Palladium selenolates via oxidative addition of organylselenenyl halides to palladium(0) precursor and via cleavage reaction of diselenides: Synthesis, structure and spectroscopic investigation

Article abstract of DOI:10.1016/j.jorganchem.2011.04.018

Oxidative addition of bis[2-(4,4-dimethyl-2-oxazolinyl)phenyl] diselenide to Pd(PPh₃)₄ provided two different mononuclear palladium selenolato complexes, Pd(Se∩N)(PPh₃)Cl (4) [Se∩N = chelating 2-(4,4-dimethyl-2-oxazolinyl)

Full text of DOI:10.1016/j.jorganchem.2011.04.018

Journal of Organometallic Chemistry 696 (2011) 2782e2788
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Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Palladium selenolates via oxidative addition of organylselenenyl halides
to palladium(0) precursor and via cleavage reaction of diselenides:
Synthesis, structure and spectroscopic investigation
,
b
Tapash Chakraborty a, Kriti Srivastava a, Harkesh B. Singh a , Ray J. Butcher
*
a Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
b Department of Chemistry, Howard University, Washington, DC 20059, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
Oxidative addition of bis[2-(4,4-dimethyl-2-oxazolinyl)phenyl] diselenide to Pd(PPh3)4 provided two
Received 29 January 2011
Received in revised form
15 April 2011
different mononuclear palladium selenolato complexes, Pd(SeXN)(PPh3)Cl (4) [SeXN ¼ chelating 2-(4,4-
dimethyl-2-oxazolinyl)phenylselenolate] and Pd(SeXN)(SeXN*)(PPh3) (5) [SeXN
¼
chelating,
SeXN* ¼ non-chelating 2-(4,4-dimethyl-2-oxazolinyl)phenylselenolato ligand] in dicholoromethane and
toluene respectively. Complex 4 has also been synthesized by the oxidative addition of 2-(4,4-dimethyl-2-
oxazolinyl)phenylselenenyl chloride to Pd(PPh3)4. The bromo and iodo analogs of 4 (9 and 10) were simi-
larly synthesized by the oxidative addition of 2-(4,4-dimethyl-2-oxazolinyl)phenylselenenyl bromide and
iodide, respectively to Pd(PPh3)4. The oxidative addition of 2-(N,N-dimethylaminomethyl)phenylselenenyl
bromide and iodide to Pd(PPh3)4 afforded mononuclear palladium selenolate complexes, Pd(SeXN)(PPh3)
X (13 and 14) [SeXN ¼ chelating 2-(N,N-dimethylaminomethyl)phenylselenolate, X ¼ Br: 13, X ¼ I: 14]. The
reactions of bis[2-(4,4-dimethyl-2-oxazolinyl)phenyl] diselenide and bis[2-(N,N-dimethylaminomethyl)
phenyl] diselenide with Pd(COD)Cl2 provided dinuclear selenolato-bridged complexes [PdCl(SeXN)]2 (15)
Accepted 19 April 2011
Keywords:
Selenolate
Palladium
Oxidative addition
Selenenyl halide
Diselenide
[SeXN
¼
chelating 2-(4,4-dimethyl-2-oxazolinyl)phenylselenolate] and [PdCl(SeXN)]2 (19)
[SeXN ¼ chelating 2-(N,N-dimethylaminomethyl)phenylselenolate] respectively. The complexes were
characterized by elemental analysis and NMR (1H and 77Se) spectroscopy. Complexes 4 and 5 were also
characterized by mass spectrometry. Molecular structures of 4, 5, 9, 14 and 15 have been established by
single crystal X-ray diffraction analysis. Complexes 4 and 9 are isomorphous and crystallize in the space
group P21/c of the monoclinic systemwhere the selenolato and halo ligands are trans to each other. Complex
5 crystallizes in the space group P21/n of the monoclinic systemwhere one chelating and one non-chelating
selenolato ligands are trans to each other. Mononuclear complex 14 and binuclear centrosymmetric
complex 15 crystallize in the P1 space group of the triclinic system.
Ó 2011 Elsevier B.V. All rights reserved.
1. Introduction
The oxidative addition of EeE bonds (E ¼ S, Se, Te etc) to low-
valent transition metal complexes is among one of the basic
The coordination chemistry of the heavier organochalcogen
ligands with transition metals, particularly Group 10, is a rapidly
developing area of organometallic chemistry [1e5]. The interest in
this area arises from the realization that the complexes may serve
as single-source precursors for binary transition metal selenides
and tellurides which find applications in material science [6e10].
The area is of current interest also because of the potential appli-
cations in homogeneous catalysis [11e13].
processes of organometallic chemistry and provides a mild and
simple way to synthesize chalcogenolato complexes via the
cleavage of the EeE bond. However, in some instances the bond
remains intact [14e16]. On the other hand the reaction of ditel-
lurides with M(0) (M ¼ Ni, Pd, Pt) may also result in the cleavage of
the CeE bond [17e20]. In 1978, McWhinnie and Chia reported the
reaction of bis(2-dithienyl) ditelluride with Pd(PPh3)4, where
formation of a dinuclear palladium complex [Pd(TeTh)2(PPh3)]2
(Th ¼ 2-thienyl) with two terminal and two bridging tellurolate
ligands was suggested [21]. Furukawa et al. [22] also reported an
analogous complex from the reaction of Ph2Se2 with Pd(PPh3)4.
