Cis configured bis phosphine platinum(II) chalcogenolate complexes: Structures, NMR and computational studies

Article abstract of DOI:10.1016/j.jorganchem.2013.03.030

Reactions of [PtCl₂(P^a?P)] (P ^a?P = dppm, dppe or dppp) with Pb(SMes)₂ and sodium arylchalcogenolates yielded mononuclear complexes of the type, cis-[Pt(EAr)₂(P^a?P)] [EAr = EMes (E = S, Se

Full text of DOI:10.1016/j.jorganchem.2013.03.030

Journal of Organometallic Chemistry 737 (2013) 40e46
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Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Cis configured bis phosphine platinum(II) chalcogenolate complexes: Structures,
NMR and computational studies
Rohit Singh Chauhan a, G. Kedarnath a, A. Wadawale a, D.K. Maity b, James A. Golen c,
,
Arnold L. Rheingold c, Vimal K. Jain a
*
a Chemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085, India
b Theoretical Chemistry Section, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085, India
c Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093-0358, United States
a r t i c l e i n f o
a b s t r a c t
Reactions of [PtCl2(PXP)] (PXP ¼ dppm, dppe or dppp) with Pb(SMes)2 and sodium arylchalcogenolates
yielded mononuclear complexes of the type, cis-[Pt(EAr)2(PXP)] [EAr ¼ EMes (E ¼ S, Se or Te;
Mes ¼ mesityl), Sepym (pym ¼ 2-pyrimidyl) or SepymMe2 (pymMe2 ¼ 4,6-dimethyl-2-pyrimidyl].
These complexes were characterized by elemental analyses and NMR (1H, 31P) spectroscopy. The mo-
lecular structures of [Pt(SeMes)2(dppp)]$½C6H6, [Pt(TeMes)2(dppp)]$3C6H6, [Pt(SeC4H3N2)2(dppm)]
and [Pt{SeC4H(4,6-Me2)N2}2(dppm)]$CH2Cl2 were established by single crystal X-ray diffraction ana-
lyses. An attempt has been made to rationalize the NMR data with the nature of chelated bis phosphine
Article history:
Received 7 January 2013
Received in revised form
6 March 2013
Accepted 13 March 2013
Keywords:
Platinum
Selenolate
Tellurolate
ligand, chalcogen atom and aryl substituent on the chalcogen atom. The energy difference (
DE),
calculated by DFT, is very small between various conformers. The calculated E between various con-
D
formers of mesitylthiolate dppp complex lies in the range of 0.1e1.0 kcal/mol; the same for mesi-
tylselenolate complex lies in the range of 0.5e2.2 kcal/mol and for mesityltellurolate complex it is in the
range of 1.0e3.0 kcal/mol.
NMR
X-ray
Density functional calculation
Ó 2013 Elsevier B.V. All rights reserved.
1. Introduction
slightly from each other, although complexes with the same two Pte
E distances are also reported. The difference in the two PteE dis-
Mononuclear cis configured palladium and platinum organo-
chalcogenolate complexes, cis-[M(ER0)2(PR3)2] are of considerable
interest as they are used as molecular tectons for constructing a va-
riety of bi- and high-nuclearity complexes [1e3] and are believed to
be catalytically active species in metal catalyzed CeE (E ¼ S or Se)
bond formation [4,5]. In the case of monodentate ER0 and PR3 ligands,
isomerization to the thermodynamically more stable trans form [6]
and polymerization to R0E-bridged species [7] are usually encoun-
tered. To circumvent these problems, chelating phosphines [8,9],
and/or chelating [10,11]/bulky [11] chalcogenolate ligands are
employed. The aryl groups on chalcogenolate ligands can mutually
adopt different orientations with respect to the metal square plane,
viz., anti form (A), syn form (B), aryl-rings coplanar with the
metal plane (C) and aryl planes perpendicular to metal plane (D)
(Scheme 1). In general distortions from these idealized conforma-
tions are usually encountered in the solid state (from X-ray crystal-
lography). The two PteE distances in cis-Pt(EAr)2(PXP) are often non-
equivalent as a consequence the two PteP distances are also differing
tances, irrespective of the nature of chalcogen atom, can be as large as
ꢀ
0.07 A (Supplementary material). Such differences are, however, not
evident from the 31P and 195Pt NMR spectra in solution and are
indicative of equivalence of the two 31P nuclei.
