Reactivity of dipyrimidyldiselenides with [M(PPh3)4] and 2-pyrimidylchalcogenolates with [MCl2(diphosphine)] (M = Pd or Pt)

Article abstract of DOI:10.1016/j.jorganchem.2012.06.036

Oxidative addition reactions of {SeC₄H(4,6-R)₂N ₂}₂ with [M(PPh₃)₄] (M = Pt or Pd) in benzene afforded complexes of composition, [Pt{SeC₄H(4,6-R) ₂N₂}₂(PPh₃)₂] (1) and [Pd{η²-SeC₄H(4,6-R)₂N₂}{SeC ₄H(4,6-R)₂N₂}(PPh₃)] (3) (R = H or Me). The former when left in solution dissociated to [Pt{η²- SeC₄H(4,6-R)₂N₂}{SeC₄H(4,6-R) ₂N₂}(PPh₃)] (2) and PPh₃. Treatment of [PtCl₂(P^∩P)] (P^∩P = dppe or dppp) and NaEC₄H(4,6-R)₂N₂ (for E/R = Se/H/Me or Te/Me) gave mononuclear complexes [Pt{EC₄H(4,6-R)₂N ₂}₂(P^∩P)] (4 and 6) (R = H or Me, P ^∩P = dppe or dppp) which on leaving for recrystallization in dichloromethane/CDCl₃ solution resulted in trinuclear chalcogenido-bridged complexes [Pt₃(μ-E)₂(P ^∩P)₃]·2Cl (E = Se or Te) (6). The latter were also formed when [PtCl₂(P^∩P)] (P^∩P = dppe or dppp) was treated with sodium 2-pyrimidyltellurolate. The substitution reactions between [PdCl₂(P^∩P)] (P^∩P = dppe or dppp) and NaEC₄H(4,6-R)₂N₂ (E = Se or Te; R = H or Me) afforded chalcogenido-bridged trinuclear complexes, [Pd ₃(μ-E)₂(P^∩P)₃]2Cl (7) (P ^∩P = dppe or dppp). These complexes were characterized by elemental analyses and NMR (¹H, ³¹P, ⁷⁷Se, ¹²⁵Te, ¹⁹⁵Pt) spectroscopy. The molecular structures of [Pt(SeC₄H₃N₂)₂(PPh₃) ₂] (1a) and [Pd{η²-SeC₄H₃N ₂}{SeC₄H₃N₂}(PPh₃)] (3a) were established by single crystal X-ray diffraction analyses. Metal atom in these complexes acquires a distorted squareplanar configuration.

Full text of DOI:10.1016/j.jorganchem.2012.06.036

Journal of Organometallic Chemistry 717 (2012) 180e186
Contents lists available at SciVerse ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Reactivity of dipyrimidyldiselenides with [M(PPh3)4]
and 2-pyrimidylchalcogenolates with [MCl2(diphosphine)]
(M ¼ Pd or Pt)
,
,
,
b
b
Rohit Singh Chauhan a 1, Rakesh K. Sharma a 1, G. Kedarnath a , David B. Cordes , Alexandra M.Z. Slawin ,
*
,
Vimal K. Jain a
*
a Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400 085, India
b School of Chemistry, University of St. Andrews, St. Andrews, KY16 9ST Fife, UK
a r t i c l e i n f o
a b s t r a c t
Article history:
Oxidative addition reactions of {SeC4H(4,6-R)2N2}2 with [M(PPh3)4] (M ¼ Pt or Pd) in benzene afforded
complexes of composition, [Pt{SeC4H(4,6-R)2N2}2(PPh3)2] (1) and [Pd{h
2-SeC4H(4,6-R)2N2}
Received 9 May 2012
Received in revised form
21 June 2012
{SeC4H(4,6-R)2N2}(PPh3)] (3) (R ¼ H or Me). The former when left in solution dissociated to [Pt
{
h
2-SeC4H(4,6-R)2N2}{SeC4H(4,6-R)2N2}(PPh3)] (2) and PPh3. Treatment of [PtCl2(PXP)] (PXP ¼ dppe or
Accepted 27 June 2012
dppp) and NaEC4H(4,6-R)2N2 (for E/R ¼ Se/H/Me or Te/Me) gave mononuclear complexes [Pt{EC4H(4,6-
R)2N2}2(PXP)] (4 and 6) (R ¼ H or Me, PXP ¼ dppe or dppp) which on leaving for recrystallization in
Keywords:
Palladium
Platinum
Pyrimidylselenide
Pyrimidyltelluride
X-ray structure
dichloromethane/CDCl3 solution resulted in trinuclear chalcogenido-bridged complexes [Pt3(m-
E)2(PXP)3]$2Cl (E ¼ Se or Te) (6). The latter were also formed when [PtCl2(PXP)] (PXP ¼ dppe or dppp)
was treated with sodium 2-pyrimidyltellurolate. The substitution reactions between [PdCl2(PXP)]
(PXP ¼ dppe or dppp) and NaEC4H(4,6-R)2N2 (E ¼ Se or Te; R ¼ H or Me) afforded chalcogenido-bridged
trinuclear complexes, [Pd3(
m
-E)2(PXP)3]2Cl (7) (PXP ¼ dppe or dppp). These complexes were charac-
terized by elemental analyses and NMR (1H, 31P, 77Se, 125Te, 195Pt) spectroscopy. The molecular structures
of [Pt(SeC4H3N2)2(PPh3)2] (1a) and [Pd{h
2-SeC4H3N2}{SeC4H3N2}(PPh3)] (3a) were established by single
crystal X-ray diffraction analyses. Metal atom in these complexes acquires a distorted squareplanar
configuration.
Ó 2012 Elsevier B.V. All rights reserved.
