Synthesis and characterization of some new triorganophosphorus, -arsenic and -antimony(V) amido derivatives

Article abstract of DOI:10.1080/10426500307799

A number of triorganophosphorus, -arsenic, and -antimony(V) amido derivatives of the general formula R₂R′ML₂ [where R = C₆F₅, C₆H₅; R′ = C₆F₅, C₆H₄

Full text of DOI:10.1080/10426500307799

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Phosphorus, Sulfur, and Silicon and the Related
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Synthesis and Characterization of Some New
Triorganophosphorus, -Arsenic and -Antimony(V) Amido
Derivatives
Sanjeev K. Shukla a , Ashok Ranjan a & A. K. Saxena a
a Defence Materials and Stores , Research and Development Establishment , Kanpur, India
Published online: 27 Oct 2010.
To cite this article: Sanjeev K. Shukla , Ashok Ranjan & A. K. Saxena (2003) Synthesis and Characterization of Some New
Triorganophosphorus, -Arsenic and -Antimony(V) Amido Derivatives, Phosphorus, Sulfur, and Silicon and the Related Elements,
178:4, 785-795, DOI: 10.1080/10426500307799
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Phosphorus, Sulfur and Silicon, 2003, Vol. 178:785–795
C
Copyright 2003 Taylor & Francis
1042-6507/03 $12.00 + .00
DOI: 10.1080/10426500390198147
SYNTHESIS AND CHARACTERIZATION OF SOME
NEW TRIORGANOPHOSPHORUS, -ARSENIC
AND -ANTIMONY(V) AMIDO DERIVATIVES
Sanjeev K. Shukla, Ashok Ranjan, and A. K. Saxena
Defence Materials and Stores, Research and Development
Establishment, Kanpur, India
(Received August 2, 2002)
A
number of triorganophosphorus, -arsenic, and -antimony(V)
amido derivatives of the general formula R2R0ML2 [where R =
C6F5, C6H5; R0 = C6F5, C6H4CH3-p; M = P, As or Sb and L =
imidazole, benzimidazole, 2-methyl benzimidazole, indazole, and
1,2,3,4-tetrahydrocarbazole] have been synthesized by the metathetical
reaction of triorganophosphorus, -arsenic, and -antimony(V) halides
and the corresponding imidazoles in the presence of triethyl amine.
These compounds have been characterized by elemental analysis, IR
and NMR (1H and 19F) spectroscopy, conductance, and molecular
weight data. The Van’t Hoff factor “i” and molar conductance data of
the compounds revealed them to be monomeric and nonionic in nature.
On the basis of spectroscopic studies, a tentative trigonal bipyramidal
structure has been assigned for these amido derivatives.
Keywords: Imidazole; NMR spectroscopy; pentafluorophenyl; synthe-
sis; trigonal bipyramidal
In comparison to the well-documented hydrocarbon based organo-
arsenic and -antimony(III and V) amido derivatives,1–4 corresponding
perfluorophenyl derivatives are scarcely reported.5 As the electronic
character of aromatic ring is markedly changed by the replacement
One of the authors (SKS) is thankful to DRDO, New Delhi for the award of a Senior
Research Fellowship. We are thankful to the Director, DMSRDE for providing laboratory
facilities and permission to publish the work. Thanks also are due to Mr. Vijay Pal,
Mr. Basant Lal, and Ms. Mamta Sharma of DRDE, Gwalior for extending IR and NMR
facilities.
Address correspondence to A. K. Saxena, Defence Materials and Stores, Research and
Development Establishment, Joint Director, DMSRDE PO, G.T. Road, Kanpur 208013,
India.
785

