Novel reactivity aspects of cis-bis(1-alkenyl)platinum(II) compounds of the type Pt(CH2(CH2)nCHCH2) 2L2 (where L2 = dppp, dppe, dppm and n = 1, 2)

Article abstract of DOI:10.1016/j.ica.2010.06.026

We describe the synthesis, structure and reactivity of novel bis(1-alkenyl)platinum(II) complexes, Pt[CH₂(CH₂) _nCHCH₂]₂L₂ (where L₂ = dppp, dppe, dppm and n = 1, 2). The stability of the title complexes with the different ligands is discussed. The steric, chelating and electronic properties of the ligands have a significant impact on the structure as well as on the reactivity of the complexes. Novel reactions with elemental sulfur and carbon dioxide are described and discussed.

Full text of DOI:10.1016/j.ica.2010.06.026

Inorganica Chimica Acta 363 (2010) 3345–3350
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Novel reactivity aspects of cis-bis(1-alkenyl)platinum(II) compounds of the
type Pt(CH2(CH2)nCH@CH2)2L2 (where L2 = dppp, dppe, dppm and n = 1, 2)
*
Akella Sivaramakrishna , John R. Moss, Hong Su
Department of Chemistry, University of Cape Town, Rondebosch 7701, Cape Town, South Africa
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 1 June 2010
Received in revised form 10 June 2010
Accepted 11 June 2010
Available online 10 August 2010
We describe the synthesis, structure and reactivity of novel bis(1-alkenyl)platinum(II) complexes,
Pt[CH2(CH2)nCH@CH2]2L2 (where L2 = dppp, dppe, dppm and n = 1, 2). The stability of the title complexes
with the different ligands is discussed. The steric, chelating and electronic properties of the ligands have a
significant impact on the structure as well as on the reactivity of the complexes. Novel reactions with ele-
mental sulfur and carbon dioxide are described and discussed.
Ó 2010 Elsevier B.V. All rights reserved.
Keywords:
Platinum–alkenyls
Synthesis
Stability
Structure
Reactivity
Structural characterization
1. Introduction
2. Results and discussion
Metal–alkenyls are an interesting class of compound in organo-
metallic chemistry, which have been shown to be key intermedi-
ates in many catalytic reactions and are also useful precursors
with many applications [1]. Recently we have shown that these
compounds can undergo ring-closing metathesis reactions (RCM)
in the presence of Grubbs’ catalysts to produce novel medium to
large metallacycloalkanes in high yields [2]. Interestingly, the
bis(1-alkenyl)platinum(II) complexes have been shown to undergo
selective and quantitative isomerization to their (2-alkenyl)plati-
All the metal–alkenyl complexes (2–9) were prepared either
from [COD]PtCl2 or their corresponding haloplatinum(II) precur-
sors (1a–d) using the well known Grignard route as shown in
Scheme 1 [2–4]. It was found that the former route was much
superior to the later one. All the products were characterized by
analytical and spectroscopic techniques. The structures of 1b and
9 in the solid state were determined by the single crystal X-ray
analysis (Figs. 1 and 2).
The stability of metal–alkenyls strongly depends on various fac-
tors such as the nature of donor ligand, solvent, light and temper-
ature. The stability of the complexes with donor atoms increases
along the series: diphosphine >> tertiary phosphine > COD > 1,10-
phenanthroline > CO. The chelating diphosphines (e.g., dppe, dppp,
dppm) imparts an outstanding stability to the metal carbon bonds
relative to the other ligands. The monophosphine complexes are
relatively stable compared to the corresponding complexes with
N donor ligands such as 1,10-phenanthroline and bipyridyl, which
are very sensitive to the halogenated solvents, light and heat. Ther-
molysis of these bis(1-alkenyl)platinum(II) compounds produce
different organic products, depending on the experimental condi-
tions [3,5]. It is interesting to note that the length of 1-alkenyl
chains did not appear to be a significant factor in the stability of
the bis(1-alkenyl)metal complexes.
num(II) analogs [3]. The formation of stable metal–g
3–allyl com-
plexes from the reactive metal–alkenyl complexes have been also
reported [4]. We have previously reported various other reactions
such as oxidative addition, insertion of carbon monoxide, trans-
metalation and thermal decomposition studies of some selected
bis(1-alkenyl)platinum(II) complexes [5]. It has also been shown
that these title compounds are useful precursors in making hetero-
bimetallic mixed metal carbonyl clusters of the type PtRu2 and
Pt2Ru [6]. The present article describes in detail the synthesis,
structure and novel reactivity of the title compounds. The factors
that influence the reactivity, as well as structural features are also
discussed.
