Palladium(II) and platinum(II) 2-(methoxycarbonyl)ethylselenolates: Synthesis, spectroscopy, structures and their conversion into metal selenide

Article abstract of DOI:10.1016/j.jorganchem.2006.12.003

A diselenide, (MeOOCCH₂CH₂Se)₂ (1) has been prepared by esterification of (HOOCCH₂CH₂Se)₂ in methanol. The reductive cleavage of Se-Se bond in 1 by NaBH₄ in methanol generates Me

Full text of DOI:10.1016/j.jorganchem.2006.12.003

Journal of Organometallic Chemistry 692 (2007) 1546–1556
www.elsevier.com/locate/jorganchem
Palladium(II) and platinum(II) 2-(methoxycarbonyl)ethylselenolates:
Synthesis, spectroscopy, structures and their conversion
into metal selenide
a
a,
b
b
Liladhar B. Kumbhare , Vimal K. Jain *, Prasad P. Phadnis , Munirathinam Nethaji
a
Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400 085, India
Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore 560 012, India
b
Received 10 October 2006; received in revised form 30 November 2006; accepted 3 December 2006
Available online 9 December 2006
Abstract
A diselenide, (MeOOCCH2CH2Se)2 (1) has been prepared by esterification of (HOOCCH2CH2Se)2 in methanol. The reductive cleav-
age of Se–Se bond in 1 by NaBH4 in methanol generates MeOOCCH2CH2SeNa. The latter in different stoichiometries reacts with
[M2Cl2(l-Cl)2(PR3)2] to give a variety of products of compositions [M2Cl2(l-SeCH2CH2COOMe)2(PR3)2] (2); [M2Cl2(l-Cl)-
(l-SeCH2CH2COOMe)(PR3)2] (3); [Pd2(SeCH2CH2COOMe)2(l-SeCH2CH2COOMe)2(PR3)2] (4); [Pd3Cl2(l-SeCH2CH2COOMe)4(PR3)2]
(5). Treatment of complexes 2 with [M2Cl2(l-Cl)2(PR3)2] affords complexes 3 in nearly quantitative yield. The formation of various prod-
ucts in these reactions is sensitive to stoichiometric ratio of reactants employed. This enables interconversion of various complexes by
manipulating mole ratios of appropriate starting materials. A homoleptic palladium complex, [Pd(SeCH2CH2COOMe)2]6 (6) was iso-
lated from a reaction between Na2PdCl4 and MeOOCCH2CH2SeNa. All these complexes have been characterized by elemental analysis,
IR, UV–Vis and NMR (1H, 13C, 31P, 77Se, 195Pt) spectroscopy. Structures of trans-[Pd2Cl2(l-SeCH2CH2COOMe)2(PPh3)2] (2d),
[Pt2Cl2(l-Cl)(l-SeCH2CH2COOMe)(PnPr3)2] (3e), [Pd3Cl2(l-SeCH2CH2COOMe)4(PnPr3)2] (5) and [Pd(SeCH2CH2COOMe)2]6 (6) have
been established unambiguously by X-ray crystallography. In these complexes, there are bridging selenolate ligands with their uncoor-
dinated ester groups. Compound 6 has a centrosymmetric Pd6Se12 hexagon in which every two palladium atoms are bridged by selenolate
ligands. Thermal behaviour of some complexes has been investigated. Pyrolysis of compound 2b in tributylphosphate at 195 ꢀC gave
Pd17Se15 nanoparticles which were characterized by XRD and EDAX.
ꢁ 2006 Elsevier B.V. All rights reserved.
Keywords: Palladium; Platinum; Selenolates; NMR; Palladium selenide; X-ray
1. Introduction
enides (MxEy; M = Pd or Pt; E = S, Se, Te) for electronic
devices has been demonstrated [3,4]. The area of metal
chalcogenolates is dominated by molecules containing
M–SR linkage. In most cases these molecules are isolated
as nonvolatile, insoluble (or sparingly soluble) polymeric
species, limiting their utility as precursors for the synthesis
of metal chalcogenides. Several strategies have been devel-
oped to suppress polymerization, the use of hybrid ligands
has been quite successful. Recently we have employed
internally functionalized hemi-labile ligands like pyridine-
2-chalcogenolates [5,6] and dimethylaminoalkyl chalcogen-
olates, Me2N(CH2)nEꢀ [7–12]. These ligands have not only
shown versatile coordination chemistry but their complexes
The chemistry of platinum group metals with chalcogen-
olate ligands has been a subject area of considerable
research for more than two decades [1]. There are several
obvious reasons for the sustained interest in this area as
these complexes show a rich structural diversity [1] and
have relevance in catalysis [2]. More recently, their role
as molecular precursors for the synthesis of metal chalcog-
*
Corresponding author. Tel.: +91 22 2559 5095; fax: +91 22 2550 5151.
E-mail address: jainvk@barc.gov.in (V.K. Jain).
0022-328X/$ - see front matter ꢁ 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2006.12.003

L.B. Kumbhare et al. / Journal of Organometallic Chemistry 692 (2007) 1546–1556
1547
have also served as precursors for the synthesis of metal
chalcogenides [5–7] as well as for the study of metal medi-
ated donor–acceptor interactions [8,9]. The continued
interest in selenium/tellurium containing inorganic materi-
als [13–15] and in pursuance of our work on design and
development of precursors for chalcogenide materials, we
have now synthesized (MeOOCCH2CH2Se)2 and explored
the chemistry of its palladium and platinum complexes.
Results of this work are reported herein.
(l-SeCH2CH2COOMe)(PR3)2] (3) (Scheme 1). The latter
were isolated in quantitative yields on treatment of
[M2Cl2(l-Cl)2(PR3)2] with the complexes 2.
Reaction of [Pd2Cl2(l-Cl)2(PnPr3)2] with 2.7 and
4 equiv. of NaSeCH2CH2COOMe gave [Pd3Cl2(l-SeCH2-
CH2COOMe)4(PnPr3)2] (5) (red solid) and [Pd2(SeCH2-
CH2COOMe)4(PnPr3)2] (4) (red oil), respectively.
Compound 5 was also isolated in poor yields as dispropor-
tionation product when 2b was left for recrystallization.
Reaction of Na2PdCl4 with 2 equiv. of NaSeCH2CH2-
COOMe in methanol afforded a homoleptic hexanuclear
palladium complex, [Pd(SeCH2CH2COOMe)2]6 (6).
2. Results and discussion
2.1. Synthesis
2.2. Spectroscopy
Esterification of (HOOCCH2CH2Se)2 in methanol in the
presence of concentrated sulfuric acid gave the correspond-
ing methyl ester, (MeOOCCH2CH2Se)2 (1), as a yellow
orange oil which can be purified by distillation under vac-
uum. Reductive cleavage of the Se–Se bond in 1 with
sodium borohydride in methanol gave NaSeCH2-
CH2COOMe which was used in situ for the reactions with
palladium and platinum complexes. Reaction of [M2Cl2-
(l-Cl)2(PR3)2] with 2 equiv. of NaSeCH2CH2COOMe gave
binuclear selenolate-bridged complexes of composition,
[M2Cl2(l-SeCH2CH2COOMe)2(PR3)2] (2) which were iso-
lated as a mixture of syn-cis and trans isomers. The reac-
tion in 1:1 stoichiometry, however, afforded mixed
chloro/selenolato bridged cis complexes; [M2Cl2(l-Cl)-
The IR spectra of compound 1 and palladium/platinum
complexes exhibited an absorption band at ꢁ1730 cmꢀ1
due to the carbonyl group. The corresponding complexes
2 and 3 showed a band in the region 302–322 cmꢀ1 assign-
able to mM–Cl stretchings [16]. The electronic spectra of
compound 1 as well as complexes displayed absorptions
in the region 235–439 nm. The absorptions with kmax
<
308 nm can be attributed to the transitions in the electron
rich selenolate group while bands having kmax > 308 nm
may be assigned to a ligand(Se)-to-ligand(PR3) charge
transfer (LL0CT) transition [8,9]. This transition has lower
energy for complexes 3 than the corresponding complexes
2. Aggregation in complexes 5 and 6 further shifts these
[Pd2(SeR')2(μ-SeR')2(PnPr3)2]
[Pd3Cl2(μ-SeR')4(PnPr3)2]
(5)
(4)
4 NaSeR'
2.7 NaSeR'
when M = Pd; R = nPr
(slow disproportionation)
[M2Cl2(μ-Cl)2(PR3)2]
1 NaSeR'
2 NaSeR'
[M2Cl2(μ-Cl)(μ-SeR')(PR3)2]
[M2Cl2(μ-SeR')2(PR3)2]
(2)
[M2Cl2(μ-Cl)2(PR3)2]
(3)
M
PR3
M
PR3
Pd PEt3
Pd PnPr3
Pd PMePh2 2c
2a
2b
Pd PEt3
Pd PnPr3
Pd PMe2Ph 3c
3a
3b
Pd PPh3
Pt PEt3
Pt PnPr3
Pt PnBu3
2d
2e
2f
Pt PEt3
Pt PnPr3
3d
3e
2g
Pd
SeR'
R'Se
Pd
SeR'
R'Se
Pd
SeR'
R'Se
6 Na2PdCl4 + 12 NaSeR'
R'Se
SeR'
-12 NaCl
Pd
Pd
SeR' R'Se
Pd
R'Se
SeR'
R' = CH2CH2COOMe
(6)
Scheme 1.

