Studies on the interaction of phosphine selenides and their structural analogues wth dihalogens and sulfuryl chloride

Article abstract of DOI:10.1039/b207019g

The phosphine selenides, tris(dimethylamino)phosphine selenide, esters of selenophosphoric acid, and esters of selenophosphonic acid react with dihalogens and sulfuryl chloride to form halogenoselenophosphonium salts (≡ 3P-SeX)⁺X^-. T

Full text of DOI:10.1039/b207019g

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Studies on the interaction of phosphine selenides and their
structural analogues wth dihalogens and sulfuryl chloride†
Ewa Krawczyk, Aleksandra Skowron´ska* and Jan Michalski
Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences,
Sienkiewicza 112, 90–363 Łódz´, Poland. E-mail: askow@bilbo.cbmm.lodz.pl
Received 17th July 2002, Accepted 24th September 2002
First published as an Advance Article on the web 30th October 2002
The phosphine selenides, tris(dimethylamino)phosphine selenide, esters of selenophosphoric acid, and esters of
selenophosphonic acid react with dihalogens and sulfuryl chloride to form halogenoselenophosphonium salts
ϩ
Ϫ
ϩ
Ϫ
᎐
᎐
(᎐P–SeX) X . The latter undergo deselenization via ligand exchange to form phosphonium salts (᎐P–X) X and
᎐
᎐
elemental selenium. The stability of these salts depends on the substituents at the phosphorus atom and the type of
counter ion. It is likely that the phosphonium salts are in equilibrium with the corresponding phosphoranes, and this
is demonstrated for esters containing an o-phenylene ligand. The structures of phosphonium salts, phosphoranes and
other phosphorus compounds are supported by 31P NMR spectroscopy data and electrical conductivity. Additional
evidence comes from addition reactions of halogenoselenophosphonium salts to cyclohexene.
and Raman spectra they assigned to Ar3PSeBr2 a non-ionic
Introduction
structure with a linear arrangement of the Br–Se–Br group. We
Interest in phosphorus–selenium compounds is growing.
repeated this procedure and the yellow solid obtained was
Derivatives of monoselenophosphoric acid P(Se)(OH)3 are of
examined by 31P NMR spectroscopy in dichloromethane solu-
special interest. Monoselenophosphate has been shown to be
tion. At room temperature a single signal δP = 50.7 ppm was
the key intermediate in selenoprotein synthesis.1 Monoseleno-
observed with an absence of satellite peaks derived from 77Se.
phosphate has been chemically synthesized and shown to be
Glidewell and Leslie have also examined this adduct in CDCl3
identical with the biological selenium donor.2 Organic pyro-
solution and observed only one signal by 31P NMR spectro-
phosphates play a fundamental role in biology: their selenium
scopy.5 In our opinion the solid Ph3PSeBr2 adduct under-
analogues may be of interest for biological studies. The first
goes deselenization in CH2Cl2 or CDCl3 solution, probably via
rational synthesis of tetraalkyl selenopyrophosphates contain-
the phosphonium intermediate 1, to give the adduct 2. We
observed the signal δP = 50.6 ppm for the adduct of triphenyl-
ing a selenium atom bridging two phosphoryl centers has been
previously described by us.3 These compounds are very reactive
phosphine with elemental bromine prepared independently
towards nucleophiles and can be considered as potent phos-
from triphenylphosphine and elemental bromine [eqn. (1)].
phorylation reagents. sym-Selenopyrophosphates when heated
to above 60 ЊC isomerize into asym-selenopyrophosphates,
which are identical with compounds previously prepared.3d
(1)
sym-Selenopyrophosphates have been prepared by interaction
of selenophosphates (RO) P᎐Se with dihalogens or sulfuryl
᎐
3
chloride.3c Also interaction of tertiary phosphine selenides
This deselenization course involves ligand exchange and
decomposition of the transient anion SeBrϪ Sex ϩ BrϪ. We
R P᎐Se with dihalogens has attracted the attention of several
᎐
3
did not observe the hypothetical structure 1 at Ϫ90 ЊC by 31P
NMR spectroscopy. In contrast the reaction of triphenyl-
phosphine selenide 3 and tri-n-butylphosphine selenide 6 with
dichlorine proceeds at Ϫ90 ЊC via formation of the ionic inter-
mediates 4 and 7. These phosphonium salts decompose into the
corresponding chlorophosphonium chlorides 5 and 8, which
are observed at Ϫ90 ЊC [eqn. (2)].
authors.4 The most meticulous studies have concerned the
interaction between tertiary phosphine selenide and elemental
iodine.4a,d,f,h However, there is very little information about the
behavior and structure of compounds obtained in solution and
some results are confusing.
In this paper we describe our studies on the interaction of
compounds R1R2R3P᎐Se (R1, R2, R3 = alkyl, aryl, dialkyl-
᎐
amino, alkoxy, aryloxy) with dichlorine, dibromine and sulfuryl
chloride providing a rationale for earlier observations. The
most significant part of this paper deals with esters of seleno-
phosphoric acid and similar structures. Finally we describe the
(2)
ϩ
Ϫ
᎐
behavior of [᎐PSe–X] X structures towards olefins.
᎐
Results and discussion
The phosphonium salt structure is in agreement with 31P
NMR spectroscopic data on chemical shift and JPSe coupling
Reaction of triphenyl and tri-n-butyl phosphine selenides with
dihalogens
1
constants indicating the presence of a selenium atom linked by
a single bond to a phosphorus center.6
Williams and Wynne have examined the adduct of elemental
bromine with triphenylphosphine selenide.4b On the basis of IR
Interestingly we observed a similar phosphonium struc-
ture 4a when triphenylphosphine was allowed to react with
selenium chloride Se2Cl2 at Ϫ90 ЊC in dichloromethane solution
[eqn. (3)].
