Reactions of organotin(IV) compounds with platinum complexes. Part II. Oxidative addition of SnRxCl4-x to [Pt(COD)2] and subsequent reactions with tertiary phosphines

Article abstract of DOI:10.1016/S0022-328X(99)00408-8

Organotin(IV) compounds SnR_xCl_4-x (R=Me, Ph; x=4-0) add oxidatively to [Pt(COD)2] (COD=cycloocta-1,5-diene) to yield platinum(II) complexes in which Pt has inserted into the Sn-Cl or Sn-R bonds, displacing one COD entity. The new com

Full text of DOI:10.1016/S0022-328X(99)00408-8

www.elsevier.nl/locate/jorganchem
Journal of Organometallic Chemistry 590 (1999) 25–35
Reactions of organotin(IV) compounds with platinum complexes
Part II. Oxidative addition of SnRxCl4−x to [Pt(COD)2] and
subsequent reactions with tertiary phosphinesꢀ
Talal A.K. Al-Allaf *,1
Department of Chemistry, College of Science, Uni6ersity of Mosul, Mosul, Iraq
Received 1 December 1998
Abstract
Organotin(IV) compounds SnRxCl4−x (R=Me, Ph; x=4−0) add oxidatively to [Pt(COD)2] (COD=cycloocta-1,5-diene) to
yield platinum(II) complexes in which Pt has inserted into the SnꢀCl or SnꢀR bonds, displacing one COD entity. The new
complexes react with tertiary phosphines, e.g. PEt3, PPh3, Ph2PCH2CH2PPh2 (DPPE) at or below room temperature with
displacement of the remaining COD. Some of the resulting platinum–phosphine complexes, e.g. cis-[PtMe(SnMe3)(PPh3)2], cis- or
trans-[PtCl(SnMe3)(PPh3)2] cannot be prepared by the direct reaction between [Pt(C2H4)(PPh3)2] or [Pt(PPh3)3] and SnMe4 or
SnMe3CI, respectively, showing the advantage of this method. Both the COD complexes and their corresponding phosphine
complexes were characterised by physical and spectroscopic methods. The thermodynamic stabilities of the complex
[PtCl(SnMe3)(COD)], its corresponding phosphine complex, cis- and trans-[PtCl(SnMe3)(PPh3)2], and the complex cis-
[PtMe(SnMe3)(PPh3)2] were studied. © 1999 Elsevier Science S.A. All rights reserved.
Keywords: Organotin complexes; Platinum complexes; Cyclooctadiene complexes; Phosphine complexes
tertiary phosphines. It also describes the thermody-
namic stability of the complex obtained by reacting
1. Introduction
SnMe3C1 and [Pt(COD)2], its corresponding phosphine
complex and the complex cis-[PtMe(SnMe3)(PPh3)2] at
various temperatures.
In a previous paper [1], the oxidative addition of
SnRxCl4x compounds to Pt(0)–phosphine complexes
was surveyed. Pt(0) complexes other than those con-
taining phosphines, e.g. [Pt(COD)2] (COD=cycloocta-
1,5-diene) were first studied by Stone and co-workers
[2], in which RX compounds (R=organic species, X=
Cl or Br) add oxidatively to [Pt(COD)2] to give [PtRX(-
COD)] complexes. The remaining COD can be replaced
by other neutral ligands, e.g. tertiary phosphines and
this was reported by Eaborn et al. [3]. The available
literature provides no examples of the oxidative addi-
tion of organotin(IV) compounds to [Pt(COD)2]. The
present paper describes the products obtained from the
reaction of SnRxCl4−x (R=Me or Ph and x=4–0)
with [Pt(COD)2], and their subsequent reactions with
2. Results and discussion
2.1. Reaction of SnRxCl4−x with [Pt(COD)2]
The reaction of organotin(IV) compounds SnRxCl4−x
with [Pt(COD)2] leads to complexes containing PtꢀSn
bonds as summarised in Scheme 1.
The complexes thus obtained were characterised
physicochemically and spectroscopically in order to
confirm their structures. Their physical properties are
listed in Table 1.
It seems likely that the reaction of SnPh3Cl and
SnPh2Cl2 with [Pt(COD)2] leads to insertion of Pt into
SnꢀPh bonds to give complexes 1 and 2, respectively
(Scheme 1), as is usual for reactions of organotin
ꢀ For Part 1 of this work, see Ref. [1].
* Corresponding author. Tel.: +962-6-5237181; fax: +962-6-5232899.
1 Present address: Department of Chemistry, Faculty of Science,
Applied Science University, Amman 11931, Jordan.
0022-328X/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(99)00408-8

26
T.A.K. Al-Allaf / Journal of Organometallic Chemistry 590 (1999) 25–35
Scheme 2. The products formed from the reaction of
[PtMe(SnMe3)(COD)] with various tertiary phosphines.
Scheme 1. The products (1–6) formed from the reaction of [Pt-
(COD)2] and various tin compounds.
24 300 Hz and Pregosin et al. observed an even higher
value: 28 954 Hz, for similar complexes [10,9]). This
result was due to the fact that both the Pt and Sn atoms
are attached to a more electronegative group (Cl),
which in turn allows a large coupling, cf. J(195Ptꢀ119Sn)
of complex 3, i.e. [PtCl(SnMe2Cl)(COD)] (13 135 Hz)
almost half of that of complex 6.
Many attempts were made to react SnPh4 with [Pt(-
COD)2] in order to obtain a complex containing PtꢀSn
bonds. All were unsuccessful.
compounds with Pt(0) complexes [4]. Confirmation is
provided by the complete disappearance of w (PtꢀCl) in
the IR spectra, as well as the 31P-NMR spectral data of
their corresponding cis-phosphine complexes (vide in-
fra), which showed no PꢀPtꢀCl species; the 195Ptꢀ31P
coupling constant is assigned to P in a trans relation-
ship to Ph, rather than to Cl [5].
