Disubstituted diphenyldithiophosphates of cadmium: Synthesis, characterization, and single-crystal X-ray structure

Article abstract of DOI:10.1080/00958972.2014.958473

A series of new disubstituted diphenyldithiophosphate complexes of cadmium [{(ArO)₂PS₂}₂Cd] (9-12) have been isolated in aqueous media while their donor stabilized adducts [{(ArO)₂PS₂}₂Cd·2C5H5N] (13-16) [(Ar = 2,4-(CH₃)₂C6H₃, 2,5-(CH₃)₂C6H₃, 3,4-(CH₃)₂C6H₃ and 3,5-(CH₃)₂C6H₃)] have been isolated in chloroform. These newly synthesized complexes were characterized by elemental analyses, IR and NMR (¹H, ¹³C and ³¹P) spectroscopic analyses. The dithiophosphate ligands are coordinated bidentate to the cadmium ion via the two thiolate sulfurs. The compounds [{(3,5-CH₃)₂C6H₃O}₂PS₂HNEt₃] (4) and [{(3,5-CH₃)₂C6H₃O}₂PS₂]₂Cd(NC5H5)₂ (16) crystallize in the monoclinic system with space group P2₁/c. Single-crystal X-ray analysis of 4 reveals that phosphorus of the anion is tetrahedrally bonded to two S and two O atoms. The structure is stabilized by cation-anion N-HS intermolecular hydrogen bond interactions. In 16, two diphenyldithiophosphate ions are bidentate with both sulfurs coordinated to cadmium. Each forms a four-membered chelate ring in the equatorial plane. Two pyridines are axially coordinated to cadmium leading to octahedral geometry. The thermal properties of this complex have also been examined by combined DTA/DTG thermal analyses.

Full text of DOI:10.1080/00958972.2014.958473

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Disubstituted diphenyldithiophosphates
of cadmium: synthesis,
characterization, and single-crystal X-
ray structure
Ruchi Khajuriaa, Sandeep Kumara, Atiya Syeda, Gurvinder Kourb,
Sumati Anthalb, Vivek K. Guptab, Rajni Kantb & Sushil Kumar
Pandeya
a Department of Chemistry, University of Jammu, Jammu, India
b X-ray Crystallography Laboratory, Post-Graduate Department of
Physics & Electronics, University of Jammu, Jammu, India
Accepted author version posted online: 26 Aug 2014.Published
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online: 16 Sep 2014.
To cite this article: Ruchi Khajuria, Sandeep Kumar, Atiya Syed, Gurvinder Kour, Sumati Anthal,
Vivek K. Gupta, Rajni Kant & Sushil Kumar Pandey (2014) Disubstituted diphenyldithiophosphates of
cadmium: synthesis, characterization, and single-crystal X-ray structure, Journal of Coordination
Chemistry, 67:17, 2925-2941, DOI: 10.1080/00958972.2014.958473
To link to this article: http://dx.doi.org/10.1080/00958972.2014.958473
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Journal of Coordination Chemistry, 2014
Vol. 67, No. 17, 2925–2941, http://dx.doi.org/10.1080/00958972.2014.958473
Disubstituted diphenyldithiophosphates of cadmium:
synthesis, characterization, and single-crystal X-ray structure
RUCHI KHAJURIA†, SANDEEP KUMAR†, ATIYA SYED†, GURVINDER KOUR‡,
SUMATI ANTHAL‡, VIVEK K. GUPTA‡, RAJNI KANT‡ and
SUSHIL KUMAR PANDEY*†
†Department of Chemistry, University of Jammu, Jammu, India
‡X-ray Crystallography Laboratory, Post-Graduate Department of Physics & Electronics,
University of Jammu, Jammu, India
(Received 6 December 2013; accepted 14 July 2014)
A series of new disubstituted diphenyldithiophosphate complexes of cadmium [{(ArO)2PS2}2Cd]
(9–12) have been isolated in aqueous media while their donor stabilized adducts
[{(ArO)2PS2}2Cd·2C5H5N] (13–16) [(Ar = 2,4-(CH3)2C6H3, 2,5-(CH3)2C6H3, 3,4-(CH3)2C6H3 and
3,5-(CH3)2C6H3)] have been isolated in chloroform. These newly synthesized complexes were char-
acterized by elemental analyses, IR and NMR (1H, 13C and 31P) spectroscopic analyses. The dithio-
phosphate ligands are coordinated bidentate to the cadmium ion via the two thiolate sulfurs. The
compounds [{(3,5-CH3)2C6H3O}2PS2HNEt3] (4) and [{(3,5-CH3)2C6H3O}2PS2]2Cd(NC5H5)2 (16)
crystallize in the monoclinic system with space group P21/c. Single-crystal X-ray analysis of 4
reveals that phosphorus of the anion is tetrahedrally bonded to two S and two O atoms. The struc-
ture is stabilized by cation–anion N–H⋯S intermolecular hydrogen bond interactions. In 16, two
diphenyldithiophosphate ions are bidentate with both sulfurs coordinated to cadmium. Each forms a
*Corresponding author. Email: kpsushil@rediffmail.com
© 2014 Taylor & Francis

2926
R. Khajuria et al.
four-membered chelate ring in the equatorial plane. Two pyridines are axially coordinated to
cadmium leading to octahedral geometry. The thermal properties of this complex have also been
examined by combined DTA/DTG thermal analyses.
Keywords: Cadmium(II); Diphenyldithiophosphate; Crystal structure; Pyridine
1. Introduction
The chemistry of cadmium dithiolates continues to be a prominent area of research for
emerging applications as precursors in metal organic chemical vapor deposition [1–3].
Recent work has established that cadmium dithiocarbamates may be useful precursors to
form CdS nanowires and may have applications as nonlinear optical materials [4, 5]. Cad-
mium and its compounds have numerous applications; however, in recent years, the use of
cadmium has declined, mainly due to concerns over the toxicity of cadmium and the intro-
duction of regulations. Cadmium and its compounds are a substantial industrial and envi-
ronmental pollutant [6] which seriously impairs erythropoiesis. Cadmium accumulates in
humans throughout their lives [7], with a negative effect on human beings and also to soil
micro-organisms [8–11]. The development of the efficient antidotes for cadmium intoxica-
tion has proven to be a task of considerable difficulty. Two types of chelating agents can
affect antidotes for cadmium intoxication: uncharged vicinal dithiols [12] and dithiocarba-
mates [13, 14]. The affinity of 1,1-dithiolate ligands for cadmium was indicated by the fact
that the ligands can be employed as scavengers for this toxic element in biological media.
Divalent d10 metal ions have various coordination geometries. While cadmium chemistry
of dithioacid based ligands like dithiocarbamate has been the subject of continuous study,
the corresponding cadmium dithiophosphate chemistry has not been developed. The versa-
tile bonding, structural features, and fascinating chemical as well as electrochemical reactivi-
ties of cadmium dialkyldithiophosphate complexes prompted us to make a systematic study
of cadmium diphenyldithiophosphates. During the past four decades, molecular structures of
cadmium(II) complexes are known for O,O′-dialkyldithiophosphate ligands [15–21]. In these
complexes, O,O′-dialkyldithiophosphate ligands adopt a bridging coordination to form
binuclear structures [Cd2{S2P(OR)2}4] (R = s-Bu [16], Cy [17], i-Pr [18, 19]) and polynu-
clear structures [Cd{S2P(OR)2}2]n (R = i-Bu) [20], (n-Pr and n-Bu) [21], eight-membered
metallocycles [Cd2S4P2] are formed in both bi- and polynuclear complexes.
These eight-membered metallocycles are easily destroyed by nitrogen donors in solution
and result in adducts with distorted octahedral geometry around cadmium, such as [Cd{S2P
(OR)2}2·Ln] (R = i-Pr, L = phen, n = 1 [22]; R = Et, L = hexamethylenetetramine, n = 2
[23]; R = i-Pr, L = py, n = 2 [24]). Herein, we report the synthesis, spectroscopic and struc-
tural properties of disubstituted diphenyldithiophosphate ligands with cadmium(II) and
donor stabilized complexes.
2. Experimental
2.1. Materials and instrumentation
Solvents were distilled and dried over sodium before use. Chloroform (Thomas Baker)
was dried over P2O5. All dimethylphenols (Sigma Aldrich) were used as supplied.

