Synthesis of monoorganotin(IV) chloride complexes of cis-1,2-bis(diphenylphosphino)ethylene: Solution and solid state structures

Article abstract of DOI:10.1016/j.jorganchem.2007.01.036

Organotin(IV) complexes of the type [RSnCl₃(cis-Ph₂PCH{double bond, long}CHPPh₂)] [R = Me (1), ⁿBu (2), Ph (3)] were prepared by the reaction of RSnCl₃ with the rigid bisphosphine ligand, cis-1,2-bis(diphenylphosphino)ethylene in dichloromethane. The complexes have been characterized both in solution and the solid state. Low temperature ³¹P and ¹¹⁹Sn NMR studies indicate two different phosphorus environments. The crystal structures indicate a weak but chelating mode of coordination of the two phosphorus atoms to tin, leading to a distorted octahedral geometry. In solution the complexes 1-3 undergo a redistribution reaction to form [SnCl₄(cis-Ph₂PCH{double bond, long}CHPPh₂)] (4) as one of the products. In order to confirm the redistribution, complex 4 has been prepared separately and characterized both structurally and spectrally.

Full text of DOI:10.1016/j.jorganchem.2007.01.036

Journal of Organometallic Chemistry 692 (2007) 2168–2174
www.elsevier.com/locate/jorganchem
Synthesis of monoorganotin(IV) chloride complexes
of cis-1,2-bis(diphenylphosphino)ethylene:
Solution and solid state structures
a,
*
Mothi Mohamed Ebrahim a,b, Helen Stoeckli-Evans
,
b,
*
Krishnaswamy Panchanatheswaran
a
ˆ ˆ
Institute of Microtechnology, University of Neuchatel, Neuchatel, Switzerland
b
School of Chemistry, Bharathidasan University, Tiruchirappalli, India
Received 23 November 2006; received in revised form 22 January 2007; accepted 23 January 2007
Available online 30 January 2007
Abstract
Organotin(IV) complexes of the type [RSnCl3(cis-Ph2PCH@CHPPh2)] [R = Me (1), nBu (2), Ph (3)] were prepared by the reaction of
RSnCl3 with the rigid bisphosphine ligand, cis-1,2-bis(diphenylphosphino)ethylene in dichloromethane. The complexes have been char-
acterized both in solution and the solid state. Low temperature 31P and 119Sn NMR studies indicate two different phosphorus environ-
ments. The crystal structures indicate a weak but chelating mode of coordination of the two phosphorus atoms to tin, leading to a
distorted octahedral geometry. In solution the complexes 1–3 undergo a redistribution reaction to form [SnCl4(cis-Ph2PCH@CHPPh2)]
(4) as one of the products. In order to confirm the redistribution, complex 4 has been prepared separately and characterized both struc-
turally and spectrally.
Ó 2007 Elsevier B.V. All rights reserved.
Keywords: Organotin(IV) complexes; Bisphosphine complexes; NMR spectroscopy; Ligand scrambling
1. Introduction
when 1,2-bis(diphenylphosphino)ethane (dppe) was
allowed to react with R2SnCl2 (R = Me, Bu, Ph [12] and
n
The utility of organotin halides to study the fundamen-
tally important Lewis acid–base model and reactivity of
organotin species had been the subject of several investiga-
tions [1–3]. In contrast to the availability of the large
amount of structural data with O-, N- and S-donor ligands
[4], the structurally characterized organotin complexes con-
taining direct Sn–P bonds are still rare [5–7]. Several NMR
(31P and 119Sn) investigations of the complexes of organo-
tin acceptors, RnSnCl4ꢀn (n = 1, 2) and mono- and bis-
phosphines have been carried out suggesting coordination
of phosphorus to tin [3,8–11]. On the other hand structural
characterizations have revealed the presence of a Sn–O–P
link, generated by the aerial oxidation of the bisphosphine
Bz [13]). In the case of highly Lewis acidic RSnCl3
(R = Me, nBu and Ph), despite the satisfactory spectro-
scopic evidence for the formation of Sn–P bond, no prod-
uct could be characterized structurally from the reaction
with bis(diphenlyphosphino)methane (dppm) or dppe
[12]. Although the importance of organotin halide–phos-
phine complexes has been realized in the catalysis of ring
opening of a,b-epoxyketones [14], the lack of structural
understanding is perhaps responsible for not using
organotin–phosphine complexes as potential catalysts.