Inthelightoftheaboveandtogainfurtherinsightonthestructural
features of cis-[Pt(EAr)2(PXP)] complexes, we have chosen a sterically
hindered Ar (mesityl) as well as heterocyclic group containing nitro-
gen atoms (e.g., pyrimidyl). The latter small bite heterocyclic chalco-
genolate ligand shows several binding possibilities (viz. terminal E
bonding, E-bridging, N,E-chelating, N,E-bridging, N,E-chelating-cum-
E bridging or N,E-bridging-cum-E-bridging modes (E ¼ S, Se, Te))
[12,13]. The complexes with higher homologues (Se, Te) quite often
show remarkable differences inreactivitythanthecorresponding thio
derivatives [14e16]. Furthermore, the tellurolate complexes are
scantly investigated. Results of this work are reported herein.
2. Experimental
The compounds [PtCl2(PXP)] [PXP ¼ dppm (bis(diphenylphos-
phino)methane), dppe (1,2-bis(diphenylphosphino)ethane), dppp
(1,3-bis(diphenylphosphino)propane)] [17] and the ligand precursors
* Corresponding author. Tel.: þ91 22 25595095; fax: þ91 22 25505151.
E-mail addresses: arheingold@ucsd.edu (J.A. Golen), jainvk@barc.gov.in (V.K. Jain).
0022-328X/$ e see front matter Ó 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.jorganchem.2013.03.030

R.S. Chauhan et al. / Journal of Organometallic Chemistry 737 (2013) 40e46
41
[22]. Crystallographic and structural determination data are listed
in Table 1.
Full geometry optimization of mesityl chalcogenolate (S, Se and
Te) complexes of platinum has been carried out by applying a DFT
functional, namely, BP86. The BP86 is a generalized gradient
approximation (GGA) functional that combines Becke’s 1988 ex-
change functional with Perdew’s 1986 correlation functional. SARC-
ZORA basis sets for platinum, Gaussian type atomic basis functions,
6-31G(d) for H, C, P, S and Se atoms and 3-21G for Te atom are
applied for all the calculations. Basis sets for Pt and Se atoms were
obtained from Extensible Computational Chemistry Environment
Basis Set Database, Pacific Northwest National Laboratory [23]. The
quasi-NewtoneRaphson based algorithm has been applied to carry
out geometry optimization to locate the minimum energy structure
in each case. All these calculations have been carried out applying
GAMESS suit of ab initio programs on a LINUX cluster platform [24].
Scheme 1.
2.1. Syntheses of complexes
(SeMes)2 [18], (TeMes)2 [19], (SeC4H3N2)2, {SeC4H(4,6-Me)2N2}2 [16]
and [Pb(SMes)2] [20] were prepared by literature methods. All re-
actions were carried out under a nitrogen atmosphere in dry and
distilled analytical grade solvents at room temperature. The 1H and
31P{1H} NMR spectra were recorded on a Bruker Avance-II spec-
trometer operating at 300 and 121.49 MHz, respectively. Chemical
shifts are relative to internal chloroform (d 7.26) for 1H, external 85%
H3PO4 for 31P. Elemental analyses were carried out on a Thermo
Fischer Flash EA1112 CHNS analyzer.
Intensity data for [Pt(SeMes)2(dppp)]$½C6H6, [Pt(TeMes)2
(dppp)]$3C6H6, [Pt(SeC4H3N2)2(dppm)] and [Pt{SeC4H(4,6-Me2)
N2}2(dppm)]$CH2Cl2 were measured on a Bruker Apex-II, CCD
diffractometer with Mo-Ka radiation so that qmax ¼ 27.5ꢀ. The
structures were solved by direct methods [21] and refinement was
on F2 using data that had been corrected for absorption effects with
an empirical procedure. Non-hydrogen atoms were modelled with
anisotropic displacement parameters, hydrogen atoms in their
calculated positions. Molecular structures were drawn using ORTEP
2.1.1. [Pt(SMes)2(dppm)]
To a benzene suspension of [PtCl2(dppm)] (100 mg, 0.15 mmol)
was added a dichloromethane solution of [Pb(SMes)2] (82 mg,
0.16 mmol) with stirring which continued for 6 h at room tem-
perature whereupon a yellow turbid solution was formed. The
latter was centrifuged and passed through Celite and the filtrate
was concentrated under reduced pressure. The residue was
extracted with dichloromethane, filtered and passed through a
Florisil column. Hexane was added to the resulting solution to give
a yellow powder (yield 81 mg, 60%). Similarly [Pt(SMes)2(dppe)]
and [Pt(SMes)2(dppp)] were prepared. Pertinent data are given in
Table 2.