1548
L.B. Kumbhare et al. / Journal of Organometallic Chemistry 692 (2007) 1546–1556
transition to lower energies due to increased orbital inter-
action. The palladium complexes showed absorptions at
lower energies than the corresponding platinum analogues.
1
The H NMR spectra of complexes 2 showed expected
resonances and peak multiplicities. The 31P{1H} NMR
spectra displayed two signals assignable to cis and trans
isomers. Resonances for platinum complexes were flanked
by the satellites of 195Pt isotope with 1J(195Pt–31P) values of
ꢁ3100 Hz which can be compared with the couplings
reported for [Pt2Cl2(l-ER)2(PR3)2] (E = S, Se, Te) [17–
1
20]. The signal with larger J(Pt–P) value is assigned to
Fig. 2. 77Se{1H} NMR spectrum of [Pt2Cl2(l-SeCH2CH2COOMe)2-
(PEt3)2] (2e) in CDCl3.
the cis isomer [21]. The 195Pt{1H} NMR spectra (Fig. 1)
showed two doublets due to coupling with phosphorus
nucleus. The doublet at higher field (shielding by
1
ꢁ100 ppm) with larger J(195Pt–31P) has been assigned to
(l-ER)(PR3)2] (E = S, Se, Te) [16]. The 195Pt{1H} NMR
the cis isomer. The 77Se{1H} NMR spectra of complexes
2 exhibited three signals (Fig. 2) in the region ꢀ47 to
ꢀ243 ppm. Shielding is higher in platinum complexes than
the analogous palladium derivative which reflects weaker
bonding of the selenolate in the latter, as a consequence
disproportionation is notable (e.g. isolation of complex 5
from 2b). The signal at ꢁꢀ240 ppm in platinum complexes
is attributed to the trans isomer while the remaining two
resonances at lower field have been assigned to the cis iso-
mer. These signals were flanked by platinum satellites with
spectra displayed
a
doublet at ꢁꢀ4000 ppm with
1J(195Pt–31P) of ꢁ3900 Hz.
The 31P{1H} NMR spectrum of 4 exhibited two peaks
which can be assigned to cis and trans isomers. In the
77Se{1H} NMR spectrum four signals at ꢀ271.1, 93.7,
97.7 and 141.5 ppm were observed. The signal at
ꢀ271.1 ppm may be originated from terminal selenolate
group of both the isomers, while the remaining three can
be assignated to bridging selenolate groups (93.7 ppm for
trans and 97.7 and 141.5 ppm for cis isomer). This can be
supported with the fact that the terminal selenolates are
more electron rich than the bridging ones and hence show
greater shielding. Similar pattern has been reported for
125Te NMR chemical shifts of [Cd{TeSi(SiMe3)3}2]2 [1b].
In the 31P{1H} NMR spectra of 5 only a single resonance
is observed suggesting the formation of one isomeric spe-
cies. Except the carbonyl carbon resonance, the 13C{1H}
and 77Se{1H} NMR spectra of 6 displayed two sets of res-
onances. The existence of other oligomeric species in solu-
tion may not be ruled out, although in the solid state
complex 6 has a symmetrical hexameric structure with
bridging selenolate groups (Table 1).
1
1J(195Pt–77Se) of 132–245 Hz. The J(195Pt–77Se) in plati-
num(II) selenolate complexes has been reported in the
range 100–472 Hz [8,20].
1
The H, 31P{1H} and 77Se{1H} NMR spectra of com-
plexes 3 showed one set of resonances indicative of the for-
mation of only one isomer exclusively, although three
isomeric forms, viz. a trans and two cis, are possible. The
former would give two 31P signals while for the latter only
one resonance is expected. The magnitude of 1J(195Pt–77Se)
(ꢁ3900 Hz) is in conformity with the phosphine trans to
the bridging chloride. The cis configuration with phosphine
trans to bridging chloride is reported for [M2Cl2(l-Cl)-
2.3. Crystallography
An ORTEP diagram with atomic number scheme
for trans-[Pd2Cl2(l-SeCH2CH2COOMe)2(PPh3)2] (2d) is
shown in Fig. 3 and selected bond lengths and angles are
given in Table 2. The complex is a centrosymmetric dimer
with syn-trans configuration. Two square planar palladium
atoms are held together by two selenolate groups which
adopt an anti configuration. The four-membered Pd2Se2
ring is planar. In [Pt2Cl2(l-SeEt)2(PEt3)2] the Pt2Se2 ring
is planar [17], but in alkyl thiolate derivatives the M2S2 ring
adopts a non-planar configuration [16]. The Pd–Se dis-
tances trans to phosphine ligands are longer than those
trans to terminal chloride due to strong trans influence of
the PPh3 ligand. The Pd–Se [4,12], Pd–Cl [22,23] and Pd–
P [22,23] distances are in agreement with the reported val-
ues. Owing to the strain in the four membered Pd2Se2 ring,
the Se–Pd–Se angles [82.21(3)ꢀ] are reduced significantly
from the ideal value of 90ꢀ.
Fig. 1. 195Pt{1H} NMR spectrum of [Pt2Cl2(l-SeCH2CH2COOMe)2-
(PEt3)2] (2e) in CDCl3.

