Synthesis and characterization of 3-dimethylaminopropyl selenolate complexes of palladium(II) and platinum(II)

Article abstract of DOI:10.1016/S0020-1693(03)00080-X

Bis(3-dimethylaminopropyl)diselenide was prepared by the reaction of Na₂Se₂ with Me₂NCH₂CH₂CH₂Cl. 3-Dimethylaminopropylselenolate complexes of palladium and platinum of the formulae [M(SeCH₂CH₂CH₂NMe₂)Cl] ₂, [M(SeCH₂CH₂CH₂NMe₂)₂] (M=Pd or Pt), [Pd(OAc)(SeCH₂CH₂CH₂NMe₂)], [PtCl(SeCH₂CH₂CH₂NMe₂)(PR ₃)]₂ (PR₃=PMePh₂ or PPr₃), [Pt(SeCH₂CH₂CH₂NMe₂) ₂(P-P)] (P-P=dppm, dppe or 2PPh₃) have been synthesized by using either the diselenide or its reduction product from the reaction with NaBH₄. All complexes have been characterized by elemental analysis, IR and NMR (¹H, ¹³C, ³¹P, ⁷⁷Se, ¹⁹⁵Pt) spectroscopy. The stereochemistry of these complexes has been deduced from the NMR spectroscopic data. The structure of [Pd(SeCH₂CH₂CH₂NMe₂)Cl] ₂ was established by single crystal X-ray diffraction analysis. Each palladium atom in the dimer is surrounded by two μ-Se atoms, a nitrogen atom and a chloride ligand.

Full text of DOI:10.1016/S0020-1693(03)00080-X

Inorganica Chimica Acta 349 (2003) 104ꢁ110
/
www.elsevier.com/locate/ica
Synthesis and characterization of 3-dimethylaminopropyl selenolate
complexes of palladium(II) and platinum(II)
Sandip Dey a, Vimal K. Jain a,*, Axel Knoedler b, Wolfgang Kaim b,*
a Novel Materials and Structural Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400 085, India
b Institut fur Anorganische Chemie, Universitat Stuttgart, Pfaffenwaldring 55, D-70569 Stuttgart, Germany
¨
¨
Received 20 September 2002; accepted 20 January 2003
Abstract
Bis(3-dimethylaminopropyl)diselenide was prepared by the reaction of Na2Se2 with Me2NCH2CH2CH2Cl. 3-Dimethylamino-
propylselenolate complexes of palladium and platinum of the formulae [M(SeCH2CH2CH2NMe2)Cl]2, [M(SeCH2CH2CH2NMe2)2]
(Mꢀ
/
Pd or Pt), [Pd(OAc)(SeCH2CH2CH2NMe2)], [PtCl(SeCH2CH2CH2NMe2)(PR3)]2 (PR3ꢀ/PMePh2 or PPr3), [Pt(SeCH2-
CH2CH2NMe2)2(PÃ
/
P)] (PÃ
/
Pꢀ
/
dppm, dppe or 2PPh3) have been synthesized by using either the diselenide or its reduction product
from the reaction with NaBH4. All complexes have been characterized by elemental analysis, IR and NMR (1H, 13C, 31P, 77Se, 195Pt)
spectroscopy. The stereochemistry of these complexes has been deduced from the NMR spectroscopic data. The structure of
[Pd(SeCH2CH2CH2NMe2)Cl]2 was established by single crystal X-ray diffraction analysis. Each palladium atom in the dimer is
surrounded by two m-Se atoms, a nitrogen atom and a chloride ligand.
# 2003 Elsevier Science B.V. All rights reserved.
Keywords: Crystal structures; Palladium complexes; Platinum complexes; Selenolate ligand
1. Introduction
2-dimethylaminoethanylchalcogenolate ions (Me2N-
CH2CH2Eꢂ; Eꢀ
S, Se, Te) is in general very similar,
however subtle differences in chemical and physical
/
The chemistry of platinum group metal chalcogen-
olates has attracted considerable attention for more
than two decades [1]. There are several obvious reasons
for the sustained interest in this area as these complexes
show a wide structural diversity [1] and find several
applications in catalysis [2]. More recently, these com-
plexes have been shown to serve as molecular precursors
properties between S and Se/Te complexes have been
noticed [5,7ꢁ
derived from mercaptoamines has been investigated in
considerable detail [11ꢁ25]. Their structure is greatly
/
10]. The chemistry of metal complexes
/
influenced by the nature of the metal ion, the number of
carbon atoms separating the N and S centers and the
substituents on the N-atom. For example, a-mercaptoa-
mines (such as 2-mercaptonicotinic acid [15]) and b-
for the synthesis of metal chalcogenides [3ꢁ5] for
/
electronic devices [6]. Most of these complexes are
non-volatile, insoluble or poorly soluble oligomeric
species, thus limiting their utility as precursors for the
synthesis of metal chalcogenides. To suppress polymer-
ization we have employed internally functionalized
ligands such as 2-(RC5H3N)Eꢂ or Me2NCH2CH2Eꢂ
mercaptoamines (such as R2NCH2CH2SH where Rꢀ
/H
or Me [11ꢁ14,16,17]) yield metal chelates whereas g-
/
mercaptoamines (such as Me2CH2CH2CH2SH and
related derivatives) behave both as simple thiolate
ligands (monodentate as well as bridging through sulfur
(Eꢀ
compared with their sulfur analogues (Me2-
NCH2CH2Sꢂ) [11ꢁ
14]. The coordination behaviour of
/
Se or Te) [5,7ꢁ
/
10]. The latter ligands can be
[18ꢁ/21]) and as chelating ligands, bridging or non-
bridging [14,22ꢁ/25]. These structural variations assisted
/
by the carbon chain length of mercaptoamines have
prompted us to examine the chemistry of the heavier
homologs of g-mercaptoamine, i.e., R2NCH2CH2-
* Corresponding authors. Tel.: ꢃ
9613.
