Synthesis and characterization of benzylselenolate complexes of palladium(II) and platinum(II)

Article abstract of DOI:10.1016/S0022-328X(00)00525-8

Reactions of sodium benzylselenolate with several palladium(II) and platinum(II) complexes were carried out and a variety of products isolated and characterized. Reactions of Na₂PdCl₄ or K₂PtCl₄ with NaSeBz gave [M(SeBz)₂]_n (M=Pd or Pt; Bz=CH₂Ph) which when treated with tertiary phosphines yielded [M(SeBz)₂(L-L)]. The latter can also be prepared by the reaction of MCl₂(L-L) (L-L=dppm, dppe or 2PPh₃) with NaSeBz. Treatment of [M₂X₂(μ-Cl)₂(PR₃)₂] with NaSeBz in 1:2 molar ratio afforded complexes of the type [M₂X₂(μ-SeBz)₂(PR₃)₂] (M=Pd or Pt; X=Cl or Me; PR₃=PEt₃, PPrⁿ₃, PBuⁿ₃, PMe₂Ph, PMePh₂ or PPh₃) which existed predominantly as a cis isomer. Reaction of [M₂Cl₂(μ-Cl)₂(PR₃)₂] with [M₂Cl₂(μ-SeBz)₂(PR₃)₂] gave heterobridged complexes [M₂Cl₂(μ-Cl)(μ-SeBz)(PR₃)₂], the bridging chloride in the latter can be substituted with SBu^t or pz. All the complexes were characterized by elemental analysis and NMR (¹H, ³¹P, ⁷⁷Se, ¹⁹⁵Pt) spectral data. Stereochemistry of these complexes has been discussed on the basis of NMR data. The crystal structure of [Pt₂Cl₂(μ-SeBz)₂(PPrⁿ₃)₂] has established a cis configuration with a bent four-membered Pt₂Se₂ ring. The complex [Pd(SeBz)₂]_n on thermolysis at 630°C yields Pd₁₇Se₁₅.

Full text of DOI:10.1016/S0022-328X(00)00525-8

Journal of Organometallic Chemistry 623 (2001) 48–55
www.elsevier.nl/locate/jorganchem
Synthesis and characterization of benzylselenolate complexes of
palladium(II) and platinum(II)
Sandip Dey a, Vimal K. Jain a,*, Babu Varghese b
a No6el Materials and Structural Chemistry Di6ision, Bhabha Atomic Research Centre, Mumbai 400085, India
b Regional Sophisticated Instrumentation Centre, Indian Institute of Technology, Chennai 600036, India
Received 9 May 2000; accepted 24 May 2000
Abstract
Reactions of sodium benzylselenolate with several palladium(II) and platinum(II) complexes were carried out and a variety of
products isolated and characterized. Reactions of Na2PdCl4 or K2PtCl4 with NaSeBz gave [M(SeBz)2]n (M=Pd or Pt;
Bz=CH2Ph) which when treated with tertiary phosphines yielded [M(SeBz)2(L-L)]. The latter can also be prepared by the
reaction of MCl2(L-L) (L-L=dppm, dppe or 2PPh3) with NaSeBz. Treatment of [M2X2(m-Cl)2(PR3)2] with NaSeBz in 1:2 molar
ratio afforded complexes of the type [M2X2(m-SeBz)2(PR3)2] (M=Pd or Pt; X=Cl or Me; PR3=PEt3, PPrn3, PBu3n, PMe2Ph,
PMePh2 or PPh3) which existed predominantly as a cis isomer. Reaction of [M2Cl2(m-Cl)2(PR3)2] with [M2Cl2(m-SeBz)2(PR3)2] gave
heterobridged complexes [M2Cl2(m-Cl)(m-SeBz)(PR3)2], the bridging chloride in the latter can be substituted with SBut or pz. All
the complexes were characterized by elemental analysis and NMR (1H, 31P, 77Se, 195Pt) spectral data. Stereochemistry of these
complexes has been discussed on the basis of NMR data. The crystal structure of [Pt2Cl2(m-SeBz)2(PPrn3)2] has established a cis
configuration with a bent four-membered Pt2Se2 ring. The complex [Pd(SeBz)2]n on thermolysis at 630°C yields Pd17Se15. © 2001
Elsevier Science B.V. All rights reserved.
Keywords: Palladium; Platinum; Benzylselenolate; NMR; Binuclear compounds; Tertiaryphosphines
1. Introduction
chalcogens (E=Se or Te) are rare [8]. We have recently
examined some chemistry of palladium and platinum
complexes with SeEt [9], SePh [10], Sepy [11], and TePh
[12] ligands. The increasing continued interest in sele-
nium/tellurium containing materials [2c,8b] and a drive
to replace volatile toxic Se/Te containing precursors
(such as H2Se or R2E2 etc.) have motivated us to
explore single source precursors. The photosensitivity
and cleaner cleavage of the benzyl group in Bz2E2
(E=Se or Te) [13] has attracted our attention to exam-
ine the chemistry of palladium(II) and platinum(II)
with the BzSe− ligand. Results of this work are re-
ported herein.
The chemistry of transition metal complexes with
chalcogen ligands is expanding at a rapid pace. Besides
diverse structural possibilities [1], they have been used
as molecular precursors for the preparation of ad-
vanced materials [2] and industrial catalysis [3]. Plat-
inum group chalcogenides MxEy (M=platinum group
metal; E=S, Se, Te) find extensive applications in
catalysis [4] and materials science [5]. We have recently
demonstrated that the methylallyl palladium complexes
[Pd2(m-ER)2(h3-C4H7)2] on thermolysis yield Pd4E (E=
S or Se)/Pd3Te2 at moderately low temperatures
(140°C) [6]. Similarly [Pd(Epy){S2P(OR)2}(PPh3)] af-
fords PdSE (E=S, Se) on pyrolysis [7].
The chemistry of palladium and platinum with
chalcogenolates has been dominated by molecules con-
taining thiolate groups [1]. Complexes with heavier
2. Results and discussion
2.1. Mononuclear complexes
* Corresponding author. Tel.: +91-22-550-5148; fax: +91-22-550-
5151.
