Reactions of organotin(IV) compounds with platinum complexes. Part(III). Reactions of (R2Sn)n, (R = Me or Ph, n = 6; R = Et, n = 9) with platinum complexes

Article abstract of DOI:10.1016/S0022-328X(02)01331-1

The R₂Sn moieties formed when the cyclic compounds (R₂Sn)_n, R = Me or Ph, n = 6; R = Et, n = 9, are exposed to light, react with the platinum(II) complexes [PtCl₂L₂], L = PEt₃, PPr₃, PBu₃, PEtPh₂, PPh₃ to give new complexes of the general formula [PtCl(SnR₂Cl)L₂]. Similarly, Et₂Sn from (Et₂Sn)₉ reacts with [PtMe(Cl)L₂] to give [PtMe(SnEt₂Cl)L₂] and Ph₂Sn from (Ph₂Sn)₆ reacts with [PtPh(Cl)L₂] or [PtPh₂L₂] to give [PtPh(SnPh₂Cl)L₂] or [PtPh(SnPh₃)L₂] (L = PEt₃), respectively. Reactions involving (R₂Sn)_n and the bridged complex [{Pt(μ-Cl)ClL}₂] give a mixture of [PtCl(SnR₂Cl)L₂] and [PtCl(SnRCl₂)L₂], R = Me or Et, L = PBu₃. It is suggested that these reactions initially involve insertion of R₂Sn moieties into Pt-Cl bonds of the complexes [PtX(Cl) L₂] or [{Pt(μ-Cl)ClL}₂] then generate R₂SnXCl (X = Cl, Me, Ph) and the Pt(0)complex [PtL₂], which undergoes oxidative-addition of the formed tin(IV) species to give complexes containing Pt-Sn bonds. With (Ph₂Sn)₆ and [PtPh₂L₂], the mechanism takes a different course. Reactions under similar conditions involving the Pt(0) complexes [Pt(C₂H₄(PPh₃)₂] or [Pt(COD)₂], (COD = 1,5-cyclooctadiene) and (R₂Sn)₆, R = Me or Ph, gave no detectable complexes containing Pt-Sn bonds. The complex [Pt(PEt₃)₄] and (MeSn)₆ likewise gives no species containing Pt-Sn bonds but with (Ph₂Sn)₆, two complexes, tentatively identified as trans-[PtPh(Sn₂Ph₅)(PEt₃)₂] and trans-[PtPh(Sn₆Ph₁₁)(PEt₃)₂], were detected in the solution. In all cases, the products were identified by ³¹P-NMR spectroscopy.

Full text of DOI:10.1016/S0022-328X(02)01331-1

Journal of Organometallic Chemistry 654 (2002) 21Á28
/
www.elsevier.com/locate/jorganchem
Reactions of organotin(IV) compounds with platinum complexes.
9)
Part(III). Reactions of (R2Sn)n, (Rꢀ
/
Me or Ph, nꢀ
/
6; Rꢀ
/
Et, nꢀ
/
with platinum complexesꢀ
Talal A.K. Al-Allaf *
Department of Chemistry, College of Basic Sciences, Applied Science University, Amman 11931, Jordan
Received 10 December 2001; received in revised form 8 February 2002; accepted 8 February 2002
Abstract
The R2Sn moieties formed when the cyclic compounds (R2Sn)n, Rꢀ
with the platinum(II) complexes [PtCl2L2], LꢀPEt3, PPr3, PBu3, PEtPh2, PPh3 to give new complexes of the general formula
[PtCl(SnR2Cl)L2]. Similarly, Et2Sn from (Et2Sn)9 reacts with [PtMe(Cl)L2] to give [PtMe(SnEt2Cl)L2] and Ph2Sn from (Ph2Sn)6
reacts with [PtPh(Cl)L2] or [PtPh2L2] to give [PtPh(SnPh2Cl)L2] or [PtPh(SnPh3)L2] (LꢀPEt3), respectively. Reactions involving
(R2Sn)n and the bridged complex [{Pt(m-Cl)ClL}2] give a mixture of [PtCl(SnR2Cl)L2] and [PtCl(SnRCl2)L2], RꢀMe or Et, Lꢀ
PBu3. It is suggested that these reactions initially involve insertion of R2Sn moieties into PtꢀCl bonds of the complexes [PtX(Cl) L2]
or [{Pt(m-Cl)ClL}2] then generate R2SnXCl (XꢀCl, Me, Ph) and the Pt(0)complex [PtL2], which undergoes oxidative-addition of
the formed tin(IV) species to give complexes containing PtꢀSn bonds. With (Ph2Sn)6 and [PtPh2L2], the mechanism takes a different
course. Reactions under similar conditions involving the Pt(0) complexes [Pt(C2H4)(PPh3)2] or [Pt(COD)2], (CODꢀ1,5-
cyclooctadiene) and (R2Sn)6, RꢀMe or Ph, gave no detectable complexes containing PtꢀSn bonds. The complex [Pt(PEt3)4] and
(MeSn)6 likewise gives no species containing PtꢀSn bonds but with (Ph2Sn)6, two complexes, tentatively identified as trans-
/
Me or Ph, nꢀ
/
6; Rꢀ
/
Et, nꢀ/9, are exposed to light, react
/
/
/
/
/
/
/
/
/
/
/
[PtPh(Sn2Ph5)(PEt3)2] and trans-[PtPh(Sn6Ph11)(PEt3)2], were detected in the solution. In all cases, the products were identified by
31P-NMR spectroscopy. # 2002 Elsevier Science B.V. All rights reserved.