Diphenyldithiophosphates of cadmium
2927
Cd(NO3)2·4H2O (Sigma Aldrich) was used as received. Triethylammonium salts of
O,O′-disubstituted diphenyldithiophosphates were synthesized according to a literature pro-
cedure used for the synthesis of ditolyl dithiophosphates [25]. Moisture was carefully
excluded during the experimental manipulations for the synthesis of ligands by using stan-
dard Schlenk techniques. Cadmium and chloride were estimated gravimetrically as [Cd
(C5H5N)2](SCN)2] and estimated volumetrically by Volhard’s method, respectively [26].
Elemental analyses (C, H, N, S) were conducted using the Elemental Analyser Vario EL-III
(Indian Institute of Integrative Medicine, Jammu). Infrared spectra were recorded from
4000 to 200 cm−1 on a Perkin–Elmer spectrum RX1 FT-IR spectrophotometer (Sophisti-
1
cated Analytical Instrumentation Facility, Panjab University, Chandigarh). H, 13C and 31P
(proton-decoupled) NMR spectra were recorded in CDCl3 and DMSO-d6 using TMS as
internal reference and H3PO4 (85%) as external reference on a Bruker Avance III 400 MHz.
All chemical shifts are reported in δ units downfield from TMS. TGA/DTA was recorded
on a Linseis STA PT-1000 thermal analyser at a heating rate of 10 °C/min in air. NMR
spectral and thermal analyses were carried out at the Department of Chemistry, University
of Jammu, Jammu.
2.2. Synthesis of ligands
2.2.1. [{(2,4-CH3)2C6H3O}2PS2HNEt3] (1). A toluene solution (~40 mL) of 2,4-dimethyl-
phenol (4.39 g, 35.93 mM) was added dropwise to a toluene (~30 mL) suspension of P2S5
(2.00 g, 8.99 mM) with constant stirring. After stirring the contents for 5–7 min at ~40 °C,
a toluene solution (~40 mL) of Et3N (1.82 g, 17.98 mM) was added dropwise to it with
constant stirring. All the P2S5 was dissolved in 15–20 min, resulting in a clear colorless
solution and evolution of H2S was observed. Evaporation of excess toluene under reduced
pressure resulted in formation of 1 as a white crystalline solid in quantitative yield. The
resulting solid was dissolved in toluene and a few drops of n-hexane were added for recrys-
tallization at room temperature. Yield: 96% (7.52 g); m.p. 60−62 °C (dec); Anal. Calcd for
C16H18O2PS2HNEt3 (M.W. 439.61): C, 60.11; H, 7.80; S, 14.59; N, 3.19%. Found: C,
60.07; H, 7.77; S, 14.54; N, 3.13%. IR (KBr): 3397 b [N–H], 1196 s [v(P)–O–C], 870 s
[vP–O–(C)], 673 s [vP=S], 580 m [vP–S] cm−1.
2.2.2. [{(2,5-CH3)2C6H3O}2PS2HNEt3] (2). Compound 2 was prepared as white crystal-
line solid by similar procedure as described above for 1 using 2,5-dimethylphenol (4.39 g,
35.93 mM), P2S5 (2.00 g, 8.99 mM), and Et3N (1.82 g, 17.98 mM). The resulting solid was
dissolved in toluene and a few drops of n-hexane were added for recrystallization at room
temperature. Yield: 97% (7.60 g); m.p. 62–64 °C (dec); Anal. Calcd for C16H18O2PS2H-
NEt3 (M.W. 439.61): C, 60.11; H, 7.80; S, 14.59; N, 3.19%. Found: C, 60.08; H, 7.75; S,
14.55; N, 3.14%. IR (KBr): 3413 b [N–H], 1150 s [v(P)–O–C], 877 s [vP–O–(C)], 688 s
[vP=S], 575 m [vP–S] cm−1.
2.2.3. [{(3,4-CH3)2C6H3O}2PS2HNEt3] (3). Compound 3 was prepared as white crystal-
line solid by similar procedure as described for 1 using 3,4-dimethylphenol (4.39 g,
35.93 mM), P2S5 (2.00 g, 8.99 mM) and Et3N (1.82 g, 17.98 mM). The resulting solid was
dissolved in toluene and a few drops of n-hexane were added for recrystallization at room

2928
R. Khajuria et al.
temperature. Yield: 98% (7.68 g); m.p. 61–63 °C (dec); Anal. Calcd for C16H18O2PS2H-
NEt3 (M.W. 439.61): C, 60.11; H, 7.80; S, 14.59; N, 3.19%. Found: C, 60.07; H, 7.76; S,
14.54; N, 3.16%. IR (KBr): 3399 b [N–H], 1148 s [v(P)–O–C], 856 s [vP–O–(C)], 672 s
[vP=S], 574 m [vP–S] cm−1.
2.2.4. [{(3,5-CH3)2C6H3O}2PS2HNEt3] (4). Compound 4 was prepared as white crystal-
line solid by similar procedure as described for 1 using 3,5-dimethylphenol (4.39 g,
35.93 mM), P2S5 (2.00 g, 8.99 mM), and Et3N (1.82 g, 17.98 mM). The resulting solid was
dissolved in toluene and a few drops of n-hexane were added for recrystallization at room
temperature. Yield: 97% (7.60 g); m.p. 65–67 °C (dec); Anal. Calcd for C16H18O2PS2H-
NEt3 (M.W. 439.61): C, 60.11; H, 7.80; S, 14.59; N, 3.19%. Found: C, 60.09; H, 7.75; S,
14.53; N, 3.15%. IR (KBr): 3431 b [N–H], 1141 s [v(P)–O–C], 843 s [vP–O–(C)], 688 s
[vP=S], 578 m [vP–S] cm−1.
2.2.5. [{(2,4-CH3)2C6H3O}2PS2Na] (5). A weighed amount of sodium metal (0.42 g,
17.87 mM) was added to
a toluene solution of triethylammonium salt [{2,4-
(CH3)2C6H3O}2PS2HNEt3] (1) and the mixture was stirred for 3 h at ~55 °C, which
resulted in formation of white precipitates. The contents were cooled and then filtered by a
funnel fitted with a G-4 sintered disk. Finally, the residue was dried under reduced pressure
giving 5 as a white solid. Yield: 95.5% (6.18 g); m.p. 190–192 °C (dec); Anal. Calcd for
C16H18O2PS2Na: C, 53.32; H, 5.03; S, 17.79%. Found: C, 53.29; H, 4.95; S, 17.77%. IR
(KBr): 1172 s [v(P)–O–C], 832 s [vP–O–(C)], 652 s [vP═S], 570 m [vP–S] cm−1.
2.2.6. [{(2,5-CH3)2C6H3O}2PS2Na] (6). Compound 6 was prepared as white powdery
solid by similar procedure as described above for 5 using triethylammonium salt [{2,5-
(CH3)2C6H3O}2PS2HNEt3] (2) and sodium metal (0.42 g, 17.87 mM). Yield: 96.3%
(6.24 g); m.p. 192–194 °C (dec); Anal. Calcd for C16H18O2PS2Na: C, 53.32; H, 5.03; S,
17.79%. Found: C, 53.30; H, 4.99; S, 17.74%. IR (KBr): 1159 s [v(P)–O–C], 846 s [vP–O–
(C)], 670 s [vP═S], 556 m [vP–S] cm−1.
2.2.7. [{(3,4-CH3)2C6H3O}2PS2Na] (7). Compound 7 was prepared as white powdery
solid by similar procedure as described for 5 using triethylammonium salt [{3,4-
(CH3)2C6H3O}2PS2HNEt3] (3) and sodium metal (0.42 g, 17.87 mM). Yield: 97.6% (6.34 g);
m.p. 190–192 °C (dec); Anal. Calcd for C16H18O2PS2Na: C, 53.32; H, 5.03; S, 17.79%.
Found: C, 53.29; H, 4.96; S, 17.71%. IR (KBr): 1152 s [v(P)–O–C], 842 s [vP–O–(C)],
659 s [vP=S], 563 m [vP–S] cm−1.
2.2.8. [{(3,5-CH3)2C6H3O}2PS2Na] (8). Compound 8 was prepared as white powdery solid
by similar procedure as described for
5
using triethylammonium salt [{3,5-
(CH3)2C6H3O}2PS2HNEt3] (4) and sodium metal (0.42 g, 17.87 mM). Yield: 97.4% (6.31 g);
m.p. 194–196 °C (dec); Anal. Calcd for C16H18O2PS2Na: C, 53.32; H, 5.03; S, 17.79%.
Found: C, 53.27; H, 4.97; S, 17.76%. IR (KBr): 1149 s [v(P)–O–C], 836 s [vP–O–(C)],
661 s [vP═S], 559 m [vP–S] cm−1.