Reaction of Na2PdCl4/K2PtCl4 with sodium ben-
E-mail address: jainvk@apsara.barc.ernet.in (V.K. Jain).
zylselenolate, prepared by reductive cleavage of the
0022-328X/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(00)00525-8

S. Dey et al. / Journal of Organometallic Chemistry 623 (2001) 48–55
49
Se–Se bond in Bz2Se2 with sodium borohydride in
methanol, afforded sparingly soluble complexes of com-
position [M(SeBz)2] (1) [M=Pd (1a) or Pt (1b)]. Several
thiolates of composition [M(SR)2] are reported as poly-
meric species; structures of palladium complexes
[Pd(SPrn)2]n (n=6 or 8) [14] have been confirmed by
X-ray diffraction. Treatment of 1 with phosphine lig-
ands readily gave monomeric complexes [M(SeBz)2(L-
L)] (2) (M=Pt; L-L=2PPh3) and (3) (Scheme 1). The
latter two can be obtained readily by the reaction of
MCl2(L-L) with NaSeBz.
2377 Hz) and −4917 (1J(195Pt–31P)=2853 Hz) ppm,
respectively, due to coupling with two equivalent phos-
phorus nuclei. 195Pt-NMR data can be compared with
the spectra of cis-[Pt(ER)2(L-L)] (E=S, Se, Te; L=
dppm or dppe) [15b]. The 195Pt resonance is shielded on
substituting dppm for dppe, though the overall stereo-
chemistry is same in the two complexes. The observed
shielding may be attributed to the ring size effects.
2.2. Binuclear complexes
The compound 2 has been isolated as a cis product.
Treatment of [M2X2(m-Cl)2(PR3)2] with NaSeBz af-
forded benzylselenolato-bridged complexes, [M2X2(m-
SeBz)2(PR3)2] (4) as orange (Pd) or yellow (Pt)
crystalline solids (Scheme 2). The reaction of halogen-
bridged complexes [M2Cl2(m-Cl)2(PR3)2] with [M2Cl2(m-
SeBz)2(PR3)2] in refluxing dichloromethane yields
heterobridged complexes [M2Cl2(m-Cl)(m-SeBz)(PR3)2]
(5) in quantitave yields. The bridging chloride in the
latter can be substituted with pyrazolato ligand, by
treatment with pyrazole in the presence of aqueous
NaOH to yield [M2Cl2(m-pz)(m-SeBz)(PR3)2] (6) or SBut
by the reaction of ButSH to give [M2Cl2(m-SBut)(m-
SeBz)(PR3)2] (7).
4
The presence of J(P–H) for the methylene protons of
1
the SeBz group and the magnitude of J(Pt–P) (2964
1
Hz) indicates a cis geometry. The magnitude of J(Pt–
P) (Table 1) can be compared with cis-[Pt(-
SePh)2(PPh3)] (2969 Hz) while the trans isomer has a
1
smaller J(Pt–P) (2860 Hz) [15]. 2 reacts with methyl
iodide in benzene to yield a pale yellow solid which is
characterized as trans-[PtI2(PPh3)2] from analysis and
NMR data.
The 31P{1H}-NMR resonances for 3 are deshielded
relative to the corresponding cis-MCl2(L-L) species and
1
the magnitude of J(Pt–P) is reduced significantly indi-
cating strong trans influence of the SeBz group trans to
The NMR spectra of these complexes (4–7) are
consistent with the [Pt2X2(m-Y)(m-SeBz)(PR3)2] arrange-
ment which exhibits trans (A) and cis (B and C) iso-
merism as depicted below:
1
phosphines. The H-NMR spectra exhibited a doublet
4
for the CH2 protons of the SeBz group due to J(P–H)
couplings (ꢀ3 Hz). The 195Pt{1H}-NMR spectra of 3b
and 3c displayed a triplet at l −4205 (1J(195Pt–31P)=
The NMR spectra of 4 revealed that these complexes
were formed exclusively as the cis isomer except in a
few cases where a small quantity of trans isomer also
formed. The 1H-NMR spectra for the cis complexes
exhibited two sets of methylene proton resonances of
SeBz groups each flanked by 77Se satellites (2J(77Se–
1H)ꢀ10 Hz). The downfield signal, appearing as a
triplet due to phosphorus coupling, has been attributed
to the SeBz group trans to the phosphine ligand. The
high field signal, appearing as a singlet, has been as-
signed to the SeBz group trans to the terminal chloride
ligand. The methylene proton resonances of the benzyl
group for platinum complexes were further flanked by
195Pt satellites. The trans isomer, as expected, showed
only one methylene proton resonance.
The 31P{1H}-NMR spectra (Table 1) displayed a
single set of resonances for cis and trans isomers, the
signal for the latter is considerably deshielded com-
Scheme 1.