Keywords: Organotin compounds; Stannylenes; Platinum complexes; 31P-NMR studies
1. Introduction
by exposing a mixture of the substrate and (R2Sn)n to
light. Corresponding insertions into SiꢀH, SiꢀO, and
SiꢀCl bonds take place with the transient silylene Me2Si
[7]. Stannylenes R2Sn (Rꢀalkyl or aryl) generated in
solution can co-ordinate to transition metals (M), Mꢀ
Cr, W and Fe [8Á10], in the presence of an electron
donating solvent such as pyridine or THF, to form
complexes containing MꢀSn bonds. Several articles
dealing with the formation of complexes containing
PtꢀM bonds (MꢀSn, Ge, Si) have been reported
/
/
The cyclic tin compounds (R2Sn)n are known to
generate the stannylenes R2Sn in solution upon expo-
sure to light at room temperature [2,3].These species can
be also formed by thermal disproportionation of 1,2-
disubstituted distannanes (R2SnX)2, which gives
SnR2X2 and R2Sn [4]. The transient R2Sn species can
/
/
/
/
/
undergo insertion into C-halogen, Oꢀ
/
O, Snꢀ
/
H, Snꢀ/C
/
/
and SnꢀSn bonds [5,6], the reactions being carried out
/
recently [11]. As an extention to our ongoing interest
in the synthesis of new platinum complexes containing
Ptꢀ
tin compounds (R2Sn)n, (Rꢀ
nꢀ9) with several platinum complexes, which to the
best of our knowledge is novel.
/
Sn bonds, we present here the reaction of the cyclic
ꢀ For Part II of this work, see Ref. [J. Organomet. Chem. 590 (1999)
25].
* Tel.: ꢁ
E-mail address: talal_al_allaf@hotmail.com (T.A.K. Al-Allaf).
/
Me or Ph, nꢀ6; RꢀEt,
/
/
/
/
962-6-523-7181; fax: ꢁ962-6-523-2899.
/
0022-328X/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved.
PII: S 0 0 2 2 - 3 2 8 X ( 0 2 ) 0 1 3 3 1 - 1

22
T.A.K. Al-Allaf / Journal of Organometallic Chemistry 654 (2002) 21Á28
/
2. Experimental
light from a tungsten lamp at ca. 90 8C. The results of
these reactions are summarised in Table 1. The 31P-
NMR spectrum of the concentrated solution obtained
from the reaction between trans-[PtCl2(PEt3)2] and
(Me2Sn)6 in benzene after ca. 24 h comprised a ca.
1:4:1 triplet with tin satellites (94%) together with the
signals from a small amount of the starting complex.
The values of d 15.0 ppm and J(PtP) 2390 Hz associated
with tin- 119 and -117 satellites (Table 2) were identical
to those for the complex trans-[PtCl(SnMe2Cl)(PEt3)2],
which has been prepared by three different methods
[1,25] (Scheme 1).
2.1. General
All the solvents were dry and oxygen-free, and
reactions were carried out under dry nitrogen or dry
argon. The proton-decoupled FT 31P-NMR spectra
were recorded at 40.48 MHz on a JEOL PFT-100
spectrometer with trimethylphosphite (TMP) or tri-
methylphosphate (TMPO) as external reference and
chemical shifts were corrected to H3PO4 as a reference
standard.
Similarly, the reaction of trans-[PtCl2(PEt3)2] and
(Et2Sn)9 gave the complex trans-[PtCl (SnEt2Cl)(PEt3)2],
which was also obtained by the routes shown in Scheme
1.
2.2. Starting materials
The metal complexes were prepared by standard
methods: [PtCl2L2], Lꢀ
PPh3; [{Pt(m-Cl)Cl(PBu3)}2]; trans-[PtCl R(PEt3)2],
RꢀMe, Ph [12Á16]; cis-[PtPh2(PEt3)2] [17];
[PtCl2(COD)] [18]; [Pt(C2H4)(PPh3)2] [19]; [Pt(COD)2]
[20]; and [Pt(PEt3)4] [21]. The organotin compounds
/
PEt3, PPr3, PBu3, PEtPh2,
In contrast when a mixture of (Ph2Sn)6, and trans-
[PtCl2(PEt3)2] in toluene was stirred in daylight at room
temperature, the 31P-NMR spectrum showed that no
reaction had taken place even after ca. 3 days. This may
due to the lower tendency of (Ph2Sn)6 compared with
(Me2Sn)6 and (Et2Sn)9 to dissociate to R2Sn moieties.
However, when the mixture was exposed to tungsten
light at ca. 90 8C for ca. 100 h, the 31P-NMR spectrum
revealed the presence of (in addition to a small amount
of the starting platinum complex) three complexes, all
having the trans-configuration. Two of them were
identified as trans-[PtCl (SnPh2Cl)(PEt3)2] (separately
prepared by reaction of [Pt(PEt3)4] with SnPh2Cl2 [25])
and trans-[PtCl (SnPhCl2)(PEt3)2] (Tables 1 and 2), the
latter being formed by reaction of the starting platinum
complex with the decomposition products of (Ph2Sn)6
formed upon prolonged heating (see latter). The third
complex (10%) was identified as trans-[PtPhCl(PEt3)2]
[26].
/
/
were also prepared by standard methods: SnR2Cl2, Rꢀ
Me, Et, Ph [22,23]; (R2Sn)n, RꢀMe, Ph, nꢀ6 and Rꢀ
Et, nꢀ9 [2,24].
/
/
/
/
/
2.3. Reaction procedure
The reactions involved (R2Sn)n,(Rꢀ
/
Me, Ph; nꢀ6 or
/
RꢀEt; nꢀ9) and various platinum complexes. A
/
/
typical procedure was as follows: the compound
(Me2Sn)6 (0.18 g, 1.2 mmol) was suspended in benzene
or toluene (20 cm3) and [PtCl2 L2] (Lꢀ
PEt3, PPr3,
PBu3, PEtPh2, PPh3) (2.1 mmol) was added. The
mixture was stirred at room temperature (r.t.) for 24 h
/
(Lꢀ
PPr3). A yellowÁ
the case of LꢀPPh3 which gave a coloured suspension
/
PEt3, PBu3, PPh3); 12 h (Lꢀ
/
PEtPh2) or 50 h (Lꢀ
/
/orange solution was obtained, except in
Analogous results were obtained from the reactions
/
between cis- or trans-[PtCl2L2], Lꢀ
and (R2Sn)n (Tables 1 and 2). However, neither (R2Sn)6
(RꢀMe, Ph) nor (Et2Sn)9 reacted with the cis-
/PBu3, PPr3, PEtPh2
owing to the insolubility of the starting material cis-
[PtCl2 (PPh3)2]. The clear supernatant liquid was
reduced in volume and used for recording of the 31P-
NMR spectrum. Details of the reactions between
(R2Sn)n and platinum complexes are summarised in
Table 1.
