114 Reactivity of Tricoordinated Phosphorus Compounds A M e c h a n i s t i c S t u d y w i t h a Variety o f Substrates C. DENNIS HALL, ROBERT C. EDWARDS, JOHN R. LLOYD, PAUL D. BEER, PHILIP J. H A M M O N D , ALBERTO O. D'AMORIM , and MELVIN P. MELROSE Downloaded by NORTHWESTERN UNIV on October 17, 2017 | http://pubs.acs.org Publication Date: November 11, 1981 | doi: 10.1021/bk-1981-0171.ch114
1
1
Department of Chemistry, King's College, University of London, Strand, London WC2R 2LS, England
Tricoordinated phosphorus compounds react with a wide range of substrates and a great deal of mechanistic information is now available within this area. The classical work involved the quaternization of phosphines with alkyl halides and the famous Arbusov reaction which prompted intensive studies in the field of organophosphorus chemistry. Both reactions involve nucleophilic attack of tricoordinated phosphorus on tetrahedral carbon and show all the characteristics of non-polar reactants combining through polar transition states although the solvent effects are sometimes quite modest. Sub sequent studies have demonstrated nucleophilic attack on activated alkenes, activated alkynes, the carbonyl group and halogen whilst in the Perkow reaction (eqn. 1) all four possible sites in 1-3
4
5,6
2
7
7
1-3
8
3
the substrate (halogen, sp C, carbonyl carbon and carbonyl oxygen) have at some time been proposed as the site of nucleophilic attack. In more recent years the range of substrates has broadened to include the O - O bond in various peroxides, the S - S bond, the S - O bond in sulphenate esters, the S - Ν bond in sulphenamides and others which are too numerous to mention. It i s the purpose of this paper to collate much of the available information and in combination with new kinetic data to offer an overall view and rationalization of the reactivity of tricoordinated phosphorus compounds. A selection of the kinetic information available from a variety of substrates i s shown in Table I in which the conditions of temperature and solvent have been maintained as uniform as possible. 2,5,9
10,11
12,13
14,15
16,17
1Theoretical contributions. 0097-6156/81/0171-0551$05.00/0 © 1981 American Chemical Society Quin and Verkade; Phosphorus Chemistry ACS Symposium Series; American Chemical Society: Washington, DC, 1981.
PHOSPHORUS
552
TABLE 1.
CHEMISTRY
Second-order r a t e c o e f f i c i e n t s f o r t h e r e a c t i o n o f Ρ(III) compounds w i t h f o u r t y p e s o f s u b s t r a t e ΙΟ
3
χ k
s"
1
£ mole
2
1
a t 25°C Source
Substrate Ph P
Ph P0R
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3
Mel
a
Et00Et
5.0 b
b
3
29 χ 1 0 ~
3.3
12,520
3
0.35
c, d
f
c
870
0.6
c
9700
^ 5.0
4.9 χ 1 0 "
3
1350
4.6
$8
Ρ(OR)
2
2.2
3.6
4.4 χ 1 0 "
PhSSSPh
PhP(0R)
2
3
c, e
1
R = P r throughout except f o r S /P(0R) f o r which R = E t . a ) i n C H C N b) i n C H C H c ) t h i s w o r k d) Songstad J . A c t a . Chem. S c a n d . ( A ) 1976, 3 0 , 724 e) r e f . 1 2 . f ) v e r y s l o w . 8
3
6
5
3
3