50
S. Dey et al. / Journal of Organometallic Chemistry 623 (2000) 48–55
Table 1
31P- and 1H-NMR data for benzylselenolate complexes of palladium and platinum
Complex 31P-NMR data
31P (ppm)
1H-NMR data
l
1H (ppm)
l
1J(Pt–P) (Hz)
Other couplings (Hz)
2
3a
17.9
49.8
2964
4.46 (d, J(P–H)=4.3 Hz; J(Pt–H)=36.5 Hz, SeCH2); 7.04–7.52 (m, Ph)
2.23 (d, 21.4 Hz, PCH2); 3.87 (d, J(P–H)=3.5 Hz, SeCH2); 7.01–7.17
(m), 7.36–7.51 (m), 7.70–7.82 (m) Ph
3b
3c
4a
−51.8
2389
2842
2J(Se–P)=29
2J(Se–P)=62.6
2J(Se–P)=64
2J(Se–P)=65
2J(Se–P)=64
2J(77Se–31P)=57;
3.74 (s, J(Pt–H)=18.6 Hz, SeCH2); 4.40 (t, J(P–H)=10.4 Hz, J(Pt–
H)=45 Hz, PCH2); 7.01–7.17 (m), 7.42–7.52 (m), 7.88–7.94 (m) Ph
2.17 (d, 18.9 Hz, PCH2); 3.83 (d, J(P–H)=3 Hz, J(Pt–H)=25 Hz,
SeCH2); 7.01–7.24 (m); 7.30–7.48 (m); 7.70–7.91 (m) Ph
1.03 (t, 7.1 Hz, PCH2CH2CH3); 1.44–1.55 (m, PCH2CH2–); 1.69–1.79
(m, PCH2–); 3.80 (s, J(Se–H)=12 Hz), SeCH2 trans to Cl); 4.51 (t, 4.7
Hz, SeCH2 trans to P); 4.40 (s, SeCH2 J(Se–H)=11 Hz trans isomer);
7.15–7.65 (m, Ph) for cis and trans isomers
0.94 (t, 6.9 Hz, PCH2CH2CH2CH3); 1.43 (br, PCH2CH2CH2–);
1.71–1.81 (m, PCH2–); 3.80 (s, SeCH2 trans to Cl); 4.50 (t,
4J(P–H)=4.6 Hz, SeCH2 trans to P); 7.15 (t, 7.4 Hz, 4H, C6H5); 7.40
(d, 7.4 Hz, C6H5); 7.65 (d, 7.1 Hz, 2H C6H5); 7.23–7.31(m, Ph)
1.50 (d), 1.64 (d) (each 11 Hz, PMe2, major cis isomer), 1.59 (d), 1.77
(d) (each 12.4 Hz, PMe2, trans isomer); 3.38 (s, 2J(Se–H)=10 Hz,
SeCH2 trans to Cl); 4.54 (t, 4J(P–H)=5.1 Hz, SeCH2 trans to P) [cis
isomer]; 3.90 (s, SeCH2, trans isomer, 10%);7.14–7.47 (m); 7.64 (d), (Ph)
3.23 (s, trans to Cl, SeCH2); 4.83 (t, 4J(P–H)=4.9 Hz, SeCH2 trans to
PPh3,); 6.84–7.76 (m, Ph)
47.0
(cis) 13.8; (trans)
31.2
4b
14.1
4c a
(cis) −3.8; (trans)
10.1
4d
4e
4f
21.2
33.1
7.5
0.46 (d, J(P–H)=3.3 Hz,, Pd–Me); 3.13–3.83 (br, SeCH2); 7.01–7.13
(m); 7.32–7.41 (m); 7.60–7.74 (m) (Ph)
1.07 (td, 16.7 Hz, d; 7.6 Hz, t; PCH2CH3); 1.60–1.94 (m, PCH2); 3.93
3219
3194
2J(195Pt–195Pt)=846 (s, 3J(Pt–H)=41 Hz; 2J(Se–H)=11 Hz; SeCH2 trans to Cl); 4.64 (t,
4J(P–H)=3.7 Hz; 3J(Pt–H)=21 Hz; SeCH2 trans to PEt3); 7.14 (t, 7.3
Hz, 4H, C6H5); 7.41–7.44 (m, 3H, C6H5); 7.60 (d, 7.3 Hz, 2H, C6H5)}
(Ph, SeBz trans to P); 7.23–7.31 (m) (Ph, SeBz cis to P)
4g
−0.8
2J(77Se–31P)=57;
1.02 (t, 7 Hz, PCH2CH2CH3); 1.42–1.58 (m, PCH2CH2–); 1.61–1.86
2J(195Pt–195Pt)=860 (m, PCH2–); 3.91 (s, 2J(Se–H)=10 Hz), 3J(Pt–H)=41 Hz; SeCH2
trans to Cl); 4.63 (t, 4J(P–H)=3.7 Hz, 3J(Pt–H)=21 Hz, SeCH2 trans
to P); 7.13 (t, 6.2 Hz, 4H, C6H5); 7.40 (m, 3H, C6H5); 7.60 (d, 7.6 Hz,
2H, C6H5)} (Ph, SeBz trans to P); 7.25–7.30 (m) (Ph, SeBz cis to P)
4h
4i
−1.3
3323
3823
2J(77Se–31P)=60
2.03 (d, J(P–H)=11 Hz; 3J(Pt–H)=30 Hz, PMe); 3.19 (s,
3J(Pt–H)=40 Hz, SeCH2, trans to Cl); 4.78 (t, 4J(P–H)=4 Hz,
3J(Pt–H)=23 Hz; SeCH2, trans to P); 6.90–7.68 (m, Ph)
0.70 (d, 3J(P–H)=4.4 Hz; 2J(Pt–H)=73 Hz; PtMe); 1.59 (d,
2J(P–H)=10 Hz; 3J(Pt–H)=41 Hz, PMe2); 3.69 (s, 3J(Pt–H)=15 Hz,
SeCH2, trans to PtMe); 4.15 (t, 4J(P–H)=3.4 Hz, 3J(Pt–H)=26 Hz;
SeCH2, trans to P); 7.04–7.47 (m), 7.65–7.71 (m) (Ph)
−13.2
5a
5b
31.2
0.1
1.03 (t, 7.1 Hz, PCH2CH2Me); 1.47–1.59 (m, PCH2CH2–); 1.69–1.84
(m, PCH2–); 4.39 (s, SeCH2 cis to P); 7.29–7.34 (m, 3, 4, 5H, Ph); 7.54
(d, 7.2 Hz, 2, 6H, Ph)
3950
4192
1.03 (t, 7.2 Hz, PCH2CH2Me); 1.48–1.59 (m, PCH2CH2–); 1.62–1.87
(m, PCH2–); 4.36 (s, 3J(Pt–H) 38 Hz); 7.29–7.34 (m, 3, 5H, Ph),
7.51–7.55(m, 2, 6H, Ph)
5c
6a
−4.4
2.06 (d, 2J(P–H)=12 Hz; 3J(Pt–H)=39 Hz, PMe); 3.62 (s,
3J(Pt–H)=32 Hz, SeCH2 trans to Cl); 7.00–7.60 (m, Ph)
1.03 (t, 7.2 Hz, PCH2CH2Me); 1.42–1.59 (m, PCH2CH2–); 1.71–1.87
(m, PCH2–); 3.50 (s, SeCH2 trans to Cl); 6.18 (t, 1.9 Hz, 3H, pz trans
to P); 7.25–7.35 (m, Ph); 8.01 (s, br, 2,4H, pz)
18.3
6b
7
−8.6
3170
3J(Pt–P)=39
1.02 (t, 7.1 Hz, PCH2CH2Me); 1.40–1.49 (m, PCH2CH2); 1.74–1.83
(m, PCH2); 3.43 (s, 3J(Pt–H)=40 Hz, SeCH2); 6.29 (s, br, 3H, pz);
7.24–7.33 (m, Ph); 8.11 (s, 2-,4H, pz)
1.09 (m, PCH2CH2Me); 1.42–1.53 (m, PCH2CH2); 1.57–1.75 (m,
PCH2); 1.80 (s, SBut); 4.11 (s, 2J(Se–H)=10 Hz, 3J(Pt–H)=42 Hz,
SeBz trans to Cl); 4.63 (t, 4J(P–H)=3.7 Hz, SeBz trans to P); 7.15 (t,
4H); 7.45–7.48 (m, 3H); 7.60 (d, 6.9 Hz, 2H; Ph for SeBz trans to P);
7.25–7.39 (m, Ph for SeBz trans to Cl)
−2.2 b; −0.8 c
3102; 3190
a cis:trans ratio 9:1.