† This paper is dedicated to Professor Reinhard Schmutzler on the
occasion of his retirement.
DOI: 10.1039/b207019g
J. Chem. Soc., Dalton Trans., 2002, 4471–4478
This journal is © The Royal Society of Chemistry 2002
4471

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(3)
Reaction of tris(dimethylamino)phosphine selenide with
elemental chlorine and bromine
This interaction is represented by eqn. (4). Halogenoseleno-
phosphonium salts 9 and 10 exhibit greater stability than the
analogous compounds derived from phosphine selenides: 4 and
7. They undergo transformation into phosphonium salts 11 and
12 after being kept for 3 days at room temperature. Chemical
shifts δ31P and coupling constants 1JPSe correlate well with those
known for the corresponding alkylselenophosphonium salts
137 and 14.8
Scheme 1
formation of diethoxyoxophosphoraneselenyl chloride 20. This
unstable compound with chemical shift δP = 23.5 ppm and
coupling constant JPSe = 644 Hz is formed when diethyl-
1
phosphoroselenoic acid 19 is allowed to react with elemental
chlorine at a temperature below Ϫ20 ЊC in ethyl chloride
solution [eqn. (7)].
(4)
(7)
A surprising difference was observed when O,O,O-triethyl-
selenophosphate was allowed to react with sulfuryl chloride
SO2Cl2 at 0 ЊC. The salt 16a was formed and is stable for several
hours in solvents like dichloromethane or benzene at room
temperature [eqn. (8)].
In the solid state a non-ionic structure was established, on the
basis of X-ray analysis, for the (Me2N)3PSeBr2 adduct.4e
Reaction of O,O,O-triethylselenophosphate with dichlorine and
sulfuryl chloride
(8)
These studies have been undertaken with the aim of finding
a route to the synthesis of oxophosphoraneselenyl halides
>P(O)SeX. The reaction of O,O,O-triethylselenophosphate
with dichlorine differs from the analogous reaction with tri-
ethylthionophosphate, which was studied earlier in this
laboratory.9 The former reaction when performed at room
temperature gives diethylphosphorochloridate along with
precipitation of elemental selenium [eqn. (5)].
Salt 16a undergoes slow decomposition into the diethyl-
phosphorochloridate 18 by steps analogous to those indicated
in Scheme 1. In earlier studies in this laboratory the salt 16a was
misidentified as the selenyl chloride 20.10 The easy accessibility
of the salt 16a and its relative stability have led to its successful
use in organic synthesis.11
(5)
Reaction of O,O,O-trineopentylselenophosphate with sulfuryl
chloride
Reaction of dichlorine with thionophosphate leads to
diethoxyoxophosphoranesulfenyl chloride [eqn. (6)].
Another object of our studies was O,O,O-trineopentylseleno-
phosphate 21. We hoped to obtain crystalline compounds
useful for X-ray studies, but this was not achieved. O,O,O-
(6)
Trineopentylselenophosphate (ButCH O) P᎐Se 21 reacts with
᎐
2
3
sulfuryl chloride to afford the phosphonium salt 22a [eqn. (9)].
To rationalize this difference variable-temperature 31P NMR
studies were undertaken. In the range from Ϫ100 ЊC to Ϫ80 ЊC
two peaks were observed corresponding to the starting triethyl-
(9)
1
selenophosphate 15 (δP = 70 ppm, JPSe = 905 Hz) and the salt
like compound 16 (δP = 38 ppm, 1JPSe = 816 Hz). At Ϫ70 ЊC the
starting material 15 disappeared and a new peak corresponding
to the triethoxychlorophosphonium salt (EtO)3PϩClClϪ 17a
was observed. This salt was identical with that obtained earlier
when triethylphosphite was allowed to react with elemental
chlorine at Ϫ100 ЊC in C2H5Cl solution.9 Subsequently at
Ϫ60 ЊC a peak derived from diethylphosphorochloridate 18
(δP = 3 ppm) appeared . At Ϫ30 ЊC the salt 17a disappeared
and this is in agreement with our earlier observations.9 Above
Ϫ30 ЊC the salt 16 is gradually transformed into diethyl-
phosphorochloridate 18 and other minor unidentified products.
The interaction of O,O,O-triethylselenophosphate 15 with
elemental chlorine is represented in Scheme 1.
Compound 22a is more stable than salt 16a containing the
ethoxy ligand. As expected a similar reaction with ele-
mental chlorine led to compound 22 [(ButCHO)3Pϩ–SeClClϪ]
1
(δP = 35 ppm, JPSe = 838 Hz) which decomposed even at
Ϫ20 ЊC. We did not observe formation of the corresponding
selenyl chloride (ButCH2O)2P(O)SeCl 23. However the unstable
23 was prepared from O,O-dineopentyl-O-trimethylsilylseleno-
phosphate.12
Additional experiments involving ligand exchange at the
phosphorus center and independent synthesis of these systems
supported the phosphonium structure of the products obtained
from the reaction of O,O,O-trialkylselenophosphates with
dihalogens.
The transformation of salt 16 into 18 probably proceeds by
ligand exchange (path b). There is no spectral indication for the
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Formation of the phosphonium salt 22b was observed at
Ϫ100 ЊC in ethyl chloride solution when trineopentyl phosphite
24 was allowed to react with selenium monochloride Se2Cl2.
In all reactions described above concerning interaction of
elemental halogens and sulfuryl chloride with (RO) P᎐Se com-
᎐
3
pounds we were not able to observe selenyl halides (RO)2P(O)-
SeX which could be formed by the dealkylation of intermediate
salts 16, 16a, 22a and 27, 28.
