Monothiophosphorylation of diorganotin dichlorides. Synthesis and characterization

Article abstract of DOI:10.1081/SIM-120017778

Reactions of diorganotin dichlorides with ammonium dialkyl monothiophosphates in refluxing benzene in 1:2 molar ratio yield diorganotin bis(dialkyl monothiophosphate). These compounds are soluble in common organic solvents. Molecular weight determinations

Full text of DOI:10.1081/SIM-120017778

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Monothiophosphorylation of Diorganotin Dichlorides.
Synthesis and Characterization
Adnan A.S. El‐Khaldy a
a Department of Chemistry , Al‐Azhar University , P.O. Box 1277, Gaza, Palestine
Published online: 09 Dec 2011.
To cite this article: Adnan A.S. El‐Khaldy (2003) Monothiophosphorylation of Diorganotin Dichlorides. Synthesis and
Characterization, Synthesis and Reactivity in Inorganic and Metal-Organic Chemistry, 33:2, 183-194, DOI: 10.1081/
SIM-120017778
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SYNTHESIS AND REACTIVITY IN INORGANIC AND METAL-ORGANIC CHEMISTRY
Vol. 33, No. 2, pp. 183–194, 2003
Monothiophosphorylation of Diorganotin
Dichlorides. Synthesis and Characterization
*
Adnan A. S. El-Khaldy
Department of Chemistry, Al-Azhar University,
Gaza-Palestine
ABSTRACT
Reactions of diorganotin dichlorides with ammonium dialkyl mono-
thiophosphates in refluxing benzene in 1:2 molar ratio yield diorganotin
bis(dialkyl monothiophosphate). These compounds are soluble in
common organic solvents. Molecular weight determinations show that
these compounds are associated in solution and the degree of
association is concentration dependent. The new compounds have been
characterized by elemental analyses as well as spectroscopic (IR, 1H,
13C, 31P and 119Sn) studies. On the basis of these data, chelate structures
have been proposed.
*
Correspondence: Adnan A. S. El-Khaldy, Department of Chemistry, Al-Azhar
University, P.O. Box 1277, Gaza-Palestine; E-mail: AdnanKhaldy@hotmail.com.
183
DOI: 10.1081/SIM-120017778
0094-5714 (Print); 1532-2440 (Online)
www.dekker.com
Copyright D 2003 by Marcel Dekker, Inc.

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El-Khaldy
INTRODUCTION
The coordination chemistry of tin(IV) is still an area of interest for
investigation, and much work has been done in the chemistry of tin(IV) and
organotin(IV) dithiophosphate derivatives. However, comparatively less
attention has been paid to the corresponding monothiophosphate deriva-
tives.[1–13] In addition to its biological activity, monothiophosphate is
capable of a variety of bonding modes (either through sulfur or oxygen).
We report in the present paper the synthesis and characterization of some
diorganotin bis(dialkyl monothiophosphates).
RESULTS AND DISCUSSION
The reactions of ammonium salts of dialkyl monothiophosphates with
diorganotin chlorides in refluxing benzene in 1:2 molar ratio yield
diorganotin bis(dialkyl monothiophosphates).
R2SnCl2 þ 2NH4OðSÞPðOR0Þ2 À! R2Sn½OðSÞPðOR0Þ2ꢀ2 þ 2NH4Cl
R =Me and R’ =Et (1), Pr-i (2), Pr-n (3), Bu-n (4), Bu-i (5) and Ph (6);
R =Bu and R’ =Ph (7) and Bu-n (8); R =Ph and R’ =Bu-n (9) and Pr-i (10).
These reactions occur readily at room temperature but to ensure
completion, the reaction mixtures were refluxed for ꢁ 3 hours and the
formed ammonium chloride was removed by filtration. The resulting
compounds are colorless viscous liquids and are soluble in common organic
solvents (Table 1). Molecular weight determinations show that these
compounds are associated in chloroform and the degree of association is
concentration dependent. Thus, Me2Sn[O(S)P(OPr-i)2]2 is monomer in
2.1% (w/w) solution but becomes a dimer on increasing the concentration
to 18.3%.
IR Spectra
Characteristic bands in the IR spectra of the present diorganotin
bis(dialkyl monothiophosphates) have been assigned by comparison with
the spectra of triorganotin derivatives (Table 2). The bands present in the
regions 960–1070 cm À 1 and 710–790 cm À 1 are assigned to n((P)–O–C)
and n(P–O–(C)) stretching vibrations, respectively.[14] The most important
feature is the absence of any peak due to n(P= O) in the region 1150–
1250 cm À 1. All the spectra show a band of medium to strong intensity at

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Diorganotin bis(Dialkyl Monothiophosphates)
185