2.1.2. [Pt(SeMes)2(dppm)]
To a benzene suspension (15 cm3) of [PtCl2(dppm)] (120 mg,
0.18 mmol) was added a methanolebenzene solution (10 cm3) of
NaSeMes [prepared from (SeMes)2 (80 mg, 0.20 mmol) in benzene
Table 1
Crystallographic and structural determination data for [Pt(SeMes)2(dppp)]$½C6H6, [Pt(TeMes)2(dppp)]$3C6H6, [Pt(SeC4H3N2)2(dppm)], [Pt{SeC5H(4,6-Me)N2}2(dppm)]$
CH2Cl2.
Complex
[Pt(SeMes)2(dppp)]$½C6H6
[Pt(TeMes)2(dppp)] $3C6H6
[Pt(SeC4H3N2)2(dppm)]
[Pt{SeC5H(4,6-Me)2N2}2(dppm)]. CH2Cl2
Chemical formula
Formula wt.
C45H48P2PtSe2$½C6H6
1042.84
C45H48P2PtTe2$3C6H6
1335.39
C33H28N4P2PtSe2
895.54
C37H36N4P2Pt Se2$CH2Cl2
1036.57
Crystal size (mm3)
Radiation used for data collection
Crystal system
0.40 ꢁ 0.30 ꢁ 0.20
0.38 ꢁ 0.33 ꢁ 0.30
0.20 ꢁ 0.15 ꢁ 0.10
0.15 ꢁ 0.10 ꢁ 0.10
Mo-Ka
Mo-Ka
Mo-Ka
Mo-Ka
Monoclinic
P21/n
Orthorhombic
Pbcn
Monoclinic
C2/c
Orthorhombic
Pna21
Space group
Unit cell dimensions
ꢀ
a (A)
14.000(5)
22.376(7)
13.583(8)
90
98.25(4)
90
4211(3)
4
1.645
2.67e28.33
5.170/2060
ꢂ10 ꢃ h ꢃ 18
0 ꢃ k ꢃ 29
ꢂ17 ꢃ l ꢃ 17
11,879
20.927(3)
12.8611(16)
20.875(3)
90
90
90
5618.3(12)
4
1.578
1.86e25.37
3.610/2620
ꢂ24 ꢃ h ꢃ 25
ꢂ15 ꢃ k ꢃ 15
ꢂ25 ꢃ l ꢃ 25
40,961
48.245(2)
8.8359(4)
22.1322(10)
90
96.990(2)
90
9364.6(7)
12
1.901
1.70e25.44
6.960/5160
ꢂ58 ꢃ h ꢃ 57
ꢂ10 ꢃ k ꢃ 10
ꢂ26 ꢃ l ꢃ 26
61,532
15.8773(4)
14.4948(4)
16.7069(5)
90
90
90
3844.90(18)
4
1.791
2.57e25.85
5.798/2016
ꢂ19 ꢃ h ꢃ 19
ꢂ17 ꢃ k ꢃ 13
ꢂ20 ꢃ l ꢃ 20
28,372
ꢀ
b (A)
ꢀ
c (A)
a
b
g
(ꢀ)
(ꢀ)
(ꢀ)
3
ꢀ
Volume (A )
Z
rcalcd, g cmꢂ3
q
for data collection (ꢀ)
m
(mmꢂ1)/F(000)
Index range
No of reflections collected
No of independent reflection/no. of
9922/4457
5156/4527
8678/7319
7412/6610
observed reflections with I > 2sI
Data/restraints/parameters
9922/0/484
0.0474/0.0905
0.1702/0.1211
0.932
5156/0/308
0.0212/0.0474
0.0273/0.0509
1.042
8678/0/569
0.0264/0.0495
0.0375/0.0523
1.038
7412/1/447
0.0250/0.0513
0.0329/0.0538
1.042
Final R1,
R1, R2 (all data)
Goodness of fit on F2
uR2 indices
u

42
R.S. Chauhan et al. / Journal of Organometallic Chemistry 737 (2013) 40e46
Table 2
Physical, analytical and NMR data for [Pt(EAr)2(PXP)].
