Dichlorostannylene complexes of group 10 metals, a unique bonding mode stabilized by bridging 2-pyridyldiphenylphosphine ligands

Article abstract of DOI:10.1039/b924783c

The reaction of tin dichloride with catalytically-relevant group 10 metal precursors [M(Cl)(X)(2-PyPPh₂)₂] (M = Ni, Pd, Pt; 2-PyPPh₂ = 2-pyridyldiphenylphosphine; X = Cl, Me) provides easy access to unprecedented cationic dichlorostannylene complexes [M(X)(2-PyPPh ₂)₂(SnCl₂)]⁺ where the M-Sn bond is bridged by two head-to-head coordinated 2-PyPPh₂ ligands. The formation of such species instead of the classical neutral trichlorostannyl derivatives [M(X)(SnCl₃)(2-PyPPh₂)₂] offers a new insight on the specific effect of the SnCl₂ cocatalyst in group 10 metal catalyzed transformations. The Royal Society of Chemistry 2010.

Full text of DOI:10.1039/b924783c

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PAPER
www.rsc.org/dalton | Dalton Transactions
Dichlorostannylene complexes of group 10 metals, a unique bonding mode
stabilized by bridging 2-pyridyldiphenylphosphine ligands†
Yves Cabon,a Henk Kleijn,a Maxime A. Siegler,b Anthony L. Spek,b Robertus J. M. Klein Gebbinka and
Berth-Jan Deelman*a,c
Received 7th September 2009, Accepted 1st December 2009
First published as an Advance Article on the web 20th January 2010
DOI: 10.1039/b924783c
The reaction of tin dichloride with catalytically-relevant group 10 metal precursors
[M(Cl)(X)(2-PyPPh2)2] (M = Ni, Pd, Pt; 2-PyPPh2 = 2-pyridyldiphenylphosphine;
X = Cl, Me) provides easy access to unprecedented cationic dichlorostannylene complexes
[M(X)(2-PyPPh2)2(SnCl2)]+ where the M–Sn bond is bridged by two head-to-head coordinated
2-PyPPh2 ligands. The formation of such species instead of the classical neutral trichlorostannyl
derivatives [M(X)(SnCl3)(2-PyPPh2)2] offers a new insight on the specific effect of the SnCl2 cocatalyst
in group 10 metal catalyzed transformations.
Introduction
Results and discussion
Tin dichloride is an important cocatalyst in various group 10 metal
catalyzed reactions1 such as hydroformylation,2 hydrogenation,3
or isomerisation4 and, more recently, hydrogen-mediated reductive
couplings.5 In all of these reactions, the insertion of SnCl2 into
a M–Cl bond (M = Ni, Pd, Pt) is postulated to lead to the
formation of a trichlorostannyl ligand, i.e. to complexes of general
formula [M-SnCl3].
The weak coordination of the [SnCl3]- anion and/or its trans-
labilising effect have been used to explain the importance of SnCl2
as a cocatalyst, even if its exact role is still unclear.6,7 The first
hypothesis does not appear to be sufficient as some analogous
complexes containing other weakly coordinating anions show
a lack of reactivity in hydroformylation8 or a temperature-
dependence of the regioselectivity9 that suggests a different
mechanism for the SnCl2 additive. The second suggestion could
also be questioned, as weakly coordinated ligands are usually
associated with a small trans-effect.6
Synthetic aspects
A previous study by Jain and coworkers showed that trans-
[Pt(Cl)(Me)(2-PyPPh2)2] reacts in dichloromethane (DCM) with
an excess of tin dichloride to form a new complex that was
identified as being neutral trans-[Pt(Me)(SnCl3)(2-PyPPh2)2] on
the basis of 31P and 1H NMR data,11 despite the observation
of an extraordinary downfield-shifted 31P NMR signal and the
remarkable stability of the complex in DCM.12 Reproducing this
experiment, we found that the ESI-MS data for the crude solution
(m/z = +926.00) was not consistent with this formula but indicates
the formation of a [Pt(Me)(2-PyPPh2)2(SnCl2)]+ cation.