There was no structural characterization in either of the reports.
Laitinen and co-workers have reported, in a series of papers, their
* Corresponding author. Tel.: þ91 22 2576 7190; fax: þ91 22 2576 7152.
E-mail addresses: tapashc@gmail.com (T. Chakraborty), akriti@chem.iitb.ac.in
(K. Srivastava), chhbsia@chem.iitb.ac.in (H.B. Singh).
0022-328X/$ e see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2011.04.018

T. Chakraborty et al. / Journal of Organometallic Chemistry 696 (2011) 2782e2788
2783
work on the oxidative addition of bis(2-thienyl) diselenide and
ditelluride (Th2Se2 and Th2Te2), diphenyl diselenide and ditelluride
to palladium(0) and platinum(0) [23e25]. Recently, they have re-
ported on the oxidative addition of a cyclic ditelluride to plat-
inum(0) and have isolated two mononuclear and a dinuclear
tellurolate complexes of platinum [26]. Morley and co-workers
have also reported on the oxidative addition of Ph2Se2 and Fc2Se2
[Fc ¼ ferrocenyl] to palladium(0) and platinum(0) [27]. Very
recently, oxidative addition of bis(2-pyridyl)ditellurides to plat-
inum(0) has been reported where in addition to the expected
product of oxidative addition, an all-tellurium-donor tridentate
ligand coordinated platinum complexes have been obtained [28]. It
has been observed that the use of simple diselenides in oxidative
addition to palladium(0) generally leads to the formation of dinu-
clear complexes [23e25]. We thought of utilizing chelating dis-
elenides to isolate mononuclear complexes. Although the oxidative
addition of SeeSe bond to palladium(0) is common, there is no
report, to our knowledge, on the oxidative addition reactions of
SeeX (X ¼ Cl, Br and I) bonds to palladium(0).
Scheme 1. Formal selferedox reaction.
Herein we report the synthesis and characterization of a few
mononuclear palladium selenolato complexes by hitherto
a
unutilized method of oxidative addition of organylselenenyl halides
to palladium(0). Also the synthesis and characterization of a few
dinuclear palladium chalcogenolato complexes by the cleavage of
diorgano dichalcogenides with palladium(II) is described to
substantiate our earlier observation.
2. Results and discussion
2.1. Palladium selenolate complexes by oxidative addition to
palladium(0)
The reaction between bis[2-(4,4-dimethyl-2-oxazolinyl)phenyl]
diselenide (3) [34] and tetrakis(triphenylphosphine) palladium(0)
in dichloromethane and toluene provided two different mono-
nuclear palladium complexes 4 and 5 respectively (Scheme 2).
Complex 4 was recrystallized from chloroform/hexane mixture
(1:1) on keeping at room temperature for a week, whereas complex
5 was recrystallized from toluene/diethyl ether (10:1) on keeping at
room temperature for 10 min. The source of the chloro ligand in
complex 4 is, presumably, the chlorinated solvent chloroform or
dichloromethane, as these solvents are reported to be cleaved by
palladium(0) complexes [35]. Also slow dissociative processes of
palladium(II) complexes have been observed in CDCl3 [36]. Such
types of dissociative processes of palladium complexes in solution
have been observed earlier [23e25,37]. In view of this observation,
we thought of synthesizing complex 4 by a different route. The
oxidative addition of 2-(4,4-dimethyl-2-oxazolinyl)phenyl-
selenenyl chloride (6) [38] to tetrakis(triphenylphosphine) palla-
dium(0) in toluene at room temperature provided complex 4.