L.B. Kumbhare et al. / Journal of Organometallic Chemistry 692 (2007) 1546–1556
1549
Table 1
Crystal data and structure refinement details of trans-[Pd2Cl2(l-SeR0)2(PPh3)2] Æ 2H2O (2d), [Pt2Cl2(l-Cl)(l-SeR0)(PnPr3)2] (3e), [Pd3Cl2(l-SeR0)4(PnPr3)2]
(5), [Pd(l-SeR0)2]6 (6) (R0 = CH2CH2COOMe)
2d
3e
5
6
Chemical formula
Formula weight
Crystal size (mm)
Temperature (K)
Wavelength, MoKa (A)
Crystal system
C44H48Cl2O6P2Pd2Se2
1176.38
0.15 · 0.12 · 0.10
293(2)
0.71073
Triclinic
C22H49Cl3O2P2Pt2Se
983.04
0.32 · 0.27 · 0.22
293(2)
0.71073
Monoclinic
P21/n
C34H70Cl2O8P2Pd3Se4
1374.78
0.34 · 0.28 · 0.22
293(2)
0.71073
Tetragonal
P421c
C48H84O24Pd6Se12
2631.08
0.44 · 0.33 · 0.31
293(2)
0.71073
Triclinic
˚
ꢀ
ꢀ
Space group
P1
P1
Unit cell dimensions
˚
a (A)
10.003(3)
11.383(4)
11.647(4)
77.879(5)
67.470(5)
86.041(6)
1197.5(7)/1
2.492/584
1.83–27.5
ꢀ13 6 h 6 13,
ꢀ14 6 k 6 15,
ꢀ15 6 l 6 15
14058/5562
5562/0/271
0.0489, 0.0756
0.1489, 0.1766
0.733
13.487(3)
18.823(4)
14.763(3)
90.00
112.861(4)
90.00
3453.4(14)/4
9.488/1872
1.85–26.37
ꢀ16 6 h 6 16,
ꢀ23 6 k 6 22,
ꢀ16 6 l 6 18
27401/7048
7048/0/296
0.0423, 0.0783
0.1430, 0.1904
0.687
25.1730(11)
25.1730(11)
16.5105(16)
90.00
90.00
90.00
10462.4(12)/8
4.006/5408
1.81–26.0
ꢀ31 6 h 6 6,
ꢀ25 6 k 6 24,
ꢀ19 6 l 6 20
26842/9159
9159/8/488
0.0552, 0.1226
0.0971, 0.1204
0.919
12.110(3)
12.363(3)
14.297(4)
93.057(5)
˚
b (A)
˚
c (A)
a (ꢀ)
b (ꢀ)
c (ꢀ)
Volume (A )/Z
l (mmꢀ1)/F(000)
111.197(5)
98.359(5)
1961.4(9)/2
6.978/1248
1.83–26.7
ꢀ15 6 h 6 15,
ꢀ15 6 k 6 15,
ꢀ17 6 l 6 17
21128/7964
7964/0/409
0.0462, 0.0934
0.1018, 0.1236
0.899
3
˚
h Range (ꢀ)
Limiting indices
Number of reflections/unique
Number of data/restraints/parameters
Final R1 [I > 2r(I)], xR2
R1, xR2 (all data)
Goodness-of-fit on F2
Table 2
˚
Selected bond lengths (A) and bond angles (ꢀ) for trans-[Pd2Cl2-
(l-SeCH2CH2COOMe)2(PPh3)2] (2d)
Pd1–Se1
Pd1–Se1_2
Pd1–P1
Pd1–Cl1
Se1–C19
C19–C20
C20–C21
2.4590(9)
2.4090(9)
2.3076(16)
2.3480(17)
1.964(7)
C21–O1
C21–O2
C22–O2
P1–C1
P1–C7
P1–C13
Pd–Pd
1.196(9)
1.313(10)
1.418(13)
1.826(6)
1.816(6)
1.817(6)
3.696(1)
1.510(12)
1.509(12)
Se1–Pd1–Se1_2
Pd1–Se1–Pd1_2
Cl1–Pd1–Se1
Cl1–Pd1Se1_2
Cl1–Pd1–P1
81.21(3)
98.79(3)
89.75(5)
167.93(5)
92.69(5)
177.56(5)
96.37(5)
C19–Se1–Pd1
C19–Se1_2–Pd1
Se1–C19–C20
C19–C20–C21
Pd1–P1–C1
99.5(2)
108.4(2)
115.0(5)
113.4(6)
114.9(2)
115.07(19)
111.4(2)
P1–Pd1–Se1
P1–Pd1–Se1_2
Pd1–P1–C7
Pd1–P1–C13
_2 Denotes symmetrical moiety with respect to centre of inversion.
Fig. 3. Molecular structure of trans-[Pd2Cl2(l-SeCH2CH2COOMe)2-
(PPh3)2] (2d) (ORTEP drawn with 50% probability; hydrogen atoms are
omitted for clarity).
The molecular structure of [Pd3Cl2(l-SeCH2CH2COO-
Me)4(PnPr3)2] (5) (Fig. 5) comprises of three distorted
square planar palladium atoms which are held together
by bridging selenolate groups. The metal square planes
are tilted towards each other (plane 1 and plane 2 =
62.08(3)ꢀ, plane 1 and plane 3 = 67.20(5)ꢀ and plane 2
and plane 3 = 50.85(4)ꢀ; where planes 1, 2 and 3 are
through Pd(1), Pd(2) and Pd(3), respectively) resulting in
a zig-zag shape of the molecule. A similar shape is observed
for [Pd3Cl2(l-S-cyclohexyl)4(PMe3)2] [25] and [Pt3(l-SC6-
H4Me-4)4(dppm)2]2+ [26]. The coordination environment
around the central palladium and the peripheral metal
atoms can be defined by the ‘‘PdSe4’’ and ‘‘PdClPSe2’’
The molecule [Pt2Cl2(l-Cl)(l-SeCH2CH2COOMe)-
(PnPr3)2] (3e) (Fig. 4) has a syn-cis configuration with the
phosphine ligands mutually trans to the bridging chloride.
The ester group on Se adopts the axial position relative to
the non-planar ‘‘PtClSePt’’ ring. The two Pt–Se bonds are
essentially the same (Table 3) and are in agreement with the
reported values. Various angles around both the platinum
atoms are normal and fall within the expected range. The
Pt–Se–Pt angle [88.80 (4)ꢀ] is within the range reported
for binuclear chalcogenolate bridged complexes (85.5–
92.0ꢀ) [24].

1550
L.B. Kumbhare et al. / Journal of Organometallic Chemistry 692 (2007) 1546–1556
cores. The phosphine ligands are trans disposed whereas
the –CH2CH2COOMe fragments on bridging selenolates
are in anti conformations. All the four Pd–Se distances
for the central palladium atom are essentially similar
(Table 4), but for peripheral palladium atoms the Pd–Se
distance trans to phosphine is longer than the one trans
to Cl atom. This has been attributed to strong trans influ-
ence of phosphine ligand. Various angles around palladium
atoms are as expected for chalcogenolato-bridged com-
plexes. The Pd–Pd distances (Pd1–Pd2 = 3.352(1) and
˚
Pd2–Pd3 = 3.204(1) A) do not support the existence of
metal–metal interactions. A number of trinuclear palla-
dium complexes have been reported and in general they
have ‘Y’ shape (e.g., [M3(l-S)2(P\P)]2+ [7,27]) or triangular
structures (e.g., [Pd(OAc)2]3 [28]). Only few examples with
linear chain arrangement, [Pd3Cl2(l-S-cyclohexyl)4-
(PMe3)2] [25] and [Pd3(g-allyl)2(l-X)4] (X = OAc, Cl)
[29–31], are reported. The structure of complex 4, to our
knowledge, is the first example of selenolato-bridged linear
trinuclear palladium complex.
The complex [Pd(SeCH2CH2COOMe)2]6 (6) (Fig. 6) has
a centrosymmetric hexameric structure in which each palla-
dium atom has a square planar configuration defined by
PdSe4 core and each ligand moiety bridges two palladium
atoms through Se ends. The PdSe coordination planes
are inclined to each other by planes 1 and 2 = 52.92(2),
planes 2 and 3 = 61.95(2) and planes 1 and 3 = 65.12(2)ꢀ
where planes 1, 2 and 3 are through Pd(1), Pd(2) and
Pd(3), respectively leading to the formation of Pd6Se12
hexagon. The structure is isomorphous to [Pd(SeCH2CH2-
CH2N-Me2)2]6 [32] and thiolate complexes [Pd(SR)2]6
Fig. 4. Molecular structure of [Pt2Cl2(l-Cl)(l-SeCH2CH2COOMe)-
(PnPr3)2] (3e) (ORTEP drawn with 50% probability; hydrogen atoms are
omitted for clarity).
