Synthesis, structures and spectroscopic properties of platinum complexes containing orthometalated 2-phenylpyridine

Article abstract of DOI:10.1016/j.jorganchem.2010.01.035

The synthesis, structure and spectroscopy of a series of luminescent orthometalated square planar platinum(II) complexes are reported. Reaction of K₂PtCl₄ with one mole equivalent of 2-phenylpyridine (ppyH) in 2-ethoxyethanol and water (1:1 ratio) resulted in the formation of chloro-bridged dimeric precursor [Pt₂(μ-Cl)₂(ppy)₂], which on further reactions with various anionic one-, two- and three-atom ancillary ligands, having O/N/S donors, yielded mono- and bi-nuclear platinum(II) complexes. Platinum(III) complexes of composition [Pt₂Cl₂(μ-Epy)₂(ppy)₂] have been isolated with pyE^- (E = O or S) ligands. These complexes have been characterized by elemental analysis, NMR (¹H, ³¹P, ¹⁹⁵Pt) and absorption spectroscopy. The complexes [Pt₂(μ-N^∩N)₂(ppy)₂] (N^∩N = pyrazole and 3,5-dimethylpyrazole); [Pt(S^∩S)(ppy)] (S^∩S = ethylxanthate and diisopropyldithiophosphate); [Pt₂Cl₂(μ-Epy)₂(ppy)₂] (Epy = 2-pyridinol {Opy} and 2-mercaptopyridine {Spy}) and [PtCl(ppy)(PhNC(Me)NHPh)] have been structurally characterized by X-ray crystallography.

Full text of DOI:10.1016/j.jorganchem.2010.01.035

Journal of Organometallic Chemistry 695 (2010) 1237–1245
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Synthesis, structures and spectroscopic properties of platinum complexes
containing orthometalated 2-phenylpyridine
*
Ninad Ghavale, Amey Wadawale, Sandip Dey, Vimal K. Jain
Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400 085, India
a r t i c l e i n f o
a b s t r a c t
Article history:
The synthesis, structure and spectroscopy of a series of luminescent orthometalated square planar plat-
inum(II) complexes are reported. Reaction of K2PtCl4 with one mole equivalent of 2-phenylpyridine
(ppyH) in 2-ethoxyethanol and water (1:1 ratio) resulted in the formation of chloro-bridged dimeric pre-
Received 12 October 2009
Received in revised form 20 January 2010
Accepted 27 January 2010
Available online 6 February 2010
cursor [Pt2(
ancillary ligands, having O/N/S donors, yielded mono- and bi-nuclear platinum(II) complexes. Plati-
num(III) complexes of composition [Pt2Cl2(
-Epy)2(ppy)2] have been isolated with pyEꢀ (E = O or S)
ligands. These complexes have been characterized by elemental analysis, NMR (1H, 31P, 195Pt) and absorp-
tion spectroscopy. The complexes [Pt2(
-N\N)2(ppy)2] (N\N = pyrazole and 3,5-dimethylpyrazole);
[Pt(S\S)(ppy)] (S\S = ethylxanthate and diisopropyldithiophosphate); [Pt2Cl2(
-Epy)2(ppy)2] (Epy = 2-
l-Cl)2(ppy)2], which on further reactions with various anionic one-, two- and three-atom
l
Keywords:
Orthometalation
Platinum
2-Phenylpyridine
NMR
X-ray diffraction
l
l
pyridinol {Opy} and 2-mercaptopyridine {Spy}) and [PtCl(ppy)(PhNC(Me)NHPh)] have been structurally
characterized by X-ray crystallography.
Ó 2010 Elsevier B.V. All rights reserved.
1. Introduction
phenyl ring leads to blue and red shifts, respectively in the emis-
sion spectra [17]. Substitution of electron donating groups (Me or
Orthometalated platinum group metal complexes have been
extensively investigated [1,2] and have been used widely in many
fields, such as organic synthesis [3,4], metallomesogens [5–7],
photo-catalysts [8], opto-electronic devices [9–11] and building
blocks for self-assembled molecules [12]. Orthometalated plati-
num complexes in particular have attracted much attention re-
cently due to their interesting photophysical properties [13]
which can be exploited for chemosensors, light emitting diodes,
etc. applications. Although a number of platinum complexes are
luminescent [13–16], orthometalated complexes based on 2-aryl-
pyridines exhibit promising photophysical properties as many of
them are emissive in solution under ambient conditions [13].
Emission from metalated 2-arylpyridine platinum complexes in
solution has been assigned to ligand centered (LC) and/or metal-to-
ligand charge transfer (MLCT) states. Orthometalated ligands help
Me2N) at 4-position of the pyridyl ring results in to hypsochromic
shift in the emission spectra [17]. Ancillary ligands in orthometa-
lated 2-arylpyridine complexes of platinum(II) also play a crucial
role on photophysical properties. For instance, [Pt(ppy)Cl2]ꢀ
(Hppy = 2-phenylpyridine) is not luminescent in solution at room
temperature whereas [Pt(ppy)(Hppy)Cl] is luminescent under sim-
ilar conditions [19]. Much of the studies on role of photophysical
properties of orthometalated 2-arylpyridine type ligand complexes
of platinum(II) are concerned with b-diketonate derivatives
[17,18,20,21].
In the above perspective the present investigation was under-
taken to synthesize orthometalated 2-phenylpyridine platinum(II)
complexes with a variety of ancillary ligands (anionic one-, two-
and three-atom ligands having O/N/S donors) and identify the
nature of resulting complexes. The results of this investigation
are reported herein.
in raising the energy gap (
D
E) between lowest lying excited state
*
–p
*
) and/ or MLCT (d–p )] and high energy antibonding
[LC (p
dx2
orbital to an extent that they are not thermally accessible
ꢀy2
2. Experimental
(DE > kT). Thus the emission colors (i.e. DE) in orthometalated 2-
phenylpyridine complexes of platinum(II) can be tuned from
blue-green to orange-red by appropriately substituting either the
phenyl [17] and/or pyridyl [17,18] rings of 2-phenylpyridine. Sub-
stitution by an electron-withdrawing and -donating group in the
2.1. General procedures and instrumentation
Solvents were dried by standard methods with subsequent dis-
tillation under nitrogen. All reactions were carried out in Schlenk
flasks under a nitrogen atmosphere. Melting points were deter-
mined in capillary tubes and are uncorrected. IR spectra were re-
corded as Nujol mulls between CsI plates on a Bomem MB-102
* Corresponding author. Fax: +91 22 2550 5151.
E-mail address: jainvk@barc.gov.in (V.K. Jain).
