Synthesis and characterization of organoarsenic(III) derivatives with 2-aminocyclopentene 1-carbodithioc acid and with their nitrogen/sulfur alkyl derivatives

Article abstract of DOI:10.1080/10426500701521647

Phenylarsenic(III) Dimethoxide reacts with N-/S- alkyl of 2-aminocyclopentene 1- carbodithioic acid and its nitrogen-/sulfur-alkyl derivatives in 1:2 and 1:1 molar ratio yields some new complexes and addition complexes of the type: [image omitted] where R' = H,CH3,C2H5,C4H9 and R = CH3 and CH2N(C2H5). Reactants were mixed in 1:1 and 1:2 molar ratios and the resulting mixture was refluxed for 5 to 6 h to ensure completion of the reaction. Sodium chloride precipitated was filtered off. Yellow to dark brown colored solids were isolated; these complexes were found to be soluble in common organic solvents (e.g., CHCl3, etc.) These complexes and additional complexes have been characterized by physicochemical and spectroscopic studies. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/10426500701521647

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Phosphorus, Sulfur, and Silicon
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Synthesis and Characterization
of Organoarsenic(III)
Derivatives with 2-
Aminocyclopentene 1-
Carbodithioc Acid and with
Their Nitrogen/Sulfur Alkyl
Derivatives
a
a
a
R. Rathore , N. Harkut & P. N. Nagar
a
Department of Chemistry , University of
Rajasthan , Jaipur, India
Published online: 03 Dec 2007.
To cite this article: R. Rathore , N. Harkut & P. N. Nagar (2007) Synthesis and
Characterization of Organoarsenic(III) Derivatives with 2-Aminocyclopentene 1-
Carbodithioc Acid and with Their Nitrogen/Sulfur Alkyl Derivatives, Phosphorus,
Sulfur, and Silicon and the Related Elements, 182:12, 2809-2820, DOI:
10.1080/10426500701521647
To link to this article: http://dx.doi.org/10.1080/10426500701521647
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Phosphorus, Sulfur, and Silicon, 182:2809–2820, 2007
Copyright © Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426500701521647
Synthesis and Characterization of Organoarsenic(III)
Derivatives with 2-Aminocyclopentene 1-Carbodithioc
Acid and with Their Nitrogen/Sulfur Alkyl Derivatives
R. Rathore
N. Harkut
P. N. Nagar
Department of Chemistry, University of Rajasthan, Jaipur, India
Phenylarsenic(III) Dimethoxide reacts with N-/S- alkyl of 2-aminocyclopentene 1-
carbodithioic acid and its nitrogen-/sulfur-alkyl derivatives in 1:2 and 1:1 molar
ratio yields some new complexes and addition complexes of the type:
(
CH2)3
ꢀ
- - ----------
PhAs[R (H)NC −−−−−−−− −− CC(S)S]2 and
CH2)3
- ----------
(
-
PhAs[(OMe)2[R(H)NC −−−−−−−− −− CC(S)SR]
ꢀ
where R = H, CH , C H , C H and R= CH and CH N(C H ). Reactants
3
2
5
4
9
3
2
2
5
were mixed in 1:1 and 1:2 molar ratios and the resulting mixture was refluxed for 5
to 6 h to ensure completion of the reaction. Sodium chloride precipitated was filtered
off. Yellow to dark brown colored solids were isolated; these complexes were found
to be soluble in common organic solvents (e.g., CHCl , etc.) These complexes and
3
additional complexes have been characterized by physicochemical and spectroscopic
studies.
Keywords 2-Aminocyclopentene1-carbodithioic acid; phenylarsenic(III) dimethoxide
INTRODUCTION
A number of metal complexes of 2-aminocyclopentene 1-carbodithioc
acid and its nitrogen/sulfur alkyl derivatives have been reported in
the literature during the last few decades and interesting chemical
1
–3
bonding patterns have been observed with various metals.
These
1
ligands bind with the metals either in monodentate, or in bidentate
fashion; sometimes they show ambidentate behavior, as well. In some
2
cases, these bind with the metal through sulfur-sulfur coordination
4
and sulfur-nitrogen coordination. A survey of the literature reveals
Received February 4, 2007; accepted May 24, 2007.
Address correspondence to P. N. Nagar, Department of Chemistry, University of
Rajasthan, Jaipur 302004, India. E-mail: neelam gats2006@rediffmail.com
2809