Complexes 9 and 10 were synthesized analogously by the oxidative
addition of 2-(4,4-dimethyl-2-oxazolinyl)phenylselenenyl bromide
(7) [38] and iodide (8) [38], respectively to the palladium(0)
precursor. Similarly the oxidative addition of 2-(N,N-dimethyla-
minomethyl)phenylselenenyl bromide (11) [39] and iodide (12)
[39] to Pd(PPh3)4 provided mononuclear palladium selenolate
complexes 13 and 14 respectively (Scheme 3). However, the reac-
tion of 19a with Pd(PPh3)4 was unsuccessful. It is worth noting that
for complexes 4, 5, 9, 10, 13 and 14, only one stereoisomer was
isolated as the major product. This is presumably predominantly
a steric effect imposed by the relatively large PPh3 ligand, rather
than an electronic one. Complexes were soluble in most of the
common organic solvents except diethyl ether and nonpolar
solvents like hexane and pentane. To purify the complexes from
In contrast to the oxidative addition reactions of diorgano dichal-
cogenides [R2E2, E ¼ Se, Te] to palladium(0)/platinum(0) [23e26,29],
there are very few examples of the cleavage reactions of R2E2 by pal-
ladium(II) [30]. Jain and co-workers have explored the reactions of
chelating alkyl selenolates and tellurolates, generated in situ from the
corresponding diselenides and ditellurides, as well as of alkyl dis-
elenides and ditellurides with palladium(II) and platinum(II) [30]. For
instance, diselenide (Me2NCH2CH2Se)2 afforded a trinuclear complex,
[PdCl(SeCH2CH2NMe2)]3, on reaction with Na2[PdCl4] [31]. On the
other hand, selenolate NaSeCH2CH2NMe2, prepared from the corre-
sponding diselenide by reduction with NaBH4, provided a mono-
nuclear complex, [Pd(SeCH2CH2NMe2)2(PPh3)2] on reaction with
PdCl2(PPh3)2. Again, selenolate NaSeCH2CH2NMe2, provided a dinu-
clear complex [Pd2Cl3(SeCH2CH2NMe2)(PPh3)2] when reacted with
[Pd2Cl2(m-Cl)2(PPh3)2] [31]. Very recently, Singh and co-workers have
reported the cleavage reactions of a series of a related chiral and achiral
multidentate selenium and tellurium ligands (1aec: Chart 1) with
palladium(II) precursor [32]. Diselenide 1b provided a selenolate
bridged dinuclear complex 2a on reaction with Pd(COD)Cl2. Ditellur-
ide 1c underwent cleavage of the TeeTe bond on reaction with
Pd(COD)Cl2 and a similar tellurolate bridged dinuclear complex 2b
was obtained. In addition to that, a dimeric chloro-bridged organyl
tellurenyl chloride [(RTeCl)2, R ¼ 2-CH2NMe2C6H4] was isolated and
characterized. It was shown that the R2E2 ligands (1aec) underwent a
formal selferedox reaction on treatment with Pd(COD)Cl2 (Scheme 1).
Ghavale et al. have also suggested that the reaction between dis-
elenides with Pd(II) proceeds via Pd(IV) intermediate which undergo
reductive elimination to afford palladium selenolate complexes along
with selenenyl halides as formal reduced and oxidized product
respectively [33]. Thus this reaction provides a general way to
synthesize dinuclear chalcogenolato palladium complexes.
Chart 1.
Scheme 2. Synthesis of mononuclear palladium selenolate complexes 4 and 5.

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T. Chakraborty et al. / Journal of Organometallic Chemistry 696 (2011) 2782e2788
Scheme 4. Synthesis of palladium chalcogenolato complexes 15, 17 and 19.
phenyl] diselenide (3) [34] and bis[2-(N,N-dimethylaminomethyl)
phenyl] diselenide (18) [39] and the ditelluride viz. bis[2-(4,4-
dimethyl-2-oxazolinyl)phenyl] ditelluride (16) [43] on reaction
with Pd(COD)Cl2 in dichloromethane provided the dinuclear
palladium chalcogenolate bridged complexes 15, 19 and 17
respectively. Organylselenenyl- and tellurenyl chlorides 15a, 19a,
17a were also obtained as byproducts. Selenenyl chlorides 15a and
19a are known compounds and were identified by comparing the
1H NMR and the elemental analysis [34,44,45]. Tellurenyl chloride
17a could not be isolated in the pure form. The palladium
complexes 15, 17 and 19 are soluble in common polar organic
solvents. However, once crystallized, the complexes became spar-
ingly soluble. Selenenyl and tellurenyl chlorides 15a, 19a, 17a were
more soluble than the complexes 15, 17 and 19 and the products
were separated by fractional crystallization.
Scheme 3. Synthesis of mononuclear palladium selenolate complexes 4, 9, 10, 13
and 14.
triphenyl phosphine impurity, washing of the crude product
several times with diethyl ether was essential. The complexes were
characterized by common spectroscopic techniques (1H, 77Se and
31P NMR) and elemental analysis. The 77Se NMR (Table 1) spectra
showed a gradual downfield shift in the series of the complexes 4, 9
and 10. Unexpectedly, the 77Se NMR of 5 in CDCl3 showed three
peaks instead of two which may be due to decomposition of the
complex in CDCl3 [35,36]. The 1H NMR spectrum of 5 also showed
unexpected multiple peaks in CDCl3 which is presumably due to
equilibrium between two species: a mono-chelated and a bis-
chelated complex [40e42]. This is indicated by the observation of
31P signal for free PPh3 at ꢀ10.2 ppm. The molecular ion cluster was
observed with the highest intensity peak at m/z 876.7 in the mass
spectrum of 5. The 1H NMR of 9 and 10 showed two broad peaks
due to NMe2 and CH2 protons and these peaks also corresponded to
lower integrated area than calculated. The multinuclear NMR
spectra of 8 and 9 showed presence of two different species in
equilibrium/isomerization in solution. Two closely spaced peaks
The complexes were characterized by common spectroscopic
techniques (1H, 77Se and 125Te NMR) and elemental analysis. The
methyl protons were anisochronous and showed multiple peaks
(four peaks at
d
1.72e1.79 ppm for 15, two peaks at
d 1.76 and
1.81 ppm for 17 and two peaks at
d
2.85 and 3.06 ppm for 19). The
eCH2e protons gave rise to a doublet of doublet indicating the
diastereotopic nature of the CH2 protons. An upfield shift of ca.