1. Introduction
[Pd(EAr)2(PR3)2] (E ¼ S or Se) complexes [15], although binuclear
complexes, [Pd2(EAr)2(m-EAr)2(PR3)2] are generally isolated when
The chemistry of platinum group chalcogenolate complexes
continues to be an active area of considerable research owing to
several obvious reasons. These include their use as molecular tec-
tons for the synthesis of high nuclearity of complexes [1e3],
precursors for low temperature synthesis of metal chalcogenides
[4e6] and their relevance in catalysis [7e10]. Palladium catalyzed
addition of EeE bond to alkyne has emerged an important strategy
to prepare vinylsulfides/selenides [9] which find numerous appli-
cations in organic synthesis, coordination chemistry and elec-
tronics [11e14]. The catalytic reaction proceeds with excellent
stereoselectivity and is believed to involve mononuclear cis-
[Pd(PR3)4] is treated with ArEEAr (E ¼ S or Se) [16e19]. Such
reactions with diaryl ditellurides, in contrast, yield several products
due to competitive cleavage of TeeTe and TeeC bonds [20e22].
Recently we have investigated reactions of hemilabile pyr-
idylchalcogenolate ligands, (RC5H3NeE) (E ¼ Se or Te), with M0 and
MII phosphine complexes in view to isolate and characterize
metastable complexes stabilized through EXN bonding [23e25].
Indeed we could isolate, besides expected products, several
serendipitous products like [Pt(2-TeC5H4N)2(Te)(PPh3)] contain Te0
as a ligand [23], and [Pt{PPh2C(TeC5H3(3-R)N)PPh2}2] (R ¼ H or Me)
[24] as well as metastable species like [Pd(2-TeC5H4N)2(dppp)]
which in chlorinated hydrocarbon solvents solution slowly trans-
formed to a trinuclear product [Pd3(m
-Te)2(dppp)3]2þ via other
intermediate complexes [25]. These reactions have prompted us to
examine chemistry of ligand systems where chalcogen carbon
is indirectly linked to two heteroatoms, e.g. 2-pyrimidyl group, so
as to enhance both denticity of the ligand and basicity of
* Corresponding authors. Tel.: þ91 22 25595095; fax: þ91 22 25505151.
E-mail addresses: kedar@barc.gov.in (G. Kedarnath), amzs@st-andrews.ac.uk
(A.M.Z. Slawin), jainvk@barc.gov.in (V.K. Jain).
1
Tel.: þ91 22 25595095; fax: þ91 22 25505151.
0022-328X/$ e see front matter Ó 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.jorganchem.2012.06.036

R.S. Chauhan et al. / Journal of Organometallic Chemistry 717 (2012) 180e186
181
Table 1
the heterocyclic ring. Accordingly we have synthesized
2-chalcogenopyrimidyl ligands (I) and studied their reactions with
M0 and MII (M ¼ Pd or Pt) phosphine complexes. The results for this
work are reported herein.
Crystallographic and structural determination data for [Pt(SeC4H3N2)2(PPh3)2]$
2CH2Cl2 (1a$2CH2Cl2) and [Pd{
h
2-SeC4H3N2}{SeC4H3N2}(PPh3)]. CH2Cl2 (3a$CH2Cl2).
Complex
1a$2CH2Cl2
3a$CH2Cl2
Chemical formula
Formula wt.
Crystal size (mm3)
Crystal system
Space group
Unit cell dimensions
a (Å)
C44H36N4P2PtSe2$2CH2Cl2
1205.57
C26H21N4PPdSe2$CH2Cl2
769.68
0.11 ꢂ 0.04 ꢂ 0.03
0.15 ꢂ 0.10 ꢂ 0.10
Monoclinic
Monoclinic
P21/c
P21/n
11.546(4)
13.308(5)
15.224(6)
107.359(8)
2232.6(14)
1.793
14.726(4)
10.539(3)
19.055(6)
107.142(8)
2825.9(14)
1.809
(R = H or Me; E = Se or Te)
b (Å)
c (Å)
b
(ꢀ)
Volume (Å3)
rcalcd, g cmꢁ3
Z
(I)
2
4
m
(mmꢁ1)/F(000)
5.123/1176
ꢁ11 ꢃ h ꢃ 13
ꢁ11 ꢃ k ꢃ 16
ꢁ18 ꢃ l ꢃ 15
2.40e25.34
3.503/1504
ꢁ17 ꢃ h ꢃ 17
ꢁ12 ꢃ k ꢃ 12
ꢁ17 ꢃ l ꢃ 22
1.55e25.36
Limiting indices
2. Experimental
Elemental selenium (99.99%), tellurium (99.99%), sodium boro-
hydride and tertiary phosphines were obtained from commercial
sources (Aldrich/Strem). The compounds, 2-bromopyrimidine,
2-chloro-4,6-dimethylpyrimidine [26], [M(PPh3)4], (M ¼ Pd [27], Pt
q
for data
collection (ꢀ)
No of reflections
collected
No of independent
reflection
Data/restraints/
parameters
Final R1, wR2
indices
4049
5090
3092
4336
[28]), [MCl2(PXP)] [PXP
¼
dppm (bis(diphenylphosphino)
methane), dppe (1,2-bis(diphenylphosphino)ethane), dppp
(1,3-bis(diphenylphosphino)propane)] [29,30] and the ligands
(SeC4H3N2)2 [31], {SeC4H(4,6-Me)2N2}2 and {TeC4H(4,6-R)2N2}2
were prepared by literature methods. All syntheses were carried out
under a nitrogen atmosphere in dry solvents. Organo-selenium
and -tellurium compounds were purified by column chromatog-
raphy on silica gel (60/120 mesh size) using solvent mixtures as
eluents and the purity was evaluated by NMR spectroscopy.
The 1H, 13C{1H}, 31P{1H}, 77Se{1H}, 125Te{1H} and 195Pt{1H} NMR
spectra were recorded on a Bruker Avance-II spectrometer oper-
ating at 300, 75.47,121.49, 57.23, 94.77 and 64.52 MHz, respectively.
