The first O,C,S-coordinating pincer-type ligand and its application to the synthesis of a triorganotin cation stabilized by two different donor atoms

Article abstract of DOI:10.1021/om0600590

The syntheses and molecular structures of the bromo-substituted triarylphosphane sulfide (3-Br-5-t-Bu-C₆H₃)P(S)Ph ₂ (1), the arylphosphonic acid di-isopropyl ester {3-t-Bu-5-[P(S)Ph₂]-C₆H₃}P(O)(O-i-Pr) ₂ (2), its triphenyltin derivative {5-t-Bu-3-[P(S)Ph ₂]-2-(SnPh₃)-C₆H₂}P(O)(O-i-Pr) ₂ (3), and the corresponding triorganostannylium salt {4-t-Bu-2-[P(O)(O-i-Pr)₂]-6-[P(S)Ph₂]-C₆H ₂}SnPh₂⁺PF₆^- (4) are reported. By reaction with bromide ion, the latter is converted in situ to the intramolecularly coordinated benzoxaphosphastannole derivative [1(P),3(Sn)-SnPh₂OP(O)(O-i-Pr)-6-t-Bu-4-P(S)Ph₂]C ₆H₂ (5). Ab initio MO calculations on the ethoxy-substituted analogue of compound 4 indicate a reduced positive charge at the tin atom in comparison with previously reported {4-t-Bu-2,6-[P(O)(OEt) ₂]₂C₆H₂}SnPh₂ ⁺PF₆^-.

Full text of DOI:10.1021/om0600590

2886
Organometallics 2006, 25, 2886-2893
The First O,C,S-Coordinating Pincer-Type Ligand and Its
Application to the Synthesis of a Triorganotin Cation Stabilized by
Two Different Donor Atoms†
Jan Fischer, Markus Schu¨rmann, Michael Mehring, Uwe Zachwieja, and Klaus Jurkschat*
Lehrstuhl fu¨r Anorganische Chemie II der UniVersita¨t Dortmund, D-44221 Dortmund, Germany
ReceiVed January 20, 2006
The syntheses and molecular structures of the bromo-substituted triarylphosphane sulfide (3-Br-5-t-
Bu-C6H3)P(S)Ph2 (1), the arylphosphonic acid di-isopropyl ester {3-t-Bu-5-[P(S)Ph2]-C6H3}P(O)(O-i-
Pr)2 (2), its triphenyltin derivative {5-t-Bu-3-[P(S)Ph2]-2-(SnPh3)-C6H2}P(O)(O-i-Pr)2 (3), and the
+
corresponding triorganostannylium salt {4-t-Bu-2-[P(O)(O-i-Pr)2]-6-[P(S)Ph2]-C6H2}SnPh2 PF6- (4) are
reported. By reaction with bromide ion, the latter is converted in situ to the intramolecularly coordinated
benzoxaphosphastannole derivative [1(P),3(Sn)-SnPh2OP(O)(O-i-Pr)-6-t-Bu-4-P(S)Ph2]C6H2 (5). Ab initio
MO calculations on the ethoxy-substituted analogue of compound 4 indicate a reduced positive charge
+
-
at the tin atom in comparison with previously reported {4-t-Bu-2,6-[P(O)(OEt)2]2C6H2}SnPh2 PF6 .
Chart 1
Introduction
Since their first appearance in the late 1970s1-3 L,C,L′-
coordinating pincer-type ligands of types A-H (Chart 1) have
become a rather popular class of compounds, the chemistry of
which has been thoroughly reviewed.4-6 Over the years the
classic pincer-type ligands (A-H) containing a phenyl backbone
and methylene bridges between the donor atoms L, L′ and the
phenyl ring have been modified and developed further to give
ligands containing oxygen (types I, J)7,8 or nitrogen (types K,
L)9,10 bridges, or anthracene (type M)11 and ferrocene12,13 (type
N) backbones, respectively (Chart 1). What makes all these
ligands so fascinating is their ability to stabilize metals in
unusual oxidation states and to participate, as their metal
complexes, in a variety of homogeneously catalyzed organic
reactions.14-16 In recent years C-H bond activation was also
achieved with pincer-type ligand-containing organometallic
† Dedicated to Professor Herbert Jacobs on the occasion of his 70th
birthday. Part of this work was first presented at the Symposium of the
Graduiertenkolleg 352, Synthetic, Mechanistic and Reaction-Engineering
Aspects of Metal-Containing Catalysts, November 17, 2005, TU Berlin,
Germany, Book of Abstracts, p 17.
(1) Shaw, B. L.; Moulton, C. J. J. Chem. Soc., Dalton Trans. 1976, 1020.
(2) Shaw, B. L.; Crocker, C.; Errington, R. J.; McDonald, W. S.; Odell,
K. J.; Goodfellow, R. J. J. Chem. Soc., Chem. Commun. 1979, 498.
(3) Shaw, B. L.; Errington, J.; McDonald, W. S. J. Chem. Soc., Dalton
Trans. 1980, 2312.
(4) van Koten, G.; Albrecht, M. Angew. Chem., Int. Ed. 2001, 40, 3750.
(5) Singleton, J. T. Tetrahedron 2003, 59, 1837.
(6) Milstein, D.; van der Boom, M. E. Chem. ReV. 2003, 103, 1759.
(7) Brookhart, M.; Gottker-Schnetmann, I.; White, P. S. Organometallics
2004, 23, 1766.
(8) Jensen, C. M.; Wang, Z. H.; Eberhard, M. R.; Matsukawa, S.;
Yamamoto, Y. J. Organomet. Chem. 2003, 681, 189.
(9) Vicente, J.; Arcas, A.; Galvez-Lopez, M. D.; Jones, P. G. Organo-
metallics 2004, 23, 3521.
(10) Sole, D.; Vallverdu, L.; Solans, X.; Font-Bardia, M. Chem. Commun.
2005, 2738.
compounds.17 Among the pincer-type ligands reported so far
there are only a few representatives containing different donor
sites L and L′ in one molecule (types G,18 H,19 L10).
(11) Haenel, M. W.; Oevers, S.; Angermund, K.; Kaska, W. C.; Fan, H.
J.; Hall, M. B. Angew. Chem., Int. Ed. 2001, 40, 3596.
(12) van Koten, G.; Farrington, E. J.; Viviente, E. M.; Williams, B. S.;
Brown, J. M. Chem. Commun. 2002, 308.
(13) Koridze, A. A.; Kuklin, S. A.; Sheloumov, A. M.; Dolgushin, F.
M.; Lagunova, V. Y.; Petukhova, II; Ezernitskaya, M. G.; Peregudov, A.
S.; Petrovskii, P. V.; Vorontsov, E. V.; Baya, M.; Poli, R. Organometallics
2004, 23, 4585.
For some time we have been interested in phosphorus-
containing O,C,O- and S,C,S-coordinating pincer-type ligands
(15) Beletskaya, I. P.; Cheprakov, A. V. J. Organomet. Chem. 2004,
689, 4055.
(16) Szabo, K. J.; Sebelius, S.; Olsson, V. J. J. Am. Chem. Soc. 2005,
127, 10478.
(14) Bedford, R. B. Chem. Commun. 2003, 1787.
(17) Jensen, C. M. Chem. Commun. 1999, 2443.
10.1021/om0600590 CCC: $33.50 © 2006 American Chemical Society
Publication on Web 04/21/2006

The First O,C,S-Coordinating Pincer-Type Ligand
Organometallics, Vol. 25, No. 11, 2006 2887
Scheme 1
of types P20,21 and Q,22 respectively (Chart 1). These ligands
have been applied in the synthesis of intramolecularly coordi-
nated main group metal and metalloid compounds as well as
of palladium complexes. Notably, a related S,C,S-coordinating
ligand of type O23 (Chart 1) was reported in 2003.