Diphenyldithiophosphates of cadmium
2929
2.3. Synthesis of complexes
2.3.1. [{(2,4-CH3)2C6H3O}2PS2]2Cd (9). To an aqueous solution of Cd(NO3)2·4H2O
(0.42 g, 1.36 mM), an aqueous solution of [{(2,4-CH3)2C6H3O}2PS2Na] (1.00 g, 2.77 mM)
was added in 1 : 2 M ratio with constant stirring at room temperature. A white solid mass
precipitated out immediately. After 30 min of stirring, the reaction contents were filtered
using an SG-4 sintered glass crucible to obtain [{(2,4-CH3)2C6H3O}2PS2]2Cd (9) as white
solid. The resulting solid was recrystallized from a chloroform/n-hexane mixture at room
temperature. Yield: 91.2% (0.97 g); m.p. 142–144 °C (dec); Anal. Calcd for
C32H36O4P2S4Cd (M.W. 787.24): C, 48.82; H, 4.61; S, 16.29; Cd, 14.28. Found: C, 48.79;
H, 4.59; S, 16.27; Cd, 14.25. IR (KBr): 1088 s [v(P)–O–C], 939 s [vP–O–(C)], 653 s
[vP–S]asym, 583 m [vP–S]sym, 262 w [vCd–S] cm−1.
2.3.2. [{(2,5-CH3)2C6H3O}2PS2]2Cd (10). Complex 10 was obtained as white solid by
similar procedure as described for 9 using Cd(NO3)2·4H2O (0.42 g, 1.36 mM) and [{(2,5-
CH3)2C6H3O}2PS2Na] (1.00 g, 2.77 mM). The resulting solid was recrystallized from a
chloroform/n-hexane mixture at room temperature. Yield: 93.4% (0.99 g); m.p. 144–146 °C
(dec); Anal. Calcd for C32H36O4P2S4Cd (M.W. 787.24): C, 48.82; H, 4.61; S, 16.29; Cd,
14.28. Found: C, 48.76; H, 4.56; S, 16.25; Cd, 14.24. IR (KBr): 1097 s [v(P)–O–C], 952 s
[vP–O–(C)], 669 s [vP–S]asym, 608 m [vP–S]sym, 263 w [vCd–S] cm−1.
2.3.3. [{(3,4-CH3)2C6H3O}2PS2]2Cd (11). Complex 11 was obtained as white solid by
similar procedure as described for 9 using Cd(NO3)2·4H2O (0.42 g, 1.36 mM) and [{(3,4-
CH3)2C6H3O}2PS2Na] (1.00 g, 2.77 mM). The resulting solid was recrystallized from a
chloroform/n-hexane mixture at room temperature. Yield: 91.8% (0.98 g); m.p. 143–145 °C
(dec); Anal. Calcd for C32H36O4P2S4Cd (M.W. 787.24): C, 48.82; H, 4.61; S, 16.29; Cd,
14.28. Found: C, 48.80; H, 4.59; S, 16.26; Cd, 14.22. IR (KBr): 1124 s [v(P)–O–C], 970 s
[vP–O–(C)], 668 s [vP–S]asym, 639 m [vP–S]sym, 264 w [vCd–S] cm−1.
2.3.4. [{(3,5-CH3)2C6H3O}2PS2]2Cd (12). Complex 12 was obtained as white solid by
similar procedure as described for 9 using Cd(NO3)2·4H2O (0.42 g, 1.36 mM) and [{(3,5-
CH3)2C6H3O}2PS2Na] (1.00 g, 2.77 mM). The resulting solid was recrystallized from a
chloroform/n-hexane mixture at room temperature. Yield: 92.6% (0.99 g); m.p. 144–146 °C
(dec); Anal. Calcd for C32H36O4P2S4Cd (M.W. 787.24): C, 48.82; H, 4.61; S, 16.29; Cd,
14.28. Found: C, 48.77; H, 4.58; S, 16.27; Cd, 14.25. IR (KBr): 1101 s [v(P)–O–C], 947 s
[vP–O–(C)], 653 s [vP–S]asym, 593 m [vP–S]sym, 260 w [vCd–S] cm−1.
2.4. Synthesis of adducts
2.4.1. [{(2,4-CH3)2C6H3O}2PS2]2Cd(NC5H5)2 (13). To a chloroform solution of [{(2,4-
CH3)2C6H3O}2PS2]2Cd (9) (1.00 g, 1.27 mM), chloroform solution of pyridine (0.20 g,
2.53 mM) was added dropwise with constant stirring at room temperature. Colorless solu-
tion changes to pale yellow within 15 min. The contents were stirred for a further 30 min at
room temperature. The solvent was then evaporated under vacuum, which results in 13 as
pale yellow solid. The resulting solid was recrystallized from a chloroform/n-hexane