/
[PtCl2(PPh3)2] in toluene or benzene at room tempera-
ture or at higher temperatures, because of the extreme
insolubility of cis-[PtCl2(PPh3)2]. The more soluble
trans-isomer, trans-[PtCl2(PPh3)2], was thus prepared
[27]. The reactions between this complex and (Me2Sn)6
or (Et2Sn)9 were not examined, because, the expected
3. Results and discussion
products trans-[PtCl(SnR2Cl)(PPh3)2] (RꢀMe, Et)
/
were already known, having been prepared by the
oxidative-addition reaction between [Pt(C2H4)(PPh3)2]
3.1. Reactions of (R2Sn)n with platinum(II) complexes
and SnR2Cl2 (RꢀMe, Et), in contrast to that with
/
Reactions of (R2Sn)n, (Rꢀ
/
Me, Ph; nꢀ
/
6 and Rꢀ
/
Et;
SnPh2Cl2, which gave cis-[PtPh(SnPhCl2)(PPh3)2]. The
reaction between trans-[PtCl2(PPh3)2] and (Ph2Sn)6 was
examined since the expected product cis- or trans-
[PtCl(SnPh2Cl)(PPh3)2 had not been previously pre-
pared. When the 31P-NMR spectrum was recorded after
UV irradiation for 1 h of a mixture of trans-
[PtCl2(PPh3)2] and (Ph2Sn)6 in benzene, it revealed the
nꢀ9), in slight excess, with Pt(II) complexes were
/
carried out in benzene or toluene. Chlorinated solvents
react with (R2Sn)n upon exposure to daylight by
insertion of R2Sn into Cꢀ
or Et the mixtures were exposed to daylight at room
temperature whereas for RꢀPh they were exposed to
/
Cl bonds [5,6]. For RꢀMe
/
/

T.A.K. Al-Allaf / Journal of Organometallic Chemistry 654 (2002) 21Á
/28
23
Table 1
Formation of complexes containing R2Sn (RꢀMe, Ph, Et) moieties
Reactants
Reaction conditions
Product
L
Configuration Proportion (%)a
trans-[PtCl2L2]ꢁ(Me2Sn)6
trans-[PtC12L2]ꢁ(Et2Sn)9
trans-[PtCl2L2]ꢁ(Ph2Sn)6
Benzene, daylight, room temperature,24 h
Benzene, daylight, room temperature,50 h
Toluene, tungsten light, 90 8C, 100 h
[PtCl(SnMe2Cl)L2] PEt3
[PtCl(SnEt2Cl)L2] PEt3
trans-
trans-
trans-
trans-
trans-
trans-
trans-
trans-
trans-
94
100
37
[PtCl(SnPh2C1)L2] PEt3
[PtCl(SnPhCl2)L2]
[PtCl(SnMe2C1)L2] PBu3
23
34
cis- or trans-[PtCl2L2]ꢁ(Me2Sn)6 Benzene, daylight, room temperature,24 h
cis- or trans-[PtCl2L2]ꢁ(Et2Sn)9 Benzene, daylight, room temperature,12 h
cis- or trans-[PtCl2L2]ꢁ(Ph2Sn)6 Toluene, tungsten light, 90 8C, 100 h
[PtCl(SnEt2Cl)L2]
[PtCl(SnPh2Cl)L2]
[PtCl(SnPhCl2)L2]
PBu3
PBu3
10
31
31
85
cis-[PtC12L2]ꢁ(Me2Sn)6
cis-[PtC12L2]ꢁ(Me2Sn)6
cis-[PtCl2L2]ꢁ(Et2Sn)9
Benzene, daylight, room temperature,50 h
Toluene, daylight, room temperature,12 h
[PtCl(SnMe2Cl)L2] PPr3
[PtCl(SnMe2Cl)L2] PEtPh2 trans-
PEtPh2 trans-
cis-
61
34
Benzene, daylight, room temperature, 12 h [PtCl(SnEt2Cl)L2]
[PtCl(SnEt2Cl)L2]
29
trans-[PtMe(C1)L2]ꢁ(Et2Sn)9
trans-[PtPh(Cl)L2]ꢁ(Ph2Sn)6
trans-[PtCl2L2]ꢁ(Ph2Sn)6
Benzene, daylight, room temperature,40 h
Toluene, tungsten light, 90 8C, 100 h
Benzene, UV light, reflux, 1 h
[PtMe(SnEt2Cl)L2] PEt3
[PtPh(SnPh2Cl)L2] PEt3
trans-
6.0
15.5
42
trans-
cis-
cis-
[PtPh(SnPhCl2)L2] PPh3
[PtPh(SnPh2Cl)L2]
24.5
4.0
10
cis-[PtPh2L2]ꢁ(Ph2Sn)6
cis- [PtPh2L2]ꢁSnPh4
[Pt2Cl4L2]ꢁ(Me2Sn)6
Toluene, tungsten light, 90 8C, 168 h
Toluene, tungsten light, 90 8C, 168 h
Toluene, daylight, room temperature, 24 h [PtCl(SnMe2Cl)L2] PBu3
[PtCl(SnMeCl2)L2]
[PtPh(SnPh3)L2]
[PtPh(SnPh3)L2]
PEt3
PEt3
trans-
trans-
trans-
trans-
trans-
trans-
trans-
trans-
trans-
cis-
2.5
26
[Pt2Cl4L2]ꢁ(Et2Sn)9
Toluene, daylight, room temperature, 1 h
[PtCl(SnEt2Cl)L2]
[PtCl(SnEtCl2)L2]
[PtCl(SnEtCl2)L2]
[PtCl(SnC13)L2]
[PtPh(Sn2Ph5)L2]
[PtPh(Sn6Ph11)L2]
[PtCl(SiMe3)L2]
PBu3
19
17.5
44
cis-[PtCl2L2]ꢁ(Et2ClSn)2
cis-[PtCl2L2]ꢁSnCl4
[PtL4]ꢁ(Ph2Sn)6
Toluene, sealed tube, 130 8C, 30 h
Toluene, room temperature, soon
Toluene, room temperature, 2 h
PBu3
PBu3
PEt3
10
22
30
35.5
trans-[PtMe(C1)L2]ꢁ(Me2Si)6
Cyclohexane, UV light,13 h
PBu3
trans-
a
Proportions of complexes were inferred directly from the relative peak heights in the 31P{1H}-NMR spectra.
