Synthesis and reactivity of platinacycloalkanes

Article abstract of DOI:10.1016/j.jorganchem.2010.04.011

Novel large platinacycloalkane compounds containing 19- and 21- membered rings of the type L₂Pt(CH₂)_n (L₂ = dppp and n = 18, 20) are synthesized through the ring closing metathesis (RCM) reaction of bis(1-alkeny

Full text of DOI:10.1016/j.jorganchem.2010.04.011

Journal of Organometallic Chemistry 695 (2010) 1627e1633
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Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Synthesis and reactivity of platinacycloalkanes
*
*
Akella Sivaramakrishna, Banothile C.E. Makhubela, John R. Moss , Gregory S. Smith
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:
Novel large platinacycloalkane compounds containing 19- and 21- membered rings of the type L2Pt
(CH2)n (L2 ¼ dppp and n ¼ 18, 20) are synthesized through the ring closing metathesis (RCM) reaction of
bis(1-alkenyl)platinum(II) complexes using Grubbs’ catalysts. These compounds are characterized by
various spectroscopic and analytical techniques. The cross metathesis reactions with different dienes and
substituted alkynes yielded interesting inter- and intra- molecular metathesis reaction products. Various
factors such as concentration, solvent, phosphine ligand and length of the alkenyl chains affect the RCM
reaction significantly to yield different products such as monomeric, dimeric and polymeric species. The
novel chemical reactivity aspects of these title compounds with elemental sulfur, carbon monoxide and
methyl iodide are discussed.
Received 12 February 2010
Received in revised form
9 April 2010
Accepted 15 April 2010
Available online 24 April 2010
Keywords:
Platinacycloalkanes
bis(1-alkenyl)platinum(II) complexes
Ring closing metathesis
Cross metathesis reactions
reactivity
Ó 2010 Elsevier B.V. All rights reserved.
Insertion reactions
1. Introduction
reactions [9e17]. In spite of the importance of medium to large
metallacycloalkanes as intermediates, very little is known about
Catalytic olefin metathesis has emerged as
a
significant
such compounds. Noteworthy, up to now, few higher metal-
lacycloalkanes have been prepared and characterized [18a].
In the present paper, we report the synthesis of new medium to
large ring platinacycles of the type L2M(CH2)n (where n ¼ 8, 18, 20;
L2 ¼ dppp ordppe) fromtheir bis(1-alkenyl) precursors, [19] i.e. with
up to a 21- membered ring compound by this route (Scheme 1).
This RCM method can also be extended to even number metal-
lacycloalkane compounds [20] as well as other metals with a variety
of ligand systems [21]. We also report the syntheses and spectro-
scopic characterization of interesting platinacycles through inter-
and intra- molecular ring closing metathesis reactions and also
describe the reactivity of these compounds.
synthetic tool for the synthesis of a wide range of organic and
polymeric materials, through the construction of carbonecarbon
bonds [1]. The scope of metal containing olefin metathesis in the
synthesis of coordination and organometallic compounds remains
relatively limited [2]. Various metallocene-containing species
including dendrimers, polymers, and ansa-metallocenes have been
prepared using either RCM, cross metathesis, or ring opening
metathesis polymerization (ROMP) reactions [3]. Polymers con-
taining main group elements such as Sn and Si have also been
prepared using the acyclic diene metathesis reaction (ADMET) [4].
The most noteworthy are the creative efforts from the laboratory of
Gladysz in applying RCM to a variety of metal compounds with
phosphine ligands bearing terminal alkenes, which resulted in
novel compounds including sterically shielded linear gyroscope-
like molecules [5,6].
2. Results & discussion
Very recently, we have reported a synthetic route for the
preparation of medium to large metallacycloalkanes using the RCM
route with Grubbs’ catalysts [7,8]. These metallacycloalkanes are an
important class of organometallic compounds which have been
known for many years to be key intermediates in useful catalytic
Platinacycloalkane compounds are relatively stable to moderate
temperatures i.e. ca. 80 ꢀC, but quite unstable above 100 ꢀC. The
stability of these compounds strongly depends on the nature of
ligand as shown in the following trend: diphosphine
>>> PPh3 > SMe2 >> COD > 1,10-phenanthroline > CH3CN]CO. It
can be seen that the chelating nature of diphosphine ligands gives
much stability than the other ligands. The stability of metal-
* Corresponding authors. Tel.: þ27 21 650 5279; fax: þ27 21 650 5195
E-mail addresses: John.Moss@uct.ac.za (J.R. Moss), Gregory.Smith@uct.ac.za (G.S.
Smith).
lacycloalkanes containing no substituents on the b-carbons follows
the trend: Pt >> Pd > Ni [21].