E-mail address: jainvk@apsara.barc.ernet.in (V. Jain).
/
91-22-2559-5095; fax: ꢃ91-22-551
/
CH2Eꢂ (Eꢀ
/Se and Te). Herein we report the synthesis
of (Me2NCH2CH2CH2Se)2 and of palladium(II) and
0020-1693/03/$ - see front matter # 2003 Elsevier Science B.V. All rights reserved.
doi:10.1016/S0020-1693(03)00080-X

S. Dey et al. / Inorganica Chimica Acta 349 (2003) 104ꢁ
/110
105
platinum(II) complexes containing Me2NCH2CH2-
CH2Seꢂ. Spectroscopic data and the X-ray structure
of [Pd(SeCH2CH2CH2NMe2)Cl]2 are also reported.
2.1.3. [PtCl(SeCH2CH2CH2NMe2)]2 (1b)
An aqueous solution (10 cm3) of K2PtCl4 (361 mg,
0.87 mmol) was added to a stirred methanolic solution
(15 cm3) of (Me2NCH2CH2CH2Se)2 (144 mg, 0.44
mmol). Stirring continued for 4 h at room temperature
(r.t.) whereupon a pale yellow precipitate formed. The
precipitate was filtered, washed thoroughly with water,
MeOH, acetone and hexane and dried in vacuo. This
2. Experimental
All reactions were carried out in dry and distilled
analytical grade solvents under N2 using conventional
Schlenk technique to prevent oxidation of the selenolate
ion. Tertiary phosphines (Strem Chemicals, USA) and
was recrystallized from DMFꢁ
/
ether as orangeꢁred
/
crystals in 35% yield (120 mg). M.p. (dec.) 188 8C.
Anal. Found: C, 12.7; H, 3.6; N, 5.0. Calc. for
C10H24Cl2N2Pt2Se2: C, 15.2; H, 3.1; N, 3.5%.
Me2NCH2CH2CH2Cl×
mercial sources. The Pd and Pt complexes Na2PdCl4,
K2PtCl4, MCl2(PÃP) (PÃPꢀ2PPh3, dppm, dppe) and
[M2Cl2(m-Cl)2(PR3)2] (PR3ꢀPPr3, PMePh2, PPh3) were
/
HCl were obtained from com-
/
/
/
2.1.4. [Pd(SeCH2CH2CH2NMe2)2] (2a)
To a freshly prepared methanolic solution (8 cm3) of
NaSeCH2CH2CH2NMe2 [prepared from (Me2NCH2-
CH2CH2Se)2 (385 mg, 1.17 mmol) and NaBH4 (90 mg,
2.37 mmol)], a solution (25 cm3) of Na2PdCl4 (341 mg,
1.16 mmol) in the same solvent was added with vigorous
stirring. The dark brown solution was stirred for 3 h at
r.t. The solvent was stripped off in vacuo. The residue
/
prepared according to literature methods [26]. Melting
points were determined in capillary tubes and are
uncorrected. Microanalysis was performed by the Ana-
lytical Chemistry Division of BARC. 1H, 13C{1H},
31P{1H}, 77Se{1H} and 195Pt{1H} NMR spectra were
recorded on a Bruker DPX-300 NMR spectrometer
operating at 300, 75.46, 121.49, 57.24 and 64.52 MHz,
respectively. Chemical shifts are relative to internal
was extracted with hexane (3ꢄ
20 cm3) and passed
through a Florisil column. The volume of the solution
/
1
CHCl3 peak (d 7.26 H and 77.0 for 13C) and external
was reduced to 8 cm3. To this a few drops of pentane
85% H3PO4 for 31P, Me2Se for 77Se and Na2PtCl6 for
195Pt. UVꢁ
Vis absorption spectra were recorded on a
/
were added and cooling to ꢂ5 8C for several hours gave
/
brownish red needle-shaped crystals which lost crystal-
linity on drying (yield: 202 mg, 40%). M.p. 102 8C. Anal.
Found: C, 26.4; H, 5.3; N, 5.3. Calc. for C10H24-
N2PdSe2: C, 27.5; H, 5.5; N, 6.4%.
Bruins Instruments Omega 10 spectrophotometer. Cyc-
lic voltammetry was carried out at 100 mV sꢂ1 scan rate
in CH2Cl2 0.1 M Bu4NPF6 using a three electrode
configuration (glassy carbon working electrode, Pt
counter electrode, Ag/AgCl reference) and a PAR 273
potentiostat and function generator. The ferrocene/
ferrocenium couple served as internal reference.
2.1.5. [Pt(SeCH2CH2CH2NMe2)2]n (2b)
To a freshly prepared methanolic solution (10 cm3) of
NaSeCH2CH2CH2NMe2 [prepared from (Me2NCH2-
CH2CH2Se)2 (241 mg, 0.73 mmol) and NaBH4 (57 mg,
1.50 mmol)] an aq. solution (10 cm3) of K2PtCl4 (300
mg, 0.72 mmol) was added and the mixture was stirred
for 4 h. The solvents were stripped off in vacuum and
the residue was thoroughly washed with water, MeOH,
acetone, ether and finally dried in vacuo (yield: 152 mg,
40%). The dark red product was insoluble in all
common organic solvents. M.p. (dec.) 205 8C. Anal.