In order to find out if this cation is present in solution or only
formed during the ionisation process in the mass spectrometer,
we attempted its selective synthesis (Scheme 1). First the chlo-
ride atom of trans-[Pt(Cl)(Me)(2-PyPPh2)2] was abstracted using
AgBF4 inDCMtogive [Pt(Me)(k -2-PyPPh2)(k -2-PyPPh2)][BF4],
whose formation could be followed by 31P NMR.13 Then, after
removal of the resulting AgCl precipitate by filtration, SnCl2 was
1
2
As the catalytically-relevant 2-PyPPh2 ligand is known to
2
favor the formation of bimetallic species through k -(P,N)
coordination,10 we decided to study the interaction of SnCl2 with
group 10 metal complexes containing this ligand, which resulted
in the discovery of a unique M–Sn bonding mode.
aUtrecht University, Faculty of Science, Debye Institute for Nanomaterials
Science, Chemical Biology & Organic Chemistry, Padualaan 8, 3584 CH,
Utrecht, The Netherlands. E-mail: y.h.m.cabon@uu.nl
bUtrecht University, Faculty of Science, Bijvoet Center for Biomolecular
Research, Crystal and Structural Chemistry, Padualaan 8, 3584 CH,
Utrecht, The Netherlands. E-mail: a.l.spek@uu.nl; Fax: +31 302533940;
Tel: +31 302523315
cARKEMA Vlissingen B.V., P.O.Box 70, 4380 AB, Vlissingen, The
Netherlands. E-mail: b.j.deelman@uu.nl; Fax: +31 113612984; Tel: +31
113617225
† Electronic supplementary information (ESI) available: NMR spectra
for [1][BF4] (1H, 13C, 19F, 31P and 195Pt), [2][BF4] (1H and 31P), [3][BF4]
(31P), [4][BF4] (31P) and [5][BF4] (31P). ESI-HRMS and IR spectra of
all five compounds. Cif file for [1][BF4]. Computational details. CCDC
reference number 746884. For ESI and crystallographic data in CIF or
other electronic format see DOI: 10.1039/b924783c
Scheme 1 Reagents and conditions: i) Ag[BF4] (1 equiv.), DCM, RT,
30 min. ii) SnCl2 (1 equiv.), DCM, RT, 1 h. i + ii 85%
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added to the reaction medium. The white solid isolated after
removing DCM under vacuum and washing with THF exhibits
1
31P and H NMR spectra identical to those of Jain’s compound.
Further characterization by 13C, 19F and 195Pt NMR as well as
ESI-HRMS and IR spectroscopy is consistent with the formation
of [Pt(Me)(2-PyPPh2)2(SnCl2)][BF4], [1][BF4] (85%). We therefore
suggest here that the excess of SnCl2 present in Jain’s synthesis
may have acted as a chloride acceptor, leading to the formation of
[1][SnCl3].
With no decomposition observed over a period of 5 days in a
DCM solution in air, the structure of [1]+ is robust and its (2-
PyPPh2)2(m-SnCl2) moiety may be envisioned as a self-assembled
pincer ligand for platinum.
The synthesis and isolation of [1][BF4] could also be achieved
in a straightforward way by mixing [Pt(Cl)(Me)(cod)], 2-PyPPh2
(2 equiv.), SnCl2 (1.1 equiv.) and [NBu4][BF4] (3 equiv.) in THF
(Scheme 2). After 1 h of stirring, the product, present as a white
precipitate, is directly recovered pure and in high yield by filtration
and washing with THF.
