Multiple coordination modes of hemilabile 3-dimethylaminopropyl chalcogenolates in platinum(II) complexes: Synthesis, spectroscopy and structures

Article abstract of DOI:10.1016/j.ica.2007.01.002

The reactions of N,N-dimethylaminopropyl chalcogenolates with platinum(II) compounds have been carried out and complexes of the types [PtCl(ECH₂CH₂CH₂NMe₂)]₂ (1) (E = S (1a) and Se (1b)), [Pt(ECH₂CH₂CH₂NMe₂)₂]_n (2) (E = S (2a) and Se (2b)), [(PtCl₂)₂{(Me₂NCH₂CH₂CH₂E)₂}]_n (3), [PtX(SeCH₂CH₂CH₂NMe₂)]₂ (4) (X = SePh (4a) and OAc (4b)) and [PtCl(ECH₂CH₂CH₂NMe₂)(PR₃)]_n (5) (E = S, Se, Te) have been isolated. These complexes have been characterized by elemental analysis, IR, UV-Vis, NMR (¹H, ¹³C, ³¹P, ⁷⁷Se, ¹⁹⁵Pt) spectroscopy and FAB mass spectral data. The structures of [PtCl(SeCH₂CH₂CH₂NMe₂)]₂ (1b) and [PtCl(SCH₂CH₂CH₂NMe₂)(PPr₃)]₂ (5a) have been established by single crystal X-ray diffraction data. Both the molecules have dimeric structures. In 1b, two platinum atoms are held together by symmetrically bridging Se atoms of the chelating selenolate groups. In 5a, two thiolates form a four-membered Pt₂S₂ bridge with dangling NMe₂ groups.

Full text of DOI:10.1016/j.ica.2007.01.002

Inorganica Chimica Acta 360 (2007) 2653–2660
www.elsevier.com/locate/ica
Multiple coordination modes of hemilabile 3-dimethylaminopropyl
chalcogenolates in platinum(II) complexes: Synthesis, spectroscopy
and structures
a
a,
b
Sandip Dey , Vimal K. Jain *, Ray J. Butcher
a
Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400 085, India
Department of Chemistry, Howard University, Washington, DC 20059, USA
b
Received 28 August 2006; accepted 3 January 2007
Available online 13 January 2007
Abstract
The reactions of N,N-dimethylaminopropyl chalcogenolates with platinum(II) compounds have been carried out and complexes of
the types [PtCl(ECH2CH2CH2NMe2)]2 (1) (E = S (1a) and Se (1b)), [Pt(ECH2CH2CH2NMe2)2]n (2) (E = S (2a) and Se (2b)),
[(PtCl2)2{(Me2NCH2CH2CH2E)2}]n (3), [PtX(SeCH2CH2CH2NMe2)]2 (4) (X = SePh (4a) and OAc (4b)) and [PtCl(ECH2CH2CH2N-
Me2)(PR3)]n (5) (E = S, Se, Te) have been isolated. These complexes have been characterized by elemental analysis, IR, UV–Vis,
NMR (1H, 13C, 31P, 77Se, 195Pt) spectroscopy and FAB mass spectral data. The structures of [PtCl(SeCH2CH2CH2NMe2)]2 (1b) and
[PtCl(SCH2CH2CH2NMe2)(PPr3)]2 (5a) have been established by single crystal X-ray diffraction data. Both the molecules have dimeric
structures. In 1b, two platinum atoms are held together by symmetrically bridging Se atoms of the chelating selenolate groups. In 5a, two
thiolates form a four-membered Pt2S2 bridge with dangling NMe2 groups.
ꢀ 2007 Elsevier B.V. All rights reserved.
Keywords: Chalcogenolate; N ligands; Platinum(II); NMR; X-ray crystal structure
1. Introduction
chalcogenolates, Me2NCH2CH2CH2Eꢀ (E = S, Se, Te), of
palladium and have shown the diverse coordination possi-
bilities of the ligand [19–21]. Only a few examples of
platinum complexes with N,N0-dimethylaminopropyl sel-
enolates are reported [19]. To assess the trend with the var-
iation in chalcogen ligand in platinum complexes, we have
prepared several platinum(II) complexes with Me2NCH2-
CH2CH2Eꢀ (E = S, Se, Te) and compared their chemistry
with palladium derivatives.
The chemistry of aminochalcogenolate ligands, R2N-
ðCR02ÞnEꢀ, has been a subject area of considerable research
for over the last two decades and has been dominated by
thiolate derivatives [1–15]. The complexes containing hea-
vier analogs (Se or Te) have been studied only recently
[16–21]. These ligands show versatile coordination chemis-
try as internal functionalization through N donor provides
a way to suppress polymerization of metal chalcogenolates,
whereas their hemilability makes them superior catalysts
[22,23]. The structures of aminoalkylchalcogenolate metal
complexes are greatly influenced by the nature of the metal
ion, the number of intervening atoms separating the N and
E centers and the substituents on the N atom. Recently we
have examined the chemistry of N,N-dimethylaminopropyl
2. Experimental
The solvents were dried and distilled under a nitrogen
atmosphere prior to use. All reactions were carried out in
a Schlenk flask under a nitrogen atmosphere. Tellurium
and Me2NCH2CH2CH2Cl Æ HCl were obtained from com-
mercial sources. Dichalcogenides (Me2NCH2CH2CH2E)2
(E = S [21,24], Se [19] and Te [21]) were prepared according
to the literature methods. Elemental analyses were carried
*
Corresponding author.
