Fluorinated phosphorus-selenium heteroatom compounds: Phenylphosphonofluorodiselenoic salts, adducts, and esters

Article abstract of DOI:10.1021/ic400612w

2,4-Bis(phenyl)-1,3-diselenadiphosphetane-2,4-diselenide, [PhP(Se)(μ-Se)]₂, Woollins' reagent (WR), reacts with dry KF or tetrabutylammonium fluoride (TBAF) at room temperature generating the corresponding potassium and tetrabutylammonium phenyldiselenofluorophosphinates 1 and 2 in almost quantitative yields. Treating 1 with equimolar amounts of tetraphenylphosphonium chloride or 1,3-dimesityl-1H-imidazol-3-ium chloride in THF at room temperature afforded the corresponding organic adducts 3 and 4 in 90% and 87% yields. Reaction of 1 with mono- and dihalogenated alkanes gave a series of esters of phenylphosphonofluoridodiselenoates 5-8 and 9 in 79-93% yields. Two representative crystal structures are reported. Published 2013 by the American Chemical Society.

Full text of DOI:10.1021/ic400612w

Article
pubs.acs.org/IC
Fluorinated Phosphorus−Selenium Heteroatom Compounds:
Phenylphosphonofluorodiselenoic Salts, Adducts, and Esters
Guoxiong Hua, Junyi Du, Alexandra M. Z. Slawin, and J. Derek Woollins*
EaStCHEM School of Chemistry, University of St Andrews, Fife KY16 9ST, United Kingdom
S
* Supporting Information
ABSTRACT: 2,4-Bis(phenyl)-1,3-diselenadiphosphetane-2,4-disele-
nide, [PhP(Se)(μ-Se)]2, Woollins’ reagent (WR), reacts with dry KF
or tetrabutylammonium fluoride (TBAF) at room temperature
generating the corresponding potassium and tetrabutylammonium
phenyldiselenofluorophosphinates 1 and 2 in almost quantitative
yields. Treating 1 with equimolar amounts of tetraphenylphospho-
nium chloride or 1,3-dimesityl-1H-imidazol-3-ium chloride in THF at
room temperature afforded the corresponding organic adducts 3 and
4 in 90% and 87% yields. Reaction of 1 with mono- and
dihalogenated alkanes gave a series of esters of phenylphosphono-
fluoridodiselenoates 5−8 and 9 in 79−93% yields. Two representa-
tive crystal structures are reported.
TBAF.25 The importance of phosphoro-fluorine compounds in
pure and applied chemistry invigorated our interest in
synthesizing new phosphorodiselenoates bearing the P−F
motif.
INTRODUCTION
■
Organophosphorus−fluorine compounds (OPFCs) bearing P−
F bonds have been of considerable interest since the 1970s due
to their diverse chemical and biological activities. They are an
important class of organophosphorus compounds and are
recognized as selective phosphorylating agents in synthesis, and
efficient inhibitors of several classes of enzymes.1−12 The
thiophosphate anions A−C (Scheme 1) were first prepared
2,4-Bis(phenyl)-1,3-diselenadiphosphetane-2,4-diselenide
[PhP(Se)(μ-Se)]2, Woollins’ reagent (WR), has become
known as a versatile selenation reagent in synthetic chemistry
in recent years26−40 because of its ease of preparation and
handling.41 As part of our investigation into the reactivity of
WR toward inorganic or organic substrates herein, we report
the synthesis of potassium and tetrabutylammonium salts of
phenylphosphonofluoridodiselenoates, and the related organic
adducts and esters. To the best of our knowledge this is the first
reported synthesis and characterization of phenylphosphono-
fluorodiselenoate [PhP(Se)(Se)F]− and its structural ana-
logues, providing a valuable addition to the library of
phosphodiselenoate compounds.