2
810
R. Rathore et al.
that only stray references5 are available in the literature on the syn-
thesis and characterization of organoarsenic (III) derivatives. In view
of the above, we were interested in synthesizing and characterizing
some organo-arsenic(III) derivatives with the abovementioned ligands.
–8
5
,6
Recently, arsenic-sulfur (trialkyltri) thioarsenites
and complexes
7
of N-aryl2-mercaptoacetamides with cyclopentadienyl titanium (IV )
have also been reported, which reflects interest in arsenic-sulfur ligand
chemistry of metals.
RESULTS AND DISCUSSION
Phenylarsenic(III) derivatives of 2-aminocyclopentene 1-carbodithioic
acid and its N-alkyl derivatives have been synthesized by reacting
PhAs(OMe)2 (prepared in situ of reacting PhAsCl2with NaOMe) with 2-
Aminocyclopentene1- carbodithioc acid, and its N-/S-alkyl derivatives
in anhydrous benzene solution under refluxing for 6 h with vigorous
stirring (Eq. 1):
ꢀ
ꢁ
2
NaOMe + PhAsCl2 → PhAs OMe + 2NaCl ↓
2
(CH2)3
6 6
C H
ꢀ
-
- ----------
PhAs[(OMe)2 + 2[R (H)NC --------------------------- CC(S)SH] −− −→
(
CH2)3
ꢀ
-
- ----------
PhAs[R (H)NC --------------------------- C]C(S)S]2 + 2MeOH
(1)
ꢀ
where R = H, CH3, C2H5 and C4H9.
Where as the addition complexes of phenylarsenic (III) dimethoxide
with S-alkyl esters of 2-Aminocyclopentene – 1-carbodithioc acid have
been synthesized by the reaction of PhAs(OMe)2 with the corresponding
ligands in 1:1 molar ratio in refluxing anhydrous benzene solution for
∼
8 h (Eq. 2):
ꢀ
ꢁ
PhAsCl2 + 2NaOMe → PhAs OMe + 2NaCl ↓
2
(
CH2)3
6 6
C H
-
(
- ----------
PhAs[(OMe)2 + [H(H)NC --------------------------- CC(S)SR] −− −→
PhAs[(OMe)2[H(H)NC --------------------------- C]C(S)SR]
CH2)3
-
- ----------
(2)
where R = CH3, CH2NC2H5.
The substituted products and the addition complexes of pheny-
larsenic(III) of 2-aminocyclopentene-1-carbodithioicacid and its
nitrogen-alkyl derivatives and phenyl-arsenic(III) dimethoxide with
S-alkyl esters of 2-aminocyclopentene1-carbodithioicacid have been
synthesized and isolated after filtering off sodium chloride thus formed
during the course of the reaction (Table 1). After removing the benzene