E-mail address: jainvk@barc.gov.in (V.K. Jain).
0020-1693/$ - see front matter ꢀ 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2007.01.002

2654
S. Dey et al. / Inorganica Chimica Acta 360 (2007) 2653–2660
out by the Radio Chemistry Division of BARC. Melting
points were determined in capillary tubes and are uncor-
rected. 1H, 13C{1H}, 77Se{1H} and 195Pt{1H} NMR spectra
were recorded on a Bruker DPX-300 NMR spectrometer
operating at 300, 75.47, 57.24 and 64.52 MHz, respectively.
Chemical shifts are relative to internal chloroform peak at d
17.2; H, 3.5; N, 4.0. Found: C, 17.1; H, 3.7; N, 4.0%.
UV–Vis (CH2Cl2) kmax: 288 (2230), 318 (sh), 366 (440)
1
nm. IR mPt–Cl: 280 cmꢀ1. H NMR in CDCl3 d: 1.98–2.13
(m); 2.38–2.43 (m); 2.66–2.74 (m), 2.81 (s, J(Pt–H) =
19 Hz), 2.89 (s, J(Pt–H) = 26 Hz), 3.26–3.32 (m). 13C{1H}
2
NMR in CDCl3 d: 25.6 (s, SCH2–, J(195Pt–13C) 40 Hz);
1
7.26 ppm for H and d 77.0 ppm for 13C{1H}, Me2Se for
27.1 (s, –CH2–); 51.4, 52.8 (each s, NMe2); 63.0 (s,
NCH2–). 195Pt{1H} NMR in CDCl3 d: ꢀ2862 (s). Cyclic
voltammetry (CH2Cl2): Epa (ox) 0.94; Epc (red) ꢀ2.46.
77Se{1H} and Na2PtCl6 for 195Pt{1H}. A 90ꢁ pulse was used
in every case. A weighting function was applied in 13C{1H},
77Se{1H} and 195Pt{1H} NMR spectra. The IR spectra were
recorded as Nujol mulls between CsI plates on a Bomen
MB-102 FT-IR spectrometer. UV–Vis absorption spectra
were recorded on a Chemito Spectrascan UV 2600 dou-
ble-beam UV–Vis spectrophotometer using quartz cuvettes
with a diameter of 1 cm. Cyclic voltammetry was carried
out at a scan rate of 100 mV sꢀ1 in CH2Cl2/0.1 M
Bu4NPF6, using a three-electrode configuration (glassy car-
bon electrode, platinum counter electrode, calomel refer-
ence electrode) and an Ecochemie potentiostat 100 with
autolab software. The ferrocene/ferrocenium couple served
as the external reference. FAB mass spectra were recorded
on a JEOL SX 102/DA-6000 mass spectrometer at CDRI,
Lucknow, India.
2.1.3. Preparation of [Pt(SCH2CH2CH2NMe2)2]n (2a)
To a freshly prepared methanolic solution (8 cm3) of
NaSCH2CH2CH2NMe2 (prepared from (Me2NCH2CH2-
CH2S)2 (271 mg, 1.15 mmol) and NaBH4 (88 mg,
2.32 mmol)), an aqueous solution (8 cm3) of K2PtCl4
(473 mg, 1.14 mmol) and acetone (10 cm3) was added with
vigorous stirring which continued for 4 h. The solvents
were evaporated under reduced pressure. The residue was
washed with hexane and extracted with acetone
(3 · 20 cm3). The yellow solution was filtered, passed
through a Florisil column and concentrated to 5 cm3 under
vacuum, and after cooling at ꢀ5 ꢁC for 24 h gave a yellow
powder in 28% yield (138 mg). M.p. 208 ꢁC (dec). Anal.
Calc. for C10H24N2PtS2: C, 27.8; H, 5.6; N, 6.5; S, 14.9.
2.1. Synthesis
Found: C, 27.0; H, 5.8; N, 6.6; S, 14.0%. UV–Vis (CH2Cl2)
1
k
max: 284 (10200), 300 (9800), 380 (sh) nm. H NMR in
2.1.1. Preparation of [PtCl(SeCH2CH2CH2NMe2)]2 (1b)
To a methanolic solution of NaSeCH2CH2CH2NMe2
(prepared from (Me2NCH2CH2CH2Se)2 (202 mg, 0.61
mmol) and NaBH4 (47 mg, 1.24 mmol) in 15 cm3 metha-
nol), an aqueous solution of K2PtCl4 (507 mg, 1.22 mmol)
was added with vigorous stirring which continued for 3 h.
The solvents were stripped off in vacuo and the residue
was washed with hexane and acetone. The residue was
extracted with dichloromethane (3 · 15 cm3), filtered
through a G-3 filter and the filtrate was passed through a
Florisil column. The yellow solution was concentrated to
5 cm3 and acetone–hexane mixture was added to yield a yel-
low powder (yield 213 mg, 44%), m.p. >195 ꢁC (dec). Anal.
Calc. for C10H24Cl2N2Pt2Se2: C, 15.2; H, 3.1; N, 3.5.