Scheme 1. Fluorinated Thiophosphate Anions A−C
from the reaction of alkali metal fluorides and P4S10 by Roesky
and co-workers.13,14 Since then, the synthesis of thiophosphoryl
halides SPF3 and SPFCl2, and their derivatives S
PF2NH2, SPFClNH2, SPF2NPF2X (X = Br, NH2 or
OH), SPF2NPCl3, and SPF2NPF2NCNSiMe3,
was reported.15−20 However, there are few examples of the
synthesis of simple phosphonofluorodithioates ROP(S)(S−)F
containing a fluorine atom attached directly to the phosphorus
atom.15,21,22 The nucleoside phosphonofluoridodithioate
monoesters were prepared via oxidation of nucleoside
phosphonodithioate with I2 in pyridine in the presence of
TMSCl, followed by addition of triethylamine trishydrofluoride
(TAF).23,24 Similar analogues were obtained from a one-pot
sequential reaction of 1,3,2-dithiaphospholane P(III) deriva-
tives, which were converted readily into the corresponding
P(V) compounds by addition of elemental sulfur and finally
into phosphonofluoridodithioates by further treatment with
RESULTS AND DISCUSSION
■
WR reacted with 2 equiv of fresh dry potassium fluoride at 80
°C in acetonitrile under N2 atmosphere for 1 h giving
potassium phenylphosphonofluoridodiselenoate 1 in 84%
yield, or with 2 equiv of tetrabutylammonium fluoride
(TBAF) at room temperature in tetrahydrofuran for 1 h to
give tetrabutylammonium phenylphosphonofluoridodiselenoate
2 in 99% yield (Scheme 2). Both reactions were fast and very
straightforward and must be performed in a moisture- and
oxygen-free atmosphere.
Compound 1 was obtained as a pale yellow solid and is
insoluble in organic solvents but soluble in oxygen-free water.
Received: May 2, 2013
Published: July 1, 2013
Published 2013 by the American Chemical
Society
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Scheme 2. Synthesis of Potassium and Tetrabutylammonium
Salts of Phenylphosphonofluoridodiselenoate 1 and 2
Compound 2 was obtained as brown sticky oil and is soluble in
organic solvents, and shows good air stability at room
1
temperature. 1 and 2 were fully characterized by H, 13C, 31P,
77Se, and 19F NMR; IR spectroscopy; and mass spectrometry.
Both compounds showed the anticipated molecular ion peaks
[M − K]+ or [M − NnBu4]+ and satisfactory accurate mass
measurement. The 31P NMR spectra exhibit doublets at δp =
105.1 ppm in compound 1 and 102.6 ppm in compound 2,
respectively, attributed to the P−F single bond. Each signal is
Figure 1. X-ray crystal structure of 3 (hydrogen atoms omitted for
clarity). Selected bond lengths (Å) and angles (deg) (esd’s in
parentheses): Se(1)−P(2) 2.1136(16), Se(2)−P(2) 2.1163(14),
F(1)−P(2) 1.604(3); Se(1)−P(2)−Se(2) 108.83(14), Se(1)−P(2)−
F(1) 107.47(10), Se(2)−P(2)−F(1) 106.44(10).
1
flanked by one set of small satellites with J(P,Se) coupling
2) reveals they crystallize as ion-separated species. The
phenylphosphonofluoridodiselenoate anion contains a distorted
constants being 728 (for compound 1) and 770 Hz (for
compound 2); these values are considerably bigger than those
in similar PSe2 ions27,42 indicating the significant electronic
effect of the fluorine atom. In the 19F NMR spectra, doublets
are observed [1J(P,F) coupling constants of 1073 Hz for 1 and
1068 Hz for 2] in accord with the known literature values,14,43
2
along with small J(Se,F) satellites with coupling constants of
31.0 Hz for compound 1 and 31.5 Hz for compound 2.
Furthermore, the 77Se NMR spectra showed double doublets at
1
δSe = 136.3 ppm with a J(P,Se) coupling constant of 728 Hz
2
and a J(Se,F) coupling constant of 31.0 Hz for compound 1,
1
and at δSe = 139.5 ppm with a J(P,Se) coupling constant of
770 Hz and a 2J(Se,F) coupling constant of 31.5 Hz for
1
compound 2. In the H NMR spectra, compound 1 showed
only phenyl protons, while in compound 2 signals for the
phenyl and n-butyl groups were observed.