presence of cis-[PtPh(SnPhCl2)(PPh3)2] (42%), cis-
[PtPh(SnPh2Cl)(PPh3)2] (24%), trans-[PtPhCl(PPh3)2]
(24.5%), as well as a small amount of the starting
complex. There was no evidence for the presence of cis-
or trans-[PtCl(SnPh2Cl)(PPh3)2 in the spectrum (see
below for the suggested mechanism).
1) The stannylenes R2Sn generated in aromatic sol-
vents from (R2Sn)n, upon exposure to light, un-
dergo direct insertion into Ptꢀ
/Cl bonds to form
Pt(SnR2Cl) species.
hn
(R2Sn)n 0 nR2Sn
(1)
When trans-[PtMeCl(PEt3)2] was treated with
(Et2Sn)9 with exposure to daylight in benzene at room
temperature for ca. 40 h, the 31P-NMR spectrum
revealed the presence of a complex with d 14.8 ppm
and J(PtP) 2600 Hz, which was judged to be trans-
[PtMe(SnEt2Cl)(PEt3)2]. These parameters are identical
to those for trans-[PtMe(SnMe2Cl)(PEt3)2] prepared by
oxidative-addition of SnMe3Cl to [Pt(PEt3)3], {J(PtP)
2583 Hz} [25]. Similarly trans-[PtPhCl(PEt3)2] when
treated with (Ph2Sn)6 in toluene under tungsten light
irradiation at 90 8C for ca. 100 h, the 31P-NMR
[PtX(Cl)L2]ꢁR2Sn 0 [PtX(SnR2Cl)L2]
(2)
2) The R2Sn moieties generated in solution first
inserted into PtꢀCl bonds to form Pt(SnR2Cl)
/
species followed by generation of R2SnXCl, with
reduction of the platinum(II) complex to [PtL2]. The
latter, which is highly reactive, undergoes oxidative-
addition of R2SnXCl to give [PtX(SnR2Cl)L2] Eq.
(3):
[PtX(Cl)L2]ꢁR2Sn 0 [PtX(SnR2Cl)L2]
0 [PtL2]ꢁR2SnXCl f0ast[PtX(SnR2Cl)L2]
spectrum
revealed
the
presence
of
trans-
(3)
[PtPh(SnPh2Cl)(PEt3)2] (Tables 1 and 2), authentic
samples of which were prepared from SnPh3Cl by the
three methods shown in Scheme 1.
We favour the second mechanism for the reasons
set out below:
3.2. Suggested mechanism for reactions of (R2Sn)n with
platinum(II) complexes
A) When a mixture of trans-[PtCl2(PBu3)2] and
(Et2Sn)9 in toluene was stirred with a five-fold
excess of SnMe2Cl2 at room temperature, the 31P-
NMR spectrum showed the presence of, in addition
to some unreacted platinum starting material, only
We consider two possible mechanisms for the reac-
tions of (R2Sn)n with platinum(II) complexes:

24
T.A.K. Al-Allaf / Journal of Organometallic Chemistry 654 (2002) 21Á28
/
Table 2
31P{1H}-NMR data of complexes obtained from the reaction between platinum(II) complexes and (R2Sn)n , RꢀMe, Ph, nꢀ6; RꢀEt, nꢀ9
Complex
L
d (ppm)
1J(PtP) (Hz)
2J(SnP) (Hz)
2J(PP) (Hz)
119Sn
117Sn
a
f
trans-(PtCl(SnMe2Cl)L2]
PEt3
16.0
16.5
2390
2387
2376
2368
2651
2420
2398
2681
2134
4312
2600
2318
2300
2539
2580
2544
2264
1966
3107
2054
2637
2138
2208
2192
2223
2240
2053
2820
137
g
139
140
133
134
PBu3
PPr3
7.3
6.6
f
137
137
f
PEtPh2
PEt3
PBu3
19.8
16.8
a
g
f
trans-(PtCl(SnEt2Cl)L2]
cis-[PtCl(SnEt2Cl)L2]
127
128
8.3
20.1
123
f
PEtPh2
PEtPh2
127
2076
c
25.7
16.3
1987
e
d
e
12
a
e
e
trans-[PtMe(SnEt2Cl)L2]
trans-[PtCl(SnPh2Cl)L2]
PEt3
PEt3
PBu3
PEt3
PEt3
PEt3
PEt3
14.8
14.6
a
g
150
149
143
144
5.6
7.7
a
g
trans-[PtPh(SnPh2Cl)L2]
a
195
e
186
e
g
trans-[PtPh(SnPh3)L2]
trans-[PtPh(Sn2Ph5)L2]
6.3
9.7
a
g
204
195
a
c
cis-[PtPh(Sn6Ph11)L2]
10.5
5.3
17
d
b,h
c
cis-[PtPh(SnPhCl2)L2]
cis-[PtPh(SnPh2Cl)L2]
trans-[PtCl(SnPhCl2)L2]
trans-[PtCl(SnMeCl2)L2]
PPh3
PPh3
26.1
20.4
d
e
e
e
e
16
15
b,h
c
27.2
23.5
d
a
PEt3
PBu3
PBu3
PBu3
PBu3
PBu3
14.4
5.6
180
180
172
165
234
172
171
165
158
223
a
6.2
6.9
a
trans-[PtCl(SnEtCl2)L2]
a
trans-[PtCl(SnCl3)L2]
trans-[PtCl(SiMe3)L2]
6.0
12.7
a
Data obtained with toluene as solvent and H3PO4 as external reference.