In addition to the signal corresponding to the salt 22b (δP
=
35.1 ppm, 1JPSe = 840 Hz) another signal was noted belonging to
O,O,O-trineopentylselenophosphate 21. The latter compound
is presumably formed via pathway c (Scheme 2).
The reaction of O,O-diethyl-P-tert-butylselenophosphonate with
elemental chlorine and sulfuryl chloride
To explain the results presented above, one option is to assume
that (RO)2P(O)SeX structures are exceptionally unstable and
undergo rapid deselenization leading to the corresponding
halogenoanhydrides (RO)2P(O)X. Another option is that
ligand exchange at the phosphonium centers is faster than
dealkylation. Ligand exchange is facilitated by higher electro-
philicity at the phosphonium center compared with the corre-
sponding sulfur structures due to lower participation of dπ–pπ
coupling in P–Se bonding and the presence of a better leaving
group –SeX in comparison with –SX. We anticipated that steric
hindrance at the phosphorus center would suppress exchange
of ligands and not interfere with dealkylation. For this reason
O,O-diethyl-P-tert-butylselenophosphonate 33 was employed
as a model compound. Salts 34 and 34a (see Scheme 4) are
Scheme 2
At Ϫ30 ЊC the product of oxidative addition of Se2Cl2 to
trineopentylphosphite, 22b was decomposed into the phos-
phonium compound 25. The spectral properties of both salts
are in good agreement with analogous phosphonium structures
formed when elemental chlorine or sulfuryl chloride are reacted
with O,O,O-trialkylselenophosphates. Path b in Scheme 2 is
likely to involve deselenization of the SeClϪ anion and ligand
exchange.
The reaction of O,O,O-trialkylselenophosphates with elemental
bromine
Interaction of elemental bromine with O,O,O-trialkylseleno-
phosphates (RO) P᎐Se was investigated in two cases (R = Et,
᎐
3
ButCH2). The corresponding bromoselenophosphonium salts
27, 28 are formed at 20 ЊC in dichloromethane solution.
The reactions described in Scheme 3 proceed at temperature
as low as Ϫ85 ЊC to give bromoselenophosphonium salts 27 and
28. However, we were not able to observe the intermediates 29
and 30.
Scheme 4
stable up 0 ЊC and 34a transforms at room temperature into
bis(phosphinoyl) diselenide among other products. The disele-
nide 35 is probably formed via the reaction of the substrate 33
with the salt 34a or the (EtO)ButP(O)SeCl 36.
The reaction of O,O-dimethyl-P-phenylselenophosphonate and
O-methyl-P,P-diphenylselenophosphinate with elemental
halogens
The interaction of compounds O,O-dimethyl-P-phenylseleno-
phosphonate 37 and O-methyl-P, P-diphenylselenophosphinate
38 with elemental chlorine, bromine and sulfuryl chloride led
at Ϫ100 ЊC to the halogenoselenophosphonium salts 39, 40,
41 and 42 which decompose at 0 ЊC to the corresponding
halogenoanhydrides 43, 44 and 45, 46. We did not observe
Scheme 3
The crystalline salt 28 precipitates from dichloromethane
solution. Its elemental analysis was in agreement with the
proposed structure. Unfortunately under X-ray irradiation 28
underwent decomposition with the precipitation of elemental
selenium.
The bromide anion was readily exchanged by the reaction of
salt 27 with silver trifluoromethanesulfonate. Salt 27a is stable
at temperatures below Ϫ20 ЊC. Its spectral properties are in
agreement with the proposed structure 27a [eqn. (10)].
ϩ
Ϫ
᎐
halogenophosphonium salts (᎐PX) X which are formed by
᎐
ligand exchange. These reactions proceed in a similar manner to
᎐
those of other types of ᎐P᎐Se compounds. The spectral data for
᎐ ᎐
salts 39, 40 and 41, 42 are given in Table 1.
The data shown are in agreement with those observed by
others 8 for R3Pϩ–SeMeSbCl6Ϫ salts.
The reaction of O,O,O-triphenylselenophosphate with elemental
halogens
(10)
Halogenoselenophosphonium salts 48, 48a, 49 are formed
when O,O,O-triphenylselenophosphate 47 is allowed to react
J. Chem. Soc., Dalton Trans., 2002, 4471–4478
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Table 1 31P NMR data collection for compounds 37–46
᎐PϩSeCl XϪ
>P(O)X
᎐
᎐P᎐Se
᎐ ᎐
᎐
(MeO)2PhP᎐Se (37)
(MeO)2PhPϩSeClXϪ (39)
XϪ = SO2ClϪ, ClϪ
δP = 72.7
(MeO)PhP(O)Cl (43)
᎐
δP = 98.5
δP = 30.0
—
1JPSe = 881 Hz
1JPSe = 701 Hz
(MeO)2PhPϩSeBrBrϪ (40)
δP = 69
(MeO)PhP(O)Br (44)
δP = 11.3
1JPSe = 696 Hz
—
(MeO)Ph2P᎐Se (38)
(MeO)Ph2PϩSeClXϪ (41)
XϪ = SO2ClϪ, ClϪ
δP = 85
Ph2P(O)Cl (45)
᎐
δP = 88
δP = 45.2
—
1JPSe = 788 Hz
1JPSe = 605 Hz
(MeO)Ph2PϩSeBrBrϪ (42)
δP = 82.4
Ph2P(O)Br (46)
δP = 71.2
—
1JPSe = 592 Hz
with elemental chlorine, bromine and sulfuryl chloride. They
are visibly less stable than the salts derived from O,O,O-
trialkylselenophosphates and are predisposed to easy ligand
exchange due to a higher positive charge at the phosphonium
center caused by electronegative ligands [eqn. (11)].
this reaction by 31P NMR showed formation of the penta-
coordinate structure 54 containing an SeCl ligand. The
phosphorane 54 was gradually transformed into the dichloro-
phosphorane 55 and finally, after warming to 0 ЊC, into the
chloroanhydride 56 (Scheme 6).