Complex
Recrystallization
solvent (% yield)
M.p. % Analysis: found (calcd.)
(ꢀC)
NMR data
1H NMR (
C
H
S or N
d
in ppm)
31P{1H} NMR
(1J(PteP) in Hz)
d
[Pt(SMes)2(dppm)]
[Pt(SeMes)2(dppm)]
CH2Cl2ehexane (60)
CH2Cl2ehexane (58)
172 58.12 (58.55) 5.23 (5.03) 7.71 (7.27) 2.03 (s, Me, 3H), 2.40 (s, Me, 6H), 4.18 (t, PCH2), ꢂ46.4 (2641)
6.28 (s, Mes), 7.31e7.51 (m), 7.92 (m)[Ph]
197 53.01 (52.93) 4.83 (4.55)
e
2.03 (s, 4-Me), 2.23 (d, 9.6 Hz, eCH2),
2.40 (s, 2,6-Me), 6.28 (s, 3,5-H), 7.28e7.31
(m, Ph), 7.40e7.49 (m, Ph)
ꢂ52.5 (2522)
[Pt(TeMes)2(dppm)]
Benzeneediethyl
ether (42)
181 48.62 (48.13) 4.44 (4.13)
e
2.03 (s, 4-Me), 2.17 (d, 0.9 Hz, eCH2), 2.22
(s, 2,6-Me), 6.46 (s, 3,5-H), 7.31e7.36
(m, Ph), 7.39e7.48 (m, Ph), 7.66 (m, Ph),
7.82e7.86 (m)
ꢂ57.4 (2422)
[Pt(SeC4H3N2)2(dppm)] CH2Cl2ehexane (67)
144 44.38 (44.25) 3.15 (3.15) 6.11 (6.25)
127 46.84 (46.69) 3.88 (3.81) 5.91 (5.89) 1.86 (s, Me), 4.46 (br, PCH2), 6.17 (s, pym),
7.35 (br), 7.93 (br) [Ph]
ꢂ50.8 (2770)
ꢂ49.9 (2685)
[Pt{SeC4H(4,6-Me2)
N2}2(dppm)]
CH2Cl2ehexane (74)
[Pt(SMes)2(dppe)]
CH2Cl2ehexane (64)
179 58.34 (58.98) 5.03 (5.17) 7.01 (7.15) 2.07 (s, 4-Me), 2.15 (s, 2,6-Me), 2.23e2.51
(m, eCH2), 6.39 (s, 3,5-H), 7.34e7.43
42.3 (2677)
(m, Ph), 7.63e7.70 (m, Ph)
[Pt(SeMes)2(dppe)]
[Pt(TeMes)2(dppe)]
CH2Cl2ediethyl
ether (62)
Acetoneediethyl
ether (51)
124 52.66 (53.39) 4.52 (4.68)
178 48.38 (48.61) 4.31 (4.27)
e
e
e
43.8 (2935)
47.9 (2810)
2.18 (s, 4-Me), 2.22e2.31 (m, eCH2), 2.34
(s, 2,6-Me), 6.28 (s, 3,5-H), 7.38e7.41
(m, Ph), 7.79e7.86 (m, Ph).
[Pt(SMes)2(dppp)]
[Pt(SeMes)2(dppp)]
[Pt(TeMes)2(dppp)]
Acetoneehexane (54)
CH2Cl2ehexane (69)
161 59.21 (59.39) 5.43 (5.31) 6.89 (7.04) 2.09 (s, Me), 2.33 (m, -PCH2), 2.48 (br, eCH2),
6.37 (s, 3,5-H), 7.32e7.38 (m, Ph), 7.74 (br, Ph)
ꢂ2.9 (2743)
ꢂ6.6 (2775)
ꢂ6.8 (2469)
168 54.09 (53.84) 4.66 (4.82)
e
2.10 (s, Me), 2.46 (br, eCH2), 6.45 (s, 3,5-H),
7.30e7.37 (m, Ph), 7.73 (br, Ph).