Found: C, 20.5; H, 4.4; N, 4.7. Calc. for C10H24N2PtSe2:
C, 22.9; H, 4.6; N, 5.3%.
2.1. Synthesis
2.1.1. (Me2NCH2CH2CH2Se)2
Bis(3-dimethylaminopropyl)diselenide was prepared
in an analogous manner to (Me2NCH2CH2Se)2 [5],
using Me2NCH2CH2CH2Cl and Na2Se2. The orangeꢁ
red liquid was fractionally distilled under vacuum.
The fraction distilling at 134ꢁ140 8C/2 mmHg was
/
/
collected and was found spectroscopically pure (NMR,
Table 1).
2.1.2. [PdCl(SeCH2CH2CH2NMe2)]2 (1a)
2.1.6. [Pd(OAc)(SeCH2CH2CH2NMe2)] (3)
A methanolic solution (10 cm3) of Na2PdCl4 (1.242 g,
4.22 mmol) was added to a stirred methanolic solution
of (Me2NCH2CH2CH2Se)2 (704 mg, 2.13 mmol). A
yellow precipitate formed immediately. The reactants
were stirred for 3 h. The yellow precipitate was filtered,
To a benzene solution (15 cm3) of 2a (73 mg, 0.17
mmol), solid Pd(OAc)2 (39 mg, 0.17 mmol) was added
with stirring. To the turbid solution acetone (15 cm3)
was added and the mixture was stirred at r.t. for 2 h. The
solvents were evaporated in vacuo and the residue was
washed with hexane and extracted with acetone. The
solution was passed through a Florisil column, concen-
washed with MeOH (2ꢄ
and finally dried in vacuo (yield 850 mg, 65%). The
product was recrystallized from CH2Cl2ꢁacetone as
orangeꢁred crystals in 38% yield (320 mg). M.p.
/
10 cmꢂ3), acetone and Et2O
/
trated to 2 cm3 and cooled at ꢂ
5 8C for 24 h to yield a
/
/
yellow solid (44 mg, 40%). M.p. (dec.) 158 8C. Anal.
Found: C, 24.7; H, 4.9; N, 4.1. Calc. for C7H15NO2-
PdSe: C, 25.4; H, 4.6; N, 4.2%.
205 8C dec. Anal. Found: C, 19.3; H, 3.6; N, 5.0. Calc.
for C10H24Cl2N2Pd2Se2: C, 19.6; H, 3.9; N, 4.6%.

Table 1
1H, 13C{1H}, 31P{1H}, 77Se{1H} and 195Pt{1H} NMR data for 3-(dimethylamino)propaneselenolate complexes of palladium(II) and platinum(II)
Complex
1H d in ppm
13C{1H} d in ppm
31P{1H}
77Se{1H} a
316
195Pt{1H} b
(Me2NCH2CH2CH2Se)2
1.90 (m, SeÃCÃ
/
/
CH2); 2.20 (s, NMe2); 2.35 (t, 7.1 Hz, 28.2 (SeCH2); 29.2 (s, SeCH2CH2); 45.4 (s,
SeCH2); 2.95 (t, 7.1 Hz, NCH2)
1.93ꢁ
2.48 (m, NCH2CH2); 2.66, 2.74 (each s, NMe2); 22.6 (s, 1J(77Seꢁ13
3.46ꢁ3.52 (m, SeCH2) 27.9 (s, SeCH2Ã
CH2, 2J(Seꢁ
NMe2); 59.3 (s, NCH2)
[PdCl(SeCH2CH2CH2NMe2)]2 (1a)
/
/
C)ꢀ
/
64 Hz, SeCH2);
C)ꢀ35 Hz);
18
/
/
/
/
50.0, 52.4 (each s, NMe2); 65.1 (s, NCH2)
[PtCl(SeCH2CH2CH2NMe2)]2 (1b)
[Pd(SeCH2CH2CH2NMe2)2] (2a)
1.93ꢁ
/
2.05 (m, SeCÃ
/
CH2); 2.21, 2.23 (each s, NMe2);
20.7, 24.7 (each s, SeCH2); 30.8, 32.6 (each
ꢂ
/
31
2.32ꢁ
/
2.56 (m, NCH2, SeCH2)
s, SeCÃ
/
CH2); 45.5 (s, NMe2); 59.3, 59.5 (s,
NCH2)
ꢂ
/
161
[Pd(OAc)(SeCH2CH2CH2Nme2)] (3)
trans-[PtCl(SeCH2CH2CH2N-
1.95, 2.08 (each s); 2.45, 2.67 (each s, NMe2); 2.90ꢁ
(m, SeCH2); 2.61ꢁ2.75 (br, m, NCH2); 2.25 (NCCH2) CH2); 50.0, 51.5 (NMe2, OAc); 64.4
(NCH2); 176.7 (CÄO)
/
2.94 19.4, 23.7 (each s, SeCH2); 27.7 (s, SeCÃ
/
ꢂ
/
32
/
/
1.05 (t, 7 Hz, PCH2CH2Me); 1.56ꢁ
/
1.85 (m, PCH2CH2,
ꢂ
/
0.1 1J(Ptꢁ
P)ꢀ3122 Hz
/
ꢂ
/
3960 (d)
1J(Ptꢁ
P)ꢀ
Hz
4093 (d) d
1J(Ptꢁ
P)ꢀ
Hz
4235 (t)
1J(Ptꢁ