It is noteworthy that SnPh4, in contrast to SnMe4,
reacts readily with other Pt(0) complexes, e.g.
[Pt(C2H4)(PPh3)2] [4], [Pt(PEt3)n] (n=3 or 4) [1], to give
complexes containing PtꢀSn bonds.
Complexes 1–6 (Scheme 1) can serve as very good
starting materials for the preparation of many com-
plexes containing PtꢀSn bonds, which could not be
easily made by direct methods.
By contrast, SnMe3Cl and SnMe2Cl2 react with [Pt(-
COD)2] by insertion of Pt into SnꢀCl bonds to give
complexes 3 and 4. This result was confirmed by the
presence of an IR band at ca. 330 cm−1 in the products
attributed to w (PtꢀCl) [6,7]. It is not surprising for the
reaction of SnMe2Cl2 with Pt(0) complexes to give
complexes of an insertion of Pt into SnꢀCl bonds [4],
but the unusual phenomenon is that for SnMe3Cl in
which all reported literature, prior to this work, stated
that reactions of SnMe3Cl with Pt(0) complexes led
always to complexes of an insertion of Pt into SnꢀMe
bonds [4].
SnMe4 is inert towards reactions with Pt(0), apart
from one statement by Steele and co-workers [8], who
reported that SnMe4 reacts with [Pt(PEt3)4] in benzene
under reflux to give cis-[PtMe(SnMe3)(PEt3)2]. We be-
lieve this result was incorrect (vide infra). However, we
discovered that SnMe4 does react with [Pt(COD)2] un-
der certain conditions to give [PtMe (SnMe3)(COD)] (5)
as an unstable oil at ambient temperature. This com-
plex serves as a good precursor for many corresponding
phosphine- or nitrogen-containing ligand–platinum
complexes that cannot be prepared by other routes
(vide infra).
2.2. Displacement of COD by tertiary phosphine
The complexes 1–6 (Scheme 1) were treated sepa-
rately with the tertiary phosphines PEt3, PBu3, PPh3,
Ph2PCH2PPh2 (DPPM), Ph2PCH2CH2PPh2 (DPPE),
the tertiary phosphite P(OPh)3 and bipyridine, in chlo-
rinated or non-chlorinated solvents. The structure of
the complexes varied according to the reaction con-
ditions.
The complex [PtMe(SnMe3)(COD)] reacts readily
with various tertiary phosphines in toluene at ca. −
40°C to give the corresponding phosphine complexes
(Scheme 2).
All the complexes prepared showed 31P-NMR pat-
terns within the expected parameters for cis complexes
together with the platinum-195 and tin-119/117 satel-
lites, and the data are listed in Table 2. For example,
the 31P-NMR spectrum of cis-[PtMe(SnMe3)(PPh3)2] in
dichloromethane at ca. −40°C consists of two princi-
pal doublets, relating to the non-equivalent phosphorus
atoms, both having platinum and tin satellites in a cis
The reaction of SnCl4 with [Pt(COD)2] gives complex
6, i.e. [PtCl(SnCl3)(COD)], which can also be prepared
by treating SnCl2 with an equimolar quantity of
[PtCl2(COD)] [9]. The 119Sn-NMR spectrum of complex
6 showed a rather large 195Ptꢀ119Sn coupling constant,
i.e. 26 208 Hz (Seddon et al. observed a lower value:

Table 1
Characterisation data for complexes containing PtꢀSn bonds with COD ligand
Seq.
Complex
Colour
m.p. (°C)
Analysis (Found (Calc.) (%))
IR a data (cm−1
)
1H-NMR b data (l ppm and J Hz)
119Sn-NMR data
(l ppm and J Hz)
/
C
H
Cl
w(PtꢀCl)
w(SnꢀCl)
295–262 s
310, 265 s
l Me
3J(PtCH)
2J(SnCH)
l Sn
J(SnPt)
1
2
[PtPh(SnPh2C Off white
l)(COD)]
[PtPh(SnPhCl Yellow
120–124 dec. 46.0 (45.5)
4.0 (4.0)
3.5 (3.4)
5.4 (5.2)
11.0 (11.0)
82–86 dec.
87–88
36.8 (37.1)
26.4 (26.3)
2)(COD)]
–orange
3
[PtCl(SnMe3) Yellow
4.1 (4.2)
330 m
0.45
9.5
48
(COD)]
4
5
6
[PtCl(SnMe2C Yellow
l)(COD]
[PtMe(SnMe3 Yellow
)(COD)]
79–80
Oil
22.7 (22.9)
–
3.6 (3.5)
–
335 m
–
280 s
–
1.0
5.0
48
−98.7
13 125
26 208
0.5 d
13 d
42 d
590
[PtCl(SnCl3) Yellow
152–154 dec. 17.2 (17.0)
2.2 (2.2)
325 c
s
325 c
s
−126.8
(
(COD)]
–orange
2
a Spectra recorded, using KBr disc, m, medium and s, strong bands.
b Spectra recorded in C6D6, using C6H6 as a reference at l 7.2 ppm.
c Not well-resolved broad peak.
d Data for the methyl group attached to platinum, l (Me) 1.47 ppm, 2J(PtCH) 64 Hz.