0022-328X/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2010.01.035

1238
N. Ghavale et al. / Journal of Organometallic Chemistry 695 (2010) 1237–1245
FT-IR spectrometer. Elemental analyses were carried out on a Car-
lo-Erba EA-1110 CHN-O instrument. 1H, 13C{1H}, 31P{1H} and
195Pt{1H} NMR spectra were recorded on a Bruker DPX-300 and
Avance II-300 NMR spectrometers operating at 300, 75.47, 121.5
and 64.29 MHz, respectively. Chemical shifts are relative to inter-
nal chloroform peak (d 7.26 1H and 77.0 for 13C), external 85%
H3PO4 for 31P{1H} and Na2PtCl6 for 195Pt{1H}. Absorption spectra
were recorded on a Chemito Spectrascan UV 2600 spectrophotom-
eter. Emission spectra were recorded in dichloromethane on an
Edinburgh Instruments’ FLSP 920 system attached with 450 W Xe
lamp as excitation source and red sensitive PMT as detector.
The product was extracted with THF by passing through a Florisil
column. The filtrate was concentrated and acetone (1 mL) was
added which on cooling ꢂ5 °C yielded yellow crystals (75 mg,
63%). mp: above 290 °C. Anal. Calc. for C32H30N6Pt2: C, 43.2; H,
3.4; N, 9.5. Found: C, 43.1; H, 3.8; N, 9.7%. UV–Vis (CH2Cl2) kmax
in nm: 260 (119 000); 289 (sh); 331 (sh); 376 (24 000); 411 (sh).
1H NMR (CDCl3): d = 2.57, 2.63 (each s, Me); 5.90 (s, CH, dmpz);
6.55–6.82 (m); 7.06 (dd, 7.5, 1.8 Hz); 7.22 (d, 6 Hz); 7.43 (dd,
7 Hz); 7.81 (d, 6 Hz, 3J(Pt–H) = 20 Hz).
2.2.5. Synthesis of [PtCl(PhNCMeNHPh)(ppy)] (7)
To a dichloromethane suspension of [Pt2(l-Cl)2(ppy)2] (157 mg,
2.2. Synthesis of complexes
0.20 mmol), Ag(PhNCMeNPh) (125 mg, 0.39 mmol) was added and
stirred for 3 h. A change in color of the reaction mixture from yel-
low to dark brown was observed. The solvent was evaporated un-
der vacuum and the residue was extracted with dichloromethane,
and passed through a Florisil column. The filtrate was concentrated
and hexane (2 mL) was added, the solution on cooling gave yellow
crystals (127 mg, 52%). mp: 234 °C. Anal. Calc. for C25H22ClN3Pt: C,
50.4; H, 3.7; N, 7.0. Found: C, 50.0; H, 3.1; N, 6.8%. UV–Vis (CH2Cl2)
kmax in nm: 255 (31 400); 277 (sh); 325 (sh); 345 (sh); 400 (1700).
1H NMR (CDCl3): d = 2.09 (s, CMe); 7.10–7.80 (m, Ph, C6H4; H-3,4,5
(py)); 9.34 (s, NH); 9.66 (d, 6 Hz, 3J(Pt–H) = 36 Hz, H-4 (py)).
195Pt{1H} NMR (CDCl3) d: ꢀ3317 ppm.
2.2.1. Synthesis of [Pt2(l-Cl)2(ppy)2] (1)
To an aqueous solution (20 mL) of K2PtCl4 (996 mg, 2.40 mmol)
was added 2-phenylpyridine (372 mg, 2.41 mmol) in 20 mL 2-eth-
oxyethanol. A clear red solution was obtained, which was heated at
70 °C for 8 h whereupon a greenish solid separated out. The solid
was filtered through a G-3 assembly, washed with distilled water
(2 ꢁ 10 mL), acetone (2 ꢁ 5 mL) followed by dichloromethane
(2 mL) (608 mg, 66%). The acetone-dichloromethane washings on
drying gave greenish yellow complex, [Pt(ppy)(Hppy)Cl] (2),
(115 mg, 9%) as identified by 195Pt NMR. mp: >280 °C. Anal. Calc.
for C22H16Cl2N2Pt2: C, 34.3; H, 2.0; N, 3.6. Found: C, 34.2; H, 1.9;
N, 3.6%.
2.2.6. Synthesis of [Pt2Cl2(l-Opy)2(ppy)2] (8)
To a suspension of [Pt2(l-Cl)2(ppy)2] (389 mg, 0.50 mmol) in
2.2.2. Synthesis of [Pt2(
l
-SEt)2(ppy)2] (4)
dichloromethane, NaOMe (2.12 mL (0.46 N), 54 mg, 0.99 mmol)
was added and stirred for 15 min. To this mixture a methanolic
solution of HOpy (106 mg, 1.11 mmol) was added and the whole
was further stirred for 2 h. The reaction mixture was dried by evap-
orating the solvents in vacuo and extracted with dichloromethane
by filtering through a G-3 sintered disc. The filtrate was concen-
trated and few mL of benzene and acetone was added and the solu-
tion was kept at 0–5 °C for crystallization to yield orange crystals
(121 mg, 25%). mp: 243 °C (dec., darkens above 230 °C). Anal. Calc.
for C32H24Cl2N4O2Pt2: C, 40.1; H, 2.5; N, 5.9. Found: C, 39.5; H, 2.3;
N, 6.0%. UV–Vis (CH2Cl2) kmax in nm: 261 (35 100); 294 (44 500);
326 (sh); 384 (4400); 448 (1400). 1H NMR (CDCl3): d = 6.44–7.62
(m); 8.08 (d, 6 Hz); 9.05 (d, 6 Hz).
To dichloromethane (4 mL) suspension of
a
1 (103 mg,
0.13 mmol) was added 3 drops of pyridine to get a clear yellow
solution. To this an excess of ethylmercaptan (3 drops) was added
and stirred for 4 h. The solvent was evaporated under vacuum and
the residue was washed with methanol (3 ꢁ 3 mL) and dried in va-
cuo. The residue was dissolved in dichloromethane and passed
through a short Florisil column. Slow evaporation of the solvent
afforded yellow crystals (83 mg, 76%), mp: 233 °C. Anal. Calc. for
C26H26N2Pt2S2: C, 38.0; H, 3.2; N, 3.4; S, 7.8. Found: C, 37.9; H,
3.2; N, 3.3; S, 7.4%. UV–Vis (CH2Cl2) kmax in nm: 256 (49 800);
317 (8500); 328 (8800); 367 (8500). 1H NMR (CDCl3): d = 1.36,
1.65 (each t, 7.2 Hz, SCH2Me, cis isomer); 1.58 (t, 7.2 Hz, SCH2Me,
trans isomer); 2.93–3.11 (m, SCH2-, cis and trans isomers); 7.21–
7.89 (m, C6H4, CH-3,4,5 (py); cis and trans isomers); 8.90, 9.11(each
d, 5 Hz, H-6 py, cis isomer); 9.05 (d, 5 Hz, H-6 py, trans isomer).