I t i s immediately obvious t h a t w i t h Mel the r a t e s of r e a c t i o n decrease i n the a n t i c i p a t e d order of n u c l e o p h i l i c r e a c t i v i t y , i . e . , P h P > P h P 0 R > P h P ( O R ) > P ( 0 R ) whereas w i t h t h e o t h e r s t h e rate order f o l l o w s t h e sequence Ph P0R > P h P ( 0 R ) > Ph P * (RO) P. The l a t t e r " a n o m a l o u s " b e h a v i o u r has been a s c r i b e d t o t h e d i r e c t f o r m a t i o n o f p e n t a c o o r d i n a t e d p r o d u c t s from P ( I I I ) and t h e sub s t r a t e a s d i s t i n c t f r o m n u c l e o p h i l i c d i s p l a c e m e n t by p h o s p h o r u s so t h a t t h e s t a b i l i t y o f t h e T.S. l e a d i n g t o t h e p e n t a c o o r d i n a t e d m o l e c u l e d i c t a t e s t h e rate.£>ϋ> 11 T h e r e i s no d o u b t t h a t s e v e r a l r e a c t i o n s w h i c h d i s p l a y t h e anomalous r a t e sequence (eg w i t h p e r o x i d e s , s u l p h e n a t e e s t e r s a n d d i t h i e t e n e s ) do g i v e p e n t a c o o r d i n a t e d p r o d u c t s and t h e p r o p o s a l i s g i v e n f u r t h e r s u p p o r t by t h e r e a c t i o n o f d i e t h y l p e r o x i d e w i t h a s e r i e s o f c y c l i c phosphines i n w h i c h t h e r a t e sequence p a r a l l e l s t h e s t a b i l i t y o f t h e P ( V ) products.il F u r t h e r m o r e , under t h e a p p r o p r i a t e c o n d i t i o n s p e n t a c o o r d i n a t e d p r o d u c t s a r e a l s o f o r m e d f r o m a l k e n e s ( e q n . 2) and a l k y n e s i i L (eqn. 3) a n d a l t h o u g h r a t e d a t a i s o n l y a v a i l a b l e f o r 3
2
2
3
2
2
OR
R 'ΠΗ Ar P(0R) . n
3
n
+ CH =CHY
3
1
^ >
2
3
(2)
A r P (OR) _ C H C H Y n
3
n
2
2
31
η = 1 or 2
Y = C 0 E t o r CN
δ
2
Ρ (H PO ) 3
l+
-50 (η -35 (η
2) 1)
OR*
1
R *OH Ar POR + PhC5CC0 Et 2
2
>
Ar Ρ(OR)C(Ph)-CHC0 Et 2
2
31
6
Ρ = -54
Quin and Verkade; Phosphorus Chemistry ACS Symposium Series; American Chemical Society: Washington, DC, 1981.
(3)
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114.
HALL E T A L .
Tricoordinated
Phosphorus
553
Compounds
p h o s p h i n i t e s a n d p h o s p h o n i t e s , t h e same r e a c t i o n s w i t h p h o s p h i t e s and t r i a r y l p h o s p h i n e s a r e q u a l i t a t i v e l y v e r y much s l o w e r . How e v e r , whereas t h e r e a c t i o n w i t h p e r o x i d e i s u n a f f e c t e d by s o l v e n t c h a n g e s , ϋ » 1 £ t h e r e a c t i o n s w i t h M e l , PhSSSPh and SQ show i n c r e a s i n g s e n s i t i v i t y t o s o l v e n t p o l a r i t y s o t h a t r e a c t i o n w i t h Sg appears t oproceed through a h i g h l y p o l a r t r a n s i t i o n s t a t e despite t h e "anomalous" r e a c t i v i t y s e q u e n c e f r o m p h o s p h i n e s t o p h o s p h i t e s . The a v a i l a b i l i t y o f a w i d e r a n g e o f Ρ(III) compounds f r o m the work w i t h a c t i v a t e d a l k e n e s , w h i c h i s r e l e v a n t t o t h e dimer i s a t i o n of a c r y l o n i t r i l e , f a c i l i t a t e d the determination o f p-values ( T a b l e I I ) f o r a number o f s u b s t r a t e s b y s y s t e m a t i c v a r i a t i o n o f t h e p a r a - s u b s t i t u e n t s i n t h e a r y l g r o u p s on p h o s p h o r u s . The d a t a T a b l e I I R h o - v a l u e s f o r t h e r e a c t i o n o f P ( I I I ) compounds w i t h a variety of substrates a
(°C)
Ρ
Substrate
• Source Ar P
-)c - X (X = C l , B r , I ) CH =CHCN 2
-1.1
2
(30)
-
2
b,c
-1.2
(30)
-2.0
(30)
-1.8 ( 3 0 )
(27)
-0.4
-
b
(37)
b
- 1 . 2 (25)
-1.1 (25)
b
(25)
-3.2
(25)
-3.3
(25)
-3.3
(25)
-2.2 (25)
EtOOEt
-0.4 (28)
-0.3
PhSSSPh
-1.2
(2 5)
-2.5 -3.2
TCNQ
ArP(0R)
Ar P0R
3
a) Maximum e r r o r t h r o u g h o u t ± 1 0 % o f ρ - v a l u e c) r e f . 9 d) r e f . 1 2 .