Organosarsenic(III) Derivatives with Aminocyclopentene
2811
a yellow to dark red solids are obtained, which have been purified by
dissolving in chloroform and petroleum ether.
It is interesting to mention here that it appears that in these reac-
tions the sulfur being less electronegative (2.44) element in comparison
to N(3.0), on one hand and on the other hand in N-alkyl derivatives
the donor (+I) capacity of nitrogen is substantially enhanced by the
presence of alkyl group on nitrogen atom. This decreases the ionocity of
N-H bond thus increase the chances of coordination of nitrogen to metal
atom. It also appears that thiols are more acidic than alcohols. The free
S-H group seem to be acidic in nature also due to conjugation between
carbon atom of the ring and carbon-sulfur double bond ( C C C S)
that facilate substitution reaction between phenyl arsenic dimethoxide.
While in S-alkyl derivatives there are no chances of substitution due
to absence of S H protons, the formation of 1:2 addition complexes is
completely ruled out because the presence of loan pair of electron on
arsenic atom repeals back or do not accept another ligand molecule.
IR Spectra
The IR spectra of these complexes have been recorded in the range of
−
1
4
000–400 and 4000–200 cm
.
−
1
A broad band appearing in the range 3350–3360 cm and 1610–1605
cm in the spectra of the compounds and the addition compounds may
be assigned to NH stretching and NH deformation mode. No significant
−
1
9
shift has been observed in NH/NH2 mode in complexes when compared
to its position in parent ligand. This suggests the non-participation of
amino groups of ligands in complexation.
−
1
A broad absorption bands observed at 2340–2500 cm in the spec-
tra of 2-amino cyclopentene 1-carbodithioicacid, and its nitrogen alkyl
9
derivatives, assigned to SH group, are found to be absent in the cor-
responding compounds. This indicates the deprotonation of SH group
on complexation. This has been further supported by the appearance
−
1
of new absorption band in the range 325–356 cm , which has been
assigned to As-S.
A strong absorption band has been observed in the region 920–970
−
1
cm in the organoarsenic(III) derivatives of 2-aminocyclopentene-1-
carbodithioicacid and its N-alkyl derivatives which may be assigned to
asym CSS mode.1
0,11
Appearance of single band for asymmetric CSS
in the region indicates the involvement of both the sulfur atoms in the
bonding a band due to sym CSS stretching vibration has been observed
−1.
in the region at 605–610 cm
The appearance of two absorption bands for asym CSS in the
−1
range of 940–960 cm in the phenylarsenic(III) compounds of S-alkyl

2
812
R. Rathore et al.
derivatives of 2-aminocyclopentene −1-carbodithioicacid in the range
−
1
of 940–960 cm indicates the participation of only one sulfur of C(S)SR
group in bonding .this has been further supported by the appearance
−1
of a new absorption band at 350 cm assigned to As-S bond.
The other absorption bands have been observed at their expected
position mentioned in Table II.
PMR Spectra
PMR spectra of the newly synthesized derivatives have been recorded in
the CDC13 solution and the chemical shift values have been tabulated
in Table III. The PMR spectra of the ligands 2-aminocyclopentene-1-
carbodithioic acid and its N-alkyl derivatives exhibits a sharp singlet
in the range of δ.13–4.86 ppm, which may be ascribed to SH proton. The
absence of the signal for the SH proton in the spectra corresponding
organoarsenic (III) complexes supports the deprotonation of SH group.
Broad signals observed in the range of δ 11.0–11.2 and δ
5.89–6.22 ppm may be assigned to NH/NH2 protons of amino
group in organoarsenic(III) complexes, if 2-aminocyclopentene – 1-
carbodithioicacid and its N-/S- alkyl derivatives (in ligands in the range
12.2 and6.22 ppm.) for-NH/NH protons. Appearance of both the signals
even in the spectra of complexes indicates that the amino group is not
deprotonated on complexation.
A slight shift has been observed in the position of NH/NH2 mode
in complexes in comparison to its position in ligands. This is due to
breakage of hydrogen bond on complexation.
A singlet observed in the range of δ.23–3.49 ppm may be ascribed
for methoxy protons in phenylarsenic(III) dimethoxide compounds of
S-alkyl derivatives of 2-aminocyclopentene 1- carbodithioicacid, which
favors the formation of addition compounds in phenylarsenic(III)
dimethoxide compounds of S- alkyl derivatives of 2- aminocyclopentene-
1-carbodithioicacid.
13C NMR
13C NMR spectra of corresponding ligands and complexes were recorded
in CDCl3 solution and the observed chemical shifts values are discussed
in the following sections.
The 13C NMR spectrum of phenylarsenic(III) complexes of 2-
aminocyclopentene – 1-carbodithioic acid exhibits a signal at 205.10
ppm, which may assigned to C(6)carbon; whereas in the spectrum of
the ligand, this signal was observed at 197.3 ppm.