The difference in reactivity between cis-1,2-bis(diphenylph-
oshino)ethylene (cis-dppen) and its saturated analogue,
dppe with various transition metals has been observed in
a number of studies [15–18]. The purpose of the present
study is to investigate the interaction of the rigid bisphos-
phine cis-dppen with monoorganotin chlorides. Herein
*
Corresponding authors. Tel.: +91 431 2407053; fax: +91 431 2407045.
E-mail address: panch_45@yahoo.co.in (K. Panchanatheswaran).
0022-328X/$ - see front matter Ó 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2007.01.036

M.M. Ebrahim et al. / Journal of Organometallic Chemistry 692 (2007) 2168–2174
2169
we report the synthesis, solution and solid state structures
of a series of monoorganotin chloride, RSnCl3 (R = Me,
nBu, Ph) complexes containing cis-dppen.
P–C6H5). 31P NMR (162 MHz, CD2Cl2): d ꢀ24.64 (br),
ꢀ26.60 (s). Mass spectrum (ESI) {m/z [assignment] (%)}:
643 [M ꢀ Cl]+(14), 917 [M*]+ (1), 883 [M* ꢀ Cl]+(100)
where M* = [(SnCl4)2(cis-dppen)].
2. Experimental
2.1.3. [PhSnCl3(cis-Ph2PCH@CHPPh2)] (3)
All solvents were dried and distilled prior to use using
standard methods [19]. Reactants and reagents were
obtained from Aldrich Chemical Company and used with-
out further purification. The IR spectra in the interval of
4000–400 cmꢀ1 were recorded on a Perkin–Elmer 1720X
FT-IR spectrometer. The 1H, 31P–{1H} and 119Sn–{1H}
NMR spectra were recorded on Bruker DPX 400 MHz
or DRX 500 MHz instrument referenced relative to resid-
ual solvent, 85% H3PO4 and Sn(CH3)4, respectively. Mass
spectra were measured on a Bruker FTMS 4.7T BioAPEX
II instrument using the solution of the complexes in a mix-
ture of methanol and dichloromethane. Elemental analyses
Compound 3 was obtained by following the same proce-
dure as 1 by using phenyltin trichloride (0.152 g, 0.5 mmol)
and cis-dppen (0.2 g, 0.5 mmol) to yield a colourless precip-
itate. Single crystals were obtained when a chloroform
solution of the compound was kept at ꢀ5 °C for several
days. Yield 0.25 g, 71%. Mp 160–162 °C. Anal. Calc. for
C32H27Cl3P2Sn: C, 55.02; H, 3.90. Found: C, 54.94; H,
3.86%. IR (cmꢀ1): 3050, 2983, 1572, 1477, 1482, 1435,
1188, 1159, 1097, 997, 746, 735, 689, 550, 517, 480, 440.
1H NMR (400 MHz, CDCl3): d 7.34–7.49, 7.54–7.65,
7.79–7.87 (m, 27H, P–CH@CH, P–C6H5 and Sn–C6H5).
31P NMR (162 MHz, CDCl3): d ꢀ26.71 (br), ꢀ26.96 (s,
[1J(119Sn–31P): 677.0], [1J(117Sn–31P): 646.2]). Mass spec-
trum (ESI) {m/z [assignment] (%)}: 663 [M ꢀ Cl]+ (1),
883 [M* ꢀ Cl]+ (100) where M* = [(SnCl4)2(cis-dppen)].
´
were performed at the Ecole d’ingenieurs de Fribourg,
Switzerland.