CDCl3 d: 2.28 (s, NMe2); 2.34 (br); 2.45 (br), 2.53 (br)
(–CH2–CH2–CH2–). 13C{1H} NMR in CDCl3 d: 31.5 (s,
SCH2); 32.2 (s, –CH2–); 45.4 (s, NMe2); 58.7 (s, NCH2–).
Cyclic voltammetry (CH2Cl2): Epc (red) ꢀ1.76.
2.1.4. Preparation of [Pt(SeCH2CH2CH2NMe2)2]n (2b)
To a freshly prepared methanolic solution (10 cm3) of
NaSeCH2CH2CH2NMe2 (prepared from (Me2NCH2CH2-
CH2Se)2 (348 mg, 1.05 mmol) and NaBH4 (81 mg,
2.14 mmol) in methanol), a dichloromethane solution
(20 cm3) of PtCl2(PhCN)2 (493 mg, 1.04 mmol) was added
with vigorous stirring which continued for 4 h whereupon
an orange precipitate formed. The solvents were evapo-
rated under reduced pressure and the residue was washed
with hexane and ether. The residue was extracted with
hot dichloromethane (3 · 20 cm3) and filtered. The filtrate
was concentrated to 5 cm3 and hexane was added to give
an orange powder (153 mg, 28% yield). M.p. 205 ꢁC
(dec). Anal. Calc. for C10H24N2PtSe2: C, 22.9; H, 4.6; N,
Found: C, 15.1; H, 3.4; N, 3.5%. UV–Vis (CH2Cl2) kmax
:
260 (sh), 303 (3820), 331 (2320), 380 (sh). IR mPt–Cl
:
1
280 cmꢀ1. H NMR in CDCl3 d: 1.86–1.99 (m); 2.06–2.14
(m); 2.50–2.75 (m), 2.78 (s), 2.83 (s) (NMe2); 3.00–3.09
(m). 13C{1H} NMR in CDCl3 d: 19.4 (s, –CH2–); 27.1 (s,
2
1
SeCH2, J(195Pt–13C) 56 Hz); 50.3, 53.6 (each s, NMe2);
5.3. Found: C, 22.0; H, 4.1; N, 4.9%. H NMR in CDCl3
65.3 (s, NCH2). 77Se{1H} NMR in CDCl3 d: ꢀ109
(1J(195Pt–77Se) = 364 Hz). 195Pt{1H} NMR in CDCl3 d:
ꢀ3209. FAB-MS m/z: 791 [M], 755 [MꢀCl], 719
[Mꢀ(CH2CH2NMe2)], 670 [Mꢀ(Cl+CH2CH2CH2NMe2)].
Cyclic voltammetry (CH2Cl2): Epa (ox) 1.10; Epc (red)
ꢀ2.36.
d: 2.22 (s, NMe2); 2.32–2.38 (br, –CH2–CH2–CH2–).
13C{1H} NMR in CDCl3 d: 25.5 (s, SeCH2); 32.1 (s,
–CH2–); 45.5 (s, NMe2); 59.6 (s, NCH2–).
2.1.5. Reaction of (Me2NCH2CH2CH2S)2 with K2PtCl4
(3a)
To a methanolic solution (15 cm3) of (Me2NCH2CH2-
CH2S)2 (152 mg, 0.64 mmol), an aqueous solution
(10 cm3) of K2PtCl4 (530 mg, 1.28 mmol) was added with
stirring which continued for 4 h, whereupon a pale yellow
precipitate formed. The precipitate was filtered through a
2.1.2. Preparation of [PtCl(SCH2CH2CH2NMe2)]2 (1a)
Prepared similarly to 1b from K2PtCl4 and NaSCH2-
CH2CH2NMe2 in 32% yield as a yellow crystalline solid.
M.p. >200 ꢁC (dec). Anal. Calc. for C10H24Cl2N2Pt2S2: C,

S. Dey et al. / Inorganica Chimica Acta 360 (2007) 2653–2660
2655
G-3 filter, washed thoroughly with H2O, followed by meth-
anol and acetone, and finally dried under vacuum (yield
317 mg, 65%). M.p. 210 ꢁC (dec). Anal. Calc. for
C10H24Cl4N2Pt2S2: C, 15.6; H, 3.2; N, 3.6; S, 8.3. Found:
C, 13.7; H, 3.0; N, 3.2; S, 10.5%.
Similarly Se (3b) [m.p. 188 ꢁC (dec). Anal. Calc. for
C10H24Cl4N2Pt2Se2: C, 13.9; H, 2.8; N, 3.2. Found: C,
12.6; H, 2.8; N, 3.5%] and Te (3c) [m.p. 158 ꢁC (dec). Anal.
Calc. for C10H24Cl4N2Pt2Te2: C, 12.5; H, 2.5; N, 2.9.
Found: C, 11.1; H, 2.3; N, 2.5%] derivatives were prepared.
in vacuo, the residue was washed with hexane and
extracted with acetone (3 · 5 cm3). The solution was con-
centrated to 5 cm3, few drops of hexane were added to yield
(120 mg, 56%) an yellow oil. Anal. Calc. for C28H66Cl2N2-
P2Pt2S2: C, 33.0; H, 6.5; N, 2.8; S, 6.3. Found: C, 32.2; H,
1
6.4; N, 3.0; S, 6.4%. H NMR in CDCl3 d: 1.02 (br, P–C–
CCH3); 1.57 (br, PC–CH2–); 1.79 (br, PCH2); 2.20, 2.37
(each s, NMe2); 2.28–2.83 (br, m, –CH2CH2CH2–).