0022-328X/$ e see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2010.04.011

1628
A. Sivaramakrishna et al. / Journal of Organometallic Chemistry 695 (2010) 1627e1633
NMR also indicated a broad signal at
d 45.25e47.34 with platinum
satellites (JPteP ¼ 1725 Hz). Formation of monomeric and frag-
(CH2)nCH=CH2
(CH2)nCH=CH2
L
L
Cl
Cl
2 moles
L
L
mented dimeric species was observed in mass spectral data.
BrMg(CH2)nCH=CH2
Pt
Pt
[n = 3, 8, 9]
Et2O
L
L
Concentrated
solution
L
L
2a, n = 3; L2 = dppp or dppe
2b, n = 8; L2 = dppe
2c, n = 9; L2 = dppp
2d, n = 2; L = PPh3
Pt
1
Pt
Pt
Grubbs'
catalyst
L
L
n
L2 = Ph2P(CH2)3PPh2 (dppp) or
= Ph2P(CH2)2PPh2 (dppe) or
L = PPh3
2a
5, Polymer
Grubbs'
Catalyst
(1).
CH2Cl2
(5 mol%)
2.1.2. Effect of diphenylacetylene on RCM of 2(.dppp)
L
The RCM reaction of 2a(dppp) was carried out in the presence of
2 moles of diphenylacetylene (Scheme 2). After 6 h of reflux in
CH2Cl2, the reaction yielded a mixture of products including 3a
(platinacyclononene, m/z ¼ 717.6) as a major species (Fig. 1). A
novel and unexpected product, 6 (m/z ¼ 891.3) was also obtained
via the formation of new CeC bonds, through insertion of diphe-
nylacetylene into the metallacycle. 1H NMR spectra showed
a complex pattern of internal alkene proton signals. 31P NMR
Pd/C, H2
n
Pt
L
n
n
L
Pt
L
n
3a, n = 3; L2 = dppp or dppe
3b, n = 8; L2 = dppe
3c, n = 9; L2 = dppp
3d, n = 2; L = PPh3
4a, n = 3; L2 = dppp or dppe
4b, n = 8; L2 = dppe
4c, n = 9; L2 = dppp
4d, n = 2; L = PPh3
indicated a broad multiplet at
d
3.45 (JPteP ¼ 1624 Hz) and a singlet
at 5.17 ppm (JPteP ¼ 1516 Hz). This multiplet could be due to the
presence of various cis and trans isomers of the products 3a and 6.
According to our earlier reports, 31P NMR examination of products
derived from RCM reactions of 2a(dppp) alone indicates the pres-
ence of different conformations of platinacycloalkenes in solution,
which also show a multiplet with the same coupling constants
(1JPteP ¼ 1620 Hz) [8].
cis and trans-isomers
Scheme 1. Preparation of odd-membered platinacycles.
2.1. Ring closing metathesis
The bis(1-alkenyl)platinum(II) complexes 2b and 2c were
prepared by the transmetalation reaction of the 1-alkenyl Grignard
reagents with the corresponding dichloroplatinum(II) precursors as
reported earlier for 2a and 2d [7,8]. These were then readily con-
verted into the platinacycloalkenes 3b and 3c using the ring closing
metathesis reaction (RCM) with Grubbs’ catalysts in CH2Cl2, and
obtained as colourless solids in high yield after recrystallization
from CH2Cl2/diethyl ether. The hydrogenation of these compounds
yielded the largest known platinacycloalkanes, 4b and 4c in high
yields (Scheme 1). The 31P{1H} NMR spectra of 4 in C6D6 displayed
a singlet with Pt-satellites at 3.4 ppm (IJPteP ¼ 1620 Hz), which is
quite similar to the precursor compounds (2, 3).
Recently, we have reported that the RCM reactions are sensitive
to the experimental conditions such as tertiary phosphine ligand,
temperature, solvent, length of alkenyl chains, catalyst and
concentration used [8]. Due to the steric, electronic and chelating
effects of ligands, the role of the donor ligand system in 2 plays an
important part in the RCM reactions. PPh3 enhances the rate of
reaction with Grubbs’ catalyst when compared to the diphosphine
ligands. Both the rate of conversion during RCM (i.e. 2 / 3) and
thermal stability of 2 increases from: PPh3 < diphosphine. It is
interesting to note that the length of alkenyl chain also has
a substantial effect on the rate of the RCM reaction [8, 21(a)]. It has
been found that the rate of the RCM reaction is enhanced by the use
of the Grubbs’ 2nd generation catalyst and the longer chains
undergo faster RCM reaction. However, this reaction is concentra-
tion dependent.