The reactivity of metal–alkenyls with terminal pendant
alkene groups is significantly different from their analogous
metallacycloalkanes and metal–alkyl compounds. Thermal
* Corresponding author. Fax: +27 21 689 7499.
E-mail address: asrkrishna@rediffmail.com (A. Sivaramakrishna).
0020-1693/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2010.06.026

3346
A. Sivaramakrishna et al. / Inorganica Chimica Acta 363 (2010) 3345–3350
Cl
Pt
Cl
i) 2 moles of
BrMgCH2(CH2)nCH=CH2
[n = 1, 2]
+
L2, CH2Cl2
ii) L ,
Et2O
2
L
Cl
CH2(CH2)nCH=CH2
CH2(CH2)nCH=CH2
L
L
Pt
Pt
2 moles of
BrMgCH2(CH2)nCH=CH2
Cl
L
[n = 1, 2]
in Et2O
2, L = PPh3; n = 1
3. L = PPh3; n = 2
1a, L = PPh3;
1b, L2 = dppp;
1c, L2 = dppe;
1d, L2 = dppm;
4. L2 = Ph2P(CH2)3PPh2 (dppp); n = 1
5. L2 = Ph2P(CH2)3PPh2 (dppp); n = 2
6. L2 = Ph2P(CH2)2PPh2 (dppe); n = 1
7. L2 = Ph2P(CH2)2PPh2 (dppe); n = 2
8. L2 = Ph2P(CH2)PPh2 (dppm); n = 1
9. L2 = Ph2P(CH2)PPh2 (dppm); n = 2
Scheme 1.
Fig. 1. Molecular structure of 1b (ORTEP diagram), showing atom-numbering
scheme. One benzene solvent molecule is omitted. Ellipsoids are drawn at 30%
probability level. Selected bond lengths (Å) and selected bond angles (°): Pt(1)–P(1)
2.247(3); Pt(1)–P(2) 2.241(2); Pt(1)–Cl(1) 2.3927(18); Pt(1)–Cl(2) 2.4207(17); P(2)–
Pt(1)–P(1) 94.23(9); P(1)–Pt(1)–Cl(l) 89.87(8); Cl(1)–Pt(1)–Cl(2) 86.87(7).
Fig. 2. Molecular structure of
9 (ORTEP diagram), showing atom-numbering
scheme. Ellipsoids are drawn at 30% probability level. Selected bond lengths (Å)
and selected bond angles (°): Pt(1)–P(1) 2.3025(7); Pt(1)–P(2) 2.3025(7); Pt(1)–C(1)
2.100(3); Pt(1)–C(6) 2.100(3); C(4)@C(5) 1.315(5); C(9)@C(10) 1.377(5); P(2)–
Pt(1)–P(1) 73.45(4); C(1)–Pt(1)–C(6) 85.27(17); P(1)–Pt(1)–C(l) 100.66(9).
decomposition of bis(1-alkenyl)platinum(II) complexes has been
reported leading to the formation of interesting organic product
distribution through b-hydrogen elimination and/or reductive
elimination under different experimental conditions [5–7].
of alkenyl chains as well as the nature of ligand, L2. When the
ligand is dppm, the complex cis-[Pt(1-pentenyl)2(dppm)] (9)
showed the formation of a mixture of unidentified products includ-
ing the expected cis-[Pt(2-pentenyl)2(dppm)]. This could be due to
the strain in the four-membered platinacycle with the chelating
dppm ligand and thus forming dimeric platinum–alkenyls with
bridging dppm. The new 2-alkenyl complexes were fully character-
ized by analytical and spectroscopic methods. Interestingly, 31P
NMR spectra of these complexes indicated the broad signals in
the range of d 46.3–46.8, which suggest a mixture of different
isomers (E/E, E/Z, and Z/Z) similar to the formation of 10 [3]. The
single crystal X-ray analysis confirmed that 11 is a 2-alkenyl
compound and therefore that isomerization has occurred (Fig. 3).