2930
R. Khajuria et al.
mixture at room temperature. Yield: 88.6% (1.06 g); m.p. 162–164 °C (dec); Anal. Calcd
for C42H46N2O4P2S4Cd: C, 53.36; H, 4.90; S, 13.57; N, 2.96; Cd, 11.89. Found: C, 53.34;
H, 4.87; S, 13.55; N, 2.93; Cd, 11.86. IR (KBr): 1116 s [v(P)–O–C], 996 s [vP–O–(C)],
642 s [vP–S]asym, 586 m [vP–S]sym, 260 w [vCd–S], 540 w [vCd–N] cm−1.
2.4.2. [{(2,5-CH3)2C6H3O}2PS2]2Cd(NC5H5)2 (14). Complex 14 was obtained as pale
yellow solid by similar procedure as described for 13 using pyridine (0.20 g, 2.53 mM) and
[{(2,5-CH3)2C6H3O}2PS2]2Cd (10) (1.00 g, 1.27 mM). The resulting solid was recrystal-
lized from a chloroform/n-hexane mixture at room temperature. Yield: 87.4% (1.04 g); m.p.
164–166 °C (dec); Anal. Calcd for C42H46N2O4P2S4Cd: C, 53.36; H, 4.90; S, 13.57; N,
2.96; Cd, 11.89. Found: C, 53.32; H, 4.86; S, 13.56; N, 2.94; Cd, 11.86. IR (KBr): 1141 s
[v(P)–O–C], 960 s [vP–O–(C)], 645 s [vP–S]asym, 594 m [vP–S]sym, 263 w [vCd–S], 531 w
[vCd–N] cm−1.
2.4.3. [{(3,4-CH3)2C6H3O}2PS2]2Cd(NC5H5)2 (15). Complex 15 was obtained as pale
yellow solid by similar procedure as described for 13 using pyridine (0.20 g, 2.53 mM) and
11 (1.00 g, 1.27 mM). The resulting solid was recrystallized from a chloroform/n-hexane
mixture at room temperature. Yield: 88.3% (1.05 g); m.p. 162–164 °C (dec); Anal. Calcd
for C42H46N2O4P2S4Cd: C, 53.36; H, 4.90; S, 13.57; N, 2.96; Cd, 11.89. Found: C, 53.34;
H, 4.83; S, 13.53; N, 2.93; Cd, 11.83. IR (KBr): 1127 s [v(P)–O–C], 957 s [vP–O–(C)],
672 s [vP–S]asym, 621 m [vP–S]sym, 261 w [vCd–S], 533 w [vCd–N] cm−1.
2.4.4. [{(3,5-CH3)2C6H3O}2PS2]2Cd(NC5H5)2 (16). Complex 16 was obtained as pale
yellow solid by similar procedure as described for 13 using pyridine (0.20 g, 2.53 mM) and
12 (1.00 g, 1.27 mM). The resulting solid was recrystallized from a chloroform/n-hexane
mixture at room temperature. Yield: 89.4% (1.07 g); m.p. 163–165 °C (dec); Anal. Calcd
for C42H46N2O4P2S4Cd: C, 53.36; H, 4.90; S, 13.57; N, 2.96; Cd, 11.89. Found: C, 53.33;
H, 4.86; S, 13.52; N, 2.92; Cd, 11.84. IR (KBr): 1128 s [v(P)–O–C], 954 s [vP–O–(C)],
633 s [vP–S]asym, 615 m [vP–S]sym, 265 w [vCd–S], 521 w [vCd–N] cm−1.
2.5. X-ray crystallography
Crystallization of 4 was executed by dissolving solid in toluene and a few drops of
n-hexane were added, then solvents were allowed to evaporate slowly to obtain white single
crystals. The crystallization of 16 was achieved by slow evaporation of chloroform/n-
hexane mixture which resulted in pale yellow crystals at room temperature. The structures
of 4 and 16 were determined by single-crystal X-ray diffraction analysis. X-ray intensity
data were collected by using an X’calibur Oxford Diffraction single-crystal X-ray diffrac-
tometer with graphite monochromated Mo Kα radiation (λ = 0.71073 Å) and reduced with
CrysAlis RED [27]. Data were corrected for Lorentz, polarization and absorption factors.
The structure was solved by direct methods using SHELXS97 and refined by SHELXL97
[28]. The geometry of the molecule is determined by PLATON [29] and PARST [30] soft-
ware. All hydrogens were geometrically fixed and allowed to ride on their parent carbon,
with C–H distances of 0.93–0.97 Å and with Uiso(H) = 1.2Ueq(C), except for the methyl
group where Uiso(H) = 1.5Ueq(C). The crystallographic data are summarized in table 1.

Diphenyldithiophosphates of cadmium
2931
Table 1. Crystal data and structure refinements for 4 and 16.
Compound
4
16
Crystal system
Space group
Monoclinic
P21/c
Monoclinic
P21/c
Temperature, K
Empirical formula
Z
293(2)
C22H34NO2PS2
4
293(2)
C42H46CdN2O4P2S4
2
Formula weight
a (Å)
b (Å)
c (Å)
α (°)
439.59
945.39
8.1973(7)
11.6205(8)
25.6019(22)
90.00
12.0398(2)
14.4082(3)
15.3752(2)
90.00
β (°)
93.769(7)
90.00
2433.48(12)
1.20
125.4560(10)
90.00
2172.57(8)
1.445
γ (°)
V (Å3)
DCalcd (g/cm3)
F (0 0 0)
943.9
972
θ Range for data collection (°)
No. of collected reflections
No. of unique reflections
No. of data/restraints/parameters
R1, wR2 [I > 2σ(I)]
R1, wR2 (all data)
Goodness-of-fit on F2
3.60–26.00
9823
4781
4781/0/264
0.0624, 0.1382
0.0944, 0.1600
1.037
0.412/−0.31
971866
3.55–27.00
36,504
4736
4736/0/273
0.0295, 0.0728
0.0381, 0.0805
1.112
0.488/−0.520
971951
Largest diff. peak/hole (e Å−3
CCDC No.
)
3. Results and discussion
Literature reports describe the isolation of phenyl/tolyl dithiophosphates [25]. However,
there is no report available so far of similar compounds having disubstituted phenyl moiety.
Triethylammonium salt of disubstituted diphenyldithiophosphates has been isolated for the
first time by a facile reaction of 2,4-, 2,5-, 3,4- or 3,5-dimethylphenol with P2S5 in the
presence of triethylamine in 4 : 1 : 2 M ratio in toluene at room temperature. The triethyl-
ammonium salts corresponding to (ArO)2PS2HNEt3, where Ar = 2,4-(CH3)2C6H3 (1),
2,5-(CH3)2C6H3 (2), 3,4-(CH3)2C6H3 (3), and 3,5-(CH3)2C6H3 (4), are obtained as white
crystalline solid in quantitative yield after removing of excess solvent (scheme 1).
These triethylammonium salts (1–4) are fairly soluble in common organic solvents like
toluene, chloroform, methylene dichloride or benzene and are insoluble in carbon tetrachlo-
ride or n-hexane. The triethylammonium salts could easily be converted into sodium salts
as white solids by direct reaction with sodium metal in toluene in equimolar ratio under
strictly anhydrous atmosphere (scheme 2).
Sodium salts are soluble in water, DMSO, methanol, and ethanol, sparingly soluble in
chloroform, and insoluble in most other hydrocarbon solvents.
Toluene
4ArOH + P2S5 + 2Et3N
2(ArO)2PS2HNEt3
-H2S
(1-4)
[Ar = 2,4-(CH3)2C6H3 (1), 2,5-(CH3)2C6H3 (2), 3,4-(CH3)2C6H3 (3) and 3,5-(CH3)2C6H3 (4)]
Scheme 1.