P)ꢀ
Hz
c
Me2)(PPr3)]2 (4a)
NCH2); 2.24 (s, NMe2); 2.45 (br, NCH2); 2.62 (br, m,
SeCH2)
/
/
/
3097
3294
2410
cis-[PtCl(SeCH2CH2CH2NMe2)(P-
MePh2)]2 (4b)
1.81 (t, NCCH2); 1.98, 2.25 (each s, NMe2); 2.03ꢁ
(m, PMe, NCH2CH2); 2.44, 3.32 (each m, SeCH2);
7.27ꢁ7.44 (m), 7.63ꢁ7.70 (m) [Ph]
2.08 (s, NMe2, 2.42ꢁ2.52 (m, SeCH2); 2.02ꢁ
NCH2); 1.56ꢁ1.67 (m, NCCH2Ã
); 4.34 (t, 2J(Pꢁ
10.4, 3J(Ptꢁ
H)ꢀ44 Hz, PCH2); 7.39ꢁ7.49 (m); 7.82ꢁ
7.90 (m) [Ph]
1.54 (m, NCÃ
PCH2); 2.02 (s, NMe2); 7.36ꢁ
[Ph]
1.65 (s, NMe2); 1.60ꢁ
SeCH2, NCH2); 7.34 (br, PPh3)
/
2.24
ꢂ
/
1.1 1J(Ptꢁ
P)ꢀ3273 Hz
/
ꢂ/
/
/
/
/
/
[Pt(SeCH2CH2CH2NMe2)2(dppm)] (5a)
/
/2.10 (m,
ꢂ/
52.5 1J(Ptꢁ
/
ꢂ/
/
/
/
H)ꢀ
/
P)ꢀ
2J(Seꢁ
Hz
46.6 1J(Ptꢁ
2851; 2J(Seꢁ
P)ꢀ32 Hz
18.4 1J(Ptꢁ
2932 Hz
/2401 ;
/
/
/
/
/
/
/
P)ꢀ
/
27
[Pt(SeCH2CH2CH2NMe2)2(dppe)] (5b)
[Pt(SeCH2CH2CH2NMe2)2(PPh3)2] (6)
/
CH2); 1.99ꢁ
/
2.40 (m, NCH2, SeCH2,
7.40 (m); 7.80ꢁ7.87 (m)
/P)ꢀ
/
55 2J(Seꢁ
P)ꢀ62 Hz
/
ꢂ
/
4946 (t)
1J(Ptꢁ
P)ꢀ
Hz
4907 (t)
1J(Ptꢁ
P)ꢀ
Hz
/
/
/
/
/
/
2865
/
/
1.72 (m, NCCH2); 2.04ꢁ
/
2.32 (m,
/P)ꢀ
/
18 2J(Seꢁ
P)ꢀ17 Hz
/
ꢂ/
/
/
/
2938
a
77Se: nuclear spin Iꢀ
/
1/2, natural abundance 7.6%.
195Pt: nuclear spin Iꢀ1/2, natural abundance 33.8%. The half line widths of 195Pt signals are 50ꢁ
spectra.
b
1
/
/
100 Hz, hence the variation in the J(Ptꢁ
/
P) coupling constants measured from 31P and 195Pt
1.0 [1J(Ptꢁ 3155 Hz]. 195Pt NMR d: ꢂ
P)ꢀ 3963(d)
c
When the solution is left for a day isomerization takes place to give a mixture of cis and trans isomers. d 31Pꢀ
[1J(Ptꢁ 3116, 2J(Ptꢁ 4065(d) [1J(Ptꢁ 3155; 2J(Ptꢁ
P)ꢀ Pt)ꢀ1060 Hz]; ꢂ P)ꢀ Pt)ꢀ972 Hz].
2J(Ptꢁ
Pt)ꢀ953 Hz.
/
ꢂ
/
0.1 [1J(Ptꢁ
/
P)ꢀ3120 Hz]; ꢂ
/
/
/
/
/
/
/
/
/
/
/
/
/
/
d
/
/

S. Dey et al. / Inorganica Chimica Acta 349 (2003) 104ꢁ
/
110
107
for
2.1.7. [PtCl(SeCH2CH2CH2NMe2)(PMePh2)] (4b)
To a freshly prepared methanolic solution (10 cm3) of
NaSeCH2CH2CH2NMe2 [prepared from (Me2NCH2-
CH2CH2Se)2 (72 mg, 0.22 mmol) and NaBH4 (17 mg,
0.45 mmol)] was added an acetone (20 cm3) suspension
of [Pt2Cl2(m-Cl)2(PMePh2)2] (196 mg, 0.21 mmol) with
stirring under a nitrogen atmosphere. The pale yellow
reaction mixture was stirred for 4 h. The solvents were
stripped off in vacuum and the residue was washed with
Table 2
Crystallographic
and
[PdCl(SeCH2CH2CH2NMe2)]2 (1a)
structure
refinement
data
Chemical formula
Formula weight
Temperature (K)
C10H24Cl2N2Pd2Se2
613.93
173(2)
˚
l (A)
0.71073
monoclinic
P21/n
Crystal system
Space group
Unit cell dimensions
hexane and was extracted with CH2Cl2 (6ꢄ
3 cm3). The
/
˚
a (A)
10.395(2)
8.6978(17)
19.160(4)
98.18(3)
1714.7(6)
4
˚
b (A)
solution was passed through a Florisil column and the
volume of the solution reduced to 5 cm3. After adding
a few drops of hexane, the solution was kept in the
˚
c (A)
b (8)
Volume (A )
3
˚
freezer (ꢂ5 8C) to yield pale yellow fibrous crystals in
/
Z
Dcalc (g cmꢂ1
)
2.378
48% yield (120 mg). M.p. 126 8C. Anal. Found: C, 35.8;
H, 4.2; N, 2.8. Calc. for C18H25ClNPPtSe: C, 36.3; H,
4.2; N, 2.4%.