1
31P{1H} NMR in CDCl3 d: 1.1, J(195Pt–31P) = 3184 Hz.
195Pt{1H} NMR in CDCl3 d: ꢀ3802 (d, 1J(195Pt–31P) =
3206 Hz). Cyclic voltammetry (CH2Cl2): Epc (red) ꢀ0.81,
ꢀ2.37.
2.1.6. Preparation of [Pt(SePh)(SeCH2CH2CH2NMe2)]2
(4a)
To a methanolic solution (10 cm3) of NaSePh (prepared
from Ph2Se2 (80 mg, 0.26 mmol) and NaBH4 (20 mg,
0.53 mmol) in methanol), a dichloromethane solution
(20 cm3) of [PtCl(SeCH2CH2CH2NMe2)]2 (200 mg,
0.25 mmol) was added with stirring. The color changed
immediately to orange. After 3 h of stirring, the solvents
were evaporated in vacuo, and the residue was extracted
with toluene (3 · 15 cm3) and filtered. The filtrate was con-
centrated under vacuum to 5 cm3. To this a mixture of ace-
tone and hexane was added whereupon an orange powder
separated (98 mg, 38% yield). M.p. >190 ꢁC (dec). Anal.
Calc. for C22H34N2Pt2Se4: C, 25.6; H, 3.3; N, 2.7. Found:
C, 24.9; H, 3.1; N, 3.0%. UV–Vis (CH2Cl2) kmax: 354 nm.
1H NMR in CDCl3 d: 2.09 (s, with a very broad base)
(SeCH2CH2CH2); 7.11 (br), 7.85 (br) (Ph). 13C{1H}
NMR in CDCl3 d: 24.5 (br, –CH2–); 31.6 (br, SeCH2);
45.4 (s, NMe2), 59.3 (each s, NCH2); 123.2 (br); 134.9
(br, Ph).
2.1.9. Preparation of [PtCl(SeCH2CH2CH2NMe2)-
(PPr3)]2 (5b)
Compound 5b prepared according to the literature
method [19]. 1H NMR in CDCl3: 1.05 (t, 7 Hz,
PCH2CH2Me); 1.56–1.85 (m, PCH2CH2, NCH2); 2.24(s,
NMe2); 2.45 (br, NCH2); 2.62 (br, m, SeCH2). 31P{1H}
NMR in CDCl3: ꢀ0.1, 1J(Pt–P) = 3122 Hz. 195Pt{1H}
1
NMR in CDCl3: ꢀ3960 (d), J(Pt–P) = 3097 Hz.
2.1.10. Preparation of [PtCl(TeCH2CH2CH2NMe2)-
(PEt3)]2 (5c1)
To a freshly prepared methanolic solution of NaTe-
CH2CH2CH2NMe2 (prepared from (Me2NCH2CH2CH2-
Te)2 (100 mg, 0.23 mmol) and NaBH4 (18 mg, 0.48 mmol)),
an acetone suspension of [Pt2Cl2(l-Cl)2(PEt3)2] (179 mg,
0.23 mmol) was added with stirring which continued for
4 h at room temperature. The solvents were evaporated
under vacuum. The residue was extracted with hexane
(3 · 8 cm3) followed by acetone (3 · 8 cm3). The extracts
were separately dried under vacuum and studied by
NMR spectroscopy.
2.1.7. Preparation of [Pt(OAc)(SeCH2CH2CH2NMe2)]2
(4b)
To a dichloromethane solution (20 cm3) of [PtCl-
(SeCH2CH2CH2NMe2)]2 (170 mg, 0.21 mmol), a methan-
olic suspension (5 cm3) of AgOAc (72 mg, 0.43 mmol)
was added with vigorous stirring which was continued
for 6 h. This was centrifuged to remove AgCl and then fil-
tered through a G-3 funnel. The filtrate was dried under
vacuum and the yellowish green solid was recrystallized
from CH2Cl2–acetone mixture in 45% (81 mg) yield. M.p.
>172 ꢁC (dec). Anal. Calc. for C14H30N2O4Pt2Se2: C,
Hexane soluble part: H NMR in CDCl3: 1.09–1.25 (m,
1
PCH2Me); 1.78–2.14 (m, PCH2); 2.18 (s, minor); 2.20 (d,
3.8 Hz, NMe2, major); 2.23–2.43 (m); 2.63–2.65 (m).
1
1
31P{1H}: 4.6 (s, J(Pt–P) = 3030 Hz, minor); 7.5 (s, J(Pt–
P) = 3046 Hz, major) (other small peaks were also present).
Anal. Calc. for C22H54Cl2N2P2Pt2Te2: C, 23.5; H, 4.8; N,
2.5%.
Acetone fraction contained mainly ꢁ90% cis-[PtCl2-
(PEt3)2], 31P{1H} NMR: 9.8 (1J(Pt–P) = 3492 Hz);
1
1
20.1; H, 3.6; N, 3.3. Found: C, 19.4; H, 3.3; N, 3.6%. H
195Pt{1H} NMR: ꢀ4475 (t, J(Pt–P) = 3496 Hz). 31P{1H}
NMR in CDCl3 d: 1.99 (s, OAc); 2.66, 2.83 (each s,
NMe2); 2.31 (br); 2.60 (br, m); 3.10 (m) (CH2–). 13C{1H}
NMR in CDCl3 d: 17.6 (s, OAc); 23.6 (s, CH2); 27.5 (s,
SeCH2), 50.8, 53.0 (each s, NMe2); 65.4 (s, NCH2); 177.3
(CO).