It shows that the two alkenyl chains are different where the alkene
H atoms are cis to each other in one chain, whereas the other
shows trans-positioned H atoms within the same molecule. Bond
lengths and angles of 11 are consistent with compound 10 [3].
2.1. Isomerization of bis(1-alkenyl)platinum(II) complexes to bis(2-
alkenyl)platinum(II)
Recently, we have shown that heating the 1-alkenyl complexes
cis-[Pt(1-alkenyl)2(dppp)] (5) [alkenyl = 1-pentenyl and 1-octenyl]
to 100 °C gave a quantitative isomerization to the corresponding 2-
alkenyl complexes cis-[Pt(2-alkenyl)2(dppp)] (10) (Eq. (1)). Similar
to the isomerization reactions with dppp complexes [3], dppe com-
plexes (7) have undergone the quantitative isomerization reaction
to give 11 under the similar experimental conditions. And it has
been found that this isomerization is strongly dependent on the
concentration of the bis(1-alkenyl) complex in solution, the length

A. Sivaramakrishna et al. / Inorganica Chimica Acta 363 (2010) 3345–3350
3347
Fig. 3. Molecular structure of 11 (ORTEP diagram), showing atom-numbering
scheme. Ellipsoids are drawn at 30% probability level. Selected bond lengths (Å) and
selected bond angles (°): Pt(1)–P(1) 2.2667(18); Pt(1)–P(2) 2.2866(18); Pt(1)–C(1)
2.134(8); Pt(1)–C(6) 2.085(8); C(3)@C(4) 1.318(9); C(8)@C(9) 1.267(9); P(2)–Pt(1)–
P(1) 84.40(6); C(1)–Pt(1)–C(6) 83.4(4); P(1)–Pt(1)–C(l) 93.0(3).
H
H
H
H
Benzene or Toluene
100oC
H
H
L2Pt
L2Pt
+
L2Pt
H
Fig. 4. Molecular structure of 12 (ORTEP diagram), showing atom-numbering
scheme. Ellipsoids are drawn at 25% probability level. Selected bond lengths (Å) and
selected bond angles (°): Pt(1)–P(1) 2.269(3); Pt(1)–P(2) 2.269(2); Pt(1)–S(1)
2.358(2); Pt(1)–S(4) 2.357(3); P(2)–Pt(1)–P(1) 91.00(9); P(1)–Pt(1)–S(l) 88.61(9);
S(1)–Pt(1)–S(4) 93.11(9).
H
5, L2 = dppp;
7, L2 = dppe
H
H
+
L2Pt
polar solvents [9]. The organic products were found to be
1-alkenes, 2-alkenes, dienes and traces of unidentified species from
the reaction mixtures. The single crystal X-ray analysis confirmed
the formation of platinacyclotetrasulfide, PtS4(dppp) (12) as shown
in Fig. 4.
H
H
10, L2 = dppp;
11, L2 = dppe
ð1Þ
S
L
L
L
S
S
THF, RT
S8
Pt
+ other products
Pt
Similar to thermolysis in solution, the UV-irradiation studies of
bis(1-pentenyl)platinum(II) complexes clearly revealed the forma-
tion of bis(2-pentenyl)platinum(II)(L2) analogs (10, L2 = dppp and
11, L2 = dppe) as major products through an irreversible isomeriza-
tion. Thermolysis of these isomerization products in the solid state
at 175 °C yielded some unexpected organic products including 2-
pentene and 2,4-pentadiene as well as some other products in the
GC, which were not observed with the precursor compounds.
L
S
12
5, L2 = dppp
ð2Þ
2.3. Reaction with CO2
2.2. Reaction with elemental sulfur
Attempts were made to study the insertion reactions with CO2
using various platinum–alkenyl complexes containing different li-
gands such as PPh3, dppe and dppp, but all these reactions were
found to be very slow at room temperature. However, the CO2 in-
serted products were difficult to isolate as these compounds were
found to be very sensitive to the experimental conditions.