Table 3
˚
Selected bond lengths (A) and bond angles (ꢀ) for [Pt2Cl2(l-Cl)-
(l-SeCH2CH2COOMe)(PnPr3)2] (3e)
Pt1–Se1
Pt2–Se1
Pt1–P1
2.3819(12)
2.3820(12)
2.214(3)
2.217(3)
2.338(3)
2.424(3)
2.430(3)
2.331(3)
1.981(13)
1.48 (2)
C11–C12
C12–O1
C12–O2
C13–O2
P1–C1
P1–C4
P1–C7
P2–C14
P2–C17
P2–C20
1.51 (2)
1.225(18)
1.228(17)
1.60(3)
1.813(13)
1.828(15)
1.829(15)
1.800(12)
1.814(12)
1.805(20)
Pt2–P2
Pt1–Cl1
Pt1–Cl2
Pt2–Cl2
Pt2–Cl3
Se1–C10
C10–C11
Se1–Pt1–Cl2
Se1–Pt2–Cl2
Se1–Pt1–Cl1
Se1–Pt2–Cl3
Pt1–Se1–Pt2
Pt1–Cl2–Pt2
P1–Pt1–Cl1
P1–Pt1–Se1
83.23(8)
83.10(8)
173.11(11)
173.82(11)
88.80(4)
86.73(9)
89.80(13)
95.54(9)
Cl2–Pt1–Cl1
Cl2–Pt2–Cl3
P1–Pt1–Cl2
P2–Pt2–Cl3
P2–Pt2–Cl2
P2–Pt2–Se1
Pt1–Se1–C10
Pt2–Se1–C10
91.36(13)
91.60(13)
178.45(12)
89.99(13)
177.84(11)
95.22(9)
Table 4
˚
Selected bond lengths (A) and bond angles (ꢀ) for [Pd3Cl2(l-SeCH2CH2-
COOMe)4(PnPr3)2] (5)
Pd1–Se1
Pd1–Se2
P1–Pd1
Cl1–Pd1
C31–Se1
C10–Se2
Pd2–Se1
Pd2–Se2
Pd1–Pd2
2.4791(15)
2.4004(15)
2.271(4)
Pd2–Se3
Pd2–Se4
Pd3–Se3
Pd3–Se4
Cl2–Pd3
P2–Pd3
C14–Se4
C27–Se3
Pd2–Pd3
2.4363(15)
2.4237(15)
2.4050(16)
2.4803(16)
2.335(4)
102.7(5)
102.3(4)
2.318(3)
1.935(18)
1.937(12)
2.4267(14)
2.4281(15)
3.352 (1)
2.267(4)
1.953(14)
1.976(12)
3.204 (1)
P1–Pd1–Se1
P1–Pd1–Se2
P1–Pd1–Cl1
Cl1–Pd1–Se1
Cl1–Pd1–Se2
Se2–Pd1–Se1
C31–Se1–Pd1
C31–Se1–Pd2
C10–Se2–Pd1
C10–Se2–Pd2
171.31(11)
89.68(11)
94.00(14)
94.25(10)
176.14(10)
82.02(5)
109.4(7)
109.4(6)
101.8(4)
103.3(4)
Se4–Pd2–Se2
Pd2–Se1–Pd1
Pd1–Se2–Pd2
Pd3–Se3–Pd2
Pd2–Se4–Pd3
98.17(5)
86.20(5)
87.94(5)
82.92(5)
81.63(5)
Se3–Pd3–Se4
P2–Pd3–Se3
Cl2–Pd3–Se3
P2–Pd3–Se4
Cl2–Pd3–Se4
P2–Pd3–Cl2
C27–Se3–Pd3
C27–Se3–Pd2
C14–Se4–Pd2
C14–Se4–Pd3
82.10(5)
92.63(11)
169.14(10)
173.05(12)
95.29(10)
90.72(14)
107.6(4)
107.1(4)
111.8(4)
110.7(4)
Se1–Pd2–Se2
Se1–Pd2–Se3
Se4–Pd2–Se1
Se2–Pd2–Se3
Se4–Pd2–Se3
82.55(5)
99.05(5)
170.07(6)
166.20(6)
82.64(5)
Fig. 5. Molecular structure of [Pd3Cl2(l-SeCH2CH2COOMe)4(PnPr3)2]
(5) (ORTEP drawn with 50% probability; hydrogen atoms are omitted for
clarity).

L.B. Kumbhare et al. / Journal of Organometallic Chemistry 692 (2007) 1546–1556
1551
2.4. Thermal behaviour
The TG curves of [M2Cl2(l-SeCH2CH2COOMe)2-
(PnPr)2] (M = Pd (2b); Pt (2f)) showed a two step decompo-
sition with the formation of Pd17Se15 and Pt5Se4,
respectively as suggested from weight loss (Calc. for
Pd17Se15 = 62.4%; Found = 64%. Calc. for Pt5Se4 =
53.6%; Found = 54%). The complex 2b was pyrolized in
a furnace at 315 ꢀC. The XRD pattern can be compared
with the standard patterns reported for Pd17Se15. Solvo-
thermal decomposition of 2b in TBP at 195 ꢀC for 1 h gave
a black residue which has been identified as Pd17Se15 from
XRD (Fig. 7) [36] and EDAX (Calc.: Pd = 60.4%; Se =
39.6%. Found for 2b: Pd = 62.9%; Se = 37.1% (furnace
heating) and Pd = 63.0%; Se = 37.0% (solvothermal)).
The broadening observed in the XRD peaks of the sample
obtained from complex 2b suggested that the particles were
in the nanometer regime.
Fig. 6. Molecular structure of [Pd(l-SeCH2CH2COOMe)2]6 (6) (ORTEP
drawn with 50% probability; except C–Se, other atoms of selenolate
ligands as well as all hydrogen atoms are omitted for clarity).
3. Experimental
(R = Prn [33], CH2COOMe [34]). The Se–Pd–Se angles
around individual palladium atom are acute (ꢁ82ꢀ; within
the ring plane) and obtuse (ꢁ97ꢀ, parallel to the ring axis)
while diagonal angles deviate slightly from ideal value of
3.1. General
Microanalyses were carried out on a Carlo-Erba EA-
1110 CHN-O instrument. UV–Vis absorption spectra were
recorded in CH2Cl2 on a Chemito Spectrascan double
˚
180ꢀ. The average Pd–Se bond distance of 2.439 A (Table
5) can be compared with that reported for
˚
[Pd(SeCH2CH2-CH2NMe2)2]6 (2.437 A) [32] and related
selenolato-bridged
CH2NMe2)2] (2.3858 (7) and 2.4037(7) A) [10] and
[Pd2(SePh)4(PPh3)2] (2.464(2), 2.494(2) A) [35]. The Pd–
Pd separation of 3.1656(10) and 3.2082(10) A is shorter
complexes,
[Pd2Cl2(l-SeCH2CH2-
100
80
60
40
20
0
˚
˚
˚
than the sum of the van der Waals radii for two Pd atoms
˚
(3.26 A). These distances can be compared to
[Pd(SeCH2CH2CH2NMe2)2]6.
Table 5
˚
Selected bond lengths (A) and bond angles (ꢀ) for [Pd(l-SeCH2CH2-
COOMe)2]6 (6)
Pd1–Se1
Pd1–Se2
Pd1–Se3
Pd1–Se6_2
Pd2–Se2
Pd2–Se3
Pd2–Se4
Pd2–Se5
Pd3–Se4
2.4405(11)
2.4348(11)
2.4467(11)
2.4419(11)
2.4353(11)
2.4396(11)
2.4441(11)
2.4337(11)
2.4427(12)
Pd3–Se5
Pd3–Se6
Pd3–Se1_2
Se1–C1
Se2–C5
Se3–C9
Se4–C17
Se5–C21
Se6–C13
2.4413(12)
2.4368(12)
2.4397(12)
1.971(8)
1.984(9)
1.984(8)
1.973(8)
1.977(8)
1.987(9)
20
30
40
50
60
80
60
40
20
0
Se2–Pd1–Se1
Se1–Pd1–Se3
Se1–Pd1–Se6
Se2–Pd1–Se3
Se2–Pd1–Se6_2
Se6_2–Pd1–Se3
Se2–Pd2–Se3
Se2–Pd2–Se4
Se5–Pd2–Se2
Se5–Pd2–Se3
Se3–Pd2–Se4
Se5–Pd2–Se4
178.25(4)
Se6–Pd3–Se1_2
Se6–Pd3–Se5
Se6–Pd3–Se4
82.79(3)
175.29(4)
97.31(4)
82.38(3)
97.11(4)
175.06(4)
84.59(4)
84.24(4)
82.31(3)
82.07(4)
80.88(3)
80.91(3)
96.16(4)
82.66(3)
83.95(3)
97.21(4)
178.71(4)
84.09(4)
177.30(4)
96.10(4)
177.96(4)
97.22(4)
82.51(4)
Se5–Pd3–Se4
Se1_2–Pd3–Se5
Se1_2–Pd3–Se4
Pd1–Se2–Pd2
Pd1–Se3–Pd2
Pd2–Se5–Pd3
Pd2–Se4–Pd3
Pd3–Se1_2–Pd1–2
Pd3–Se6–Pd1_2
20
30
40
50
60
2θ
Fig. 7. XRD pattern of Pd17Se15 obtained from [Pd2Cl2(l-SeCH2CH2-
COOMe)2(PnPr3)2] (2b) by heating in (a) furnace, (b) TBP.