Data obtained by dichloromethane as solvent.
Parameters for P trans- to Sn.
b
c
d
e
f
Parameters for P cis- to Sn.
Signal to noise ratio insufficient for observation of Sn satellites.
Tin satellites for Sn(119) and Sn(117) were not very well resolved.
Closely similar to those reported [25].
g
h
These were already reported and their data are closely similar to those reported [37].
trans-[PtCl(SnMe2Cl)(PBu3)2] and no trans-
[PtCl(SnEt2Cl)(PBu3)2].This is what would be ex-
pected for the mechanism above (Eq. (3)), in which
Et2Sn first inserts into PtꢀCl bonds of [PtCl2
/
(PBu3)2] to form Pt(SnEt2Cl) species and the latter
then generates Et2SnCl2 with the formation of
[Pt(PBu3)2], then since SnMe2Cl2 is more reactive
than SnEt2Cl2, it would selectively add to the Pt(0)
complex to give the observed product (Scheme 2a).
However, in another experiment, when the complex
trans-[PtCl(SnEt2Cl)(PBu3)2], prepared as described
earlier, was treated with an excess of SnMe2Cl2 in
toluene for 4 h the 31P-NMR spectrum of the
solution revealed the presence of only trans-
[PtCl(SnMe2Cl)(PBu3)2]. It is possible that
SnMe2Cl2
added
oxidatively
to
trans-
[PtCl(SnEt2Cl)(PBu3)2] to give a Pt(IV) intermediate
(Scheme 2b) which underwent reductive-elimination
of SnEt2Cl2 to form the Pt(II) complex trans-
[PtCl(SnMe2Cl)(PBu3)2]. Thus, it is also possible
that the reaction between trans-[PtCl2(PBu3)2] and a
Scheme 1. Methods of preparing trans-[PtCl(SnMe2Cl)(PEt3)2].

T.A.K. Al-Allaf / Journal of Organometallic Chemistry 654 (2002) 21Á
/28
25
20.0 ppm, J(PtP) 2672 Hz (CH2Cl2)}, and no
complexes containing PtꢀSn bonds were detected.
/
This showed that the formation of cis-
[PtPh(SnPh2Cl)(PPh3)2] in the reaction involving
(Ph2Sn)6 was not due to the effect of the UV light
on the cis-[PtPh(SnPhCl2)(PPh3)2].
C) i) The reaction of cis-[PtPh2(PEt3)2] and (Ph2Sn)6 in
toluene gave trans-[PtPh(SnPh3)(PEt3)2] and some
SnPh4 was also formed.
ii) The reaction of cis-[PtPh2(PEt3)2] with SnPh4 in
toluene gave trans-[PtPh(SnPh3)(PEt3)2] as shown
by 31P-NMR spectroscopy (Tables 1 and 2). These
experiments provide good evidence that the first
step is the formation of Pt(0) complex which is
followed by oxidative-addition of SnPh4 [produced
by decomposition of (Ph2Sn)6] [3]. To confirm this,
we exposed a stirred suspension of (Ph2Sn)6 in
toluene under nitrogen at 90 8C to tungsten light
for ca. 12 days. The mixture was then allowed to
cool to room temperature and [Pt(C2H4)(PPh3)2]
was added and the toluene evaporated off. The
residue was dissolved in dichloromethane (in which
it is more soluble) and the 31P-NMR spectrum of
the solution revealed the presence of two cis-
complexes as the major products along with a little
of the starting complex. One of these cis-complexes
was judged to be cis-[PtPh(SnPh3)(PPh3)2] [28]
(Table 2) and the other gave parameters of d 27.7
ppm; J(PtP) 2446 Hz (P trans- to Sn) and d 22.1
ppm; J(PtP) 2097 Hz (P trans- to Ph) (the tin
satellites could not be observed, because of the low
signal to noise ratio). These parameters are closely
similar to those for cis-[PtPh(SnPh2OSnPh3)-
(PPh3)2] and cis-[PtPh(SnPh2OH)(PPh3)2] [29]. The
results provide good evidence that (Ph2Sn)6 decom-
poses in solution under the conditions used to give
organotin compounds that can react with Pt(0)
complexes in the usual way. It is noteworthy that
(Ph2Sn)6 does not react with [Pt(C2H4)(PPh3)2]
under normal conditions (vide infra).
Scheme 2. The suggested mechanism for the reaction of stannylenes
R2Sn with [PtCl2L2] complexes.
mixture of (Et2Sn)9 and SnMe2Cl2 did not form
instead
which
[Pt(PBu3)2]
[PtCl(SnEt2Cl)(PBu3)2],
but
gave
reacted
trans-
with
SnMe2Cl2 as in Scheme 2b. This ambiguity was
resolved as described under (B), below.