Hydrogenation of this mixture showed two singlets for 4a and 7
in the 31P NMR spectrum consistent with the disappearance of
Ph
CH2Cl2, 50 oC, 6h
L
2
Pt
+
Grubbs' 1st Gen.
catalyst
L
Ph
2a(dppp)
L
Ph
L
L
Pt
+
Pt
L
Ph
3a(dppp)
6
Pd/C,
H2
L
Ph
L
L
Pt
+
Pt
L
Ph
4a(dppp)
7
175 oC, 2h
2.1.1. Effect of concentration
We have also shown that the nature of product formed during
the RCM reaction was strongly dependant on the concentration of
the precursors, since the dimeric species were isolated along with
their corresponding monomeric species. When the RCM reaction
was carried out with 2a(dppe) in a highly concentrated solution
(2M), a viscous oily mass (5) was obtained as product, which is due
to the polymerization of Pt-alkenyls (Eq.1). 1H NMR spectrum of 5
Ph
+
+
+
Ph
8
Scheme 2. Metathesis followed by hydrogenation of 2a(dppp) in the presence of
shows broad internal alkene signals in the range
d
4.90e6.93. 31P
diphenylacetylene.

A. Sivaramakrishna et al. / Journal of Organometallic Chemistry 695 (2010) 1627e1633
1629
SCAN GRAPH. Flagging=Low Resolution M/z. Filter=[Int:0.1%. ].Ctd=[Thr:300µV, Min.Hgt:300µV, Min.Wid(Mlt):10(7), Inc:50%, Res:10
Scan 11#1:02. Entries=1108. Base M/z=154.2. 100% Int.=0.06192. FAB. POS.
100
154.2
90
80
717.6
70
60
606.3
50
40
885.2
30
297.4
826.2
20
10
0
675.9
165.2
273.3
772
530.4
424.4
378.3
961.6
500.5
100
200
300
400
500
Low Resolution M/z
600
700
800
900
1000
Fig. 1. Mass spectrum of mixture of compounds 3a and 6.
isomeric forms of 3a and 6. As expected, thermal decomposition of
these products indicated the formation of 1-octene, 1,7-octadiene
and n-octane by GC-MS, as well as diphenylacetylene derivative 8
(m/z ¼ 290) (Scheme 2).
intramolecular metathesis reactions. The 31P NMR spectrum also
showed the appearance of very close singlets and a multiplet at
d
46.8 (JPteP ¼ 1617 Hz) indicating that these cross metathesis
products contain similar species as their precursors. A similar trend
was observed with 2a(dppe) complex. The mass spectrum of the
isolated compound 9, showed mass fragments corresponding to: Pt
(dppp)þ (m/z ¼ 607.4), 9-membered - ring (m/z ¼ 718.6), 10-
membered diene- ring (m/z ¼ 733.8), 12-membered diene- (m/
z ¼ 761.2), 15-membered ring (m/z ¼ 799.6), 22-membered ring
(m/z ¼ 900.6), 23-membered ring (m/z ¼ 912.4) and other species
containing lower as well as higher mass values. Products from self
metathesis of 1,7-octadeine were not found. Hydrogenation of 9
yielded the known compound 10 [8] in good yields and the 31P
2.1.3. Cross metathesis
Studies on the influence of various dienes during the RCM
reaction of bis(1-alkenyl)platinum(II) complexes clearly indicated
the formation of a variety of products, depending on the experi-
mental conditions.
Reaction of 2a(dppp) complex with 1,7-octadiene in the pres-
ence of 5 mol % of Grubbs’ catalyst showed the formation of new
broad internal alkene signals and the reaction was complete within
12 h at 45 ꢀC (Scheme 3). The broad multiplet signals in the 1H NMR
NMR spectrum of 10 showed a singlet at
d 3.45 with similar JPteP
spectrum (in a range of
d
4.2e4.4 and
d
5.2e5.8) are due to the
values as the precursors (Scheme 3).
formation of various products through, intermolecular and
When the RCM reaction was carried out with 2d in the presence
of 1,5-hexadiene, the terminal alkene protons in 1H NMR spectrum
were unchanged even after refluxing the reaction mixture for
several days in the presence of Grubbs’ catalyst added batch-wise
(Eq. (2)). The formation of 11 with internal alkene protons was
significant in 1H NMR spectrum. This could be due to the cross
metathesis reaction of 1,5-hexadiene molecules with each alkenyl
chain of the precursor without closing the ring. Mass spectrum
indicated the molecular ion (m/z ¼ 911.5) and evidence of other
mass fragments as expected.
RCM, CH2Cl2
L
L
Pt
+
Grubbs 1st Gen.
Catalyst
2a.dppp
L
L
Pt
Ph3P
9
Ph3P
Ph3P
CH2Cl2
Pt
+
Pt
Grubbs 1st Gen.
Catalyst
Ph3P
Pd/C, H2
2d
11
L
(2).
Pt
L
2.2. Reactivity
10
The interest in reactions of metallacycloalkanes resides in the
scope they offer for functionalising hydrocarbons to give valuable
Scheme 3. Ring closing metathesis reaction of 2a(dppp) in the presence of 1,7-
octadiene.