2.1. Synthesis
2.1.4. [SnCl4(cis-Ph2PCH@CHPPh2)] (4)
2.1.1. [MeSnCl3(cis-Ph2PCH@CHPPh2)] (1)
To a solution of cis-dppen (0.2 g, 0.5 mmol) in dichloro-
methane (10 ml), a solution of SnCl4 (0.06 ml, 0.5 mmol) in
dichloromethane (10 ml) was added. The resulting clear
solution was stirred for 8 h whereupon the solution became
slightly turbid. The solvent was reduced to 10 ml and addi-
tion of n-pentane (20 ml) caused the precipitation of the
product as a yellowish white solid. It was filtered and
recrystallized by vapour diffusion of n-pentane into a
dichloromethane solution to obtain single crystals. Yield
0.26 g (79%). Mp: 179–180 °C. Anal. Calc. for
C26H22Cl4P2Sn: C, 47.54; H, 3.38. Found. C, 47.76; H,
3.40%. IR (cmꢀ1): 3056, 3001, 1482, 1435, 1263, 1189,
1162, 1098, 1025, 997, 749, 727, 688, 552, 518, 499, 478,
462. 1H NMR (400 MHz, CD2Cl2): d 7.51–7.55, 7.60–
7.64, 7.79–7.85 (m, 20H, P–C6H5), 7.96 (dd, 2H, P–
Methyltin trichloride (0.121 g, 0.5 mmol) in dichloro-
methane (5 ml) was added dropwise to a solution (5 ml)
of cis-dppen (0.20 g, 0.5 mmol) also in dichloromethane.
The resulting clear colourless solution was stirred for 3 h
and the solvent reduced to 5 ml. Upon addition of n-pen-
tane (15 ml) a white crystalline solid precipitated. It was fil-
tered and recrystallized by vapour diffusion of n-pentane
into a dichloromethane solution, to obtain single crystals.
Yield 0.25 g, 79%. Mp: 147–148 °C. Anal. Calc. for
C27H25Cl3P2Sn: C, 50.95; H, 3.96. Found: C, 50.64; H,
3.92%. IR (cmꢀ1): 3035, 2992, 1483, 1436, 1190, 1147,
1096, 1025, 998, 758, 753, 742, 721, 696, 686, 548, 531,
1
510, 474, 465. H NMR (400 MHz, CD2Cl2): d 1.57 (t,
3H, Sn–CH3), [2J(119Sn–1H): 114.6], [2J(117Sn–1H): 109.8];
7.42–7.53, 7.62–7.70 (m, 22H, P–CH@CH and P–C6H5).
31P NMR (162 MHz, CD2Cl2): d ꢀ25.92 (br), ꢀ26.58 (s).
Mass spectrum (ESI) {m/z [assignment] (%)}: 601
[M ꢀ Cl]+ (4), 917 [M*]+ (22), 883 [M* ꢀ Cl]+ (100) where
M* = [(SnCl4)2(cis-dppen)].
CH@CH,
3J(31P–1H) = 14.0,
[3J(119Sn–1H):
45.2],
[3J(117Sn–1H): 43.2]). 31P NMR (162 MHz, CD2Cl2): d
ꢀ26.60 (s), [1J(119Sn–31P): 717.4], [1J(117Sn–31P): 685.9].
119Sn NMR (186 MHz, CD2Cl2) : d ꢀ628 (t). Mass spec-
trum (APCI) {m/z [assignment] (%)}: 655 [M]+(30), 586
[M ꢀ 2Cl]+ (100).
2.1.2. [nBuSnCl3(cis-Ph2PCH@CHPPh2)] (2)
Compound 2 was obtained as for 1 by using n-butyltin
trichloride (0.142 g, 0.5 mmol) and cis-dppen (0.2 g,
0.5 mmol). Single crystals were obtained by vapour diffu-
sion of n-pentane into a dichloromethane solution. Yield
0.27 g, 78%. Mp: 159–160 °C. Anal. Calc. for
C30H31Cl3P2Sn: C, 53.10; H, 4.60. Found: C, 52.95; H,
4.61%. IR (cmꢀ1): 3056, 2951, 2924, 2867, 1482, 1435,
1156, 1142, 1123, 1095, 1072, 1026, 997, 751, 743, 725,
2.2. X-ray crystallography
The intensity data were collected at 173 K (ꢀ100 °C) on
a Stoe Mark I-Image Plate Diffraction System (complex 2)
and a Stoe Mark II-Image Plate Diffraction System [20]
(complexes 1, 3 and 4) using Mo Ka graphite monochro-
mated radiation. The structures were solved by direct
methods using the program SHELXS-97 [21]. The refinement
and all further calculations were carried out using SHELXL-
97 [22]. The H-atoms were included in calculated positions
and treated as riding atoms using SHELXL default parame-
ters. The non-H atoms were refined anisotropically, using
1
714, 690, 550, 518, 478. H NMR (400 MHz, CD2Cl2): d
0.89 (t, 3H, CH3–, J = 7.2); 1.39 (sex, 2H, –CH2–,
J = 7.5), 1.78 (qt, 2H, –CH2–, J = 7.5), 2.19 (br, 2H, –
CH2–Sn); 7.38–7.48, 7.53–7.71 (m, 22H, P–CH@CH and

2170
M.M. Ebrahim et al. / Journal of Organometallic Chemistry 692 (2007) 2168–2174
Fig. 4. Molecular structure of 4 with atom numbering scheme. The
CH2Cl2 solvent molecule has been omitted for clarity.
