear structure with bridging sulfur atoms in which the tin
atom exhibits a distorded tetrahedral geometry. The four-
membered ring is planar by symmetry and has an inversion
Figure 1. Molecular structure of compound 1 in the solid state (50%
probability level for the thermal ellipsoids). For clarity, hydrogen
atoms are omitted and methyl/isopropyl/t-Bu groups are simplified.
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Table 2. Crystallographic Data for Compounds 1, 3, 5, and 6
1
3
5
6
formula
mol wt
C49H78Cl2N2P2Sn
946.66
C76H116Cl4P4S6Sn2.C7H8
1817.24
C49H78Cl2GeN2P2Se.1.5(C7H8)
C76H116Cl4Ge2P4Se3.2(C5H12)
1117.73
193(2)
0.71073
triclinic
1821.72
193(2)
0.71073
triclinic
temp. (K)
λ(Mo Kα) (Å)
cryst syst
space group
a (Å)
193(2)
193(2)
0.71073
0.71073
triclinic
triclinic
P1
̅
P1
̅
P1
̅
9.9799(5)
P1
̅
12.8737(2)
15.0045(3)
16.0067(3)
66.4910(10)
69.4920(10)
73.1300(10)
2614.52(8)
2
12.4775(4)
13.8395(4)
14.3456(4)
94.8930(10)
97.332(2)
11.6532(17)
b (Å)
22.0637(12)
27.7366(15)
87.142(3)
19.582(4)
c (Å)
21.979(4)
α (deg)
β (deg)
γ (deg)
V (Å3)
78.469(7)
87.901(2)
89.317(6)
110.1260(10)
2284.64(12)
1
82.048(2)
74.700(6)
6038.4(6)
4735.6(14)
2
Z
4
dcalcd (g/cm3)
1.202
1.321
1.229
1.278
μ (mm−1
)
0.684
0.910
1.288
2.007
F(000)
1000
946
2364
1900
cryst size (mm)
θ range (deg.)
index range h k l
0.20 × 0.20 × 0.10
5.10 - 28.28
−17 ≤ h ≤ 17
−19 ≤ k ≤ 19
−21 ≤ l ≤ 21
35801/12828
R(int) = 0.0441
98.9
0.50 × 0.38 × 0.36
5.10 - 28.28
−16 ≤ h ≤ 16
−18 ≤ k ≤ 18
−19 ≤ l ≤ 19
36008/11261
R(int) = 0.0169
99.2
0.38 × 0.06 × 0.04
5.11 - 24.71
−11 ≤ h ≤ 11
−25 ≤ k ≤ 25
−32 ≤ l ≤ 32
100435/20176
R(int) = 0.1033
98.0
0.10 × 0.08 × 0.04
5.11 - 24.71
−13 ≤ h ≤ 13
−23 ≤ k ≤ 23
−25 ≤ l ≤ 25
70423/15831
R(int) = 0.0616
98.0
no of reflns collected/unique
completeness to θ(%)
data/restraints/params
goodness-of-fit
12828/0/529
1.007
11261/141/546
1.049
20176/783/1456
1.046
15831/324/1034
1.013
R1, wR2 (I > 2(σ)I)
R1, wR2 (all data)
largest diff. peak, hole (eÅ−3
0.0360, 0.0813
0.0534, 0.0899
0.651, −0.322
0.0240, 0.0610
0.0268, 0.0636
0.888, −0.431
0.0597, 0.1084
0.1285, 0.1282
0.576, −0.488
0.0391, 0.0825
0.0738, 0.0958
0.682, −0.360
)
Scheme 2. Synthesis of Dithiadistannetanne 3
center at the midpoint of the ring. The phosphaalkenyl
substituents are attached to each tin atom with one above and
the other one below the ring and the chlorine and sulfur atoms
are situated in a trans position relatively to the PC double
bond. The Sn1−S1 and Sn1−S1′ bond lengths (2.4134(4) and
2.4196(4) Å) are comparable to those previously observed for
sulfido-bridged dimers (average 2.41−2.47 Å).15c,20 By contrast,
no reaction occurs at room temperature between 1 and
selenium; heating the reaction mixture at 40 °C involved a slow
decomposition of stannylene.