Fig. 1 Molecular structure of trans-[Pt(Me)(SnCl2)(2-PyPPh2)2][BF4],
[1][BF4] ([BF4]- anion omitted for clarity. Selected bond lengths (A)
˚
and angles (◦): Pt(1)–Sn(1) 2.5166(6); Pt(1)–P(1) 2.2683(11); Pt(1)–P(2)
2.2706(11); Pt(1)–C(1) 2.136(5); Sn(1)–Cl(1) 2.3524(12); Sn(1)–Cl(2)
2.3569(12); Sn(1)–N(1) 2.347(3); Sn(1)–N(2) 2.348(3); C(1)–Pt(1)–P(1)
89.64(11); P(1)–Pt(1)–Sn(1) 90.19(3); Sn(1)–Pt(1)–P(2) 90.69(3);
P(2)–Pt(1)–C(1) 89.50(11); Pt(1)–Sn(1)–Cl(1) 129.58(3); Cl(1)–Sn(1)–Cl(2)
101.96(4); Cl(2)–Sn(1)–Pt(1) 128.46(3); N(1)–Sn(1)–N(2) 168.98(12).
The closest analogy is with a neutral palladium(II) complex re-
ported by Jambor and coworkers that contains the arylstannylene
Scheme 2 Reagents and conditions: i) 2-PyPPh2 (2 equiv.), SnCl2
(1.1 equiv.), [NBu4][BF4] (3 equiv.), THF, RT, 1 h.
[2,6-(Me2NCH2)2C6H3]SnCl.14 The Pt–Sn bond (2.5166(6) A) is
˚
short compared to known Pt(II)–SnCl3 species but comparable to
the few known Pt(0)–stannylene complexes none of which contain
a Pt–C bond.15 The Pt–C bond (2,136(5) A) is long compared to
˚
other Pt(II)–Me complexes,15 indicating a strong trans- influence
of the SnCl2 ligand in this configuration. The participation of
the phosphorus atoms in five-membered rings may explain their
downfield chemical shift in the 31P NMR spectrum.16
Interestingly this method is not limited to M = Pt. Per-
forming the same reaction, but with the palladium precursor
[Pd(Cl)(Me)(cod)], led to a pure compound that was characterized
by 1H, 19F and 31P NMR, ESI-HRMS and IR spectroscopy
(Scheme 2). Although the 13C NMR spectrum could not be
obtained due to poor solubility, the compound could be identified
as [Pd(Me)(2-PyPPh2)2(SnCl2)][BF4], [2][BF4], by analogy with the
NMR data of the platinum compound [1][BF4].
Moreover, reacting the chloride precursors [PtCl2(SMe2)2],
[PdCl2(cod)] or [NiCl2(DME)] in THF under the same conditions
led to three new dichlorostannylene adducts (Scheme 2). The very
1
low solubilities severely hampered H and 13C NMR analyses of
these products but on the basis of their 31P NMR, ESI-HRMS
and IR spectroscopic data, that are analogous to the methyl
derivatives [1][BF4] and [2][BF4], they were assigned the general
formula [M(Cl)(2-PyPPh2)2(SnCl2)][BF4].
Structural study and bonding mode of complex [1][BF4]
The structure of [1][BF4] was confirmed by X-ray crystallography
(Fig. 1). The cationic square-planar platinum complex exhibits a
unique Pt–SnCl2 bond bridged by two head-to-head coordinated
2-PyPPh2 ligands. This bonding behaviour is without precedent.
Fig. 2 Molecular orbitals HOMO-17 (left) and HOMO-16 (right) of the
calculated trans-[Pt(Me)(SnCl2)(2-PyPH2)2]+ cation, showing the bonding
mode of the SnCl2 moiety in [1]+.
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The intramolecular donation of the nitrogen lone pairs of
the pyridylphosphine ligands to the tin atom, leading to a pen-
tacoordinated trigonal-bipyramidal geometry, seems to stabilize
the stannylene-type coordination of the SnCl2 moiety on the
platinum(II) centre.14,17 This was confirmed by DFT calculations18
on a model of [1]+ in which the phenyl groups of the ligands
are replaced by H atoms. The HOMO-17 orbital describes the
donation of the SnCl2 fragment to the platinum centre and the
HOMO-16 orbital exhibits the donation of the nitrogen lone-pairs
in the empty p orbital of the SnCl2 moiety (Fig. 2).
