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Formation of Phosphorus Oxoacids with P-P-P-P-P-P and P-P-P-P-P Frameworks and Related Compounds 1
T O S H I O NAKASHIMA , HIROHIKO WAKI, and S H I G E R U OHASHI Department of Chemistry, Faculty of Science, Kyushu University 33, Hakozaki, Higashiku, Fukuoka, 812 Japan
The following ten kinds of phosphorus oxoacids with P-P bonds are known at present (1, 2): P -P , P -P -O-P -P , (-P -P -O-) , P -P -O-P , P -P -O-P , P -O-P -P -O-P , P -P , P -P , P -P -P and (-P -) . Among these compounds we reported the formation of P -O-P -P -O-P by the substitution reaction between P -P and P -O-P at the ICPC., 1979 (2). The last compound i n the above series, (-P -)6, was f i r s t prepared by Blaser and Worms i n 1959 (3). This compound has a six-membered P-P bond ring structure as shown i n Formula 1. It has been known that this ring acid i s decomposed by hydrolysis into a complicated mixture of various phosphorus oxoacids and f i n a l l y converted into a mixture of monomeric phosphorus oxoacids; phosphinic acid (hypophosphorous acid, P ), phosphonic acid (phosphorous acid, P ) and orthophosphoric acid ( P ) . Therefore, there i s a p o s s i b i l i t y that some new phosphorus oxoacids with P-P bonds may be found i n the decomposition products by partial hydrolysis of (-P -) ring acid. This paper describes the separation of new phosphorus oxoacids with P-P-P-P-P-P and P-P-P-P-P frameworks and related compounds from the decomposition products of (-P -) ring acid by ion-exchange chromatography and their identification by the measurements of their UV absorption spectra and by the charge determination of anionic species of these compounds. Decomposition products by oxidation of (-P -) ring acid were also examined. IV
IV
IV
III
IV
IV
IV
V
2
II
IV
IV
III
IV
IV
IV
III
IV
IV
IV
IV
IV
III
II
IV
II
III
6
III
IV
IV
IV
IV
III
III
III
III
I
III
V
III
6
III
6
III
6
Experimental The mixed potassium
sodium
III
salt of (-P -)
6
ring
acid
1
Current address: Department of Inorganic and Analytical Chemistry, Hebrew University of Jerusalem, Jerusalem, Israel. 0097-6156/81/0171-0267$05.00/0 © 1981 American Chemical Society
In Phosphorus Chemistry; Quin, L., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.
was
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prepared by the B l a s e r and Worms' procedure (3), i . e . , the o x i d a t i o n of red phosphorus w i t h bromine and the s e p a r a t i o n of the de s i r e d compound from the other products. ^ The potassium sodium s a l t of (-P r i n g a c i d was hydrol y z e d i n d i l u t e h y d r o c h l o r i c a c i d at 21°C f o r 40-60 min. In some cases the s a l t of (-P^-)^ r i n g a c i d i n potassium hydrogen carbo nate s o l u t i o n was o x i d i z e d with hydrogen peroxide at 11-20°C f o r 20-25 h. The decomposition products were separated by eluting with potassium c h l o r i d e s o l u t i o n on a column packed with anion-exchange r e s i n , Dowex 1x4 i n c h l o r i d e form. During the e l u t i o n the concen t r a t i o n of potassium c h l o r i d e i n the eluent was increased expo nentially. The phosphorus contents i n e f f l u e n t f r a c t i o n s were determined c o l o r i m e t r i c a l l y with a molybdenum(V)-molybdenum(VI) reagent (4). For UV s p e c t r a l measurements a H i t a c h i r e c o r d i n g spectropho tometer ESP-3T was employed w i t h a 5-cm quartz c e l l . Charges of a n i o n i c species of phosphorus oxoacids were d e t e r mined by an ion-exchange e q u i l i b r i u m method. For t h i s purpose d i s t r i b u t i o n r a t i o s , D, of phosphorus oxoacid between an anionexchange r e s i n Dowex 1x4 phase and an aqueous s o l u t i o n phase con t a i n i n g tetramethylammonium c h l o r i d e as a