In the case of the Ge(II) compound 7, rapid reactions take
place with both sulfur and selenium (Scheme 3). The 31P NMR
spectra show the presence of a sole signal at 289.9 ppm for 4
and 291.3 ppm for 5, slightly downfield shifted in comparison
with that of the starting derivative NHC−Ge[C(Cl)PMes*]2
indicating that no oxidative reaction occurs at the phosphorus
atom. This difference of behavior between the tin and
germanium compounds could be explained by the larger steric
hindrance in the case of the germanium derivatives which
prevents both dimerization reactions and oxidation at the
phosphorus atom.
Figure 2. Molecular structure of compound 3 (50% probability level
for the thermal ellipsoids). For clarity, hydrogen atoms and
cocrystallized solvent (toluene) are omitted and t-Bu groups are
simplified.
1
The germathione 4 was characterized by H and 31P NMR
spectroscopy but decomposed to unidentified products after
some hours in solution; contrary to its tin analogue, the head-
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germylene (2.087(2) Å),18 whereas the Ge−C(P) bonds are
slightly shorter (1.972(5) and 1.986(5) Å versus 2.011(2) and
2.014(2) Å).18
Scheme 3. Synthesis of Chalcogeno (S, Se) Germanium
Compounds
Heating the germaselenone NHC−Ge(Se)[C(Cl)
PMes*]2 5 at 80 °C in the presence of selenium led to the
new five-membered ring derivative 6 containing three selenium
and two germanium atoms with elimination of the NHC. This
compound is probably formed by an initial head-to-tail
dimerization followed by selenium insertion. So far, only two
similar heterocycles (tetradentate [Ge2Se7]−4 anions) have
been reported.23 Compound 6 was fully characterized and the
solid state structure has been determined by single crystal X-ray
diffraction studies (Figure 4). As observed for tetraselenager-
to-tail dimer sometimes formed from GeS compounds,21 was
never obtained. By contrast, the germaselenone 5 was stable
and could be isolated and characterized by NMR spectroscopy
and by X-ray diffraction studies (Figure 3). Some germasele-
Figure 4. Molecular structure of compound 6 in the solid state (50%
probability level for the thermal ellipsoids). For clarity, hydrogen
atoms and cocrystallized solvent (pentane) are omitted and t-Bu
groups are simplified.
Figure 3. Molecular structure of compound 5 in the solid state (50%
probability level for the thermal ellipsoids). For clarity, hydrogen
atoms and cocrystallized solvent (toluene) are omitted and methyl/
isopropyl/t-Bu groups are simplified. The asymmetric unit contains
two independent molecules; only one is shown.
molanes,24 compound 6 presents a distorted half-chair
conformation in which the two germanium and two selenium
atoms (Se1 and Se2) almost lie in the same plane with the third
selenium (Se3) at 1.365 Å out of the mean plane. The Ge−Se
distances (average 2.35 Å) are slightly shorter than in the
nones stabilized owing to extremely bulky groups on the
germanium atom or by intramolecular complexation have
previously been reported.15a,b,f,22 In our case, as the steric
crowding close to the germanium atom is relatively small, the
stabilization is probably due to the complexation by the
carbene. The presence of the carbene is proved in the 13C
NMR spectrum of 5 by a signal at the expected chemical shift
for the carbenic carbon atom (149.94 ppm) coupled with the
phosphorus atom (3JC−P = 10.0 Hz). Although 4 could not be
[Ge2Se7]−4 anions (2.41 Å)21 and in a tetraselenagermolane
a
(2.42 Å).23a,24 Let us note that even with an excess of selenium
and under heating, the formation of compounds with a PSe
unit has not been observed, contrary to the case of the tin
derivative 1 which reacts with sulfur to form PS double
bonded derivative. The 77Se NMR spectrum reveals the
presence of two singlets at −160.4 and −500.0 ppm.