In the presence of CO2 and moisture, the formation of the corre-
sponding known platinum carbonate complexes (13) [10] in good
yields was evident during the reaction with 3 (Eq. (3)). This could
be due to the cleavage of platinum–carbon bonds by the in situ
formed weak carbonic acid from CO2–H2O mixture. The organic
products were identified as 1-alkenes (70%), 2-alkenes (12%), the
corresponding dienes (2%) and the products with high retention
time (16%). The single crystal X-ray analysis indicated the forma-
Platinum containing sulfur compounds are known in the litera-
ture [8]. Most of the compounds were either ionic or polysulfide
compounds. The reaction of elemental sulfur with the title com-
pounds was aimed at the insertion of sulfur into the metal–carbon
bonds. However, the reaction gave the platinacyclosulfides as a
mixture of products with platinacyclopentasulfide being the major
product (Eq. (2)). 31P NMR of the reaction mixture clearly showed
the formation of very close singlets for the different platinacycles
with different ring sizes, which show similar JPt–P values. Mass
spectral data of the crude reaction mixture clearly indicated the
presence of mass fragments with different platinacyclosulfides
i.e. L2PtS6, L2PtS5, L2PtS4, L2PtS3 and L2PtS2 (where L2 = dppp). It is
also well known that the elemental sulfur, S8 exists as S4 or S5 in

3348
A. Sivaramakrishna et al. / Inorganica Chimica Acta 363 (2010) 3345–3350
tion of 13 and the bond lengths and bond angles are similar to the
literature reports for this compound [10].
L
L
L
L
O
O
CO2
H2O
Pt
Pt
O
+
3, L =PPh3
13
+
+ Other products
Reaction with CO2
ð3Þ
2.4. Discussion on the crystallographic data of compounds 1b, 9, 11,
12 and 13
Intensity data for the single crystals of compounds 1b (CCDC
number 674790), 9 (CCDC number 674788), 11 (CCDC number
674787), 12 (CCDC number 674789) and 13 (CCDC number
674786) were collected at 113 K on a Nonius Kappa CCD diffrac-
tometer using graphite-monochromated Mo K
a
radiation
(k = 0.71073 Å). The crystallographic data of these compounds are
summarized in Table 1.
Fig. 5. Molecular structure of 13 (ORTEP diagram), showing atom-numbering
scheme. Ellipsoids are drawn at 25% probability level. Selected bond lengths (Å) and
selected bond angles (°): Pt(1)–P(1) 2.2297(18); Pt(1)–P(2) 2.2524(18); Pt(1)–O(1)
2.042(4); Pt(1)–O(2) 2.063(5); P(2)–Pt(1)–P(1) 99.66(7); P(1)–Pt(1)–O(l) 98.78(14);
O(1)–Pt(1)–O(4) 65.28(19).
The bond lengths and bond angles of the solvated crystal struc-
ture of 1b were almost identical with the reported structure [12].
The Pt–P and Pt–C bond lengths in 9 and 11 were found in the
range of 2.3025(7)–2.2667(18) and 2.085(8)–2.134(8) respectively
(Figs. 2 and 3). But the Pt–P bond lengths of 1b, 12 and 13 were
found to be in the range of 2.247(3)–2.297(18) (Figs. 1, 4 and 5),
which are slightly shorter than the bond lengths of 9 and 10. An
analog to the crystal structure of 12 was reported using dppe li-
gand [13] and it is found that some of the bond lengths and bond
angles of these complexes were slightly different to each other.
This can be explained by the influence of electronegative atoms at-
tached to the metal. The C@C bond lengths in 9 and 11 showed
1.315(5), 1377(5) and 1.267(9), 1.318(9) respectively. In 13, the
bond length in C@O was 1.208(8), which is significantly shorter
that the other C–O bond lengths [1.323(9) and 1.369(9)].
Table 1
X-ray data and refinement parameters for compounds 1b, 9, 11, 12 and 13.