Crystal size (mm)
0.3ꢄ/0.25ꢄ0.2
/
Absorption correction
Reflections collected/unique
Data/restraints/parameters
Final R1, vR2 indices
R1, vR2 (all data)
C scan
4359/4139
4139/0/164
0.0356, 0.0797
0.0491, 0.0860
2.1.8. [PtCl(SeCH2CH2CH2NMe2)(PPr3)] (4a)
Prepared in a manner similar to 4b and recrystallized
from hexane in 45% yield, m.p. 118 8C. Anal. Found: C,
30.7; H, 5.9; N, 2.4. Calc. for C14H33ClNPPtSe: C, 30.2;
H, 6.0; N, 2.5%.
3
˚
Largest difference peak and hole (e A )
1.310 and ꢂ1.297
/
and the hydrogen atoms were introduced using the
appropriate riding model.
2.1.9. [Pt(SeCH2CH2CH2NMe2)2(dppm)] (5a)
Prepared from PtCl2dppm and 2NaSeCH2CH2-
CH2NMe2 and recrystallized from tolueneꢁhexane in
/
3. Results and discussion
45% yield, m.p. 184 8C. Anal. Found: C, 42.4; H, 3.9; N,
2.4. Calc. for C35H46N2P2PtSe2: C, 46.2; H, 5.1; N,
3.1%.
Synthetic routes to 3-dimethylaminopropylselenolate
complexes of palladium(II) and platinum(II) are given in
Scheme 1. In a few cases the analytical data were
unsatisfactory. Poor solubility of 1b and 2b in non-
coordinating solvents and dissociation in coordinating
solvents rendered their purification difficult while slow
air oxidation of the phosphine/selenolate in 5a gave
variable analyses.
2.1.10. [Pt(SeCH2CH2CH2NMe2)2(dppe)] (5b)
Prepared from PtCl2dppe and 2NaSeCH2CH2CH2-
NMe2 and recrystallized from acetoneꢁhexane in 60%
/
yield. Anal. Found: C, 46.1; H, 5.0; N, 2.8. Calc. for
C36H48N2P2PtSe2: C, 46.8; H, 5.2; N, 3.0%.
The reaction of Na2PdCl4 with (Me2NCH2-
2.1.11. [Pt(SeCH2CH2CH2NMe2)2(PPh3)2] (6)
Prepared from PtCl2(PPh3)2 and 2NaSeCH2-
CH2CH2Se)2 in methanol yields an orangeꢁ
precipitate which, after recrystallization from CH2Cl2ꢁ
acetone, gave microcrystals of the empirical composi-
tion [PdCl(SeCH2CH2CH2NMe2)]n (1a). The IR spec-
trum of 1a exhibited a band at 291 cmꢂ1, attributable to
/
yellow
/
CH2CH2NMe2 and recrystallized from tolueneꢁpentane
/
in 55% yield. Anal. Found: C, 52.3; H, 5.3; N, 2.5. Calc.
for C46H54N2P2PtSe2: C, 52.6; H, 5.2; N, 2.7%.
nPdÃ
/
Cl. The structure of the complex has been un-
2.2. Crystallography
ambiguously established by X-ray diffraction, 1a is
dimeric. The structure is similar to that of g-mercaptoa-
mine complexes of palladium(II) and platinum(II), e.g.
[PdCl(SCH2CH2CH2NMe2)]2 [24], [PdCl{SCH2CH2(2-
N(Me)C5H7)}]2 [23] or [PtBr(SC4H8NMe-4)]2 [25].
Treatment of Na2PdCl4 with 2 equiv. of NaSeCH2-
CH2CH2NMe2 yields a hexane-soluble brown product
of the composition [Pd(SeCH2CH2CH2NMe2)2] (2a).
However, a similar reaction with K2PtCl4 gave an
insoluble red product 2b. These complexes may appear
to be bis-chelates. However, the corresponding [Pd-
(SeCH(Me)CH2NMe2)2]6 was shown to be hexameric by
X-ray data of an orangeꢁyellow crystal of
[PdCl(SeCH2CH2CH2NMe2)]2 (1a) were collected on a
Siemens P3 diffractometer using graphite monochro-
/
mated Mo Ka radiation and employing the v ꢁ
/2u scan
technique. The unit cell parameters (Table 2) were
determined from 25 reflections measured by a random
search routine. The intensity data were corrected for Lp
and absorption effects (c scans). The structure was
solved by direct methods (program SHELXTL-5.1 [27]).
The non-hydrogen atoms were refined anisotropically

108
S. Dey et al. / Inorganica Chimica Acta 349 (2003) 104ꢁ
/110
Scheme 1.