NMR: 8.1 (1J(Pt–P) = 3054 Hz); 195Pt{1H} NMR: ꢀ4735
1
(d, J(Pt–P) = 3065 Hz) (minor).
2.1.11. Preparation of [PtCl(TeCH2CH2CH2NMe2)-
(PMePh2)]2 (5c2)
To a methanolic solution of NaTeCH2CH2CH2NMe2
(prepared from (Me2NCH2CH2CH2Te)2 (78 mg, 0.18
mmol) and NaBH4 (15 mg, 0.40 mmol) in methanol) was
added an acetone suspension (15 cm3) of [Pt2Cl2(l-Cl)2-
(PMePh2)2] (167 mg, 0.18 mmol) with vigorous stirring
which continued for 4 h. The solvents were removed in
vacuo. The residue was washed with hexane (2 cm3) and
extracted with acetone (3 · 8 cm3) and filtered. The filtrate
2.1.8. Preparation of [PtCl(SCH2CH2CH2NMe2)-
(PPr3)]2 (5a)
To a dichloromethane solution (20 cm3) of [Pt2Cl2-
(l-Cl)2(PPr3)2] (180 mg, 0.21 mmol), a methanolic solution
of NaSCH2CH2CH2NMe2 (prepared from (Me2NCH2-
CH2CH2S)2 (50 mg, 0.21 mmol) and NaBH4 (16 mg,
0.42 mmol)) stirred for 3 h. The solvents were stripped off

2656
S. Dey et al. / Inorganica Chimica Acta 360 (2007) 2653–2660
Table 1
anisotropically. Selected crystallographic data are given in
Table 1.
Crystallographic and structure refinement data for 1b and 5a
Compound
1b
5a
3. Results and discussion
Chemical formula
Formula weight
Crystal size (mm)
Temperature (K)
C10H24Cl2N2Pt2Se2
791.32
0.71 · 0.33 · 0.18
103(2)
C28H66Cl2N2P2Pt2S2
1017.96
0.28 · 0.24 · 0.10
103(2)
3.1. Synthesis and NMR spectroscopic data
˚
k (A)
0.71073
0.71073
The reactions of NaECH2CH2CH2NMe2 with K2PtCl4
in 1:1 and 2:1 stoichiometry gave yellow-orange complexes
of compositions [PtCl(ECH2CH2CH2NMe2)]2 (1) (E = S
(1a); Se (1b)) and [Pt(ECH2CH2CH2NMe2)2]n (2) (E = S
(2a); Se (2b)), respectively, as a sparingly soluble powder.
Similar reactions with NaTeCH2CH2CH2NMe2, however,
gave brown insoluble solid which was not characterized
further. The reaction of Na2PdCl4 with (Me2NCH2CH2-
CH2E)2 in methanol affords dimeric [PdCl(ECH2CH2CH2-
NMe2)]2, which has been unambiguously characterized by
X-ray crystallography [18,20]. The reaction of K2PtCl4
with (Me2NCH2CH2CH2Se)2 gave an insoluble complex
which was thought to be [PtCl(SeCH2CH2CH2NMe2)]2
(1b), although microanalytical data were slightly different
from the expected composition [18]. When this reaction
was extended to other dichalcogenides (E = S or Te), insol-
uble products were formed which gave microanalysis
slightly lower than that expected for 1. The analytical data
are, however, closer to the composition, [Pt2Cl4{(Me2-
NCH2CH2CH2E)2}] (3). These complexes are soluble in
coordinating solvents, like DMSO and pyridine, with
which they react. The 195Pt{1H} NMR spectra of DMSO
solutions of 3a and 3b exhibited major signals due to the
cis and trans [PtCl2(DMSO)2] (d ꢀ2964, ꢀ3455 ppm) and
several small peaks in the regions ꢀ2858, ꢀ2900, ꢀ3250
and ꢀ3500 (3a); ꢀ3600 and ꢀ3800 ppm (3b), respectively.
The peaks at ꢀ2858 (in 3a) and ꢀ3193 (in 3b) ppm may
be due to 1a and 1b and the slight difference in chemical
shift may be due to solvent effects. A similar 195Pt{1H}
NMR spectrum was observed when a DMSO solution of
[PtCl2(DMSO)2] was treated with (Me2NCH2CH2CH2Se)2.
These complexes also dissolved readily in pyridine to give
deep colored solutions from which a colorless product
was isolated. This colorless product has been characterized
as [PtCl(py)3]Cl (m.p. >260 (d)) from microanalysis (Anal.