Benzeneediethylether (58) 132 49.21 (49.08) 4.37 (4.39)
e
2.17 (s, 4-Me), 2.22e2.42 (m, eCH2), 2.57
(s, 2,6-Me), 6.78 (s, 3,5-H), 7.39e7.59
(m, Ph), 7.75e7.81 (m, Ph).
and NaBH4 (16 mg, 0.42 mmol) in methanol]. The mixture was
stirred for 4 h, whereupon a clear yellow solution was obtained. The
solvents were evaporated under reduced pressure. The residue was
washed with hexane followed by diethyl ether. The product was
extracted with dichloromethane and passed through a Florisil
column which on slow evaporation gave yellow crystals of [Pt(Se-
Mes)2(dppm)]. Similarly all other selenolate complexes were
prepared.
3. Results and discussion
3.1. Synthesis and spectroscopy
Reactions of PtCl2(PXP) with either Pb(SMes)2 or 2 equiv of
NaEAr (E ¼ Se or Te) (prepared by reductive cleavage of EeE bond in
Ar2E2 by NaBH4 in methanolebenzene) gave mononuclear plat-
inum chalcogenolate complexes, [Pt(EAr)2(PXP)] [EAr ¼ EMes
2.1.3. [Pt(TeMes)2(dppm)]
To a benzene suspension (10 cm3) of [PtCl2(dppm)] (125 mg,
0.19 mmol) was added a methanolebenzene solution (10 cm3) of
NaTeMes [freshly prepared from (TeMes)2 (94 mg, 0.19 mmol) in
benzene and NaBH4 (15 mg, 0.40 mmol) in methanol]. The re-
actants were stirred for 5 h at room temperature to give a red so-
lution. The solvents were removed under vacuum and the residue
was washed with diethyl ether and dried under reduced pressure.
The product was extracted with benzene, filtered and passed
through a Florisil column. The resulting solution was concentrated
(5 cm3) under vacuum which on slow evaporation at room tem-
perature gave red crystals (yield 86 mg, 42%). Similarly all other
tellurolate complexes were prepared.
Table 3
ꢀ
ꢀ
Selected bond lengths (A) and angles ( ) of [Pt(SeMes)2(dppp)]$½C6H6.
Pt1eP1
Pt1eSe1
Se1eC1
P1ePt1eP2
P1ePt1eSe1
P1ePt1eSe2
C1eSe1ePt1
P1ePt1eSe1eC1
P1ePt1eSe2eC10
C1eSe1ePt1eSe2
2.246(2)
2.4251(11)
1.887(9)
97.14(9)
85.18(7)
161.68(7)
111.0(3)
ꢂ164.5(3)
ꢂ89.4(4)
ꢂ1.7(3)
Pt1eP2
Pt1eSe1
Se2eC10
Se1ePt1eSe2
P2ePt1eSe1
P2ePt1eSe2
C10ePt1eSe2
P2ePt1eSe1eC1
P2ePteSe2eC10
C10eSe2ePt1eSe1
2.238(2)
2.4353(13)
1.914(8)
88.65(4)
159.95(7)
94.56(7)
113.4(2)
97.9(4)
40.2(3)
ꢂ159.7(3)
Fig. 1. ORTEP drawing of [Pt(SeMes)2(dppp)]$½C6H6 with atomic number scheme.
Hydrogen atoms and the solvent molecule are omitted for clarity.

R.S. Chauhan et al. / Journal of Organometallic Chemistry 737 (2013) 40e46
43
two PteP and two PteSe distances (Table 3). However such dif-
ferences are not evident from NMR data. The 31P NMR spectrum of
this complex in CD2Cl2 solution at 700 MHz did not show any
noticeable change down to ꢂ45 ꢀC.