1630
A. Sivaramakrishna et al. / Journal of Organometallic Chemistry 695 (2010) 1627e1633
organic compounds, such as alkenes, aldehydes, acids, ethers and
thiolates [22e27]. Thermal decomposition studies of metal-
lacycloalkanes have been investigated due to their importance as
key intermediates in ethylene oligomerization reactions [7,8,28].
We report herein the results of some CO and S8 insertion reactions
with platinacycles, to give interesting new compounds as shown in
Scheme 4.
2.2.2. Reaction of elemental sulfur
Very little work has been reported in the literature on the
insertion of elemental sulfur (S8) into transition metal-carbon
bonds [32]. Some nickel(II)-thiolate complexes obtained from
insertion of sulfur have been reported [33]. Our studies indicated
from mass spectrometry, the formation of the sulfur di-inserted
product (Scheme 4) and some traces of metallacyclosulfides. The
latter products are presumed to be due to the presence of S4, S6 and
other fragments in polar solvents, according to literature [34]. The
ring size of the platinacyclosulfides strongly depends on the reac-
tion conditions, especially temperature.
The reaction of the platinacyclononane 4a with S8 resulted in
a mixture of products including a platinacyclosulphide (14 in
traces) and 15 which is formed by the insertion of two sulfur atoms
from S8 into the two PteC bonds. A peak assigned to the dppp
ligand in an environment containing PteS bonds was observed in
2.2.1. Insertion of CO
Extensive work has been published on the insertion of CO into
transition metal-carbon bonds. Generally all the metals have been
shown to undergo CO insertion, except for Nb, Ta, Tc, Cu, Ag, and Au
[22e27]. Only a small number of investigations of CO insertion into
Pt-alkyl complexes have been undertaken [27]. Insertion of some
neutral and cationic complexes of platinum into PteC bonds has
been demonstrated [29]. The carbonylation reaction was followed
by IR spectroscopy. This reaction proved to be relatively slow, and
this could principally be due to the strong metal-carbon bond seen
in most 5d transition metal complexes [27]. The di-acyl compound
12 (Scheme 4) was obtained in a reasonable yield and its formu-
lation was confirmed by the appearance of bridging carbonyl bands
the region of
d
ꢁ3.23 ppm in the 31P NMR spectrum of the product.
Similar products have also been seen in the reaction of S8 with
platinum bis(1-alkenyl) complexes and the mechanism leading to
these platinacyclosulphides is still not understood [35]. The di-
insertion of sulfur into the PteC bonds may proceed through
a mechanism similar to that reported by Legzdins and co-workers
[36].
in its IR spectrum as well as a peak in the region of
d C
203 in the 13
NMR spectrum. These formulations agree well with our previous
reports [30]. A mechanism leading to this product may proceed via
an intermediate 5-coordinate platinum species [31].
2.2.3. Oxidative addition of 4a(dppp) with methyl iodide
Attempts to insert oxygen into the PteC bonds of 4a failed as the
reaction mixtures decomposed completely in the presence of either
oxygen or hydrogen peroxide. The expected product 13 (Scheme 4)
could not be identified. This could be due to the radical reaction of
nascent oxygen in solution.
The reaction of methyl iodide with 4a(dppp) yielded known
products 16 and 17 [37] (Scheme 4) at 175 ꢀC through the formation
of a hexacoordinate platinum(IV) complex. This oxidative addition
reaction strongly depends on the nature of ligands. Surprisingly,
the formation of cyclooctane was not observed in contrast to the
14
S
S
L
L
S
Pt
Pt
L
L
S
S
S
15
S8, Toluene
Excess S8, Toluene
O
O
O
L
CO
L
L
L
L
Pt
Pt
Pt
L
O2/H2O2
O
4
12
13
MeI
I
L
L
I
Pt
Pt
+
+
I
L
Me
L
17
16
1-nonene
1,7-diiodooctane
+
8-iodo-1-octene +
Scheme 4. Reactivity studies of platinacyclononane.

A. Sivaramakrishna et al. / Journal of Organometallic Chemistry 695 (2010) 1627e1633
1631
smaller platinacycloalkenes [18b]. The other organic products such
as 1-nonene and 8-iodo-octene were formed by cross reductive
elimination.
(m, 20H, Ph); 5.48e5.62 (m, 2H, ]CH); 4.67e4.77 (m, 4H, ]CH2);
2.43e2.56 (m, 4H, PeCH2); 0.86e2.08 (m, 32H, eCH2); 13C{1H}
NMR: 139.3, 133.2 (d, CH]), 127.7e133.4 (m, Ph), 113.8, 114.1 (d, ]
CH2), 36.1, 33.9, 33.7, 23.7, 23.4, 22.6, 22.1; 31P{1H}:
d 45.5 (s)
2.2.4. UV-irradiation studies
(JPteP ¼ 1617 Hz). Anal. Calcd for C46H62P2Pt: C, 63.36; H, 7.17.