(1H, 13C with calibration using the (residual) solvent signal),
external H3PO4 85% in water (31P), external K2[PtCl6] 1 M in
water (195Pt) and external neat CFCl3 (19F). High-Resolution Mass
Spectra (HRMS) have been recorded on a Waters LCT Premier
XE Micromass spectrometer using the ElectroSpray Ionization
technique (ESI). IR spectra in the solid state have been recorded
on a Perkin Elmer Spectrum One FT-IR spectrometer.
trans-[Pt(Me)(SnCl2)(2-PyPPh2)2][BF4], [1][BF4]
Method 1. trans-[Pt(Me)Cl(2-PyPPh2)2] (100 mg, 0,13 mmol)
was dissolved in 5 mL of DCM. Ag[BF4] (25.3 mg, 0.13 mmol) was
then added as a solid and the reaction mixture was stirred at room
Conclusions
R
temperature for 30 min. The reaction was filtered over Celiteꢀ
Until now, the reaction of SnCl2 with the M–Cl bond (M = Pt,
Pd, Ni) was thought to lead to the formation of a trichlorostannyl
ligand, i.e. to complexes of general formula [M-SnCl3].
The weak coordination of the [SnCl3]- anion has often been
used to explain the importance of the SnCl2 cocatalyst allowing
the creation of a vacant site on the catalyst, i.e. the formation
of [M]+[SnCl3]- ion pairs. Despite its relevance in many cases,
this hypothesis is not sufficient as, in some reactions, the use of
other weakly coordinating ligands, such as borate anions, led to
significantly different results.8,9
Another explanation often found in the literature is that the
[SnCl3]- ligand has a strong trans-labilising effect in [M-SnCl3]
complexes. But this statement could be questioned as it appears to
be in contradiction with a weakly coordinating character for the
[SnCl3]- ligand.6
Thus, our observation that SnCl2 upon reaction with M–Cl
species can also bind to the metal centre in a dichlorostannylene-
type fashion showing a strong trans-influence is of high interest. We
believe that the (transient) formation under catalytic conditions
of [M-SnCl2]+[Cl]- or [M-SnCl2]+[SnCl3]- species19 should be
considered, especially when stabilisation of the dichlorostannylene
moiety by intramolecular donor groups or coordinating solvents
is possible. Their presence may help to understand the specific and
unique cocatalytic effect of SnCl2 in some transformations.
The reactivity and catalytic activity of these new dichlorostan-
nylene complexes of group 10 metals are currently under investi-
gation.
1
to remove AgCl, leading to a colorless solution of [Pt(Me)(k -2-
2
PyPPh2)(k -2-PyPPh2][BF4] (not isolated but 31P NMR shows two
signals at d +19.3 and -17.9 ppm as described in the literature).
SnCl2 (25.0 mg, 0.13 mmol) was added as a solid to this solution
and stirred for 30 min. Traces of SnCl2 were then removed by
R
filtration over Celiteꢀ. The solvent of the colorless solution was
removed in vacuum leading to a white solid that was washed with
THF (2 ¥ 5 mL). The final product was obtained as a white solid.
Yield: 112 mg (0.11 mmol, 85%). The complex was recrystallized
by vapor diffusion of Et2O on a saturated DCM solution leading to
single crystals that were suitable for X-ray structure determination.
Method 2. [Pt(Me)(Cl)(cod)] (50.0 mg, 0.14 mmol), 2-PyPPh2
(74.5 mg, 0.28 mmol), SnCl2 (29.5 mg, 0.15 mmol) and [NBu4][BF4]
(186 mg, 0.42 mmol) were dissolved in 10 mL of THF. The reaction
was stirred for 1 h during which a white precipitate appeared. The
white precipitate was recovered by filtration, washed with THF (2 ¥
5 mL) and dried in vacuum. Yield: 103 mg (0.10 mmol, 72%). 1H
NMR (CD2Cl2, 298 K): d +9.31 [m, 2H], +8.03 [m, 2H], +7.76 [m,
4H], +7.41 [m, 20H], +0.71 [t, Pt-Me, 2JHP 6.5 Hz, 2JHPt 71.8 Hz].