X-ray crystallography [28]. A similar hexameric struc-
ture has been reported for the nickel thiolato complex
[Ni(SCH2CH2CH2NMe2)2]6 [19]. In both cases oligo-
merization takes place via the chalcogen bridges while
the NMe2 groups remain free. It is possible that 2a may
have a similar hexameric structure in the solid. The FAB
mass spectrum of 2a displayed a multiplet at m/z 2619
with an isotopic pattern attributable to the hexamer.
The 13C{1H} NMR spectrum of the complex, however,
exhibited two singlets each for three methylene carbons.
This suggests that lower oligomeric species (such as
dimeric) may be present in CDCl3 solution. When 2a is
gesting the formation of trans-[M(SeCH2CH2CH2N-
Me2)2(PPh3)2].
Treatment of [Pt2Cl2(m-Cl)2(PR3)2] (PR3ꢀ
/
PPr3n,
PMePh2) with 2 equiv. of NaSeCH2CH2CH2NMe2
resulted in the formation of [PtCl(SeCH2CH2CH2N-
Me2)(PR3)]. These complexes show a single resonance in
the 31P NMR spectra with 195Pt satellites and a doublet
in the 195Pt NMR spectra due to coupling with one
phosphorus nucleus. Although the NMR data of these
complexes are very similar to recently reported mono-
nuclear complexes, [MCl(ECH2CH2NMe2)(PR3)] (Mꢀ
Pd or Pt; EꢀS, Se, Te) [5,7,8,31], the magnitude of
1J(Ptꢁ
P) for the former series is significantly reduced
and shows a phosphine dependence. The magnitude of
1J(Ptꢁ
P) (Â3400 Hz) for [PtCl(ECH2CH2NMe2)(PR3)]
/
/
treated with Pd(OAc)2,
[Pd(OAc)(SeCH2CH2CH2NMe2)] is formed (nCÄ
1613 cmꢂ1).
The reaction of [PtCl2(PÃ
a
redistribution product
/
/
O
/
/
/
P)] (PÃ
/
Pꢀ/dppm or dppe)
shows little dependence either on the phosphine ligand
or on the nature of the chalcogen atom (S, Se, Te). The
with 2 equiv. of NaSeCH2CH2CH2NMe2 gave mono-
nuclear [Pt(SeCH2CH2CH2NMe2)2(PÃP)] as yellow
crystalline solids. The 31P{1H} and 195Pt{1H} (nuclear
spin Iꢀ1/2 with a natural abundance of 33.8%) data are
1
/
magnitude of J(Ptꢁ
/P) for the present series of com-
plexes can be compared with that of [Pt2Cl2(m-
/
SeR?)2(PR3)2] (R?ꢀEt, Bz, Ph) [32], therefore, these
/
similar to those reported for several organochalcogen-
olates of platinum(II) [7,29]. These complexes have been
assigned a cis configuration.
complexes may be assigned a dimeric structure with
selenolate bridges. This is further substantiated by the
presence of 2J(PtꢁPt) coupling in the 195Pt NMR
/
The reaction of [PtCl2(PPh3)2] with 2 equiv. of
NaSeCH2CH2CH2NMe2 afforded [Pt(SeCH2CH2CH2-
NMe2)2(PPh3)2]. A freshly prepared CDCl3 solution of
the complex exhibited singlet and triplet signals in the
31P{1H} and 195Pt{1H} NMR spectra, respectively. The
31P and 195Pt chemical shifts and the magnitude of
spectra. Complex 4a is formed as a sym ꢁ
which slowly isomerizes to a mixture of sym ꢁ
isomers as revealed by NMR spectroscopy. Compound
4b is isolated as sym ꢁcis isomer.
In contrast to the reactions of NaSeCH2CH2-
CH2NMe2 with chloro-bridged platinum complexes,
the similar reaction with [Pd2Cl2(m-Cl)2(PMePh2)2] after
/
trans isomer
/cis/trans
/
1J(Ptꢁ
P) are similar to [Pt(SePh)2(PPh3)2] [29,30] sug-
/

S. Dey et al. / Inorganica Chimica Acta 349 (2003) 104ꢁ
/110
109
Table 3
UVꢁ
Vis absorption a and electrochemical data of complexes in
CH2Cl2 and 0.1 M Bu4NPF6/CH2Cl2 b, respectively
hexameric 2a. Typically, the palladium compounds
display absorptions at lower energies than the platinum
analogues [7,8]. The peak potentials for irreversible
oxidation reflect the donor capacity of triorganopho-
sphine co-ligands.
/
b
Complex
lmax (o)
Epa
[PdCl(SeCH2CH2CH2NMe2)]2 (1a)
298 (10 000), 335 (sh), 1.17
370 (sh)
298 (13 800), 338
[Pd(SeCH2CH2CH2NMe2)2] (2a)
3.2. Crystal structure analysis of
[PdCl(SeCH2CH2CH2NMe2)]2 (1a)
(9900), 440 (5000)
251 (6700), 271 (7000), 0.59
290 (6400)
[PtCl(m-SeCH2CH2CH2N-
Me2)(PPr3n )]2 (4a)
[PtCl(m-SeCH2CH2CH2NMe2)-
(PMePh2)]2 (4b)
249 (12 500), 270
(11 500), 286 (9300),
315 (4470)
0.58
The molecular structure of 1a is shown in Fig. 1,
selected bond lengths and angles are summarized in
Table 4. The structure contains two distorted square
planar palladium atoms which are held together by two
symmetrically bridging Se atoms of the chelating
selenolate ligands. The two chloride ligands are mu-
tually trans. Each palladium atom is surrounded by Cl,
N and two Se atoms. The various bond lengths and
angles in the ‘PdClNSe2’ fragments are comparable. The
[Pt(SeCH2CH2CH2NMe2)2(dppm)]
(5a)
266 (29 000), 369 (1700) 0.47
a
Wavelengths lmax at the absorption maxima in nm, molar
extinction coefficients in Mꢂ1 cmꢂ1
.
b
From cyclic voltammetry at 100 mV sꢂ1 scan rate, Epa anodic
peak potentials in V vs. FeCp2/FeCp2ꢃ
.