The UV-irradiation studies of 4a(dppp) and 4b(dppe) yielded
a very complex mixture of products and the reaction solutions
changed from colourless to yellow brown and finally to reddish
brown and these products could not be isolated and characterized.
However, the distribution of organic products was very similar to
the thermal decomposition results reported previously [21a,b].
Found: C, 63.96; H, 7.76.
4.2. Preparation of compound 2c
PtCl2(COD) (326 mg, 0.871 mmol) in diethyl ether (20 mL) was
cooled down to T ¼ ꢁ78 ꢀC and 2.7 mL of 1-undecenyl Grignard
reagent (0.98 M, 2.61 mmol) was added. The solution was brought
to around 0 ꢀC and then stirred until the solution became clear. To
this, dppp (359 mg, 0.871 mmol) was added and stirred for 36 h
until a clear solution was formed. The reaction mixture was worked
up as described above. The obtained viscous colourless oily mass
was dried under high vacuum for several hours. For 2c; yield 82%;
3. Conclusions
In conclusion, we have prepared medium to large ring metal-
lacycloalkanes in high yield through a ring closing metathesis
reaction, and that such compounds are quite thermally stable. It is
noteworthy that platinacycloalkane compounds can undergo
a variety of reactions with various substrates depending on the
experimental conditions. We are currently exploring the mecha-
nistic pathways for these interesting reactions. We are also inves-
tigating the reactivity of similar compounds with other metals as
well as even membered ring metallacycloalkanes and cross ring
closing metathesis reactions to prepare novel organometallic
complexes.
1H NMR
d 6.98e7.91 (m, 20H, Ph); 5.69e5.90 (m, 2H, ]CH);
4.91e5.11 (m, 4H, ]CH2); 1.86e2.19 (m, 6H, PeCH2); 0.82e1.68 (m,
36H, eCH2); 31P{1H} 3.84 (s) (JPteP ¼ 1619 Hz). Anal. Calcd for
C49H68P2Pt: C, 64.38; H, 7.50. Found: C, 64.76; H, 8.23.
4.3. Preparation of compound 3b
Compound 2b (225 mg, 0.258 mmol) and Grubbs 1st generation
catalyst (ca. half of 16 mg, 0.0194 mmol, 5 mol%) were added to
30 mL of dichloromethane. The solution was refluxed at 50 ꢀC. After
3 h, the remaining catalyst was added. After another 4 h, the solvent
was removed using a vacuum pump. The residue was purified from
a CH2Cl2/hexane mixture (3 mL: 10 mL) to give 3b as an oily mass.
4. Experimental section
General Considerations: All manipulations were carried out
under a nitrogen atmosphere unless otherwise stated. The solvents
were commercially available and distilled from dark purple solu-
tions of benzophenone ketyl. 1H, and 31P NMR spectra were
recorded on a Bruker DMX-400 spectrometer and all 1H chemical
shifts are reported relative to residual proton resonance in the
deuterated solvents. Mass spectral data was obtained using VG70SE
with 8 kV acceleration and the FAB gun is an Iontech Saddlefield,
using xenon gas and operating at 8 Kv. All matrices were made with
3-nba. Microanalyses were conducted with a Thermo Flash 1112
Series CHNS-O Analyzer instrument. PtCl2(COD) [38], 1-alkenyl
Grignard reagents (BrMgCH2CH2(CH2)nCH]CH2; n ¼ 1, 3, 4, 6)
were prepared according to literature procedures [39]. Compounds
2a(dppp), 2a(dppe) and 2d were prepared as described ear-
lier.[8] PPh2CH2CH2CH2PPh2 (dppp) and PPh2CH2CH2PPh2 (dppe)
were purchased from Aldrich Chemical Co. and used without
further purification. Grubbs’ catalyst (Ru(]CHPh)PCy3)2(Cl)2 and
Palladium, 10 wt. % on activated carbon used as received from
Aldrich.
Yield 88%; 1H NMR:
d 7.31e7.93 (m, 20H, Ph); 5.28e5.46 (m, 2H, ]
CH); 1.88e2.24 (m, 4H, PeCH2); 0.84e1.62 (m, 32H, eCH2); 31P{1H}:
45.47, 45.05, 45.29, 44.98 (isomers) (JPteP ¼ 1617 Hz). Anal. Calcd.
for C44H58P2Pt: C, 62.62; H, 6.93. Found: C, 62.96; H, 7.15.