Calc.: C, 35.8; H, 3.0; N, 8.3. Found: C, 37.6; H, 3.7; N,
Crystal system
Space group
Unit cell dimensions
monoclinic
P21/n
monoclinic
C2/c
˚
a (A)
10.3406(19)
8.6477(15)
19.141(3)
97.809(2)
1695.7(5)
3.100
21.896(3)
11.5656(14)
15.9619(19)
106.588(2)
3874.0(8)
1.745
˚
b (A)
˚
c (A)
b (ꢁ)
3
˚
V (A )
Dcalc (g cmꢀ3
)
Z
8
8
l (mmꢀ1)/F(000)
h Range for data
collection (ꢁ)
21.075/1424
2.13–28.27
7.563/2000
1.94–30.87
Limiting indices
ꢀ11 6 h 6 13,
ꢀ11 6 k 6 11,
ꢀ25 6 l 6 25
ꢀ31 6 h 6 28,
ꢀ16 6 k 6 15,
ꢀ22 6 l 6 22
1.123
Goodness-of-fit on F2 1.064
Absorption correction SADABS
Reflections collected/
unique
Data/restraints/
parameters
SADABS
16000/4161
20802/5532
4161/6/167
5532/0/177
Final R1, wR2 indices 0.0413, 0.1119
0.0573, 0.1199
0.0708, 0.1269
5.895 and ꢀ4.797
R1, wR2 (all data)
Largest difference in
peak and hole
0.0451, 0.1142
3.569 and ꢀ3.723
ꢀ3
˚
(e A
)
Computer programs
used
SHELXTL-5.1 [31]
SHELXTL-5.1 [31]
was concentrated to 5 cm3 and hexane (1 cm3) was added
and cooled at ꢀ5 ꢁC for 24 h whereupon pale yellow crys-
tals separated (yield: 111 mg, 48%) (m.p. 172 ꢁC). Anal.
Calc. for C36H50Cl2N2P2Pt2Te2: C, 33.5; H, 3.9; N, 2.2.
1
Found: C, 33.9; H, 3.9; N, 2.1%. H NMR in CDCl3: 2.15
(d, 11 Hz, PMe2); 2.03, 2.17, 2.26 (each s); 1.82–2.34
(broad+multiplets); 7.28–7.71 (m, Ph). 31P{1H} NMR: 0.1
(s, 1J(Pt–P) = 3110 Hz), ꢀ0.9 (s, 1J(Pt–P) = 3075 Hz) (each
1:1); ꢀ1.7 (s, 1J(Pt–P) = 3100 Hz, small). 195Pt{1H} NMR:
ꢀ4754 (d, 1J(Pt–P) = 3129 Hz), ꢀ4809 (d, 1J(Pt–P) =
3084 Hz) (each 1:1); ꢀ4789 (d, 1J(Pt–P) = 3058 Hz, minor)
1
8.8%.) and H NMR spectra. From these data it appears
that these complexes 3 contain dichalcogenide ligand coor-
1
ppm. cis-[PtCl2(PMePh2)2] ꢀ0.2; J(Pt–P) = 3614 Hz.
dinated to platinum through chalcogen/nitrogen donors.
2.2. X-ray crystallography
x = 1
[PtCl(ECH2CH2CH2NMe2)]2 (1)
(E = S (1a), Se (1b))
The unit cell parameters and the intensity data for yel-
low single crystals of [PtCl(SeCH2CH2CH2NMe2)]2 (1b)
and [PtCl(SCH2CH2CH2NMe2)(PPr3)]2 (5a) were collected
at ꢀ170 ꢁC on a Bruker Smart 1K CCD diffractometer
using graphite-monochromated Mo Ka radiation (k =
K2PtCl4 + x NaECH2CH2CH2NMe2
x = 2
[Pt(ECH2CH2CH2NMe2)2]n (2)
(E = S (2a), Se (2b))
The FAB mass spectrum of 1b displayed a multiplet at
1
˚
0.71073 A), employing the x scan technique. The intensity
m/z 791 suggesting a dimeric formulation of 1. The H
and 13C{1H} NMR spectra of 1 displayed two signals for
the methyl groups of NMe2, suggesting that they are aniso-
chronous. The 13C{1H} signals for NCH2 and ECH2 in 1b
data were corrected for Lorentz, polarization and absorp-
tion effects [25]. The structure was solved and refined with
SHELX program [26]. The non-hydrogen atoms were refined

S. Dey et al. / Inorganica Chimica Acta 360 (2007) 2653–2660
2657
are deshielded as compared to the corresponding reso-
nances for 1a. The 195Pt{1H} spectra (Fig. 1) showed a sin-
gle resonance, suggesting that there is only one type of
platinum center. The 77Se{1H} NMR spectrum of 1b dis-
gesting that 4b may have binuclear selenolate bridged
structure similar to the palladium complex [21]. The H
NMR spectrum of 4a, however, showed broad resonances.
Treatment of [Pt2Cl2(l-Cl)2(PR3)2] with two equivalents
of NaECH2CH2CH2NMe2 gave complexes of the general
1
1
played a single resonance at ꢀ104 ppm with J(Pt–Se) of
1
364 Hz (Fig. 2). The J(Pt–Se) in platinum(II) selenolate
composition
[Pt2Cl2(l-ECH2CH2CH2NMe2)2(PR3)2],
complexes has been reported in the range of 100–385 Hz
[17,27]. The H NMR spectra of 2 showed multiplets for
which are formed as either cis (E = S; PR3 = PPr3) or a
mixture of cis and trans (E = Se or Te) isomers. The tellur-
olate derivatives tend to disproportionate slowly to
PtCl2(PR3)2 in solution and the latter could be isolated
by recrystallization. In contrast to the platinum complexes,
similar reactions of [Pd2Cl2(l-Cl)2(PR3)2] with NaS-
eCH2CH2CH2NMe2 gave a mixture of products from
which [PdCl(SeCH2CH2CH2NMe2)]2 was isolated [21].