786
S. K. Shukla et al.
of five nuclear hydrogen atoms by fluorine, the chemical and physical
properties of the compounds also are changed. Thus, most of the time,
very striking differences have been observed in phenyl and pentaflu-
orophenyl substituted compounds just as perfluoroalkyl groups alter
the chemistry of alkyl groups.6 Such intricacies always kindled in-
terest of researchers to study pentafluorophenyl derivatives of group
15 elements.
Thus, keeping in view our continued interest in the synthesis, reac-
tions, and spectroscopic studies of fluorophenyl group 15 derivatives7–10
and also to study the effect of pentafluorophenyl group on coordina-
tion behaviour of group 15 organometallic compounds,11–14 it is consid-
ered worthwhile to synthesize and characterize some new triaryl M(V)
amido derivatives (M = As and Sb) along with some hydrocarbon based
triorganophosphine(V) amido derivatives for the shake of spectral
comparison.
RESULTS AND DISCUSSION
A number of hitherto unreported triorganophosphorus, -arsenic, and
-antimony(V) amido derivatives were synthesized by metathetical re-
action using triorganophosphorus, -arsenic, and -antimony halides and
imidazoles in the presence of Et3N as shown below:

Synthesis of Triorganophosphorus, -Arsenic and -Antimony(V) Amido Derivatives 787
The reactions were carried out under inert atmosphere in benzene
offering high yields of the products in general. Physical and analyti-
cal details of the compounds are given in Table I. All the compounds
are sharp melting and soluble in common organic solvents and are sta-
ble to air and moisture. The melting points of compound (II) and (VI)
do not change even after stirring 1.5 h with water and methanol at
3
room temperature. The molar conductance values for 10 M solution
1
in methanol of these derivatives were found in range of 14–22
mol cm2, which showed the absence of ionic species in solution.15
1
From the molecular weight determination, it has been concluded that
the derivatives are monomeric in nature.
IR Spectra
The formation of imidazole derivatives was identified by the disappear-
1
ance of (NH) absorption band at 3404
6 cm present in the lig-
ands invariably. Further, the appearance of characteristic absorptions
for C6F5, C6H5, C6H4CH3-p group and imidazole ring in the respective
derivatives confirmed the formation of the derivatives.16,17
1
As the absorption bands of (C C) of C6F5 ring16 at 1645–1465 cm
,
ring stretching vibration (C C) of C6H5 ring17 at 1584–1446 cm 1, and
1
(C N) of imidazoles at 1640–1527 cm appear in close proximities,
hence could not be assigned separately in these derivatives. Similarly,
(CN) [at 1307–1274 cm 1], (CN) [at 1170–1068 cm 1] absorptions of
imidazoles17 and (C F) of C6F5 group (at 1385–1088 cm 1) also appear
very close, hence not assignable separately (Table II).
In pentafluorophenylarsenic and -antimony derivatives [compounds
(I)–(IX)] characteristic aromatic stretching vibrations (C H) and
1
bending vibrations out of plane (C H) appeared at 3087–3010 cm
and 767–713 cm respectively.
1