4.4. Preparation of compound 3c
Compound 2c (206 mg, 0.2254 mmol) and Grubbs 1st genera-
tion catalyst (ca. half of 16 mg, 0.0194 mmol, 5 mol%) were added to
30 mL of dichloromethane. The solution was refluxed at 50 ꢀC. After
4 h, the remaining catalyst was added. After another 4 h, the solvent
was removed using a vacuum pump. The residue was purified from
a CH2Cl2/hexane mixture (1:5) to give 3c as an oily mass. Yield 81%;
1H NMR:
d 7.26e7.81 (m, 20H, Ph); 5.30e5.44 (m, 2H, ]CH);
1.87e2.21 (m, 6H, PeCH2); 0.78e1.82 (m, 32H, eCH2); 31P{1H}:
3.23, 3.41, 3.49, 3.57 (isomers) (JPteP ¼ 1632 Hz). Anal. Calcd. for
C47H64P2Pt: C, 63.71; H, 7.28. Found: C, 64.96; H, 8.15.
4.1. Preparation of compound 2b
4.5. Preparation of compound 4b
A
Schlenk flask was charged with PtCl2(COD) (455 mg,
Compound 3b (125 mg, 0.148 mmol) and 10 mg of Pd/C (10%)
catalyst were added to 25 mL of toluene. After bubbling the
contents of the flask with H2 gas for 2e3 min, the solution was
stirred at 50 ꢀC under ambient pressure of hydrogen (balloon). After
72 h, the solvent was removed under the reduced pressure. The
residue was filtered and purified from a CH2Cl2/hexane mixture
(1:8 v/v) to get a colourless oily mass; Yield 72%; 1H NMR
1.217 mmol) and diethyl ether (25 mL). The mixture was cooled to
T ¼ ꢁ78 ꢀC and 1-decenyl Grignard reagent (3.4 mL, 1.08 M,
3.65 mmol) was added. The solution was brought to around 0 ꢀC
and then stirred until the solution became clear. To this, dppe
(485 mg, 1.217 mmol) was added and stirred for 1h until a clear
solution was formed. The excess Grignard reagent was removed by
hydrolyzing the reaction mixture with 5 mL of saturated aqueous
NH4Cl at ꢁ78 ꢀC. The aqueous layer was washed with 2 ꢂ 5 mL of n-
hexane and the organic layer was separated using a separating
funnel. The solvent was removed from the organic layer under
reduced pressure and the residue was purified from a CH2Cl2/
hexane mixture (1:5) at ꢁ10 ꢀC for 48 h. The colourless oily mass
was separated by decanting the mother liquor and dried under
d
6.90e7.95 (m, 20H, Ph); 1.85e2.22 (m, 4H, PeCH2); 0.51e1.79 (m,
42H, eCH2 and CH3); 31P{1H} NMR: 45.6 (s) (JPteP ¼ 1617 Hz). MS
(FAB, m/z) ¼ 844.3 (Mþ), 593.1 [(dppe)Ptþ].
4.6. Preparation of compound 4c
Compound 3c (142 mg, 0.160 mmol) and 10 mg of Pd/C (10%)
catalyst were added to 25 mL of toluene. A similar procedure was
vacuum for several hours. For 2b; yield 92%; 1H NMR:
d
7.22e7.60

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A. Sivaramakrishna et al. / Journal of Organometallic Chemistry 695 (2010) 1627e1633
used as described above for the hydrogenation reaction. The
4.11. RCM of 2d in the presence of 1,5-hexadiene
residue was filtered and purified from a CH2Cl2/hexane mixture
(1:8 v/v); Yield 82%; 1H NMR:
d
6.99e7.44 (m, 20H, Ph); 1.97e2.23
2d (360 mg, 0.434 mmol), 1,5-hexadiene (180 mg, 2.19 mmol)
and Grubbs 1st generation catalyst (ca. half of 14 mg, 5 mol%) were
added to 30 mL of dichloromethane. The solution was refluxed at
50 ꢀC. After 5 h, the remaining catalyst was added. After another
30 h, the solvent was removed using a vacuum pump. The residue
was purified from a CH2Cl2/hexane mixture (2:5) to give a product
11 as a colourless solid. Yield 82%, m.p. 144e176 ꢀC; 1H NMR:
(m, 6H, PeCH2); 0.55e1.85 (m, 20H, eCH2); 31P{1H} NMR: 2.91 (s)
(JPteP ¼ 1623 Hz). MS (FAB, m/z) ¼ 890.3 (Mþ), 606.3 [(dppp)Ptþ].