b Phosphine trans to bridging SBut; major isomer.
c Phosphine trans to bridging SeBz; minor isomer (by integration of 31P-NMR spectrum).

S. Dey et al. / Journal of Organometallic Chemistry 623 (2001) 48–55
51
phosphorus nuclei. The magnitude of 2J(195Pt–195Pt)
couplings can be compared with bis(organochalcogeno-
lato)-bridged complexes, [Pt2Cl2(m-ER)2(PR3)2] [10,18].
The 77Se{1H}-NMR spectra of 4b [l 38.8 (cis to P),
pared with that for the former. These signals were
2
flanked by the 77Se isotope with J(Se–P)ꢀ60 Hz. The
1
spectra of platinum complexes displayed J(Pt–P) cou-
plings which can be compared with the couplings re-
ported for organochalcogenolate bridged complexes
[Pt2Cl2(m-ER)2(PR3)2] (E=S, Se, Te) [9,10,16,17].
1
29.1 (trans to P)] and 4g [l 11.8, J(195Pt–77Se)=134
1
2
Hz (cis to P); −25.3, J(195Pt–77Se)=229 Hz, J(77Se–
31P)=39 Hz (trans to P)] exhibited two signals at-
tributable to bridging SeBz groups, each trans to
chloride and phosphine ligands. The 77Se-NMR spectra
of 4g (Fig. 1) showed couplings due to 195Pt and 31P
nuclei. The BzSe group trans to phosphine exhibited
phosphorus couplings (2J(77Se–31P)=39 Hz) while for
the BzSe trans to chloride such couplings are not
resolved as the 2J(Se–P)cis are B10 Hz [15b]. The
magnitude of J(195Pt–77Se) for BzSe trans to P is
greater than that of the trans to Cl. The compound 7
also existed in two cis configurations (B and C; Y=
SBut, Cl), thus the 31P-NMR spectra displayed two
signals, and the isomer with the phosphines trans to
SBut predominated.
1
The 195Pt-NMR spectra of 4g (l −4072, J(195Pt–
2
31P) 3200 Hz, J(195Pt–195Pt)=841 Hz) and 4h (l −
1
2
4107, J(195Pt–31P) 3310 Hz, J(195Pt–195Pt)=929 Hz)
displayed the expected doublet due to coupling with
On the basis of NMR data 5 and 6 have been
assigned a cis configuration with phosphine ligands
trans to bridging Y (Y=Cl or pz) (C). Accordingly the
1
methylene proton signal of SeBz in the H-NMR spec-
tra did not show 4J(P–H) couplings. The 31P-NMR
1
spectra of 5b and 5c showed considerably large J(Pt–
P) couplings. 195Pt and 77Se-NMR spectra of 5b were
recorded in CDCl3. The 195Pt-NMR spectrum exhibited
1
the expected doublet at l −3986 with J(195Pt–31P)=
3955 Hz. The 77Se-NMR spectrum showed a triplet at l
1
69.2 with J(195Pt–77Se)=113 Hz. The magnitude of
2J(Se–P) appears to be small which further suggests
that phosphine is cis to the bridging SeBz group. Re-
cently we have reported a series of organochalcogeno-
lato-bridged complexes of type 5 and 6 for which a cis
configuration (C) has been established by X-ray diffrac-
tion data [16,19–22].
2.3. Structure of [Pt2Cl2(v-SeBz)2(PPrn3)2] (4g)
Scheme 2.
The crystal and molecular structure of [Pt2Cl2(m-
SeBz)2(PPrn3)2] (4g) together with atomic numbering
scheme is shown in Fig. 2. Selected bond lengths and
angles are summarized in Table 2. The molecule con-
sists of two slightly distorted square planar platinum
atoms which are bridged together by two benzylseleno-
lato groups. The platinum atoms Pt(1) and Pt(2)
,
showed deviation of 0.046 and 0.032 A, respectively,
from the mean planes defined by P(1)Cl(1)Se(1)Se(2)
and P(2)Cl(2)Se(1)Se(2). The molecule has a sym-cis
configuration with
‘Pt2Se2’ ring (hinge angle 131.1°). This is in contrast to
the ethylselenato-bridged complex [Pt2Cl2(m-
a
non-planar four-membered
SeEt)2(PEt3)2] which has a planar Pt2Se2 ring [9].
Alkylthiolato-bridged palladium and platinum com-
plexes adopt a non-planar conformation for the four-
Fig. 1. 77Se{1H}-NMR spectrum of 4g in CDCl3.

52
S. Dey et al. / Journal of Organometallic Chemistry 623 (2001) 48–55
are significantly smaller than those observed in
[Pt2Cl2(m-SeEt)2(PEt3)2] [9] (96.9°), but can be com-
pared with the alkylthiolato bridged complex [Pt2Cl2(m-
SEt)2(PR3)2] [85.1(2), 89.7(2)°] [24]. The benzyl groups
adopt an anti configuration.
2.4. Thermal studies
In order to evaluate whether the benzylselenolate
complexes reported here can serve as precursors for the
synthesis of palladium selenides, thermolysis of one
representative complex, [Pd(SeBz)2]n (1a) was studied.