˚
PdÁ Á ÁPd distance at 3.413(1) A is significantly longer
recrystallization afforded 1a. The reaction mixture
showed several peaks in the 31P NMR spectrum.
than expected for any direct PdÁ Á ÁPd bonding interac-
Table 4
˚
Selected bond lengths (A) and angles (8) for [PdCl(SeCH2-
CH2CH2NMe2)]2 (1a)
3.1. Absorption spectra and electrochemistry
Bond lengths
Absorption spectra and cyclovoltammetric peak po-
tentials of a few complexes have been recorded in
dichloromethane and are summarized in Table 3. The
long-wavelength transitions of the complexes have their
origin in the electron-rich selenolate groups, the un-
occupied target orbital is typically associated with the
metal [8]. Very weak features of the triorganophosphine-
containing compounds have been attributed to seleno-
late-to-phosphine charge transfer transitions [7,8]. Ag-
gregation, and thereby increased orbital interaction,
shifts these transitions to lower energies as is evident
from a comparison between dimeric 1a and presumably
Pd(1)Ã
Pd(1)Ã
Pd(2)Ã
Pd(2)Ã
Pd(1)Ã
/
Se(1)
Se(2)
Se(1)
Se(2)
Cl(1)
2.3858(7)
2.4037(7)
2.3954(9)
2.3965(7)
Pd(2)Ã
Pd(1)Ã
Pd(2)Ã
Se(1)Ã
/
Cl(2)
N(1)
N(2)
2.3445(14)
2.148(4)
2.141(4)
1.973(5)
1.981(6)
/
/
/
/
/
/
C(1)
C(6)
/
2.3677(15) Se(2)Ã
/
Bond angles
Se(1)ÃPd(1)Ã
Se(1)ÃPd(1)Ã
Se(1)ÃPd(1)Ã
Se(2)ÃPd(1)Ã
Se(2)ÃPd(1)Ã
N(1)ÃPd(1)Ã
Pd(1)ÃSe(1)Ã
/
/
Se(2)
Cl(1)
N(1)
N(1)
Cl(1)
79.67(2)
171.22(4)
Se(1)Ã
/
Pd(2)Ã
Pd(2)Ã
Pd(2)Ã
Pd(2)Ã
Pd(2)Ã
Pd(2)Ã
Pd(1)ÃSe(2)Ã
/
Se(2)
Cl(2)
N(2)
N(2)
Cl(2)
Cl(2)
79.62(3)
170.84(4)
95.56(12)
174.31(11)
91.35(4)
/
/
Se(2)Ã
/
/
/
/
94.78(12) Se(2)Ã
172.49(12) Se(1)Ã
91.98(4)
Se(1)Ã
93.29(13) N(2)Ã
91.11(3)
/
/
/
/
/
/
/
/
/
/
/
/
Cl(1)
/
/
93.37(12)
90.64(3)
/
/Pd(2)
/
/Pd(2)
Fig. 1. View of [PdCl(SeCH2CH2CH2NMe2)]2 (1a) with crystallographic numbering scheme.

110
S. Dey et al. / Inorganica Chimica Acta 349 (2003) 104ꢁ110
/
(d) J.R. Dilworth, N. Wheatley, Coord. Chem. Rev. 119 (2000)
89;
tion. The PdÁ Á ÁPd separation is considerably greater
than that of thiolato-bridged analogues (3.144(2)ꢁ
/
3.374
25]) due to the larger size of bridging
(e) J. Real, M. Pages, A. Polo, J.F. Pinella, A. Alvarez-Larena,
Chem. Commun. (1999) 277;
˚
(1) A [23ꢁ
/
selenium. An even smaller PdÁ Á ÁPd separation of
(f) V.K. Jain, G.S. Rao, Inorg. Chiem. Acta 127 (1987) 161.
[3] S. Narayan, V.K. Jain, K. Panneerselvam, T.H. Lu, S.F. Tung,
Polyhedron 18 (1999) 1253.
˚
2.9726 (7) A was found in the related (and isostructural)
phosphinothiolato complex [PdCl(SCH2CH2-
[4] A. Singhal, V.K. Jain, R. Misra, B. Varghese, J. Mater. Chem.
(2000) 1121.
CH2PPh2)]2 [33]. Like in the latter compound, the six-
membered chelate rings (‘PdSeCCCN’ in 1a) are puck-
ered in a boat-type conformation while the four-
membered ‘Pd2Se2’ ring is non-planar with a hinge
[5] S. Dey, V.K. Jain, S. Chaudhury, A. Knoedler, F. Lissner, W.
Kaim, J. Chem. Soc., Dalton Trans. (2001) 723.