1346 ppm in the 77Se NMR spectrum of 15 (Table 1) with respect to
were observed in the 77Se NMR spectrum at
for 8 and at 362.0 and 362.4 ppm for 9. It is to be noted that on
d 306.3 and 306.6 ppm
the ligand 3 (d 455 ppm) is quite remarkable [46].
d
moving from the bromo- (8) to the iodo-complex (9)there is
a downfield shift in the 77Se NMR spectrum (Table 1).
2.2. Palladium chalcogenolate complexes by cleavage reaction of
diselenides and ditellurides with palladium(II)
Synthesis of the dinuclear palladium chalcogenolate complexes
15, 17 and 19 by the reductive cleavage reactions is depicted in
Scheme 4. The diselenides viz. bis[2-(4,4-dimethyl-2-oxazolinyl)
Table 1
77Se/125Te spectroscopic data of 4, 5, 9, 10, 13, 14, 15, 17 and 19 in CDCl3.
Complexes/ligands
77Se/125Te (
d, ppm)
4
240
5
180, 213, 277
9
259
10
13
14
15
17
19
3
284
306.3, 306.6 {2J (77See31P) ¼ 18 Hz}
362.0, 362.4 {2J (77See31P) ¼ 21 Hz}
ꢀ892
ꢀ145
ꢀ50
455
417
430
Fig. 1. Molecular structure of 4; thermal ellipsoids are drawn at the 30% probability
level; hydrogen atoms are removed for clarity. Selected bond lengths (Å) and bond
angles (ꢁ): PdeN 2.117 (4), PdeP 2.2387 (12), PdeSe 2.3896 (6), PdeCl 2.4155 (10),
SeeC1 1.902 (5) Å; PePdeSe 88.91 (3), NePdeCl 95.67 (10), PePdeCl 85.65 (4),
NePdeSe 89.60 (10), SeePdeCl 170.72 (4), NePdeP 178.10 (11), C1eSeePd 101.66
(15)ꢁ.
16
18

T. Chakraborty et al. / Journal of Organometallic Chemistry 696 (2011) 2782e2788
2785
Fig. 4. Molecular structure of 5; thermal ellipsoids are drawn at the 30% probability
level; hydrogen atoms are removed for clarity. Selected bond lengths (Å) and bond
angles (ꢁ):PdeN1 2.122 (2), PdeP 2.2278 (8), PdeSe1 2.4252 (4), PdeSe2 2.4540 (4),
Se1eC1A 1.917 (3), Se2eC1B 1.922 (3) Å; N1ePdeP 171.29 (7), N1ePdeSe1 87.19 (7),
PePdeSe1 86.31 (2), N1ePdeSe2 99.08 (7), PePdeSe2 88.51 (2), Se1ePdeSe2 166.423
(16), C1AeSe1ePd 94.15 (9), C1BeSe2ePd 102.58 (10)ꢁ.
Fig. 2. Molecular structure of 9; thermal ellipsoids are drawn at the 30% probability
level; hydrogen atoms are removed for clarity. Selected bond lengths (Å) and bond
angles (B): PdeN 2.126 (3), PdeP 2.2459 (9), PdeSe 2.3937 (5), PdeBr 2.4917 (5),
SeeC1 1.900 (4) Å; PePdeSe 88.69 (3), NePdeBr 95.93 (10), PePdeBr 85.68 (3),
NePdeSe 89.54 (10), SeePdeBr 170.02 (2), NePdeP 178.01 (10), C1eSeePd 101.51
(13)ꢁ.
trans influence of the groups: Clꢀ < Brꢀ < Iꢀ. The six membered
chelate ring forms a boat conformation. The geometry around the
selenium atom is V-shaped.
2.3. Molecular structures
In structure 5, the PdeSe bond [2.4252 (4) Å] of the chelating
ligand is slightly shorter than that of the non-chelating ligand
[2.4540 (4) Å]. Both the bonds are, however, longer than those in
4 [2.3896 (6) Å], 9 [2.3937 (5) Å] and 14 [2.4218 (3) Å] as well as that
in the palladium complex PdL(PnBu3) (5a) [L ¼ SeC(R)]C(R)]N]
NC(R)]C(R)Se, R ¼ (CH2)4] [2.370 (2) Å, 2.371 (1) Å] [54]. The PdeP
bond [2.2278 (8) Å] is slightly shorter than those in 4 [2.2387 (12)
Å], 9 [2.2459 (9) Å], 14 [2.2429 (5) Å] and 5a [2.264 (2) Å]. The
PdeSe and PdeP bond lengths are also comparable to those in
Pd(4eCH3C6H4Se)2(CNC6H4)(PPh3) [55].