B) We mentioned above that treatment of trans-
[PtCl2(PPh3)2] with (Ph2Sn)6 gave a mixture of cis-
[PtPh(SnPhCl2)(PPh3)2] and cis-[PtPh(SnPh2Cl)-
(PPh3)2] (Tables 1 and 2) and not the expected
[PtCl(SnPh2Cl)(PPh3)2], which would be produced
by insertion of Ph2Sn into Ptꢀ
likely that decomposition of (Ph2Sn)6 to various
species occurred and that these insert into PtꢀCl
/Cl bonds. It is quite
/
bonds of trans-[PtCl2(PPh3)2] (Eq. (3))to give finally
[Pt(PPh3)2] and SnPh2Cl2 as well as SnPh3Cl, and
both of these tin compounds reacted with the Pt(0)
complex
to
give
a
mixture
of
cis-
[PtPh(SnPhCl2)(PPh3)2] and cis-[PtPh(SnPh2Cl)-
(PPh3)2], respectively. It is possible that insertion
of Ph2Sn moieties into Ptꢀ/Cl bond had initially
occurred to give cis-or trans-[PtCl(SnPh2Cl)-
(PPh3)2] as an intermediate, and that the latter
then reacted with another molecule of SnPh2Cl2 to
D) It should be noted that double insertions of R2Sn
moieties into both Ptꢀ
/
Cl bonds in the reaction
to give
give
the
thermodynamically
stable
cis-
between [PtCl2L2] and (R2Sn)n
[PtPh(SnPhCl2)(PPh3)2] [1].The question then arises
of how the complex cis-[PtPh(SnPh2Cl)(PPh3)2]
could be formed in solution if the reaction involved
insertion of Ph2Sn moieties? One possibility is that
UV irradiation of cis-[PtPh(SnPhCl2)(PPh3)2] in
[Pt(SnR2Cl)2L2] did not occur in any of the
experiments, which provides further support for
the mechanism shown in Scheme 2a.
The reaction of (Me2Si)6 with platinum(II) complexes
was carried out in the hope of obtaining complexes
solution
somehow
formed
cis-[PtPh-
formed by insertion of the Me2Si moiety into Ptꢀ
/
Cl
(SnPh2Cl)(PPh3)2], and so we examined the
behaviour of cis-[PtPh(SnPhCl2)(PPh3)2] (prepared
as described in ref. [28]) when subjected to UV
irradiation in toluene. After 1 h, the 31P-NMR
spectrum of the solution revealed the presence of
trans-[PtPhCl(PPh3)2] {d 24.9 ppm and J(PtP) 3158
Hz (CH2Cl2)} as well as trans-[PtCl2(PPh3)2] {d
bonds. Due to the low reactivity of (Me2Si)6, UV light
was used, and the quartz reaction vessel was irradiated
at a distance of ca. 10 cm with a Hanovia medium
pressure Hg lamp, model UVS. 500. The 31P-NMR
spectrum of a mixture obtained from cis-or trans-[Pt Cl2
L2] (LꢀPBu3 or PEt3) and (Me2Si)6 in 1:1 or 6:1 molar
/

26
T.A.K. Al-Allaf / Journal of Organometallic Chemistry 654 (2002) 21Á28
/
ratio in cyclohexane after 16 h of irradiation revealed
the presence of a complex with the parameters d 14.4
proportions of the other products had increased to 43,
29 and 28, respectively (Scheme 3). The disappearance
of the [{Pt(m-Cl)Et(PBu3)2}2] is probably associated with
the instability arising from the ease of b-elimination
from the ethyl group attached to platinum. In contrast,
the complex [{Pt(m-Cl)Me(PBu3)2}2], is fairly stable in
ppm, J(PtP) 2715 Hz (Lꢀ
J(PtP) 2726.5 Hz (LꢀPEt3) which was identified as
trans-[PtCl(H)L2] [30]. It seems that Me2Si moiety
initially inserts into PtꢀCl bonds of [PtCl2L2] followed
/PBu3) and d 23.3 ppm,
/
/
by generation of SiMe2Cl2 and [PtL2]; the former would
then undergo hydrolysis very readily to give HCl, which
would add to [PtL2]. When a mixture of trans-
[PtMe(Cl)(PBu3)2] and a slight excess of (Me2Si)6 in
cyclohexane was UV irradiated for ca. 13 h, the 31P-
NMR spectrum revealed the presence of three com-
plexes, two of which were identified as trans-
[PtCl2(PBu3)2)] (22%) and trans-[PtCl(H)(PBu3)2]
(20%). The third complex (36%), with parameters d
12.7 ppm and J(PtP) 2820 Hz, was tentatively identified
as trans-[PtCl(SiMe3)(PBu3)2] since its coupling con-
stant is very similar to that for e.g. trans-
solution.
Furthermore,
the
complex
trans-
[PtCl(SnEtCl2)(PBu3)2] (Scheme 3) was also detected
by 31P-NMR spectroscopy when a solution reaction of
cis-[PtCl2(PBu3)2] and (Et2ClSn)2 in toluene was heated
at 130 8C in a sealed tube for 30 h in an attempt to
produce Et2Sn species [4] that might insert into Ptꢀ
/
Cl
bonds to give, e.g. trans-[PtCl(SnEt2Cl)(PBu3)2]. The
31P-NMR spectrum of the mixture revealed the presence
of, in addition to unchanged starting complex, only the
trans-[PtCl(SnEtCl2)(PBu3)2] (44%). The formation of
trans-[PtCl(SnRCl2)(PBu3)2] (RꢀMe, Et) in this reac-
/
tion and the reactions listed in Scheme 3 can be
understood in terms of a redistribution of organotin
compounds in the presence of the extra chlorine in the
bridge complex, to form SnRCl3, with the latter, which
[PtCl(SiPh3)L2],
[PtCl(SiCl3)L2], Lꢀ
trans-[PtCl(SiPh2Me)L2],
trans-
PMe2Ph; for which the values of
/
J(PtP) are 2772, 2842 and 2873 Hz, respectively [31].
This favours the mechanism suggested for the analogous
reactions with (R2Sn)n compounds (Eq. (3) and Scheme
2a).
has
a high reactivity, reacting immediately with
[Pt(PBu3)2] (Eq. (3), Scheme 2a) to give trans-
[PtCl(SnRCl2)(PBu3)2].
It is evident that none of the reactions of (R2Sn)n with
Pt(II) complexes that we examined proceeded via direct
3.3. Reaction of (R2Sn)n with bridged platinum
complexes
insertion of R2Sn moieties into the Ptꢀ
Furthermore we observed no formation of any bridge
complex containing PtꢀSn bonds in the reaction be-
tween [{Pt(m-Cl)Cl(PBu3)}2] and (R2Sn)n. In contrast,
the stable divalent tin compounds R2Sn, RꢀN(SiMe3)2
and CH(SiMe3)2 were found to undergo ready direct
insertion into PtꢀCl bonds [32].