[6] (a) Y. Tonomura, J. Handa, Mitsubishi Paper Mills Ltd., Jpn Pat
(1991) 03126035 (Chem. Abst. 115 (1991) 218921);
(b) T. Oota, K. Yoshioka, T. Akyama, S. Mori, Jap. Pat. (1995)
7205548 (Chem. Abst. 123 (1995) 325855).
angle of 136.28, showing an anti configuration. The PdÃ
/
Se distances trans to N and trans to Cl are essentially
similar and are well within the range expected for
chelated selenolate ligands in palladium [5,8] and
[7] S. Dey, V.K. Jain, A. Knoedler, W. Kaim, S. Zalis, Eur. J. Inorg.
Chem. (2001) 2965.
analogous platinum complexes [7]. Also, the PdÃ
and PdÃN distances are well within the ranges reported
for similar derivatives [5,7,8]. The former is longer by
/Cl
[8] S. Dey, V.K. Jain, A. Knodler, A. Klein, W. Kaim, S. Zalis,
Inorg. Chem. 41 (2002) 2864.
/
[9] S. Narayan, V.K. Jain, B. Varghese, J. Chem. Soc., Dalton Trans.
(1998) 2359.
˚
˚
about 0.14 A while the latter is shorter by 0.07 A relative
to the values reported for the sulfur analogue
[10] S. Dey, V.K. Jain, J. Singh, V. Trehan, K.K. Bhasin, B. Varghese,
unpublished results.
[11] C.W. Schlapfer, K. Nakamoto, Inorg. Chiem. Acta 6 (1972) 177.
¨
[PdCl(SCH2CH2CH2NMe2)]2 [24]. The SeÃ
/
PdÃ
/
Se angle
is small and, in consequence, the other right angles have
[12] D. Gibson, S.J. Lippard, Inorg. Chem. 25 (1986) 219.
[13] I. Casals, P. Gonzalez-Duarte, W. Clegg, C. Foces-Foces, F.H.
Cano, M. Martinez-Ripoll, M. Gomez, X. Solans, J. Chem. Soc.,
Dalton Trans. (1991) 2511.
opened up to 95.56(12)8.
In summary, the chemistry of the 3-dimethylamino-
propylselenolate ligand differs considerably from that of
its lower homologue Me2NCH2CH2Seꢂ. The g-amino-
selenolate ligand can bind palladium and platinum as a
[14] M. Capdevila, W. Clegg, P. Gonzalez-Duarte, I. Mira, J. Chem.
Soc., Dalton Trans. (1992) 173.
[15] S. Marchal, V. Moreno, G. Aullon, S. Alvarez, M. Quiros, M.
Font-Bardia, X. Solans, Polyhedron 18 (1999) 3675.
[16] D.C. Jicha, D.H. Busch, Inorg. Chem. 1 (1962) 872.
[17] J. Suades, X. Solans, M. Font-Altaba, Polyhedron 3 (1984) 1227.
[18] M. Capdevila, P. Gonzalez-Duarte, C. Foces-Foces, F.H. Cano,
M. Martinez-Ripoll, J. Chem. Soc., Dalton Trans. (1990) 143.
[19] M. Capdevila, P. Gonzalez-Duarte, J. Sola, C. Foces-Foces, F.H.
Cano, M. Martinez-Ripoll, Polyhedron 8 (1989) 1253.
[20] H. Barrera, J.C. Bayon, J. Suades, C. Germain, J.P. Declerq,
Polyhedron 3 (1984) 969.
simple selenolate or as metalÃ
/
metal bridging selenolate,
in N,Se-chelating or chelating-bridging modes.
4. Supplementary material
The material is available from the authors on request.
[21] M. Capdevila, W. Clegg, P. Gonzalez-Duarte, B. Harris, I. Mira,
J. Sola, I.C. Taylor, J. Chem. Soc., Dalton Trans. (1992) 2817.
[22] J. Sola, R. Yanez, J. Chem. Soc., Dalton Trans. (1986) 2021.
[23] H. Barrera, J.M. Vinas, M. Font-Altaba, X. Solans, Polyhedron 4
(1985) 2027.
Acknowledgements
We thank Drs. J.P. Mittal and P. Raj for encourage-
ment of this work and Dr. Axel Klein for helpful
discussions. We are also grateful to Dr. M. Sudersha-
nan, Head, Analytical Chemistry Division, BARC for
providing microanalyses of complexes. Support for this
work under the Indo-German Bilateral Program from
the BMBF (Project No. IND 99/060) is gratefully
acknowledged.
[24] X. Solans, M. Font-Altaba, J.L. Brianso, J. Sola, J. Suades, H.
Barrera, Acta Crystallogr., C 39 (1983) 1653.
[25] J.A. Ayllon, P. Gonzalez-Duarte, C. Miravitlles, E. Molins, J.
Chem. Soc., Dalton Trans. (1990) 1793.
[26] F.R. Hartley, The Chemistry of Platinum and Palladium, Wiley,
New York, 1973.
[27] SHELXTL-5.1, Bruker Analytical X-ray Systems, Madison, WI,
1998.
[28] S. Dey, V.K. Jain, A. Klein, W. Kaim, unpublished results.
[29] A. Singhal, V.K. Jain, B. Varghese, E.R.T. Tiekink, Inorg. Chim.
Acta 285 (1999) 190.
[30] V.K. Jain, S. Kannan, E.R.T. Tiekink, J. Chem. Res. (M) (1994)
501.
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