2.2.7. Synthesis of [Pt2Cl2(l-Spy)2(ppy)2] (9)
To a dichloromethane (10 mL) suspension of [Pt2(
l
-Cl)2(ppy)2]
(143 mg, 0.18 mmol), [Pb(Spy)2] (90 mg, 0.21 mmol) was added
and stirred for 3 h. The color of the reaction mixture turned red.
This was filtered through a G-3 assembly. The filtrate was concen-
trated and acetone (1 mL) and hexane (1 mL) were added and the
clear solution on cooling at ꢂ5 °C gave red crystals which were
separated, washed with benzene/hexane (1:10) mixture and dried
(103 mg, 60%), mp: 253 °C. Anal. Calc. for C32H24Cl2N4Pt2S2.C6H6: C,
42.7; H, 2.8; N, 5.2; S, 6.0. Found: C, 41.5; H, 2.4; N, 6.0; S, 8.3%. UV–
Vis (CH2Cl2) kmax in nm: 259 (61 800); 283 (55 300); 352 (20 500);
502 (5300). 1H NMR (CDCl3): d = 6.48–7.62 (m); 8.17 (d, 6 Hz,
3J(Pt–H) = 30 Hz); 9.54 (d, 6 Hz, 3J(Pt–H) = 18 Hz, H-6(py)).
2.2.3. Synthesis of [Pt2(
l-pz)2(ppy)2] (5)
To a dichloromethane suspension of [Pt2(
l
-Cl)2(ppy)2] (396 mg,
0.51 mmol) was added NaOMe (2.16 mL (0.46 N), 55 mg,
1.0 mmol) and stirred for 15 min. Subsequently a methanolic solu-
tion of pyrazole (73 mg, 1.0 mmol) was added and the whole reac-
tion mixture was stirred for additional 3 h. The solvents were
evaporated under vacuum and the residue was extracted with
dichloromethane. The extract was concentrated and hexane
(2 mL) was added and on cooling ꢂ5 °C gave yellow crystals which
were decanted and washed with dichloromethane (217 mg, 51%).
mp: 247 °C (dec., darkens above 240 °C). Anal. Calc. for
C28H22N6Pt2: C, 40.4; H, 2.6; N, 10.1. Found: C, 40.7; H, 2.2; N,
9.8%. UV–Vis (CH2Cl2) kmax in nm: 256 (43 500); 284 (25 100);
328 (12 300); 356 (9900); 406 (2900). 1H NMR (CDCl3): d = 6.42
(t, 2 Hz, H-4 (pz)); 6.48 (m); 6.70–6.85 (m); 7.09 (d, 7 Hz); 7.45–
7.50 (m); 7.62 (br); 7.98–8.15 (m).
2.2.8. Synthesis of [Pt(S2COEt)(ppy)] (10)
To a methanolic solution of NaS2COEt (84 mg, 0.58 mmol),
[Pt2(l-Cl)2(ppy)2] (218 mg, 0.28 mmol) was added and stirred for
3 h. The solvents were removed in vacuo and the residue was
washed with hexane and extracted with dichloromethane by filter-
ing through a Florisil column. The filtrate was concentrated and
few mL of hexane was added, kept at 0–5 °C for crystallization to
yield dark yellow crystals (193 mg, 72%) mp: 145 °C. IR:
1713 cmꢀ1 (C@O). Anal. Calc. for C14H13NOPtS2: C, 35.7; H, 2.8;
N, 3.0; S, 13.6. Found: C, 35.8; H, 2.5; N, 3.2; S, 17.1%. UV–Vis
(CH2Cl2) kmax in nm: 250 (32 800); 287 (18 200); 329 (sh); 360
2.2.4. Synthesis of [Pt2(
To a THF solution of dmpzH (26 mg, 0.26 mmol) excess of NaH
was added and stirred for 1 h. To this reaction mixture [Pt2(
l-dmpz)2(ppy)2] (6)
l
-
Cl)2(ppy)2] (103 mg, 0.13 mmol) was added and was further stirred
for 1 h. The solvent was evaporated to obtain yellow-orange solid.

N. Ghavale et al. / Journal of Organometallic Chemistry 695 (2010) 1237–1245
1239
(sh); 377 (11 500); 435 (1900). 1H NMR (CDCl3): d = 1.57 (t, 7.5 Hz,
3. Results and discussion
3H, OCHCH3); 4.75 (q, 7.5 Hz, 2H, OCH2CH3); 7.14–8.00 (m);
8.62 (d, 5 Hz, 3J(Pt–H) = 37 Hz). 195Pt{1H} NMR (CDCl3) d:
ꢀ3881 ppm.
3.1. Synthesis and spectroscopy
The halo-bridged binuclear platinum complexes, [Pt2(l-
Cl)2(X)2L2] (X = anionic ligand such as alkyl, aryl, halide; L = neutral
donor) are versatile synthons for the preparation of a variety of
platinum complexes differing in nuclearity [1]. Accordingly reac-
2.2.9. Synthesis of [Pt{S2P(OPri)2}(ppy)] (11)
To methanolic solution of NH4S2P(OPri)2 (188 mg, 0.79 mmol),
tions of [Pt2(l-Cl)2(ppy)2] with a variety of anionic ligands were
[Pt2(l-Cl)2(ppy)2] (301 mg, 0.39 mmol) was added and stirred
conceived for the synthesis of 2-phenylpyridine platinum(II) com-
plexes. The reaction of K2PtCl4 with 2-2.5 equivalents of 2-phenyl-
pyridine in a mixture of 2-ethoxyethanol–water (3:1) at 80 °C over
a period of 16 h has been reported earlier, without characterizing
3 h. The solvents were evaporated to dryness and the residue
was extracted with dichloromethane. The extract was filtered
through a Florisil column and the filtrate was concentrated. Few
drops of acetone and hexane were added for crystallization and
the mixture was allowed to evaporate slowly. Yellow crystals were
obtained (176 mg, 40%) mp: 189 °C. Anal. Calc. for C17H22NO2PPtS2:
C, 36.3; H, 3.9; N, 2.5; S, 11.4. Found: C, 36.3; H, 3.9; N, 2.6; S,
14.1%. UV–Vis (CH2Cl2) kmax in nm: 250 (18 300); 287 (12 300);
313 (sh, 5380); 364 (4800); 410 (sh). 1H NMR (CDCl3): d = 1.42
(d, 6 Hz, 12H, OCHMe2); 4.95 (sept, 6 Hz, 2H, OCHMe2); 7.06–7.90
(m); 8.78 (d, 6 Hz, 3J(Pt–H) = 45 Hz). 31P{1H}NMR (CDCl3) d: 96.8
(2J(195Pt–31P) = 320 Hz). 195Pt{1H} NMR (CDCl3) d: ꢀ3797 (d,
2J(195Pt–31P) = 298 Hz) ppm.