2.3.1. Molecular structures of 4, 9, 14 and 5
The molecular structures are depicted in Figs. 1e4. The palla-
dium center is coordinated to the atoms N, Se, P and X [X ¼ Cl (4), Br
(9) and I (14)] in an essentially square planar geometry. The halo
ligand is trans to the selenium while the phosphine ligand is trans to
the nitrogen in the cases of 4, 9 and 14. The greater trans influence
of PPh3 and Se is reflected in the slight elongation of the PdeCl
[2.4155 (10) Å] and PdeN [2.117 (4) Ǻ] bonds as compared to other
related structures [31,47e51]. The PdeBr [2.4917 (5) Å] bond length
in 9 is comparable to 2.4548 (5)e2.4832 (5) Å, observed in
[PPh4]2[Pd2(m-Se2N2S)Br4] [52]. The PdeI bond length [2.6772 (2)
2.3.2. Molecular structure of 15
Å] in structure 14 is slightly longer than 2.651 (2) Å, observed in
[PdI(Se{Et}C8H12Se)(PPh3)] (14a) [53]. The PdeSe [2.4218 (3) Å and
PdeP [2.2429 (5) Å] bond lengths are also comparable to those
observed in 14a. The increasing order of PdeSe bond length in
complexes 4, 9 and 14: 2.3896 (6) Å [4 (PdeCl)] < 2.3937 (5)
[9 (PdeBr)] < 2.4218 (3) [14 (PdeI)] reflects the increasing order of
The centrosymmetric dinuclear palladium selenolate complex
15 crystallized in the P1 space group of the triclinic system. The unit
cell contains two discrete molecules having different geometric
parameters. The molecular structure of one of them is shown in
Fig. 5. Molecular structure of 15; thermal ellipsoids are drawn at the 70% probability
level; hydrogen atoms are removed for clarity. Selected bond lengths (Å) and bond
angles (ꢁ):Pd1eN1A 2.1007 (15), Pd1eCl1A 2.3560 (5), Pd1eSe1A 2.3777 (2),
Pd1eSe1Ai 2.4017 (2), Se1AeC1A 1.9227 (18), Se1AePd1i 2.4017 (2); N1AePd1eCl1A
97.15 (4), N1AePd1eSe1A 88.31 (4), Cl1AePd1eSe1A 174.496 (14), N1AePd1eSe1Ai
164.74 (4), Cl1AePd1eSe1Ai 93.063 (13), Se1AePd1eSe1Ai 81.716 (8), C1AeSe1AePd1
94.24 (5)ꢁ.
Fig. 3. Molecular structure of 14; thermal ellipsoids are drawn at the 30% probability
level; hydrogen atoms are removed for clarity. Selected bond lengths (Å) and bond
angles (ꢁ): PdeN 2.1958 (18), PdeP 2.2429 (5), PdeSe 2.4218 (3), PdeI 2.6772 (2),
SeeC1 1.906 (2) Å; PePdeSe 87.368 (16), NePdeI 93.11 (5), PePdeI 88.332 (15),
NePdeSe 92.80 (5), SeePdeI 165.841 (9), NePdeP 172.96 (5), C1eSeePd 99.13 (7)ꢁ.

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T. Chakraborty et al. / Journal of Organometallic Chemistry 696 (2011) 2782e2788
Fig. 5. The coordination environment of each palladium of the
dinuclear complex is defined by two selenium donors of the two
bridging selenolate ligands, one chloro and one nitrogen donor in
a near square planar arrangement. The two PdeSe distances in each
of the molecule are different [2.3777 (2) Å, 2.4017 (2) Å; 2.3594 (2)
Å, 2.3779 (2) Å] from each other and comparable to those reported
for related bridging selenolate palladium complexes [53e56]. The
Pd/Pd distances in the two molecules are 3.553 Å and 3.615 Å
which are less than the sum of their van der Waals radii (4.100 Å)
[57]. These distances are, however, greater than the corresponding
distances in the thiolato-bridged analogs and shorter than the
corresponding distances in the tellurolato-bridged complexes
[30,58e60]. This trend is easily explained in terms of the size of the
chalcogen atoms which increases from S to Te through Se. The Se
atoms are approximately in a pyramidal coordination with the
angles being 94.24 (5) Å, 98.284 (8) Å, and 109.87 (5) Å in one
molecule and 94.36 (5) Å, 97.189 (8) Å and 108.36 (5) Å in the other.
The bite angles of the chelating SeeN ligand are 88.31 (4) Å and
86.00 (4) Å in the two molecules. None of the crystal structures
show presence of any chalcogenehalogen secondary bonds.
hexane (1:3) afforded red crystals of 4. Yield: 75 mg (57%), mp
218e220 ꢁC.
Method B: [2-(4,4-Dimethyl-2-oxazolinyl)phenyl]selenenyl
chloride [38] (114 mg, 0.40 mmol) was dissolved in 20 mL of dry
dichloromethane to which tetrakis[triphenylphosphine] palla-
dium(0) (462 mg, 0.40 mmol) was added and stirred at ambient
temperature for 6 h. The solution was passed through a celite pad
and then concentrated to ca. 5 mL by partial evaporation of solvent.