4049/0/268
0.0504/0.0985
5090/6/334
0.0372/0.0816
R1, wR2 (all data)
Goodness of
fit on F2
0.0736/0.1125
1.091
0.0476/0.0955
1.089
192 ꢀC (dec.)). Anal. calcd. for C44H36N4P2PtSe2: C, 51.02; H, 3.50, N;
5.41%. Found: C, 50.85; H, 3.36; N; 5.52%. 1H NMR (CDCl3)
: 6.80
d
(br, C4H3N2), 7.33e7.67 (m, Ph), 8.25 (br, C4H3N2); 31P{1H} NMR
Chemical shifts are relative to internal chloroform peak for 1H, 13
{1H} NMR spectra and external 85% H3PO4 for 31P NMR, external
Ph2Se2
463 ppm relative to Me2Se) in CDCl3 for 77Se{1H} NMR,
external [Te(dtc)2] in CDCl3
C
(CDCl3)
d
: 20.3 [(1J(PteP) ¼ 2792 Hz)], 195Pt{1H} NMR (CDCl3)
d
: ꢁ5120 [(1J(PteP) ¼ 2778 Hz)]; on prolonged standing in solution
gave [Pt{h
2-SeC4H3N2}{SeC4H3N2}(PPh3)] (2a): 31P{1H} NMR
(CDCl3)
(CDCl3)
(d
d
: 7.4 [(1J(PteP) ¼ 3873 Hz)], 29.2 (OPPh3), 195Pt{1H} NMR
(
d
¼ 440 ppm relative to Me2Te;
dtc ¼ N,N-diethyldithiocarbamate) for 125Te{1H} NMR spectra and
Na2PtCl6 in D2O for 195Pt NMR. Elemental analyses were carried out
on a Thermo Fischer Flash EA1112 CHNS analyzer.
d
: ꢁ4409 (d, 1J(PteP) ¼ 3886 Hz)].
2.1.2. Preparation of [Pt{SeC4H(4,6-Me)2N2}2(PPh3)2] (1b)
Intensity data for [Pt(SeC4H3N2)2(PPh3)2] (1a) and [Pd{h2
-
Prepared in a similar fashion adopting above method (Section
2.1.1) for the synthesis of 1a, and recrystallized from
dichloromethaneehexane mixture as yellow crystals (yield 103 mg,
74%; mp: 208 ꢀC (dec.)). Anal. calcd. for C48H44N4P2PtSe2: C, 52.80; H,
SeC4H3N2}{SeC4H3N2}(PPh3)] (3a) were collected on a Rigaku
MM007 RA equipped with a Mercury CCD diffractometer using
MoKa radiation at 93(2) K so that qmax ¼ 27.5ꢀ. The structures were
solved by direct methods [32] and refinement was on F2 using data
that had been corrected for absorption effects with an empirical
procedure [33]. Non-hydrogen atoms were modelled with aniso-
tropic displacement parameters, hydrogen atoms in their calcu-
lated positions. Molecular structures were drawn using ORTEP [34].
Crystallographic and structural determination data are listed in
Table 1.
4.06, N; 5.13%. Found: C, 52.31; H, 4.21; N; 5.28%. 1H NMR (CDCl3)
d:
2.18 (s, Me), 6.32 (s, CH-5), 7.29 (br, Ph), 7.86 (br, C4HN2); 31P{1H}
NMR (CDCl3)
d
: 21.8 [(1J(PteP) ¼ 2831 Hz)]; onprolonged standing in
solution gave [Pt{h
2-SeC4H(4,6-Me)2N2}{SeC4H(4,6-Me)2N2}(PPh3)]
(2b) 31P{1H} NMR (CDCl3)
(OPPh3), ꢁ5.5 ppm (PPh3).
d
: 5.5 [(1J(PteP) ¼ 4064 Hz)], 29.2
2.1.3. Preparation of [Pd{
To a benzene solution (10 cm3) of (SeC4H3N2)2 (48 mg,
0.15 mmol),
solution (30 cm3) of [Pd(PPh3)4] (168 mg,
h
2-SeC4H3N2}{SeC4H3N2}(PPh3)] (3a)
2.1. Syntheses of complexes
a
2.1.1. Preparation of [Pt(SeC4H3N2)2(PPh3)2] (1a)
0.15 mmol) in the same solvent was added with continuous stir-
ring for 4 h at room temperature. The solvent was evaporated
under vacuum and the residue was washed thoroughly with
diethyl ether to remove liberated triphenylphosphine and
was recrystallized from dichloromethane to afford red crystals of
the title complex (yield 75 mg, 75%, m.p. 169 ꢀC). Anal. calcd.
for C26H21N4PPdSe2: C, 45.60; H, 3.09, N; 8.18%. Found: C, 45.73;
To a benzene solution (15 cm3) of (SeC4H3N2)2 (38 mg,
0.12 mmol) a solution (30 cm3) of [Pt(PPh3)4] (140 mg, 0.11 mmol)
in the same solvent was added with stirring and the contents were
stirred for 5 h at room temperature. The solvent was evaporated in
vacuo and the residue was washed thoroughly with hexane fol-
lowed by diethyl ether to remove liberated phosphine. The residue
was extracted with dichloromethane, filtered and passed through
a Florisil column. The ensuing solution on refrigeration at ꢁ5 ꢀC
afforded yellow crystals of the title complex (yield 82 mg, 70% m.p.,
H, 3.30; N; 7.89%. 1H NMR (CDCl3)
d: 6.73 (t, 4.8 Hz, C4H3N2), 7.37
(br, PPh3), 8.20 (d, 4.8 Hz, C4H3N2); 31P{1H} NMR (CDCl3)
32.9 ppm.
d:

182
R.S. Chauhan et al. / Journal of Organometallic Chemistry 717 (2012) 180e186
2.1.4. Preparation of [Pd{
Me)2N2}(PPh3)] (3b)
h
2-SeC4H(4,6-Me)2N2}{SeC4H(4,6-
C, 46.91; H, 3.78; N; 5.72%. 1H NMR (CDCl3)
d: 1.97 (s, Me),
2.13e2.20 (m, ePCH2), 6.22 (s, C4HN2), 7.32 (br) 7.87 (m, PPh2); 31
P
Prepared similar to 3a and recrystallized from dichloromethane
gave red crystals (yield 65 mg, 68%, m.p. 182 ꢀC). Anal. calcd. for
C30H29N4PPdSe2: C, 48.63; H, 3.94, N; 7.56%. Found: C, 48.28; H,
{1H} NMR (CDCl3)
d
: 45.7 [(1J(PteP) ¼ 3039 Hz)].