788

789

790
S. K. Shukla et al.
In diphenyl(p-tolyl)phosphine derivatives [compounds (X)–(XIII)]
characteristic aromatic and aliphatic stretching vibrations (CH) ap-
1
peared at 3089–2844 cm and bending vibrations (C H) appeared17
at 1417–705 cm 1. In these derivatives the imidazole ring showed the
1
stretching and bending vibrations (CN) and (CN) at 1312-1245 cm
1
and 1185–1070 cm respectively.17
1H NMR Spectra
The signals due to N H protons invariably disappeared in all the
phosphorus, arsenic, and antimony imidazole derivatives, which may
be attributed to the formation of the derivatives. In diphenyl(p-
tolyl)phosphine derivatives [compound (X)–(XIII)] the aromatic protons
of C6H5, C6H4CH3-pand aromatic ring of imidazole ligands appeared in
close proximities as multiplet in the range 7.14–7.31 ppm thus could
not be assigned separately whereas the CH3 protons of p-tolyl group
appeared at
In the triarylarsenic and -antimony imidazole derivatives [compound
(I) and (V)] the C2 and C4,5 protons of the ligands appeared at 7.85
ppm (s, 2H) and 7.33 ppm (s, 4H) respectively.
2.35 ppm (Table III).
Benzimidazole derivatives of triorganoarsenic and -antimony(V)
[compounds (II) and (VI)] showed the protons of C2, C5,6, and C4,7 at
8.13 (s, 2H), 7.68 (q, 4H), and 7.32 ppm (q, 4H) respectively.
In the compound (III) and (VII) the C5,6 and C4,7 protons of 2-
methyl benzimidazole ligand appeared at
ppm (q, 4H) respectively. The C4,7 protons in the ligand appeared
at 7.15 ppm as hexet due to coupling of NH and C5,6 protons
7.49 (q, 4H) and 7.19
which in the derivatives appeared as a quartet at 7.19 ppm due to
loss of -NH proton. The CH3 proton due to ligand in these deriva-
tives appeared at
2.6 ppm (s, 6H). The single peak of CH3 fur-
ther showed that ligands are present in one plane. In the compound
(XII), CH3 protons of the p-tolyl group and ligand appeared at 2.32
(s, 3H) and 2.60 ppm (s, 6H), respectively, which further confirmed
that the p-tolyl group and the ligand are present separately in one
plane.
Indazole derivatives (IV) and (VIII) showed the C3, C4, C5, C6, C7
protons in usual manner at
8.62 (s, 2H), 7.45 (d, 2H), 7.13 (t, 2H),
7.35 (t, 2H), and 7.73 ppm (d, 2H) respectively.
Compound (IX) showed the proton signals of 1,2,3,4-
tetrahydrocarbazole in usual manner at 7.6 (C2, t, 2H), 7.4 (C4,
t, 2H), 7.16 (C3,5, Q, 4H), 2.75 (C6,9, Q, 4H), 1.96 ppm (C7,8, m, 4H).

791

792
S. K. Shukla et al.
19F NMR Spectra
Pentafluorophenylarsenic derivatives [compound (I)–(IV)] showed F2,6
F4 and F3,5 signals at 129, 143, and 156 ppm, respectively and
pentafluorophenyl antimony derivatives [compound (V)–(IX)] showed
F2,6, F4, and F3,5 signals at 135, 143, and 160 ppm respectively.
,
The F4 signals were easily identified due to half intensity compared to
F2,6 and F3,5. The F4 signals appeared as a triplet due to F3,5 coupling.
The F2,6 and F3,5 signals appeared as doublet and triplet respectively.
The F3,5 chemical shifts were observed at higher field compared to the
F2,6 and F4 chemical shifts, indicating that the donation of electron from
o- and p-positions takes place toward carbon attached to antimony atom
and this observation is in accordance with the previous studies that the
C1 carbon of perfluorinated benzene ring feels high electron density due
to the diminished inductive effect of the fluorine atom and donation of
electron density from the unshared p electron of fluorine to the system
of the ring ( p- interaction).18,19
In view of the spectroscopic data of these compounds, the metal
(P, As, and Sb) in such cases is assumed to be in pentacoordinated
state and the structure of the compounds (I)–(XIII) may be tentatively
assigned as trigonal bipyramidal (Figure 1) in which aryl rings are in
one plane and thus imidazole ligands attained apical position.
FIGURE 1 Configuration of triorganophosphorus, -arsenic, and -antimony(V)
amido derivatives.