data, to yield binuclear complex, [Pt2(l-Cl)2(ppy)2] (1) [17,27]
and the resulting product has been used directly in further reac-
tions for the preparation of b-diketonate complexes of the type
[Pt(ppy)(b-dik)] [17,20]. It has been shown subsequently that un-
der these conditions [Pt(ppy)(Hppy)Cl] (2) is formed [21,28], which
and related derivatives, [Pt(Arpy)(HArpy)Cl], have been used for
the preparation of b-diketonate complexes, [Pt(C\N)(b-dik)]
(C\N = ppy or Arpy) [21,27,29]. Ford et al. [30], however, obtained
1 by the reaction of [Bu4N]2[PtCl4] in ethanol with 1.1 equivalent of
Hppy in dichloromethane at room temperature for 5–7 days. Other
products, 2 and [Pt(ppy)Cl2]ꢀ are also formed when 4 equivalents
of Hppy was used and the reaction was carried out in MeOH at
50 °C for 12 h [30]. Interestingly the reaction of 2-phenylpyridine
2.3. Crystallography
with Na2PdCl4 is quite facile and yields [Pd2(l-Cl)2(ppy)2] [31]
which has a cis chloro-bridged dimeric structure as revealed by
X-ray structural analysis [32].
We have carried out the reaction of 2-phenylpyridine with
K2PtCl4 under the conditions described earlier [17] and also in
1:1 molar ratio in 2-ethoxyethanol (Scheme 1). In the former case
the complex 2, as reported by Marder et al. [21] and Slugovc et al.
[28], was formed while in the latter reaction an insoluble product
of composition (from microanalysis) ‘‘Pt(ppy)Cl” was isolated in
ꢂ65% yield. This complex was soluble in coordinating solvents like
Intensity data were collected on a Rigaku AFC7S diffractometer
fitted with Mo-Ka (k = 0.71069 Å) radiation so that hmax = 27.5°.
The structures were solved by direct methods [22], and refine-
ment [23] was on F2 using data corrected for absorption correc-
tion effects with an empirical procedure [24,25]. The non-
hydrogen atoms were refined with anisotropic displacement
parameters and fitted with hydrogen atoms in their calculated
positions. Molecular structures were drawn using ORTEP [26].
Crystal data and details of collection and refinement are given
in Table 1.
Table 1
Crystallographic and structure refinement data for platinum complexes.
Complex
5ꢃ(CH2Cl2)0.5
6ꢃ(CH2Cl2)0.5ꢃH2O
7
8
9ꢃ(C6H6)2
10
11
Chemical formula
Formula weight
Crystal size (mm3)
Crystal system
Space group
Unit cell dimensions
a (Å)
C28.5H23ClN6Pt2
875.16
C32.5H33OClN6Pt2
949.25
C25H22ClN3Pt
594.99
C32H24Cl2N4O2Pt2
957.63
C44H36Cl2N4S2Pt2
1145.98
C14H13NOPtS2
470.46
C17H22NO2PPtS2
562.59
0.15 ꢁ 0.10 ꢁ 0.10 0.15 ꢁ 0.15 ꢁ 0.10 0.40 ꢁ 0.20 ꢁ 0.10 0.15 ꢁ 0.10 ꢁ 0.05 0.40 ꢁ 0.30 ꢁ 0.20 0.50 ꢁ 0.20 ꢁ 0.50 0.40 ꢁ 0.20 ꢁ 0.20
monoclinic
P21/a
monoclinic
P21/a
monoclinic
P21/n
monoclinic
C2/c
triclinic
monoclinic
P21/n
orthorhombic
Pnma
ꢀ
P1
23.500(3)
11.651(6)
19.774(5)
90
102.390(15)
90
5288(3)
2.198
4
10.701/3272
ꢀ17 6 h 6 30
0 6 k 6 15
ꢀ25 6 l 6 25
2.55–27.51
34.423(10)
12.790(6)
15.160(5)
90
101.49(2)
90
6541(4)
1.924
4
8.662/3592
ꢀ25 6 h 6 44
0 6 k 6 16
ꢀ19 6 l 6 19
2.53–27.50
18.400(3)
7.897(2)
16.555(3)
90
114.820(12)
90.00(8)
2183.4(8)
1.807
15.630(3)
11.341(3)
16.968(3)
90
102.015(13)
90
2942.0(10)
2.162
4
9.719/1800
ꢀ11 6 h 6 20
0 6 k 6 14
ꢀ22 6 l 6 21
2.66–27.50
11.694(2)
13.430(3)
14.200(4)
101.130(18)
107.377(16)
110.891(15)
1873.0(7)
1.963
18.960(6)
5.755(3)
14.086(5)
90
109.61(3)
90
1447.8(10)
2.158
4
9.969/888
ꢀ13 6 h 6 24
0 6 k 6 7
ꢀ18 6 l 6 17
3.07–27.51
9.478(2)
14.5200(15)
14.685(4)
90
90
90
2020.9(7)
1.855
2
7.240/1092
ꢀ6 6 h 6 12
ꢀ10 6 k 6 18
0 6 l 6 19
2.56–27.50
b (Å)
c (Å)
a
(°)
b (°)
(°)
V (Å3)
c
q
Z
l
calcd. (g cmꢀ3
)
4
2
(mmꢀ1)/F(0 0 0)
6.565/1148
ꢀ13 6 h 6 23
0 6 k 6 10
ꢀ21 6 l 6 19
2.71–27.50
7.751/1058
ꢀ8 6 h 6 15
ꢀ17 6 k 6 16
ꢀ18 6 l 6 17
2.70–27.51
Limiting indices
Range of data
collection (°)
Reflections
collected/unique
Data/restraints/
parameters
12 109/3770
12 109/0/262
15 023/4495
15 023/0/198
5012/3088
5012/0/272
3387/2326
3387/0/190
8598/5855
8598/0/460
3333/2482
3333/0/173
2414/1234
2414/0/119
Final R1, wR2 indices 0.0848/0.2355
0.0734/0.1791
0.3100/0.1427
0.81
0.0639/0.2020
0.1230/0.1657
1.025
0.0353/0.0790
0.0777/0.0719
1.014
0.0484/0.1548
0.1413/0.0869
1.001
0.0257/0.0647
0.0647/0.0558
1.087
0.0492/0.1371
0.1402/0.1099
0.988
R1, wR2 (all data)
Goodness of
0.3156/0.1645
0.907
fit (GOF) on F2

1240
N. Ghavale et al. / Journal of Organometallic Chemistry 695 (2010) 1237–1245
K2PtCl4
2-3 Hppy
EtOCH2CH2OH + H2O
1 Hppy
EtOCH2CH2OH
80 °C
80 °C
[Pt2(μ-Cl)2(ppy)2]
(1)
[Pt(ppy)(Hppy)Cl]
(2)
excess Hppy
dmso
195Pt NMR, δ = -3201
[Pt(ppy)Cl(dmso)]
(3)
195Pt NMR, δ = -3807
Scheme 1.