Figure 1. General view (SHELXTL) of a molecule of 1 showing
30% probability displacement ellipsoids and the atom numbering.
In continuation of our studies we report here the synthesis
of the first O,C,S-coordinating pincer-type ligand of type R
(Chart 1), in its protonated form, and its triphenyltin derivative.
The latter was converted into an intramolecularly coordinated
triorganotin cation which showed remarkable stability against
moisture but reacted with bromide ion to give, in situ, an
intramolecularly PdS-coordinated benzoxaphosphastannole.
Results and Discussion
The one-pot subsequent reaction of 1,3-di-bromo-5-tert-
butylbenzene with n-butyllithium, chlorodiphenylphosphine, and
elemental sulfur provided the bromo-substituted triarylphos-
phane sulfide (3-Br-5-t-Bu-C6H3)P(S)Ph2 (1) in good overall
yield (Scheme 1). Compound 1 is a colorless solid, the molecular
structure of which is shown in Figure 1. Selected geometric
parameters are collected in Table 1. The phosphorus atom
exhibits a distorted tetrahedral configuration (bond angles
between 105.0(1)° (C21-P1-C2) and 113.24(8)° (C11-P1-
S1). Notably, there are intramolecular S(1)‚‚‚H(1) and S(1)‚‚‚
H(12) distances of 2.90(2) and 2.84(2) Å, respectively, being
shorter than the sum of the van der Waals radii24 of these atoms
(H: 1.20-1.40 Å, S: 1.80 Å). For the parent triphenylphosphine
sulfide, Ph3PS, there is one intramolecular S‚‚‚H distance of
2.79 Å.25
Figure 2. General view (SHELXTL) of a molecule of 2 showing
30% probability displacement ellipsoids and the atom numbering
(only one representative of the two symmetry-independent mol-
ecules is shown).
Table 1. Selected Bond Lengths (Å) and Bond Angles (deg)
for 1 and 2
1
2
P(1)-S(1)
1.9556(8)
1.954(1)
1.461(2)
1.567(2)
1.582(2)
112.25(9)
113.49(9)
106.8(1)
105.1(1)
112.73(9)
105.9(1)
113.8(1)
117.1(1)
103.0(1)
113.8(1)
109.6(1)
97.9(1)
P(2)-O(2)
A TAVS reaction26 catalyzed by NiBr2 of the bromo-
substituted triarylphosphane sulfide 1 with tri-isopropyl phos-
phite, (i-PrO)3P, gave the arylphosphonic acid diisopropyl ester
{3-t-Bu-5-[P(S)Ph2]-C6H3}P(O)(O-i-Pr)2 (2) in moderate yield
(Scheme 1). Notably, the reaction is not prevented by the sulfur
atom present in compound 1. The molecular structure of
P(2)-O(2′)
P(2)-O(2′′)
C(2)-P(1)-S(1)
C(11)-P(1)-S(1)
C(11)-P(1)-C(2)
C(11)-P(1)-C(21)
C(21)-P(1)-S(1)
C(21)-P(1)-C(2)
O(2)-P(2)-O(2′)
O(2)-P(2)-O(2′′)
O(2′)-P(2)-O(2′′)
O(2)-P(2)-C(6)
O(2′)-P(2)-C(6)
O(2′′)-P(2)-C(6)
C(1)-C(2)-P(1)
C(1)-C(6)-P(2)
112.73(7)
113.24(8)
106.21(9)
106.2(1)
112.73(7)
105.0(1)
(18) Milstein, D.; Poverenov, E.; Gandelman, M.; Shimon, L. J. W.;
Rozenberg, H.; Ben-David, Y. Organometallics 2005, 24, 1082.
(19) Milstein, D.; Rybtchinski, B.; Oevers, S.; Montag, M.; Vigalok, A.;
Rozenberg, H.; Martin, J. M. L. J. Am. Chem. Soc. 2001, 123, 9064.
(20) Fischer, J. Diploma thesis, Dortmund University, 2003.
(21) Jurkschat, K.; Fischer, J.; Schu¨rmann, M.; Krause, N.; Lo¨hr, S.
Symposium of the Graduiertenkolleg 352, Synthetic, Mechanistic and
Reaction-Engineering Aspects of Metal-Containing Catalysts, November
17, 2005, TU Berlin, Germany, Book of Abstracts, p 17.
(22) Mehring, M.; Schu¨rmann, M.; Jurkschat, K. Organometallics 1998,
17, 1227.
118.7(2)
119.4(2)
120.1(2)
compound 2 is shown in Figure 2, and selected geometric
parameters are collected in Table 1.
In the unit cell there are two crystallographically independent
molecules whose geometric parameters differ marginally, and
consequently the structure of only one molecule is briefly
(23) Yamamoto, T.; Kanbara, T. J. Organomet. Chem. 2003, 688, 15.
(24) Bondi, A. J. Phys. Chem. 1964, 68, 441.
(25) Ziemer, B.; Rabis, A.; Steinberger, H. U. Acta Crystallogr. Sect.
C: Cryst. Struct. Commun. 2000, 56, E58.
(26) Tavs, P. Chem. Ber. 1970, 103, 2428.

2888 Organometallics, Vol. 25, No. 11, 2006
Fischer et al.
Scheme 2
Figure 3. General view (SHELXTL) of a molecule of 3 showing
30% probability displacement ellipsoids and the atom-numbering
scheme.
discussed. The phosphorus atoms exhibit distorted tetrahedral
configurations with the distortion being more pronounced for
the phosphonic ester phosphorus (angles between 97.9(1)° and
117.1(1)° at P2 versus 105.1(1)° and 113.49(9)° at P1). As in
compound 1, the sulfur atom S(1) points to H(1) with a distance
of 2.75(2) Å, whereas the O(3) oxygen atom points away, with
the consequence of the isopropoxy oxygen atom O(2′′) ap-
proaching H(1) at a distance of 2.77(2) Å. A similar situation
was observed for the phosphoryl groups in the related com-
pounds 1,3-[P(O)(OR)2]2-5-t-Bu-C6H3 (R ) Et, i-Pr).27,28
Metalation of compound 2 was achieved with lithium
diisopropyl amide, LiN(i-Pr)2, in diethyl ether/hexane in the
temperature range between -50 and 0 °C. Subsequent reaction
with triphenyltin chloride, Ph3SnCl, and recrystallization from
dichloromethane/hexane provided the tetraorganotin compound
{5-t-Bu-3-[P(S)Ph2]-2-(SnPh3)-C6H2}P(O)(O-i-Pr)2 (3), as its
CH2Cl2 solvate 3‚0.6 CH2Cl2, as a colorless crystalline solid in
poor yield (Scheme 2). The molecular structure of compound
3 is shown in Figure 3, and selected geometric parameters are
collected in Table 2.