2.1.9. Preparation of [Pt{TeC4H(4,6-Me)2N2}2(dppe)] (5c)
3.78; N; 7.63%. 1H NMR (CDCl3)
d
: 2.23 (s, Me), 6.41 (s, C4HN2), 7.28
(d, Ph), 7.61 (br, Ph); 31P{1H} NMR (CDCl3) : 32.7 ppm; 77Se{1H}
NMR (CDCl3) : 210 ppm.
Prepared and recrystallized similar to above method as a yellow
powder (yield 106 mg, 68%, mp: 163 ꢀC (dec)). Anal. calcd. for
C38H38N4P2PtTe2: C, 42.94; H, 3.60; N, 5.27%. Found: C, 43.12; H,
d
d
3.48; N, 5.51%. 1H NMR (CDCl3)
d: 2.16 (m, ePCH2), 2.42 (s, Me), 6.22
2.1.5. Preparation of [Pt{SeC4H3N2}2(dppe)] (4a)
(s, C4HN2), 7.31(br), 7.88 (br)(Ph); 31P{1H} NMR (CDCl3)
[1J(PteP) ¼ 2978 Hz] ppm.
d: 45.8
To a benzene suspension (10 cm3) of [PtCl2(dppe)] (90 mg,
0.13 mmol) was added a methanolebenzene solution (10 cm3) of
NaSeC4H3N2 [freshly prepared from (SeC4H3N2)2 (50 mg,
0.16 mmol) in benzene and NaBH4 (12 mg, 0.32 mmol) in meth-
anol]. The reactants were stirred for 5 h at room temperature to
give a yellow solution. The solvents were removed under vacuum
and the residue was washed with diethyl ether and dried under
reduced pressure. The product was extracted with dichloro-
methane, filtered and passed through a Florisil column. The
resulting solution was concentrated (5 cm3) under vacuum which
on slow evaporation at room temperature gave a yellow powder
(yield 79 mg, 64%, mp: 129 ꢀC). Anal. calcd. for C34H30N4P2PtSe2: C,
44.89; H, 3.32; N, 6.16%. Found: C, 45.34; H, 3.23; N, 5.89%. 1H NMR
2.1.10. Preparation of [Pt{SeC4H(4,6-Me)2N2}2(dppp)] (5d)
Prepared in a similar fashion to 5a and recrystallized from
dichloromethane as yellow powder (yield 85 mg, 64%, mp:
121 ꢀC(dec.)). Anal. calcd. for C39H40N4P2PtSe2: C, 47.81; H, 4.12; N,
5.72%. Found: C, 47.69; H, 4.28; N, 5.95%. 1H NMR (CDCl3)
d: 1.89(br),
2.49(br)(CH2), 2.40 (s, Me), 6.33 (s, C4HN2), 7.33 (br), 7.83 (br) (Ph);
31P{1H} NMR (CDCl3)
d
: ꢁ5.0 [1J(PteP) ¼ 2887 Hz].
2.1.11. Preparation of [Pt{TeC4H(4,6-Me)2N2}2(dppp)] (5e)
Prepared and recrystallized in a similar fashion to 5a, brown
powder (yield 101 mg, 65%, mp: 174 ꢀC (dec)). Anal. calcd. for
C39H40N4P2PtTe2: C, 43.49; H, 3.74; N, 5.20%. Found: C, 43.92; H,
(CDCl3) d: 2.13e2.37 (br, ePCH2), 6.45 (br, C4H3N2), 7.67e7.85 (m,
Ph), 8.54 (br, pym); 31P{1H} NMR (CDCl3)
d:
46.1
3.89; N, 4.89%. 1H NMR (CDCl3)
d: 1.96 (br), 2.57 (br) (CH2), 2.43 (s,
[1J(PteP) ¼ 3090 Hz] ppm. The latter in CDCl3 solution on pro-
longed period afforded yellow crystals of a trinuclear complex of
the composition, [Pt3Se2(dppe)3]Cl2 (6a) (mp: 268 ꢀC (dec)). Anal.
calcd. for C78H72Cl2P6Pt3Se2: C, 46.62; H, 3.61%. Found: C, 47.12; H,
Me), 6.40 (s, C4HN2), 7.32(br), 7.89 (br) (Ph); 31P{1H} NMR (CDCl3)
d
: ꢁ6.3 [1J(PteP) ¼ 2825 Hz] ppm. When a CDCl3 solution of the
complex was left for more than 24 h, red crystals of 6c (31P
NMR ¼ ꢁ13.5 ppm) were formed, analysis and NMR data were
consistent with other preparations.
3.79%. 1H NMR (CDCl3) : 7.22e7.70 (m, Ph); 31P{1H} NMR (CDCl3)
d d:
38.7 [1J(PteP) ¼ 3244 Hz].
2.1.12. Preparation of [Pt3(m-Te)2(dppe)3]Cl2 (6b)
2.1.6. Preparation of [Pt{SeC4H3N2}2(dppp)] (4b)
To a benzene suspension (14 cm3) of [PtCl2(dppe)] (120 mg,
0.18 mmol) was added a methanolebenzene solution (10 cm3) of
NaTeC4H3N2 [freshly prepared from (TeC4H3N2)2 (75 mg,
0.18 mmol) in benzene and NaBH4 (14 mg, 0.37 mmol) in meth-
anol]. The mixture was stirred for 5 h whereupon an orange solu-
tion was obtained. The solvents were removed under reduced
pressure. The residue was washed thoroughly with diethyl ether
and dried under vacuum. The product was extracted with
dichloromethane, filtered and passed through a Florisil column.
The resulting solution was concentrated (5 cm3) under vacuum and
hexane (0.5 cm3) was added which on refrigeration at ꢁ5 ꢀC
afforded an orange powder (yield 75 mg, 59%, mp: 167 ꢀC (dec)).