Compound
1b
9
11
12
13
Structure formula
Formula weight
C
27H26Cl2P2Ptꢀ0.5C6H6
C35H40P2Pt
717.70
C36H42P2Pt
731.73
C27H26P2PtS4ꢀ2CHCl3
974.48
C36H30O3P2PtꢀC2H2Cl2
864.57
717.46
Data collection temperature (K)
Crystal system, space group
a (Å)
b (Å)
c (Å)
173(2)
133(2)
113(2)
133(2)
113(2)
triclinic, P1
ꢀ
monoclinic, P21/n
11.7212(2)
15.0029(5)
16.1048(6)
90
98.541(2)
90
2800.7(2)
4
monoclinic, C2/c
17.3672(2)
8.2433(1)
22.4767(3)
90
105.326(1)
90
3103.40(7)
4
monoclinic, P21/c
12.2411(2)
14.6320(2)
17.9071(3)
90
95.694(1)
90
3191.55(9)
4
monoclinic, P21/c
12.9880(4)
14.0947(5)
19.7921(6)
90
98.558(1)
90
3582.8(2)
4
10.5215(2)
12.1655(3)
15.2639(4)
85.629(1)
71.541(1)
70.453(1)
1745.48(7)
2
a
(°)
b (°)
c
(°)
V (Å3)
Z
Dcalc, calculated density (g cmꢁ3
)
)
1.702
5.333
1404
1.536
4.646
1432
1.523
4.519
1464
1.807
4.708
1904
1.645
4.300
852
Absorption coefficient
F(0 0 0)
l
(mmꢁ1
Crystal size (mm)
h Range for data collection
Limiting indices
0.06 ꢂ 0.08 ꢂ 0.14
4.03–26.02
ꢁ14, 12; 18; 19
48 280/5483
317/0
0.02 ꢂ 0.03 ꢂ 0.06
3.45–25.34
20; 9; 27
41 691/2829
174/0
0.07 ꢂ 0.09 ꢂ 0.12
3.39–25.67
14; 17; 21
82 791/6031
325/4
0.02 ꢂ 0.03 ꢂ 0.05
2.89–25.07
15; 16; 23
40 532/6320
352/0
0.07 ꢂ 0.08 ꢂ 0.11
3.13–25.66
12; 14; 18
32 837/6543
402/0
Reflections collected /unique
No. of parameters/restraints
Extinction coefficient
0.0004(3)
1.052
0.0003(5)
1.079
0.0005(2)
1.037
0.0002(1)
1.026
0.0026(5)
1.028
Goodness-of-fit (GOF) on F2
Final R indices [I > 2
r
(I)]
R1 = 0.0512
wR2 = 0.1292
R1 = 0.0821
wR2 = 0.1475
2.943/ꢁ1.448
R1 = 0.0207
wR2 = 0.0409
R1 = 0.0207
wR2 = 0.0424
2.107/ꢁ0.661
R1 = 0.0426
wR2 = 0.1090
R1 = 0.0602
wR2 = 0.1199
1.979/ꢁ1.453
R1 = 0.0580
wR2 = 0.1252
R1 = 0.0959
wR2 = 0.1408
1.957/ꢁ1.617
R1 = 0.0463
wR2 = 0.0983
R1 = 0.0752
wR2 = 0.1089
1.939/ꢁ1.883
R indices (all data)
Largest difference peak and hole (e Åꢁ3
)

A. Sivaramakrishna et al. / Inorganica Chimica Acta 363 (2010) 3345–3350
3349
The P–Pt–P bond angles of compounds 9 [73.45(4)] and 11
3.2.2. cis-[Pt(1-butenyl)2(dppe)] (6)
[84.40(6)] were found to be shorter than the other compounds,
1b [94.23(9)], 12 [91.00(9)] and 13 [99.66(7)]. In 10, the olefinic
protons were found to be cis to each other in one chain and trans
to each other in another chain.
In conclusion, a variety of bis(alkenyl)platinum(II) complexes
with different donor ligands have been made and it is found that
the stability of these complexes depends on the nature of ligand.
The novel reactivity aspects of these complexes reveal that they
are promising precursors in many interesting reactions.
A similar procedure was followed as described above using
Pt(COD)Cl2 (356 mg, 0.951 mmol) in diethyl ether (20 mL), 1-bute-
nyl Grignard reagent (3.4 mL of 0.85 M, 2.853 mmol) and dppe
(379 mg, 0.951 mmol). Yield: 95%. m.p. 143–145 °C, Anal. Calc.
for C36H42P2Pt: C, 59.09; H, 5.79. Found: C, 58.82; H, 5.74%. 1H
NMR: d 7.36–7.91 (m, 20H, Ph), 5.55–5.71 (m, 2H, @CH), 4.69–
4.80 (m, 4H, @CH2), 1.99–2.17 (m, 4H, P–CH2), 1.25–1.85 (m,
12H, CH2); 31P NMR: d 45.9 (s) (JPt–P = 1641 Hz).