_2 Denotes symmetrical moiety with respect to centre of inversion.

1552
L.B. Kumbhare et al. / Journal of Organometallic Chemistry 692 (2007) 1546–1556
1
beam UV–Vis spectrophotometer. H, 13C{1H}, 31P{1H},
77Se{1H} and 195Pt{1H} NMR spectra were recorded in
CDCl3 on a Bruker DPX-300 NMR spectrometer operat-
ing at 300, 75.47, 121.49, 57.24 and 64.52 MHz, respec-
tively and chemical shifts are relative to internal CHCl3
methanolic solution (10 cm3) of NaSeCH2CH2COOMe
[prepared from (MeOOCCH2CH2Se)2 (141 mg,
0.43 mmol) and NaBH4 (32 mg, 0.84 mmol)]. Reaction
mixture was stirred under argon for 1 h to obtain an
orange solution. The solvents were evaporated under vac-
uum and the residue was extracted with dichloromethane
(20 cm3). The dichloromethane solution was passed
through a Florisil column (0.5 cm · 7 cm) and dried to
give an orange oil which was dissolved in CH2Cl2–ethyl
acetate–hexane mixture and refrigerated to yield orange
crystals of the title complex in 45% yield (159 mg);
mp = 99–100 ꢀC. Anal. Calc. for C20H44Cl2O4P2Pd2Se2:
C, 28.2; H, 5.2. Found: C, 27.8; H, 5.1%. IR (Nujol) m,
cmꢀ1: 1728 (C@O); 314 (Pd–Cl). UV–Vis (CH2Cl2), k (e,
for H and 13C, external 85% H3PO4 for 31P{1H}, Me2Se
1
for 77Se (secondary reference Ph2Se2, d 463 ppm) and
Na2PtCl6 in D2O for 195Pt{1H}. TG curves were obtained
at a heating rate of 10 ꢀC minꢀ1 under flowing argon on
a Setaram 92-16.18 instrument. Solvothermal decomposi-
tion of [Pd2Cl2(l-SeCH2CH2COOMe)2(PnPr3)2] (2b) was
carried out by adding a saturated dichloromethane solu-
tion of the complex to preheated tributyl phosphate
(TBP) at 195 ꢀC with stirring under an argon atmosphere.
The black residue was separated by centrifugation which
was repeatedly washed with ethanol and dried under vac-
uum. Powder XRD patterns were recorded on a Philips
PW 1710 using CuKa radiation.
M
ꢀ1 cmꢀ1): 236 (2.7 · 104), 274 (1.8 · 104), 340
(1.9 · 104) nm. 1H NMR (CDCl3): 1.22 (m, 18H,
PCH2CH3); 1.92 (m, 12H, PCH2–), 2.79 (q) 2.88 (q)
(SeCH2 for cis and trans); 3.06 (t, 8 Hz, –CH2–); 3.22–
3.26 (m, –CH2–); 3.64, 3.70 (each s, COOMe). 31P{1H}
NMR (CDCl3): 21.7; 23.6 (s). 77Se{1H} NMR (CDCl3):
ꢀ47.0 (t, 2J(77Se–31P) = 135 Hz, trans isomer); ꢀ74.7,
ꢀ99.8 ppm (each s, cis isomer).
3.2. Materials
The complexes, Na2PdCl4, K2PtCl4 and [M2Cl2(l-Cl)2-
(PR3)2] (M = Pd, Pt; PR3 = PEt3, PnPr3, PnBu3, PMe2Ph,
PMePh2, PPh3) were prepared according to literature
methods [37]. 3,30-Diselenopropionic acid, (HOOCCH2-
CH2Se)2 was prepared by reacting an aqueous Na2Se2
solution with 3-bromo propionic acid (1:2 mol) and
recrystallized from hot water, in 63% yield [38]. All reac-
tions were carried out under argon in dry and distilled
solvents.
3.4.2. [Pd2Cl2(l-SeCH2CH2COOMe)2(PnPr3)2] (2b)
Prepared similar to complex 2a from [Pd2Cl2(l-Cl)2-
(PnPr3)2] (559 mg, 0.83 mmol) and NaSeCH2CH2COOMe
[(MeOOCCH2CH2Se)2 (280 mg, 0.84 mmol) and NaBH4
(65 mg, 1.71 mmol)] and recrystallized from ethyl ace-
tate–hexane in 58% yield (450 mg); mp = 120–121 ꢀC.
Anal. Calc. for C26H56Cl2O4P2Pd2Se2: C, 33.4; H, 6.0.
Found: C, 33.9; H, 6.0%. IR (Nujol) m, cmꢀ1: 1734
(C@O); 316 (Pd–Cl). UV–Vis (CH2Cl2), k (e, Mꢀ1 cmꢀ1):
238 (2.4 · 104), 274 (1.7 · 104), 295 (1.5 · 104), 338 nm
(1.9 · 104). 1H NMR (CDCl3): 1.07 (t, 7 Hz, 18H,
PCH2CH2CH3); 1.56–1.68 (m, 12H, PCH2CH2); 1.81–
1.90 (m, 12H, PCH2–); 2.76 (q), 2.87 (cis/trans SeCH2–);
3.04 (t, 7 Hz, –CH2–); 3.18–3.23 (m, –CH2–); 3.63, 3.70
(each s, cis and trans isomer). 31P{1H} NMR (CDCl3):
12.9; 14.3 (s). 77Se{1H} NMR (CDCl3): ꢀ79.4 (s, trans
isomer); ꢀ58.8, ꢀ107.6 (cis isomer).
3.3. Preparation of the ligand (MeOOCCH2CH2Se)2 (1)
A methanolic solution (25 cm3) of (HOOCCH2CH2Se)2
(3.5 g, 11.5 mmol) containing 2 cm3 of conc. H2SO4 was
refluxed for 24 h. Excess methanol was distilled out and
the resulting contents were dissolved in ether (25 cm3).
Ether solution was repeatedly washed with three portions
(10 cm3) of water and dried over anhydrous sodium sulfate.
The solvent was stripped off by distillation and the residue
was distilled off under reduced pressure (2 mm) at 145 ꢀC as
a yellow-orange oil. Yield: 2.6 g (68%). Anal. Calc. for
C8H14O4Se2: C, 28.9; H, 4.2. Found: C, 29.3; H, 4.2%.
3.4.3. [Pd2Cl2(l-SeCH2CH2COOMe)2(PMePh2)2] (2c)
Prepared similar to complex 2a from [Pd2Cl2(l-Cl)2-
(PMePh2)2] (245 mg, 0.32 mmol) and NaSeCH2CH2-
COOMe [(MeOOCCH2CH2Se)2 (113 mg, 0.34 mmol) and
NaBH4 (26 mg, 0.68 mmol)] and recrystallized from
CHCl3–ether–hexane in 62% yield (203 mg); mp = 179–
180 ꢀC. Anal. Calc. for C34H40Cl2O4P2Pd2Se2: C, 40.2; H,
4.0. Found: C, 40.0; H, 3.8%. IR (Nujol) m, cmꢀ1: 1730
IR (Nujol) mC@O: 1734 cmꢀ1. UV–Vis (CH2Cl2), k (e,
1
M
ꢀ1 cmꢀ1): 235 (867), 307 (552) nm. H NMR (CDCl3):
2.81 (t, 7.2 Hz, 4H, SeCH2); 3.09 (t, 7.1 Hz, 4H,
SeCH2CH2); 3.69 (s, 6H, COOMe). 13C{1H} NMR
(CDCl3): 23.3 (COOMe); 35.7 (SeCH2); 51.6 (SeCH2CH2);
172.2 (CO). 77Se{1H} NMR (CDCl3): 325.4 ppm. Caution:
Skin contact should be avoided as it causes rashes/itching.