(11)
The reaction of halogenoselenophosphonium salts with
cyclohexene
Additional evidence for the structure of salts 16, 16a and 27 is
their reaction with cyclohexene. Two sets of products are
formed indicating the ambident electrophilic character of com-
pounds 16, 16a and 27. This behavior is presented in Scheme 5,
disregarding hypothetical unstable intermediates. The addition
leads to compounds of trans configuration.
Scheme 6
Transformation of the phosphorane 54 (containing a
chloroseleno ligand) into the dichlorophosphorane 55 probably
proceeds via corresponding phosphonium salts. A similar
pentacoordinate structure was obtained in the reaction of ethyl-
O-phenylene phosphite 57 and phenylselenyl chloride PhSeCl
(Scheme 7).
Scheme 7
Scheme 5
It is well known that the ligand derived from 1,2-dihydroxy-
benzene contributes towards the stability of phosphorane
pentacoordinate structures. It is also well established that they
are in equilibrium with their corresponding tetracoordinate
phosphorus salt structures, which are involved in ligand
exchange.13
Presumably fast equilibrium with the corresponding penta-
coordinate structure takes place in all reactions leading to the
halogenoselenophosphonium structures described in this paper.
However their concentration is too low to be detected by 31P
NMR spectroscopy.
The total yield of products formed by pathways a and b is
high. Low temperatures favor path a. These and similar reac-
tions of selenium containing ambident electrophiles are the
subject of our current studies.
The reaction of O,O-phenylene-O-ethylselenophosphate with
sulfuryl chloride
A significant observation was made when O,O-phenylene-O-
ethylselenophosphate 53 was allowed to react with sulfuryl
chloride at Ϫ100 ЊC in ethyl chloride solution. Monitoring of
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J. Chem. Soc., Dalton Trans., 2002, 4471–4478

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1
Reaction of O,O-dialkyl-O-trimethylsilylselenophosphate with
elemental chlorine and sulfuryl chloride
Both JPSe coupling constants observed exceeded the
values reported for >P(O)–SeR compounds. The high value
1
of JPSe has also been noted by other authors for the salts
This is the only rational approach towards synthesis of com-
pounds (RO)2P(O)SeCl 59 which are formed at Ϫ78 ЊC almost
quantitatively. Because of their high instability they must be
used in situ. A good illustration of this situation is the synthesis
of sym-tetraalkyl selenopyrophosphates. The selenyl chloride
59 formed at Ϫ78 ЊC reacts very rapidly with dialkyl trimethyl-
silylphosphite 60 to give the sym-selenopyrophosphates 61 in
very high yield3c (Scheme 8).
(EtO)2Pϩ(OSiMe3)SeRXϪ.15
It is also known that 1JPSe rises when electronegative substitu-
ents are attached to the phosphorus center.6,16,17 In our case the
1
difference in JPSe can be seen when (RO)2P(O)SeCl (R = Et,
1JPSe = 644 Hz; R = ButCH2,
J
= 514 Hz) are compared with
12 1
PSe
O,O-diethyl-Se-ethylphosphate (1JPSe = 468).6
Electrical conductivity of halogenoselenophosphonium salts
Measurements of conductivity provide more strong evidence
for the ionic character of halogenoselenophosphonium salts
described in this study.
Two solvents of different polarity were used: dichloro-
methane (ε = 9.08) and 1-nitropropane (ε = 23.2). Conductivity
t
calculated according to the equation Λot = 1/c × p × Go for the
concentration 10Ϫ1 mol is presented in Table 2.
These data indicate that we are dealing with ion pairs whose
degree of separation depends on the polarity of the solvent.
Our observations of conductivity are analogous to those
described for alkyltriphenoxyphosphonium salts described by
Hudson and co-workers.18
Conclusion
Scheme 8
We have examined the interaction of R1R2R3P᎐Se compounds
᎐
In the synthesis of selenopyrophosphate 61 however it is
more convenient to use a relatively stable phosphonium salt
e.g. 16a, which reacts at room temperature to give the desired
compound (Scheme 9).
with dihalogens and sulfuryl chloride in solution. We have
demonstrated that, in contrast to the structures observed in
the solid state, halogenoselenophosphonium salts [R1R2R3-
P–SeX]ϩXϪ (C) are formed. They undergo deselenization via
ligand exchange to form phosphonium salts [R1R2R3P–X]ϩXϪ
(D) and elemental selenium. Salts (C) derived from O,O,O-
trialkylselenophosphate are stable enough to be used as
convenient electrophilic selenophosphorylating reagents in
synthetic procedures.
In the case of reaction between O,O-phenylene-O-ethyl-
selenophosphates and sulfuryl chloride we observed the
formation of pentacoordinate species containing SeCl and Cl
ligands which were transformed into dichlorophosphorane.
It seems most likely that the phosphonium salts are in
dynamic equilibria with the corresponding phosphoranes. The
equilibria favour the phosphonium form except when phos-
phorus bears a ligand, which stabilizes PV species. But in
every case reactions of selenophosphates with dihalogens and
sulfuryl chloride proceed with formation of phosphonium
salts.