3.2.3. cis-[Pt(1-butenyl)2(dppm)] (8)
A similar procedure was followed as described above using
Pt(COD)Cl2 (386 mg, 1.031 mmol) in diethyl ether (20 mL), 1-bute-
nyl Grignard reagent (3.65 mL of 0.85 M, 3.093 mmol) and dppm
(396 mg, 1.031 mmol). The yield of the white crystalline solid
was 92%, m.p. 154–56 °C (dec), Anal. Calc. for C33H36P2Pt: C,
57.47; H, 5.26. Found: C, 57.64; H, 5.28%. 1H NMR: d 7.26–7.96
(m, 20H, Ph), 5.60–5.76 (m, 2H, @CH), 4.71–4.82 (m, 4H, @CH2),
4.12–4.29 (m, 2H, P–CH2), 1.52–2.07 (m, 8H, CH2); 31P NMR: d
ꢁ32.8 (s) (1296 Hz).
3. Experimental
3.1. General
All manipulations were carried out under a nitrogen atmo-
sphere unless otherwise stated. The solvents were commercially
available and distilled from dark purple solutions of sodium/ben-
zophenone ketyl. 1H and 31P NMR spectra were recorded on a Bru-
ker DMX-400 spectrometer and all 1H chemical shifts are reported
relative to the residual proton resonance in the deuterated solvents
(all at 298 K, C6D6). Microanalyses were conducted with a Thermo
Flash 1112 Series CHNS–O Analyzer instrument. GC analyses were
carried out using a Varian 3900 gas chromatograph equipped with
3.2.4. cis-[Pt(1-pentenyl)2(dppm)] (9)
Compound 9 was prepared in the same fashion as compound 4
utilizing Pt(COD)Cl2 (426 mg, 1.138 mmol) in diethyl ether
(20 mL), 1-pentenyl Grignard reagent (2.75 mL of 1.25 M,
3.414 mmol) and dppm (434 mg, 1.138 mmol). The yield was 94%
of the white crystalline solid, m.p. 118–120 °C (dec), Anal. Calc.
for C35H41P2Pt: C, 58.57; H, 5.62. Found: C, 58.82; H, 5.72%. 1H
NMR: d 7.29–7.90 (m, 20H, Ph), 5.62–5.78 (m, 2H, @CH), 4.73–
4.85 (m, 4H, @CH2), 4.07–4.25 (m, 2H, P–CH2), 1.52–2.07 (m,
12H, CH2); 31P NMR: d ꢁ32.9 (s) (1296 Hz).
an FID and a 30 m ꢂ 0.32 mm CP-Wax 52 CB column (0.25
lm film
thickness). The carrier gas was helium at 5.0 psi. The oven was pro-
grammed to hold at 32 °C for 4 min and then to ramp to 200 °C at
10 °/min and hold 5 min. GC–MS analyses for peak identification
were performed using an Agilent 5973 gas chromatograph
equipped with MSD and
a
60 m ꢂ 0.25 mm Rtx-1 column
(0.5 m film thickness). The carrier gas was helium at 0.9 ml/
l
3.2.5. cis-[Pt(2-pentenyl)2(dppe)] (11)
min. The oven was programmed to hold at 50 °C for 2 min and then
ramp to 250 °C at 10 °/min and hold 8 min. Pt(COD)Cl2 [11], L2PtCl2
[14] (L = PPh3 and L2 = dppp, dppe and dppm) (1a–d), 1-alkenyl
Grignard reagents (BrMgCH2(CH2)nCH@CH2; n = 1, 2) were pre-
pared according to literature procedures [15]. The compounds
cis-[Pt(1-butenyl)2(PPh3)2] (2) [2c], cis-[Pt(1-pentenyl)2(PPh3)2]
(3) [2c], cis-[Pt(1-pentenyl)2(L2)] {5, L2 = dppp [2a,2b]; 7, L2 = dppe
[5]}, cis-[Pt(2-pentenyl)2(dppp)] (10) [3] and cis-(carbonato-
A Schlenk flask was charged with 154 mg (0.211 mmol) of 7 in
10 mL of toluene and the mixture was heated at 110 °C for 125 h
under reduced pressure. The reaction was monitored by 1H NMR.