dmso and gave a complex of composition [Pt(ppy)Cl(dmso)] (3)
which was structurally characterized (see Supplementary mate-
rial). The cleavage of chloro-bridged binuclear platinum complexes
with dmso to yield mononuclear complexes is well documented
[33]. The 195Pt NMR spectrum of 3 in dmso exhibited a single res-
onance at d ꢀ3807 ppm. When a dmso solution of 3 was treated
with an excess of 2-phenylpyridine in NMR tube, a new 195Pt res-
onance appeared at d ꢀ3201 ppm attributable to 2. Based on this,
the insoluble complex formed in 1:1 reaction can be considered
as binuclear complex [Pt2(l-Cl)2(ppy)2] (1). The reaction of K2PtCl4
with 2 or more equivalents of 2-phenylpyridine appears to yield
initially 1 which undergoes bridge cleavage reaction with the ex-
cess of 2-phenylpyridine to afford 2.
Various complexes synthesized using 1 are shown in Scheme 2.
The reaction of 1 with an excess of ethylmercaptan in the presence
of pyridine as HCl scavenger in dichloromethane afforded bis(thio-
lato)-bridged complex, [Pt2(l-SEt)2(ppy)2] (4). Interestingly at-
tempts to prepare bis(thiolato)-bridged palladium complexes
N
N
Cl
N
N
Cl
Pt
Pt
Cl
Pt
NH
N
N
N
O
O N
Cl
Pt
Pt
Cl
CH3
N
S
S N
(8)
(i) 2 NaOMe
(ii) 2 HOpy
(7)
(9)
Pb(Spy)2
2 [AgPhNC(CH3)NPh]
CH3
H3C
N
S
S
N
2 Na(S2COEt)
excess NaH
2 dmpzH
N N
N N
[Pt2(µ-Cl)2(ppy)2]
Pt
C
O
Et
Pt
Pt
N
(1)
H3C
CH3
(10)
2 NH4{S2P(OPri)2}
(i) 2 NaOMe
(ii) 2 pzH
(6)
(i) py
(ii) EtSH
OPri
OPri
S
N
Pt
P
N
N
N
N
S
Pt
Pt
[Pt2(µ-SEt)2(ppy)2]
N
N
(11)
(4a) and (4b)
(5)
Scheme 2.

N. Ghavale et al. / Journal of Organometallic Chemistry 695 (2010) 1237–1245
1241
containing C\N type ligands led to the isolation of mixed chloro/
mercapto bridged complexes, [Pd2( -Cl)(
-SR)(C\N)2] [34–37].
However, heavier organochalcogenolate ligands readily give
bis(organochalcogenolate) complexes, [Pd2(
-EAr)2(C\N)2] (E = Se
olate complexes (10 and 11) are blue shifted with respect to the
absorption band for [Pt(acac)(ppy)] [17,20]. The binuclear com-
plexes (5, 6, 8, 9) with shorter Pt–Pt separation exhibited an addi-
tional weak band of lower energy (406–502 nm) which may be
assigned to metal–metal-to-ligand charge transfer (MMLCT) tran-
sition. This band is red shifted with decreasing Pt–Pt separation.
Preliminary work on photoluminescence revealed that these com-
plexes, except [Pt2(l-SEt)2(ppy)2], are emissive in solution. A de-
tailed study on photoluminescence properties of these complexes
will be published separately.
l
l
l
or Te) [34]. The 1H NMR spectrum of 4 in CDCl3 exhibited two sets
of resonances attributable to cis and trans isomers. The trans iso-
mer displayed a triplet and a quartet for CH3 and CH2 protons of
magnetically equivalent two SEt groups. For the cis isomer two sets
of triplets and quartets were observed for two non-equivalent SEt
groups, one trans to metalated carbon and another trans to nitro-
gen donor atom of ppy. Platinum complexes derived from metalat-
ed phosphine ligand and bridging organochalcogenolate ligands
have been isolated as a mixture of cis and trans isomers [38,39].
The reaction of 1 with pyrazole and 3,5-dimethylpyrazole in the
3.2. Crystal structures
Molecular structures of these complexes have been established
unequivocally by single crystal X-ray diffraction analyses. ORTEP
drawings are shown in Figs. 1-7 and selected interatomic parame-
ters for 8 and 9 are given in Tables 2 and 3. The metalated 2-phen-
ylpyridine ligands, in general, have a planar arrangement around
distorted square planar platinum atom. The Pt–C and Pt–N dis-
tances involving metalated 2-phenylpyridine lie in the ranges
1.958–2.074 and 1.963–2.148 Å, respectively, while the N–Pt–C
angles vary between 78.6 and 82.3°. The acute N–Pt–C angle is
characteristic of orthometalated five membered C\N ligands in
transition metal complexes. The Pt–C and Pt–N distances and N–
Pt–C angle in the complexes reported here are well within the
range reported in orthometalated 2-phenylpyridine complexes of
platinum such as [PtCl(ppy)(Hppy)] [30], [Pt(ppy)(PhCOCHCOPh)]
[20] and [Pt(ppy){(Me2pz)2BH2}] [17].
presence of a base gave pyrazolato-bridged derivatives, [Pt2(l-
N\N)2(ppy)2] (N\N = pz (5); dmpz (6)]. Treatment of 1 with silver
salt of 1,3-diphenylacetamidine gave a mononuclear complex,
[PtCl(PhNCMeNHPh)(ppy)] (7) rather than the acetamidinato–
bridged complex. The 7 appeared to be formed by the reaction of
moisture on acetamidine complex. The reactions of small bite
three-atom anionic ligand, pyOH and pySH, with 1 gave after pro-
cessing binuclear platinum(III) complexes, [Pt2Cl2(l-Opy)2(ppy)2]
(8) and [Pt2Cl2( -Spy)2(ppy)2] (9), as isolable products. These li-
l
gands have been known to give binuclear platinum complexes
with short metal-metal contacts which undergo facile oxidation
leading to the formation of platinum(III) complexes [40]. For exam-
ple, the complex, [Pt(Spy)2]2 is readily oxidized in halogenated sol-
vents (e.g. CHCl3) to give [Pt2X2(Spy)4] [41]. The complexes 8 and 9
represent rare examples of orthometalated platinum complexes in
higher oxidation state (>2) of platinum. Recently orthometalated
palladium(III) and platinum(IV) complexes have been described
Table 2
Selected bond lengths (Å) and angles (°) for [Pt2Cl2(l-Opy)2(ppy)2] (8).