In order to complete the series of the complexes trans-
[PtCl(SnRxCl3ꢂx)(PBu3)2] (Xꢀ2, 3, 0), that with Xꢀ
0, i.e. trans-[PtCl(SnCl3)(PBu3)2] [usually prepared by
insertion of SnCl2 into PtꢀCl bonds] was obtained from
the reaction of cis-[PtCl2(PBu3)2] with SnCl4. When the
/Cl bonds.
/
Reactions of (R2Sn)n with the bridged complex
[{Pt(m-Cl)Cl(PBu3)}2] were examined, these provide
evidence of whether or not insertion of R2Sn moieties
occurs. The reactants and the products (with their
proportions) of these reactions are indicated in Scheme
3.
When the 31P-NMR spectrum of the mixture obtained
from of [{Pt(m-Cl)Cl(PBu3)}2] and (Et2Sn)9 was re-
corded again after 24 h at room temperatures, it showed
that the [{Pt(m-Cl)Et(PBu3)2}2] had disappeared and the
/
/
/
/
/
Scheme 3. The products formed from the reaction of trans-[{Pt(m-Cl)Cl(PBu3)}2] and (R2Sn)n in toluene. For 31P-NMR data of the Ptꢀ
complexes, see Table 2.
/Sn

T.A.K. Al-Allaf / Journal of Organometallic Chemistry 654 (2002) 21Á
/28
27
SnCl4 was added to trans-[PtCl2(PBu3)2] in toluene a
rapid reaction occurred and a white precipitate sepa-
rated. The solid was dissolved in dichloromethane and
the 31P-NMR spectrum recorded to show that two
complexes were present, with d 5.5 ppm; J(PtP) 3657
Hz (78%) and d 10.6 ppm; J(PtP) 3589 Hz (22%),
neither associated with tin satellites. These may be
related to a bridge complex present as both cis-and
trans-isomers, but are not [{Pt(m-Cl)Cl(PBu3)}2] {cis-, d
0.2 ppm; J(PtP) 3702 Hz and trans-, d 2.6 ppm; J(PtP)
3814 Hz (CH2Cl2)} [33]. The yellowish filtrate was
shown by 31P-NMR spectroscopy to contain trans-
[PtCl(SnCl3)(PBu3)2] (Tables 1 and 2) as its parameters
ca. 20 h, the 31P-NMR spectrum revealed the presence
of, in addition to the unchanged [Pt(C2H4)(PPh3)2], a
complex with d 49.9 ppm and J(PtP) 4463 Hz (30%),
which was definitely identified as [Pt(PPh3)3] [36]; no
complexes containing Ptꢀ/Sn bonds were observed.
Similar results were obtained when either THF or
pyridine was used instead of benzene.
When the more reactive complex [Pt(PEt3)4] was used
with (Me2Sn)6 in toluene, an immediate decomposition,
to give a dark brown mixture, occurred, but the 31P-
NMR spectrum showed that no complex containing Ptꢀ
/
Sn bonds was formed. When (Ph2Sn)6 was used instead
of (Me2Sn)6, the 31P-NMR spectrum revealed the
presence of three complexes, the first one (17%) being
the trans-[PtPh2(PEt3)2] [26]. The second (22%) and
third (30%) complexes (Tables 1 and 2) were identified
were identical to those for trans-[PtCl(SnCl3)L2](Lꢀ
/
PEt3 [34] and LꢀPCyc3 [25]). It is relevant to note
/
that Baird [35] reported that trans-[PtH(Cl)(PPh3)2] and
SnCl4 in benzene gave an orange precipitate, which was
identified as [PtCl2(SnCl3)2(PPh3)2], i.e. a Pt(IV) com-
plex. We repeated that reaction in order to examine the
31P-NMR spectrum of the product. When the orange
precipitate was isolated and dissolved in dichloro-
methane, the spectrum revealed the presence of two
complexes with parameters: d 12.9 ppm; J(PtP) 3884 Hz
(63%) and d 16.1 ppm; J(PtP) 3825 Hz (37%). None of
the resonances showed tin satellites, although the signal
to noise ratios were easily adequate for the detection of
such satellites. The parameters could be for cis- and
trans- isomers of a bridged complex, but not cis- and
trans-[{Pt(m-Cl)Cl(PPh3)}2] {cis-, d 3.4 ppm; J(PtP)
4004 Hz and trans-, d 5.2 ppm; J(PtP) 4099 Hz} [34].
We cannot account for Baird’s results [35], and we could
not detect the complex he suggested or, indeed, any
as trans-[PtPh(Sn2Ph5)(PEt3)2]
[PtPh(Sn6Ph11)(PEt3)2], respectively.
[25]
and
cis-
An attempt was made to bring (Ph2Sn)6 into reaction
with the more active platinum(0) complex [Pt(COD)2] in
order to obtain complexes containing Ptꢀ
/
Sn bonds. A
suspension of the reactants was stirred in toluene at
room temperature for ca. 2 h, during which it turned
yellowÁbrown. It was filtered through Celite and the
/
filtrate evaporated to dryness. The residual solid was
redissolved in dichloromethane and PPh3 was added.
The 31P-NMR spectrum showed that no complex
containing Ptꢀ/Sn bonds was present and only small
singlet peaks (not associated with platinum satellites)
were observed.
complex containing Ptꢀ/Sn bonds.
3.4. Reaction of (R2Sn)n with platinum(0) complexes
Acknowledgements
The reactions of (R2Sn)n with platinum(0) complexes
were examined in the hope of obtaining complexes
arising either by ring opening of (R2Sn)n to give bis-
tin chelation to platinum or by insertion of platinum(0)
This work was carried out in the School of Molecular
Sciences at Sussex University, Brighton BN1 9QJ, UK,
in association with Professor C. Eaborn and Dr. A.