Fig. 1. Molecular structure of 1 with atom numbering scheme at 50%
probability ellipsoids.
weighted full-matrix least-squares on F2. The n-butyl chain
in 2 was found to be disordered over two positions A & B
(occupancies 0.526 / 0.474). Semi-empirical absorption
corrections were applied using the MULscanABS routine
in PLATON [23]; transmission factors for 1 (Tmin/Tmax
0.563/0.779), 2 (Tmin/Tmax = 0.769/0.804), 3 (Tmin/Tmax
=
=
0.683/0.763) and 4 (Tmin/Tmax = 0.517/0.902). Further
crystallographic data are given in Table 2. The molecular
structure and crystallographic numbering schemes are illus-
trated in the PLATON drawings (Figs. 1–4).
3. Results and discussion
3.1. Synthesis
The reaction of cis-dppen with RSnCl3 (R = Me, nBu or
Ph) in dichloromethane yielded colourless derivatives, 1–3,
in good yields. Rigorous exclusion of oxygen was not nec-
essary as sufficiently pure products were obtained even in
aerobic conditions. The products in the solid state are
highly stable to air and moisture and oxidizes slowly in
solution. They are moderately soluble in chlorinated sol-
vents, acetone and DMSO but insoluble in diethyl ether,
aliphatic hydrocarbons and water. It is to be noted that
the crystallizations of the complexes were facile in contrast
to the dppm or dppe derivatives [12]. The stability of these
complexes can be attributed to the chelate effect of the
ligand as well as to the electronegative effects of the three
chlorine atoms.
Fig. 2. Molecular structure of 2 with atom numbering scheme. The
disordered nBu group is shown with dashed bonds.
3.2. Spectroscopy
In the IR spectra the absence of any significantly strong
band in the region around 1190–1150 cmꢀ1 assignable to
the m(P@O) [12], indicates that the ligand in the products
1
remain unoxidised. The H NMR spectrum of 1 shows a
sharp singlet at 1.57 ppm for the methyl group bonded to
tin with satellites due to coupling with nuclei 119Sn
[2J(119Sn–1H): 114.6 Hz] and 117Sn [2J(117Sn–1H):
Fig. 3. Molecular structure of 3 with atom numbering scheme. The two
CHCl3 solvent molecules have been omitted for clarity.
1
109.8 Hz]. The H NMR spectrum of 2 exhibits a broad

M.M. Ebrahim et al. / Journal of Organometallic Chemistry 692 (2007) 2168–2174
2171
Table 1
resonance centered at 2.19 ppm for the CH2 group
attached to tin, while the other signals due to n-butyl group
are sharp. The resonance due to the protons of the phenyl
group attached to tin in 3 and the –CH@CH– protons in all
the complexes are merged with the other aromatic protons
of the ligand.
Low temperature 31P and 119Sn NMR spectral dataa (d in ppm and J in
Hz) (for A, B and X notations see figure below)
dA
(
31P)
dB
(
31P)
dX
(
119Sn)
JA–B
JA–X
JB–X
1b
2b
3c
ꢀ24.09
ꢀ23.07
ꢀ25.02
ꢀ31.32
ꢀ30.24
ꢀ32.51
ꢀ462.5
ꢀ456.3
ꢀ510.1
307
292
306
2419
2344
2327
1283
1530
1156
The 31P NMR of all the complexes at 300 K in CD2Cl2
exhibit two resonances in the region of ꢀ24.64 to
ꢀ26.96 ppm; the low intensity signal around ꢀ26 ppm
appears sharp and the high intensity signal is broad. Upon
lowering the temperatures to 200 K, the major resonance
gives rise to a quartet with the corresponding tin satellites.