b,d
(25)
b
b) t h i s w o r k
r e v e a l t h a t a l l t h e r e a c t i o n s a r e a c c e l e r a t e d by e l e c t r o n d o n a t i o n ( i . e . have a n u c l e o p h i l i c component) a n d t h a t t h e r e i s a w i d e range o f s e n s i t i v i t y o f r e a c t i o n r a t e t o t h e e l e c t r o n i c e f f e c t s of s u b s t i t u e n t s a t phosphorus. I t i s also apparent that t h e pv a l u e s a r e v i r t u a l l y i n d e p e n d e n t o f t h e t y p e o f P ( I I I ) compound f o r a g i v e n s u b s t r a t e b u t change w i t h t h e n a t u r e o f t h e s u b s t r a t e . I t seems l i k e l y t h a t t h e m a g n i t u d e o f ρ r e p r e s e n t s t h e " e x t e n t o f e l e c t r o n demand" a t p h o s p h o r u s L i i n t h e T.S. o r i n o t h e r w o r d s i s a measure o f " e l e c t r o n t r a n s f e r " i n t h e T.S., a t e r m (=z) which appears i n t h e semi-empirical equations d e s c r i b i n g t h e n u c l e o p h i l i c r e a c t i v i t y of t r i c o o r d i n a t e d phosphorus.il. This c o n c e p t i s r e i n f o r c e d by ( i ) t h e o b s e r v a t i o n ( f r o m t h e d a t a o f B o k o n o v H and G o e t z u ' u î ) t h a t p - v a l u e s b a s e d o n t h e p K v a l u e s of p r o t o n a t e d phosphines i n c r e a s e w i t h i n c r e a s i n g ρ % , i . e . i n c r e a s e w i t h a s h i f t o f t h e e q u i l i b r i u m (eqn. 4) t o t h e l e f t and a
Quin and Verkade; Phosphorus Chemistry ACS Symposium Series; American Chemical Society: Washington, DC, 1981.
PHOSPHORUS CHEMISTRY
554
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(ii) by the fact that reactions of higher ρ value (eg SQ) show a higher sensitivity to solvent. Literature cited 1. Kosolapoff, G.M. and Maier, L.(eds) "Organic Phosphorus Com pounds", Vols 1 and 4, Wiley Interscience, New York, 1972/73. 2. Emsley, J . and Hall, C.D. "The Chemistry of Phosphorus", Harper and Row, London, 1976. 3. Trippett, S. Specialist Reports, Royal Society of Chemistry, Organophosphorus Chemistry, Vols 1-11, 1969-1979. 4. Davies, W.C. and Lewis, W.P.G. J . Chem. Soc. 1934, 1599. 5. Arbusov, B.A. Pure and Applied Chem. 1964, 1, 307. 6. Aksnes, G. and Aksnes, D. Acta Chem. Scand. 1965, 19, 898. 7. Shaw, M.A. and Ward, R.S. Topics in Phosphorus Chemistry, 1972, Vol 7, p.11. 8. Jarvis, Β.B. and Marien, B.A. J . Org. Chem. 1976, 41, 2182. 9. Borowitz, I . J . ; Firstenberg, S.; Borowitz, G.B. and Schuessler, D. J . Amer. Chem. Soc. 1972, 94, 1623. 10. Denney, D.B. and Jones, D.H. J . Amer. Chem. Soc. 1969, 91, 5821. 11. Denney, D.B.; Denney, D.Z.; Hall, C.D. and Marsi, K.L. J . Amer. Chem. Soc. 1972, 94, 245. 12. Bartlett, P.D. and Meguerian, G. J . Amer. Chem. Soc. 1956, 78, 3710. 13. Feher, F. and Kurz, D. Z. Naturforsch, B. 1968, 23, 1030. 14. Chang, L . L . ; Denney, D.B.; Denney, D.Z. and Kazior, R.J. J. Amer. Chem. Soc. 1977, 99, 2293. 15. Bowman, D.A.; Denney, D.B. and Denney, D.Z. Phosphorus and Sulphur, 1978, 4, 229. 16. Aida, T.; Furukawa, Ν. and Oae, S. Chem. Lett. 1973, 805. 17. Hammond, Ρ. J.; Lloyd, J. R. and Hall, C.D. Phosphorus and Sulphur, 1981 (in press) 18. Beer, P.D.; Edwards, R.C.; Hall, C.D.; Jennings, J.R. and Cozens, R.J. Chem. Comm. 1980, 351. 19. Scott, G.; Hammond, P.J.; Hall, C.D. and Bramblett, J . J. Chem. Soc. Perkin II, 1977, 882. 20. Kosower, E.M. "An Introduction to Physical Organic Chemistry" 1968, J . Wiley, p.54. 21. Hudson, R.F. "Structure and Mechanism in Organophosphorus Chemistry", 1965, Academic Press, Chap. 4. 22. Stepanov, Β . I . ; Bokanov, A.I. and Kovolev, B.A. J. Gen. Chem. USSR (English Ed) 1967, 37, 2029. 23. Goetz, H. and Siegfried, D. Annalen, 1967, 704, 1. 24. Goetz, H. and Sidhu, A. Annalen, 1965, 682, 71. RECEIVED
June 30,
1981.
Quin and Verkade; Phosphorus Chemistry ACS Symposium Series; American Chemical Society: Washington, DC, 1981.