Table 2
31P{1H}-NMR data l (ppm) and J (Hz) for complexes containing PtꢀSn bonds a
Complex
−l P(A) trans to Sn
1J(PtPA)
2J(SnPA)
119Sn
−l P(B) cis to Sn
1J(PtPB)
2J(SnPB)
2J(PAPB)
117Sn
1610
119Sn
117Sn
cis-[PtCl(SnMe3)(PPh3)2] b
trans-[PtCl(SnMe3)(PPh3)2] b
trans-[PtCl(SnMe3)(PBu3)2] c
[PtCl(SnMe3)(DPPE)] d
105.7
110.6
132.4
91.0
125.2
108.4
89
179.7
88.7
89.3
86.8
91.6
81.9
119.5
91.1
91.3
94.7
1946
2959
2529.3
1785
2063
2061
3076.2
1440.4
1920
2102
2358
2932
2190
2839
2507
2193
1747
1683
117.6
4516
84.3
115
12.4
f
f
/
139
183
215
120
149
161
f
1902
1995
1846
2426.8
1280
1719
1914
1765
96.0
127.5
114.1
80.6
161.2
86.1
97.0
88.3
90.8
4070
2102
2227
3654.7
1536
1883
3839
1826
1835
95
cis-[PtMe(SnMe3)(PEt3)2] b
cis-[PtMe(SnMe3)(PPh3)2] b
cis-[PtMe(SnMe3){P(OPh)3}2] b,c
[PtMe(SnMe3)(DPPM)] b
[PtMe(SnMe3)(DPPE)] b
17.0
14.7
27.0
24.4
f
f
154
2336.4
1168
f
124.5
138
92
105
148
1842 f
2219
[PtCl(SnMe2Cl)(DPPE)2] d
[PtMe(SnMe2Cl)(DPPE)] d,e
[PtPh(SnPhCl2)(DPPE)] d
[Pt(SnMe3)2(DPPE)] d
2317
2316
2877
1553
3.7
5.0
4.9
f
f
f
2227
2754
1474.6
153.9
123.6
106
129.4
116
95
trans-[PtPh(SnPhCl2)(PPh3)2] c
[PtPh(SnPh2Cl)(DPPE)] d,e
[PtPh(SnPh3)(DPPE)] d,e
197.8
130
f
2365
1942
1658
2262
1852
1589
90.5
92.0
86.6
1866
1792
2590
3.6
3.7
6.0
f
590
[Pt(CꢁCPh)(SnMe3)(DPPE)] d,e
)
a Data obtained using CH2Cl2 as a solvent. External references, TMP for r.t. and TMPO for low temperature.
b Complex prepared and spectrum recorded at −70°C.
2
c Complex prepared and spectrum recorded in toluene at −40°C.
d Complex prepared and spectrum recorded at r.t.
e Complex prepared by method other than displacement of COD (see text).
f Not well resolved Sn(119) and Sn(117) satellites.

T.A.K. Al-Allaf / Journal of Organometallic Chemistry 590 (1999) 25–35
29
and trans relationship to phosphorus. The parameters
were in agreement with those expected for such a
complex (Table 2). The 1H-NMR spectrum of this
complex in CD2Cl2 at ca. −20°C showed a resonance
at l −0.35 ppm for the SnMe3 group protons, associ-
ated with platinum and tin satellites, and a resonance
for the PtꢀMe protons, split into four lines by the two
non-equivalent phosphorus atoms, the four lines being
accompanied by weak platinum satellites. The com-
plex was isolated from cold solution as a yellow
powder. It is stable at room temperature (r.t.), and
analysed to give the correct analytical figures (Table
3). All the complexes listed in Scheme 2 represent
novel platinum complexes that could not be prepared
by the direct reaction of SnMe4 and Pt(0) complexes
containing phosphine ligands. The statement by Steele
and co-workers is an exception [8]. In their work,
SnMe4 reacts with [Pt(PEt3)4] in benzene under reflux
for ca. 5 h to give cis-[PtMe(SnMe3)(PEt3)2] but no tin
satellites were observed and the complex was not
isolated. In the absence of full characterisation, there
is some doubt, therefore, that this complex would in
fact be formed under their conditions [8]. We there-
fore, decided to prepare the complex cis-
[PtMe(SnMe3)(PEt3)2] by reacting [PtMe(SnMe3)-
(COD)] with PEt3 in CH2Cl2 at ca. −40°C (Scheme
2) and to record the 31P-NMR spectrum. This re-
vealed very clearly the presence of the correct complex
(Table 2). We found that this complex is unstable in
solution at ambient temperature and hence Steele and
co-workers [8] had been wrong in their assignments.
Treatment of complex 3 (Scheme 1), [PtCl(SnMe3)-
(COD)], with PPh3, PBu3, and DPPE in CH2Cl2 at ca.
−70°C gave the corresponding phosphine complexes,
i.e. cis- and trans-[PtCl(SnMe3)(PPh3)2], trans-
[PtCl(SnMe3)(PBu3)2] and [PtCl(SnMe3)(DPPE)], re-
spectively. The 31P-NMR spectral data of these
complexes (Table 2) were commensurate with the
expected structures [5]. Earlier workers suggested that
cis-[PtCl(SnMe3)(PPh3)2] could be obtained from
SnMe3Cl and [Pt(PPh3)3] (see Ref. [1]), however
Eaborn and co-workers [4] found that this was incor-
rect. After treating SnMe3CI with the more conve-
nient Pt(0) complex, i.e. [Pt(C2H4)(PPh3)2], they found
that cis-[PtMe(SnMe2Cl)(PPh3)2] was formed. We
have previously suggested that the reaction of
SnMe3Cl with [Pt(C2H4)(PPh3)2] leads initially to cis-
[PtCl(SnMe3)(PPh3)2], which then converts into the
thermodynamically more stable cis-[PtMe(SnMe2Cl)-
(PPh3)2] via the formation of a Pt(IV) intermediate
[11]. Details about this mechanism will be published in
a
future article. However the complex cis-
[PtCl(SnMe3)(PPh3)2] was isolated at −70°C as a
yellow crystalline product, and characterised by its
elemental analysis and IR spectrum (Table 3). This
complex is prepared for the first time and cannot be

30
T.A.K. Al-Allaf / Journal of Organometallic Chemistry 590 (1999) 25–35
obtained by the direct reaction of SnMe3CI and
[Pt(PPh3)n] (n=3, 4) or [Pt(C2H4)(PPh3)2], due to its
unstability in solution at temperatures close to r.t.