Scheme 9
Coupling constants 1JPSe in halogenoselenophosphonium salts
In all halogenoselenophosphonium salts described in this paper
1JPSe values were up to 800 Hz and therefore close to those
1
Experimental
᎐
assigned earlier for seleno compounds ᎐P᎐Se ( J = 745–
᎐ ᎐
PSe
1100 Hz).6 It is known that the presence of positive charge
Glassware was flame-dried and cooled under a stream of
nitrogen and all reactions were performed under a dry argon
atmosphere. Solvents were dried by conventional methods
and distilled under nitrogen. Triphenylphosphine (Lab BDH
Reagent), phenylselenenyl chloride (Aldrich) and dichloro-
diselenide (Alfa Product) were used as received. 1H, 13C
NMR spectra were run on a Bruker AC-200 at 200.1 (1H),
50.32 (13C) using internal SiMe4 (1H, 13C). 31P NMR spectra
were recorded on a FT JEOL FX-60H at 24.3 MHz and on a
Bruker AC-200 at 81.02 MHz. Positive chemical shifts were
reported in parts per million (ppm) downfield from 85%
H3PO4 as external standard. CDCl3, CH2Cl2, C6D6 were used
as solvents. IR spectra were taken with ATI MATTSON
INFINITY FTIR 60 spectrometer and Carl Zeiss UR-10
spectrometer and Beckman IR-11 spectrometer. Mass spectra
were registered on LKB 2091 and Finnigan MAT 95. Micro-
analyses were obtained on a Carlo Erba CH NS-OEA 1108
Elemental Analyzer. Melting and boiling points were
uncorrected.
1
14
at the phosphorus center leads to higher values of JPSe
. This
can be explained by contraction of phosphorus d-orbitals.15
One can expect that the real structure of halogenoseleno-
phosphonium salts can be described by two resonance forms A
and B.
For comparison we obtained ethylselenophosphonium salts
by the alkylation of O,O,O-trialkylselenophosphates employing
the Meerweine salt [eqn. (12)].
(12)
J. Chem. Soc., Dalton Trans., 2002, 4471–4478
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t
Table 2 Conductivity of [(RO)3P–SeX]ϩXϪ species in CH2Cl2 (ε = 9.08) and 1-nitropropane (ε = 23.2) (Λot = 1/c × p × Go )
[(RO)3P–SeX]ϩXϪ
Solvent
T /ЊC
Λ0 10Ϫ1/ΩϪ1 cm2 molϪ1
[(EtO)3P–SeCl]ϩSO2ClϪ (16a)
[(ButCH2O)3P–SeCl]ϩSO2ClϪ (22a)
[(EtO)3P–SeBr]ϩBrϪ (27)
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
C3H7NO2
C3H7NO2
C3H7NO2
C3H7NO2
ϩ20.2
ϩ20.2
ϩ20.2
ϩ20.2
ϩ20.2
Ϫ30.0
Ϫ30.0
Ϫ30.0
Ϫ30.0
ϩ20.2
ϩ20.2
0.255
0.639
0.163
0.1746
49.47
0.995
1.392
2.05
[(ButCH2O)3P–SeBr]ϩBrϪ (28)
[(Me2N)3P–SeMe]ϩIϪ (13)
[(ButCH2O)3P–SeCl]ϩSO2ClϪ (22a)
[(ButCH2O)3P–SeCl]ϩSO3CF3Ϫ (22c)
[(ButCH2O)3P–SeCl]ϩSO2ClϪ (22a)
[(EtO)3P–SeCl]ϩSO2ClϪ (16a)
[(EtO)3P–SeBr]ϩBrϪ (27)
7.56
25.88
282.98
[(Me2N)3P–SeMe]ϩIϪ (13)
Table 3 Physical data for the halogenoselenophosphonium salts
Phosphonium compounds
Yielda (%)
Stability in solution (rt)
ν(P᎐Se)/cmϪ1
δP (ppm)
1JPSe/Hz
᎐
9 (Me2N)3PSeClϩClϪ
100
100
100
100
100
100
3 days
2 days
2 h
—
—
70.8
65.2f
39.0
34.8
33.6
30.0
623
652
820
847
828
854
10(Me2N)3PSeBrϩBrϪ
16a (EtO)3PSeClϩSO2ClϪ
22a (ButCH2O)3PSeClϩSO2ClϪ
27 (EtO)3PSeBrϩBrϪ
513m,522mc
—
6 h
1 h
510m,545mc
519w,579sd
550w,570se
28 (ButCH2O)3PSeBrϩBrϪ
b
a From 31P NMR. b Precipitate from CH2Cl2 solution during evaporation. c Carl Zeiss UR-10 (Ϫ60 ЊC, film). d ATI MATTSON INFINITY FTIR 60
(CsI, rt). e Beckman IR-11 (film, rt). f Lit.,4e δP 66.1.
Materials
few cases by IR spectra. Their yield, stability and spectral data
were collected in Table 3.