The thermogravimetric analysis (TGA) (Fig. 3) of 1a
was carried out in a flowing argon atmosphere. The TG
trace (Fig. 3) shows two stages of decomposition. The
product formed after the first stage of decomposition
(in the temperature range 210–500°C) was identified as
a mixture of PdSe2 and Pd17Se15 contaminated with
carbon (typical analysis of a sample heated at 300°C: C,
7.7; H, 0.6; Se, 49.1; Pd, 40.4%, XRD pattern showed
peaks due to PdSe2 and Pd17Se15). In the second stage
of decomposition (above 600°C) selenium is eleminated
leading to the formation of Pd17Se15 as indicated by the
weight loss and XRD pattern which compares well with
the reported pattern (JCPDS-ICDD 29-1437; 11-508).
The carbon contents (C 5.7%) in this product were
reduced slightly.
Fig. 2. Molecular structure with atomic numbering scheme of
[Pt2Cl2(m-SeBz)2(PPrn3)2] (4g).
Table 2
n
,
Selected bond lengths(A) and angles(°) for [Pt2Cl2(m-SeBz)2(PPr3)2]
(4g)
Pt(1)–P(1)
Pt(1)–Cl(1)
Pt(1)–Se(1)
Pt(1)–Se(2)
Se(1)–C(1)
2.253(3)
2.338(2)
2.3885(10)
2.4829(13)
2.015(10)
Pt(2)–P(2)
Pt(2)–Cl(2)
Pt(2)–Se(1)
Pt(2)–Se(2)
Se(2)–C(8)
2.257(3)
2.345(3)
2.3874(12)
2.4734(11)
1.979(10)
3. Experimental details
The complexes [MCl2(L-L)] [30,31], [M2Cl2(m-
Cl)2(PR3)2] [32] (M=Pd or Pt; L-L=dppm, dppe,
2PPh3; PR3=PEt3, PPrn3, PBu3n, PMe2Ph; PMePh2 or
PPh3), [M2Me2(m-Cl)2(PR3)2] [33,34] and Bz2Se2 (Bz=
PhCH2–) were prepared according to literature meth-
ods. Due to slow photodecomposition of Bz2Se2, it was
recrystallized every month from petroleum ether, m.p.
Pt(1)–Se(1)–Pt(2)
P(1)–Pt(1)–Cl(1)
P(1)–Pt(1)–Se(1)
Cl(1)–Pt(1)–Se(1)
P(1)–Pt(1)–Se(2)
Cl(1)–Pt(1)–Se(2)
Se(1)–Pt(1)–Se(2)
Se(1)–C(1)–C(2)
89.99(4)
89.19(10)
96.09(7)
174.72(8)
175.26(8)
93.88(8)
80.88(4)
112.2(8)
Pt(1)–Se(2)–Pt(2)
P(2)–Pt(2)–Cl(2)
P(2)–Pt(2)–Se(1)
Cl(2)–Pt(2)–Se(1)
P(2)–Pt(2)–Se(2)
Cl(2)–Pt(2)–Se(2)
Se(1)–Pt(2)–Se(2)
Se(2)–C(8)–C(9)
85.89(4)
88.63(10)
96.03(8)
171.06(9)
175.49(9)
94.69(8)
81.10(4)
110.9(8)
membered ‘M2SRX’ (X=SR or Cl) with dihedral angle
varying in the range 130–154° between the two coordi-
nation planes [16,20,23–26].
,
The Pt–Cl [2.338(2), 2.345(3) A], Pt–P, Se–C and
P–C distances are in agreement with the values re-
ported in the literature [1,4,5,8–10,16,24]. There are
distinctly two types of Pt–Se bonds, the one trans to
,
phosphine is longer (ꢀ0.1 A) than that trans to chlo-
ride, in accordance with the trans influence of the PR3
and Cl ligands. These distances can be compared with
those observed in [Pt2Cl2(m-SeEt)2(PEt3)2] [9], [Pt2Cl2(m-
Cl)(m-SeEt)(PMe2Ph)2] [22] and similar other complexes
[27–29]. The two Pt–Se–Pt angles [89.99(4), 85.89(4)°]
Fig. 3. TG curve for [Pd(SeBz)2]n.

S. Dey et al. / Journal of Organometallic Chemistry 623 (2001) 48–55
53
Table 3
Physical and analytical data for benzylselenolate complexes of palladium and platinum
Complex
Recrystallization solvent
Yield (%)
M.p. (°C)
Analysis: found (calc.) (%)
C
H
[{Pd(SeBz)2}n]
[{Pt(SeBz)2}n]
[Pt(SeBz)2(PPh3)2]
[Pd(SeBz)2(dppe)]
[Pt(SeBz)2(dppm)]
[Pt(SeBz)2(dppe)]
1a
1b
2
CH2Cl2
CH2Cl2
C6H6–hexane
82
37
40
69
65
55
58
66
38
80
75
43
60
70
70
94
68
72
55
48
40
135
160
112
171
157
187
156
137
169
150
149
205(d)
184
178(d)
178(d)
145
144
185(d)
146
37.3 (37.6)
31.6 (31.4)
56.1 (56.6)
56.3 (56.8)
50.5 (50.9)
51.2 (51.4)
40.4 (40.7)
44.2 (44.4)
39.7 (40.0)
51.9 (52.3)
55.9 (56.4)
29.8 (30.1)
34.1 (34.3)
39.8 (40.0)
36.7 (37.0)
36.7 (37.1)
29.9 (30.4)
37.2 (37.1)
39.6 (40.0)
33.1 (33.0)
33.1 (33.5)
3.0 (3.2)
2.4 (2.6)
3.9 (4.2)
4.4 (4.5)
3.6 (3.9)
3.8 (4.1)
5.9 (5.9)
7.1 (6.7)
3.8 (4.0)
3.7 (3.9)
4.4 (4.5)
5.3 (4.3)
5.3 (5.0)
3.4 (3.4)
4.0 (4.1)
6.1 (6.1)
4.7 (5.0)
3.2 (3.1)
5.9 (6.2)
5.0 (5.1)
5.6 (5.6)
3a
3b
3c
4a
4b
4c
4d
4e
4f
4g
4h
4i
5a
5b
5c
6a
6b
7
CH2Cl2–hexane
CH2Cl2–hexane
CH2Cl2–hexane
CH2Cl2–hexane
CH2Cl2–ethanol
CH2Cl2–hexane
CH2Cl2–hexane
CH2Cl2–methanol
CH2Cl2–ethanol
CH2Cl2–hexane
CH2Cl2–hexane
CH2Cl2–hexane
CH2Cl2–hexane
CH2Cl2–hexane
CH2Cl2–ethanol
CH2Cl2–hexane
CH2Cl2–ethanol
CH2Cl2–hexane
[Pd2Cl2(m-SeBz)2(PPrn3)2]
[Pd2Cl2(m-SeBz)2(PBun3)2]
[Pd2Cl2(m-SeBz)2(PMe2Ph)2]
[Pd2Cl2(m-SeBz)2(PPh3)2]
[Pd2Me2(m-SeBz)2(PPh3)2]
[Pt2Cl2(m-SeBz)2(PEt3)2]
[Pt2Cl2(m-SeBz)2(PPrn3)2]
[Pt2Cl2(m-SeBz)2(PMePh2)2]
[Pt2Me2(m-SeBz)2(PMe2Ph)2]
[Pd2Cl2(m-Cl)(m-SeBz)(PPrn3)2]
[Pt2Cl2(m-Cl)(m-SeBz)(PPrn3)2]
[Pt2Cl2(m-Cl)(m-SeBz)(PMePh2)2]
[Pd2Cl2(m-pz)(m-SeBz)(PPrn3)2] a
[Pt2Cl2(m-pz)(m-SeBz)(PPrn3)2] b
[Pt2Cl2(m-SBut)(m-SeBz)(PPr3n)2]
149
136
a N: found 3.1; calcd. 3.3%.