2932
R. Khajuria et al.
Toluene
(ArO)2PS2HNEt3
+
Na
(ArO)2PS2Na
-1/2 H2
(1-4)
-Et3N
(5-8)
Scheme 2.
Cadmium diphenyldithiophosphates [{(ArO)2PS2}2Cd] (Ar = 2,4-(CH3)2C6H3, 2,5-
(CH3)2C6H3, 3,4-(CH3)2C6H3, and 3,5-(CH3)2C6H3) (9–12) have been isolated as white
solid by the reaction of sodium salts of O,O′-diphenyldithiophosphoric acids (5–8) and cad-
mium nitrate tetrahydrate, Cd(NO3)2·4H2O, in 2 : 1 M stoichiometry in water (scheme 3).
The donor stabilized cadmium diphenyldithiophosphates [{(ArO)2PS2}2Cd(NC5H5)2]
(Ar = 2,4-(CH3)2C6H3, 2,5-(CH3)2C6H3, 3,4-(CH3)2C6H3, and 3,5-(CH3)2C6H3) (13–16)
were prepared by the reaction of cadmium diphenyldithiophosphates (9–12) with pyridine
in 1 : 2 stoichiometry in chloroform (scheme 4).
All these complexes and adducts are soluble in common organic solvents and insoluble
in solvents like n-hexane and carbon tetrachloride.
3.1. IR spectra
IR spectra of 1–16 were interpreted on the basis of relevant literature reports [25, 31–34].
IR spectra have a broad absorption for [vN–H] at 3431–3397 cm−1 in 1–4, while these
absorptions were absent in 5–8. In 1–8, [v(P)–O–C] and [vP–O–(C)] were at 1196–1141
and 877–832 cm−1, respectively. Sharp to medium intensity bands at 688–652 and
580–556 cm−1 are assignable to [vP=S] and [vP–S] (asymmetric and symmetric) vibrations.
Comparison of IR spectra of the complexes and donor stabilized complexes with starting
materials has also shown significant changes. Bands due to [vN–H] vibrations are absent in
9–16. Two strong bands were observed at 1141–1088 and 996–939 cm−1 in 9–16, which
may be ascribed to [ν(P)–O–C] and [νP–O–(C)] of dimethyl diphenyldithiophosphate,
H2O
[{(ArO)2PS2}2Cd]
2(ArO)2PS2Na + Cd(NO3)2.4H2O
Stirring~30 min
(9-12)
(5-8)
-2NaNO3
[Ar = 2,4-(CH3)2C6H3 (9), 2,5-(CH3)2C6H3 (10), 3,4-(CH3)2C6H3 (11) and 3,5-(CH3)2C6H3 (12)]
Scheme 3.
Chloroform
[{(ArO)2PS2}2Cd(NC5H5)2]
[{(ArO)2PS2}2Cd] + 2C5H5N
Stirring~30 min
(13-16)
(9-12)
[Ar = 2,4-(CH3)2C6H3 (13), 2,5-(CH3)2C6H3 (14), 3,4-(CH3)2C6H3 (15) and 3,5-(CH3)2C6H3 (16)]
Scheme 4.

Diphenyldithiophosphates of cadmium
2933
respectively. The regions of IR spectra for P–S are of particular interest. Bands for
[vP–S]asym and [vP–S]sym of diphenyldithiophosphate in 9–16 were observed at 672–633
and 639–583 cm−1, respectively. This shift and appearance of closely spaced bands arising
from v(PS2) vibrations in 9–16 are quite diagnostic to propose bidentate bonding of dithio
moiety with cadmium. Appearance of new bands of νCd–S (in comparison to free ligand)
at 265–260 cm−1 indicates formation of cadmium–sulfur bonds [31]. The presence of bound
pyridine to cadmium via nitrogen in 13–16 can be supported by the existence of a band at
540–521 cm−1, assigned to νCd–N [32, 33].
3.2. 1H, 13C and 31P NMR spectra
1H NMR spectra of 1–16 exhibited phenyl and pyridine proton signals with the expected
peak multiplicities (table 2). For 9–16 chemical shifts of the methyl protons of the phenyl
rings were observed at 2.14–2.36 ppm as a very sharp 12 proton singlet (9–11 and 13–15)
and a 24 proton singlet in 12 and 16. The aromatic protons of the phenyl groups were
observed at 6.77–7.37 ppm with their characteristic splitting patterns. The chemical shifts
for protons due to pyridine are observed at 7.21–8.55 ppm.
The 13C NMR spectral data show the chemical shifts expected for the carbons present in
the molecule (table 2). 13C NMR spectra of 9–12 and adducts 13–16 show the chemical
shifts of carbons of phenyl rings with a marginal shift in their values compared to the parent
ligands (5–8). The chemical shift for the methyl (–CH3) carbon, attached to phenyl, was
found at 16.61–21.29 ppm. The carbon nuclei of the aryl groups have resonances at
118.69–139.08 ppm. The chemical shifts for C–O carbons were observed at 142.29–
151.58 ppm. The carbons on the pyridine rings in 13–16 have three peaks at 122.46–
149.69 ppm.
31P NMR spectra (proton-decoupled) displayed a single resonance in each case. The
31P NMR spectra of 9–12 have a singlet in each case in the upfield region 101.02–
101.86 ppm compared to the parent compounds (106.02–107.48 ppm) with a difference of
5–6 ppm. This shift may be attributed to bidentate dithiophosphate [35]. Adducts 13–16
showed the 31P chemical shift as a singlet in the downfield region 104.23–106.12 ppm com-
pared to 9–12 with a difference of 3–5 ppm, which can be attributed to binding of two pyri-
dines leading to six coordinate Cd. Occurrence of a singlet in each case indicated the
equivalent nature of phosphorus nuclei in the molecule. More upfield shift was observed in
four coordinate 9–12 than six coordinate 13–16 compared to the parent ligands. A summary
1
of H, 13C and 31P NMR data is presented in table 2.
3.3. Molecular and crystal structures of [{(3,5-CH3)2C6H3O}2PS2HNEt3] (4) and [{(3,5-
CH3)2C6H3O}2PS2]2Cd(NC5H5)2 (16)
ORTEP [36] view of triethylammonium salt 4 and adduct 16 with atomic labeling is shown
in figures 1 and 2, respectively. Selected bond lengths and angles of both compounds are
shown in tables 3 and 4, respectively. In the ORTEP diagram (figure 1), the expected dis-
torted tetrahedral environment around phosphorus can be clearly seen with two sulfurs and
two oxygens bound to phosphorus [figure 3(a)]. Compound 4 consists of triethyl ammo-
nium and O,O′-bis[3,5-dimethylphenyl]dithiophosphate, connected through N1–H1⋯S2
intermolecular hydrogen bond (figure 4). The N1–H1 bond length is fixed at 0.94 Å, while
the N1–S2 distance refines to 3.20(3) Å. This N1–S2 distance of 3.20(3) compares well