Synthesis of Triorganophosphorus, -Arsenic and -Antimony(V) Amido Derivatives 793
EXPERIMENTAL
All solvents (AR Grade) were purified, dried, and distilled before use
by the standard methods.20 The reactants, viz. imidazole, benzimida-
zole, 2-methyl benzimidazole, indazole, and 1,2,3,4-tetrahydrocarba-
zole (all Lancaster) were used as such. Triethylamine (E. Merck, AR
Grade) was used after drying over potassium hydroxide. Tris(penta-
fluorophenyl)arsenic and -antimony(V) dichlorides were prepared by
the reported methods.21,22
IR spectra were recorded on a Pye Unicam SP3-300 spectropho-
tometer over the spectral range 4000–200 cm 1in the solid state us-
ing KBr/CsI Pellets.1H and 19F NMR spectra were recorded on Jeol
JNM-400 NMR spectrometer using TMS and CF3COOH as references
respectively. Molecular weights were determined cryoscopically in ni-
trobenzene using a Beckman thermometer of 0.01 accuracy. The mo-
3
lar conductance of 10 M solution of the compounds was determined
at 25 C with a Khera DC610 digital conductivity meter in methanol.
Some representative synthesis procedures follow.
Synthesis of Diphenyl(p-tolyl)phosphine Dichloride
[(C6H5)2(C6H4CH3-p)PCl2]
Dry chlorine gas (generated by reaction of KMnO4 and conc. HCl) was
bubbled in a solution of Ph2(p-Tol)P (13.82 g, 0.05 mmol) in petroleum-
ether (60–80 C) at room temperature under moisture free and nitrogen
atmosphere with constant stirring. White precipitate was started to
settle down, after 15 min bubbling of Cl2 gas was stopped and the reac-
tion mixture was further stirred for 30 min at room temperature, and
then the solvent was decanted. The residue was washed three times
with petroleum-ether (60–80 C) to remove unreacted Ph2(p-Tol)P. The
residue was characterized as Ph2(p-Tol)PCl2, yield 12.50 g (72%), m.p.
93 C, (found: C, 65.79; H, 5.00%; calcd. for C19H17Cl2P; C, 65.72; H,
4.93%).
Reaction of Tris(pentafluorophenyl)arsenic Dichloride
[(C6F5)3AsCl2] with Imidazole
Tris(pentafluorophenyl)arsenic dichloride (1.294 g, 2 mmol), imidazole
(0.272 g, 4 mmol) and Et3N (1 ml) were stirred together in 75 ml of
benzene at room temperature for 6 h, followed by 3 h of refluxing
to ensure the completion of the reaction. Et3N HCl [m.p. 261 C(d)]
formed was filtered off and the filtrate on concentration and addition of
petroleum-ether (40–60 C) afforded the product C24H6F15N4As (I),
yield 1.05 g (74%), m.p. 122 C.

794
S. K. Shukla et al.
Similarly, other reactions of (C6F5)3AsCl2 with benzimidazole,
2-methyl benzimidazole, and indazole were carried out.
Reaction of Tris(pentafluorophenyl)antimony Dichloride
[(C6F5)3SbCl2] with Benzimidazole
Tris(pentafluorophenyl)antimony dichloride (1.388 g, 2 mmol), benz-
imidazole (0.472 g, 4 mmol) and Et3N (1 ml) were stirred together in
75 ml of benzene at room temperature for 6 h, followed by 1 h of reflux-
ing to ensure the completion of the reaction. Et3N HCl [m.p. 261 C(d)]
formed was filtered off and the filtrate on concentration and addition of
petroleum-ether (40–60 C) afforded the product C32H10F15N4Sb (VI),
yield 1.457 g (85%), m.p. 109–111 C.
In a similar way, other reactions of (C6F5)3SbCl2 with imidazole,
2-methyl benzimidazole, indazole, and 1,2,3,4-tetrahydrocarbazole
were carried out.
Reaction of Diphenyl(p-tolyl)phosphine Dichloride
[(C6H5)2(C6H4CH3-p)PCl2] with 2-Methylbenzimidazole
Diphenyl(p-tolyl)phosphine dichloride (1.389 g, 4 mmol), 2-methyl ben-
zimidazole (1.057 g, 8 mmol) and Et3N (1 ml) were stirred together in
75 ml of benzene at room temperature for 6 h, followed by 3 h of reflux-
ing to ensure the completion of the reaction. Et3N HCl [m.p. 261 C(d)]
formed was filtered off and the filtrate on concentration and addition of
petroleum-ether (40–60 C) afforded the product C35H31N4P (XII), yield
1.71 g (79%), m.p. 104 C.
Similarly, other reactions of Ph2(p-Tol)PCl2with imidazole, benzim-
idazole, and indazole were carried out. Some products were viscous,
which could be crystallized only after scratching with a glass rod.
Reaction of (II) and (IV) with Water and Methanol
The diamides (II) and (IV) were stirred with excess of water and
methanol respectively for 1.5 h at room temperature and subsequently
refluxed for 1 h. After removal of the solvent the residue showed no
change in melting point or IR spectra.
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