Anal. calcd. for C78H72Cl2P6Pt3Te2: C, 44.47; H, 3.44%. Found: C,
Prepared similar to 4a and recrystallized from dichloromethane
as a yellow powder (yield 87 mg, 70%, mp: 183 ꢀC(dec.)). Anal.
calcd. for C35H32N4P2PtSe2: C, 45.51; H, 3.49; N, 6.06%. Found: C,
45.67; H, 3.55; N, 5.98%. 1H NMR (CDCl3)
d: 1.95 (br), 2.51 (br)(CH2),
6.79e8.48 (br, m, C4H3 and Ph); 31P{1H} NMR (CDCl3)
[1J(PteP) ¼ 2886 Hz] ppm.
d
: ꢁ5.9
2.1.7. Preparation of [Pt{TeC4H(4,6-Me)2N2}2(dppm)] (5a)
To a benzene suspension (10 cm3) of [PtCl2(dppm)] (120 mg,
0.18 mmol) was added a methanolebenzene solution (10 cm3) of
NaTeC4H(4,6-Me)2N2 [freshly prepared from {TeC4H(4,6-Me)2N2}2
(90 mg, 0.19 mmol) in benzene and NaBH4 (15 mg, 0.40 mmol) in
methanol]. The mixture was stirred for 6 h whereupon a turbid
orange solution was formed. The solvents were decanted and the
precipitate was washed thoroughly with diethyl ether and extrac-
ted with dichloromethane, filtered, and passed through a Florisil
column. The resulting solution was concentrated (5 cm3) under
vacuum and hexane (0.5 cm3) was added which on refrigeration
at ꢁ5 ꢀC afforded orange crystals (yield 139 mg, 72%, mp: 129 ꢀC
(dec)). Anal. calcd. for C37H36N4P2PtTe2: C, 42.36; H, 3.46; N, 5.34%.
44.10; H, 3.63%. 1H NMR (CDCl3)
d: 2.47 (m, ePCH2), 6.98e7.45 (m,
Ph); 31P{1H} NMR (CDCl3)
d
: 40.8 [1J(PteP) ¼ 3144 Hz] ppm.
2.1.13. Preparation of [Pt3(m-Te)2(dppp)3]Cl2 (6c)
Prepared
similar
to 6b and recrystallized
from
dichloromethaneediethyl ether mixture as red crystals (yield
64 mg, 62%, mp: 182 ꢀC (dec)). Anal. calcd. for C81H78Cl2P6Pt3Te2: C,
45.28; H, 3.66%. Found: C, 45.44; H, 3.42%. 1H NMR (CDCl3)
d: 2.51
Found: C, 42.28; H, 3.43; N, 5.21%. 1H NMR (CDCl3)
d
: 2.35 (s, Me),
(br, ePCH2), 2.95 (br, CH2), 7.13e7.21 (m, Ph), 7.40e744 (m, Ph), 7.78
4.38 (t, 2J(PeH) ¼ 10.2 Hz, 3J(PteH) ¼ 55 Hz, ePCH2), 6.21 (s,
(br, Ph); 31P{1H} NMR (CDCl3)
d
: ꢁ13.0 [1J(PteP) ¼ 2980 Hz] ppm.
C4HN2), 7.16e7.31 (m, Ph), 7.86 (br, Ph); 31P{1H} NMR (CDCl3)
d
: ꢁ50.1 [1J(PteP) ¼ 2512 Hz]; 125Te{1H} NMR (CDCl3)
d
: ꢁ32
2.1.14. Preparation of [Pd3(m-Se)2(dppe)3]Cl2 (7a)
[1J(PteTe) ¼ 1034 Hz] ppm.
Prepared similar to 6b using [PdCl2(dppe)] (96 mg, 0.17 mmol)
and either NaSeC4H(4,6-Me)2N2 [prepared from {SeC4H(4,6-
Me)2N2}2 (62 mg, 0.17 mmol) in benzene and NaBH4 (14 mg,
0.37 mmol) in methanol] or NaSeC4H3N2 [prepared from
(SeC4H3N2)2 (54 mg, 0.17 mmol) in benzene and NaBH4 (13.3 mg,
0.35 mmol) in methanol] and extracted with dichloromethane
which on slow evaporation gave an orange crystalline solid in
52e56% yield (m.p. 293 ꢀC (dec.)). Microanalysis and NMR data for
2.1.8. Preparation of [Pt{SeC4H(4,6-Me)2N2}2(dppe)] (5b)
Prepared similar to 4a using [PtCl2(dppe)] (96 mg, 0.14 mmol)
and NaSeC4H(4,6-Me)2N2 [freshly prepared from {SeC4H(4,6-
Me)2N2}2 (53 mg, 0.14 mmol) in benzene and NaBH4 (12 mg,
0.32 mmol) in methanol] in yield 67% (93 mg), mp: 176 ꢀC (dec).
Anal. calcd. for C38H38N4P2PtSe2: C, 47.26; H, 3.97, N; 5.80%. Found:

R.S. Chauhan et al. / Journal of Organometallic Chemistry 717 (2012) 180e186
183
R
N
PPh3
PPh3
Ph3P
Ph3P
M
R
N
Se
)
2
2 PPh3
R
N
N
R
Se
PPh3
Ph3P
Se
M
Pt
Pt
R
H
Me
M
(1a)
(1b)
R
N
R
N
(1)
M = Pd
PPh3
M = Pt
Se
N
Ph3P
Se
Ph3P
Se
2-SeC4H3N2}{SeC4H3N2}(PPh3)]$CH2Cl2 (3a$CH2Cl2)
Pd
Fig. 2. ORTEP diagram of [Pd{
with atomic number scheme. The ellipsoids were drawn at 50% probability level. The
solvent molecule is omitted.
h
Pt
N
N
Se
N
R
R
N
R
N
R
R
R
N
R
N
R
2.1.15. [Pd3(m-Se)2(dppp)3]Cl2 (7b)
(3)
(2)
Prepared, extracted with dichloromethane and recrystallized in
a similar fashion to 7a using [PdCl2(dppp)] and NaSeC4H3N2 or
NaSeC4H(4,6-Me)2N2 as yellow crystalline solid in 70% yield (mp:
275 ꢀC (dec)). Anal. calcd. for C81H78Cl2P6Pd3Se2: C, 54.49, H, 4.40%.