2934
R. Khajuria et al.
Table 2. 1H, 13C and 31P NMR spectroscopic data of 1–16.
S.
No. Compounds
1H, 13C and 31P Chemical shift (δ)
5
6
1
2
3
4
1H NMR (CDCl3, ppm): 1.25 (t, J = 14.4 Hz, 9H, CH3 of
Et3N), 2.28 (s, 6H, 2-CH3), 2.33 (s, 6H, 4-CH3), 3.12
(q, 6H, CH2 of Et3N), 6.98 (d, J = 8 Hz, 2H, H6), 7.00
(d, J = 8 Hz, 2H, H5), 7.55 (s, 2H, H3), 9.32 (s, 1H, –NH);
13C NMR (CDCl3, ppm): 8.55 (CH3 of Et3N), 17.48
(2-CH3), 20.82 (4-CH3), 46.18 (CH2 of Et3N), 114.96 (C6),
121.47 (C2–CH3), 127.21 (C5), 130.59 (C4–CH3), 133.18
(C3), 151.97 (C1–O); 31P NMR (CDCl3, ppm): 106.95 (s)
1H NMR (CDCl3, ppm): 1.25 (t, J = 14.4 Hz, 9H, CH3 of
Et3N), 2.17 (s, 6H, 2-CH3), 2.22 (s, 6H, 5-CH3), 3.12
(q, 6H, CH2 of Et3N), 6.77 (d, J = 7.6 Hz, 2H, H3), 7.02 (d,
4
4
H3C
H3C
O
1 O3
1
3
26CH
PS
2 HNEt3
5
3
2 CH3
H3C
5
6
4
O
1
3
2
2
H3C
PS2 HNEt3
5
6CH3
J = 7.6 Hz, 2H, H4), 7.41 (s, 2H, H6), 9.03 (s, 1H, –NH); 13
C
4
O
1
NMR (CDCl3, ppm): 8.53 (CH3 of Et3N), 16.63 (2-CH3),
20.90 (5-CH3), 46.28 (CH2 of Et3N), 121.46 (C6), 126.64
(C4), 127.32 (C2–CH3), 131.11 (C3), 136.83 (C5–CH3),
149.56 (C1–O); 31P NMR (CDCl3, ppm): 106.40 (s)
3
CH3
1H NMR (CDCl3, ppm): 1.26 (t, J = 14.4 Hz, 9H, CH3 of
Et3N), 2.21 (s, 6H, 3-CH3), 2.23 (s, 6H, 4-CH3), 3.13
(q, 6H, CH2 of Et3N), 7.06 (d, J = 7.6 Hz, 2H, H6), 7.17
(s, 2H, H2), 7.37 (d, J = 8 Hz, 2H, H5), 9.20 (s, 1H, –NH);
13C NMR (CDCl3, ppm): 8.57 (CH3 of Et3N), 19.12 (4-CH3),
19.96 (3-CH3), 46.31 (CH2 of Et3N), 116.77 (C6), 119.18
(C2), 130.30 (C4–CH3), 132.09 (C5), 137.14 (C3–CH3),
150.56 (C1–O); 31P NMR (CDCl3, ppm): 106.02 (s)
5
6
4
H3C
O
1
H3C3
2
6
PS2
HNEt3
5
4
H3C
O
1
H3C 3
2
1H NMR (CDCl3, ppm): 1.29 (t, J = 14.4 Hz, 9H, CH3 of
Et3N), 2.29 (s, 12H, 3,5-(CH3)2), 3.15 (q, 6H, CH2 of Et3N),
6.75 (s, 4H, H2,6), 7.03 (s, 2H, H4), 9.25 (s, 1H, –NH);
13C NMR (CDCl3, ppm): 8.50 (CH3 of Et3N), 21.35
(3,5-(CH3)2), 46.21 (CH2 of Et3N), 119.72 (C2,6), 125.70 (C4),
138.40 (C3,5-CH3), 152.58 (C1–O); 31P NMR (CDCl3, ppm):
106.78 (s)
H3C
5
6
4
O
1
3
2
H3C
H3C
PS2
PS2
HNEt3
Na
5
6
4
O
1
H3C 3
2
5
6
5
6
7
8
1H NMR (DMSO-d6, ppm): 2.07 (s, 6H, 2-CH3), 2.17 (s, 6H,
4-CH3), 6.47 (d, J = 8 Hz, 2H, H5), 6.73 (s, 2H, H3), 6.80
(d, J = 8 Hz, 2H, H6); 13C NMR (DMSO-d6, ppm): 17.00
(2-CH3), 19.72 (4-CH3), 117.66 (C6), 122.74 (C2–CH3),
126.70 (C5), 127.25 (C4–CH3), 131.01 (C3), 161.97 (C1–O);
31P NMR (DMSO-d6, ppm): 107.48 (s)
4
H3C
H3C
O
1
3
2
5
6CH3
4
O
1
3
2
CH3
1H NMR (DMSO-d6, ppm): 2.23 (s, 6H, 2-CH3), 2.28 (s, 6H,
5-CH3), 6.82 (d, J = 7.6 Hz, 2H, H3), 7.11 (d, J = 7.6 Hz, 2H,
H4), 7.47 (s, 2H, H6); 13C NMR (DMSO-d6, ppm): 17.12
(2-CH3), 20.32 (5-CH3), 123.52 (C6), 127.63 (C4), 128.47
H3C
5
6
4
O
1
3
2
2
H3C
PS2
Na
5
6CH3
4
5
6
(C2–CH3), 131.62 (C3), 137.42 (C5–CH3), 151.42 (C1–O); 31
P
O
1
4
3
H3C
O
O
1
C2H3
H3C3
NMR (DMSO-d6, ppm): 106.62 (s)
PS2
1H NMR (DMSO-d6, ppm): 2.15 (s, 6H, 4-CH3), 2.16 (s, 6H,
3-CH3), 6.97 (d, J = 7.6 Hz, 2H, H6), 7.00 (s, 2H, H2), 7.36
(d, J = 8 Hz, 2H, H5); 13C NMR (DMSO-d6, ppm): 19.14
(4-CH3), 20.01 (3-CH3), 117.34 (C6), 119.13 (C2), 122.96
Na
5
6
4
H3C
1
2
H3C 3
(C4–CH3), 127.84 (C5), 136.62 (C3–CH3), 151.42 (C1–O); 31
P
NMR (DMSO-d6, ppm): 107.31(s)
H3C
1H NMR (DMSO-d6, ppm): 1.99 (s, 12H, 3,5-(CH3)2), 6.54
(s, 4H, H2,6), 6.73 (s, 2H, H4); 13C NMR (DMSO-d6, ppm):
23.12 (3,5-(CH3)2), 122.56 (C2,6), 128.64 (C4), 142.33
(C3,5-CH3), 154.53 (C1–O); 31P NMR (DMSO-d6, ppm):
106.59 (s)
5
6
4
O
1
3
2
6
H3C
H3C
PS
2 Na
5
4
O
1
H3C 3
2
(Continued)