Pidcock. The author is very grateful to them for their
kind help and advice during the work.
into Snꢀ
moieties (Rꢀ
can co-ordinate to Cr, W and Fe [8Á
/
R bonds. It was reported that stable R2Sn
alkyl, aryl or halogen; MꢀGe, Sn, Pb)
10] in the presence
/
/
/
of an electron donor solvent (B:), e.g. pyridine or THF
(Equation 4).
References
ð4Þ
[1] T.A.K. Al-Allaf, J. Organomet. Chem. 590 (1999) 25 (and
references therein).
[2] M. Gielen, P.G. Harrison, ‘Organomet. Coord. Chem. Germa-
Thus we carried out many reactions between plati-
num(0) complexes and (R2Sn)n in various solvents. In
the case of [Pt(C2H4)(PPh3)2] and (Me2Sn)6 or (Ph2Sn)6
in benzene, the 31P-NMR spectrum recorded after 3 h at
room temperature revealed the presence only of the
platinum starting material, but when the mixture was
heated at reflux for ca. 10 min or put aside for a further
nium, Tin, Lead’
A
Plenary Lecture, Second International
74.
[3] A.L. Rheingold, Homoatomic Rings, Chains and Macromole-
Conference, 1977 (pub. 1978), pp. 51Á
/
cules of Main Group Elements (Chapter 11), Elsevier, Amster-
dam, 1977, pp. 277Á288.
[4] R. Sommer, B. Schneider, W.P. Neumann, Liebigs Ann. Chem.
/
692 (1966) 12.

28
T.A.K. Al-Allaf / Journal of Organometallic Chemistry 654 (2002) 21Á28
/
[5] U. Schroer, W.P. Neumann, Angew. Chem. Int. Ed. 14 (1975)
240.
[18] J.X. McDermott, J.F. White, G.M. Whitesides, J. Am. Chem.
Soc. 98 (1976) 6521.
[6] W.P. Neumann, A. Schwarz, Angew. Chem. Int. Ed. 14 (1975)
812.
[19] C.D. Cook, G.S. Jouhal, J. Am. Chem. Soc. 90 (1968) 1464.
[20] J.L. Spencer, Inorg. Synth. 19 (1979) 213.
[7] M. Ishikawa, K. Kumada, J. Organomet. Chem. 42 (1972) 325.
[8] T.J. Marks, A.R. Newmann, J. Am. Chem. Soc. 95 (1973) 769.
[9] A.B. Cornwell, P.G. Harrison, J.A. Richards, J. Organomet.
Chem. 76 (1974) C26.
[21] G.W. Parshall, J. Am. Chem. Soc. 96 (1974) 2360.
[22] O.H. Johnson, H.E. Fritz, D.O. Halvorson, R.L. Evans, J. Am.
Chem. Soc. 77 (1955) 5857.
[23] H. Gilman, L.A. Gist, J. Organomet. Chem. 22 (1957) 368.
[24] W.P. Neumann, K. Konig, Liebigs. Ann. Chem. 677 (1964) 1.
[25] T.A.K. Al-Allaf, Asian J. Chem. 11 (1999) 348 (and refs. therein).
[26] F.A. Allen, A. Pidcock, J. Chem. Soc. (A) (1968) 2700.
[27] S.H. Martin, P. Haake, Chem. Commun. (1970) 202.
[28] G. Butler, C. Eaborn, A. Pidcock, J. Organomet. Chem. 181
(1979) 47.
[10] A.B. Cornwell, P.G. Harrison, J. Chem. Soc. Dalton Trans.
(1975) 1486.
[11] (a) V. Christou, B.G. Young, J. Organomet. Chem. 510 (1996)
157;
(b) H. Gilges, U. Schubert, Eur. J. Inorg. Chem. (1998) 897.;
(c) H. Gilges, G. Kickelbick, U. Schubert, J. Organomet. Chem.
548 (1997) 57;
[29] G. Butler, D. Phil. Thesis, Sussex University, UK, 1978.
[30] G. Socrates, J. Inorg. Nucl. Chem. 31 (1969) 1667.
[31] B.T. Heaton, A. Pidcock, J. Organomet. Chem. 14 (1968) 235.
[32] (a) M.F. Lappert, R.S. Rowe, Coord. Chem. Rev. 100 (1990) 267;
(b) T.A.K. Al-Allaf, J. Chem. Res., in press.
(d) Y. Tsuji, Y. Obora, J. Organomet. Chem. 611 (2000) 343;
(e) A.J. Canty, H. Jin, B.W. Skelton, A.H. White, Aust. J. Chem.
52 (1999) 417;
(f) L. Abdol Latif, C. Eaborn, A. Pidcock, N.S. Weng, J.
Organomet. Chem. 474 (1994) 417.
[33] K.J. Odell, D. Phil. Thesis, Sussex University, UK, 1976.
[34] P.S. Pregosin, S.N. Sze, Helv. Chem. Acta 61 (1978) 1848.
[35] M. Baird, J. Inorg. Nucl. Chem. 29 (1967) 367.
[36] C.A. Tolman, W.C. Seidel, D.H. Gerlach, J. Am. Chem. Soc. 94
(1972) 2669.
[12] M.F. Lappert, P.P. Power, Adv. Chem. Ser. Am. Chem. Soc.
Washington (1976) 70.
[13] A.C. Simithies, M. Rycheck, M. Orchin, J. Organomet. Chem. 12
(1968) 199.
[14] J. Chatt, G.A. Rowe, Nature 191 (1961) 1191.
[15] K.A. Jensen, Z. Anorg. U. Allgen. Chem. 299 (1936) 225.
[16] L. Malatesta, C. Cariello, J. Chem. Soc. (1958) 2323.
[17] J. Chatt, B.L. Shaw, J. Chem. Soc. (1959) 4020.
[37] (a) G. Butler, C. Eaborn, A. Pidcock, J. Organomet. Chem. 181
(1979) 47;
(b) C. Eaborn, A. Pidcock, B.R. Steele, J. Chem. Soc. Dalton
(1976) 767.