[42–44]. The palladium(III) complex [Pd2X2(l-OAc)2(benz)2]
(benz = metalated benzoquinoline) undergo bimetallic reductive
elimination of halogenated benzoquinoline [44]. The reaction of 1
with large bite three-atom anionic ligands, such as ethylxanthate
and diisopropyldithiophosphate yielded mononuclear complexes,
[Pt(S\S)(ppy)] (S\S = S2COEt (10); S2P{OPri}2 (11)) in which the
dithiolate ligand is chelated.
The mononuclear complexes 2, 3 and 7 adopt a configuration in
which nitrogen atom of the chelating ppy ligand is trans to the do-
nor atom of the incoming ligand. A configuration with the N atom
of the ppy cis to neutral donor would be unfavorable as it would be
expected to isomerize via a dissociative mechanism [45].
Pt(1)–Cl(1)
Pt(1)–N(1)
Pt(1)–O(1)
Pt(1)–N(2)
2.454(2)
2.050(6)
2.134(5)
2.016(6)
173.63(4)
88.6(2)
84.61(18)
91.03(15)
96.71(17)
88.9(2)
Pt(1)–C(12)
1.988(7)
2.5681(7)
1.280(8)
1.375(9)
94.0(3)
82.70(14)
95.4(2)
177.1(3)
94.89(17)
81.6(3)
Pt(1)–Pt(1)i
C(1)–O(1)
C(1)–N(1)
Cl(1)–Pt(1)–Pt(1)i
Cl(1)–Pt(1)–Cl(2)
Cl(1)–Pt(1)–N(2)
Cl(1)–Pt(1)–O(1)
Cl(1)–Pt(1)–N(1)
N(1)–Pt(1)–O(1)
N(1)–Pt(1)–Pt(1)i
N(1)–Pt(1)–N(2)
N(1)–Pt(1)–C(12)
O(1)–Pt(1)–Pt(1)i
O(1)–Pt(1)–N(2)
O(1)–Pt(1)–Cl(12)
N(2)–Pt(1)–Pt(1)i
N(2)–Pt(1)–C(12)
C(12)–Pt(1)–Pt(1)i
84.29(17)
175.4(2)
97.6(2)
The 1H NMR spectra of these complexes displayed expected res-
onances. The CH-6 proton of pyridine ring of the chelating ppy li-
gand appeared as a doublet in the range 7.81–9.66 ppm with
3J(195Pt–1H) of 18–37 Hz. The 195Pt NMR of 2, 3, 7, 10, 11 displayed
single resonances in the region d ꢀ3201 to ꢀ3881 ppm. The 195Pt
signal for 11 appeared as a doublet due to coupling with a phos-
phorus nucleus (2J(195Pt–31P) = 298 Hz) of the dithiophosphate li-
gand. The 31P NMR spectrum of 11 displayed a singlet at d
96.8 ppm with 2J(195Pt–31P) of 320 Hz, indicative of chelating
dithiophosphate ligand [46,47]. The magnitude of 2J(195Pt–31P) is
in accord with dithiophosphate complexes of platinum(II) [46].
These complexes vary in color from pale -yellow, -orange to -
red. Absorption spectra of these complexes in dichloromethane
Table 3
Selected bond lengths (Å) and angles (°) for [Pt2Cl2(
(9ꢃ(C6H6)2).
l
-Spy)2(ppy)2]ꢃ(C6H6)2
Pt(1)–Cl(1)
Pt(1)–S(1)
Pt(1)–N(2)
Pt(1)–N(3)
Pt(1)–C(17)
Pt(1)–Pt(2)
2.487(3)
2.305(3)
2.168(7)
2.024(9)
2.069(7)
2.6253(7)
176.34(7)
92.0(2)
89.87(11)
85.8(3)
88.3(2)
86.5(2)
86.4(2)
177.1(3)
96.8(3)
86.71(8)
95.6(3)
176.3(2)
95.8(3)
81.1(3)
Pt(2)–Cl(2)
Pt(2)–S(2)
Pt(2)–N(1)
Pt(2)–N(4)
Pt(2)–C(28)
2.475(4)
2.312(3)
2.173(7)
2.015(9)
2.067(8)
Cl(1)–Pt(1)–Pt(2)
Cl(1)–Pt(1)–N(2)
Cl(1)–Pt(1)–S(1)
Cl(1)–Pt(1)–N(3)
Cl(1)–Pt(1)–C(17)
N(2)–Pt(1)–Pt(2)
N(2)–Pt(1)–S(1)
N(2)–Pt(1)–N(3)
N(2)–Pt(1)–C(17)
S(1)–Pt(1)–Pt(2)
S(1)–Pt(1)–N(3)
S(1)–Pt(1)–C(17)
N(3)–Pt(1)–Pt(2)
N(3)–Pt(1)–C(17)
C(17)–Pt(1)–Pt(2)
Cl(2)–Pt(2)–Pt(1)
Cl(2)–Pt(2)–N(1)
Cl(2)–Pt(2)–S(2)
Cl(2)–Pt(2)–N(4)
Cl(2)–Pt(2)–C(28)
N(1)–Pt(2)–Pt(1)
N(1)–Pt(2)–S(2)
N(1)–Pt(2)–N(4)
N(1)–Pt(2)–C(28)
S(2)–Pt(2)–Pt(1)
S(2)–Pt(2)–N(4)
S(2)–Pt(2)–C(28)
N(4)–Pt(2)–Pt(1)
N(4)–Pt(2)–C(28)
C(28)–Pt(2)–Pt(1)
176.08(8)
88.9(2)
93.80(11)
89.2(3)
84.8(2)
87.2(2)
86.3(2)
177.4(3)
97.6(3)
86.63(7)
95.6(3)
175.8(2)
94.6(2)
80.4(4)
95.1(2)
*
showed bands assignable to p–p and MLCT transitions from meta-
lated ppy ligand in the region 255–400 nm. The lower energy
weaker absorption bands may be assigned to metal-to-ligand
charge transfer transition. The absorption band in 2 at 400 nm
(lit. 402 nm [19] due to MLCT) is blue shifted in dmso complex 3
(372 nm). It is worth noting that when nitrogen ligands whether
in the terminal position (as in 7) or in bridging mode (e.g. 5 and
6) are substituted with sulfur donors in either situation (e.g. 3 in
dmso complex and 4 in thiolato bridge) the MLCT band is blue
shifted and appears at ꢂ370 nm. Similarly the absorptions in dithi-
95.2(2)

1242
N. Ghavale et al. / Journal of Organometallic Chemistry 695 (2010) 1237–1245
The structural features of [PtCl(ppy)(Hppy)] [30] and
The pyrazolato–bridged complexes, [Pt2(l-pz)2(ppy)2] and
[PtCl(dmso)(ppy)] [48] (see Supplementary material) are in accor-
dance with the structural parameters reported earlier.