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El-Khaldy
Table 2. Some relevant IR spectral dataa (cm À 1) for diorganotin(IV) dialkyl mono-
thiophosphates.
S. no.
Compound
n[(P)–O–C]
n[P–O–(C)]
n[P S]
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)
(10)
Me2Sn[OSP(OEt)2]2
Me2Sn[OSP(OPr-i)2]2
Me2Sn[OSP(OPr-n)2]2
Me2Sn[OSP(OBu-n)2]2
Me2Sn[OSP(OBu-i)2]2
Me2Sn[OSP(OPh)2]2
Bu2Sn[OSP(OPh)2]2
Bu2Sn[OSP(OBu-n)2]2
Ph2Sn[OSP(OBu-n)2]2
Ph2Sn[OSP(OPr-i)2]2
960 s
980 s
970 s
770 s
760 s
750 s
780 s
790 s
715 s
710 s
790 s
780 s
790 s
590 m
615 m
595 m
590 m
580 m
670 m
690 m
590 m
680 m
620 m
1010 s
1010 s
1070 s
1070 s
1010 s
1010 s
980 s
as = sharp and m = medium.
ꢁ 600 cm À 1 (at ꢁ 685 cm À 1 in diphenyl monothiophosphate derivatives)
which we tentatively assign to n(P=S). The position of this band does not
shed any light on the bonding pattern of the monothiophosphate ligands.[13]
1H NMR Spectra
1
The H NMR spectra (Table 3) show the expected peak patterns and
2
chemical shifts. The noteworthy observation is that the J(1H–119Sn) values
for dimethlyltin bis(diisopropyl and diphenyl monothiophosphate) deriva-
tives are 80 and 78 Hz, respectively, and these coupling constant values
appear to be concentration independent. These values are higher than those
for penta-coordinated triorganotin monothiophosphate derivatives ( ꢁ 68),
thus supporting to the presence of hexa-coordinated tin in the diorganotin
derivatives.[13]
13C NMR Spectra
The 13C NMR spectral data for these compounds are given in
Table 4. The chemical shift values of diorganotin bis(dialkyl monothio-
phosphates) ( ꢁ 10% solution in CHCl3) are in the expected range. The
alkoxy carbons show 2- and 3-bond coupling with the phosphorus atoms. The
[1J(13C–119Sn] values for Me2Sn[O(S)P(OPr-i)2]2 and Me2Sn[O(S)P(OPh)2]2
are 572.40 and 566.6 Hz, respectively, and correspond to hexa-coordinated

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Diorganotin bis(Dialkyl Monothiophosphates)
189
tin atoms in the complexes.[15] These values are similar to those of dialkyl-
tin bis(dialkyl dithiophosphates).
The corresponding [1J(13C–119Sn] values for diphenyltin bis(diisopro-
pyl and dibutyl monothiophosphates) could also be determined (after 4200
scans) and are 942.5 and 900.8 Hz, respectively, which is significantly
higher than the reported values for triphenyltin carboxylates[16] ( ꢁ 650 Hz)
or diphenyltin chloride[17] (786.8 Hz). These data are thus consistent with a
hexa-coordinated state of tin in the diphenyl complexes also.
31P NMR Spectra
Proton decoupled 31P NMR spectra in CDCl3 (Table 3) show only one
peak for each compound in the region 42.5–50.9 ppm. These chemical shift
values are indicative of bidentate attachment of the thiophosphato moieties
to the tin atom.[18]
119Sn NMR Spectra
119Sn NMR chemical shifts for diorganotin bis(dialkyl monothiopho-
sphates) recorded in chloroform (Table 3) do not appear to change
significantly with a change in the concentration. A Me2Sn[O(S)P(OPr-i)2]2
solution of the concentration 2.2% (w/w) shows a signal at À 130.5 ppm.
This value is almost in the same range as that reported for R2Sn[S2P(OR’)2]2
( ꢁ À 160 ppm) and thus is consistent with hexa-coordinated tin atoms.[19]
It may be recalled that in the case of Me3SnO(S)P(OPr-i) which has a
penta-coordinated structure, the chemical shift is 59.9 ppm.
Interestingly, the 119Sn shifts in organotin monothiophosphates appear
to be affected by the nature of organic groups present in thiophosphate
moieties. Thus, the values for R2Sn[O(S)P(OPh)2]2 are in the range of À 85
ppm which are appreciably lower than the corresponding value for O,O-
diisopropyl dithiophosphate derivatives.
119Sn chemical shift values for corresponding diphenyltin (diisopropyl-
and dibutylmonothiophophates) were observed at À 302.00 and À 305.00
ppm. These values are consistent with the values for diphenyltin bis(dialkyl
and alkylene dithiophosphates),[19] which contain hexa-coordinated tin atom.
The C–Sn–C bond angles for dimethyltin bis(diisopropyl and diphenyl
dithiophosphates), calculated on the basis of [1J(13C–119Sn] values, are
138.6° and 128.3°, respectively.[15]
From the molecular weight, various spectroscopic data and yields,
valuable information regarding structural features of diorganotin bis(dialkyl