The complex [PtCl(SnMe3)(DPPE)] was first sug-
gested by Clemmit and Glockling [12] to be obtained
from the reaction of SnMe3H and [PtCl2(DPPE)] as a
white powder. We decided to prepare this complex by
treating [PtCl(SnMe3)(COD)] with DPPE in dichloro-
methane at low temperature. The 31P-NMR spectrum
of the product revealed the presence of one cis complex
having the parameters shown in Table 2. In order to
compare the properties of our product with those previ-
ously reported, we isolated the complex [PtCl(SnMe3)-
(DPPE)] from the mixture as a yellow crystalline
product (Table 3). As the two sets of data were differ-
ent, we [13] repeated the procedure of the earlier work-
ers and the product obtained was examined by
31P-NMR. It seems possible therefore that Clemmit and
Glockling [12] may have obtained the complex
[PtMe(SnMe2Cl)(DPPE)] (Table 2), which of course,
has the same elemental composition as the complex
[PtCl(SnMe3)(DPPE)].
The complex [PtCl(SnMe2Cl)(COD)] reacts with ter-
tiary phosphines, e.g. PPh3, PEt3, PBu3 to yield known
complexes. Treatment with DPPE or bipy in
dichloromethane at ambient temperature leads to for-
mation of the new complexes [PtCl(SnMe2Cl){(DPPE)
or (bipy)}], which could not be prepared by other
routes, e.g. from Me2SnCl2 and [Pt(DPPE)2] or from
[PtCl(SnMe2Cl)(PPh3)2] and DPPE. However, the com-
plexes were isolated and fully characterised (Table 3).
The reaction of [PtPh(SnPh2Cl)(COD)] with PPh3 at
or below r.t. yields the known complex cis-
[PtPh(SnPh2Cl)(PPh3)2] [8]. Using DPPE in CH2Cl2 at
r.t., the reaction gave a complex with 31P-NMR
parameters (Table 2) identical to those of
[PtPh(SnPh2Cl)(DPPE)]. This complex was isolated and
characterised (Table 3). The reaction of [PtPh-
(SnPhCl2)(COD)] with PPh3 in CH2Cl2, at −70°C or at
r.t., gave the known complex cis-[PtPh(SnPhCl2)-
(PPh3)2] [4]. An in situ reaction between [Pt(COD)2] and
SnPh2Cl2 in toluene at ca. −40°C for ca. 60 min was
carried out in the hope of obtaining [PtCl(SnPh2Cl)-
(COD)], the toluene then being evaporated off while the
temperature was maintained below −40 to −10°C.
The residue was dissolved in CH2Cl2 at −40°C and
PPh3 added and the 31P-NMR spectrum was recorded
at −40°C, which revealed the presence of cis- (53%)
and trans- (47%) [PtPh(SnPhCl2)(PPh3)2] The complex
cis-[PtCl(SnPh2Cl)(PPh3)2] could not be detected. It
seems that the trans-[PtPh(SnPhCl2)(PPh3)2], which it
observed for the first time (Table 2), is stable in solu-
tion only at low temperature, for when the solution
containing this complex was allowed to warm up, the
proportion of the trans complex gradually fell and it
was completely converted into the cis isomer at r.t.
Furthermore, treatment of [PtPh(SnPhCl2)(COD)]
with DPPE in CH2Cl2 at r.t. leads to formation of the
new complex [PtPh(SnPhCl2)(DPPE)], which again
could not be prepared by other routes, i.e. SnPh2Cl2
and [Pt(DPPE)2] or [PtPh(SnPhCl2)(PPh3)2] and DPPE.
It was isolated and fully characterised (Tables 2 and
3).
The reaction of [PtCl(SnCl3)(COD)] with tertiary
phosphines leads to known complexes that can be
prepared from the direct reaction of SnCl4 and Pt(0)
complexes.
2.3. Decomposition of [PtCl(SnMe3)(COD)] and its
PPh3 analogue
It is evident that the complex [PtCl(SnMe3)(COD)] is
thermally unstable at r.t., and its decomposition prod-
ucts were studied carefully by using 31P-NMR spec-
troscopy after adding phosphine.
Two samples of [PtCl(SnMe3)(COD)] (0.1 g, 0.2
mmol) were kept for 4 days, one at −25°C and the
other at r.t. Each was then dissolved in CH2Cl2, the
solution cooled to −70°C, a pre-cooled solution to
−70°C of PPh3 (0.1 g, 0.4 mmol) in CH2Cl2 added, and
the 31P-NMR spectrum recorded. The spectrum (at
−70°C) from the sample kept at −25°C, revealed the
presence of cis-[PtCl(SnMe3)(PPh3)2] (A) (62%) and
trans-[PtCl(SnMe3)(PPh3)2] (B) (38%) (Scheme 3). The
spectrum (at −70°C) of the sample kept at r.t. revealed
the presence of three known complexes: A, B, cis-
[PtMe(SnMe2Cl)(PPh3)2] (C) (43, 13 and 22%, respec-
tively), and an unknown complex (D) (22%) (Scheme 3)
having the parameters: l −105.2 ppm, J(PtP) 2075.2
Hz (P cis to Sn); l −114.1 ppm, J(PtP) 2131.3 Hz (P
trans to Sn); 2J(PꢀPtꢀP) 10 Hz. Both signals were
associated with tin satellites; those in cis relationship to
phosphorus, 2J(SnP) 103 Hz, and those in a trans
relationship to phosphorus being obscured by the other
lines. Product D was found to be thermally very un-
stable, for when the mixture was warmed to −60°C,
the proportion of it decreased by ca. 50% and it had
totally disappeared at −50°C. When both samples
were warmed to r.t., only complex C (the thermody-
namically stable species) was observed (Scheme 3).