As in the related intramolecularly coordinated tetraorganotin
compounds {4-t-Bu-2,6-[P(O)(OEt)2]2C6H2}SnPh2R (R ) Ph,22
Me3SiCH229), the tin atom in compound 3 adopts a typical [4+2]
coordination. A distorted tetrahedron (mean angle 109.55°) with
bond angles ranging between 95.5(1)° (C51-Sn1-C61) and
125.5(1)° (C1-Sn1-C61) is capped with O(2) at the opposite
face of the carbon atom C(61) and with S(1) at the opposite
face of the carbon atom C(51), at O(2)‚‚‚Sn(1) and S(1)‚‚‚Sn-
(1) distances of 2.956(2) and 3.513(1) Å, respectively. These
distances are 0.744 and 0.487 Å shorter than the sums of the
van der Waals radii24 of tin (2.20 Å) and oxygen (1.50 Å), and
tin and sulfur (1.80 Å), respectively. Notably, these intra-
molecular OfSn and SfSn interactions lengthen the Sn(1)-
C(61) and Sn(1)-C(51) distances to 2.161(3) and 2.156(3) Å,
respectively, with respect to the remaining tin-phenyl bond Sn-
(1)-C(41) (2.137(3) Å). As in the previously reported sym-
metrically substituted pincer-type ligand-substituted tetraorga-
notin compound {4-t-Bu-2,6-[P(O)(OEt)2]2C6H2}SnPh3, the
C(1)-Sn(1) distance is the longest among the tin-carbon bond
lengths and amounts to 2.202(19) Å.22 A comparison of the
C(1)-C(2)-P(1) (121.1(3)°) and C(1)-C(6)-P(2) (124.5(3)°)
angles, assigned as R, R′ angles,27 with the corresponding angles
Table 2. Selected Bond Lengths (Å) and Bond Angles (deg)
for 3 and 4
3
4
Sn(1)-C(1)
2.201(3)
2.137(3)
2.156(3)
2.161(3)
2.956(2)
3.513(1)
1.948(1)
1.464(2)
1.572(2)
1.575(2)
109.7(1)
103.5(1)
125.5(1)
119.1(1)
104.1(1)
95.5(1)
2.159(3)
2.129(3)
2.129(3)
Sn(1)-C(41)
Sn(1)-C(51)
Sn(1)-C(61)
Sn(1)-O(1)
2.278(2)
2.6295(9)
2.006(1)
1.501(2)
1.542(2)
1.562(1)
113.5(1)
122.2(1)
Sn(1)-S(1)
P(1)-S(1)
P(2)-O(2)
P(2)-O(2′)
P(2)-O(2′′)
C(1)-Sn(1)-C(41)
C(1)-Sn(1)-C(51)
C(1)-Sn(1)-C(61)
C(41)-Sn(1)-C(51)
C(41)-Sn(1)-C(61)
C(51)-Sn(1)-C(61)
C(1)-Sn(1)-O(2)
C(1)-Sn(1)-S(1)
C(41)-Sn(1)-O(2)
C(41)-Sn(1)-S(1)
C(51)-Sn(1)-O(2)
C(51)-Sn(1)-S(1)
C(61)-Sn(1)-O(2)
C(61)-Sn(1)-S(1)
O(2)-Sn(1)-S(1)
C(1)-C(2 -P(1)
C(1)-C(6)-P(2)
123.5(1)
75.7(1)
72.31(9)
70.7(1)
91.7(1)
98.97(9)
90.1(1)
94.63(9)
79.77(9)
86.12(8)
81.42(9)
70.18(9)
158.61(9)
157.7(1)
71.95(9)
126.65(4)
121.1(3)
124.5(3)
162.42(5)
119.3(2)
116.1(2)
in the parent compound 2 (119.4(2)°, 120.1(2)°) suggests,
however, that these intramolecular interactions are rather weak.
This view is supported by the facts that (i) in comparison with
the organotin-free derivative 2 the P(1)-S(1) (1.948(1) Å) and
P(2)-O(2) (1.464(2) Å) distances are almost unchanged, (ii)
the ν˜(PdO) of 1241 cm-1 is rather close to that of compound
2 (1249 cm-1), and (iii) both the O(2) and S(1) atoms are
displaced by 0.611(6) and 1.497(6) Å from the least-squares
plane defined by the aromatic carbon atoms C(2)-C(6). In the
trioganotin cation 4 (see below) this displacement is much less
pronounced (Figure 4).
The weak intramolecular OfSn and SfSn interactions in
compound 3 are retained in solution. This is especially
manifested by its low-frequency 119Sn NMR chemical shift of
δ -194 as compared to δ -128 found for tetraphenyltin,
SnPh4.30
(27) Henn, M.; Jurkschat, K.; Ludwig, R.; Mehring, M.; Peveling, K.;
Schu¨rmann, M. Z. Anorg. Allg. Chem. 2002, 628, 2940-2947.
(28) Henn, M. Ph.D. Thesis, Dortmund University, 2004.
(29) Mehring, M.; Lo¨w, C.; Schu¨rmann, M.; Uhlig, F.; Jurkschat, K.;
Mahieu, B. Organometallics 2000, 19, 4613.
Reaction of the [4+2]-coordinated tetraorganotin compound
3 with triphenylmethyl hexafluorophosphate, CPh3+PF6-, pro-

The First O,C,S-Coordinating Pincer-Type Ligand
Organometallics, Vol. 25, No. 11, 2006 2889
The separation between the triorganotin cation {4-t-Bu-2-
[P(O)(O-i-Pr)2]-6-[P(S)Ph2]-C6H2}SnPh2+ and the hexafluoro-
-
phosphate anion PF6 amounts to 5.855(11) Å and indicates
no bonding interaction. Overall, the geometrical data including
the intramolecular O(2)‚‚‚Sn(1) distance of compound 4 re-
semble those of the related organotin salt {4-t-Bu-2,6-[P(O)-
(Oi-Pr)2]2C6H2}SnPh2+PF6- 34 (geometrical goodness31-33 ∆Σ-
(θ) ) 84.6°; O‚‚‚Sn 2.249(2), 2.241(3) Å).
In solution, the triorganotin hexafluorophosphate 4 shows a
119Sn NMR chemical shift of δ -132, which is high-frequency
+
shifted as compared to {4-t-Bu-2,6-[P(O)(Oi-Pr)2]2C6H2}SnPh2 -
-
PF6 containing two PdO donor functions (δ -208).34 This
difference is in line with the trend observed for the chemical
shifts of solutions containing equimolar mixtures of Ph3SnCl/
Ph3PO (δ -94) and Ph3SnCl/Ph3PS (δ -46), respectively.
Another interesting fact to be noticed is the dramatic decrease
of the J(119Sn-31P(O)) couplings, as compared to the related
tetraorganotin derivatives {4-t-Bu-2,6-[P(O)(Oi-Pr)2]2C6H2}-
SnPh3 (35 Hz)34 and 3 (28 Hz), respectively, for both {4-t-Bu-
2,6-[P(O)(Oi-Pr)2]2C6H2}SnPh2+PF6- 34 (5 Hz) and compound
4 to the extent that in the latter this coupling was detected neither
in the 119Sn nor in the 31P NMR spectrum because of line
broadening (ν1/2 9 Hz, 5 Hz). The J(119Sn-31P(S)) coupling in
4 (37 Hz) decreases as well with respect to compound 3 (56
Hz). The coupling constants actually observed are absolute
values and composed of different coupling pathways 2J(119Sn-
Figure 4. View along the aromatic plane of compounds 3 (left)
and 4 (right).
3
X-31P) (X ) O, S) and J(119Sn-C-C-31P). These coupling
pathways might have different signs and magnitudes, which in
turn can change upon changes of the substituent pattern at the
tin or phosphorus atoms and/or the conformation of the
molecule. The conversion of the tetraorganotin compound 3 to
the corresponding triorganotin cation 4 is associated with such
a change, and consequently, the magnitude of the coupling
constant changes. Similar observations for o-Ph2P(O)C6H4-
SnMe2X (X ) Me, Br) were already noticed by Weichmann
and Schmoll.35
Figure 5. General view (SHELXTL) of an ion pair of 4 showing
30% probability displacement ellipsoids and the atom-numbering
scheme.