b N: found 2.9; calcd. 2.7%.
1
90°C (lit. 90–91°C) [35]. H-NMR in CDCl3: l=3.86
(s, 2J(Se–H) 14.5 Hz; SeCH2), 7.25–7.31 (m, Ph).
77Se{1H}-NMR in CDCl3: l=400.3. The tertiary phos-
phines (Strem Chemicals, USA) and NaBH4 were ob-
tained from commercial sources. Reactions were carried
out under nitrogen using Schlenk techniques in dry and
distilled analytical grade solvents. The 1H, 31P{1H},
77Se{1H} and 195Pt{1H}-NMR spectra were recorded
on a Bruker DPX-300 NMR spectrometer operating at
300.00, 121.49, 57.31, and 64.52 MHz, respectively.
Chemical shifts are relative to internal chloroform (l
tants were stirred for 5 h. The brown insoluble product
was filtered off, washed with water, ethanol and di-
ethylether and dried in vacuo (yield 1.19 g, 82%). The
product was sparingly soluble in dichloromethane. It
was extracted in 90% yield from dichloromethane using
Soxhlet apparatus. Pertinent data are summarized in
Table 3.
3.2. [{Pt(SeBz)2}n] (1b)
This was prepared in 95% yield in an analogous
manner to complex 1a from Bz2Se2 (259 mg, 0.76
mmol), NaBH4 (62 mg, 1.64 mmol) and K2PtCl4 (309
mg, 0.74 mmol). It was extracted in 37% yield from
dichloromethane using Soxhlet apparatus.
7.26 ppm) for H, external 85% H3PO4 for 31P, Me2Se
1
for 77Se and Na2PtCl6 in D2O for 195Pt. A 90° pulse was
used in every case. Thermogravimetric analysis (TGA)
was carried out on a Setaram 92-16-18 instrument. The
TG curves were recorded at a heating rate of 10°C
min−1 under a flow of argon. Microanalyses of the
complexes were carried out in the Analytical Chemistry
Division of this research centre.
3.3. [Pt(SeBz)2(PPh3)2] (2)
(a) Analogously as described for 3a, by using
[PtCl2(PPh3)2] (458 mg, 0.58 mmol) and NaSeBz [pre-
pared from Bz2Se2 (199 mg, 0.59 mmol) and NaBH4
(47.3 mg, 1.24 mmol) as starting materials]. Recrystal-
lized from benzene–hexane as orange crystals in 40%
yield.
3.1. [{Pd(SeBz)2}n] (1a)
To a dichloromethane solution (10 cm3) of Bz2Se2
(1.112 gm, 3.27 mmol) was added a methanolic solution
of NaBH4 (255 mg, 6.74 mmol) at room temperature
with stirring for 5 min whereupon the yellow coloured
solution became colourless. To this an aqueous solution
(10 cm3) of Na2PdCl4 (954 mg, 3.24 mmol) was added
immediately. A brown precipitate formed. The reac-
(b) To a dichloromethane suspension (8 cm3) of
[{Pt(SeBz)2}n] (55 mg, 0.10 mmol) was added solid
PPh3 (56 mg, 0.21 mmol) and the mixture was stirred
for 1 h. The clear solution was filtered and the filtrate
concentrated in vacuo, and washed with hexane and

54
S. Dey et al. / Journal of Organometallic Chemistry 623 (2001) 48–55
dried to give 28% title complex. The NMR spectra were
consistent with the product obtained in (a).
Cl)2(PPrn3)2] (162 mg, 0.24 mmol) (yellow or a mixture
of yellow and orange-red forms can be taken) was
added, and stirred for 5 h. The solvent was evaporated
in vacuo. Similarly 5b and 5c were prepared in refluxing
CH2Cl2.
3.4. Reaction of 2 with methyl iodide
To a dichloromethane solution (15 cm3) of [Pt(-
SeBz)2(PPh3)2] (50 mg, 0.05 mmol) excess MeI was
added, and the yellow coloured solution was stirred for
4 h. The solvent was evaporated in vacuo. The residue
was washed with hexane, diethylether and
dichloromethane to leave a pale yellow residue. 1H-
NMR (CDCl3): l=7.38–7.43 (br); 7.72–7.75 (br) (Ph).
31P{1H}-NMR (CDCl3): l=12.6 [1J(Pt–P)=2497 Hz].
Anal. Calc. for C36H30P2I2Pt (973.5): C, 44.4; H, 3.2.
Found: C, 43.9; H, 2.9%.