A sample of [PtCl(SnMe3)(COD)] was prepared and
stored at r.t. under argon for 1 week then dissolved in
CH2Cl2. The solution was cooled to −70°C and PPh3
was added (as above). This again gave a mixture of the
three known complexes: A, B and C (22, 6, and 45%,
respectively) and complex D (27%).
A sample of [PtCl(SnMe3)(COD)] was prepared and
stored at r.t. under argon for 5 weeks, then dissolved in
CH2Cl2. The solution was cooled to −70°C and
treated with PPh3 (as above). The 31P-NMR spectrum
revealed the presence of a mixture of complex C
(47.5%), a complex (16%) having the parameters l

T.A.K. Al-Allaf / Journal of Organometallic Chemistry 590 (1999) 25–35
31
Scheme 3. Products formed from the reaction of [PtCl(SnMe3)(COD)] (stored at −25°C once and at r.t. for another 4 days) with PPh3 at −70°C,
and at r.t.
greater the number of decomposition products. Further
studies concerning the mechanisms of such reaction will
be published later.
−112.5 ppm, J(PtP) 1919 Hz, identified as cis-
[PtMe2(PPh3)2] [14], a complex (10%) having the
parameters l −109.2 ppm, J(PtP) 3120 Hz, identified
as trans-[PtMeCl(PPh3)2] [15], and complex D (26%)
(Scheme 3); no cis- or trans-[PtCl(SnMe3)(PPh3)2] was
detected in the mixture.
2.4. Decomposition of cis-[PtMe(SnMe3)(PPh3)2]
In order to study the decomposition products of
[PtCl(SnMe3)(COD)], without having the trans com-
plexes, DPPE was used instead of PPh3. A sample of
[PtCl(SnMe3)(COD)] was stored at r.t. for ca. 2 weeks,
then dissolved in CH2Cl2, and the solution was cooled
to −70°C and treated with DPPE (as above). The
31P-NMR spectrum recorded at −70°C revealed (in
addition to the unreacted DPPE), the presence of three
complexes (Scheme 4). Complex A (15%) identified as
[PtMe(SnMe2Cl)(DPPE)] (Table 2), complex B (42.5%)
having the parameters l −92.8 ppm, J(PtP) 1814 Hz,
identified as [PtMe2(DPPE)] [16], and an unknown
complex C (21.5%) having the parameters l −73.0
ppm, J(PtP) 2329 Hz, l −80.8 ppm, J(PtP) 2977 Hz,
accompanied by tin satellites, those in a cis relationship
Two samples of cis-[PtMe(SnMe3)(PPh3)2] were pre-
pared by treating [PtMe(SnMe3)(COD)] with two molar
equivalents of PPh3 in CH2Cl2 at −70°C. The first was
2
to phosphorus having J(SnꢀP) 90 Hz and those in a
trans relationship being obscured by the signals of other
complexes. The PP coupling was very small and could
not be resolved. Again, when the mixture was warmed
to r.t., complex C (Scheme 4) completely disappeared
and the complexes D and E appeared.
As
a conclusion, it seems that the complex
[PtCl(SnMe3)(COD)] decomposes in the solid state at
r.t. to give [PtMe(SnMe2Cl)(COD)] via an unknown
intermediate, the extent of decomposition increases
with time, and the longer the complex is stored the
Scheme 4. Products formed from the reaction of [PtCl(SnMe3)(COD)]
(stored at r.t. for 2 weeks) with DPPE at −70°C, and at r.t.

32
T.A.K. Al-Allaf / Journal of Organometallic Chemistry 590 (1999) 25–35
allowed to warm gradually and the 31P-NMR spec-
trum was recorded at 10°C intervals. No change oc-
curred over the range −70 to −10°C, but the
spectrum at 0°C comprised resonances from the origi-
nal complex (70%) and from a new complex (15%) {l
−90.5 ppm, J(PtP) 4465 Hz} identified as [Pt(PPh3)3]
[17,18], in addition to cis-[PtMe2(PPh3)2] [14], which
was present in the spectrum from the start (above).
When the sample was warmed to r.t., the solution
turned brown and the proportion of [Pt(PPh3)3] grew
to 60%, while that for the original compound was
reduced to 25%. When the sample was allowed to
stand at r.t. for a further ca. 30 min, the spectrum
showed that the original complex had completely dis-
appeared. The second sample was warmed rapidly
to r.t., and the 31P-NMR spectrum recorded during
20 min showed only the presence of [Pt(PPh3)3]. For
this sample, the 1H-NMR was recorded to show
a resonance at 0.07 ppm, associated with tin satellites,
2J(SnCH) 51 Hz; this was attributed to SnMe4, and
the assignment was confirmed by addition of SnMe4,
which caused an increase in the height of the
signal.
It appears therefore, that decomposition of cis-
[PtMe(SnMe3)(PPh3)2] in the presence of PPh3 does not
give [Pt(PPh3)3] as was observed from the decomposi-
tion in the absence of PPh3.