13C NMR (CD2Cl2, 298 K): d +149.21 [m], +141.94 [m], +134.21
[m], +132.74 [s], +131.37 [m], +129.54 [m], +129.03 [s], +126.60
1
[m], +2.06 [s, CH3, J13C-195Pt could not be detected]. 19F NMR
(CD2Cl2, 298 K): d -153.3 [s, BF4]. 31P NMR (CD2Cl2, 298 K):
d +66.8 [s, 1JPPt 2873 Hz, 2JPSn 233 Hz]. 195Pt NMR (CD2Cl2, 298
K): d -5463.6 [t, 1JPtP 2873 Hz]. ESI-HRMS (in DCM): calculated
for [1]+ 926.0004, found 925.9973 with the correct isotope pattern.
IR (solid, cm-1): 3065, 1584, 1481, 1460, 1434, 1312, 1286, 1182,
1165, 1133, 1097, 1053, 1017, 998, 919, 852, 770, 748, 723, 689.
Experimental
All operations were performed in dry degassed solvents
under a nitrogen atmosphere using standard Schlenk and
cannula techniques. 2-Pyridyldiphenylphoshine, silver tetraflu-
oroborate and anhydrous tin dichloride were purchased
from Sigma-Aldrich. Metallic precursors trans-[Pt(Cl)(Me)(2-
PyPPh2)2], [Pt(Cl)(Me)(cod)], [PtCl2(SMe2)2], [Pd(Cl)(Me)(cod)],
[PdCl2(cod)] and [NiCl2(dme)] were prepared according to classi-
cal literature procedures.
Several attempts to obtain accurate elemental analyses data for
the new compounds failed despite recrystallization of the com-
pounds before analysis (probably because digestion is hampered
by the high hetero-atom content and the ionic nature of these
compounds) but high-resolution mass spectra were obtained◦to
compensate for this. NMR spectra have been recorded at 25 C
on a Varian Oxford 300 MHz or a Varian Oxford AS 400 MHz
NMR spectrometer. Chemical shifts are reported relative to SiMe4
trans-[Pd(Me)(SnCl2)(2-PyPPh2)2][BF4], [2][BF4]
[Pd(Me)(Cl)(cod)] (50.0 mg, 0.19 mmol), 2-PyPh2 (99.3 mg,
0.38 mmol), SnCl2 (39.3 mg, 0.21 mmol) and [NBu4][BF4] (148 mg,
0.57 mmol) were dissolved in 10 mL of THF. The reaction mixture
was stirred for 1 h during which a white precipitate appeared. The
white precipitate was recovered by filtration, washed with THF
(2 ¥ 5 mL) and dried in vacuum. Yield: 141 mg (0.15 mmol, 81%).
1H NMR (CD2Cl2, 298 K): d +9.01 [m, 2H], +8.08 [m, 2H], +7.85
[m, 2H], +7.59 [m, 2H], +7.54 to +7.39 [m, 20H], +1.16 [t, Pd-Me,
2JHP 6.5 Hz]. 19F NMR (CD2Cl2, 298 K): d -153.3 [s, BF4] ppm.
2
31P NMR (CD2Cl2, 298 K) d +63.9 [s, JPSn 241Hz]. ESI-HRMS
(in DCM): calculated for [2]+ 836.9391, found 836.9391 with the
right isotope pattern. IR (solid, cm-1) 3060, 1583, 1482, 1463, 1434,
1310, 1283, 1182, 1169, 1134, 1097, 1054, 1008, 999, 917, 850, 765,
751, 723, 688.