The spectral parameters have been obtained by solving the
spectra for an ABX spin system and are listed in Table 1.
The 31P NMR spectra represent the AB part while the
119Sn NMR spectra form the X part. The 31P NMR chem-
ical shifts occur upfield to that of the free ligand (d ꢀ21.95,
CD2Cl2), the coupling constants J (Sn–PA) and J (Sn–PB)
(see Table 1) agree well with values reported in the litera-
ture [6,11]. As observed previously [24], the reason for
the rather surprising upfield coordination shift in the 31P
NMR spectra remains unclear. One can expect either four
or six line pattern in the X part of the ABX spectra,
depending upon the ratio of the coupling constant to the
chemical shift [25]. The 119Sn NMR spectra at lower tem-
peratures exhibit six lines for 1 and 3 whereas 2 shows a
four line pattern. The chemical shifts (Table 1) are in the
range reported previously for six coordinate geometry
around tin [26].
a
ABX system solved according to reference [25].
In CD2Cl2, 202.45 MHz (31P NMR), 186.40 MHz (119Sn NMR) at
b
200 K.
c
In CDCl3, 202.45 MHz (31P NMR), 186.40 MHz (119Sn NMR) at
225 K.
tin(IV) halides or organotin(IV) halides with phosphine
ligands [24,27] and found to be the major cause for room
temperature line broadening in the 31P NMR spectra. In
order to confirm the ligand dissociation, the 31P NMR
spectra were measured at higher temperatures. At 308 K,
the broad peak sharpened and moved to a position around
ꢀ22 ppm (free ligand ꢀ21.95 ppm in CD2Cl2 at 300 K),
indicating that the dissociation is complete at higher tem-
peratures.
Cl
R
Cl
P
Cl
Cl
P
B
Sn
Sn
X
R
P
P
A
The hexacoordinate complexes of the type discussed
above can have two configurations I and II (vide infra).
Only configuration I can give rise to two different phospho-
rus environments leading to an ABX type spectrum. The
low temperature (200 K) 31P NMR spectra are consistent
with form I. The absence of tin satellites for the major peak
at ambient temperature 31P NMR spectra shows that some
kind of exchange is occurring at this temperature. Ligand
dissociation has been widely observed in the adducts of
Cl
Cl
II
I
The minor signal in the 31P NMR spectra is observed
upfield (ꢀ26.6 ppm) to that of the free ligand. Tin satellites
could be observed for this peak in the spectrum of 3, while
for 1 and 2 the signal intensity is too low to observe
Table 2
Crystal data and refinement details for 1–4
Compound
1
2
3 Æ 2CHCl3
4 Æ CH2Cl2
Empirical formula
Formula weight
Crystal system
Space group
C27H25Cl3P2Sn
636.45
Monoclinic
Cc
C30H31Cl3P2Sn
678.53
Monoclinic
P21/c
C32H27Cl3P2Sn, 2(CHCl3)
C26H22Cl4P2Sn, CH2Cl2
741.79
Monoclinic
P21/c
937.25
Orthorhombic
Pbca
˚
a (A)
17.6425(13)
9.5408(5)
15.9723(11)
98.768(6)
2657.1(3)
4
11.1115(8)
13.0577(8)
20.5792(14)
101.109(9)
2929.9(3)
4
15.6807(7)
21.9531(10)
22.7673(9)
90
7837.4(6)
8
13.0900(9)
11.0710(7)
21.2812(13)
104.283(5)
2988.7(3)
4
˚
b (A)
˚
c (A)
b (°)
3
˚
V (A )
Z
Absorption coefficient (mmꢀ1
Collected reflections
Independent reflections
R(int)
)
1.399
16536
6918
0.0211
0.0166
0.0456
1.274
22631
5679
0.0388
0.0261
0.0601
1.372
45870
6968
0.0823
0.0550
0.1153
1.515
27530
8070
0.0416
0.0293
0.0702
R1 (Observed data)
wR2(all data)

2172
M.M. Ebrahim et al. / Journal of Organometallic Chemistry 692 (2007) 2168–2174
satellites. Change in temperature did not affect this signal
as it remains sharp between 300 and 200 K. On the basis
of J(P–Sn) coupling constants and the sharp feature, the
signal has been attributed to the presence of [SnCl4(cis-
dppen)] due to a redistribution reaction in solution.