3.8. [Pd2Cl2(v-pz)(v-SeBz)(PPrn3)2] (6a)
To a solution of [Pd2Cl2(m-Cl)(m-SeBz)(PPrn3)2] (104
mg, 13 mmol) was added a methanolic solution (2 cm3)
of pzH (11 mg, 0.16 mmol) containing aq. NaOH
solution (1.62 cm3, 0.1 N) with vigorous stirring which
continued for 5 h. The solvent was evaporated in
vacuo. It was extracted with dichloromethane and
passed through a Florisil column. The solvent was
evaporated in vacuo and the residue was recrystallized
from dichloromethane–hexane as a yellow solid in 55%
(60 mg) yield.
3.5. [Pd(SeBz)2(dppe)] (3a)
(a) To a methanolic solution (15 cm3) of NaSeBz
(prepared from Bz2Se2 (125 mg, 0.37 mmol) and
NaBH4 (30 mg, 0.79 mmol) a dichloromethane suspen-
sion of [PdCl2(dppe)] (204 mg, 0.35 mmol) was added
at once and the resulting orange coloured mixture was
stirred for 4 h. The solvents were evaporated in vacuo
and the orange red residue was extracted with
dichloromethane (3×8 cm3), and was passed through a
Florisil column. The solvent was evaporated in vacuo
and the residue obtained as an orange crystalline solid.
Similarly 3b and 3c were prepared. 3a can also be
prepared from [Pd(SeBz)2]n and dppe as described for 2
(method (b)).
3.9. [Pt2Cl2(v-SBut)(v-SeBz)(PPr3n)2] (7)
To a dichloromethane solution (20 cm3) of [Pt2Cl2(m-
Cl)(m-SeBz)(PPrn3)2] (81 mg, 0.08 mmol) ButSH (0.5
cm3) was added in excess, and stirred for 5 h at room
temperature. The solvent was evaporated in vacuo. The
residue was washed with hexane to remove the excess
ButSH; the residue on recrystallization from
dichloromethane–hexane gave a pale yellow fibrous
compound:
3.10. X-ray crystallographic study of 4g
3.6. [Pd2Cl2(v-SeBz)2(PPrn3)2] (4a)
X-ray data on yellow crystals of [Pt2Cl2(m-
SeBz)2(PPrn3)2] (4g) were collected at room temperature
on an Enraf–Nonius CAD-4 diffractometer using
graphite monochromated Mo–Ka radiation (u=
A dichloromethane solution (10 cm3) of [Pd2Cl2(m-
Cl)2(PPrn3)2] (325 mg, 0.48 mmol) was added to a freshly
prepared methanolic solution of NaSeBz [prepared
from Bz2Se2 (165 mg, 0.49 mmol) and NaBH4 (39 mg,
1.03 mmol)] with stirring at room temperature. After
stirring the mixture for 4 h, the solvents were evapo-
rated in vacuo. The yellow-orange coloured residue was
extracted with dichloromethane (3×8 cm3), the solu-
tion was passed through a Florisil column and the
solvents evaporated in vacuo. The residue was dissolved
in acetone to leave some orange–red coloured solid
(yield 193 mg, m.p. 182°C; found: C, 40.0; H, 4.8%)
and the filtrate afforded yellow crystals (m.p. 156°C;
128 mg; 28%) which can be recrystallized with
dichloromethane–hexane.
,
0.71073 A) employing the ꢀ–2q scan technique. The
unit cell parameters (Table 4) were determined from 25
reflections measured by random search routine and
indexed by the method of short vectors followed by
least-squares refinement. The intensity data were cor-
rected for Lorentz-polarization and absorption effects.
The structure was solved using SHELXS-86 [36] and
SHELXL-97 [37] computer programs. The non-hydrogen
atoms were refined anisotropically.
Acknowledgements
Other binuclear bis(selenolato) bridged complexes
were prepared in a similar manner.
We thank Dr J.P. Mittal, Director, Chemistry and
Isotope Group and Dr Prithviraj, Head, Novel Materi-
als and Structural Chemistry Division, B.A.R.C. for
encouragement of this work. We are grateful to the
Head, Analytical Chemistry Division of this centre for
providing microanalyses.
3.7. [Pd2Cl2(v-Cl)(v-SeBz)(PPrn3)2] (5a)
To a dichloromethane solution (20 cm3) of [Pd2Cl2(m-
SeBz)2(PPrn3)2] (224 mg, 0.24 mmol) solid [Pd2Cl2(m-

S. Dey et al. / Journal of Organometallic Chemistry 623 (2001) 48–55
55
Table 4
[8] (a) J. Arnold, Prog. Inorg. Chem. 43 (1995) 353. (b) H.B. Singh,
N. Sudha, Polyhedron 15 (1996) 745.
Crystallographic data for [Pt2Cl2(m-SeBz)2(PPrn3)2] (4g)
[9] V.K. Jain, S. Kannan, R.J. Butcher, J.P. Jasinski, Polyhedron 14
(1995) 3641.
[10] V.K. Jain, S. Kannan, J. Organomet. Chem. 405 (1991) 265.
[11] S. Narayan, V.K. Jain, B. Verghese, J. Chem. Soc. Dalton
Trans. (1998) 2359.
[12] V.K. Jain, S. Kannan, J. Organomet. Chem. 418 (1991) 349.
[13] (a) J.Y.C Chu, D.G. Marsh, W.H.H. Gunther, J. Am. Chem.
Soc. 97 (1975) 4905. (b) D.L.J. Clive, W.A. Kiel, S.M. Menchen,
A. Singh, N.J. Curtis. J. Am. Chem. Soc. 102 (1980) 4438. (c)
H.K. Spencer, M.V. Lakshminathan, M.P. Cava, J. Am. Chem.
Soc. 99 (1977) 1470.
[14] (a) N.R. Kunchur, Acta Crystallogr. Sect. B 24 (1968) 1623. (b)
J.D. Higgins, J.W. Suggs, Inorg. Chim. Acta. 145 (1988) 247.
[15] (a) V.K. Jain, S. Kannan, E.R.T. Tiekink, J. Chem. Soc. M
(1994) 501. (b) A. Singhal, V.K. Jain, B. Varghese, E.R.T.
Tiekink, Inorg. Chim. Acta. 285 (1999) 190.
[16] V.K. Jain, R.P. Patel, K. Venkatasubramanian, Polyhedron 10
(1991) 851.
[17] V.K. Jain, S. Kannan, R.J. Butcher, J.P. Jasinski, J. Organomet.