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trans-[Pt(Cl)(SnCl2)(2-PyPPh2)2][BF4], [3][BF4]
6-31G* for H, C, N, P and Cl atoms and LANL2DZ for Sn
and Pt atoms. The geometry was optimized until it met the
usual convergence criteria and was found to match the molecular
structure of [1][BF4] determined by X-ray crystallography. A
frequency calculation found no imaginary frequencies.
[Pt(SMe2)2Cl2] (50.0 mg, 0,13 mmol), 2-PyPPh2 (67.5 mg,
0,26 mmol), SnCl2 (26.7 mg, 0.14 mmol) and [NBu4][BF4] (127 mg,
0.39 mmol) were dissolved in 10 mL of THF. The reaction was
stirred for 1 h during which a white precipitate appeared. The
white precipitate was recovered by filtration, washed with THF
(2 ¥ 5 mL) and dried in vacuum. Yield: 83,4 mg (0,08 mmol, 63%).
31P NMR (CD2Cl2, 298 K): d +78.7 [s, 1JPPt 2917 Hz]. ESI-HRMS
(in DCM): calculated for [3]+ 945.9458, found 945.9528 with the
right isotope pattern. IR (solid, cm-1) 3099, 3062, 2971, 2867, 1585,
1481, 1462, 1434, 1311, 1286, 1182, 1170, 1134, 1097, 1059, 1011,
998, 918, 852, 768, 752, 722, 689.
Acknowledgements
Dr Y. Cabon gratefully acknowledges support from the French
Government and ARKEMA for a postdoctoral VIS fellowship.
We thank Prof. G. van Koten (Utrecht University) for valuable
discussions.
Notes and references
trans-[Pd(Cl)(SnCl2)(2-PyPPh2)2][BF4], [4][BF4]
1 For a review see, M. S. Holt, W. L. Wilson and J. H. Nelson, Chem.
Rev., 1989, 89, 11.
[Pd(cod)Cl2] (50.0 mg, 0.17 mmol), 2-PyPPh2 (92.2 mg,
0.35 mmol), SnCl2 (36.5 mg, 0.19 mmol) and [NBu4][BF4] (173 mg,
0.52 mmol) were dissolved in 10 mL of THF. The reaction was
stirred for 1 h during which a white precipitate appeared. The
white precipitate was recovered by filtration, washed with THF
(2 ¥ 5 mL) and dried in vacuum. Yield: 124 mg (0.13 mmol,
75%). 31P NMR (CD2Cl2, 298 K): d +76.3 [s] ppm. ESI-HRMS
(in DCM): calculated for [4]+ 856.8845, found 856.8929 with the
right isotope pattern. IR (solid, cm-1): 3100, 3059, 2972, 2869,
1584, 1482, 1460, 1434, 1312, 1284, 1182, 1172, 1134, 1096, 1059,
1010, 999, 904, 851, 768, 751, 722, 689.
2 I. Schwager, and J. F. Knifton, Ger. Pat. 2322751, 1973; C.-Y. Hsu
and M. Orchin, J. Am. Chem. Soc., 1975, 97, 3553; I. Schwager and
J. F. Knifton, J. Catal., 1976, 45, 256. For recent examples see, R. van
Duren, J. I. van der Vlugt, H. Kooijman, A. L. Spek and D. Vogt,
Dalton Trans., 2007, 1053; E. Robe, C. Hegedus, J. Bakos, Y. Coppel,
J.-C. Daran and M. Gouygou, Inorg. Chim. Acta, 2008, 361, 1861; G.
Petocz, G. Rangits, M. Shaw, H. de Bod, D. B. G. Williams and L.
Kollar, J. Organomet. Chem., 2009, 694, 219.
3 R. D. Cramer, E. L. Jenner, R. V. Lindsey, Jr. and U. G. Stolberg,
J. Am. Chem. Soc., 1963, 85, 1691; L. P. Van’t Hof and B. G. Linsen,
J. Catal., 1967, 7, 295; L. Jardine and F. J. McQuillin, Tetrahedron
Lett., 1966, 7(40), 4871; D. H. Goldsworthy, F. R. Hartley and S. G.