1
isolated due to its low stability, the fact that its H NMR
spectrum is very similar to that of 5 unambiguously proves its
germathione structure. The 77Se NMR spectrum of 5 displays a
singlet at −173.7 ppm that is in the range of the values
observed for germaselenones stabilized by intramolecular
complexation (−28.7 to −348 ppm).15f,22b Figure 3 shows its
molecular structure. The asymmetric unit contains two
chemically similar but crystallographically different molecules
of 5 in which the germanium atom is four-coordinated in a
tetrahedral environment. The Ge−Se distance of 2.2426(7) Å is
in good agreement with the values reported for GeSe bonds
(2.199(1) and 2.223(9) Å).15f,22b The Ge−Ccarbene bond
(2.048(5) Å) is about the same as that of the starting
CONCLUSION
■
In summary, the first bis(phosphaalkenyl)tin(II) compound
stabilized by intramolecular coordination of N-heterocyclic
carbene was isolated and fully characterized, including
molecular structure determination by single crystal X-ray
diffraction analysis. Its reactivity toward sulfur showed the
oxidation of both tin and phosphorus atoms leading to a four-
membered Sn2S2 inorganic ring compound, probably by
dimerization of a stannathione intermediate. A different
behavior was observed for the germylene analogue with the
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NMR (C6D6): δ = −95.3 (tt, 2JSn−P = 270.7 Hz; 4JSn−P = 7.5 Hz). Anal.
Calcd for C76H116Cl4P4S6Sn2 (1725.25): C, 52.91; H, 6.78%. Found:
C, 53.46; H, 7.24%.
sole oxidation of the germanium center and the formation of
doubly bonded GeY (Y = S, Se) compounds. The
germaselenone was more stable than the germathione and
could be structurally characterized. The slightly larger steric
crowding around the GeY than around the SnY double
bonds due to shorter MY and M−C distances can probably
explain the nondimerization of the germathione and the
germaselenone. An unusual thermal cyclization reaction of the
germaselenone occurs with an excess of selenium to give a
Ge2Se3 inorganic ring (triselenadigermolane) derivative.
Compound 4. A suspension of S8 (0.03 g, 0.10 mmol) in toluene (2
mL) was added to a solution of germylene 7 (0.15 g, 0.17 mmol) in
toluene (2 mL) at −80 °C. The mixture was allowed to warm up to
room temperature when the solution became clear brown. The
solution was cooled again at low temperature (around −40 °C) and
filtered to remove the excess of sulfur. The solvent was evaporated
under reduced pressure and 4 was obtained as a red-brown powder
(0.13 g, 87%). Derivative 4 is stable in solution only for several hours,
decomposing to unidentified products. M.p.: 97−98 °C. 1H NMR
3
(C6D6): δ = 1.22 (d, JH−H = 6.9 Hz, 12H, CHMe2); 1.31 (s, 18H,
EXPERIMENTAL SECTION
■
CpCMe3); 1.54 (s, 6H, =CMe); 1.71 (s, 18H, CoCMe3); 1.76 (s, 18H,
4
General Procedures. All manipulations were performed in a dry
and oxygen-free atmosphere of argon by using standard Schlenk-line
and glovebox techniques. Solvents were purified with the MBRAUN
SBS-800 purification system. NMR spectra were recorded with a
Bruker Avance II 300 apparatus: 1H (300.13 MHz), 13C (75.48 MHz),
31P (121.50 MHz), 119Sn (111.92 MHz), and with a Bruker Avance
400: 77Se (76.27 MHz) at 298 K, in C6D6. Chemical shifts are
expressed in parts per million with residual solvent signals as internal
reference (1H and 13C{1H}) or with an external reference (H3PO4 for
31P, SnMe4 for 119Sn, and Me2Se for 77Se). Melting points were
CoCMe3); 6.50−6.80 (m, 2H, CHMe2); 7.62 (d, JH−P = 6.3 Hz, 4H,
CHAr). 31P NMR (C6D6): δ = 289.9.
Compound 5. A suspension of Se (0.03 g, 0.44 mmol) in toluene (3
mL) was added to a solution of germylene 7 (0.10 g, 0.11 mmol) in
toluene (3 mL) at −70 °C. After 30 min of stirring at room
temperature, the solution was filtered and the red filtrate was
evaporated under low pressure. Derivative 5 was isolated as a orange
powder (0.10 g, 96%), and crystallized from toluene at −24 °C. m.p.:
173 °C. 1H NMR (C6D6): δ = 1.23 (d, 3JH−H = 6.9 Hz, 12H, CHMe2);
1.32 (s, 18H, CpCMe3); 1.57 (s, 6H, CMe); 1.71 (s, 18H,
CoCMe3); 1.78 (s, 18H, CoCMe3); 6.45−6.65 (m, 2H, CHMe2); 7.62
(d, 4JH−P = 6.6 Hz, 4H, CHAr). 13C NMR (C6D6): δ = 10.36 (CMe);
22.02 (CHMe2); 31.41 (CpCMe3); 33.25, 33.59 (CoCMe3); 34.98
(CpCMe3); 38.10 and 38.87 (CoCMe3); 51.37 (CHMe2); 121.48 and
122.74 (Cm); 125.13 (C); 137.04 (d, 1JC−P = 66.9 Hz, CiP); 149.94
(t, 3JC−P = 10.0 Hz, C:); 150.11 (Cp); 153.63, 154.98 (Co); 172.29 (d,
1JC−P = 92.0 Hz, CP). 31P NMR (C6D6): δ = 291.3. 77Se NMR
(C6D6): δ = −173.7. Anal. Calcd for C49H78Cl2GeN2P2Se (979.61): C,
60.08; H, 8.03; N, 2.86%. Found: C, 60.60; H, 8.18; N, 3.31%.