three complexes, the C@C distance is similar to the dis-
tance of 1.334(6) A [30] observed in the free ligand. This
˚
precludes any p bonding interactions with tin. The Sn–C
˚
bond lengths in 1 and 2 [2.133(2) and 2.177(3) A, respec-
tively] are quite close to the values reported in the literature
˚
[31]. In complex 3, however, the same distance [2.20(4) A] is
2RSnCl3ðcis-dppenÞ ! SnCl4ðcis-dppenÞ
þ R2SnCl2ðcis-dppenÞ
longer. As expected the rigid bisphosphine forms a chelate
with the Sn albeit with a slight distortion. The Sn(1)–P(1)
distances for complexes 1–3 [respectively, 2.667(1),
˚
In order to support the above formulation [SnCl4(cis-
dppen)] was prepared separately and its 31P NMR chemical
shift recorded. A sharp signal at ꢀ26.6 ppm with tin satel-
lites was observed. The same signals were observed in the
solution of 1–3. When the reaction mixture containing
RSnCl3 and cis-dppen was stirred for more than 24 h at
room temperature a large amount of [SnCl4(cis-dppen)]
could be isolated, indicating the facile nature of the dispro-
portionation. Mass spectra of complexes 1–3 which show,
in addition to molecular peaks, a signal with 100% intensity
at m/z 883 for [M*ꢀCl]+, where M* = [(SnCl4)2(cis-dppen)]
(mass = 917) indicate the formation of the species M* un-
der ESI conditions. We have recently demonstrated
through computational studies that the disproportionation
reactions of organotin(IV) trihalides are energetically
favourable [28]. Experimentally, the formation of
[SnCl4(Bu3P)] has been observed previously for the reac-
tion of PhSnCl3 with Bu3P [3,10]. Comparison of the spec-
troscopic data of the three complexes at 300 K shows that
both redistribution and dissociation is faster for 3 than for
1 or 2. Although we could not isolate [R2SnCl2(cis-dppen)]
complexes, their presence are indicated as low intensity sig-
nals in 1H, 31P (ꢁꢀ21.5 ppm at 300 K) and 119Sn
(ꢁꢀ485 ppm at 200 K). The latter signals assignable to
tin in an octahedral environment occur considerably up-
field to the 119Sn shifts, 6.0, ꢀ6.1 and ꢀ65 ppm reported
2.694(1) and 2.704(1) A] are shorter than the Sn(1)–P(2)
˚
distances [respectively, 2.758(1), 2.753(1) and 2.723(1) A].
The disparity in the Sn–P bond lengths with the ligand
present in the chelating mode could be due to the trans
influences of the ligands attached to Sn. The shorter
Sn(1)–P(1) distance being the bond trans to the carbon
Table 3
˚
Selected interatomic distances (A) and angles (°) in 1–3
1
2
3
Interatomic distances
Sn(1)–Cl(1)
Sn(1)–Cl(2)
Sn(1)–Cl(3)
Sn(1)–C(27)
Sn(1)–P(1)
Sn(1)–P(2)
P(1)–C(1)
P(1)–C(3)
P(1)–C(9)
P(2)–C(2)
P(2)–C(15)
P(2)–C(21)
C(1)–C(2)
2.4615(5)
2.5053(5)
2.4219(5)
2.133(2)
2.6686(5)
2.7578(5)
1.8081(18)
1.8128(19)
1.8028(19)
1.8054(18)
1.810(2)
2.4817(7)
2.4621(7)
2.4360(8)
2.177(3)
2.6945(7)
2.7526(7)
1.802(3)
1.813(3)
1.819(3)
1.806(3)
1.810(3)
1.820(3)
1.327(4)
2.4399(13)
2.4962(13)
2.4233(12)
2.202(4)
2.7036(13)
2.7231(13)
1.806(5)
1.805(6)
1.814(5)
1.796(5)
1.811(5)
1.8160(18)
1.338(2)
1.803(5)
1.337(7)
Bond angles
C(27)–Sn(1)–Cl(3)
C(27)–Sn(1)–Cl(1)
Cl(3)–Sn(1)–Cl(1)