2813

2
814

2815

2
816
R. Rathore et al.
A downward shift of 8 ppm in its position may be due to deshielding
of C6 carbon atom because of metallation of SH group and coordination
between arsenic and sulfur atom of C(S)S group. The signal for C(2)
carbon in same complex observed at 187.1 ppm and at170.1 ppm for
ligand. This signal show a downfield shift ∼17 ppm in its position as
compared to the ligand which may be due to decrease in electron density
between C(2) and C(6) as both the sulfur atom attached to C(6) carbon
coordinate to the metal atom there by decreasing the electron density.
1
3
In the
C NMR spectra of addition compounds of pheny-
larsenic(III) dimethoxide compounds of sulfur alkyl derivatives of 2-
aminocarbodithioic acid, the signal for C(6) carbon atom observed at
δ79.3–179.5 (in ligand at δ 201.1 ppm)ppm respectively. An upfield shift
has been observed in the position of C(6) carbon atom in comparison to
its position in the spectra of free ligands.
This favors the coordination between free sulfur atom of dithiocar-
boxylate group of ligand moiety and arsenic atom. The methoxy carbon
signals have been observed in the range of δ 43.4–49.7 ppm in both
the compounds; this favors the formation of addition complex of pheny-
larsenic(III) with sulfur alkyl derivatives of 2- aminocarbodithioic acid
and its N- alkyl derivatives from substituted compounds. Other signals
appear at their expected position shown in Table IV.
The corrected chemical shift values12 and Hammet Taft constant
1
0
3,14
R
have been found to be in the region of δ 7.8–8.8 ppm and δ 0.35–
0.37 ppm, respectively. These negative values indicate an electron re-
lease from arsenic atom towards phenyl ring through dπ -pπ conjugation
and poor donor capability of arsenic atom in these derivatives.
On the basis of strong absorption band for asym C(S)S and ab-
sence of SH signal in the IR spectra and the position of the NH2 in
1
phenyl or R-NH proton in H NMR in phenylarsenic(III) complexes of
TABLE IV 13C NMR Spectral Data of
2
-Aminocyclopentene-1-carbodithioic Acid and Its N-/S-Alkyl
Derivatives and Their Corresponding Phenyl Arsenic (III)
Derivatives
Ligand(a) and
corresponding
S. N. complexes(b) R
ꢀ
ꢀ
R
C(1)
C(2)
C(3)
C(4)
C(5)
C(6)
1
2
(a) H
b) H
(a) CH3
b) CH3
118.8
118.7
118.9
—
170.1
187.1
176.5
—
36.7
36.8
34.2
—
20.0
19.3
20.9
—
34.3
34.1
33.2
—
197.3
205.10
159.0
—
—
—
—
(
(
31.4

Organosarsenic(III) Derivatives with Aminocyclopentene
2817
2-aminocyclopentene 1- carbodithioic acid and its nitrogen alkyl deriva-
tives , it may be concluded that the NHR group of ligand does not take
part in the bonding and the chemical bonding takes place between ar-
senic and CS2 group of the ligand. The ligand behaves as bidentate
moiety. In view of bidentate nature of ligand and presence of lone pair
of electron following structure may be tentatively proposed for these
derivatives
−
1
Whereas the appearance of two strong bands at 940–970 cm for
νasym C(S)S in the IR spectra of phenylarsenic dimethoxide derivatives
of S-alkyl derivatives of 2-aminocyclopentene – 1- carbodithioicacid in-
dicates the monodentate behavior of ligand moiety in addition com-
pound and non involvement of amino group in bonding and favors the
coordination between the sulfur atom of dithiocarboxylate group of lig-
1
13
and moiety and arsenic atom and on the basis of IR ,NMR ( H & C)
spectral evidences following probable structure may be assigned.