supporting e l e c t r o l y t e were obtained from the absorbancies of phosphorus oxoacid i n the aqueous s o l u t i o n phase before and a f t e r e q u i l i b r a t i o n . D was de f i n e d as the r a t i o of the c o n c e n t r a t i o n of phosphorus i n the r e s i n phase to the c o n c e n t r a t i o n of phosphorus i n the s o l u t i o n phase. Results and D i s c u s s i o n (_5, 6) A complicated mixture produced by h y d r o l y s i s of (-P"^*-)/- r i n g a c i d was separated by ion-exchange chromatography. The e l u t i o n peaks due to Compounds 1 and 2 were always observed i n the l a t e s t part of an e l u t i o n p a t t e r n . Compounds 1 and 2 have c h a r a c t e r i s t i c UV a b s o r p t i o n at 272 and 255 nm, r e s p e c t i v e l y , a n d were presumed from t h e i r e l u t i o n p o s i t i o n s to be phosphorus oxoacids having a r a t h e r long P-P chain. D values of Compounds 1 and 2 i n an aqueous s o l u t i o n o f t e t ramethyl ammonium c h l o r i d e of v a r i o u s c o n c e n t r a t i o n s at pH about 7 were measured. The p l o t s of l o g D values against l o g [CI ] values showed a l i n e a r r e l a t i o n s h i p between these two v a r i a b l e s . The slopes of these s t r a i g h t l i n e s i n d i c a t e d that anion charges of Compounds 1 and 2 at n e u t r a l pH are -6.0 and -4.8, r e s p e c t i v e l y . A method f o r t h i s a n a l y s i s was d i s c u s s e d i n reference (5). The r e s u l t s mentioned above suggest that Compound 1 i s pro duced immediately a f t e r the h y d r o l y t i c r i n g opening of the parent compound, (-p-^-)
H0 2
π
>
ρ
_ m_piii_piii_ iii_ ]y p
p
p
6d
In Phosphorus Chemistry; Quin, L., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.
NAKASHiMA E T A L .
55.
Phosphorus
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Oxoacids
A l l the protons o f except one of two protons a t the end P ^ unit are considered from the d i s s o c i a t i o n behavior o f other known phosphorus oxoacids to be completely d i s s o c i a t e d at n e u t r a l pH (1_). Therefore, P ^ may have a charge of about - 6 under the present ex perimental c o n d i t i o n s . ^ Further h y d r o l y t i c decomposition of (-P - ) ^ r i n g a c i d may produce the f o l l o w i n g three kinds of phosphorus oxoacids with a PP-P-P-P framework ( P ). Downloaded by UNIV OF CALIFORNIA SAN DIEGO on November 12, 2015 | http://pubs.acs.org Publication Date: November 11, 1981 | doi: 10.1021/bk-1981-0171.ch055
5 d
p*_p™-P*- *-P* P
pi
+
(P - l
)
2H 0 m
(-P -)
n
6
m
m
m
P -P .p -P -P
w
pn_pm_pm_ iii_pii p
+ +
P
m
( P
v
P
(
P
5 d
5 d
-2 )
-
3
)
At n e u t r a l pH, Ρ -1, P^^-2 and P^^-3 may have a charge of -5 ~ -6, -5 and -5, r e s p e c t i v e l y . The r e s u l t of the charge determination mentioned above suggests t h a t Compound 2 i s any one or a mixture of these three compounds. An anion charge of a copper complex of Compound 2 was determined by the anion-exchange e q u i l i b r i u m method to be -3.2. T h i s means that P^-3 i s the most probable compound or the most predominant compound i n a mixture of these three spe cies . Since the number of phosphorus atoms i n a molecule of Com pound 1 or 2 i s considered to be s i x o r f i v e , the molar absorp t i v i t y , ε, of each can be c a l c u l a t e d . The curves of l o g ε v s . wavelength f o r Compounds 1 ( P^, ) and 2 ( P ^ ) and the parent (_ρΠΙ_)^ r i n g a c i d were obtained (5). A comparison of the p o s i t i o n of the longest wavelength peaks (or shoulders) f o r these new longer chain species ( P ^ and P ^ l and the known s h o r t e r chain s p e c i e s , P#-pIV ( P ) and pTV.pïïTptV ( P ^ ) i s very i n t e r e s t i n g . I t was revealed that there i s a l i n ear r e l a t i o n s h i p