Compound 6. A suspension of Se (0.05 g, 0.64 mmol) in toluene (2
mL), was added to a solution of 7 (0.14 g, 0.16 mmol) in toluene (4
mL) at −70 °C. The mixture was stirred for 30 min at room
temperature; the 31P NMR spectrum showed the complete conversion
to derivative 5. After heating for 2.5 h at 80 °C, the mixture was
filtered and the filtrate was completely evaporated under low pressure
to yield 6 as a red powder (0.16 g, 59%). Crystals suitable for X-ray
studies were obtained from toluene at −24 °C. m.p.: 92 °C. 1H NMR
(C6D6): δ = 1.28 (s, 36H, CpCMe3); 1.60 (s, 36H, CoCMe3); 1.62 (s,
measured in a sealed capillary using the Stuart automatic melting point
10a
SMP40 apparatus. The compounds NHC−SnCl2
and Mes*P
25
CCl2 were prepared according to literature procedures.
Synthesis. Compound 1. A suspension of NHC−SnCl2 (0.30 g,
0.82 mmol) in THF (3 mL) was added to a solution of Mes*P
C(Li)Cl25,26 (1.64 mmol) freshly prepared in THF (6 mL) at −90 °C.
After 1 h of stirring at low temperature, the solution was allowed to
warm up to room temperature and was stirred for an additional one
hour. The volatiles were removed under reduced pressure and the
residue was extracted with toluene (12 mL). After filtration, the filtrate
was evaporated under vacuum to yield 1 as a light brown powder (0.63
g, 82%). Crystallization from a saturated toluene solution at room
temperature gave brown crystals suitable for X-ray studies. m.p.: 157
3
°C (dec). 1H NMR (C6D6): δ = 1.19 (d, JH−H = 7.0 Hz, 12H,
CHMe2); 1.35 (s, 18H, CpCMe3); 1.51 (s, 6H, CMe); 1.74 (s, 18H,
3
CoCMe3); 1.78 (s, 18H, CoCMe3); 5.62 (sept, JH−H = 6.8 Hz, 2H,
CHMe2); 7.64 (s, 4H, CHAr). 13C NMR (C6D6): δ = 10.12 (CMe);
22.16 (CHMe2); 31.55 (CpCMe3); 32.64 and 32.73 (CoCMe3); 34.98
(CpCMe3); 38.11 and 38.26 (CoCMe3); 53.24 (CHMe2); 121.29 and
121.70 (Cm); 126.20 (NC); 140.74 (dd, 1JC−P = 83.9 Hz, 5JC−P = 8.5
Hz, CiP); 149.22 (Cp); 153.46 (d, 2JC−P = 7.3 Hz, Co); 175.29 (t, 3JC−P
= 14.4 Hz, C:); 205.13 (dd, 1JC−P = 108.2 Hz, 3JC−P = 19.2 Hz, CP).
4
36H, CoCMe3); 7.59 (d, JH−P = 2.7 Hz, 8H, CHAr). 13C NMR
(C6D6): δ = 31.30 (CpCMe3); 33.16 (CoCMe3); 35.05 (CpCMe3);
38.04 and 38.08 (CoCMe3); 122.35 (Cm); 134.91 (d, 1JC−P = 66.0 Hz,
1
CiP); 151.18 (Cp); 154.05 and 154.42 (Co); 163.78 (dd, JC−P = 88.6
5
Hz, JC−P = 8.0 Hz, CP). 31P NMR (C6D6): δ = 295.8. 77Se NMR
31P NMR (C6D6): δ = 277.4 (2JP−
NMR (C6D6): δ = −130.8 (t, JSn−P = 360.0 Hz). Anal. Calcd for
C49H78Cl2N2P2Sn (946.72): C, 62.16; H, 8.30; N, 2.96%. Found: C,
62.28; H, 8.25; N, 3.50%.