Found: C, 54.71; H, 4.73%. 1H NMR (CDCl3) 2.85 (br, ePCH2), 3.2
(br, eCH2), 6.38e7.16 (m, Ph), 7.47e7.59 (br, Ph), 7.77e7.84 (m, Ph);
R
H
R
H
(2a)
(3a)
Me (2b)
Me (3b)
Scheme 1. Oxidative addition reactions of [M(PPh3)4] (M
selenopyrimidines.
¼
Pd or Pt) with 2-
31P{1H} NMR (CDCl3)
d: ꢁ3.0 ppm.
2.1.16. [Pd3(
Prepared in a similar fashion as 7a adopting method (i) in 61%
m-Te)2(dppe)3]Cl2 (7c)
the samples isolated from these preparations were similar. Anal.
calcd. for C78H72Cl2P6Pd3Se2: C, 53.74, H, 4.16%. Found: C, 54.01; H,
4.39%. 1H NMR (CDCl3) 2.64 (br, ePCH2), 7.10 (t, 1.2 Hz, Ph),
yield as
a
red crystal. m.p. 193 ꢀC (dec.). Anal. calcd. for
C78H72Cl2P6Pd3Te2: C, 50.89; H, 3.94%. Found: C, 50.63; H, 3.79%. 1H
7.38e7.47 (m, Ph), 7.48e7.55 (m, Ph); 31P{1H} NMR (CDCl3)
d:
NMR (CDCl3) 2.40 (m, ePCH2), 7.40 (br), 7.79 (br) (Ph); 31P{1H} NMR
50.3 ppm.
(CDCl3) d: 46.3 ppm. Similarly, prepared in a manner to 7a method
(ii) using reaction of [PdCl2(dppe)] (101 mg, 0.18 mmol) with
NaTeC5H3N2 [prepared from (TeC5H3N2)2 (75 mg, 0.18 mmol) in
benzene and NaBH4 (14 mg, 0.37 mmole) in methanol] gave red
crystals in 63% (68 mg) yield (m.p. 193 ꢀC (dec.)). Anal. calcd. for
C78H72Cl2P6Pd3Te2: C, 50.89; H, 3.94%. Found: C, 51.13; H, 3.67%. 31
P
{1H} NMR (CDCl3)
d: 46.0 ppm.
2.1.17. [Pd3( -Te)2(dppp)3]Cl2 (7d)
m
Prepared in a similar fashion as 7a adopting method (i) in 72%
yield as red crystals. m.p. 212 ꢀC (dec.). Anal. calcd. for
C81H78Cl2P6Pd3Te2: C, 51.67; H, 4.18%. Found: C, 51.39; H, 4.23%. 1H
NMR (CDCl3) 2.95 (br, ePCH2), 2.51(br, eCH2), 7.14e7.77 (m, Ph); 31
P
{1H} NMR (CDCl3)
d
: ꢁ11.0 ppm. Similarly, prepared in a manner to
7a method (ii) using reaction of [PdCl2(dppp)] (108 mg, 0.18 mmol)
Table 2
Selected bond lengths (Å) and angles (ꢀ) of [Pt(SeC4H3N2)2(PPh3)2]$2CH2Cl2
(1a$2CH2Cl2).
Pt1eP1
Pt1eSe1
Se1eC1
2.3128(19)
2.4491(11)
1.900(7)
Pt1eP1
Pt1eSe1
2.313(2)
2.4491
P1ePt1eP1
P1ePt1eSe1
P1ePt1eSe1
C1eSe1ePt1
179.999(1)
97.26(5)
82.74(5)
Se1ePt1eSe1
P1ePt1eSe1
P1ePt1eSe1
179.998(11)
82.74(5)
97.26(5)
Fig. 1. ORTEP diagram of [Pt(SeC4H3N2)2(PPh3)2]$2CH2Cl2 (1a$2CH2Cl2) with atomic
number scheme. The ellipsoids were drawn at 50% probability level. The solvent
molecules are omitted.
106.9(3)

184
R.S. Chauhan et al. / Journal of Organometallic Chemistry 717 (2012) 180e186
Table 3
the range of 117.2e167.5 ppm. The signal due to C-4,6 carbons is
significantly deshielded (w167 ppm) in dimethyl substituted
dichalcogenides as compared to its position in unsubstituted
derivatives (w158 ppm). The C-2 (or CeE) carbon signal in dis-
elenided (w166 ppm) is considerably deshielded with respect to
the corresponding ditellurides (w150 ppm) owing to the difference
in their electronegativity and polarizability.
Selected bond lengths (Å) and angles (ꢀ) of [Pd{ 2-SeC4H3N2}{SeC4H3N2}(PPh3)].
h
CH2Cl2 (3a$CH2Cl2).
Pd1eP1
Pd1eSe1
Pd1eSe2
Pd1eN2
N2ePd1eP1
P1ePd1eSe1
P1ePd1eSe2
N2ePd1eSe1
Se2ePd1eSe1
N2ePd1eSe2
2.2310(13)
2.4394(7)
2.4341(7)
2.118(4)
Se1eC1
Se2eC5
N2eC1
1.891(4)
1.917(5)
1.349(6)
170.76(11)
100.66(4)
90.90(4)
71.01(10)
168.37(2)
97.37(10)
C1eSe1ePd1
C1eN2ePd1
C5eSe2ePd1
N1eC1eSe1
N2eC1eSe1
N1eC1eN2
77.47(14)
102.3(3)
96.38(14)
125.5(3)
109.2(3)
125.3(4)
3.2. Reactions of [M(PPh3)4] with di(2-pyrimidyl)diselenides
The oxidative addition reactions of [M(PPh3)4] with dipyr-
imidyldiselenides proceed smoothly to afford complexes of the
type trans-[Pt{SeC4H(4,6-R)2N2}2(PPh3)2] (1) (when M ¼ Pt) and
[Pd{h
2-SeC4H(4,6-R)2N2}{SeC4H(4,6-R)2N2}(PPh3)]
(3)
(when
with NaTeC5H3N2 [prepared from (TeC5H3N2)2 (77 mg, 0.19 mmol)
in benzene and NaBH4 (15 mg, 0.39 mmol) in methanol] gave red
crystals in 69% (79 mg) yield (m.p. 212 ꢀC (dec.)). Anal. calcd. for
M ¼ Pd) (Scheme 1). Both theoretical [35] and experimental [36,37]
investigations on oxidative addition reactions of [Pt(PR3)4] with
diorgano diselenides have shown that initially
a
cis-
C81H78Cl2P6Pd3Te2: C, 51.67; H, 4.18%. Found: C, 51.54; H, 4.04%. 31
P
[Pt(SeAr)2(PPh3)2] is formed which is subsequently isomerised to
a thermodynamically stable trans product. Isolation of 1 as a trans
isomer in the present study indicates that the isomerisation of cis
form to trans is facile. The oxidative addition reactions of
[Pd(PPh3)4] with diorgano diselenides are known to yield binuclear
{1H} NMR (CDCl3)
d: ꢁ11.0 ppm.