As is evident from Table 2, the order of coupling constant
for each chalcogen atom of EAr group follows the trend
dppm < dppp < dppe. The observed trend of coupling is in con-
formity with the earlier reports [8,25,26]. On keeping the bis
phosphine ligand fixed, the coupling constant followed the trend
Se > S ꢄ Te. Interestingly the
p-acidity (nucleophilicity) of chalco-
genolate ligand follows the sequence Te > Se [ S. The variation of
group on chalcogen atom resulted into a slight change in coupling
constant (less than 150 Hz) (Supplementary material). Attempts to
correlate these values with respect to the nature of Ar group
(electronic effect) were inconclusive as the contributions from steric
effect of different Ar groups could not be rationalized.
3.2. Crystal structures
Molecular structures of [Pt(SeMes)2(dppp)]$½C6H6, [Pt(TeMes)2
(dppp)]$3C6H6, [Pt(SeC4H3N2)2(dppm)] and [Pt{SeC4H(4,6-Me2)
N}2(dppm)]$CH2Cl2 were established by single crystal X-ray
diffraction analyses. ORTEP drawings with atomic numbering
scheme are depicted in Figs. 1e4 while selected inter-atomic pa-
rameters are given in Tables 3e6. Except [Pt(SeC4H3N2)2(dppm)],
these complexes crystallized with the solvent of crystallization.
There are two independent molecules of [Pt(SeC4H3N2)2(dppm)] in
the crystal lattice which differ slightly in inter-atomic parameters
from each other. The other complexes comprised of discrete
monomeric units.
Fig. 2. ORTEP drawing of [Pt(TeMes)2(dppp)]$3C6H6 with atomic number scheme.
Hydrogen atoms and the solvent molecule are omitted for clarity.
(E ¼ S, Se or Te; Mes ¼ mesityl), Sepym (pym ¼ 2-pyrimidyl) or
SepymMe2 (pymMe2 ¼ 4,6-dimethyl-2-pyrimidyl); PXP ¼ dppm,
dppe or dppp] as yellow crystalline solids. The reactions with lead
mesitylthiolate are quite facile affording desired products in fairly
good yield.
The 31P{1H} NMR spectra of these complexes displayed single
resonances which appeared in the expected range of the respective
chelating phosphine complexes of platinum [25]. The resonances
were flanked by 195Pt couplings. The magnitude of 1J(PteP) lies in
the range 2419e3090 Hz and depends on the nature of the
chelating phosphine ligand, chalcogen atom and to a some extent
on the nature of Ar group on chalcogen. The observed magnitude of
1J(PteP) is reduced significantly as compared to the values for the
corresponding [PtCl2(PXP)] indicating strong trans influence of the
organochalcogenolate ligand. The X-ray structural analysis of
[Pt(SeMes)2(dppp)] reveals that the complex has slightly different
The platinum atom in these complexes adopts a distorted square
planar geometry defined by two chalcogenolate ligands and the
chelating phosphine ligand in a cis configuration. The PteSe
ꢀ
ꢀ
(2.4182(5)e2.4914(5) A), PteTe (2.6394(3) A) and PteP (2.238(2)e
ꢀ
2.2710(8) A) distances can be compared with mononuclear plat-
inum chalcogenolate complexes, [Pt(EAr)2(PXP)] (E ¼ Se or Te)
[8,11,27,28]. The two PteTe distances in [Pt(TeMes)2(dppp)]$3C6H6
are essentially the same, whereas these are distinctly different in
ꢀ
[Pt(TePh)2(dppe)] (PteTe ¼ 2.6465(7), 2.6053(6) A) [28] and
ꢀ
[Pt(TeTh)2(dppe)] (PteTe ¼ 2.6594(9), 2.607(1) A) [28].
Fig. 3. ORTEP drawing of [Pt(SeC4H3N2)2(dppm)] with atomic number scheme.

44
R.S. Chauhan et al. / Journal of Organometallic Chemistry 737 (2013) 40e46
Fig. 4. ORTEP drawing of [Pt{SeC4H(4,6-Me2)N2}2(dppm)]$CH2Cl2 with atomic number scheme. Hydrogen atoms and the solvent molecule are omitted for clarity.