Chem. 468 (1994) 285.
[18] P.S. Pregosin, Coord. Chem. Rev. 96 (1989) 1.
[19] V.K. Jain, S. Kannan, R. Bohra, Polyhedron 11 (1992) 1551.
[20] V.K. Jain, R.P. Patel, K.V. Muralidharan, R. Bohra, Polyhe-
dron 8 (1989) 2151.
[21] V.K. Jain, S. Kannan, R.J.Butcher, J.P. Jasinski, J. Chem Res S
(1996) 284.
Empirical formula
Formula weight
Temperature (K)
C32H56Cl2P2Pt2Se2
1121.71
293(2)
0.71073
,
Wavelength (A)
Crystal system, space group
Unit cell dimensions
Orthorhombic, Pbca
,
a (A)
16.774(4)
20.575(3)
23.602(4)
8146(3)
,
b (A)
,
c (A)
3
,
Volume (A )
Z
8
Dcalc (mg m−3
)
1.829
8.878
4288
Absorption coefficient (mm−1
F(000)
)
Crystal size(mm)
q range for data collection (°)
Index ranges
0.2×0.2×0.1
2.11–24.99
05h519, 05k524,
05l528
7102/7102 [Rint=0.0000]
90.6
Reflections collected/unique
Completeness to 2q=24.99 (%)
Absorption correction
Maximum and minimum
transmission
C scan
0.99 and 0.61
Refinement method
Full-matrix least-squares on
F2
Data/restraints/parameters
Goodness of fit on F2
Final R indices [I\2|(I)]
7102/0/362
1.055
R1=0.0401, wR2=0.0651
0.764 and −0.818
[22] V.K. Jain, S. Kannan, R.J.Butcher, J.P. Jasinski, Unpublished
results, X-ray structure of [Pt2Cl2(m-Cl)(m-SeEt)(PMe2Ph)2].
[23] E.M. Padilla, J.A. Golen, P.N. Richmann, C.M. Jensen, Polyhe-
dron 10 (1991) 1343.
[24] M.C. Hall, J.A.J. Jarvis, B.T. Kilbourn, P.G. Owston, J. Chem.
Soc. Dalton Trans. (1972) 1544.
Largest difference peak and hole
.
−3
,
(e A
)
[25] P.H. Bird, U. Siriwardane, R.D. Lai, A. Shaver, Can. J. Chem.
60 (1982) 2075.
References
[26] C.E. Briant, C.J. Gardner, T.S.A. Hor, N.D. Howells, D.M.P.
Mingos, J. Chem Soc. Dalton Trans. (1984) 2645.
[27] E.G. Hope, W. Levason, M. Webster, S.G. Murray, J. Chem.
Soc. Dalton Trans. (1986) 1003.
[28] E.G. Hope, H.C. Jewiss, W. Levason, M. Webster, J. Chem.
Soc. Dalton Trans. (1986) 1479.
[29] V.W. Day, D.A. Lesch, T.B. Rauchfuss, J. Am. Chem. Soc. 104
(1982) 1290.
[30] T.G. Appleton, M.A. Bennett, I.B. Tomkins, J. Chem. Soc.
Dalton Trans. (1976) 439.
[31] G.K. Anderson, J.A. Davis, D.J. Schoeck, Inorg. Chim. Acta 76
(1983) 251.
[32] R.J. Goodfellow, L.M. Venanzi, J. Chem. Soc. (1965) 7533. A.C.
Smithies, M. Rycheck, M. Orchin, J. Organomet. Chem. 12
(1968) 199
[1] (a) I.G. Dance, Polyhedron 5 (1986) 1037. (b) P.J. Blower, J.R.
Dilworth, Coord. Chem. Rev. 76 (1987) 121. (c) M.A. Ansari,
J.A. Ibers. Coord. Chem. Rev. 100 (1990) 223.
[2] (a) K.W. Kim, M.G. Kanatzidis, J. Am. Chem. Soc. 114 (1992)
4878. (b) W. Hipro, S. Dhingra, M.G. Kanatzidis, J. Chem. Soc.
Chem. Commun. (1992) 557. (c) M.A. Malik, P. O’Brien, D.J.
Otway, Phosphorus Sulfur Silicon 136–138 (1998) 431.
[3] L. Dong, S.B. Duckett, F.F. Ohman, W.D. Jones, J. Am. Chem.
Soc. 114 (1992) 151.
[4] (a) L.Y. Chiang, J.W. Swirczewski, R. Kastrup, C.S. Hsu, R.B.
Upasani, J. Am. Chem. Soc. 113 (1991) 6574. (b) S. Eijsbouts,
V.H.J. De Beer, R.Prins, J. Catal. 109 (1988) 217. (c) M.
Misono, N.Nojiri, Appl. Catal. 64 (1990) 1.
[33] H.C. Clark, A.B. Goel, V.K. Jain, K.G. Tyers, C.S. Wong, J.
Organomet. Chem. 321 (1987) 123.
[34] A. Singhal, V.K. Jain, J. Chem. Soc. Dalton Trans. (1993) 1515.
[35] J.Q. Li, W.L. Bao, P. Lue, X.J. Zhou, Synth. Commun. 21
(1991) 799.
[5] (a) T. Yamamoto, Jpn. Patent 61215661 (1986); Chem. Abstr.
106 (1987) 87694h. (b) Y. Idota, M. Yagihara, Fuji Photo Films
Co. Ltd, Jpn. Patent 61186959 (1986); Chem. Abstr. 106 (1987)
166325s. (c) T. Oota, K. Yoshioka, T. Akyama, S. Mori, Jpn.
Patent 07205548 (1995); Chem. Abstr. 123 (1995) 325855j.
[6] A. Singhal, V.K. Jain, R. Misra, B. Varghese, J. Mater. Chem.
(2000) 1121.
[36] G.M. Sheldrick, SHELXS-86, Program for Crystal Structure De-
termination, University of Go¨ttingen, 1986.
[7] S. Narayan, V.K. Jain, K. Panneerselvam, T.H. Lu, S.F. Tung,
Polyhedron 18 (1999) 1253.
[37] G.M. Sheldrick, SHELXL-97, Program for Crystal Structure refin-
ement, University of Go¨ttingen, 1997.