Diphenyldithiophosphates of cadmium
2935
Table 2. (Continued).
S.
No. Compounds
1H, 13C and 31P Chemical shift (δ)
5
6
6
5
9
1H NMR (CDCl3, ppm): 2.20 (s, 12H, 2-CH3), 2.36 (s, 12H,
4-CH3), 7.01 (d, J = 8 Hz, 4H, H6), 7.07 (d, J = 8 Hz, 4H,
H5), 7.37 (s, 4H, H3); 13C NMR (CDCl3, ppm): 17.72
(2-CH3), 20.81 (4-CH3), 120.83 (C6), 127.44 (C2–CH3),
129.96 (C5), 132.13 (C4–CH3), 135.42 (C3), 146.84 (C1–O);
31P NMR (CDCl3, ppm): 101.46 (s)
4
S
S
S
4
H3C
H3C
O
1
O
CH3
CH3
1
3
2
2
3
5
2
6
Cd
P
5
P
6CH3
H3C
4
4
1
O
CH3
S
O
1
3
3
2
H3C
10
H3C
1H NMR (CDCl3, ppm): 2.27 (s, 12H, 2-CH3), 2.29 (s, 12H,
5-CH3), 6.96 (d, J = 7.6 Hz, 4H, H3), 7.12 (d, J = 7.6 Hz, 4H,
H4), 7.31 (s, 4H, H6) ppm; 13C NMR (CDCl3, ppm): 16.61
(2-CH3), 20.99 (5-CH3), 121.46 (C6), 126.62 (C4), 127.31
CH3
5
6
5
6
4
S
S
S
S
4
O
1
O
1
3
3
2
2
3
H3C
2
2
Cd
P
CH3
P
5
6CH3
5
6
H3C
4
(C2–CH3), 131.24 (C3), 136.91 (C5–CH3), 149.51 (C1–O); 31
P
O
1
4
O
1
3
NMR (CDCl3, ppm): 101.26 (s)
CH3
H3C
1H NMR (CDCl3, ppm): 2.28 (s, 12H, 4-CH3), 2.31 (s, 12H,
3–CH3), 6.86 (d, J = 7.6 Hz, 4H, H6), 6.95 (s, 4H, H2), 7.06
(d, J = 8 Hz, 4H, H5); 13C NMR (CDCl3, ppm): 19.20
(4-CH3), 19.93 (3-CH3), 118.69 (C6), 122.46 (C2), 130.44
5
5
5
6
6
11
12
4
4
S
S
S
S
H3C
O
1
O
CH3
1
1
3
3
3
3
2
6
2
Cd
P
P
H3C
5
6
CH3
4
4
H3C
O
1
CH3
O
2
(C4–CH3), 133.88 (C5), 138.10 (C3–CH3), 149.29 (C1–O); 31
P
2
H3C
CH3
NMR (CDCl3, ppm): 101.02 (s)
1H NMR (CDCl3, ppm): 2.35 (s, 24H, 3,5-(CH3)2), 6.77
(s, 8H, H2,6), 7.00 (s, 4H, H4); 13C NMR (CDCl3, ppm):
H3C
CH3
4
5
5
6
6
4
S
O
1
S
O
1
3
3 CH3
2
6
21.28 (3,5-(CH3)2), 119.35 (C2,6), 126.58 (C4), 138.95 (C3,5-
2
H3C
CH3), 151.17 (C1–O); 31P NMR (CDCl3, ppm): 101.86 (s)
Cd
P
P
5
5
6
CH3
H3C
4
4
S
S
O
1
O
1
3
3
2
2
CH3
H3C
1H NMR (CDCl3, ppm): 2.18 (s, 12H, 2-CH3), 2.25 (s, 12H,
4-CH3), 7.00 (d, J = 8 Hz, 4H, H6), 7.06 (d, J = 8 Hz, 4H,
H5), 7.26 (t, J = 14.4 Hz, 4H, H2,4, C5H5 N), 7.35 (s, 4H, H3),
7.68 (t, J = 13.6 Hz, 2H, H3, C5H5 N), 8.52 (d, J = 8 Hz, 4H,
H1,5, C5H5 N); 13C NMR (CDCl3, ppm): 17.70 (2-CH3),
20.78 (4-CH3), 121.13 (C6), 126.42 (C2–CH3), 128.31 (C5),
131.26 (C4–CH3), 134.32 (C3), 149.63 (C1–O), 122.46,
136.41, 149.43 (C5H5 N); 31P NMR (CDCl3, ppm): 106.12 (s)
3
2
1
13
14
15
4
5
5
N
6
6
5
4
4
4
S
S
S
H3C
H3C
O
1
O
CH3
1
3
2
3
2
6
Cd
P
5
P
P
6CH3
H3C
5
4
O
CH3
S
1
O
CH3
1
3
2
3
2
N
5
H3C
1
2
4
3
3
1H NMR (CDCl3, ppm): 2.19 (s, 12H, 2-CH3), 2.24 (s, 12H,
5-CH3), 6.94 (d, J = 7.6 Hz, 4H, H3), 7.14 (d, J = 7.6 Hz, 4H,
H4), 7.24 (t, J = 14 Hz, 4H, H2,4, C5H5 N), 7.29 (s, 4H, H6),
7.62 (t, J = 12.8 Hz, 2H, H3, C5H5 N), 8.51 (d, J = 8.4 Hz,
4H, H1,5, C5H5 N); 13C NMR (CDCl3, ppm): 17.42 (2-CH3),
19.63 (5-CH3), 121.32 (C6), 125.43 (C4), 127.10 (C2–CH3),
130.46 (C3), 135.42 (C5–CH3), 149.50 (C1–O) 122.86,
136.23, 149.62 (C5H5 N); 31P NMR (CDCl3, ppm): 104.21(s)
2
4
1
5
N
H3C
CH3
5
6
5
6
4
S
S
S
4
O
1
O
1
3
3
2
2
3
H3C
2
Cd
P
P
CH3
5
6CH3
5
6
H3C
4
O
S
1
4
O
1
3
N
3
2
5
CH3
1
2
H3C
4
1H NMR (CDCl3, ppm): 2.14 (s, 12H, 4-CH3), 2.17 (s, 12H,
3-CH3), 6.98 (d, J = 7.6 Hz, 4H, H6), 7.07 (s, 4H, H2), 7.21
(t, J = 14.4 Hz, 4H, H2,4, C5H5 N), 7.31 (d, J = 8 Hz, 4H, H5),
7.66 (t, J = 14 Hz, 2H, H3, C5H5 N), 8.55 (d, J = 8 Hz, 4H,
H1,5, C5H5 N); 13C NMR (CDCl3, ppm): 19.18 (4-CH3),
19.89 (3-CH3), 119.07 (C6), 124.00 (C2), 130.06 (C4–CH3),
132.87 (C5), 137.46 (C3–CH3), 149.79 (C1–O),122.90,
136.71, 149.69 (C5H5 N); 31P NMR (CDCl3, ppm): 106.11(s)
2
1
4
5
N
5
5
6
5
5
6
4
4
S
S
S
H3C
O
1
O
CH3
1
1
H3C 3
3 CH3
2
6
Cd
2
P
6
4
4
H3C
O
1
O
CH3
S
3
3 CH3
2
N
5
1
2
2
H3C
4
3
(Continued)

2936
R. Khajuria et al.
Table 2. (Continued).
S.
No. Compounds
1H, 13C and 31P Chemical shift (δ)
1H NMR (CDCl3, ppm): 2.31 (s, 24H, 3,5-(CH3)2), 6.86
3
16
2
4
(s, 8H, H2,6), 7.03 (s, 4H, H4), 7.28 (t, J = 14.4 Hz, 4H, H2,4
,
H3C
5
CH3
1
5
6
5
6
N
C5H5 N), 7.77 (t, J = 13.6 Hz, 2H, H3, C5H5 N), 8.50
(d, J = 4.4 Hz, 4H, H1,5, C5H5 N); 13C NMR (CDCl3, ppm):
21.29 (3,5-(CH3)2), 119.48 (C2,6), 126.88 (C4), 139.08
(C3,5-CH3), 151.58 (C1–O),124.38, 137.52, 149.60 (C5H5 N);
31P NMR (CDCl3, ppm): 104.23 (s)
4
4
S
O
1
S
O
O
1
3
3
2
6
2
H3C
H3C
CH3
Cd
P
P
5
5
CH3
6
4
4
S
S
O
1
1
H3C 3
3CH3
N
2
5
4
2
1
2
3
Notes: s = singlet, d = doublet, q = quartet, m = multiplet.
Figure 1. ORTEP view of 4 showing the atom-labeling scheme. Displacement ellipsoids are drawn at the 40%
probability level.
with the values of 3.25(5) and 3.249(6) Å reported for [Et3NH]+[(2-MeC6H4O)2PS2]− [37]
and
[38], respectively.
P1–S1 and P1–S2 bond lengths in 4 [P1–S1 = 1.9389(12) and P1–S2 = 1.9586(12) Å]
are comparable with the lengths of a single (2.14 Å) and double (1.94 Å) P–S bond [19]. In
16, phosphorus–sulfur bonds [P1–S1 = 1.9759(8) and P1–S2 = 1.9779(8) Å] are intermedi-
ate between single and double P–S bonds, which suggests that the negative charge is
delocalized over the S–P–S fragment. The S1–P1–S2 bond angle in {(3,5-
CH3)2C6H3O}2PS2HNEt3 [119.31(6)°] is slightly smaller than those of another literature
reported triethylammonium salt, [Et3NH]+[CH2{6-t-Bu-4-Me-C6H4O}2P(S)(S)]− [38].