Treating 1 with an equimolar amount of tetraphenylphos-
phonium chloride in degassed water in room temperature led
to the formation of tetraphenylphosphonium
phenylphosphonofluoridodiselenoate 3 in 90% yield as a
white solid. Similarly, reacting compound 1 with 1,3-
dimesityl-1H-imidazol-3-ium chloride under identical condi-
tions provided 1,3-dimesityl-1H-imidazol-3-ium phenylphos-
phonofluoridodiselenoate 4 in 87% yield as a pale pink solid
(Scheme 3). Both compounds 3 and 4 are air stable and soluble
in normal organic solvents. The 31P, 77Se, and 19F NMR spectra
of compounds 3 and 4 showed similar patterns to 1 with
Figure 2. X-ray crystal structure of 4 (hydrogen atoms omitted for
clarity). Selected bond lengths (Å) and angles (deg) (esd’s in
parentheses): Se(1)−P(1) 2.119(3), P(1)−F(1) 1.610(5), P(1)−
Se(2) 2.108(3); Se(1)−P(1)−Se(2) 120.29(11), Se(1)−P(1)−F(1)
106.2(2), Se(2)−P(1)−F(1) 107.4(3).
tetrahedral phosphorus atom with P−Se bond distances
[2.1136(16), 2.1163(14) Å in compound 3, and 2.119(3),
2.108(3) Å in compound 4] shorter than those found in amine
salts of bisdiselenophosphonic acid [2.1280(11)−2.1350(12)
Å];44 however, they are still intermediate between single bond
[ca. 2.38 Å] and double bond [PSe double bond length ca.
2.08 Å],45 indicating the delocalization of the negative charge
over the FPSe2 fragment.
1
1
2
identical J(P,F), J(P,Se), and J(Se,F) coupling constants.
Crystals of 3 and 4 suitable for X-ray analysis were obtained
by diffusion of hexane into dichloromethane solutions at room
temperature. X-ray structural analysis of 3 and 4 (Figures 1 and
Reacting 1 with an equimolar amount of halogenated alkanes
in dry THF in room temperature generates a series of esters of
phenylphosphonofluoridodiselenoates 5−8 in 84−92% yields
(Scheme 4). Furthermore, 1,4-phenylenebis(methylene) bis-
(phenylphosphonofluoridodiselenoate) 9 was prepared by the
reaction of compound 1 with 0.5 equiv of 1,4-bis-
(bromomethyl)benzene under identical conditions in 79%
yield as shown in Scheme 5. The esters 5−9 are air-stable oils
or pastes and are soluble in common organic solvents such as
dichloromethane, trichloromethane, acetone, and THF. Com-
pounds 5−9 were fully characterized by multinuclear NMR and
IR spectroscopy and accurate mass measurement. All new
compounds showed the anticipated molecular ion peaks [M]+,
and were confirmed by satisfactory accurate mass measure-
ments. The 31P NMR spectra of esters 5−9 showed two
Scheme 3. Derivatives 3 and 4 of Potassium
Phenylphosphonofluoridodiselenoate 1
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Inorganic Chemistry
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Scheme 4. Synthesis of Esters of
Phenylphosphonofluoridodiselenoates 5−8
ACKNOWLEDGMENTS
■
We are grateful to the University of St Andrews for financial
support and the EPSRC National Mass Spectrometry Service
Centre (Swansea) for mass spectral measurements. We also
thank Professor Andrew Smith (the University of St Andrews)
for the kind supply of 1,3-dimesityl-1H-imidazol-3-ium
chloride.
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ASSOCIATED CONTENT
* Supporting Information
Experimental details, crystal data (CIF), and spectra. This
material is available free of charge via the Internet at http://
pubs.acs.org.
■
S
AUTHOR INFORMATION
Corresponding Author
*Phone: (+44)-1334-463384. E-mail: jdw3@st-and.ac.uk.
■
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Notes
The authors declare no competing financial interest.
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