4.7. Preparation of polymer 5 from RCM reaction of 2a(dppe)
2a(dppe) (192 mg, 0.2627 mmol) and Grubbs 1st generation
catalyst (ca. half of 12 mg, 5 mol%) were taken in a John-Young NMR
tube. To this, 0.4 mL of C6D6 was added. Then the solution was
heated at 50 ꢀC. After 6 h, the remaining catalyst was added. After
another 6 h, the solvent was removed by the vacuum pump which
gave an oily mass. Attempts to isolate the impurities from the
residue were not successful as the products were sensitive to
preparative TLC and silica gel. Crude yield 68%; 1H NMR:
d 7.05e7.79 (m, 30, Ph); 5.68e5.88 (m, 2H, CH2]CH), 5.33e5.48 (m,
4H, ]CH), 4.91e5.07 (m, 4H, ]CH2), 0.83e2.49 (m, 12H, eCH2); 31
P
{1H}:
d
27.3 (s, JPteP ¼ 1864 Hz). MS (FAB, m/z) ¼ 911.5 [Mþ for 11]
and 719.3 [(PPh3)2Ptþ].
4.12. Carbonylation of 4a(dppp)
4a (242 mg, 336 mmol) was transferred into a 100 mL round
bottom flask and dissolved in dry THF (25 mL). The flask was then
closed with a stopper containing a tap, which was in turn equipped
with a CO gas filled balloon. The tap was opened allowing the gas to
enter the flask while stirring at room temperature for 21 days,
during which the progress of the reaction was monitored by IR
spectroscopy. After 21 days the solvent was removed from the now
pale pink solution to give a light red oil. The oil was recrystallized
from benzene (15 mL) to yield colourless crystals of the product 12.
Yield 77%; m.p. 123e125 ꢀC; 1H NMR (300 MHz, C6D6):
d
6.38e8.46 (m, Ph); 4.24e5.87 (m, ]CH); 0.62e2.90 (m, PeCH2
and eCH2); 31P{1H} NMR: 45.4e47.5 (broad) (JPteP ¼ 1675 Hz). MS
(FAB, m/z) ¼ 703.2 [monomer, 9-membered platinacycloalkene],
815.9 [(dimer)-(dppePt)] and 582.8 [(dppe)Ptþ].
4.8. RCM reaction of 3a(dppp) in the presence of diphenylacetylene
2a(dppp) (202 mg, 0.271 mmol), diphenylacetylene (97 mg,
0.542 mmol) and Grubbs 1st generation catalyst (ca. half of 14 mg,
5 mol%) were added to 30 mL of dichloromethane. The solution was
refluxed at 50 ꢀC. After 5 h, the remaining catalyst was added. After
another 6 h, the solvent was removed using a vacuum pump. The
residue was purified from a CH2Cl2/hexane mixture (2:5) to give
a mixture of products 3a and 6 as a colourless solid. Attempts to
isolate these products from the reaction mixture were not
successful. The reaction mixture as such was used for the hydro-
genation reaction. Yield 82% (mixture of products); 1H NMR:
d
6.93e7e75 (m, 20H Ph); 2.03e2.27 (m, 4H PeCH2); 0.99e1.90 (m,
18H CH2); 13C NMR (100 MHz, C6D6):
d
203.68 (s, 2C);
133.56e133.81 (m, 12C); 129.65 (s, 8C); 127.68 (s, 4C); 32.47 (s, 2C);
30.02 (S, 2C); 29.36 (s, 2C), 27.25 (s, 2C); 22.72. (s, 2C); 20.82 (s, 1C);
31P NMR (121 MHz, C6D6):
d
45.43 (s), J(195PteP) ¼ 2322.13 Hz;
Elemental analysis calculated for C37H42O2P2Pt: C, 57.29; H, 5.46,
Found: C, 57.38; H, 5.64; nmax/cmꢁ1 (DCM): 1606, m, 1673, s (C]O),
LRMS (FAB) C37H42O2P2Pt: m/z ¼ [775.1]þ
d
7.03e7.81 (m, Ph); 4.90, 5.13, 5.50 (t, ]CH); 2.24e2.72 (m,
PeCH2); 0.597e2.0 (m, eCH2); 31P{1H}:
d
3.45 (m, JPteP ¼ 1624 Hz)
4.13. Preparation of compounds 14 and 15
and
d
5.17 (s, JPteP ¼ 1516 Hz) (isomers). MS (FAB, m/z) ¼ 891.3 (Mþ
for 6) and 717.6 (Mþ for 3a(dppp)), 606.3 [(dppp)Ptþ].
4a (292 mg, 0.406 mmol) was transferred into a 100 mL round
bottom flask and dissolved in dry toluene (30 mL). Elemental sulfur
(S8) (25 mg, 0.812 mmol) was added to the solution and it was
stirred at room temperature for 21 days, during which the solution
had turned from colourless to orangeeyellow. The solvent was
removed by rotary evaporation to give a semi-solid crude product,
which was passed through an alumina column eluting with a 50:50
mixture of dichloromethane and hexane. A light yellow band was
collected and after removal of the volatiles a yellow solid was
obtained. This yellow solid was found to contain a mixture of
products 14 and 15 and attempts to separate these products were
unsuccessful. Yield (110 mg); m.p. 112e121 ꢀC (mixture); 31P NMR:
4.9. Hydrogenation of the reaction mixture from 6
126 mg of the product mixture (3a.dppp þ 6) and 10 mg of Pd/C
(10%) catalyst were added to 25 mL of toluene. A similar procedure
was used as described above in 4b for the hydrogenation reaction.