Upon addition of hexane (10 mL) and on trituration a red precipi-
tate formed. The precipitate was filtered off, washed with diethyl
ether and hexane and dried under vacuum. Yield: 215 mg (83.5%),
mp 218e220 ꢁC. Anal. Calcd for C29H27ClNOPPdSe: C, 52.99; H, 4.14;
N, 2.13. Found: C, 52.88; H, 3.78; N, 2.25. 1H NMR (CDCl3):
d 1.91 (s,
6H), 4.26 (s, 2H), 7.07e7.16 (m, 2H), 7.27e7.53 (m, 11H), 7.72e7.77
(m, 6H). 31P NMR (CDCl3):
279.14 [PPh3O]þ, 100].
d
28.6. ESI-MS: m/e 622.11 [(MꢀCl)þ, 60],
4.2. Synthesis of 5
Bis[2-(4,4-dimethyl-2-oxazolinyl) phenyl] diselenide [34]
(202 mg, 0.40 mmol) was dissolved in 20 mL of dry toluene to
which tetrakis[triphenylphosphine] palladium(0) (462 mg,
0.40 mmol) was added and stirred at ambient temperature for 6 h.
The solution was passed through a celite pad and then concentrated
to ca. 5 mL by partial evaporation of solvent. Upon addition of
diethyl ether (5 mL) dark brown crystals of the titled complex
formed. The solid was filtered off, washed with diethyl ether and
hexane and dried under vacuum. Yield: 310 mg (88%), mp
230e232 ꢁC. Anal. Calcd for C40H39N2O2PPdSe2: C, 54.90; H, 4.49; N,
3.20. Found: C, 54.67; H, 3.93; N, 3.20. 31P NMR (CDCl3):
3. Conclusion
In conclusion, synthesis of mononuclear palladium selenolato
complexes has been demonstrated by the oxidative addition of
chelating organylselenenyl halides to palladium(0) precursor. Also
synthesis of dinuclear palladium complexes with bridging seleno-
lato ligands has been achieved by the cleavage of the chelating
diorgano diselenides.
d
29.2, ꢀ10.2 (PPh3). ESI-MS: m/e 876.7 [Mþ, 100], 621.84
4. Experimental
[C29H27NOPPdSeþ, 95].
All the reactions were carried out under nitrogen or argon using
standard vacuum-line techniques. Solvents were purified and dried
by standard procedures and were distilled prior to use. Bis[2-(4,4-
dimethyl-2-oxazolinyl)phenyl] diselenide [34], 2-(4,4-dimethyl-2-
oxazolinyl)phenylselenenyl chloride, bromide and iodide [38],
2-(N,N-dimethylaminomethyl)phenylselenenyl bromide and iodide
[39], bis[2-(N,N-dimethylaminomethyl)phenyl] diselenide [39] and
bis[2-(4,4-dimethyl-2-oxazolinyl)phenyl] ditelluride [43] were
prepared by published procedures. Melting points were recorded
on a Veego VMP-I melting point apparatus in capillary tubes and
were uncorrected. Nuclear magnetic resonance spectra, 1H
(400.13 MHz), 13C (100.56 MHz) and 31P (161.92 MHz) were recor-
ded on a Varian Mercury plus 400 MHz spectrometer and 77Se
(57.22 MHz) and 125Te (94.79 MHz) on a Varian VXR 300S spec-
trometer. Chemical shifts are cited with respect to Me4Si as internal
standard (1H, 13C), Me2Se (77Se), Me2Te (125Te) and 85% aq. H3PO4
4.3. Synthesis of 9, 10, 13, 14
4.3.1. Synthesis of 9
[2-(4,4-Dimethyl-2-oxazolinyl)phenyl]selenenyl bromide [38]
(133 mg, 0.40 mmol) was dissolved in 20 mL of dry toluene to
which tetrakis[triphenylphosphine] palladium(0) (462 mg,
0.40 mmol) was added and stirred at ambient temperature for
6 h. The solution was passed through a celite pad and then
concentrated to ca. 5 mL by partial evaporation of solvent. Upon
addition of hexane (10 mL) and on trituration a red precipitate
formed. The precipitate was filtered off, washed with diethyl
ether and hexane and dried under vacuum to get a magenta
powder. Yield: 210 mg (75%), mp 238e240 ꢁC. Anal. Calcd for
C29H27BrNOPPdSe: C, 49.63; H, 3.88; N, 2.00. Found: C, 49.98; H,
3.49; N, 1.70. 1H NMR (CDCl3):
7.07e7.16 (m, 2H), 7.34e7.49 (m, 11H), 7.73e7.78 (m, 6H). 31P
NMR (CDCl3): 28.5.
d 1.92 (s, 6H), 4.29 (s, 2H),
(
31P) as external standard. Elemental analyses were performed on
a Carlo Erba elemental analyzer model 1106. The ESI mass spectra
were recorded on a Q-Tof micro (YA-105) mass spectrometer.