The 1H NMR spectrum of 5a showed two NMe2 signals,
suggesting that the complex has sym-cis configuration. The
31P{1H} NMR spectra of 5a and 5b displayed a singlet with
platinum coupling. The magnitude of 1J(Pt–P) can be com-
pared with that of [Pt2Cl2(l-ER0)2(PR3)2] (E = S or Se),
therefore, a dimeric chalcogenolato-bridged structure may
be suggested (A and B; E = S or Se) (see later, X-ray crys-
tallography) [28,29]. The 31P spectra of 5c1, 5c2, however,
displayed three resonances. These resonances can be attrib-
uted for cis- (A, E = Te) and trans- (B, E = Te) isomers.
The third resonance can be assigned to a monomeric spe-
cies (C, E = Te) [PtCl(TeCH2CH2CH2NMe2)(PR3)]. The
195Pt{1H} NMR spectrum of [PtCl(TeCH2CH2CH2N-
Me2)(PMePh2)]n (5c2) (Fig. 3) also displayed three doublets
(d 195Pt = ꢀ4754; ꢀ4809; ꢀ4789 ppm) due to phosphorous
coupling. A small doublet at d ꢀ4789 ppm may be attrib-
uted to the monomeric species. The former two doublets
appearing in approximately 1:1 ratio may be assigned to
the cis and trans isomers. The 195Pt resonance gets shielded
1
CH2 proton resonances and a singlet for NMe2 protons.
The 13C{1H} NMR spectra displayed a single resonance
for the methylene and methyl carbons of chalcogenolate
groups.
The terminal chloride in 1b can be replaced with other
anionic ligands, viz., OAc, SePh. Thus the reaction of 1b
with NaSePh or AgOAc gave [Pt(SePh)(SeCH2CH2CH2N-
Me2)]n (4a) or [Pt(OAc)(SeCH2CH2CH2NMe2)]n (4b),
respectively. The NMR (1H and 13C) data of 4b can be
compared with [Pd(OAc)(SeCH2CH2CH2NMe2)]2, sug-
1
while J(Pt–P) decreases on increasing the size of the chal-
cogen atom, ꢀ3802 (cis, 5a, S, 1J(Pt–P) = 3206 Hz); ꢀ4065
(cis, 5b, Se, 1J(Pt–P) = 3155 Hz); ꢀ4735 (cis, 5c1, Te,
-3000
-3100
-3200
-3300
-3400
ppm
Fig. 1. 195Pt{1H} NMR spectrum of [PtCl(SeCH2CH2CH2NMe2)]2 in
CDCl3.
1
1J(Pt–P) = 3065 Hz). The decreasing magnitude of J(Pt–
P) with increasing size of chalcogen atom reflects their
increasing trans influence of the chalcogenolate ligand
[27]. This is manifested from facile disproportionation of
tellurolate derivative in solution.
NMe2
Pt
NMe2
Pt
PR3
Cl
Cl
Cl
Cl
E
E
E
E
E
PR3
Cl
Pt
Pt
Pt
PR3
PR3
PR3
N
NMe2
cis (A)
NMe2
trans (B)
Me2
monomeric (C)
(E∩N = Me2NCH2CH2CH2E; E = S, Se, Te)
3.2. Electronic spectra and electrochemistry
ppm
-200
-150
-100
Absorption spectra and cyclovoltammetric peak poten-
tials of a few complexes have been recorded in dichloro-
methane. These absorptions can be assigned as charge
Fig. 2. 77Se{1H} NMR spectrum of [PtCl(SeCH2CH2CH2NMe2)]2 in
CDCl3.

2658
S. Dey et al. / Inorganica Chimica Acta 360 (2007) 2653–2660
Table 2
Selected bond lengths (A) and angles (ꢁ) for [PtCl(SeCH2CH2CH2NMe2)]2
˚
(1b)
Pt(1)–Se(1)
Pt(1)–Se(2)
Pt(1)–Cl(1)
Pt(1)–N(2)
Se(1)–C(21)
N(2)–C(23)
2.3915(8)
2.3938(8)
2.3348(19)
2.134(6)
1.956(8)
1.499(10)
Pt(2)–Se(1)
Pt(2)–Se(2)
Pt(2)–Cl(2)
Pt(2)–N(1)
Se(2)–C(11)
N(1)–C(13)
2.3992(8)
2.3812(8)
2.3570(19)
2.136(6)
1.982(8)
1.490(10)
Se(1)–Pt(1)–Se(2)
N(2)–Pt(1)–Se(1)
Cl(1)–Pt(1)–Se(1)
N(2)–Pt(1)–Se(2)
Cl(1)–Pt(1)–Se(2)
N(2)–Pt(1)–Cl(1)
Pt(1)–Se(1)–Pt(2)
Pt(1)–Se(1)–C(21)
Pt(2)–Se(1)–C(21)
80.13(3)
96.19(18)
171.93(5)
175.92(18)
91.84(5)
91.82(18)
91.20(3)
103.8(2)
107.7(2)
Se(2)–Pt(2)–Se(1)
N(1)–Pt(2)–Se(2)
Cl(2)–Pt(2)–Se(2)
N(1)–Pt(2)–Se(1)
Cl(2)–Pt(2)–Se(1)
N(1)–Pt(2)–Cl(2)
Pt(2)–Se(2)–Pt(1)
Pt(2)–Se(2)–C(11)
Pt(1)–Se(2)–C(11)
80.22(3)
95.34(17)
172.30(5)
173.78(18)
92.38(5)
91.87(18)
91.58(3)
105.7(2)
109.3(2)
ppm
-4600
-4700
-4800
-4900
Fig. 3. 195Pt{1H} NMR spectrum of [PtCl(TeCH2CH2CH2NMe2)-
(PMePh2)]n (n = 1 or 2) in CDCl3.