Diphenyldithiophosphates of cadmium
2937
Figure 2. ORTEP view of 16 showing the atom-labeling scheme. Displacement ellipsoids are drawn at the 40%
probability level.
Table 3. Selected bond lengths (Å) and angles (°) for 4.
Bond distances
P1–O1
P1–S1
O2–C7
N1–C19
N1–C17
1.610(2)
1.9389(12)
1.386(4)
1.471(5)
1.538(6)
P1–O2
P1–S2
O1–C1
N1–C21
C20–C19
1.622(2)
1.9586(12)
1.393(4)
1.496(5)
1.501(7)
Bond angles
O1–P1–O2
O2–P1–S1
102.33(12)
105.96(9)
111.06(9)
127.09(19)
116.1(4)
112.7(3)
123.7(3)
113.0(4)
O1–P1–S1
O1–P1–S2
S1–P1–S2
C1–O1–P1
C19–N1–C17
C2–C1–O1
N1–C19–C20
N1–C21–C22
112.57(10)
104.41(9)
119.31(6)
129.01(19)
110.5(4)
115.3(3)
112.8(4)
114.1(3)
O2–P1–S2
C7–O2–P1
C19–N1–C21
C21–N1–C17
C6–C1–O1
C18–C17–N1
The crystal structure of 16 consists of two dithiophosphate and two pyridine units linked
to cadmium. The coordination geometry is based on an octahedron within a trans-N2S4
donor set [figure 3(b)]. Cd(II) of 16 is surrounded by two chelating dithiophosphate anions,
situated on a crystallographic center of inversion. The two pyridines are coordinated to cad-
mium axially. The cadmium attached to the pyridine ring is slightly above the plane of the
pyridine ring (the value of the deviation being 0.2562). The dihedral angle between the
pyridine ring (N1/C17/C18/C19/C20/C21) and the plane through cadmium (Cd1/S1/P1/S2)

2938
R. Khajuria et al.
Table 4. Important bond lengths (Å) and angles (°) for 16.
Bond distances
Cd1–N1
Cd1–S1
Cd1–S2
P1–O1
P1–O2
P1–S1
2.3973(19)
2.7282(5)
2.6741(5)
1.5947(16)
1.5943(16)
1.9759(8)
1.9779(8)
1.407(3)
P1–S2
O1–C1
O2–C9
N1–C21
N1–C17
1.398(3)
1.324(3)
1.321(3)
Bond angles
N1′–Cd1–N1
N1′–Cd1–S2
N1′–Cd1–S1
S2′–Cd1–S1′
N1′–Cd1–S1′
S2′–Cd1–S1′
O2–P1–O1
S2–Cd1–S1
O2–P1–S1
O2–P1–S2
C17–N1–C21
P1–S2–Cd1
C9–O2–P1
180.0
N1′–Cd1–S2
S2′–Cd1–S2
N1′–Cd1–S1′
S2′–Cd1–S1
S1′–Cd1–S1
O1–P1–S1
90.80(5)
180.00(2)
92.52(5)
103.663(17)
180.000
113.20(7)
105.67(7)
115.22(3)
81.99(2)
124.01(14)
120.83(17)
121.22(18)
122.4(3)
89.20(5)
87.48(5)
76.336(17)
92.52(5)
76.336(17)
98.29(8)
76.337(17)
111.05(8)
112.06(8)
117.6(2)
83.38(2)
128.64(14)
123.4(3)
O1–P1–S2
S1–P1–S2
P1–S1–Cd1
C1–O1–P1
C17–N1–Cd1
C21–N1–Cd1
N1–C17–C18
N1–C21–C20
Figure 3. (a) Tetrahedral view of 4 and (b) Octahedral view of 16.
is 78.72(1)°. The S1–Cd1–S2 and S1–P1–S2 angles [76.336(17)° and 115.22(3)°] are nor-
mal [39]. The Cd–S bonds lengths [2.7282(5) and 2.6741(5) Å] of 16 are in agreement with
those reported for other analogous complexes Cd{S2P(OCH2CH2Ph)2}2·bipy [2.7958(14)
and 2.5985(13) Å] [39], Cd{S2P(OCy)2}2 [2.526(8) and 2.660(8)] [17], and Cd[(iPrO)2P-
S2]2(py)2 [2.694(1) and 2.704(1)] [24]. The Cd–N bond distance in 16 is 2.397(19) Å which
is comparable to the value found in Cd[(iPrO)2PS2]2(py)2 [2.399(3) Å] [24]. The phospho-
rus is surrounded by two sulfurs and two oxygens to furnish a distorted tetrahedral geome-
try. The P–O bond in 16 is slightly shorter than those in 4, although all of these are in the

Diphenyldithiophosphates of cadmium
2939
Figure 4. Packing diagram viewed down the a-axis for 4 showing hydrogen bonding.
Table 5. Geometry of intramolecular and intermolecular interactions for 4.
D–H⋯A
D–H (Å)
H⋯A (Å)
D⋯A (Å)
θ [D–H⋯A (°)]
C6–H6⋯O2i
N1–H1⋯S2ii
0.930
0.940
2.50(2)
2.30(4)
3.13(4)
3.20(3)
124.8(2)
160.75(3)
Note: Symmetry codes: (i) x, y, z; (ii) 1 − x, 1/2 + y, 1/2 − z.
expected range. Compound 4 has only S2 involved in hydrogen bonding (table 5) while no
classical hydrogen bonds are present in 16.
3.4. Thermogravimetric analysis
The thermal behavior of [{(3,5-CH3)2C6H3O}2PS2]2Cd(NC5H5)2] (16) displayed a thermol-
ysis step that covers a temperature range from 150 to 900 °C (figure 5). The rate of weight
loss increases steeply at 322 °C. The weight loss of 65.09% (Calcd wt. loss = 64.61%) cor-
responds to the formation of bis(dithio-meta-phosphato)cadmium(II) [Cd(S2PO)2] which is
diagnostic for dithiophosphate complexes [40]. The temperature range for formation of [Cd
(S2PO)2] is from 300 to 350 °C. The formation of final residue CdSO4 contaminated with
other thermolysis products was obtained with the weight loss of 77.60% (Calcd wt.
loss = 77.95%) at 891 °C. The DTA curve shows an endotherm which signifies the thermal
decomposition of the organic part of the dithiophosphate ligand at 160 °C.

2940
R. Khajuria et al.
Figure 5. TGA/DTA curve of 16.
4. Conclusion
We have synthesized and characterized new disubstituted diphenyldithiophosphates and
their cadmium(II) complexes by elemental analysis, IR, NMR (1H, 13C and 31P) and single-
crystal X-ray analysis. In the triethylammonium salt [{(3,5-CH3)2C6H3O}2PS2HNEt3],
phosphorus of the anion is tetrahedrally bonded to two S and two O atoms. The cation–
anion N–H⋯S hydrogen bond interactions in 4 stabilized the structure. The complex [{(3,5-
CH3)2C6H3O}2PS2]2Cd(NC5H5)2 has bidentate diphenyldithiophosphate ions with two sul-
furs coordinated to cadmium. Each forms a four-membered chelate ring in the equatorial
plane as a [CdS2] unit. Two pyridines are axially coordinated to cadmium.
Supplementary material
CCDC 971866 and 971951 contain the supplementary crystallographic data for 4 and 16.
These data can be obtained free of charge via http://www.ccdc.cam.ac.uk/conts/retrieving.
html, or from the Cambridge Crystallographic Data Center, 12 Union Road, Cambridge
CB2 1EZ, UK; Fax: (+44) 1223-336-033 or E-mail: deposit@ccdc.cam.ac.uk.
Acknowledgments
The authors are grateful to the NMR laboratory Department of Chemistry, University of
Jammu, Jammu for providing NMR spectral facilities (PURSE program). One of the authors
(Rajni Kant) acknowledges the DST for the single-crystal X-ray diffractometer as a
National Facility under Project No. SR/S2/CMP-47/2003.

Diphenyldithiophosphates of cadmium
2941
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