ꢀ
The PteP distance in [Pt(TeMes)2(dppp)]$3C6H6 (2.2710(8) A) is
Each of the two PteSe and two PteP distances, except molecule
b of [Pt(SeC4H3N2)2(dppm)] are distinctly different in selenolate
complexes while in molecule b of [Pt(SeC4H3N2)2(dppm)] the two
PteSe and PteP distances are the same. The PePteP and SeePteSe
angles in [Pt(SeC4H3N2)2(dppm)] [73.85(4)ꢀ, 85.559(16)ꢀ (molecule
a) and 74.09(6)ꢀ, 80.27(2)ꢀ (molecule b)] and [Pt{SeC4H(4,6-Me2)
N}2(dppm)]$CH2Cl2 (73.54(5)ꢀ, 79.633(17)ꢀ) can be compared
with the sulphur analogue, [Pt(SC4H3N2)2(dppm)] (73.73(3)ꢀ; Se
PteS ¼ 79.35(3)ꢀ) [13] and [Pt(SC5H4N)2(dppm)] (74.01(4)ꢀ; SePte
S ¼ 78.56(4)ꢀ) [12].
marginally longer than the selenium analogue, [Pt(Se-
Mes)2(dppp)]$½C6H6 (av. 2.242 A) indicating stronger trans influ-
ꢀ
ence of the tellurolate group. The EePteE angle in these complexes
lies in the range 79.633(17)ꢀe94.673 (13)ꢀ. The EeMeE angle in cis-
[M(EAr)2(PR3)2] (M ¼ Pd or Pt; E ¼ S, Se, Te) complexes varies be-
tween 78ꢀ and 101ꢀ [8,9,11,27,28] and is influenced by the orien-
tation of the aryl group on the chalcogen atom with respect to the
MeE bond [28].
Table 4
ꢀ
ꢀ
Selected bond lengths (A) and angles ( ) of [Pt(TeMes)2(dppp)]$3C6H6.
3.3. Theoretical study
Pt1eP1
Pt1eTe1
P1ePt1eP1
P1ePt1eTe1
P1ePt1eTe1
P1ePt1eTe1eC15
P1ePt1eTe10eC150
2.2710(8)
2.6394(3)
91.17(4)
169.734(19)
87.97 (2)
152.40(8)
67.03(14)
Te1eC15
2.141(3)
X-ray structural analyses for several dichalcogenolate com-
plexes show subtle differences in the conformations. However such
differences could not be diagnosed in solution even for the com-
plexes containing bulky aryl groups like mesityl. To understand
possible reasons for observed conformational variations, DFT cal-
culations were performed. Three minimum energy structures are
obtained in each of these three (S, Se or Te based mesityl chalco-
genolate with dppp as a co-ligand) cases with various possible
input structures for the three complexes based on different spatial
orientations of the ligands. Optimization of structures are carried
out applying a DFT functional, namely, BP86 which is known to
work well for platinum based complexes considering mixed atomic
basis functions. The optimized structures look similar and the final
optimized structures are displayed in Fig. 5. In case of thiolate and
selenolate complexes, conformers IA and IIA (where mesityl rings
Te1ePt1eTe1
C15eTe1ePt1
94.673(13)
108.15(8)
C15eTe1ePt1eTe10
ꢂ37.54(8)
Table 5
Selected bond lengths (A) and angles ( ) of [Pt(SeC4H3N2)2(dppm)].
ꢀ
ꢀ
Molecule a
Molecule b
Pt1eP1
Pt1eP2
Pt1eSe1
Pt1eSe2
Se1eC1
Se2eC5
2.2642(10)
2.2488(11)
2.4182(5)
2.4914(5)
1.903(4)
Pt2eP3
Pt2eSe3
Se3eC34
2.2603(11)
2.4537(5)
1.908(5)
1.920(5)
P1ePt1eP2
P1ePt1eSe1
P1ePt1eSe2
P2ePt1eSe1
P2ePt1eSe2
Se1ePt1eSe2
C1eSe1ePt1
C5eSe2ePt1
P1ePt1eSe1eC1
P1ePt1eSe2eC5
P2ePt1eSe1eC1
P2ePt1eSe2eC5
C1eSe1ePt1eSe2
C5eSe2ePt1eSe1
73.85(4)
P3ePt2eP30
P3ePt2eSe3
P3ePt2eSe30
Se3ePt2eSe30
C34eSe3ePt2
74.09(6)
176.25(4)
102.86(3)
80.27(2)
104.83(3)
169.50(3)
175.11(3)
95.67(3)
85.559(16)
110.62(13)
106.96(13)
15.01(14)
106.2(2)
Table 6
ꢀ
ꢀ
Selected bond lengths (A) and angles ( ) of [Pt{SeC5H(4,6-Me)N2}2(dppm)]$CH2Cl2.