The natural bond orbital (NBO) analyses on model com-
pounds (Table 3) in which the isopropoxy substituents are
replaced by ethoxy substituents shows (i) that the positive charge
at the tin atom in [R′SnPh2]+ (R′ ) S,C,O-coordinating ligand;
the ethoxy-substituted analogue of the cation in compound 4)
is reduced with respect to [RSnPh2]+ 34 (R ) O,C,O-coordinat-
ing ligand), (ii) that in [R′SnPh2]+ the positive charge at both
phosphorus atoms increases with respect to R′H with the effect
being more pronounced for the PdO phosphorus atom, and (iii)
that in [R′SnPh2]+ the PdOfSn charge transfer is higher than
in [RSnPh2]+ and slightly dominates over the one induced by
PdSfSn. The results suggest that compared with {4-t-Bu-2,6-
vided the intramolecularly coordinated triorganotin hexafluo-
rophosphate {4-t-Bu-2-[P(O)(O-i-Pr)2]-6-[P(S)Ph2]-C6H2}SnPh2+-
-
PF6 (4) as colorless crystals in good yield (Scheme 2). The
molecular structure of compound 4 is shown in Figure 5.
Selected geometric parameters are given in Table 2.
The tin atom in compound 4 shows a distorted trigonal
bipyramidal configuration (geometrical goodness31-33 ∆Σ(θ) )
79.44°) with the carbon atoms C(1), C(41), and C(51) in
equatorial and the oxygen and sulfur atoms O(2) and S(1),
respectively, in axial positions. The Sn(1) atom is deviated by
0.113(2) Å in the direction of S(1) from the plane defined by
C(1), C(41), and C(51). Compared with the tetraorganotin
derivative 3, the intramolecular O(2)‚‚‚Sn(1) (2.278(2) Å) and
S(1)‚‚‚Sn(1) (2.6295(9) Å) distances are considerably shortened
by 0.678 and 0.884 Å, respectively. This shortening causes a
simultaneous lengthening of the P(2)-O(2) and P(1)-S(1)
distances to 1.501(2) and 2.006(1) Å, respectively, with the
former also being illustrated by a decrease of the ν˜(PdO) to
1155 cm-1. The C(1)-C(2)-P(1) and C(1)-C(6)-P(2) angles
(R, R′ angles27) decrease to 119.3(2)° and 116.1(2)°, respec-
tively.
+
[P(O)(O-i-Pr)2]2C6H2}SnPh2 for compound 4 the importance
of the canonical formula (II) with the positive charge located
at the PdO phosphorus atom increases, without, however,
dominating over canonical formula (I) (Chart 2). Apparently,
the charge distribution can be controlled by the identity of the
donor atom. These statements get further support by the ν˜(Pd
O) being smaller for compound 4 (1155 cm-1) than for {4-t-
Bu-2,6-[P(O)(O-i-Pr)2]2C6H2}SnPh2+PF6 (1177 cm-1).34 On
-
the other hand, the Wiberg bond indices36,37 of 0.4040 and
0.2157 indicate a higher covalent character of the Sn-S as
compared to the Sn-O bond, and consequently, the canonical
formula (III) appears also to be meaningful. At this point it
(30) Lycka, A.; Snobl, D.; Handlir, K.; Holecek, J.; Nadvornik, M.
Collect. Czech. Chem. Commun. 1981, 46, 1383.
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13, 4413.
(32) Kolb, U.; Beuter, M.; Dra¨ger, M. Inorg. Chem. 1994, 33, 4522.
(33) Kolb, U.; Dra¨ger, M.; Jousseaume, B. Organometallics 1991, 10,
2737.
(34) Peveling, K.; Henn, M.; Lo¨w, C.; Mehring, M.; Schu¨rmann, M.;
Costisella, B.; Jurkschat, K. Organometallics 2004, 23, 1501.
(35) Weichmann, H.; Schmoll, C. Z. Chem. 1984, 24, 390.
(36) Mayer, I. Chem. Phys. Lett. 1983, 97, 270.
(37) Wiberg, K. A. Tetrahedron 1968, 24, 1083.

2890 Organometallics, Vol. 25, No. 11, 2006
Fischer et al.
+
Table 3. Selected Results of the NBO Analysis for 5-t-Bu-1,3-[P(O)(OEt)2]2C6H3 (RH), {4-t-Bu-2,6-[P(O)(OEt)2]2-C6H2}SnPh2
+
+
(RSnPh2+), {3-t-Bu-5-[P(S)Ph2]-C6H3}P(O)(OEt)2 (R′H), and {4-t-Bu-2-[P(O)(OEt)2]-6-[P(S)Ph2]-C6H2}SnPh2 (R′SnPh2
)
Calculated at the B3LYP/LANL2DZ Level of Theory (atomic charges; charge transfer, au; orbital occupation)
NBO charges
charge transfer
PdO
PdS
PdO
PdS
M
PdOfM
PdSfM
occ(p(M))
RH
R′H
RSnPh2
+2.282
+2.274
+2.355
+2.361
+2.363
-1.053
-1.046
-1.158
-1.159
-1.164
+1.231
-0.592
+
+2.350
+2.165
0.122
0.135
0.198
0.284
+
R′SnPh2
+1.297
-0.548
0.115
Chart 2
its distribution in the cation by the identity of the coordinating
donor atoms has been shown. This work contributes to the
general understanding of structure and reactivity of organoele-
ment-14 cations as a field of ongoing interest.39-45 Given the
fact that organotin-based Lewis acids46,47 are catalysts for a
variety of organic reactions, it even suggests the possibility for
tailoring such catalysts by variation of coordinating donor atoms.
Experimental Section
General Considerations. All solvents were dried and purified
by standard procedures. All reactions were carried out under an
atmosphere of dry argon. SnPh3Cl and CPh3+PF6- were purchased
from Lancaster and Aldrich, respectively, and used without further
purification. IR spectra (cm-1) were recorded on a Bruker IFS 28
spectrometer. Varian Mercury 200, Bruker DPX-300, and DRX-
400 spectrometers were used to obtain 1H, 13C, 31P, and 119Sn NMR
should be mentioned that the classification of so-called datiVe
bonds as being covalent or ionic is still a matter of controversial
debate.38
The triorganotin hexafluorophosphate 4 is stable toward
moisture, but it does react with tetraphenylphosphonium bro-
1
spectra. H, 13C, 31P, and 119Sn NMR chemical shifts are given in
ppm and were referenced to Me4Si, H3PO4 (85%, 31P) and Me4Sn
(
119Sn). NMR spectra were recorded at room temperature unless
otherwise stated. The atom numberings given in Figures 3 and 4
apply for the assignment of the 13C resonances of compounds 3
and 4. Elemental analyses were performed on a LECO-CHNS-932
analyzer.
mide, Ph4PBr (Scheme 2), in a manner analogous to that for
- 34
{4-t-Bu-2,6-[P(O)(OEt)2]2C6H2}SnPh2+PF6
.
Thus, the 31P
NMR spectrum of a C2D2Cl4 solution containing equimolar
amounts of compound 4 and Ph4PBr, which had been heated to
65° C for 6 h, exhibited two equally intense doublet resonances
at δ 15.2 (ν1/2 1.6 Hz, J(31P-31P) ) 2.0 Hz) and δ 51.4 (ν1/2 4
Hz, J(31P-31P) ) 2.0 Hz, J(31P-119Sn) ) 64.8 Hz). The 119Sn
NMR spectrum of the same solution contained a resonance at
δ -168 (ν1/2 18 Hz, J(31P-119Sn) ) 65 Hz). The signals are
assigned to hypercoordinated benzoxaphosphastannole derivative
5 (Scheme 2), which, however, was not isolated from the
reaction mixture. In both the 31P and 119Sn NMR spectra, again
only one instead of the expected two J(31P-119Sn) couplings
were observed. The explanation for this is the same as given
above. The assignment of the NMR signals gets support from
the electrospray mass spectrum (positive mode) of the crude
product, showing a mass cluster centered at m/z ) 745.1 and
which corresponds to the empirical formula C37H39O3P2SSn,
i.e., protonated benzoxaphosphastannole [5-H]+.