C(27)–Sn(1)–Cl(2)
Cl(3)–Sn(1)–Cl(2)
Cl(1)–Sn(1)–Cl(2)
C(27)–Sn(1)–P(1)
Cl(3)–Sn(1)–P(1)
Cl(1)–Sn(1)–P(1)
Cl(2)–Sn(1)–P(1)
C(27)–Sn(1)–P(2)
Cl(3)–Sn(1)–P(2)
Cl(1)–Sn(1)–P(2)
Cl(2)–Sn(1)–P(2)
P(1)–Sn(1)–P(2)
C(9)–P(1)–C(1)
C(9)–P(1)–C(3)
C(1)–P(1)–C(3)
C(9)–P(1)–Sn(1)
C(1)–P(1)–Sn(1)
C(3)–P(1)–Sn(1)
C(2)–P(2)–C(15)
C(2)–P(2)–C(21)
C(15)–P(2)–C(21)
C(2)–P(2)–Sn(1)
C(15)–P(2)–Sn(1)
C(21)–P(2)–Sn(1)
C(2)–C(1)–P(1)
C(1)–C(2)–P(2)
102.96(7)
92.97(7)
93.833(19)
94.39(8)
91.713(19)
169.561(17)
170.26(7)
85.945(17)
90.311(16)
81.260(16)
95.57(7)
161.408(17)
86.643(16)
85.290(16)
75.465(14)
108.88(9)
106.22(9)
103.68(9)
111.90(6)
105.72(6)
119.78(6)
105.55(8)
105.50(8)
106.94(8)
103.55(6)
113.87(6)
120.10(6)
123.55(14)
123.04(13)
99.08(11)
98.63(8)
95.78(2)
94.55(8)
92.65(3)
163.01(3)
171.83(11)
89.00(2)
79.22(2)
86.22(2)
94.85(11)
166.04(2)
82.92(2)
101.07(12)
93.77(12)
90.90(5)
93.06(12)
91.74(5)
172.07(5)
169.60(12)
89.11(4)
88.13(4)
84.44(4)
94.90(12)
163.52(4)
92.11(4)
n
previously for MeSnCl3, BuSnCl3 and PhSnCl3, respec-
tively [29].
3.3. Crystal and molecular structures
The solid state structures of 1–3 were determined by sin-
gle-crystal X-ray diffraction and are shown in Figs. 1–3.
Selected bond distances and angles are listed in Table 2.
The asymmetric units of 1 and 2 contain a molecule of
the complex, while for 3 the asymmetric unit is composed
of a molecule of the complex and two molecules of chloro-
form solvent. The molecular structures of the complexes
are similar regardless of the nature of the organic group
attached to tin. Therefore a general description for these
compounds is given.
The geometry around the Sn atoms is distorted octahe-
dral with the C atom of the tin bound organic group, one
Cl atom and two P atoms of the chelating bisphosphine
forming the equatorial plane, while the other two Cl atoms
are axially disposed. The P(1)–Sn(1)–P(2) bite angle is the
smallest amongst the cis angles, being equal to 75.46(1)°,
77.09(2)° and 74.80(4)° for 1, 2 and 3, respectively. In all
85.34(2)
77.09(2)
83.29(4)
74.80(4)
104.1(3)
107.0(3)
105.05(13)
105.12(12)
102.03(12)
119.24(9)
106.07(9)
117.35(9)
105.63(12)
102.66(12)
106.33(12)
105.38(9)
116.03(9)
119.16(9)
126.0(2)
105.5(3)
121.86(18)
104.79(17)
112.08(19)
107.7(2)
104.1(2)
105.6(2)
104.69(17)
117.20(17)
116.54(18)
122.8(4)
123.9(2)
123.1(4)

M.M. Ebrahim et al. / Journal of Organometallic Chemistry 692 (2007) 2168–2174
2173
Table 4
ligand, cis-dppen. The phosphine chelates to tin in an
unsymmetrical fashion to form octahedral complexes.
The two different Sn–P bond lengths observed in the solid
state corroborate well with the low temperature 31P NMR
spectra which exhibit two different J(Sn–P) values in all the
organotin complexes. In solution these complexes undergo
facile redistribution to form [SnCl4(cis-dppen)]. The forma-
tion of the above stable crystalline complexes suggests that
although the Sn–P coordination is weaker the rigidity of
the bisphosphine can help in stabilizing the complexes
resisting, to some extent, both oxidation and dissociation
of the ligand.