Another sample of cis-[PtMe(SnMe3)(PPh3)2] pre-
pared, as above, in toluene at −70°C was saturated
with ethylene. The 31P-NMR showed no change had
occurred at −70°C, or up to −30°C, but when the
ethylene was slowly bubbled into solution while the
temperature was allowed to rise to r.t., the solution
turned brown. The spectrum recorded at −50°C re-
vealed
the
presence
of
two
complexes:
[Pt(C2H4)(PPh3)2] (73%) l −106.6 ppm, J(PtP) 3711
Hz and [Pt(C2H4)2(PPh3)] (27%), l −116.3 ppm,
J(PtP) 3388.7 Hz; [15] l −116.0 ppm, J(PtP) 3425 Hz.
The formation of the first complex can be understood
as a result of the initial decomposition of cis-[PtMe-
(SnMe3)(PPh3)2] to [Pt(PPh3)2] followed by combination
with ethylene to give [Pt(C2H4)(PPh3)2]. The formation
of the second complex can possibly be understood as a
result of the initial decomposition of [PtMe(SnMe3)-
(COD)] that was left unreacted with a sufficient quan-
tity of PPh3; when this decomposes in the presence of
ethylene it gives [Pt(C2H4)3], and this has been shown to
react with [Pt(C2H4)(PPh3)2] in the presence of ethylene
to give [Pt(C2H4)2(PPh3)].
It is concluded that cis-[PtMe(SnMe3)(PPh3)2] is un-
stable in solution at temperatures somewhat below
0°C, and decomposes:
This was confirmed by the two following experi-
ments: (a) ethylene was bubbled into a toluene solution
of [Pt(C2H4)(PPh3)2] for several minutes at r.t., and the
31P-NMR spectrum indicated that no change had oc-
curred. (b) When a mixture of [Pt(C2H4)(PPh3)2] and a
slight excess of [Pt(COD)2] was dissolved in toluene, the
31P-NMR spectrum gave no indication of change, al-
though the solution had turned brown. When ethylene
was bubbled into this solution (or into a similar mix-
ture freshly prepared), for ca. 2 min, the solution
turned dark brown, and the spectrum revealed the
presence of [Pt(C2H4)2(PPh3)] only.
3cis-[PtMe(SnMe3)(PPh3)2]
“2[Pt(PPh3)3]+3SnMe4+Pt
Similarly, Abis et al. [19] observed the formation of
[Pt(PPh3)3] when a solution of cis-[PtHMe(PPh3)2] pre-
pared at −80°C, was warmed to −25°C:
3cis-[PtHMe(PPh3)2]“2[Pt(PPh3)3]+3CH4+Pt
A sample of cis-[PtMe(SnMe3)(PPh3)2] (93.5%) was
prepared in situ from [PtMe(SnMe3)(COD)] and ex-
actly two molar equivalents of PPh3 in CH2Cl2 at
−70°. The remaining 6.5% was cis-[PtMe2(PPh3)2] and
no free PPh3 was observed in the spectrum. An excess
of PPh3 (1.5 molar equivalents) was added to the
solution at −60°C and the 31P-NMR showed no
change even on warming the solution to +10°C. At
r.t., the spectrum was recorded during ca. 30 min and
showed the presence of PPh3, traces of the original
complex and two new complexes in an almost 1:1
molar ratio. These have the parameters (a) l −109.6
ppm, J(PtP) 3342 Hz and (b) l −110.2 ppm, J(PtP)
3320 Hz; neither resonance was associated with tin
satellites. The parameters do not correspond to any of
cis-[PtMe2(PPh3)2] [14], trans-[PtXY(PPh3)2] X=Me,
Y=Cl [15]; X=H, Y=Cl [20]; X=CH2CI, Y=Cl
[21] or cis- or trans-[PtCl2 (PPh3)2] [22]. One of the
complexes may be the trans-[PtMe2 (PPh3)2] (parame-
ters not available in the literature). No further investi-
gations were carried out on these complexes.
These results are consistent with the following
equations:
[Pt(COD)2]+3C2H4“[Pt(C2H4)3]+2COD
[Pt(C2H4)3]+[Pt(C2H4)(PPh3)2]“2[Pt(C2H4)2(PPh3)]
This represents a superior method for the prepara-
tion of [Pt(C2H4)2(PPh3)] in comparison with that re-
ported earlier [23]. It should be noted that the
preparation should be carried out at low temperatures
to avoid decomposition.
3. Experimental
3.1. General
All the solvents were dry and oxygen-free, and
reactions were carried out under dry nitrogen or dry

T.A.K. Al-Allaf / Journal of Organometallic Chemistry 590 (1999) 25–35
33
1
argon. The H-NMR spectra were recorded on a 90
0.49 mmol) in toluene (8 ml) at r.t. The mixture was
stirred for ca. 30 min then filtered through Celite, and
the filtrate was reduced in volume to ca. 0.5 ml. n-Hex-
ane (3 ml) was added, and the solution was decanted
from the yellow crystals, which were washed with hex-
ane (3×3 ml), and dried under vacuum (yield, 0.2 g,
80%).
MHz Perkin–Elmer R32 spectrometer using SiMe4 as
internal reference where necessary. The proton
-decoupled FT 31P-NMR spectra were recorded at
40.48 MHz on a Jeol PFT-100 spectrometer using
trimethylphosphine (TMP) or trimethylhosphate
(TMPO) as external references. The proton-decoupled
FT 119Sn-NMR spectra were recorded at 33.34 MHz on
a Jeol FX-90Q spectrometer using SnMe4 as external
reference. The tin spectra were performed by Dr W.
McFarlene and Dr B.V. Cheesman at the City of
London Polytechnic in early 1980.