1,2-Dichlorocyclohexane,19a triethyloxotetrafluoroborate,20 tri-
neopentyl phosphite,19b diethyl trimethylsilyl phosphite,21
dineopentyl trimethylsilyl phosphite,21 ethyl-ortho-phenylene
phosphite,22 O,O-diethyl hydrogen phosphoroselenoate23
were prepared by literature procedures. O,O,O-Triethyl-
selenophosphate,6 O,O,O-triphenylselenophosphate,24 O,O-
(ButCH2O)3PSeBrϩBrϪ 28 brown solid (88%); mp 43–47 ЊC
(decomp., diethyl ether–benzene) (Found: C, 34.3; H, 6.28; P,
6.1; Br, 29.4%. requires C, 33.9; H, 6.21; P, 5.8; Br, 30.1%);
νmax/cmϪ1(Br–Se–Br) 190 (vs), 157 (w); m/z (CI, isobutane) 532
[Mϩ (80Se), 100%], 530 [Mϩ (78Se), 48.3%].
dimethyl-P-phenylselenophosphonate,8
phenylselenophosphinate,8
O-methyl-P, P-di-
tris(dimethylamino)phosphine
The reaction of O,O-diethyl-P-tert-butylselenophosphonate 33
with sulfuryl chloride. The reaction of 33 with sulfuryl chloride
was performed at Ϫ20 ЊC. 31P NMR spectrum recorded at that
temperature revealed the presence of But(EtO)2PSeClϩSO2ClϪ
34a (60%) and unchanged substrate 33 (40%). Raising the
temperature to 20 ЊC resulted in the formation of bis(O-ethyl-
tert-butylphosphonyl)diselenide 35 (80%). 33 δP (24.3 MHz,
CDCl3) 115.8 (1JPSe 849 Hz); 34a δP (24.3 MHz, CDCl3) 95.9
(1JPSe 690 Hz); 35 red viscous oil (Found: C, 31.2; H, 6.43; P,
13.4%; C12H28O4P2Se2 requires C, 31.6; H, 6.18; P, 13.6%);
δP (24.3 MHz, CDCl3) 60.2 (1JPSe 464 Hz); δH CDCl3 (200 MHz)
selenide,4d triphenylphosphine selenide,4b tributylphosphine
selenide,6 O,O,O-trineopentylselenophosphate [80%, mp 41–43
ЊC (Found: C, 48.3; H, 8.6; P, 7.98.%. C15H33O3PSe requires C,
48.5; H, 8.9; P, 8.3%); δP 72.6 (1JPSe 955 Hz)], O,O-diethyl-P-
tert-butylselenophosphonate32 [70%, bp 48–50 ЊC/0.2 Torr
(Found: C, 37.4; H, 7.4; P, 12.0%. Calcd for C8H19O2PSe: C,
37.2; H, 7.1; P, 12.6%); δP 115.8 (1JPSe 849 Hz)], O-ethyl-O,O-
ortho-phenyleneselenophosphate [75%, bp 56–58 ЊC/0.05 Torr,
(Found C, 36.1; H, 3.41; P, 12.01%. C8H9O3PSe requires C,
36.5; H, 3.45; P, 11.77%); δP 80.1 (1JPSe 1050 Hz)], were obtained
by addition of dry elemental selenium to the corresponding
trivalent phosphorus compounds at 5 ЊC or 40 ЊC in dry diethyl
ether or benzene.
3
3
1.21, 1.24 (2 × d, JPH 15 Hz, 18 H), 1.34, 1.36 (2 × t, JHH
7.0 Hz, 6H), 4.04–4.31 (m, 4H); m/z (EI, 70 eV) 456
[Mϩ (80Se),2.6%], 454 [Mϩ (80Se), 1.2%].
The reaction of bromoselenotriethoxyphosphonium bromide 27
with silver triflate. A solution of silver trifluoromethano-
sulfonate (3.08 g, 12 mmol) in dry diethyl ether (15 cm3) was
added dropwise at Ϫ70 ЊC to a stirred solution of 27 (freshly
prepared) (4.86 g, 12 mmol) in dichloromethane/acetonitrile
(1 : 1) (30 cm3). Stirring was continued at Ϫ70 ЊC and progress
of the reaction was monitored by 31P NMR (24.3 MHz, CDCl3)
spectroscopy. Complete conversion of 27 into bromoseleno-
triethoxyphosphonium trifluorosulfonate 27a was achieved
after 10 h. The precipitated silver bromide was filtered off at
Ϫ30 ЊC under anhydrous conditions (glovebag), (2.07 g, 92%)
and the crude reaction mixture, analysed by 31P NMR spectro-
scopy at Ϫ30Њ, showed the presence of 27a (90%), δP 36.4 (1JPSe
810 Hz). The compound 27a was stable in solution below Ϫ20
ЊC. 31P NMR spectrum recorded at that temperature revealed
the presence of a number of unidentified compounds.
Conductivity
Specific conductivity at 10Ϫ1M was measured utilizing a
Radelkis conductometer OK-102, equipped with a standard
conductivity cell (p = 0.582 cmϪ1). Measurements were made
in dichloromethane and 1-nitropropane, which were purified
according to described procedures.25 Manipulations involving
air-sensitive compounds were performed in a polyethylene
glovebag under a dry argon atmosphere. The specific conduc-
tivity of solvents and substrates was negligible.
Preparations
General procedure. A solution of sulfuryl chloride or bromine
(10 mmol) in dichloromethane (10 cm3) was added dropwise
to a stirred solution of the appropriate selenonophosphate
(10 mmol) in CH2Cl2 (25 cm3) at 0 ЊC. Stirring was continued at
the same temperature for 15 min. Crude halogenoseleno-
phosphonium compounds (besides 28) were not isolated owing
to their instability, and were characterized by 31P NMR and in
The reaction of (EtO)3PSeCl+SO2Cl؊ 16a with cyclohexene.