between the wavenumber of the above mentioned peak or shoulder and the number of phosphorus atoms i n a molecule. A s p e c i e s which has a shoulder a t the p o s i t i o n corresponding to l?4d was a l s o found i n a mixture of h y d r o l y t i c products of ( - P ^ - ) ^ r i n g a c i d , though i t could not always be detected i n the chromatographic s e p a r a t i o n . T h i s behavior mentioned above may be analogous to that observed i n polysulfide series (7). This s p e c t r a l r e l a t i o n a l s o supports the s t r u c t u r e s of P ^ and P ^ . I t was very d i f f i c u l t to o b t a i n the new compound o f P ^ or P,^ as a s o l i d s a l t , because a very small amount o f P ^ or P ^ was present i n very d i l u t e aqueous s o l u t i o n . However, the p r e p a r a t i o n of a small volume of P ^ s o l u t i o n of r e l a t i v e l y high c o n c e n t r a t i o n was s u c c e s s f u l l y achieved by the f o l l o w i n g procedure; the e n r i c h ment of phosphorus oxoacid species i n t o a c e r t a i n amount of an anion-exchange r e s i n and the subsequent e l u t i o n with a c a l c u l a t e d volume of potassium c h l o r i d e s o l u t i o n of a proper c o n c e n t r a t i o n . By adding small volumes of magnesium c h l o r i d e s o l u t i o n and methyl a l c o h o l to the r e s u l t i n g P ^ s o l u t i o n , 4 mg of magnesium s a l t of ^6d obtained. 2 d
w
a
s
In Phosphorus Chemistry; Quin, L., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.
PHOSPHORUS
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"Decomposition products o f (-P r i n g a c i d with hydrogen peroxide i n potassium hydrogen carbonate s o l u t i o n were a l s o exam ined i n a s i m i l a r way. Compound 3 having a c h a r a c t e r i s t i c absorp t i o n spectrum with a peak a t 268 nm was found i n the decomposition products. At pH 3.2, the spectrum of Compound 3 g r a d u a l l y changed i n t o a spectrum of . A c o n s i d e r a b l e amount o f diphosphate, Ρ -0-P , was always found i n the same decomposition products. T h i s suggests that the o x i d a t i o n o f phosphorus oxoacid with a frame work composed of only P-P bonds leads to the formation o f a com pound having a P-O-P bond. In order to c a l c u l a t e the average o x i d a t i o n number o f phosphorus atoms ^ / _ i n Compound 3, the f i n a l h y d r o l y s i s \ / ^ ^\Γ>^ products o f Compound 3, i.e., Ρ , ^0H P " and P , were separated and deHO I I 0 termined by ion-exchange chromato\ V graphy. The average o x i d a t i o n number 0 ^ \ ^ ^x^^OH obtained by t h i s a n a l y s i s was +3.43. 0 The f a c t s mentioned above may suggest that Compound 3 has a s t r u c t u r e of Formula 2 Formula 2. The average oxidation number o f phosphorus atoms i n Formula 2 i s c a l c u l a t e d to be +3.40. Since Compound 3 i s r a t h e r unstable even a t n e u t r a l pH, some of the techniques such as the anion-exchange e q u i l i b l i u m method f o r charge determination, etc.,cannot be used f o r f u r t h e r i n v e s t i g a t i o n . 113
V
Literature Cited 1.
2. 3. 4. 5. 6. 7.
Grayson, M. ; G r i f f i t h , E. J., Ed. ; "Topics i n Phosphorus Chemistry", Vol. 1, Interscience Publishers, New York 1964; pp. 113-187. Yoza, N.; Yoshidome, H., Ohashi, S. J . Chromatogr. 1978, 150, 393. Blaser, Β.; Worms, Κ. Η. Ζ. Anorg. Allgem. Chem. 1959, 300, 237. Yoza, N.; Ishibashi, K.; Ohashi, S. J . Chromatogr. 1977, 134, 497. Nakashima, T.; Waki, Η., Ohashi, S. : J . Inorg. Nucl. Chem. 1977, 39, 1751. Nakashima, T., Nakamura, S.; Sutoh, H.; Ohashi, S. J . Inorg. Nucl. Chem. 1981, 43, 612. Fehér, F., Münzner, H. Chem. Ber. 1963, 96, 1131.
R E C E I V E D July 7, 1981.
In Phosphorus Chemistry; Quin, L., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.