The IR spectra were recorded as Nujol mull smears
between CsI discs on a Perkin–Elmer 457 or 597
grating infrared spectrometer. Elemental analyses were
carried out at the microanalytical laboratory at the
School of Molecular Sciences, Sussex University,
Brighton, UK.
3.3.3. [PtMe(SnMe3)(COD)]
An excess of SnMe4 was added to a solution of
[Pt(COD)2] (0.2 g, 0.49 mmol) in toluene (5 ml) under
argon. The mixture was kept for ca. 16 h at r.t., during
which it turned yellow–brown. It was filtered through
Celite and the filtrate was taken to dryness and kept
under vacuum for ca. 2 h. The product was obtained as
yellow oil, and many unsuccessful attempts were made
to crystallise it. The complex was found to decompose
readily at r.t. to metallic platinum, but it is wholly
satisfactory for immediate use. It can also be stored
safely at ca. −25°C for a long time.
3.2. Starting materials
3.3.4. [PtPh(SnPh2Cl)(COD)]
K2PtCl4, PtCl2, cycloocta-1,5-diene (COD) and cy-
cloocta-1,3,5,7-tetraene (COT) were commercial prod-
ucts. COD and COT were distilled under nitrogen
before use. The tertiary phosphines PEt3, PPh3,
P(OPh)3, Ph2PCH2PPh2 (DPPM), Ph2PCH2CH2PPh2
(DPPE), … etc. and other neutral ligands were either
obtained commercially or prepared by standard meth-
ods. The organotin(IV) compounds SnRxCl4−x, R=
Me, Ph and x=4–0, were either commercial products
or prepared by standard methods. The platinum com-
plexes used in this study were prepared by standard
methods: [PtCl2(COD)] [24], [Pt(COD)2] [25] and
[Pt(C2H4)(PPh3)2] [26].
A solution of [Pt(COD)2] (0.100 g, 0.24 mmol) in
benzene (4 ml), was added dropwise under nitrogen to
a solution of SnPh3Cl (0.094 g, 0.24 mmol) in benzene
(6 ml) at r.t.; the mixture turned yellow soon after the
first few drops were added. The mixture was stirred for
ca. 15 min, then reduced in volume to ca. 2 ml, and
n-hexane was added dropwise to precipitate the uniden-
tified brown material (possibly decomposition prod-
ucts). The solution was filtered through Celite and the
clear yellow filtrate was reduced in volume to ca. 0.5
ml. n-Hexane (3 ml) was added and the solution was
cooled to ca. −10°C, then the liquid was decanted
from the off-white crystals, which were washed with
hexane (3×2 ml) then dried in vacuo for ca. 1 h (yield,
0.100 g, 60%).
3.3. Preparation of complexes
The complex [PtPh(SnPhCl2)(COD)] was prepared
similarly from equimolar quantities of [Pt(COD)2] and
SnPh2Cl2 in benzene.
3.3.1. [PtCl(SnMe3)(COD)]
To a solution of SnMe3Cl (0.220 g, 1.1 mmol) in
toluene (2 ml), a solution of [Pt(COD)2] (0.411 g, 1.0
mmol) in toluene (10 ml) was added at r.t. The mixture
was stirred for ca. 30 min, and the yellow solution was
filtered through Celite and reduced in volume to 0.5 ml.
n-Hexane (3 ml) was added at 0°C and the solution was
decanted from the crystalline product, which was
washed with hexane (3×3 ml), and dried under vac-
uum to give pale yellow fine crystals of the product
(0.379 g, 75%). This complex is unstable in the solid
state at r.t., but can be safely kept at −25°C for
several months without decomposition.
3.3.5. [PtCl(SnCl3)(COD)]
This was prepared by two methods: (a) a solution of
[Pt(COD)2] (0.20 g, 0.49 mmol) in toluene (8 ml) was
added gently to a solution of SnCl4 (0.15 g, 0.58 mmol)
in toluene (2 ml) under nitrogen. An immediate precip-
itate separated; this was filtered off, washed with n-hex-
ane and dried in vacuo to give yellow–orange crystals
of the product (0.20 g, 73%).
(b) A mixture of [PtCl2(COD)] (0.20 g, 0.53 mmol)
and anhydrous SnCl2 (0.10 g, 0.53 mmol) was sus-
pended in dichloromethane (15 ml) and the mixture was
stirred for ca. 2 h at r.t. The suspension was reduced in
volume to ca. 5 ml, then the solid was separated by
filtration, washed with hexane, and dried in vacuo, to
give a yellow–orange product (0.26 g, 95%).
3.3.2. [PtCl(SnMe2Cl)(COD)]
A solution of SnMe2Cl2(0.1 g, 0.46 mmol) in toluene
(2 ml) was treated with a solution of [Pt(COD)2] (0.2 g,

34
T.A.K. Al-Allaf / Journal of Organometallic Chemistry 590 (1999) 25–35
3.3.6. cis-[PtCl(SnMe3)(PPh3)2]
3.4. NMR tube in situ reactions
Freshly prepared [PtCl(SnMe3)(COD)] (0.1 g, 0.20
mmol) was dissolved in dichloromethane (0.5 ml) and
the solution was cooled to ca. −70°C in an acetone–
dry ice bath. A solution of PPh3 (0.1 g, 0.38 mmol) in
dichloromethane (0.3 ml) was added at ca. −70°C and
the mixture was shaken for ca. 60 s to ensure homo-
geneity. A few drops of n-hexane were added to the
point of turbidity, and within ca. 30 min yellow crystals
began to separate. After a further 30 min the superna-
tant liquid was decanted from the crystals, which was
washed with n-hexane (3×1 ml) at ca. −70°C and
dried in vacuo to give fine pale yellow crystals of the
product.