Electrospray mass spectra were recorded in the positive mode
on a Thermoquest-Finnigan instrument using CH3CN as the mobile
phase. The samples were introduced as solution in a mixture of
CH3CN and 1% formic acid (9:1 ratio) (c ) 10-4 mol L-1) via a
syringe pump operating at 0.5 µL/min. The capillary voltage was
4.5 kV, while the cone skimmer voltage was varied between 50
and 250 kV. Identification of the inspected ions was assisted by
comparison of experimental and calculated istope distribution
patterns. The m/z values reported correspond to those of the most
intense peak in the corresponding isotope pattern.
Molecular Orbital Calculations. Calculations of the structures
and energies of 5-t-Bu-1,3-[P(O)(OEt)2]2C6H3,34 {4-t-Bu-2,6-[P(O)-
(OEt)2]2-C6H2}SnPh2+ 34
, {3-t-Bu-5-[P(S)Ph2]-C6H3}P(O)(OEt)2, and
{4-t-Bu-2-[P(O)(OEt)2]-6-[P(S)Ph2]-C6H2}SnPh2+ have been carried
out at the density functional (B3LYP) level with the Gaussian 98
program48 using the internal stored LANL2DZ basis set. This basis
(39) Zharov, I.; Michl, J. The Chemistry of Organic Germanium, Tin,
and Lead Compounds; Rappoport, Z., Ed.; Wiley & Sons: New York, 2002;
Vol. 2, pp 633-652,
(40) Mu¨ller, T. AdV. Organomet. Chem. 2005, 53, 155.
(41) Kasˇna´, B.; Jambor, R.; Dosta´l, L.; C´ısarova´, I.; Holecek, J. J.
Organomet. Chem. 2006, 691, 1554.
(42) Choi, N.; Lickiss, P. D.; McPartlin, M.; Masangane, P. C.; Veneziani,
G. L. Chem. Commun. 2005, 6023.
(43) Kost, D.; Kalikhman, I. AdV. Organomet. Chem. 2004, 50, 1.
(44) Beckmann, J.; Dakternieks, D.; Duthie, A.; Mitchell, C. Organo-
metallics 2004, 23, 6150.
(45) Kasˇna´, B.; Jambor, R.; Dosta´l, L.; Kola´rova´, L.; C´ısarova´, I.;
Holecek, J. Organometallics 2006, 25, 5300.
(46) Ishihara, K. Sn(II) and Sn(IV) Lewis Acids. In Lewis Acids in
Organic Synthesis; Yamamoto, H., Ed.; Wiley-VCH: Weinheim, 2000; p
395.
Conlusion
In this report we have added a novel representative to the
family of pincer-type ligands, namely, in its protonated form,
the unsymmetrically O,C,S-coordinating ligand {3-t-Bu-5-[P(S)-
Ph2]-C6H3}P(O)(O-i-Pr)2 combining both the hard and soft
donor atoms oxygen and sulfur, respectively. The utility of this
ligand for the synthesis of the intramolecularly coordinated
triorganostannylium salt {4-t-Bu-2-[P(O)(O-i-Pr)2]-6-[P(S)Ph2]-
-
C6H2}SnPh2+PF6 (4) has been demonstrated, and, by MO
calculations, the possibility to control the positive charge and
(47) Durand, S.; Sakamoto, K.; Fukuyama, T.; Orita, A.; Otera, J.; Duthie,
A.; Dakternieks, D.; Schulte, M.; Jurkschat, K. Organometallics 2000, 19,
3220.
(38) Kocher, N.; Henn, J.; Gostevskii, B.; Kost, D.; Kalikhman, I.; Engels,
B.; Stalke, D. J. Am. Chem. Soc. 2004, 126, 5563.

The First O,C,S-Coordinating Pincer-Type Ligand
Table 4. Crystallographic Data for 1-4
Organometallics, Vol. 25, No. 11, 2006 2891
1
2
3
4
formula
fw
cryst syst
cryst size, mm
space group
a, Å
b, Å
c, Å
R, deg
â, deg
γ, deg
V, Å3
C22H22BrPS
429.34
monoclinic
0.25 × 0.25 × 0.23
P21/c
8.9777(2)
9.3145(2)
24.3328(6)
90
93.1687(12)
90
2031.67(8)
4
1.404
2.207
880
C28H36O3P2S
514.57
triclinic
C46H50O3P2SSn‚0.6CH2Cl2
914.51
triclinic
[C40H45O3P2SSn]+[PF6]-
931.42
triclinic
0.20 × 0.20 × 0.18
0.30 × 0.25 × 0.25
0.10 × 0.05 × 0.05
P1h
P1h
P1h
11.2637(10)
14.920(2)
17.289(2)
84.923(4)
89.342(7)
77.652(7)
2827.1(6)
4
12.3286(9)
13.3439(8)
15.2367(8)
113.043(3)
92.551(4)
104.670(3)
2202.2(2)
2
11.1588(5)
11.8227(11)
16.2506(14)
88.244(3)
74.999(5)
86.297(5)
2066.3(2)
2
Z
F
calcd, Mg/m3
1.209
0.254
1096
1.379
0.812
942
1.497
0.849
948
µ, mm-1
F(000)
θ range, deg
3.15 to 27.48
-11ehe11
-12eke12
31ele31
19 432
2.95 to 25.35
-13ehe13
-17eke17
-20ele20
33 673
2.94 to 27.49
-15ehe15
-17eke16
-19ele19
29 671
3.03 to 26.37
-13ehe13
-14eke14
-19ele20
30 785
index ranges
no. of reflns collcd
completeness to θmax,
%
99.7
4641/0.043
2762
268
0.864
99.5
10291/0.034
4815
727
0.775
97.6
9851/0.057
4851
519
0.775
99.3
8399/0.05
4501
487
0.721
no. of indep reflns/Rint
no. of reflns obsd with I > 2σ(I)
no. of refined params
GOF (F2)
R1 (F) (I > 2σ(I))
wR2 (F2) (all data)
(∆/σ)max
0.0317
0.0592
0.001
0.409/-0.441
0.0422
0.0859
< 0.001
0.465/-0.303
0.0455
0.0766
< 0.001
1.216/-0.634
0.0390
0.0610
0.001
0.851/-0.466
largest diff peak/hole, e/Å3
set was previously shown to be appropriate for large organotin
compounds including intra- and intermolecular coordination.34,49-53
In combination with an NBO analysis it provides a qualitative
picture of the bonding situation, although the geometry optimization
of the PdO and PdS bond lengths is inaccurate. Comparing the
results obtained by single-crystal X-ray structure analyses with those
obtained by calculations, systematic errors of about 6% and 8%
are observed for the PdO34 and PdS bond lengths, respectively.
For the calculations shown in Table 4 the O-i-Pr groups of
compound 4 were replaced by OEt groups in order to compare the
results with those recently reported.34 However, the results obtained
orbitals and unoccupied antibonding orbitals and provides atomic
charges that are more reliable than Mulliken charges.