The residue was filtered and purified from a CH2Cl2/hexane mixture
(1:2 v/v); Yield 62%; 1H NMR:
d 7.04e7.86 (m, 20H, Ph); 2.29e2.59
(m, 6H, PeCH2); 0.51e1.93 (m, 20H, eCH2); 31P{1H} NMR:
and 3.53 (JPteP ¼ 1597 Hz).
d 3.49
(121 MHz, CDCl3):
d
ꢁ3.23 (s), J(195PteP) ¼ 2688.59 Hz; LRMS (FAB)
C35H42S2P2Pt: m/z ¼ [783.19]þ. C27H26S4P2Pt: m/z ¼ [767.11]þ.
4.10. RCM reaction of 2a(dppp) in the presence of 1,7-octadiene
2a(dppp) (214 mg, 0.287 mmol), 1,7-octadiene (32 mg,
0.0181 mmol) and Grubbs 1st generation catalyst (ca. half of 12 mg,
5 mol%) were added to 15 mL of dichloromethane. The solution was
refluxed at 50 ꢀC. After 5 h, the remaining catalyst was added. After
another 6 h, the solvent was removed using a vacuum pump. The
residue was purified from a CH2Cl2/hexane mixture (2:5) to give
a product 9 as colourless oil. Yield 58% (mixture of products); 1H
4.14. Oxidative addition of 4a.dppp with methyliodide
3
mL of methyliodide was added to 4a.dppp (156 mg,
0.217 mmol). The mixture was stirred for 72 h at room temperature.
After removing all the volatiles under reduced pressure, the
obtained colourless product was heated in an oil bath at 175 ꢀC for
8 h. The pyrolysis products were found to be [dppp]PtMeI, [dppp]
PtI2 and 1-nonene as major species. The other minor products were
1,7-diiodooctane and iodooctane. The organic products were
analyzed by GC-MS and the complexes [dppp]PtMeI and [dppp]PtI2
were identified by NMR spectroscopy [40].
NMR:
d 7.16e7.75 (m, 20H, Ph); 5.06e5.56 (m, 4H, ]CH);
0.60e2.58 (m, 26H, PeCH2 and eCH2); 31P{1H} NMR:
d 5.32 (m,
JPteP ¼ 1617 Hz). MS (FAB, m/z) ¼ 799.6 (Mþ for 9) and 606.3
[(dppp)Ptþ].

A. Sivaramakrishna et al. / Journal of Organometallic Chemistry 695 (2010) 1627e1633
1633
4962;
4.15. UV-irradiation studies
(j) L. Wang, T. Shima, F. Hampel, J.A. Gladysz, Chem. Commun. (2006) 4075;
(k) L.Y. Wang, F. Hampel, J.A. Gladysz, Angew. Chem. Int. Ed. 45 (2006) 4372;
(l) N. Lewanzik, T. Oeser, J. Blumel, J.A. Gladysz, J. Mol, Catal. A: Chem. 254 (2006)
20.
Irradiations were carried out with a Englehard Hanovia Lamp
(125 W) at a distance of 16 cm from the reaction vessel. 4a.dppp
(24 mg, 0.033 mmol) or 4b.dppe (28 mg, 0.04 mmol) was trans-
ferred to a J. Young NMR tube and toluene-d8 (0.9 mL) was added.
The resulting solution was subjected to three freezeethaw cycles,
and then allowed to warm to room temperature. The colourless
solution was then irradiated for 9 h.
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A. Sivaramakrishna, Chem. Commun. (2005) 3865.
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3541.
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of Organotransition Metal Chemistry. University Science Books, Mill Valley,
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[10] R.H. Grubbs, Tetrahedron 60 (2004) 7117.
[11] R. Emrich, O. Heinemann, P.W. Jolly, C. Kruger, G.P.J. Verhovnik, Organome-
tallics 16 (1997) 1511.
Acknowledgements
[12] T. Agapie, S.J. Schofer, J.A. Labinger, J.E. Bercaw, J. Am. Chem. Soc. 126 (2004)
1304.
Financial support from the AngloPlatinum Corporation, DST
Centre of Excellence in Catalysis (c* change), NRF, UCT and gifts of
chemicals from Johnson & Matthey are gratefully acknowledged.
The authors also wish to thank Ian Rogers for his valuable input into
the study.
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