A solution of freshly prepared 16a (1.9 g, 5 mmol) in dichloro-
4476
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methane (15 cm3) was added by cannula to a stirred solution of
cyclohexene (0.45 g, 5.5 mmol) in the same solvent (30 cm3) at
Ϫ78 ЊC. Stirring was continued at Ϫ78 ЊC for 5 h and the
reaction mixture was then allowed to warm slowly to ambient
temperature. After evaporation of solvent the crude reaction
mixture was analysed and was found to contain, by 31P NMR
(CDCl3, 81.02 MHz) spectroscopy, selenophosphoric acid
Se-(2-chlorocyclohexyl)ester O,O-diethyl ester 52 (90%) to-
gether with O,O,O-triethylselenophosphate 15 (10%). Column
chromatography (silica gel, eluent C6H6–EtOAc in ratio 1 : 1
v/v) afforded: 5210a (1.3 g, 78%), Rf 0.5 (C6H6–EtOAc 1 : 1 v/v);
δP 19.9 ppm (1JPSe 484 Hz); δH (CDCl3, 200 MHz) 1.34 (t, 3JHH
7 Hz, 6H, OCH2CH3), 1.71–2.30 (m, 5H), 2.58–2.68 (m, 2H),
2.79 (s, 1H), 3.32 (dt, 3JHH 10.1, 4.4 Hz, HC–Cl), 3.61 (ddt, 3JHH
rubber septa. Variable-temperature spectra were recorded on a
JEOL-60H spectrometer at 24.3 MHz, and monitored usually
at intervals of 10 ЊC and 10 min. Phosphoric acid (85%) was
run prior to all samples where the chemical shift was to be
determined.
Reactions of tributylphosphine selenide 6 [run (1)], triphenyl-
phosphine selenide 3 [run (2)] with elemental chlorine and a
triphenyl phosphine with selenium chloride [run (3)]. 31P NMR
(C2H5Cl, 24.3 MHz) spectra recorded at Ϫ90 ЊC reveals the
presence of:
1) [Bu3PSeCl]ϩClϪ 7 (40%) and Bu3PϩClClϪ 8 (60%). 7 δP 60.5
(1JPSe 498 Hz); 58 δP 103.7 [lit.,26 δP 105].
2) [Ph3PSeCl]ϩClϪ 4 (70%) and Ph3PϩClClϪ 5 (30%). 4 δP 51.9
(1JPSe 544 Hz); 5 δP 65.6 [lit.,26 δP 63].
3
9.8, 4.3 Hz, JPH 13.4 Hz, HC–SeP), 4.06–4.31 (m, 4H,
3) [Ph3PSeCl]ϩSeClϪ 4a (40%), triphenylphosphine selenide 3
(40%) and Ph3PϩClClϪ 5 (20%). 4a δP 52 (1JPSe 544 Hz); 3 δP 34
(1JPSe 761 Hz) [lit.,6 δP 36]; 5 δP 65.
OCH2CH3); δC (CDCl3, 50.32 MHz) 15.63, 15.87 (OCH2CH3),
22.52 (CH2), 24.22 (CH2), 31.85 (CH2), 33.85 (CH2), 49.41 (s,
HC–SeP), 62.54 (d, 3JPC 4.3 Hz, HC–Cl), 63.51 (d, 3JPC 5.5 Hz,
3
OCH2CH3), 65.71 (d, JPC 6 Hz, OCH2CH3); m/z (CI, iso-
Raising the temperature to Ϫ40 ЊC resulted in the formation
of:
butane) 335 [Mϩ (80Se) ϩH, 100%], 333 [Mϩ (78Se) ϩH, 46.5,%],
297/299 [Mϩ Ϫ Cl], 219 [(Mϩ Ϫ Cl Ϫ Se]. 15 (0.068 g, 5.5%), Rf
0.8 (C6H6–EtOAc 1 : 1 v/v); δP 70.8 (1JPSe 942 Hz); GCMS m/z
246 [Mϩ (80Se), 16.6%], 244 [Mϩ (78Se), 8.5%] [lit.,6 δP 71.8].
trans-1,2-dichlorocyclohexane (0.03 g, 4%), Rf 0.7 (C6H6–
EtOAc 1 : 1 v/v); GCMS m/z 152 [Mϩ 0.9%], retention time 379
s (compared with authentic sample: retention time 370 s).
1) Bu3PϩClClϪ 8 (100%).
3) 3 (40%) and Ph3PϩClClϪ 5 (60%) and after raising the
temperature to 0 ЊC:
2) Ph3PϩClClϪ 5 (100%) was found by means 31P NMR
spectroscopy.
Reactions of O,O-dimethyl-P-phenylselenophosphonate 37
and O-methyl-P,P-diphenylselenophosphinate 38 with sulfuryl
chloride, elemental chlorine and elemental bromine. From 37
and surfuryl chloride and elemental chlorine a crude reaction
Preparation of ethylselenotriethoxyphosphonium tetrafluoro-
borate 62. To a solution of triethyloxonium tetrafluoroborate
(0.95 g, 5 mmol) in 1-nitropropane (20 cm3) a solution of
O,O,O-triethylselenophosphate 15 (1.2 g, 20 mmol) in CH2Cl2
(5 cm3) was added dropwise at Ϫ80 ЊC. Stirring was continued
at that temperature for 48 h. The reaction was monitored and
the reaction mixture was found by 31P NMR spectroscopy, to
contain 62 (30%) together with unchanged substrate (70%). The
reaction mixture was then allowed to warm to 0 ЊC and stirred
at that temperature for 48 h. 31P NMR spectrum recorded at
0 ЊC revealed of the presence of 62 (70%) and 15 (30%). 62 δP
43.7 (1JPSe 664 Hz) (stable for 5 h in CH2Cl2–1-nitropropane
solution). All attempts to obtain pure 62 failed because of its
instability.
mixture was obtained at Ϫ90 ЊC and found by means of its 31
P
NMR (C2H5Cl, 24.3MHz) spectrum to contain 39 (100%). 39
(MeO)2PhPSeClϩSO2ClϪ (Cl)Ϫ δP 72.7 (1JPSe 701 Hz). After
raising the temperature to Ϫ10 ЊC 31P NMR spectrum recorded
at that temperature reveals the presence of methyl phenyl
chlorophosphonate 43 δP 30.0 [lit.,27 δP 29.5].