Wash with soap solution.
(C@O). UV–Vis (CH2Cl2),
k
(e,
M
ꢀ1 cmꢀ1): 235
(3.5 · 104), 275 (2.1 · 104), 353 (2.2 · 104) nm. H NMR
(CDCl3): 1.94 (t, 6.8 Hz); 2.11(d, 10.8 Hz, PMe); 2.20 (d,
10.6 Hz, PMe), 3.20 (t, 8 Hz) 3.44 (m, –CH2–), 3.60, 3.69
(each 1:1 cis isomer), 3.72 (trans isomer) (COOMe); 7.19–
7.35 [m, Ph]. 31P{1H} NMR (CDCl3): 8.6 (s, cis isomer);
10.6 (s, trans isomer).
1
3.4. Preparation of complexes
3.4.1. [Pd2Cl2(l-SeCH2CH2COOMe)2(PEt3)2] (2a)
A
dichloromethane solution (15 cm3) of [Pd2Cl2-
(l-Cl)2(PEt3)2] (247 mg, 0.42 mmol) was added to a

L.B. Kumbhare et al. / Journal of Organometallic Chemistry 692 (2007) 1546–1556
1553
3.4.4. [Pd2Cl2(l-SeCH2CH2COOMe)2(PPh3)2] (2d)
Prepared similar to complex 2a from [Pd2Cl2(l-Cl)2-
(PPh3)2] (249 mg, 0.28 mmol) and NaSeCH2CH2COOMe
[(MeOOCCH2CH2Se)2 (99 mg, 0.30 mmol) and NaBH4
(22 mg, 0.59 mmol)] and recrystallization by CHCl3–
ether–hexane in 59% yield (192 mg); mp = 160–161 ꢀC.
Anal. Calc. for C44H44Cl2O4P2Pd2Se2: C, 46.3; H, 3.9.
Found: C, 46.2; H, 3.9%. IR (Nujol) m, cmꢀ1: 1733
(C@O), 302 (Pd–Cl). UV–Vis (CH2Cl2), k (e, Mꢀ1 cmꢀ1):
235 (4.1 · 104), 308 (1.7 · 104), 361 (2.4 · 104) nm. 1H
NMR (CDCl3): 1.94 (t, 7 Hz); 2.14 (t, 7 Hz); 3.20 (t,
8 Hz), 3.48 (m) (–CH2–); 3.61 (s), 3.63 (s) (cis); 3.65 (s,
trans) (COOMe); 7.30–7.68 (m, Ph). 13C{1H} NMR
(CDCl3): 19.6, 22.6 (each s 1:1); 20.4 (br); 36.6, 38.0 (each
singlet 1:1); 51.6, 51.9 (each singlet 1:1); 51.8 (s), 128.1–
134.8 (complex pattern, Ph). 170.9, 171.9, 172.7 (each s,
CO). 31P{1H} NMR (CDCl3): 20.2 (s, cis); 23.1 (s, trans).
3090 Hz] (trans isomer). 77Se{1H} NMR (CDCl3): ꢀ106.5
[t, 1J(195Pt–77Se) = 177 Hz]; ꢀ128.1 [1J(195Pt–77Se)
= 242 Hz] (cis isomer); ꢀ241.0 [(d, J(195Pt–31P) = 144 Hz,
J(195Pt–77Se) = 132 Hz] (trans isomer). 195Pt{1H} NMR
2
(CDCl3): ꢀ3960 [d, 1J(195Pt–31P) = 3102 Hz, J(195Pt–195Pt)
= 986 Hz] (trans isomer); ꢀ4056 [d, 1J(195Pt–31P) =
2
3160 Hz, J(195Pt– 195Pt) = 922 Hz) (cis isomer).
3.4.7. [Pt2Cl2(l-SeCH2CH2COOMe)2(PnBu3)2] (2g)
Prepared similar to complex 2a from [Pt2Cl2(l-Cl)2-
(PnBu3)2] (145 mg, 0.16 mmol) and NaSeCH2CH2COOMe
[(MeOOCCH2CH2Se)2 (51 mg, 0.16 mmol) and NaBH4
(12 mg, 0.31 mmol)] and recrystallized from ethyl acetate–
hexane in 62% yield (115 mg); mp 110–112 ꢀC. Anal. Calc.
for C32H68Cl2O4P2Pt2Se2: C, 32.1; H, 5.7. Found: C, 32.5;
H, 5.7%. IR (Nujol) m, cmꢀ1: 1737 (C@O), 310 cmꢀ1 (Pt–
Cl). UV–Vis (CH2Cl2), k (e, Mꢀ1 cmꢀ1): 246 (2.3 · 104),
268 (2.3 · 104), 309 (8.6 · 103) nm. 1H NMR (CDCl3):
0.95 (t, 7 Hz, 18H, PCH2CH2CH2CH3); 1.44–1.55 (br, m,
24H, PCH2CH2CH2); 1.86 (br, 12H, PCH2); 2.81 (br,
SeCH2); 2.99 (br, SeCH2); 3.24 (br, –CH2–) 3.34 (br,
–CH2–); 3.63 (s, trans isomer), 3.69 (s, cis isomer) (COOMe).
31P{1H} NMR (CDCl3): ꢀ0.3 [1J(195Pt–31P) = 3133 Hz,
2J(77Se–31P) = 122 Hz] (cis isomer); 0.9 ppm [1J(195Pt–
31P) = 3105 Hz] (trans isomer). 77Se{1H} NMR (CDCl3):
ꢀ113.6 [1J(195Pt–77Se) = 183 Hz]; ꢀ139.9 [1J(195Pt–77Se) =
245 Hz] (cis isomer); ꢀ243.1 [d, J(77Se–31P) = 143 Hz,
J(195Pt–77Se) = 190 Hz] (trans isomer). 195Pt{1H} NMR
(CDCl3): ꢀ3964 (d, 1J(195Pt–31P) = 3111 Hz, trans isomer);
ꢀ4051 [d, 1J(195Pt–31P) = 3135 Hz, 2J(195Pt–195Pt) =
1007 Hz] (cis isomer).
3.4.5. [Pt2Cl2(l-SeCH2CH2COOMe)2(PEt3)2] (2e)
Prepared similar to complex 2a from [Pt2Cl2(l-Cl)2-
(PEt3)2] (210 mg, 0.27 mmol) and NaSeCH2CH2COOMe
[(MeOOCCH2CH2Se)2 (95 mg, 0.29 mmol) and NaBH4
(22 mg, 0.57 mmol)] and recrystallized from ethyl acetate–
hexane as yellow crystalline solid in 46% yield (128 mg);
mp = 123–125 ꢀC. Anal. Calc. for C20H44Cl2O4P2Pt2Se2:
C, 23.3; H, 4.3. Found: C, 23.6; H, 4.1%. IR (Nujol) m,
cmꢀ1: 1734 (C@O). UV–Vis (CH2Cl2), k (e, Mꢀ1 cmꢀ1):
1
248 (2.0 · 104), 266 (2.0 · 104), 311 (sh, 6.6 · 104) nm. H
NMR (CDCl3): 1.18 (m, 18H, PCH2CH3); 1.88 (m, 12H,
PCH2); 2.80 (SeCH2); 2.90 (SeCH2); 3.15 (t, 7 Hz, –CH2–)
3.40 (br, –CH2–); 3.64 (s, trans isomer, COOMe); 3.69 (s,
cis isomer, COOMe). 31P{1H} NMR (CDCl3): 7.8
[1J(195Pt–31P) = 3166 Hz (cis isomer)]; 8.6 [1J(195Pt–31P) =
3111 Hz (trans isomer)]. 77Se{1H} NMR (CDCl3): ꢀ104.2
[t, 1J(195Pt–77Se) = 168 Hz], ꢀ122.4 [t, 1J(195Pt–77Se) =
241 Hz] (cis isomer); ꢀ242.4 [d, (195Pt–77Se) = 143 Hz]
(trans isomer). 195Pt{1H} NMR (CDCl3): ꢀ3976 [(d,
3.4.8. [Pd2Cl2(l-Cl)(l-SeCH2CH2COOMe)(PEt3)2]
(3a)
A
dichloromethane solution (10 cm3) of [Pd2Cl2-
(l-Cl)2(PEt3)2] (59 mg, 0.10 mmol) was added to a solu-
tion (10 cm3) of [Pd2Cl2(l-SeCH2CH2COOMe)2(PEt3)2]
(85 mg, 0.10 mmol) in the same solvent. The resulting
light orange solution was stirred for 1 h. The solvent
was removed under vacuum to yield a yellow solid which
was recrystallized from CH2Cl2–hexane at ꢀ10 ꢀC as
deep yellow crystals (yield 123 mg, 86%); mp = 156–
157 ꢀC. Anal. Calc. for C16H37Cl3O2P2Pd2Se: C, 26.6;