˚
Selected interatomic distances (A) and angles (°) in 4
Bond lengths
Cl(1)–Sn(1)
Cl(3)–Sn(1)
P(1)–Sn(1)
C(1)–P(1)
C(7)–P(1)
C(13)–P(1)
C(13)–C(14)
2.4102(6)
2.3745(6)
2.6537(5)
1.808(2)
1.801(2)
1.802(2)
1.329(3)
Cl(2)–Sn(1)
Cl(4)–Sn(1)
P(2)–Sn(1)
C(15)–P(2)
C(21)–P(2)
C(14)–P(2)
2.4138(5)
2.3812(6)
2.6780(5)
1.812(2)
1.802(2)
1.804(2)
Bond angles
Cl(1)–Sn(1)–Cl(2)
Cl(4)–Sn(1)–Cl(1)
Cl(4)–Sn(1)–Cl(2)
Cl(1)–Sn(1)–P(1)
Cl(2)–Sn(1)–P(1)
Cl(3)–Sn(1)–P(1)
Cl(4)–Sn(1)–P(1)
P(1)–Sn(1)–P(2)
C(13)–P(1)–Sn(1)
C(21)–P(2)–Sn(1)
C(15)–P(2)–Sn(1)
171.89(2)
92.58(2)
93.40(2)
Cl(3)–Sn(1)–Cl(1)
Cl(3)–Sn(1)–Cl(2)
Cl(3)–Sn(1)–Cl(4)
Cl(1)–Sn(1)–P(2)
Cl(2)–Sn(1)–P(2)
Cl(3)–Sn(1)–P(2)
Cl(4)–Sn(1)–P(2)
C(7)–P(1)–Sn(1)
C(1)–P(1)–Sn(1)
C(14)–P(2)–Sn(1)
92.67(2)
91.89(2)
98.27(2)
87.138(19)
85.904(18)
93.268(19)
168.463(19)
114.03(7)
118.45(7)
104.39(7)
88.025(19)
86.490(18)
171.573(19)
90.090(19)
78.374(16)
105.24(7)
113.47(7)
120.66(7)
Acknowledgements
M.M.E. would like to thank the Swiss Federal Commis-
sion for a scholarship to study at the University of Neuchaˆ-
tel. We express our sincere thanks to Dr. Klaus J. Kulicke,
University of Basel for low temperature 119Sn and 31P
NMR measurements.
attached to Sn, while the longer Sn(1)–P(2) distance is trans
to a chloride. The Sn–P distances are significantly longer
˚
Appendix A. Supplementary material
than the sum of the covalent radii of atoms (2.51 A) but
˚
shorter than the sum of the van der Waals radii (3.9 A)
CCDC 627633, 627634, 627635 and 627636 contain the
supplementary crystallographic data for 1, 2, 3 Æ 2CHCl3,
4 Æ CH2Cl2. These data can be obtained free of charge via
http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from
the Cambridge Crystallographic Data Centre, 12 Union
Road, Cambridge CB2 1EZ, UK; fax: +(44) 1223-336-
033; or e-mail: deposit@ccdc.cam.ac.uk. Supplementary
data associated with this article can be found, in the online
version, at doi:10.1016/j.jorganchem.2007.01.036.
[32]. The Sn-Cl distances lie in the range of 2.422(1)–
˚
˚
2.505(1) A, which is within the range of 2.37–2.60 A
observed previously [33]. The Sn(1)–Cl(3) bond, which lies
trans to the phosphorus, is shorter than the other two
bonds, Sn(1)–Cl(1) and Sn(1)–Cl(2) (Table 3).
The crystal structure of [SnCl4(cis-dppen)] (4) has been
determined for comparison purposes. Fig. 4 shows the
molecular structure and Table 4 contains selected bond dis-
tances and angles. The asymmetric unit contains a
molecule of the complex along with a molecule of dichloro-
methane solvent. The central tin atom is coordinated to the
bidentate ligand and four chloro ligands in a slightly dis-
torted octahedral geometry. The Sn–P distances [2.654(1)
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