3. Results and discussion
3.1. Synthesis of ligands
complexes, [Pd2(SeAr)2(m-SeAr)2(PPh3)2] exclusively [17e19].
However, in the present case, internal functionalization of the
selenolate aids in chelation of the ligand. Based on the earlier work
[17e19] and from this study it can be inferred that the oxidative
addition reaction of R20 E2 (E ¼ S or Se) on [Pd(PR3)4] also yields
initially a mononuclear complex, Pd(ER0)2(PR3)2, which dissociates
in solution to PR3 and a three-coordinate palladium species,
“Pd(ER0)2(PR3)”. The latter species depending on the nature of R0
group on chalcogenolate ligand either dimerizes, when R0 is simple
alkyl or aryl group, or gives a monomeric chelate complex when R0
Treatment of 2-chloropyrimidine with Na2E2 (E ¼ Se, Te) in
watereethanol mixture afforded not only a reddish diselenide but
also yellow crystals of monoselenide whereas in case of tellurium
only dark red (R ¼ H) or blue crystals (R ¼ Me) of ditellurides were
obtained exclusively.
The 1H NMR spectra of all the ligands displayed expected
resonances and peak multiplicities. The 13C NMR spectra of dis-
elenides and ditellurides displayed peaks due to pyimidyl carbon in
P
P
dppm
dppe
dppe
dppp
dppp
(5a)
(5b)
(5c)
(5d)
(5e)
[PtCl2(P P)]
(5)
(i) in benzene-methanol
(ii) extraction in CH2Cl2
On leaving (5e) in
CH2Cl2/CHCl3 solution
SeNa
On leaving (4a) in CH2Cl2/CHCl3
solution for recrystallization
2Cl
(4)
(6)
P
P
P
P
dppe
dppp (4b)
(4a)
dppe
dppe
dppp
(6a)
(6b)
(6c)
Scheme 2. Reactions of [PtCl2(PXP)] (PXP ¼ dppe or dppp) with sodium pyrimidyl chalcogenolate.

R.S. Chauhan et al. / Journal of Organometallic Chemistry 717 (2012) 180e186
185
atom. The trans-P2Se2 donor set defines the coordination environ-
ment around the platinum atom. The two selenolate groups adopt
an anti configuration. The PteSe distances (2.4491(11) Å) are
similar to those reported for the known [Pt(SeR0)2(PR3)2]; trans-
[Pt(SePh)2(PPh3)2]
(2.417(3),
2.419(3)
Å)
[36],
trans-
[Pt(SeTh)2(PPh3)2] (2.4629(1) Å and 2.465(1) Å) [17] and trans-
[Pt(SePh)2(PR3)2] (2.461(1) Å for R ¼ Et and 2.463(3) Å for R ¼ Bu)
[18]. The PteP distances are in good agreement with those reported
for [Pt(SeR0)2(PR3)2] complexes [17,18,35]. The two acute (82.74(5)ꢀ)
and obtuse (97.26(5)ꢀ) PePteSe angles can be compared with
trans-[Pt(SeTh)2(PPh3)2] (w83 and w96ꢀ), but differ from phenyl-
selenolate derivatives, trans-[Pt(SePh)2(PR3)2] (R ¼ Et, Bu, Ph) (w86
and w94ꢀ) [18,35,37].
The palladium atom in 3a acquires distorted square planar
geometry defined by P, N, Se2 donor atoms, the neutral donor atoms
(P and N) being trans. One of the selenolate ligand forms a four-
membered chelate ring while the other selenolate is bound to
palladium in a monodentate fashion. The four-membered chelate
ring and the pyrimidyl ring are nearly co-planar. The two PdeSe
distances are similar and are in agreement with those reported in
literature, e.g. [Pd2(SeTh)4(PPh3)2] (PdeSe ¼ 2.465(av) Å) [17]. The
PdeN and PdeP distances are as expected, e.g. [PdCl(TeC5H3(Me)
N)(PPh3)] (PdeP ¼ 2.2420(15) and PdeN ¼ 2.085(4) Å) [38].
Fig. 3. 125Te{1H} NMR spectrum of [Pt{TeC4H(4,6-Me)2N2}2(dppm)] (5a).
contains an additional donor atom like nitrogen. Formation of such
a three coordinate palladium species may have implication during
palladium catalyzed addition of Ar2E2 to alkenes [15] and can be
substantiated by the fact that the palladium complexes derived
from chelated phosphines are inactive in these reactions [10]
because of their inability to give three coordinate palladium
complex.
3.3. Reactions of [MCl2(PXP)] with sodium 2-pyrimidyl
chalcogenolate
The 31P NMR spectra of 1 and 3 exhibited a singlet while reso-
nances for the former were flanked by 195Pt satellites. The magni-
tude of 1J(PteP) (w2800 Hz) is in conformity with trans
configuration of the complexes [17,18,35]. The 195Pt NMR spectrum
of 1a showed a triplet at ꢁ5120 ppm due to coupling with two
equivalent 31P nuclei. The 1 dissociated to platinum analogue (2) of
3 and triphenylphosphine in solution when left for a few hours. The
31P NMR spectra of 2 were considerably shielded and the magni-
tude of 1J(PteP) was also increased (w3900 Hz) with respect to 1.