2
1J(Pt–P) = 3110 Hz, J(195Pt–195Pt) = 1015 Hz)] (trans iso-
mer); ꢀ4073 [(d, 1J(195Pt–31P) = 3161 Hz, 2J(195Pt–195Pt) =
943 Hz)] (cis isomer).
3.4.6. [Pt2Cl2(l-SeCH2CH2COOMe)2(PnPr3)2] (2f)
Prepared similar to complex 2a from [Pt2Cl2(l-Cl)2-
(PnPr3)2] (170 mg, 0.20 mmol) and NaSeCH2CH2COOMe
[(MeOOCCH2CH2Se)2 (69 mg, 0.21 mmol) and NaBH4
(16 mg, 0.42 mmol)] and recrystallized from ethyl acetate–
hexane in 54% yield (120 mg); mp = 144–146 ꢀC. Anal.
Calc. for C26H56Cl2O4P2Pt2Se2: C, 28.0; H, 5.1. Found:
C, 28.3; H, 4.9%. IR (Nujol) m, cmꢀ1: 1732 (C@O), 312
(Pt–Cl). UV–Vis (CH2Cl2), k (e, Mꢀ1 cmꢀ1): 247 (2.7 ·
104), 267 (2.7 · 104), 309 (9.4 · 103) nm. 1H NMR (CDCl3):
1.07 (t, 7 Hz, 18H, PCH2CH2CH3); 1.61 (m, 12H,
PCH2CH2); 1.85 (m, 12H, PCH2); 2.78 (t, SeCH2); 2.92
(t, SeCH2); 3.15 (t, CH2) 3.40 (br, –CH2–); 3.64 (s, trans
isomer, COOMe); 3.70 (s, cis isomer, COOMe). 31P{1H}
NMR (CDCl3): ꢀ1.0 ppm [1J(195Pt–31P) = 3141 Hz,
2J(77Se–31P) = 122 Hz] (cis isomer); ꢀ0.1 [1J(195Pt–31P) =
H, 5.2. Found: C, 27.0; H, 5.1%. IR (Nujol) m, cmꢀ1
:
1731 (C@O), 322 (Pd–Cl). UV–Vis (CH2Cl2), k (e,
M
ꢀ1 cmꢀ1): 237 (2.7 · 104), 296 (2.0 · 104), 355 (6.1 ·
103) nm. H NMR (CDCl3): 1.22 (m, 18H, PCH2CH3);
2.02 (m, 12H, PCH2); 2.97 (t, 6.9 Hz, 2H, SeCH2); 3.38
(t, 6.6 Hz, 2H, SeCH2CH2); 3.73 (s, 3H, COOMe).
31P{1H} NMR (CDCl3): 41.1. 77Se{1H} NMR (CDCl3):
21.5 ppm.
1
3.4.9. [Pd2Cl2(l-Cl)(l-SeCH2CH2COOMe)(PnPr3)2]
(3b)
Prepared similar to complex 3a from [Pd2Cl2(l-Cl)2-
(PnPr3)2] (73 mg, 0.11 mmol) and [Pd2Cl2(l-SeCH2CH2-
COOMe)2(PnPr3)2] (100 mg, 0.1 mmol) and recrystallized

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L.B. Kumbhare et al. / Journal of Organometallic Chemistry 692 (2007) 1546–1556
1
from CH2Cl2–hexane (137 mg, 79% yield) as orange crys-
tals; mp = 175–176 ꢀC. Anal. Calc. for C22H49Cl3O2P2-
Pd2Se: C, 32.8; H, 6.1. Found: C, 32.5; H, 6.2%. IR (Nujol)
m, cmꢀ1: 1734 (C@O), 320 (Pd–Cl). UV–Vis (CH2Cl2), k (e,
(8.2 · 103), 344 (2.1 · 103) nm. H NMR (CDCl3): 1.07 (t,
6.9 Hz, 18H, PCH2CH2CH3); 1.65 (m, 12H, PCH2
CH2); 1.89 (m, 12H, PCH2); 2.94 (t, 2H, 6.9 Hz,
SeCH2), 3.25 (br, 2H, SeCH2CH2); 3.72 (s, 3H, COOMe).
31P{1H} NMR (CDCl3): 0.4 [1J(195Pt–31P) = 3912 Hz].
77Se{1H} NMR (CDCl3): ꢀ18.1 [1J(195Pt–77Se) = 134 Hz].
M
ꢀ1 cmꢀ1): 237 (2.7 · 104), 295 (2.0 · 103), 358 (6.2 · 103)
nm. 1H NMR (CDCl3): 1.09 (t, 7 Hz, 18H, PCH2CH2-
CH3); 1.69 (br, m, 12H, PCH2CH2); 1.93 (m, 12H,
PCH2); 2.95 (t, 6.6 Hz, 2H, SeCH2); 3.38 (t, 6.6 Hz, 2H,
SeCH2CH2); 3.73 (s, 3H, COOMe). 31P{1H} NMR
(CDCl3): 31.4. 77Se{1H} NMR (CDCl3): 16.4.
195Pt{1H} NMR (CDCl3): ꢀ3992 [d, J(195Pt–31P) = 3902
1
2
Hz, J(195Pt–195Pt) = 500 Hz].
3.4.13. [Pd2(SeCH2CH2COOMe)4(PnPr3)2] (4)
A dichloromethane solution (15 cm3) of [Pd2Cl2(l-
Cl)2(PnPr3)2] (185 mg, 0.27 mmol) was added to a methan-
olic solution (15 cm3) of NaSeCH2CH2COOMe [prepared
from (MeOOCCH2CH2Se)2 (192 mg, 0.58 mmol) and
NaBH4 (44 mg, 1.15 mmol)]. Reaction mixture was stirred
for 2 h under argon and the solvents were removed under
reduced pressure. Contents were extracted with dichorom-
ethane and extract was passed through a Florisil column.
Solvent was stripped off from the filtrate in vacuo where-
upon an oily residue was obtained. Repeated washing with
hexane and subsequent drying yielded a red oil of title com-
pound (230 mg, 74% Yield). Anal. Calc. for
C34H70O8P2Pd2Se4: C, 34.1; H, 5.9. Found: C, 34.6; H,
3.4.10. [Pd2Cl2(l-Cl)(l-SeCH2CH2COOMe)-
(PMe2Ph)2] (3c)
A
dichloromethane solution (15 cm3) of [Pd2Cl2-
(l-Cl)2(PMe2Ph)2] (217 mg, 0.34 mmol) was added to a
methanolic solution (10 cm3) of NaSeCH2CH2COOMe
[prepared from (SeCH2CH2COOMe)2 (57 mg, 0.17 mmol)
and NaBH4 (13 mg, 0.34 mmol)] and recrystallized from
CHCl3–ether (159 mg, 61% yield) as yellow crystals; mp
136–138 ꢀC. Anal. Calc. for C20H29Cl3O2P2Pd2Se: C,
31.5; H, 3.8. Found: C, 31.9; H, 3.7%. IR (Nujol) m,
cmꢀ1: 1721 (C@O), 314 (Pd–Cl). UV–Vis (CH2Cl2), k (e,
M
ꢀ1 cmꢀ1): 239 (2.1 · 104), 293 (2.2 · 104), 365 (7.5 · 104)
1
nm. H NMR (CDCl3): 1.90, 1.98 (each d, J(P–H) 12 Hz,
PMe2); 2.58 (t, 6.9 Hz, 2H, SeCH2); 2.78 (t, 6.6 Hz, 2H,
SeCH2CH2), 3.66 (s, 3H, COOMe); 7.45, 7.61–7.66 (m)
[Ph]. 31P{1H} NMR (CDCl3): 10.3. 77Se{1H} NMR
(CDCl3): 56.3 ppm.