2
818
R. Rathore et al.
EXPERIMENTAL
All reaction was carried in anhydrous conditions. The chemicals used
were reagent grade. Solvents used were dried by standard meth-
ods. The ligands 2-aminocyclopentene-1-carbodithioicacid and its N-
/
S-alkylderivatives and phenylarsenic (III) derivative have been pre-
1
4,15
pared by standard methods reported in literature.
These products
have been purified by dissolving in choloroform and then precipitat-
ing by adding access of petroleum ether. Separated product were de-
canted off and washed repeatedly with petroleum ether and the last
traces of volatile fraction were removed under reduced pressure. These
complexes are found to be soluble in common organic solvents, eg-
CHCl3CCl4 and CH2Cl2elements arsenic, sulfur and nitrogen were
analyzed through literature methods.1
6,17
IR absorption spectra were
−
1
recorded as a nujol mull on CSI pallets in the region 4000–400cm , and
000–200cm . The H and C NMR spectra were recorded in CDCl3
−1
1
13
4
and DMSO solution, respectively, on BRUCKER-270 MHz.Brucker
DPX-300 MHz and JEOL FX 90Q MHz using TMS as in internal ref-
erence. All the derivatives have been prepared by the same procedure.
The preparation method of a representative complexes and addition
complexes is described below and the results for the rest are summa-
rized in Table I.
Synthesis of Organic Derivatives of Organoarsenic(III)
Aminocyclopentene(I)-Carbodithioicacid and Its
N–Alkylderivatives
These derivatives have been prepared by the reaction of PhAsCl2, with
corresponding ligands in 1:2 molar ratio in presence of sodium methox-
ide in benzene solution under constant stirring and heating for 8 h.
Since all the N-alkylderivatives are prepared by similar methods for
the sake of brevity and convenience the detailed synthesis of only one
representative compounds is being discussed and the rest are summa-
rized in Table IV.
Synthesis of Phenyl Arsenic (III)-Derivatives
of Bis[2-Aminocyclopentene-1-carbodithiato-S,S]
To a benzene solution (15 ml) of sodium methoxide [prepared by treat-
ing sodium (0.16 gm, 6.95 mM) with small amount (15 ml) of methanol],
a benzene solution of phenyl arsenic(III) dichloride (0.81gm, 3.63 mM)
was added, and the solution was stirred for 2 h. Then 15 ml of benzene
solution of ligand 2-aminocyclopentene – 1- carbodithioicacid (1.16 g,

Organosarsenic(III) Derivatives with Aminocyclopentene
2819
7.28 mM) was added to it. The reaction mixture was stirred for 4 h
to ensure the completion of reaction. After the completion of reaction,
NaCl formed was filtered off, and the excess of the solvent was removed
from the filtrate under reduced pressure. The yellow colored solid com-
pound thus obtained was recrystallized from chloroform/n-hexane mix-
ture (91% yield). The compound was analyzed for the As, N and S found
As = 15.40, N = 5.13 and S = 27.90 %, calculated for C18H21S4N2As,
(
As = 15.90, N = 5.97 and S = 27.37 %).
Synthesis of Addition Compounds of Phenylarsenic(III)
Methoxide with S-Alkyl Esters of 2-Aminocyclopentene-
1-carbodithioicacid
These compounds have been synthesized by the reaction of PhAsCl2
with corresponding ligands in 1:1 molar ratio in presence of a base
NaOMe. Since both the compounds have been prepared by a similar
method, the synthesis of only one representative compounds is being
summarized in Table I.
Synthesis of [S-Methyl-2-aminocyclopentene –
1-carbodithioato-S] Phenyl Arsenic (III) Dimethoxide
Add (0.72 g, 3.23 mM ) of sodium in small amount of methanol (20
ml). Then add 20 ml of benzene solution of the ligand S-methyl – 2-
aminocyclopentene – 1-carbodithioicacid (1.12 g, 6.46 Mm) was added to
it and the reaction mixture was refluxed for 8 h to ensure the completion
of reaction. The precipitated sodium chloride was filtered off. The excess
of solvent was removed from the filtrate under reduced pressure. The
brown solid compound was recrystallized from chloroform/pet. Ether
(
40–60 OC) mixture (yield 93%) analysis found, As = 19.30, S = 17.11,
and N = 3.60%; calculated for C15H22S2O2NAs (As = 19.44, S = 17.51
and N = 3.75 %).
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