The molecular structure of [PtCl(ppy)(PhNCMeNHPh)] is
shown in Fig. 3. The amidine ligand is coordinated to platinum
through C@N and is trans to the nitrogen atom of the metalated
2-ppy ligand. The two Pt–N distances are comparable and are in
accordance with Pt–N bond length reported in other platinum
complexes, such as [PtCl2(bipy)] [29]. The N–C–N angle in ami-
dine (115.0(12)°) is reduced markedly from the ideal value of
120°.
[Pt2( -dmpz)2(ppy)2], (Figs. 1 and 2, respectively) comprise of
l
two ‘‘Pt(ppy)” fragments which are held together by exo-bidentate
pyrazolate ligands. The six-membered ‘‘Pt2N4” ring has a boat con-
formation with the platinum atoms at the vertexes of the boat.
Similar boat conformation has been reported in [Pt2Cl2(
l
-
-
dmpz)2(PMePh2)2] [49], [Pt2(
l
-dmpz)2(P\C)2] [50] and [Pt2(
l
pz)2(thpy)2] [29]. The two pyrazolato-ligands are planar within
experimental error and the average dihedral angles between the two
planes are 100.4° and 98.98°, respectively. The molecules adopt
a sym-trans configuration. Both sym-trans (e.g. [Pt2(l-pz)2(thpy)2]
Fig. 1. ORTEP drawing with crystallographic numbering scheme for [Pt2(
lengths (Å) and angles (°): Pt(1)–N(1) 2.11(2), Pt(1)–N(3) 2.09(2), Pt(3)–N(7) 2.04(2), Pt(3)–N(9) 2.04(2), Pt(2)–N(2) 2.02(2), Pt(4)–N(10) 2.08(2), Pt(2)–N(4) 2.01(2), Pt(4)–
l-pz)2(ppy)2]ꢃ(CH2Cl2)0.5 (5ꢃ(CH2Cl2)0.5) (ellipsoids drawn with 50% probability). Selected bond
N(8) 2.00(3), Pt(1)–Pt(2) 3.289, Pt(3)–Pt(4) 3.289, N(1)–Pt(1)–N(3) 86.3(8), N(9)–Pt(3)–N(7) 87.1(9), N(2)–Pt(2)–N(4) 87.1(8), N(10)–Pt(4)-N(8) 84.8(9).
Fig. 2. ORTEP drawing with crystallographic numbering scheme for [Pt2(
l
-dmpz)2(ppy)2]ꢃ(CH2Cl2)0.5ꢃH2O (6.(CH2Cl2)0.5ꢃH2O), (ellipsoids drawn with 50% probability).
Selected bond lengths (Å) and angles (°): Pt(3)–N(10) 2.076(15), Pt(1)–N(3) 2.050(14), Pt(3)–N(11) 2.063(13), Pt(1)–N(5) 2.005(16), Pt(4)–N(12) 2.095(14), Pt(2)–N(4)
2.078(14), Pt(2)–N(6) 2.070(15), Pt(4)–N(9) 1.997(13), Pt(2)–Pt(1) 3.1904(13), Pt(4)–Pt(3) 3.2029(13), N(10)–Pt(3)–N(11) 84.9(6), N(3)–Pt(1)–N(5) 85.5(6), N(4)–Pt(2)–N(6)
85.3(6), N(12)–Pt(4)–N(9) 88.0(6).

N. Ghavale et al. / Journal of Organometallic Chemistry 695 (2010) 1237–1245
1243
Fig. 3. ORTEP drawing with crystallographic numbering scheme for
[Pt(ppy)(PhNHCMeNPh)Cl] (7) (ellipsoids drawn with 50% probability). Selected
bond lengths (Å) and angles (°): Pt(1)–Cl(1) 2.405(3), Pt(1)–C(7) 1.958(13), Pt(1)–
N(1) 2.038(10), N(2)–C(18) 1.326(19), Pt(1)–N(2) 2.036(11), N(3)–C(18) 1.348(18),
Cl(1)–Pt(1)–N(1) 95.7(3), N(1)–Pt(1)–N(2) 176.3(5), Cl(1)–Pt(1)–N(2) 87.5(4),
Pt(1)–N(2)–C(18) 125.5(9), N(2)–C(18)–N(3) 115.0(12).
[29], [Pt2(
l
-3-Me,5-Butpz)2{(2,4-F2C6H2)py}2] [51] and sym-cis
-N\N)2{(2,4-F2C6H2)py}2] (N\N = pz, dmpz, But2pz))
(e.g. [Pt2(
l
Fig. 4. ORTEP drawing with crystallographic numbering scheme for
[Pt2Cl2(l-Opy)2(ppy)2] (8) (ellipsoids drawn with 50% probability).
[51] have been reported for metalated arylpyridine platinum com-
plexes containing pyrazolate-bridges. The two-bridging pyrazolate
ligands form disparate Pt–N bonds reflecting the different trans
influence of the C-(phenyl) and N (pyridyl) donor atoms of ppy.
The shorter Pt–N distances have the N atoms trans to N of ppy
while longer Pt–N bond lengths have the N(pz) trans C (phenyl)
atom. The Ptꢃ ꢃ ꢃPt spacings are 3.289 (for pz) and av. 3.196 (for
dmpz) Å. The Ptꢃ ꢃ ꢃPt separations in various pyrazolato-bridged
substituting bulky groups at 3- and 5-positions of the bridging pyr-
azolate ligand [51]. There are weak interactions between the
p–p
ppy groups of two molecules. The two boat-shaped molecules are
entangled in each other.
The complexes [Pt2Cl2(l-Opy)2(ppy)2] and [Pt2Cl2(l-Spy)2(p-
complexes are 3.170(1) Å [Pt2Cl2(
l-dmpz)2(PMePh2)2] [49];
py)2] (Figs. 4 and 5, respectively) have similar geometries contain-
ing two platinum atoms bridged by two pyE (E = O or S) ligands in a
head-to-tail fashion and overall configuration can be compared
3.432(1) Å [Pt2(l-pz)2(thpy)2] [29]; 2.8343–3.3763Å [Pt2(l-
N\N)2{(2,4-F2C6H2)py}2] [51]. The Ptꢃ ꢃ ꢃPt separation decreases by
Fig. 5. ORTEP drawing with crystallographic numbering scheme for [Pt2Cl2(l-Spy)2(ppy)2]ꢃ(C6H6)2 (9ꢃ(C6H6)2) (ellipsoids drawn with 50% probability).

