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The Perfluoropinacolyl Group: A Stabilizing Substituent for Unusual Phosphites and Phosphoranes GERD-VOLKER RÖSCHENTHALER, and RAINER BOHLEN Fachbereich 3 der Universität, 28 Bremen 33, FRG WERNER STORZER Lehrstuhl Β für Anorganische Chemie der Technischen Universität, 33 Braunschweig, FRG
The perfluoropinacolyl moietyOC(CF3)2C(CF3)2Ostabilizes higher valence states of main group elements (1) because of its high group electronegativity and bidentate character. The inves tigations of Ramirez, Trippett, and Knunyants show that pentacovalent phosphorus compounds containing this grouping are readi ly obtained by oxidative cyclisation reacting phosphorus(III) compounds with hexafluoroacetone. We were successful in synthe sizing fluorophosphoranes in a similar manner (2, 3):
Two fluorines attached to phosphorus instead of the perfluoro pinacolyl moiety would cause rapid decomposition. These findings prompted us to try the synthesis of phosphites, cyclic and bicyclic phosphoranes by a step by step procedure using dilithium perfluoropinacolate 1 and phosphorus halogenides as starting materials:
0097-6156/81/0171-0443$05.00/0 © 1981 American Chemical Society Quin and Verkade; Phosphorus Chemistry ACS Symposium Series; American Chemical Society: Washington, DC, 1981.
PHOSPHORUS CHEMISTRY
444
The chlorophosphite 3 is a precursor f o r s e v e r a l s u b s t i tution r e a c t i o n s y i e l d i n g s u r p r i s i n g l y s t a b l e phosphorus(III) compounds (Scheme 1):
Scheme 1 The phosphites 3 and 4 are o x i d i z e d by c h l o r i n e and bromine to f u r n i s h s t a b l e covalent phosphoranes. No Arbuzov r e a c t i o n was observed. The trichlorophosphorane 5 can be reacted w i t h 1 again to form a spirophosphorane 7 which is hydrolyzed without r i n g cleavage to g i v e an extremely s t a b l e hydroxyphosphorane or a phosphoraneoxide a n i o n :
Quin and Verkade; Phosphorus Chemistry ACS Symposium Series; American Chemical Society: Washington, DC, 1981.
91.
ROSCHENTHALER
E TAL.
The Perfluoropinacolyl
445
Group
Aminophosphites are t r a n s f e r r e d t o aminospirophosphoranes v i a a s i m i l a r r e a c t i o n route: 1 C F) 3'2
ClR
2
N
\ ~>(CF ) Q
Cl •R N-P| 2
3
!
0
(CF
2
9 X c F3J' 2
_
-2LiCI
0y ^ X
{C
3 2
1CF )
/Ci )2
[/O
2
\ Q
>(CF )
0
3
1CF )
]
32
3
2
2
A n i t r o g e n - b r i d g e d d i p h o s p h o r a n e i s o b t a i n e d by r e a c t i n g t h e p h o s p h i t e p r e c u r s o r w i t h c h l o r i n e . The d i p h o s p h o r a n e decomposes s l o w l y t o form 5 and a d i a z a d i p h o s p h e t i d i n e .
|. Me
Cl Cl I/CICI\I ,0-P. .P-0 ^ I ^ N ^ I >(CF )
ci,
(CF )2< ;/ V/ 3)2 0
3
(CF ^ 3
XN
CF
HF ) 3
3
(Cr ) 3
Me
32 ;
2
2
r
O
X
p
/
(CF ) 3
2
2
Me I Cl i NN> i / • Ο ΙΟ F,) 3'2 X
i
y i ^ N (CFo) 3'2 Cl 1 Me 7
3
V
0-i(CF ) 3
2
3
2
A v e r y i n t e r e s t i n g c h e m i s t r y d e v e l o p s from t h e aminop h o s p h i t e J3 h a v i n g a H^N g r o u p bonded t o p h o s p h o r u s , t h e f i r s t s t a b l e species o f that type, which i s synthesized by r e a c t i n g 3^ w i t h l i t h i u m a m i d e . Compound e a s i l y adds h y d r o g e n f l u o r i d e to form a aminofluorohydridophosphorane. C h l o r i n e y i e l d s a d i c h l o r o p h o s p h o r a n e _9 w h i c h decomposes upon h e a t i n g t o g i v e a c y c l i c p h o s p h a z e n e . S u b s t i t u t i o n o f t h e two c h l o r i n e s i n compound 9_ b y t h e p e r f l u o r o p i n a c o l y l g r o u p i n g y i e l d s a a m i n o s p i r o s y s t e m . Two r e m a r k a b l e compounds a r e f o u n d d u r i n g t h e r e a c t i o n o f 8^ w i t h ammonium p e r f l u o r o p i n a c o l a t e a n d h e x a f l u o r o a c e t o n e . I n t h e f i r s t case a hydridospirophosphorane, i n t h e l a t t e r a phosphorane c o n t a i n i n g a f o u r a n d f i v e membered r i n g c a n be i s o l a t e d ( S c h e m e 2).
Quin and Verkade; Phosphorus Chemistry ACS Symposium Series; American Chemical Society: Washington, DC, 1981.
PHOSPHORUS
446
CHEMISTRY
Scheme 2 Deutsche Forschungsgemeinschaft i s thanked f o r f i n a n c i a l support, Professor Schmutzler f o r access t o research f a c i l i t i e s , and D a i k i n Company, O s a k a , J a p a n f o r t h e g e n e r o u s g i f t o f h e x a fluoroacetone.
1. 2. 3.
Allen, M.; Janzen, A. F . ; Willis, C. J . Can. J . Chem. 1968, 46, 3671. Gibson, J . Α.; Röschenthaler, G.-V.; Schmutzler, R. J . Chem. Soc. Dalton Trans. 1975, 918. Röschenthaler, G.-V.; Gibson, J . Α.; Schmutzler, R. Chem. Ber. 1977, 110, 611.
RECEIVED
June 30, 1981.
Quin and Verkade; Phosphorus Chemistry ACS Symposium Series; American Chemical Society: Washington, DC, 1981.