phous to those of the corresponding palladium derivatives,
[PdCl(ECH2CH2CH2NMe2)]2 (E = S, Se or Te) [19,21].
The molecule comprises of two distorted square planar
platinum atoms bridged together by two selenolate groups
of symmetrically chelated SeCH2CH2CH2NMe2 ligands.
The coordination environment around each platinum atom
is defined by two Se, one N and one Cl atoms. The two
chloride ligands are mutually trans. The four-membered
Pt2Se2 ring is non-planar. The various bond lengths and
angles in the ‘‘PtClNSe2’’ fragments are comparable. The
two Pt–Se distances trans to N and trans to Cl are essen-
tially similar. The Pt–Cl [17,18,30], Pt–N [17,18,30], Pt–Se
[17,18,30] and Se–C [21] distances are well within the range
reported earlier. The Se–Pt–Se angles (80ꢁ) have reduced
considerably from the ideal value of 90ꢁ, consequently
other angles have opened up.
The molecular structure of [PtCl(SCH2CH2CH2NMe2)-
(PPr3)]2 (5a), established by the X-ray diffraction method,
is illustrated in Fig. 5. Selected bond lengths and bond
angles are given in Table 3. The molecule is a centrosym-
metric dimer comprising two distorted square planar plat-
inum atoms bridged together by thiolate groups. The
molecule has a sym-trans configuration with a planar
four-membered ‘‘Pt2S2’’ ring, the bridging SCH2CH2CH2-
NMe2 groups adopt an anti configuration with respect to
each other. Owing to high trans influence of phosphine
ligand, the Pt–S distances trans to P are longer than the
one trans to Pt–Cl. Various other bond angles around each
platinum atom are as expected for [Pt2Cl2(l-ER)2(PR3)2]
(E = S or Se) [27,31].
transfer transitions from electron-rich chalcogenolate
ligand centers to unoccupied metal orbitals (LMCT). The
absorptions of the complexes [Pt(ECH2CH2CH2NMe2)2]n
are intense and red-shifted in comparison to the correspon-
ding complexes [PtCl(ECH2CH2CH2NMe2)]2. According
to cyclic voltammetry in CH2Cl2/0.1 M Bu4NPF6, the che-
lating bridging chalcogenolates in Pt(II) complexes 1 are
oxidized irreversibly. The anodic peak potentials >0.9 V
for 1a and 1b show that they are hard to oxidize, but in case
of thiolate compound 1a rather facile oxidation takes place
in comparison to selenolate derivative 1b. The smaller
reduction potential (ꢀ1.76 V) of hexameric [Pt(SCH2CH2-
CH2NMe2)2]6 (2a) compared to dimeric [PtCl(SCH2CH2-
CH2NMe2)]2 (1a) may be explained due to increased orbital
interaction of the metal based LUMO which shifts to lower
energy in the case of 2a.
3.3. Crystal structures of 1b and 5a
The structure of [PtCl(SeCH2CH2CH2NMe2)]2 (1b) was
confirmed by single crystal X-ray diffraction methods. The
ORTEP plot with atomic numbering scheme is shown in
Fig. 4 and the selected bond lengths and angles are given
in Table 2. The structure of the title complex 1b is isomor-
In conclusion, the chemistry of platinum(II) N,N-dim-
ethylaminopropylchalcogenolates differs markedly from
the corresponding palladium derivatives both in terms of
stability and lability. While the platinum complexes of type
5 are readily isolated, the reactions to isolate palladium
counterparts of 5 lead to the formation of a mixture of
products. Different bonding modes, viz., chelating, chelat-
ing bridging, bridging of N,N-dimethylaminopropyl chal-
cogenolates, have been demonstrated.
Fig. 4. Molecular structure of [PtCl(SeCH2CH2CH2NMe2)]2 (1b) with
atomic numbering scheme.

S. Dey et al. / Inorganica Chimica Acta 360 (2007) 2653–2660
2659
s
Fig. 5. Molecular structure of [PtCl(SCH2CH2CH2NMe2)(PPr3)]2 (5a) with atomic numbering scheme.
Table 3
this article can be found, in the online version, at
doi:10.1016/j.ica.2007.01.002.
˚
Selected bond lengths (A) and angles (ꢁ) for [PtCl(SCH2CH2CH2NMe2)-
(PPr3)]2 (5a)
Pt–P
Pt–S
2.264(2)
2.383(2)
2.310(2)
2.355(2)
2.310(2)
1.845(9)
1.519(13)
C(2)–C(3)
N–C(4)
N–C(5)
1.520(13)
1.466(12)
1.469(13)
1.470(12)
1.831(9)
1.822(9)
1.860(9)
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