Crystallography. Intensity data for the colorless crystals were
collected on a Nonius KappaCCD diffractometer with graphite-
monochromated Mo KR (0.71073 Å) radiation at 173(1) K. The
data collection covered almost the whole sphere of reciprocal space
with three (1, 4) and four (2, 3) sets at different k-angles with 302
(1), 210 (2), 540 (3), and 237 (4) frames via ω-rotation (∆/ω )
1°) (1, 3, 4) and (∆/ω ) 2°) (2) at two times 10 s (3, 4), 12.5 s (2),
and 60 s (4) per frame. The crystal-to-detector distances were 3.4
cm (1, 2, 4) and 4.0 cm (3). Crystal decays were monitored by
repeating the initial frames at the end of data collection. The data
were not corrected for absorption effects. Analyzing the duplicate
reflections there were no indications for any decay. The structure
was solved by direct methods using SHELXS9756 and successive
difference Fourier syntheses. Refinement applied full-matrix least-
squares methods with SHELXL97.57
The H atoms were placed in geometrically calculated positions
using a riding model with isotropic temperature factors constrained
at 1.2 for non-methyl and at 1.5 for methyl groups times Ueq of the
carrier C atom. In 1 and 2 the coordinates (refx,y,z) of the aryl
hydrogen atoms were refined.
In 2 and 3 isopropoxy groups are disordered over two positions
with occupancies of 0.5 (O(4′′), C(73), C(74), C(75), O(4”′), C(73′),
C(74′), C(75′)) (2) and 0.4 (C(33′)) and 0.6 (C(33) (3). Each
chlorine atom (Cl(1), Cl(2), Cl(1′), Cl(2′), Cl(3), Cl(4), Cl(3′), Cl-
(4′)) of the solvent molecules CH2Cl2 in 3 is disordered over two
positions and was isotropically refined with occupancies of 0.15,
whereas the carbon atoms (C(71), C(81)) were isotropically refined
with occupancies of 0.3.
+
for {4-t-Bu-2-[P(O)(O-i-Pr)2]-6-[P(S)Ph2]-C6H2}SnPh2 do not
show any significant difference. Having these results in mind and
being forced to use the same level of theory for all compounds to
get comparable results, the LANL2DZ basis set was chosen.
Additionally, the wave functions were analyzed by the natural bond
orbital (NBO) method,54,55 a standard option of Gaussian 98. The
NBO analysis explains the strength of coordinative bonds in terms
of donor-acceptor interactions between doubly occupied lone pair
(48) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb,
M. A.; Cheeseman, J. R.; Zakrzewski, V. G.; Montgomery, J. A.; Stratmann,
R. E.; Burant, J. C.; Dapprich, S.; Millian, J. M.; Daniels, A. D.; Kudin, K.
N.; Strain, M. C.; Farkas, O.; Tomasi, J.; Barone, V.; Cossi, M.; Cammi,
R.; Mennucci, B.; Pomelli, C.; Adamo, C.; Clifford, S.; Ochterski, J.;
Petersson, G. A.; Ayala, P. Y.; Cui, Q.; Morokuma, K.; Malick, D. K.;
Rabuck, A. D.; Raghavachari, K.; Foresman, J. B.; Cioslowski, J.; Ortiz, J.
V.; Stefanov, B. B.; Liu, G.; Liashenko, A.; Piskorz, P.; Komaromi, I.;
Bomperts, R.; Martin, R. L.; Fox, D. J.; Keith, T.; Al-Laham, M. A.; Peng,
C. Y.; Nanayakkara, A.; Gonzalez, C.; Challacombe, M.; Gill, P. M. W.;
Johnson, B. G.; Chen, W.; Wong, M. W.; Andres, J. L.; Head-Gordon, M.;
Replogle, E. S.; Pople, J. A. Gaussian 98; Gaussian Inc.: Pittsburgh, 1998.
(49) Buntine, M. A.; Hall, V. J.; Kosovel, F. J.; Tiekink, E. R. T. J.
Phys. Chem. A 1998, 102, 2472.
Atomic scattering factors for neutral atoms and real and
imaginary dispersion terms were taken from International Tables
for X-ray Crystallography.58 The figures were created by SHELX-
TL.59 Crystallographic data are given in Table 4; selected bond
distances and angles, in Table 1 (1, 2) and Table 2 (3, 4).
(50) Obora, Y.; Nakanishi, M.; Tokunaga, M.; Tsuji, Y. J. Org. Chem.
2002, 67, 5835.
(51) Ryner, M.; Finne, A.; Albertsson, A.-C.; Kricheldorf, H. R.
Macromolecules 2001, 34, 7281.
(52) Hu, Y.-H.; Su, M.-D. J. Phys. Chem. A 2003, 107, 4130.
(53) Tani, K.; Kato, S.; Kanda, T.; Inagaki, S. Org. Lett. 2001, 3, 655.
(54) Reed, A. E.; Curtiss, L. A.; Weinhold, F. Chem. ReV. 1988, 88,
899.
(56) Sheldrick, G. M. Acta Crystallogr. A 1990, 46.
(57) Sheldrick, G. M. SHELXL97; University of Go¨ttingen, 1997.
(58) International Tables for X-ray Crystallography; Kluwer Academic
Publishers: Dordrecht, 1992; Vol. C.
(55) King, B. F.; Weinhold, F. J. Phys. Chem. 1995, 103, 333.

2892 Organometallics, Vol. 25, No. 11, 2006
Fischer et al.
(3-Bromo-5-tert-butylphenyl)diphenylphosphane Sulfide, (3-
Br-5-t-Bu-C6H3)P(S)Ph2 (1). 1,3-Dibromo-5-tert-butylbenzene (28.3
g, 98.6 mmol) was dissolved in dry diethyl ether. Under magnetic
stirring at -70 °C, a solution of n-BuLi in n-hexane (63.1 mL, 1.6
M) was added dropwise within 3 h. Progress of the metal-halide
exchange was controlled by GC/MS. The reaction mixture was kept
at -70 °C, and chlorodiphenylphosphane (18.8 mL, 101.5 mmol)
was added dropwise within 45 min. The reaction was warmed to 0
°C, and sulfur (3.3 g, 103.5 mmol) was added in small portions.
After the reaction mixture had been stirred overnight, the precipitate
was filtered and subsequently washed with water, in order to remove
the lithium salts, and diethyl ether. Subsequent recrystallization with
diethyl ether gave 24.5 g (58%) of 1 as a colorless solid; mp 131
°C. Single crystals suitable for X-ray diffraction analysis were
grown by slow evaporation of a hexane/diethyl ether solution.
1H NMR (400.13 MHz, CDCl3): δ 1.23 (s, 9H), 7.44 (m, 4H),
7.51 (m, 2H), 7.56 (ddd, 3J(1H-31P) ) 12.8 Hz, 4J (1H-1H) ) 1.5
0.49 M, 3.46 mmol) in diethyl ether/hexane (2:1) was added
dropwise at -50 °C and under magnetic stirring to a solution of
the arylphosphonic acid diisopropyl ester {3-t-Bu-5-[P(S)Ph2]-
C6H3}P(O)(O-i-Pr)2 (2) (1.48 g, 2.88 mmol) in diethyl ether (35
mL). The reaction mixture was allowed to warm to 0 °C and was
stirred at this temperature for 9 h. Then the reaction mixture was
cooled to -20 °C and triphenyltin chloride (1.33 g, 3.46 mmol)
was added in one portion. The suspension was stirred overnight
while reaching room temperature. The solvent was removed in
vacuo. Dichloromethane and a saturated aqueous KF solution were
added to the residue, and the resulting mixture was stirred for 10
min. The precipitate formed at the interlayer was filtered, and the
organic phase was separated, washed again with aqueous KF
solution, and dried over MgSO4 followed by filtration. The solvent
of the filtrate was evaporated in vacuo, and the residue was purified
by column chromatography (silica, diethyl ether) to give starting
material 2 (0.97 g, 1.88 mmol) and a product-containing fraction.