Murray, J. Mol. Catal., 1983, 19, 269; J. C. Bailar, Jr. and H. Itatani,
J. Am. Chem. Soc., 1967, 89, 1592; J. C. Bailar, Jr. and H. Itatani, Inorg.
Chem., 1965, 4, 1618; K. Kushi, H. Kanai, K. Tamara and S. Yoshida,
Chem. Lett., 1972, 7, 539. Hydrogenation also occurs as a side reaction
in hydroformylation, S. C. Tang and L. Kim, J. Mol. Catal., 1982, 14,
231; I. Toth, C. J. Elsevier, J. G. de Vries, J. Bakos, W. J. J. Smeets and
A. L. Spek, J. Organomet. Chem., 1997, 540, 15; J. I. van der Vlugt,
R. van Duren, G. D. Batema, R. den Heeten, A. Meetsma, J. Fraanje,
K. Goubitz, P. C. J. Kamer, P. W. N. M. van Leeuwen and D. Vogt,
Organometallics, 2005, 24, 5377.
4 H. A. Tayim and J. C. Bailar, Jr., J. Am. Chem. Soc., 1967, 89, 3420.
5 I. G. Jung, J. Seo, S. I. Lee, S. Y. Choi and Y. K. Chung, Organometallics,
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1, 64.
7 A. Scrivanti, A. Berton, L. Tonioli and C. Botteghi, J. Organomet.
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X. Solans, Organometallics, 1991, 10, 4036; W. Rocha and W. B. de
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8 H. J. Ruegg, P. S. Pregosin, A. Scrivanti, L. Toniolo and C. Botteghi,
J. Organomet. Chem., 1986, 316, 233.
trans-[Ni(Cl)(SnCl2)(2-PyPPh2)2][BF4], [5][BF4]
[Ni(DME)Cl2] (40.0 mg, 0.18 mmol), 2-PyPPh2 (95.9 mg,
0.36 mmol), SnCl2 (38.0 mg, 0,20 mmol) and [NBu4][BF4] (180 mg,
0.55 mmol) were dissolved in 10 mL of THF. The reaction was
stirred for 1 h during which a white precipitate appeared. The
white precipitate was recovered by filtration, washed with THF
(2 ¥ 5 mL) and dried in vacuum. Yield: 0.108 g (0,12 mmol, 66%).
31P NMR (CD2Cl2, 298 K): d +57.3 [s]. ESI-HRMS (in DCM):
calculated for [5]+ 808.9163, found 808.9136 with the right isotope
pattern. IR (solid, cm-1) 3098, 3059, 2972, 2867, 1585, 1481, 1462,
1434, 1311, 1286, 1182, 1170, 1134, 1097, 1054, 1011, 998, 918,
852, 769, 752, 723, 689.
Crystallography
Crystal data for [1][BF4]. [C35H31Cl2N2P2PtSn]+[BF4]-, M =
9 L. Janosi, T. Kegl and L. Kollar, J. Organomet. Chem., 2008, 693, 1127.
10 For reviews see, G. Newkome, Chem. Rev., 1993, 93, 2067; Z.-Z. Zhang
and H. Cheng, Coord. Chem. Rev., 1996, 147, 1; P. Espinet and K.
Soulantica, Coord. Chem. Rev., 1999, 193, 499.
11 V. K. Jain, V. S. Jakkal and R. Bohra, J. Organomet. Chem., 1990, 389,
417.
1013.08, orthorhombic, space group Pccn (No. 56), a = 16.6611(3),
3
˚
˚
b = 20.3193(7), c = 21.1892(2) A, U = 7173.4(3) A . Z =
8, T = 110 K. Dc = 1.876 g cm-3, F(000) = 3904. Graphite
˚
monochromated Mo-Ka radiation l = 0.71073 A. q(max) =
27.5◦. 61256 were measured of which 8246 unique (R(int) = 0.035).