The 195Pt NMR spectrum of 2a displayed a doublet due to coupling
with a 31P nucleus. The magnitude of 1J(PteP) indicates that the
phosphine ligand is trans to the nitrogen atom of the chelating
selenolate ligand [38].
Treatment of [PtCl2(PXP)] with NaSeC4H3N2 or NaEC4H(4,6-
Me)2N2 (E ¼ Se or Te) in benzeneemethanol mixture afforded
mononuclear
complexes
of
composition,
[Pt{EC4H(4,6-
R)2N2}2(PXP)] (4 and 5) (Scheme 2). The similar reaction with
NaTeC4H3N2 gave an orange powder which after extraction with
dichloromethane afforded tellurido-bridged trinuclear complexes,
[Pt3(m
-Te)2(PXP)3]$2Cl (6) (PXP ¼ dppe (6b) and dppp (6c)). When
the mononuclear complexes 4a and 5e were left in halogenated
solvents (CDCl3 or CH2Cl2) for several hours, crystals of 6 were
isolated. The 31P NMR chemical shifts and 1J(PteP) values for 6 are
in conformity with the reported values [39,40]. The formation of
telluride-bridged complex 6 either from 5e in CDCl3 or in the
reaction between PtCl2(dppe) and NaTeC4H3N2 takes place via
a facile TeeC bond cleavage.
The molecular structures of [Pt(SeC4H3N2)2(PPh3)2]$2CH2Cl2
(1a$2CH2Cl2) (Fig. 1) and [Pd{
h
2-SeC4H3N2}{SeC4H3N2}(PPh3)].
The 31P NMR spectra of 4 and 5 displayed single resonances
flanked by 195Pt satellites. The observed 1J(PteP) values are
consistent with the values reported for [Pt(EAr)2(PXP)] complexes
[2,38,41,42]. The 125Te{1H} NMR spectrum (Fig. 3) of [Pt{TeC4H(4,6-
Me)2N2}2(dppm)] displayed a three lines centred at ꢁ32 ppm with
CH2Cl2 (3a$CH2Cl2) (Fig. 2) were established by X-ray diffraction
analyses. Both the complexes crystallized with solvent molecule(s)
(CH2Cl2). Selected interatomic parameters are given in Tables 2 and
3. The 1a comprises of a distorted square planar central platinum
(i) benzene - methanol
(ii) extraction with CH2Cl2
2 NaE
[PdCl2(P P)]
2Cl
R = H, Me
P
P
E
dppe (7a)
Se
Se
dppp
(
7b)
dppe (7c)
dppp
Te
Te
(7d)
Scheme 3. Reactions of [PdCl2(PXP)] (PXP ¼ dppe or dppp) with sodium 2-pyrimidyl chalcogenolates.

186
R.S. Chauhan et al. / Journal of Organometallic Chemistry 717 (2012) 180e186
platinum satellites (1J(PteTe) ¼ 1034 Hz). The observed pattern is in
fact a second order spectrum originating due to coupling with cis
and trans phosphorus nuclei.
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The reactions between [PdCl2(PXP)] and NaEC4H(4,6-R2)N2
(E ¼ Se or Te; R ¼ H or Me) in benzeneemethanol mixture followed
by extraction with dichloromethane invariably gave trinuclear
chalcogenido-bridged palladium complexes, [Pd3(m
-E)2(PXP)3]2Cl
(7) (E ¼ Se or Te; PXP ¼ dppe or dppp) in 52e72% yield (Scheme 3).
The 1H NMR spectra were devoid of any EC4H(4,6-R2)N2 proton
resonances as expected. The 31P NMR chemical shifts for 7 are in
accordance with BPh4/PF6 salts of [Pd3(m
-E)2(PXP)3]2þ cations re-
ported earlier [39,43,44]. These complexes have been isolated in
low yields by a reaction between [PdCl2(PXP)] and NaEH (E ¼ Se or
Te) in the presence of NaBPh4 or NaPF6 [39,43]. The selenido-
bridged complexes have been isolated in fairly good yield through
unprecedented cleavage of CeSe bond of selenocarboxylate during
the reaction of [Pd(SeCOAr)2(PXP)] with [PdCl2(PXP)] in the pres-
ence of NaBPh4 in CH2Cl2eMeOH solvent mixture [44]. In an
alternative route 7a has been prepared in 52% yield by Morley et al.
by the reaction of [Pd(dppe)2] with selenium powder in CH2Cl2
[40].
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4. Conclusions
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439e446.
Oxidative addition reactions of bis(2-pyrimidyl)diselenides with
M(PPh3)4 afforded [Pt{SeC4H(4,6-R)2N2}2(PPh3)2] in the case of
platinum and [Pd{SeC4H(4,6-R)2N2}{h
2-SeC4H(4,6-R)2N2}(PPh3)]
when M ¼ Pd. Substitution reactions between [PtCl2(PXP)] and
2-pyrimidylchalcogenolate yielded mononuclear complexes, [Pt
{EC4H(4,6-R2)N2}2(PXP)] which are converted in to trinuclear
complexes, [Pt3(
m
-E)2(PXP)3]$2Cl when left in CDCl3/CH2Cl2 solu-
tion for a long time. Similar reactions with [PdCl2(PXP)], after
dissolution in CH2Cl2, invariably afforded [Pd3(m
-E)2(PXP)3]$2Cl.
[31] A.S. Hodage, P. Prabhu, P.P. Phadnis, A. Wadawale, K.I. Priyadarsini, V.K. Jain,
Acknowledgements
Unpublished results.
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Approximation, Rigaku Corporation, 3-9-12 Matsubara, Akishima, Japan,
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Oak Ridge TN, 1976.
One of the authors (RSC) is grateful to DAE for the award of SRF.
We thank Drs. T. Mukherjee and D. Das for encouragement of this
work.
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