All the volatiles were removed from the pale yellow brown reac-
tion mixture. The product was recrystallized from a CH2Cl2/hexane
mixture (3:5 mL) at ꢁ10 °C for 48 h. to give pure 11 as crystalline
colorless solid. Yield: 128 mg (83%). m.p. 153–155 °C, Anal. Calc.
for C36H42P2Pt: C, 59.09; H, 5.79. Found: C, 59.32; H, 5.84%. 1H
NMR: d 6.76–7.74 (m, 20H, Ph), 5.21–5.58 (m, 4H, @CH), 1.83–
2.03 (m, 4H, P–CH2), 0.68–1.77 (m, 14H, CH2 and CH3); 31P NMR:
d 46.3–46.8 (m) (JPt–P = 1642 Hz).
j
2O,O0)bis(triphenylphosphine-
pared as mentioned earlier.
jP)platinum(II) (13) were pre-
3.2. Synthesis of compounds 4, 6, 8, 9, 11–13
3.2.6. Platinacyclotetrasulfide (12)
3.2.1. cis-[Pt(1-butenyl)2(dppp)] (4)
A solution of cis-[Pt(1-pentenyl)2(dppp)] (245 mg, 0.328 mmol)
and elemental sulfur (168 mg, 0.654 mmol) in THF (10 mL) was
stirred at room temperature for 3 days. The solvent was removed
in vacuo, and the product was isolated from a preparative TLC plate
using CH2Cl2 as an eluent and recrystallized from n-hexane/CH2Cl2
(5:1) at T = ꢁ30 °C. The pure yellow brown crystalline solid was
isolated as major product and dried under vacuo for 3 h. Yield:
176 mg (72%). m.p. 174–176 °C (dec), Anal. Calc. for C27H26P2S4Pt:
C, 44.07; H, 3.56. Found: C, 44.16; H, 3.62%. 1H NMR: d 7.31–7.86
(m, 20H, Ph), 1.92–2.77 (m, 6H, P–CH2); 31P NMR: d ꢁ5.4 (s)
(2706 Hz).
In a Schlenk flask, Pt(COD)Cl2 (316 mg, 0.818 mmol) in diethyl
ether (20 mL) was cooled to T = ꢁ78 °C and 1-butenyl Grignard re-
agent (2.9 mL of 0.85 M, 2.454 mmol) was added. The solution was
brought to ca. 0 °C and then stirred until the solution became clear.
To this, dppp (337 mg, 0.818 mmol) was added and the reaction
mixture stirred for 36 h until a clear solution is formed. The excess
Grignard reagent was removed by hydrolyzing the reaction mix-
ture with 5 ml of saturated aqueous NH4Cl at ꢁ78 °C. The aqueous
layer was washed with 3 ꢂ 5 ml of dichloromethane before the or-
ganic layer was separated. All the volatiles in the flask were re-
moved under reduced pressure and the residue obtained was
recrystallized from a CH2Cl2/hexane mixture (1:2) at ꢁ10 °C for
48 h. The colorless crystalline solid was separated by decanting
the mother liquor and dried under vacuum. For 4; m.p. 132–
134 °C; yield 97%, Anal. Calc. for C35H40P2Pt: C, 58.57; H, 5.62.
Found: C, 58.66; H, 5.72%. 1H NMR d 7.26–7.76 (m, 20H, Ph);
5.42–5.63 (m, 2H, @2CH); 4.40–4.53 (m, 4H, @CH2); 2.41–2.59
(m, 6H, P–CH2); 0.62–1.93 (m, 8H, –CH2); 31P{1H} NMR: 3.44 (s)
(JPt–P = 1623 Hz).
3.2.7. General procedure for UV-irradiation studies
UV-irradiations were carried out with an Englehard Hanovia
Lamp (125 W) at a distance of 16 cm from the reaction tube under
the constant water circulation. The John–Young NMR tubes con-
taining sample solutions of 10 (102 mg, 0.136 mmol) and 11
(96 mg, 0.131 mmol) in toluene-d8 were irradiated for 8 h. These
reactions were monitored by 1H and 31P NMR until the signals
for the starting materials (i.e. 1-alkene protons) disappeared.

3350
A. Sivaramakrishna et al. / Inorganica Chimica Acta 363 (2010) 3345–3350
Chem. Soc. 124 (2002) 10456;
3.2.8. General procedure for CO2 insertion reactions
(d) S.M.A. Shibli, M. Noel, J. Power Sources 45 (1993) 139;
(e) C. Dossi, R. Psaro, A. Bartsch, A. Fusi, L. Sordelli, R. Ugo, M. Bellatreccia, R.