The structure was solved with DIRDIF. SHELXL refinement with
521 parameters converged to R = 0.0306 (5980 reflections with
12 Insertion of SnCl2 into a Pt–Cl bond is normally associated with a
shielding of the phosphorus nuclei in 31P NMR (see ref. 6 and 11) and is
reversible. Therefore Pt-(SnCl3) complexes are usually unstable in DCM
due to the solubility-driven elimination of SnCl2, see: D. Fernandez,
M. I. Garcia-Seijo, T. Kegl, G. Petocz, L. Kollar and M. E. Garcia-
Fernandez, Inorg. Chem., 2002, 41, 4435.
-3
˚
I > 2s(I)), wR2 = 0.0700, S = 1.02, -0.79 < Dr < 1.16 e A .
A disorder model was refined to handle the minor 0.0440(11)
inversion disorder of the Pt–Sn cation (taking into account Pt, Sn,
Cl, P & C1 disorder only).
13 31P NMR shows two signals at 19.2 and -17.6 ppm, see ref. 11.
14 J. Martincova, L. Dostal, A. Ruszicka, J. Taraba and R. Jambor,
Organometallics, 2007, 26, 4102; J. Martincova, R. Jambor, M.
Schurmann, K. Jurkschat, J. Honzicek and F. A. Almeida Paz,
Organometallics, 2009, 28, 4778; J. Martincova, R. Dostalova, L.
Dostal, A. Ruzicka and R. Jambor, Organometallics, 2009, 28, 4823.
15 The average bond lengths reported in the Cambridge Structural
Computational details
Calculations were run at the DFT level using the Gaussian G03W
software, the B3LYP functional (restricted) and the basis set
˚
Database for Pt(II)–SnCl3 = 2.565 A (25 hits, standard deviation
2426 | Dalton Trans., 2010, 39, 2423–2427
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The Royal Society of Chemistry 2010
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Knox, H. P. Hratchian, J. B. Cross, V. Bakken, C. Adamo, J. Jaramillo,
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W. Chen, M. W. Wong, C. Gonzalez and J. A. Pople, GAUSSIAN 03
(Revision B.03), Gaussian, Inc., Wallingford, CT, 2004.
0.044 A), Pt(0)–SnR2 = 2,501 A (15 hits, standard deviation 0.030 A),
˚
˚
Pt(II)–Me = 2.084 A (548 hits, standard deviation 0.047 A).
16 E. Lindner, R. Fawzi, H. A. Mayer, K. Elchele and W. Hiller,
Organometallics, 1992, 11, 1033; P. E. Garrou, Chem. Rev., 1981, 81,
229.
17 Stannylene ligands coordinated to a metal center could be stabilized
by additional coordination of extra donor(s) to the tin atom, see for
examples: M. D. Brice and F. A. Cotton, J. Am. Chem. Soc., 1973, 95,
4529; W. Petz, J. Organomet. Chem., 1979, 165, 199; A. L. Balch and
D. E. Oram, Organometallics, 1988, 7, 155.
18 M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria, M. A. Robb,
J. R. Cheeseman, J. A. Montgomery, Jr., T. Vreven, K. N. Kudin, J. C.
Burant, J. M. Millam, S. S. Iyengar, J. Tomasi, V. Barone, B. Mennucci,
M. Cossi, G. Scalmani, N. Rega, G. A. Petersson, H. Nakatsuji, M.
Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T.
Nakajima, Y. Honda, O. Kitao, H. Nakai, M. Klene, X. Li, J. E.
19 Pregosin noticed (ref. 8) that H2 activation by chloroplatinum com-
plexes and routine hydroformylation required more than one equivalent
of SnCl2 per Pt for best performance. This may be related to our
hypothesis that the excess of SnCl2 in Jain’s synthesis (ref. 11) acts
as a chloride acceptor to form [1][SnCl3].
This journal is
The Royal Society of Chemistry 2010
Dalton Trans., 2010, 39, 2423–2427 | 2427
©