3.4.1. Tertiary phosphine with COD complexes
3.4.1.1. Low-temperature reaction. A typical reaction,
between PPh3 and [PtCl(SnMe3)(COD)] is described.
The latter (0.1 g, 0.20 mmol) was dissolved in
dichloromethane (0.5 ml) under nitrogen and the solu-
tion placed in an 8 mm NMR tube flushed with nitro-
gen. The tube was then sealed with a rubber subaseal
and cooled to ca. −70°C in an acetone–dry ice bath.
The PPh3 (0.1 g, 0.38 mmol) was dissolved in
dichloromethane (0.3 ml) and the solution was carefully
injected through the subaseal cap, so that drops of the
liquid fell first on to the cold inside of the tube; in this
way the two solutions were mixed at −70°C. The
mixture was shaken carefully, then the 31P-NMR spec-
trum recorded at −70°C.
The complex [PtCl(SnMe3)(DPPE)] was prepared
similarly, from [PtCl(SnMe3)(COD)] (0.20 g, 0.40
mmol) and DPPE (0.14 g, 0.35 mmol) in toluene (3 ml)
at ca. −20°C, as a yellow powdered product.
The reaction between [PtCl(SnMe3)(COD)] and PBu3
or PEt3 was carried out analogously, but by using
toluene at ca. −40°C.
A similar procedure was carried out for the reactions
between [PtMe(SnMe3)(COD)] and PPh3, PEt3, DPPM,
DPPE in dichloromethane at −70°C. With P(OPh)3
the reaction was carried out in toluene at −40°C.
3.3.7. cis-[PtMe(SnMe3)(PPh3)2]
A mixture of [Pt(COD)2] (0.1 g, 0.24 mmol) and an
excess of SnMe4 in toluene (8 ml) was left aside at r.t.
for ca. 16 h. The mixture was then filtered through
Celite and the yellow filtrate was reduced in volume to
ca. 2 ml, then cooled to ca. −50°C in an acetone–dry
ice bath. A solution of PPh3 (0.1 g, 0.38 mmol) in
toluene (0.5 ml) was added at −50°C, and the mixture
was shaken for ca. 60 s. n-Hexane was added to the
point of turbidity, and a yellow solid separated. The
supernatant liquid was decanted from the solid, which
was washed with hexane (3×2 ml) at −50°C and
dried in vacuo to give the final product as a yellow
powder.
3.4.1.2. Room-temperature reactions. A typical reaction,
between [PtCl(SnMe2Cl)(COD)] and PPh3 was carried
out as follows. The [PtCl(SnMe2Cl)(COD)] (0.1 g, 0.20
mmol) was dissolved in dichloromethane (0.5 ml) in an 8
mm NMR tube under nitrogen. A solution of PPh3 (0.1
g, 0.38 mmol) in dichloromethane (0.3 ml) was introduced
into the NMR tube under nitrogen and the mixture was
shaken for ca. 30 s. The 31P-NMR spectrum was then
recorded.
The reaction between [PtCl(SnMe2Cl)(COD)] and
DPPE was carried out in the same way. With PBu3 and
PEt3, the reactions were carried out in toluene.
A similar procedure, with toluene as solvent, was used
for the reactions between [PtCl(SnMe3)(COD)] and
DPPE, [PtPh(SnPh2Cl)(COD)] or [PtPh(SnPhCl2)-
(COD)] and PPh3 or DPPE and {[PtCl(SnCl3)(COD)] and
PBu3}.
3.3.8. [PtPh(SnPh2Cl)(DPPE)]
The [PtPh(SnPh2Cl)(COD)] (0.14 g, 0.2 mmol) was
dissolved in dichloromethane (2 ml) and a solution of
DPPE (0.08 g, 0.2 mmol) in dichloromethane (1 ml)
was added. The mixture was shaken for ca. 60 s and
n-hexane was added to precipitate the product. The
solid was crystallised from dichloromethane–hexane
and dried under vacuum to give white crystals of the
product.
The complexes [PtPh(SnPhCl2)(DPPE)] and [PtCl-
(SnMe2Cl)(DPPE)] were obtained analogously as pale
yellow crystalline products.
3.4.2. Reaction between cis-[PtRR%(PPh3)2] and DPPE
The complex cis-[PtRR%(PPh3)2] (R=Ph, R%=
SnPh3, SnPh2Cl; R=Me, R%=SnMe2Cl) (0.2 mmol)
(prepared as described in Ref. [4]) was dissolved in
dichloromethane (5 ml) at r.t. and DPPE (0.2 mmol)
was added. After ca. 5 min the solution was reduced in
volume to ca. 1 ml and the 31P-NMR spectra recorded.
Attempts were made to obtain a similar complex
from the reaction between cis-[PtPh(SnPhCl2)(PPh3)2]
and DPPE but were unsuccessful even at −30°C, as
were those between cis- and trans-[PtCl(SnMe2Cl)-
(PPh3)2] and DPPE, but at r.t.
3.3.9. [PtCl(SnMe2Cl)(bipy)]
The [PtCl(SnMe2Cl)(COD)] (0.10 g, 0.20 mmol) was
dissolved in toluene (6 ml) and bipyridine (0.07 g, 0.45
mmol) was added at r.t. The mixture was stirred for ca.
30 min, during which a yellow crystalline complex
separated. This was filtered off, washed with n-hexane
(3×3 ml), and dried in vacuo for ca. 1 h to give a
yellow crystalline product.

T.A.K. Al-Allaf / Journal of Organometallic Chemistry 590 (1999) 25–35
35
Acknowledgements
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