d
4.3.2. Synthesis of 10
4.1. Synthesis of 4
Yield: 215 mg (72%), mp 241e243 ꢁC. Anal. Calcd for
C29H27INOPPdSe: C, 46.52; H, 3.63; N, 1.87. Found: C, 46.95; H,
Method A: Bis[2-(4,4-Dimethyl-2-oxazolinyl)phenyl] diselenide
[34] (101 mg, 0.20 mmol) was dissolved in 20 mL of dry dichloro-
methane to which tetrakis[triphenylphosphine] palladium(0)
(231 mg, 0.20 mmol) was added and stirred at ambient tempera-
ture for 12 h. The solution was passed through a column of florisil
(0.7 cm ꢂ 5 cm), and then concentrated to ca. 5 mL by partial
evaporation of solvent. Upon addition of hexane (10 mL) and on
trituration a red precipitate formed. The precipitate was filtered off,
washed with diethyl ether and hexane and dried under vacuum
to get a magenta powdered solid. Recrystallization from CHCl3/
3.40; N, 2.08. 1H NMR (CDCl3):
d
1.91 (s, 6H), 4.33 (s, 2H),
7.03e7.15 (m, 2H), 7.29e7.43 (m, 11H), 7.71e7.76 (m, 6H). 31P
NMR (CDCl3): 29.5.
d
4.3.3. Synthesis of 13
Yield: 195 mg (73%), mp 197e199 ꢁC. Anal. Calcd for
C27H27BrNPPdSe: C, 49.00; H, 4.11; N, 2.12. Found: C, 49.80; H, 3.74;
N, 2.29. 1H NMR (CDCl3):
d
2.84 (b, 6H), 3.67 (b, 2H), 7.12e7.20 (m,
2H), 7.37e7.48 (m, 9H), 7.53e7.58 (m, 2H), 7.64e7.74 (m, 6H). 31P
NMR (CDCl3): 29.2, 29.7.
d

T. Chakraborty et al. / Journal of Organometallic Chemistry 696 (2011) 2782e2788
2787
Table 2
Crystal data and structure refinement for 4, 5, 9, 14 and 15.
4
5
9
14
15
Empirical formula
Formula weight
Crystal system
Space group
a [Å]
C29H27ClNOPPdSe
657.30
Monoclinic
P2/1c
15.2717 (7)
11.0133 (3)
17.5843 (8)
90
113.448 (6)
90
2713.31 (19)
4
1.609
295 (2)
4.67 to 32.56
2.205
C40H39N2O2PPdSe2
875.02
Monoclinic
P2/1n
19.0569 (8)
8.7203 (4)
23.0467 (10)
90
111.008 (2)
90
3575.4 (3)
4
1.626
296 (2)
2.91 to 28.36
2.638
C29H27BrNOPPdSe
701.76
Monoclinic
P2/1c
15.3355 (3)
11.1817 (2)
17.4125 (4)
90
113.598 (3)
90
2736.14 (10)
4
1.704
295 (2)
5.05 to 77.71
9.427
C27H27INPPdSe
708.73
Triclinic
P1
9.0542 (3)
10.6774 (3)
15.1732 (5)
72.887 (3)
74.896 (3)
70.549 (3)
1300.22 (7)
2
C22H24Cl2N2O2Pd2Se2
790.05
Triclinic
P1
6.8522 (3)
13.3785 (5)
14.0559 (6)
105.786 (2)
100.446 (2)
93.386 (2)
1211.36 (9)
2
2.166
203 (2)
3.03 to 32.73
4.733
b [Å]
c [Å]
a
b
g
[ꢁ]
[ꢁ]
[ꢁ]
V [Å3]
Z
Dcalcd. [mgmꢀ3
Temp [K]
]
1.810
295 (2)
5.15 to 32.81
3.377
q
range [ꢁ]
Abs. coeff. [mmꢀ1
]
Final R(F)
0.0422
0.0354
0.0448
0.0277
0.0215
[I > 2
wR(F2) indices
[I > 2 (I)]
s
(I)]a
0.1137
0.0666
0.0485
0.0479
0.0282
s
R indices (all data)
wR2 (all data)
0.1137
0.1599
9007/0/316
1.120
0.0666
0.0813
8817/0/439
1.003
0.0485
0.1235
5708/192/299
1.053
0.0479
0.0594
8617/0/291
0.913
0.0282
0.0518
8823/0/293
1.043
Data/restraints/parameters
Goodness of fit on F2
P
P
P
P
a
2
Definitions: R(Fo) ¼ jjFojꢀjFcjj/ jFoj and wR(Fo2) ¼ { [w(Fo ꢀFc2)]2/ [w(Fc2)2]}1/2
.