= 349.1/364.1 Hz). 119Sn
117/119Sn
2
(C6D6): δ = −160.4 and −500.0 ppm. Anal. Calcd for
C76H116Cl4Ge2P4Se3 (1677.60): C, 54.41; H, 6.97%. Found: C,
54.94; H, 7.53%.
X-ray Structure Determinations. X-ray data for compounds 1, 3,
5, and 6 were collected at low temperature (193 K) on a Bruker-AXS
SMART APEX II diffractometer (compound 1) and on a Bruker-AXS
APEX II Quazar diffractometer using a 30 W air-cooled microfocus
source (ImS) with focusing multilayer optics (compounds 3, 5 and 6)
with graphite-monochromated MoKα radiation (wavelength =
0.71073 Å) by using phi- and omega-scans. The data were integrated
with SAINT, and an empirical absorption correction with SADABS
was applied.27 The structures were solved by direct methods, using
SHELXS-9728 and refined using the least-squares method on F2.29 All
non-H atoms were treated anisotropically. The H atoms were located
by difference Fourier maps and refined with a riding model.
Crystallographic data are summarized in Table 1.
Compound 2. A freshly prepared solution of Mes*PC(Li)Cl
(0.83 mmol) in THF (3 mL) was added to a suspension of SnCl2
(0.08 g, 0.42 mmol) in THF (2 mL) at −90 °C. The solution was
stirred for 15 min and then allowed to warm up to room temperature.
The compound 2 was identified by 31P NMR spectrometry (δ = 264.0
ppm). Addition of the carbene NHC directly into the NMR tube led
to the formation of compound 1.
Compound 3. A suspension of S8 (0.02 g, 0.08 mmol) in toluene (2
mL) was added to a solution of 1 (0.10 g, 0.11 mmol) in toluene (1
mL) at −70 °C. After warming up to room temperature, the orange
solution was stirred for 2 h. After filtration and evaporation of the
solvent under reduced pressure, derivative 3 was isolated as a yellow
powder (0.11 g, 61%). Yellow crystals suitable for X-ray studies were
obtained from toluene at −24 °C. m.p.: 180 °C. 1H NMR (C6D6): δ =
4
1.18 (s, 36H, CpCMe3); 1.86 (s, 72H, CoCMe3); 7.64 (d, JH−P = 5.4
ASSOCIATED CONTENT
■
Hz, 8H, CHAr). 13C NMR (C6D6): δ = 30.85 (CpCMe3); 33.97
(CoCMe3); 35.29 (CpCMe3); 39.34 (CoCMe3); 122.71 (d, 1JC−P = 54.8
Hz, CiP); 123.96 (d, 3JC−P = 13.4 Hz, Cm); 135.69 (d, 1JC−P = 67.8 Hz,
CP); 154.94 (d, 4JC−P = 3.3 Hz, Cp); 156.23 (d, 2JC−P = 7.4 Hz, Co).
S
* Supporting Information
Crystallographic data in CIF format for compounds 1, 3, 5, and
6. This material is available free of charge via the Internet at
http://pubs.acs.org
31P NMR (C6D6): δ = 189.2 (2JP−
= 258.8/270.7 Hz). 119Sn
117/119Sn
7786
dx.doi.org/10.1021/ic300810q | Inorg. Chem. 2012, 51, 7782−7787

Inorganic Chemistry
Article
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AUTHOR INFORMATION
Corresponding Author
*E-mail: sgabi@chem.ubbcluj.ro (G.N.); castel@chimie.ups-
tlse.fr (A.C.).
■
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
We are grateful to the CNRS (ANR-08-BLAN-0105-01) and
Romanian Agency UEFISCDI (PCCE-140/2008) for financial
support of this work. T. K. thanks also POSDRU (contract 88/
1.5/S/60185 “Investing in people!”).
(17) Kuhn, N.; Kratz, T. Synthesis 1993, 561−562.
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