111.71(14)
Pt1eP1
Pt1eSe1
Se1eC26
P1ePt1eP2
P1ePt1eSe1
P1ePt1eSe2
C26eSe1ePt1
P1ePt1eSe1eC26
P1ePt1eSe2eC32
C26eSe1ePt1eSe2
2.2550(12)
2.4568(6)
1.910(5)
Pt1eP2
Pt1eSe2
Se2eC32
Se1ePt1eSe2
P2ePt1eSe1
P2ePt1eSe2
C32eSe2ePt1
P2ePt1eSe1eC26
P2ePt1eSe2eC32
C32eSe2ePt1eSe1
2.2523(13)
2.4445(5)
1.908(5)
79.633(17)
175.81(4)
104.14(3)
113.64(14)
47.0(5)
73.54(5)
P3ePt2eSe3eC34
C34eSe3ePt2eSe30
C34eSe3ePt2eP3
8.82(15)
ꢂ169.08(15)
44.1(5)
102.85(3)
174.99(4)
111.96(15)
17.10(17)
64.3(4)
ꢂ58.7(4)
102.60(14)
ꢂ163.41(13)
ꢂ82.10(14)
2.48(17)
ꢂ175.66(16)
ꢂ158.45(16)

R.S. Chauhan et al. / Journal of Organometallic Chemistry 737 (2013) 40e46
45
Fig. 5. Optimized structures of different conformers of S, Se and Te based mesitylchalcogenolate (I: S, II: Se and III: Te) complexes of platinum calculated at DFT level of theory.
on chalcogen ligands are mutually perpendicular) are the most
stable ones. For tellurolate, IIIB conformer (mesityl rings are par-
allel to each other) is the most stable one. However, the energy
structures reported here and in the literature. The observed
orientation of the aryl group in the solid state may possibly due to
subtle crystal energy packing requirement. The DFT calculations
suggest that there is a very small energy difference among various
conformers which make them indistinguishable in solution.
difference (DE) is very small between conformers A and B in all the
three cases. For thiolate, selenolate and tellurolate complexes
D
E
between A and B conformers and that between A and C conformers
is calculated to be 0.1, 0.5 and 1.0 kcal/mol and 1.0, 2.2 and 3.1 kcal/
mol, respectively. Calculated geometrical parameters of the most
stable conformer are very close to that of the X-ray data (for sele-
nolate and tellurolate complexes). In each minimum energy
Acknowledgements
One of the authors(RSC) is grateful to DAE for the award ofSRF. We
thank Drs. T. Mukherjee and D. Das for encouragement of this work.
structure,
substitutedesubstituted) is observed to be stacked in parallel
fashion allowing interaction between aryl rings to provide
a pair of aryl rings (unsubstitutedesubstituted or
Appendix A. Supplementary material
pep
extra stability for the observed conformer of the complexes.
CCDC 916604 (for [Pt(SeMes)2(dppp)]$½C6H6), CCDC 916607
(for [Pt(TeMes)2(dppp)]$3C6H6), and 916606 (for [Pt{SeC4H(4,6-
Me2)N2}2(dppm)]$CH2Cl2) contain the supplementary crystallo-
graphic data for this paper. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre via www.
ccdc.cam.ac.uk/data_request/cif.
4. Conclusions
The relative orientation of the aryl groups attached to the
chalcogen atom is a distinguishing feature among the several

46
R.S. Chauhan et al. / Journal of Organometallic Chemistry 737 (2013) 40e46
[13] T.S. Lobana, P. Kaur, G. Hundal, R.J. Butcher, A. Castineiras, Z. Anorg. Allg.
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