4.3.4. Synthesis of 14
5. Crystal structure determination of 4, 5, 9, 14 and 15
Yield: 230 mg (81%), mp 201e203 ꢁC. Anal. Calcd for
C27H27INPPdSe: C, 45.75; H, 3.84; N, 1.98. Found: C, 47.07; H, 3.62;
The diffraction measurements were performed at room
temperature (for 4, 5, 9 and 14) and at 203 (2) K (for 10) on an Oxford
Diffraction Gemini diffractometer (for 4, 9 and 14) and on a Bruker
Apex 2 diffractometer (for 5 and 15) with graphite-monochromated
N, 1.76. 1H NMR (CDCl3):
d
2.96 (b, 6H), 3.71 (b, 2H), 7.11e7.19 (m,
2H), 7.31e7.45 (m, 9H), 7.52e7.54 (d, J ¼ 7.2 Hz, 2H), 7.65e7.75 (m,
6H). 31P NMR (CDCl3):
29.1, 29.2.
d
Mo K
radiation (
a
radiation (
l
¼ 0.71073 Å) (for 4, 5, 14 and 15) and with Cu K
a
l
¼ 1.54184 Å) (for 9). The data were corrected for Lorentz,
4.4. Synthesis of 15, 17, 19
polarization and absorption effects. The structures were determined
by routine heavy-atom methods using SHELXS 97 [61] and Fourier
methods and refined by full-matrix least squares with the non-
hydrogen atom anisotropic and hydrogen with fixed isotropic
thermal parameters of 0.07 Å2 by means of the SHELXL 97 [62]
program. The hydrogens were partially located from difference
electron-density maps, and the rest were fixed at predetermined
positions. Scattering factors were from common sources [63]. Some
details of the data collection and refinement are given in Table 2.
4.4.1. Synthesis of 15
To a solution of bis[2-(4,4-dimethyl-2-oxazolinyl) phenyl] dis-
elenide [34] (152 mg, 0.30 mmol) in 20 mL of dry dichloromethane
was added Pd(COD)Cl2 (85.5 mg, 0.30 mmol) and stirred at ambient
temperature for 2 h. The solution was filtered through a celite pad
and concentrated to ca. 2 mL. It was then layered with 1 mL of
hexane and kept at 0 ꢁC overnight when orange crystals of the titled
compound were obtained. Yield: 145 mg (61%), mp 215e217 ꢁC.
Anal. Calcd for C22H24Cl2N2O2Pd2Se2: C, 33.44; H, 3.06; N, 3.55.
Found: C, 33.64; H, 2.97; N, 5.85. 1H NMR(CDCl3):
d 1.72e1.79 (4
Acknowledgments
lines, eC(Me2)e, 12H), 4.29e4.35 (dd, J ¼ 12.8, 8.8 Hz, eCH2e, 4H),
7.31e7.42 (m, 2H), 7.42e7.55 (m, 4H), 8.64e8.66 (m, 1H), 9.03e9.05
(m, 1H).
We are thankful to the Department of Science and Technology
(DST), India for funding this work. Additional help from the
Sophisticated Analytical Instrument Facility (SAIF), Indian Institute
of Technology, Bombay, for 300 MHz NMR spectroscopy is grate-
fully acknowledged. T. C. and K. S. are also grateful to the Council of
Scientific and Industrial Research, India for providing fellowship.
4.4.2. Synthesis of 17
Reaction time: 30 min, Crystallization done at ambient
temperature. Yield: 115 mg (43%), mp 230e231 ꢁC. Anal. Calcd for
C22H24Cl2N2O2Pd2Te2: C, 29.78; H, 2.73; N, 3.16. Found: C, 29.49; H,
2.17; N, 3.77. 1H NMR (CDCl3):
d 1.76e1.81 (2 lines, eC(Me2)e, 6H),
Appendix A. Supplementary material
4.30e4.36 (dd, J ¼ 12, 8.8 Hz, eCH2e, 2H), 7.25e7.35 (m, 2H), 7.50
CCDC numbers 790808e790812 for 14,15, 4, 5 and 9, respectively
contain the supplementary crystallographic data for this paper. These
data can be obtained free of charge from The Cambridge Crystallo-
graphic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
(d, J ¼ 8 Hz, 1H), 8.95 (d, J ¼ 8 Hz, 1H).
4.4.3. Synthesis of 19
Reaction time: 2 h, Crystallization done at ambient tempera-
ture. Yield: 130 mg (52%), mp 250e252 ꢁC. Anal. Calcd for
C18H24Cl2N2Pd2Se2.CH2Cl2: C, 28.70; H, 3.30; N, 3.52. Found: C, 28.71;
Appendix. Suppplementary material
H, 3.07; N, 3.83. 1H NMR (CDCl3):
d 2.85e3.06 (2 lines, eNMe2, 6H),
3.11 (d, J ¼ 12Hz, eCH2e, 1H), 3.95 (d, J ¼ 12Hz, eCH2e, 1H),
Supplementary materialassociated with this article can be found,
in the online version, at doi:10.1016/j.jorganchem.2011.04.018.
7.08e7.11 (m, 1H), 7.29e7.31 (m, 2H), 8.80e8.82 (m, 1H).

2788
T. Chakraborty et al. / Journal of Organometallic Chemistry 696 (2011) 2782e2788
[33] N. Ghavale, A. Wadawale, S. Dey, V.K. Jain, Indian J. Chem. 48A (2009)
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