The latter was purified by crystallization from a hexane/dichlo-
rmethane mixture to give compound 3 (0.24 g, 10%), as its
dichloromethane solvate 3‚CH2Cl2, as colorless crystals with a mp
of 114 °C.
4
Hz, 1.5 Hz, 1H), 7.62 (d, J (1H-1H) ) 1.5 Hz, 1H), 7.72-7.65
(complex pattern, 5H). 13C{1H} NMR (100.63 MHz, CDCl3): δ
30.8 (C(CH3)3), 35.0 (C(CH3)3), 122.7 (d, 3J(13C-31P) ) 16.5 Hz,
C3-Br), 128.0 (d, 2J(13C-31P) ) 11.2 Hz, C2,6), 128.4 (d, 3J(13C-
31P) ) 12.6 Hz, CPh), 131.6 (d, 4J(13C-31P) ) 3.4 Hz, CPh), 131.6
(d, 2J(13C-31P) ) 12.1 Hz, C2,6), 131.7 (d, 4J(13C-31P) ) 2.4 Hz,
C4), 132.0 (d, 2J(13C-31P) ) 10.7 Hz, CPh), 132.3 (d, 1J(13C-31P)
3
1H NMR (400.13 MHz, CD2Cl2): δ 0.83 (d, J(1H-1H) ) 6.3
Hz, 6H; CH(CH3)2), 1.12 (d, 3J(1H-1H) ) 6.3 Hz, 6H; CH(CH3)2),
1.13 (s, 9H; C(CH3)3), 3.94 (d of septet, 2H, 3J(1H-1H) ) 3J(1H-
31P) ) 6.3 Hz, 2H; CH(CH3)2), 5.27 (s, 2H, CH2Cl2), 7.01-7.10
1
) 85.0 Hz, CPh), 135.0 (d, J(13C-31P) ) 82.1 Hz, C1), 153.7 (d,
3J(13C-31P) ) 11.7 Hz, C5-C(CH3)3). 31P{1H} NMR (121.49 MHz,
D2O): δ 44.1 Anal. Calcd for C22H22BrPS: C, 61.5; H, 5.2.
Found: C, 61.1; H, 5.3.
3
(9H, unresolved), 7.60-7.78 (17H, unresolved), 7.85 (d, J(1H-
31P) ) 13.3 Hz, 1H; C3,5). 13C{1H} NMR (100.63 MHz, CDCl3):
δ 23.4 (d, 3J(13C-31P) ) 5.8 Hz; CH(CH3)2), 23.9 (d, 3J(13C-31P)
) 2.9 Hz; CH(CH3)2), 30.6 (s; C(CH3)3), 34.4 (s; C(CH3)3), 70.3
[3-tert-Butyl-5-(diphenylphosphinothioyl)phenyl]phosphon-
ic Acid Di-isopropyl Ester, {3-t-Bu-5-[P(S)Ph2]-C6H3}P(O)(O-
i-Pr)2 (2). (3-Bromo-5-tert-butylphenyl)diphenylphosphane sulfide
(1) (9.59 g, 22.3 mmol) and nickel bromide (0.49 g, 2.23 mmol)
were heated at 165 °C. Phosphoric acid tri-isopropyl ester (6.1 mL,
24.5 mmol) was added dropwise within 30 min and the reaction
mixture was kept at 165 °C for another 30 min, during which it
turned black. The crude product was purified by column chroma-
tography (silica, diethyl ether) to give 6.8 g (59%) of compound 2
as a colorless oil, which solidified after it had been kept overnight
at 0 °C. Single crystals (mp 86 °C) suitable for X-ray diffraction
analysis were grown by slow evaporation of a hexane/dichlo-
romethane solution.
2
4
(d, J(13C-31P) ) 5.8 Hz; CH(CH3)2), 126.6 (s, J(13C-119Sn) )
10.6 Hz, Sn-Cpara), 127.1 (s, 2J(13C-119Sn) ) 54.4 Hz; Sn-Cortho),
128.4 (d, J(13C-31P) ) 12.6 Hz; P-Phortho), 131.0 (d, J(13C-
2
4
31P) ) 2.9 Hz; P-Phpara), 131.7 (d, 3J(13C-31P) ) 10.7 Hz;
P-Phmeta), 132.2 (dd, J(13C-31P) ) 10.7 Hz, J(13C-31P) ) 2.9
2
4
Hz; C3,5), 133.2 (d, 1J(13C-31P) ) 83.6 Hz; C2,6), 135.2 (dd, 2J(13C-
31P) ) 14.8 Hz, J(13C-31P) ) 2.9 Hz; C3,5), 137.1 (s, J(13C-
4
3
119Sn) ) 36.9 Hz; Sn-Cmeta), 148.1 (s; Sn-Cipso), 149.4 (dd,
3J(13C-31P) ) 12.1 Hz, 11.2 Hz; C4), 153.3 (dd, J(13C-31P) )
2
24.3 Hz, 23.3 Hz; C1). C2 and C6 were not assigned unambiguously.
31P{1H} NMR (81.01 MHz, CDCl3): δ 18.5 (d, J(31P-31P) ) 5.2
Hz, J(31P-119Sn ) 27.5 Hz); PdO), 50.0 (d, J(31P-31P) ) 5.2 Hz,
J(31P-119Sn ) 56.1 Hz); PdS). 119Sn{1H} NMR (111.92 MHz,
CDCl3): δ -194 (dd, J(119Sn-31P) ) 56 Hz, 28 Hz). IR (KBr):
ν˜(PdO) 1241 cm-1. Anal. Calcd for C46H50O3P2SSn‚CH2Cl2: C,
59.5; H, 5.5. Found: C, 59.5; H, 5.6.
3
1H NMR (400.13 MHz, CDCl3): δ 1.12 (d, J(1H-1H) ) 6.3
Hz, 6H, CH(CH3)2), 1.28 (d, 3J(1H-1H) ) 6.3 Hz, 6H; CH(CH3)2),
1.28 (s, 9H, C(CH3)3), 4.61 (d, septet, 3J(1H-1H) ) 3J(1H-31P) )
6.3 Hz, 2H; CH(CH3)2), 7.43 (m, 4H; HPh), 7.50 (m, 2H; HPh-para),
7.64-7.75 (complex pattern, 5H; HPh and H6), 7.95 (d, 3J(1H-31P)
[4-tert-Butyl-2-(di-isopropoxyphosphoryl)-6-(diphenylphos-
phinothioyl)phenyl]diphenylstannylium Hexafluorophosphate,
{4-t-Bu-2-[P(O)(O-i-Pr)2]-6-[P(S)Ph2]-C6H2}SnPh2+PF6- (4). To
a solution of 3 (46.0 mg, 0.05 mmol) in C2D2Cl4 (1.5 mL) was
added triphenylmethyl hexafluorophosphate (19.4 mg, 0.05 mmol).
After the reaction mixture had been stirred at room temperature
overnight the solvent was removed in vacuo and the crude product
was dissolved in dichloromethane. Slow evaporation of the solvent
first gave crystals of tetraphenylmethane. After these crystals had
been filtered slow evaporation of the solvent was continued to
provide 44 mg (94%) of compound 4 as colorless crystals (mp 160
°C) suitable for X-ray diffraction analysis.
3
) 14.0 Hz, 1H; H2,4), 8.04 (d, J(1H-31P) ) 14.6 Hz, 1H; H2,4).