1244
N. Ghavale et al. / Journal of Organometallic Chemistry 695 (2010) 1237–1245
with [Pt2Cl2(Opy)2(en)2]2+ (en = H2NCH2CH2NH2) [52,53]. Each
platinum atom adopts an octahedral configuration defined by che-
lating ppy ligand, E and N atoms of pyE ligands, a chloride and a Pt–
Pt bond. The oxygen/sulfur atom of Epy ligand is trans to the C-
atom of the metalated ppy. The platinum atom coordination planes
are deviated with the twist angles (defined by the torsion angle E–
Pt–Pt–N) of 26.57° and 33.21° from the ideal eclipsed configura-
tion. The ppy rings are inclined to each other at an angle of
14.81° and 13.89° in 8 and 9, respectively. The Pt–Cl distances
(av. 2.454 Å in Opy and av. 2.481 Å in Spy) can be compared with
those found in Pt(III) complexes (e.g. [Pt2Cl2(4-MepyS)4], Pt–Cl =
av. 2.451 Å) [54]. The Pt–Pt distances 2.5681(7) Å (in Opy) can be
compared to the reported value [Pt2XY(Opy)2(NH3)4]2+ (av.
2.575 Å) [55], whereas 2.6253(7) Å (in pyS) is slightly longer than
reported for [Pt2Cl2(Spy)4] (2.532(1) Å) [40]. The Pt–Pt distance in
platinum(III) complexes varies between 2.39 and 2.78 Å, being
shorter with smaller bite ligands [41].
The crystal structure of [Pt(S2COEt)(ppy)] (Fig. 6) consists of dis-
crete monomeric molecules. The geometry around platinum is dis-
torted square planar and is defined by the N and C atoms of the
metalated 2-phenylpyridine and two sulfur atoms of slightly asym-
metrically chelated xanthate ligand. The latter adopts its character-
istic geometry of chelated xanthate ligand in metal complexes [56].
The strain imposed by the four-membered PtS2C ring is reflected in
the S–Pt–S angle which is compressed to 74.28(6)° while the adja-
cent angles C7–Pt1–S2 and N1–Pt1–S1 are opened to 101.79(19)°
and 102.82(15)°, respectively. The Pt–S distance trans to C-(phe-
nyl) is longer than the one trans to nitrogen (pyridyl) owing to their
different trans influences. The Pt–S distances are well within the
range reported for the dithiolato complexes, e.g. [PtMe{S2P(O-
Pri)2}(AsPh3)] (Pt–S = 2.341(2), 2.434(2) Å) [46], [PtBui{S2CN-
Me2}(Pc-Hx3)] (Pt–S = 2.404(2), 2.412(3)) [57]. The two C–S
distances are similar (1.684(6) and 1.698(6) Å) and are intermedi-
ate between double (1.62 Å) and single bond (1.81 Å) values indi-
cating delocalization of double bond over OCSꢀ2 moiety.
Fig. 7. ORTEP drawing with crystallographic numbering scheme for [Pt(S2P{O-
Pri}2)(ppy)] (11) (N1i has been changed to C10 in the figure) (ellipsoids drawn with
50% probability). Selected bond lengths (Å) and angles (°): Pt(1)–S(1) 2.371(3), P(1)–
S(1) 2.003(4), Pt(1)–S(1)i 2.371(3), P(1)–S(1)i 2.003(4), Pt(1)–N(1) 2.020(9), P(1)–
O(1) 1.569(10), Pt(1)–C(10) 2.020(9), P(1)–O(2) 1.570(9), S(1)–Pt(1)–S(1)i
82.80(17), S(1)–P(1)–S(1)i 103.0(2), N(1)–Pt(1)–C(10) 82.1(5).
chelated as the two Pt–S distances (2.371(3) Å) are same and are
in accord with the literature values (e.g. [Pt{S2P(OEt)Ph}2] (Pt–
S = 2.333(3) and 2.341(3) Å) [58] and [Pt{S2P(OEt)2}2(PPh3)] (Pt–
S = 2.325(10)–2.388(12) Å) [47]. The Pt–S distances (2.003(4) Å)
are similar and are intermediate between single (2.09 Å) and dou-
ble bond (1.94 Å) values indicating symmetrically delocalized P–S
p
bond. The acute S–Pt–S angle (82.8°) is within the range (ꢂ83°)
of chelating dithiophosphate ligand ([Pt{S2P(OEt)2}2(PPh3)] (S–Pt–
S = 82.7(3)°) [47] and (S–Pt–
[PtMe{S2P(OPri)2}(AsPh3)]
S = 83.10(7)° [54].
The crystal structure of [Pt{S2P(OPri)2}(ppy)] (Fig. 7) shows that
the square planar platinum is coordinated by C and N atoms of ppy
ligand and the two S atoms of symmetrically chelated dithiophos-
phate ligand. The molecule has a mirror plane bisecting Pt and P
atoms, thus C and N atoms of ppy are indistinguishable. Unlike
the xanthate complex, the dithiophosphate is symmetrically
Acknowledgements
We thank Drs. T. Mukherjee and D. Das for encouragement of
this work. We are thankful to the Chemistry Department, IIT Bom-
bay, Mumbai for providing microanalysis of the complexes. The
authors also thank Dr. V. Sudarshan for recording photoluminis-
cence spectra. One of the authors (NG) is thankful to DAE for the
award of a Senior Research Fellowship.
Appendix A. Supplementary material
CCDC 737106, 737107, 737108, 737109, 737110, 737111,
737112, 737113 and 737114 contain the supplementary crystallo-
graphic data for complexes 5, 6, 7, 8, 9, 10, 11, 2 and 3, respectively
These data can be obtained free of charge from The Cambridge
Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_re-
quest/cif. Supplementary data associated with this article can be
found,
in
the
online
version,
at
doi:10.1016/
j.jorganchem.2010.01.035.
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Fig. 6. ORTEP drawing with crystallographic numbering scheme for [Pt(S2COEt)(-
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angles (°): Pt(1)–S(1) 2.4018(19), S(1)–C(12) 1.684(6), Pt(1)–S(2) 2.3106(18),
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119.7(4), S(2)–C(12)–O(1) 125.7(5), S(1)–Pt(1)–N(1) 102.82(15), C(7)–Pt(1)–N(1)
81.1(2).

N. Ghavale et al. / Journal of Organometallic Chemistry 695 (2010) 1237–1245
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