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Figure 1. Suggested monomeric structure of diorganotin bis(dialkyl monothiophos-
phate). R = Me and R’ = Et (1), Pr-i (2), Pr-n (3), Bu-n (4), Bu-i (5) and Ph (6); R = Bu
and R’ = Ph (7) and Bu-n (8); R = Ph and R’ = Bu-n (9) and Pr-i (10).
monothiophosphates) may be obtained and the conclusion are summar-
ized below:
1. Diorganotin bis(dialkyl monothiophosphates) in very dilute solu-
tions are monomeric. The 119Sn chemical shifts as well as
1H–119Sn coupling constants obtained for the same concentrations
confirm hexa-coordination of tin and, therefore, a trans-octahedral
structure for the monomeric species may be suggested as shown in
Figure 1.
2. In concentrated solutions, these derivatives are present as dimeric
species but the spectroscopic features, in general, do not change. The
dimer, therefore, may have the following structure in Figure 2,
containing both chelating and bridging thiophosphate moieties. The
presence of only one 31P NMR signal indicates a fast exchange bet-
ween the bridging and chelating groups and obviously low-
temperature NMR data would be required for these complexes.
Figure 2. Suggested dimeric structure of diorganotin bis(dialkyl monothiophos-
phate). R = Me and R’ = Et (1), Pr-i (2), Pr-n (3), Bu-n (4), Bu-i (5) and Ph (6); R = Bu
and R’ = Ph (7) and Bu-n (8); R = Ph and R’ = Bu-n (9) and Pr-i (10).

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Diorganotin bis(Dialkyl Monothiophosphates)
191
Figure 3. Suggested polymeric structure of diorganotin bis(dialkyl monothiophos-
phate). R = Me and R’ = Et (1), Pr-i (2), Pr-n (3), Bu-n (4), Bu-i (5) and Ph (6); R = Bu
and R’ = Ph (7) and Bu-n (8); R = Ph and R’ = Bu-n (9) and Pr-i (10).
3. Although molecular weights in solutions of higher than 18%
concentration could not be determined, it seems reasonable to
assume that the extent of oligomerisation should increase with
concentration and in the neat form, these compounds probably are
present as polymers of the following type in Figure 3. On the ba-
sis of the Mo¨assbauer data for a few diorganotin bis(monothio-
phosphates), Nasser and Zuckerman[17] have also suggested a sim-
ilar structure.
4. The trans-octahedral environment around tin in all of the above
species is considerably distorted as indicated by the calculated
C–Sn–C bond angles. It may not be out of place to mention
here that x-ray crystal structures of diphenyltin bis(dithiophos-
phate)[20,21] and dimethyltin bis(tetramethylethylene)[22] show dis-
torted trans-octahedral structures with 135° and 133.9° (C–Sn–C)
bond angles, respectively. Our calculated bond angles being in the
same range also support the above structure.
EXPERIMENTAL
IR spectra were recorded as Nujol mulls using a Perkin–Elmer 2000
FT IR spectrometer in the range 4000–200 cm À 1 and CsI cells. NMR
spectra were recorded on a Bruker AC 250 FT spectrometer NMR using
TMS as internal references for 1H and 13C. 31P and 119Sn spectra were
recorded using H3PO4 or Me4Sn as external references, respectively. Mole-
cular weights were determined using a Knaur vapour pressure osmometer.

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El-Khaldy
Stringent precautions were taken to exclude moisture. The ammonium salts
of monothiophosphoric acids were prepared by the literature methods.[23]
Sulfur was determined by Messenger’s method as barium sulfate and tin as
tin oxide (Table 1).
Reactions of Diorganotin Dichlorides with Diisopropyl
Monothiophosphate Salts in 1:2 Molar Ratio
A benzene (20 mL) solution of diorganotin dichloride (1.09 g, 4.9
mmol) was added to a suspension of ammonium dialkyl monothiopho-
sphates (2.13 g, 9.9 mmol) in the same solvent (20 mL). The mixture was
refluxed for ꢁ 3 hours. NH4Cl which precipitated during the reaction was
filtered the solvent was removed under reduced pressure and diorganotin
dialkyl monothiophsphates were obtained as colorless, viscous liquids.
Synthetic and analytical data are listed in Table 1.
ACKNOWLEDGMENTS
The author would like to thank the Department of Chemistry, Al
Azhar University of Gaza and Dr. Amar El-Kidra, Amsterdam University
for support.
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Received December 13, 2000
Accepted September 14, 2002
Referee I: D. A. Knight
Referee II: S. O. Grim