5.8%. IR (Nujol) mC@O: 1740 cmꢀ1 1H NMR (CDCl3):
.
1.04 (t, 18H, PCH2CH2CH3); 1.55 (br, 12H, PCH2CH2);
1.87 (br, PCH2); 2.73–2.95 (m, 16H, SeCH2CH2); 3.38
(s); 3.66 (s) (COOMe). 31P{1H} NMR (CDCl3): 7.7; 8.6.
77Se{1H} NMR (CDCl3): ꢀ271.1; 93.7; 97.7; 141.5 (each s).
3.4.11. [Pt2Cl2(l-Cl)(l-SeCH2CH2COOMe)(PEt3)2] (3d)
Prepared similar to complex 3a from [Pt2Cl2-
(l-SeCH2- CH2COOMe)2(PEt3)2] (86 mg, 0.08 mmol) and
[Pt2Cl2(l-Cl)2(PEt3)2] (64 mg, 0.08 mmol) in CH2Cl2 and
recrystallized from CH2Cl2–hexane at ꢀ10 ꢀC as yellow
crystals (117 mg, 78% yield); mp = 187–189 ꢀC. Anal. Calc.
for C16H37Cl3O2P2Pt2Se: C, 21.4; H, 4.1. Found: C, 21.7;
H, 4.1%. IR (Nujol) m, cmꢀ1: 1741 (C@O), 315 (Pt–Cl).
UV–Vis (CH2Cl2), k (e, Mꢀ1 cmꢀ1): 246 (2.1 · 104), 280
(6.7 · 103), 332 (1.5 · 103) nm. 1H NMR (CDCl3): 1.16
(m, 18H, PCH2CH3); 1.90–2.10 (m, 12H, PCH2); 2.99 (t,
7 Hz, 2H, SeCH2); 3.25 (t, br, 6.9 Hz, 2H, SeCH2CH2);
3.73 (s, 3H, COOMe). 31P{1H} NMR (CDCl3): 9.3
[1J(195Pt–31P) = 3936 Hz, 2J(195Pt–195Pt) = 432 Hz]. 77Se
{1H} NMR (CDCl3): ꢀ15.3 [1J(195Pt–77Se) = 147 Hz].
195Pt{1H} NMR (CDCl3): ꢀ4017 [d, 1J (195Pt–31P) =
3.4.14. [Pd3Cl2(l-SeCH2CH2COOMe)4(PnPr3)2] (5)
The complex 2b, when left for recrystallization gave two
types of crystals viz. yellow orange (2a), and deep red (5).
The latter was mechanically separated. A dichloromethane
solution (15 cm3) of [Pd2Cl2(l-Cl)2(PnPr3)2] (189 mg,
0.28 mmol) was added to a methanolic solution (10 cm3)
of NaSeCH2CH2COOMe [prepared from (MeOOCCH2-
CH2Se)2 (126 mg, 0.38 mmol) and NaBH4 (29 mg,
0.76 mmol)]. Reaction mixture was stirred under argon
for 2 h to obtain a red solution. The solvents were evapo-
rated under vacuum and the residue was extracted with
dichloromethane (20 cm3). Extract was passed through a
Florisil column (0.5 cm · 7 cm) and dried to get a red oil
which was dissolved in CH2Cl2–ethyl acetate–hexane mix-
ture and cooled at ꢀ10 ꢀC yield red crystals of the title
compound (103 mg, 68% yield); mp = 124–125 ꢀC. Anal.
Calc. for C34H70Cl2O8P2Pd3Se4: C, 29.7; H, 5.1. Found:
C, 30.2; H, 5.1%. IR (Nujol) mC@O: 1732 cmꢀ1. UV–Vis
2
3922 Hz, J(195Pt–195Pt) = 446 Hz].
3.4.12. [Pt2Cl2(l-Cl)(l-SeCH2CH2COOMe)(PnPr3)2]
(3e)
(CH2Cl2),
k
(e,
M
ꢀ1 cmꢀ1): 236 (3.1 · 104), 259
(2.7 · 104), 291 (2.8 · 104), 342 (2.6 · 104), 372 (sh,
2.4 · 104). 1H NMR (CDCl3): 1.06 (t, 18H, PCH2-
CH2CH3); 1.60 (br, 12H, PCH2CH2); 1.86 (br, 12H,
PCH2); 2.76, 2.78 (each m); 3.06 (m), 3.22 (br); 3.62, 3.69
(each s, COOMe). 31P{1H} NMR (CDCl3): 13.0 (s).
Prepared similar to complex 3a using [Pt2Cl2(l-Cl)2-
(PnPr3)2] (65 mg, 0.076 mmol) and [Pt2Cl2(l-SeCH2CH2-
COOMe)2(PnPr3)2] (85 mg, 0.076 mmol) and recrystallized
from CH2Cl2–hexane as yellow crystals (121 mg, 81%
yield); mp = 177–179 ꢀC. Anal. Calc. for C22H49Cl3O2P2-
Pt2Se: C, 26.9; H, 5.0. Found: C, 27.1; H, 4.9%. IR (Nujol)
m, cmꢀ1: 1737 (C@O), 315 (Pt–Cl). UV–Vis (CH2Cl2), k (e,
3.4.15. [Pd(SeCH2CH2COOMe)2]6 (6)
A methanolic solution (15 cm3) of Na2PdCl4 (307 mg,
1.04 mmol) was added to a solution (10 cm3) of NaSe-
M
ꢀ1 cmꢀ1): 238 (2.4 · 104), 246 (2.5 · 104), 280

L.B. Kumbhare et al. / Journal of Organometallic Chemistry 692 (2007) 1546–1556
1555
CH2CH2COOMe [prepared from (MeOOCCH2CH2Se)2
(350 mg, 1.05 mmol) and NaBH4 (82 mg, 2.2 mmol)].
Reaction mixture was stirred for 2 h under argon and the
solvent was dried under vacuum. Residue was extracted
with dichloromethane which was evaporated in vacuo to
yield a deep red powder. Recrystallisation from dichloro-
methane–hexane–ethyl acetate gave deep red crystals
(228 mg, 50% yield); mp = 140–141 ꢀC. Anal. Calc. for
[C8H14O4PdSe2]6: C, 21.9; H, 3.2. Found: C, 22.3; H,
3.2%. IR (Nujol) mC@O: 1732 cmꢀ1. UV–Vis (CH2Cl2), k
CH2COOMe)2(PPh3)2], [Pt2Cl2(l-Cl)(l-SeCH2CH2COO-
Me)(PnPr3)2], [Pd3Cl2(l-SeCH2CH2COOMe)4(PnPr3)2] and
[Pd(l-SeCH2CH2COOMe)2]6. These data can be obtained
free of charge via http://www.ccdc.cam.ac.uk/conts/
retrieving.html, or from the Cambridge Crystallographic
Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK;
fax: (+44) 1223-336-033; e-mail: deposit@ccdc.cam.ac.uk.
Supplementary data associated with this article can be
found, in the online version, at doi:10.1016/j.jorganchem.
2006.12.003.
(e,
M
ꢀ1 cmꢀ1): 235 (4.5 · 104), 257 (4.7 · 104), 279
(5.4 · 104), 297 (6.5 · 104), 331(5.0 · 104), 439 (2.7 · 104)
nm. 1H NMR (CDCl3): 2.65–2.79 (m), 2.92 (t, 7 Hz)
(SeCH2CH2); 3.68, 3.72 (each s, OMe). 13C NMR (CDCl3):
17.7, 20.6 (each s, SeCH2); 36.5, 38.9 (each s, CH2); 51.5,
51.7 (each s, OMe); 171.6 (s, CO). 77Se{1H} NMR
(CDCl3): ꢀ33.0; ꢀ172 (each s).
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