3
13C{1H} NMR (100.63 MHz, CDCl3): δ 23.5 (d, J(13C-31P) )
3
4.9 Hz; CH(CH3)2), 23.8 (d, J(13C-31P) ) 3.9 Hz; CH(CH3)2),
2
30.9 (s, C(CH3)3), 35.1 (s, C(CH3)3), 70.8 (d, J(13C-31P) ) 5.8
Hz; CH(CH3)2), 128.4 (d, 3J(13C-31P) ) 12.6 Hz; CPh), 130.4 (dd,
3
1J(13C-31P) ) 188.0 Hz, J(13C-31P) ) 11.7 Hz; C1-P), 131.5
4
2
(d, J(13C-31P) ) 2.9 Hz; CPh-para), 131.9 (dd, J(13C-31P) ) 10.7
Hz, J(13C-31P) ) 2.9 Hz; C2,4), 132.2 (dd, J(13C-31P) ) 10.7
4
2
Hz, 10.7 Hz; C6), 132.2 (d, J(13C-31P) ) 10.7 Hz; CPh), 133.1
2
(dd, J(13C-31P) ) 11.7 Hz, J(13C-31P) ) 2.9 Hz; C2,4), 133.3
(dd, 1J(13C-31P) ) 85.6 Hz, 3J(13C-31P) ) 14.5 Hz; C5-P), 151.7
(dd, 3J(13C-31P) ) 13.6 Hz, 11.2 Hz; C3-C(CH3)3). 31P{1H} NMR
(81.01 MHz, CDCl3): δ 16.3 (d, J(31P-31P) ) 5.9 Hz; PdO), 44.6
2
4
3
1H NMR (300.13 MHz, CDCl3): δ 1.11 (d, J(1H-1H) ) 6.2
Hz, 6H; CH(CH3)2), 1.23 (d, 3J(1H-1H) ) 6.3 Hz, 6H; CH(CH3)2),
(d, J(31P-31P) ) 5.9 Hz; PdS). IR (KBr): ν˜(PdO) 1249 cm-1
.
3
3
1.31 (s, 9H; C(CH3)3), 4.48 (d, septet, J(1H-1H) ) JPOCH(1H-
31P) ) 6.2 Hz, 2H; CH(CH3)2), 7.34-7.44 (6H, unresolved), 7.60-
7.78 (14H, unresolved), 7.91 (d, 3J(1H-31P) ) 11.3 Hz, 1H; H3,5),
Anal. Calcd for C28H36O3P2S: C, 65.4; H, 7.1. Found: C, 65.1; H,
6.9.
[5-tert-Butyl-3-(diphenylphosphinothioyl)-2-(triphenylstannyl)-
phenyl]phosphonic Acid Di-isopropyl Ester, {5-t-Bu-3-[P(S)Ph2]-
2-(SnPh3)-C6H2}P(O)(Oi-Pr)2 (3). A solution of i-Pr2NLi (6.8 mL,
3
8.05 (d, J(1H-31P) ) 13.5 Hz, 1H; H3,5). 13C{1H} NMR (100.63
MHz, CDCl3): δ 23.5 (d, 3J(13C-31P) ) 5.8 Hz; CH(CH3)2), 23.6
(d, 3J(13C-31P) ) 5.3 Hz; CH(CH3)2), 29.7 (d, 3J(13C-31P) ) 5.3
Hz; C(CH3)3), 30.8 (s; C(CH3)3), 36.7 (s; C(CH3)3), 75.8 (d, 2J(13C-
31P) ) 6.3 Hz; CH(CH3)2), 126.2 (d, 1J(13C-31P) ) 87.5 Hz;
(59) Sheldrick, G. M. SHELXTL. Release 5.1 Software Reference Manual;
Bruker AXS, Inc.: Madison, WI, 1997.

The First O,C,S-Coordinating Pincer-Type Ligand
Organometallics, Vol. 25, No. 11, 2006 2893
2
P-Phipso), 129.2 (s, J(13C-119Sn) ) 76.5 Hz; Sn-Cortho), 130.0
at 65 °C for 6 h the solution was characterized by NMR
spectroscopy. Subsequently, the solvent was removed in vacuo, and
the residue was investigated by electrospray mass spectrometry.
Attempts at isolating analytically pure compound 5 failed.
31P{1H} NMR (81.02 MHz, C2D2Cl4): δ 15.2 (d, ν1/2 1.6 Hz,
J(31P-31P) ) 2.0 Hz, PdO), 51.4 (d, ν1/2 1.4 Hz, J(31P-31P) )
2.0 Hz, J(31P-119Sn) ) 64.8 Hz; PdS). 119Sn{1H} NMR (111.92
MHz, CDCl3): δ -168 (d, ν1/2 18 Hz, J(31P-119Sn) ) 65 Hz).
ESI-MS: m/z ) 745.1 ([5-H]+ corresponding to natural isotope
distribution).
(d, J(13C-31P) ) 13.6 Hz; P-Phortho), 130.5 (s, J(13C-119Sn) )
2
4
15.5 Hz; Sn-Cpara), 132.2 (dd, J(13C-31P) ) 12.6 Hz, J(13C-
2
4
31P) ) 2.9 Hz; C3,5), 132.5 (d, 2J(13C-31P) ) 11.2 Hz; P-Phmeta),
133.0 (d, J(13C-31P) ) 70.9 Hz; C2,6), 133.2 (d, J(13C-31P) )
1
1
87.5 Hz; C2,6), 134.4 (d, J(13C-31P) ) 2.9 Hz; P-Phpara), 134.6
4
(dd, 2J(13C-31P) ) 14.6 Hz, 4J(13C-31P) ) 2.9 Hz; C3,5), 135.6 (s,
3J(13C-119Sn) ) 52.5 Hz; Sn-Cmeta), 138.8 (d, 4J(13C-31P) ) 2.9
Hz; Sn-Cipso), 151.3 (dd, J(13C-31P) ) 27.2 Hz, 22.4 Hz; C1),
2
156.6 (dd, J(13C-31P) ) 12.6 Hz, 9.7 Hz, C4). 31P{1H} NMR
3
(121.49 MHz, CDCl3): δ -143.2 (sept, (1J(31P-19F) ) 712 Hz);
PF6-), 25.0 (d, ν1/2 5 Hz, J(31P-31P) ) 3.0 Hz; PdO), 54.8 (d,
J(31P-31P) ) 3.0 Hz, (J(31P-119Sn) ) 37.1 Hz); PdS). 119Sn{1H}
NMR (111.92 MHz, CDCl3): δ -132 (d, ν1/2 9 Hz, J(119Sn-31P)
) 37 Hz). IR (KBr): ν˜(PdO) 1155 cm-1. Anal. Calcd for
C40H45O3F6P3SSn: C, 61.1; H, 5.9. Found: C, 60.4; H, 5.4.
In Situ Generation of 6-tert-Butyl-4-(diphenylphosphino-
thioyl)-1-isopropoxy-1-oxo-3,3-diphenyl-2,1,3-benzoxaphospha-
stannole (5). To a solution of 4 (44 mg, 0.047 mmol) in C2D2Cl4
(1.5 mL) was added tetraphenylphosphonium bromide, PPh4+Br-
(20.9 mg, 0.05 mmol). After the reaction mixure had been stirred
Acknowledgment. We thank the Deutsche Forschungsge-
meinschaft for financial support.
Supporting Information Available: For compounds 1-4
details of structure determination, atomic coordinates, bond lengths
and bond angles, and displacement parameters in cif format. This
material is available free of charge via the Internet at http://
pubs.acs.org.
OM0600590