Zanoni, G. Vlaic, J. Catal. 145 (1994) 377;
(f) D.C. Bradley, Polyhedron 13 (1994) 1111;
(g) R.J. Puddephatt, Polyhedron 13 (1994) 1233.
Compound 3 (196 mg, 0.228 mmol) was dissolved in a wet tol-
uene solution (20 mL). After bubbling CO2 through the contents of
the flask for 5–6 min, the solution was stirred at 50 °C under ambi-
ent pressure of carbon monoxide (balloon). After 72 h, the solvent
was removed under the reduced pressure and washed with 10 mL
of Et2O. The obtained residue was filtered and recrystallized from a
CH2Cl2/hexane mixture (2:1 v/v) to give compound 13. Yield 71%
(126 mg). The spectroscopic and analytical characterization data
were found to be similar to the earlier reports [10].
[2] (a) A. Sivaramakrishna, H. Su, J.R. Moss, Angew. Chem., Int. Ed. Eng. 46 (2007)
3541;
(b) A. Sivaramakrishna, H. Su, J.R. Moss, Dalton Trans. (2008) 2228;
(c) K. Dralle, N.L. Jaffa, T. le Roex, J.R. Moss, S. Travis, N.D. Watermeyer, A.
Sivaramakrishna, Chem. Commun. (2005) 3865;
(d) T. Mahamo, F. Zheng, A. Sivaramakrishna, G.S. Smith, J.R. Moss, J.
Organomet. Chem. 693 (2008) 103;
(e) A. Sivaramakrishna, B.C.E. Makhubela, G.S. Smith, J.R. Moss, J. Organomet.
Chem. 695 (2010) 1627.
4. Supplementary material
[3] A. Sivaramakrishna, H. Su, J.R. Moss, Organometallics 26 (2007) 5786.
[4] A. Sivaramakrishna, E. Hager, F. Zheng, H. Su, G.S. Smith, J.R. Moss, J.
Organomet. Chem. 692 (2007) 5125.
[5] A. Sivaramakrishna, B.C.E. Makhubela, F. Zheng, H. Su, G.S. Smith, J.R. Moss,
Polyhedron 27 (2008) 44.
[6] A. Sivaramakrishna, H. Su, J.R. Moss, unpublished results.
[7] F. Zheng, A. Sivaramakrishna, J.R. Moss, Inorg. Chim. Acta 361 (2008) 2871.
[8] (a) K.-W. Kim, M.G. Kanatzidis, Inorg. Chem. 32 (1993) 4163;
(b) S. Ford, M.R. Lewtas, C.P. Morley, M. Di Vaira, Eur. J. Inorg. Chem. (2000)
933;
CCDC 674790, 674788, 674787, 674789, and 674786 contain
the supplementary crystallographic data for 1b, 9, 11, 12, and 13.
These data can be obtained free of charge from The Cambridge
Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_re-
quest/cif.
(c) J. Chatt, D.M.P. Mingos, J. Chem. Soc., Sect. A (1970) 1243;
(d) R.R. Gukathasan, R.H. Morris, A. Walker, Can. J. Chem. 61 (1983) 2490.
[9] F.A. Cotton, G. Wilkinson, C.A. Murillo, M. Bochmann, Advanced Inorganic
Chemistry, sixth ed., A Wiley-Interscience, John Wiley and Sons, 1999. p. 534.
[10] A. Sivaramakrishna, H. Su, J.R. Moss, Acta Crystallogr., Sect. E63 (2007) m3097.
and references therein.
Acknowledgements
We thank Johnson Matthey, Anglo Platinum Corporation, C*
Change, NRF, UCT for the financial support.
[11] H.C. Clark, L.E. Manzer, J. Organomet. Chem. 59 (1973) 411.
[12] G.B. Robertson, W.A. Wickramasinghe, Acta Crystallogr. C43 (1987) 1694.
[13] C.E. Briant, M.J. Calhorda, T.S.A. Hor, N.D. Howells, J. Chem. Soc., Dalton Trans.
(1993) 1325.
[14] (a) D.A. Slack, M.C. Baird, Inorg. Chim. Acta 24 (1977) 277;
(b) M. Hackett, G.M. Whitesides, J. Am. Chem. Soc. 110 (1988) 1449.
[15] J.X. McDermott, J.F. White, G.M. Whitesides, J. Am. Chem. Soc. 98 (1976) 6522.
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