From 37 and elemental bromine the crude 40 (MeO)2PhPSe-
BrϩBrϪ (100%) was obtained at Ϫ90 ЊC. 40 δP 69 (1JPSe 696 Hz).
Raising the temperature to Ϫ30 ЊC resulted in the formation of
methyl phenyl bromophosphonate 44 δP 11.3.
From 38 and sulfuryl chloride and elemental chlorine
(MeO)Ph2PSeClϩSO2ClϪ (Cl)Ϫ 41 (100%) was obtained at
Ϫ80 ЊC, δP 85 (1JPSe 605 Hz). Complete conversion of 41 into
diphenyl phosphinoyl chloride 45 was achieved after raising the
temperature to Ϫ20 ЊC. 45 δP 45.2 [lit.,28 δP 42.7].
From the reaction of 38 and elemental bromine, performed at
Ϫ85 ЊC the crude (MeO)Ph2PSeBrϩBrϪ 42 (100%) was obtained
and after raising the temperature to Ϫ40 ЊC was found by
means 31P NMR (C2H5Cl, 24.3MHz) recorded at that temper-
ature to have converted completely (100%) into diphenyloxy-
bromophosphine 46. 42 δP 82.4 (1JPSe 592 Hz). 46 δP 71.2 [lit.,29
δP 78.4].
Preparation of O,O,O,O-tetraethyl-sym-monoselenopyro-
phosphate 61. A solution of freshly prepared 16a (0.42 g, 1.1
mmol) in dichloromethane (5 cm3) was added by cannula to a
stirred solution of diethyl trimethylsilyl phosphite 60 (0.23 g,
1.1 mmol) in CH2Cl2 (2 cm3) at 0 ЊC and stirring was continued
for 24 h at that temperature. Solvent was evaporated under
reduced pressure to afford crude 61 (0.34 g, 88%), δP 11.5 (1JPSe
427 Hz) [lit.,3c δP 11.8 (1JPSe 425 Hz)]; νmax/cmϪ1 (film) (P᎐O)
᎐
1230 (s), (POC) 1030 (s), (P᎐Se) 420 (w); m/z (CI, isobutane)
᎐
355 [Mϩ (80Se) ϩ H, 100%], 353 [Mϩ (78Se) ϩ H, 49.2%], 217/
219 [C4H11O3PSe, 5.3/11.2%].
Reactions of O,O,O-triphenylselenophosphate 47 with sulfuryl
chloride [run (1)], and elemental chlorine [run (2)] and bromine
[run (3)]. 31P NMR (CH2Cl2, 24.3MHz) spectra recorded at
Ϫ80 ЊC reveals the presence of:
Preparation of dibromo(triphenylphosphine)selenium(II),
Ph3PSeBr2. From triphenylphosphine selenide 3 (0.55 g, 1.6
mmol) and bromine (0.23 g, 1.4 mmol) Ph3PSeBr2 was obtained
as a yellow powder, according to the procedure of Williams
and Wynne.4b Ph3PSeBr2: (0.53 g, 75%) mp 90 ЊC (decomp.); δP
(CDCl3, 81.02 MHz) 50.7 (br s), δP (C6D6, 81.02 MHz) 42.0 (br
s); CP/MAS solid state 31P NMR spectrum was recorded at
121.46 MHz (Bruker 300 DSX) δP 42.13 (br s) [lit.,5 δP 51.96].
Ph3PϩBrBrϪ δP (CDCl3, 81.02 MHz) 50.6 (br s).
1) (PhO)3PSeClϩSO2ClϪ 48a (60%) and (PhO)3PϩClClϪ 50
(40%). At Ϫ20 ЊC the only product is 50. 48a δP 27.4 (1JPSe 953
Hz), 50 δP 7.3 [lit.,30 δP 7.0].
2) (PhO)3PSeClϩClϪ 48 (35%) and (PhO)3PϩClClϪ 50 (65%).
At Ϫ50 ЊC the only product is 50. 48 δP 26.7 (1JPSe 950 Hz), 50 δP
7.3.
3) (PhO)3PSeBrϩBrϪ 49 (80%) and (PhO)3PϩBrBrϪ 51 (20%).
Raising the temperature to Ϫ60 ЊC resulted in the formation of
51 (100%). 49 δP 24.5 (1JPSe 1008 Hz), 51 δP 4.6 [lit.,30 δP 3.6].
Low-temperature 31P NMR measurements
A 10 mm NMR tube (cooled in liquid N2 or acetone–solid CO2)
was charged with the compounds (0.5–1 mmol) in dichloro-
methane or ethyl chloride. All operations were carried out in a
dry argon atmosphere. The tubes were closed tightly with
Reaction of ethyl ortho-phenylene phosphite 57 with phenyl-
selenyl chloride. The reaction of 57 with PhSeCl was performed
J. Chem. Soc., Dalton Trans., 2002, 4471–4478
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at Ϫ80 ЊC. The reaction mixture, analysed by 31P NMR
(CH2Cl2, 24.3MHz) spectroscopy, showed the presence of
unchanged substrate 57 (30%) and the phosphorane 58 (70%) δP
Ϫ36.3 (1JPSe 698 Hz). Raising the temperature to Ϫ50 ЊC
resulted in the formation of 2,2-dichloro-2-ethoxy-1,3,2λ5-
benzodioxaphosphole 55 (80%) δP Ϫ34.6 [lit.,31 δP Ϫ34.5 ppm]
and diphenyl diselenide, identified by GC (analysis of crude
reaction mixture at rt), by comparison with authentic samples.
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