97 Secondary Phosphino Macrocyclic Ligands EVAN P. KYBA and HEINZ H. HEUMÜLLER
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Department of Chemistry, The University of Texas at Austin, Austin,TX78712
The use of secondary phosphines as ligands for transition metals has led to some interesting complexes (2,3). Our interest in unusual macrocyclic ligand systems led us to the synthesis of the first macrocycles (VI, VII, Scheme 1) which contain secondary -phosphino ligating sites. In order to prepare these macrocycles it was necessary to synthesize the previously unknown o-bis(phosphino)benzene (IV). Lithium aluminum hydride reduction of the o-bis(phosphonate) III gave IV in 50% yield ( P NMR, δ-123.8 ppm, JPH = 207 Hz). The phosphonate III could be obtained in modest yields by the photo -activated nucleophilic aromatic substitution by sodium diethylphosphite on o-chloroiodobenzene in liquid ammonia solution (4). Recently we have developed a more general approach to mole cules exemplified by III. Thus the Diels-Alder cycloaddition of alkyne II and α-pyrone, followed by aromatization by loss of car bon dioxide, led to the isolation of III (72%) (5). Alkyne II was obtained in high yields, in two steps from dichloroacetylene and triethylphosphite via Arbuzov-type reactions (5). Since the intermediate chloroalkyne phosphonate I was isolable (90%), phos phorus nucleophiles other than triethylphosphite could be used to give unsymmetrical alkyne diphosphoryl species. We have demon strated this approach by the reaction of I with Ph2POEt and PhP(OEt) (5). Treatment of II in THF with two equivalents of n-butyllithium generated V, which gave VI and VII upon high dilution reactions (6) in THF with bis(3-methanesulfonyloxypropyl)sulfide and bis(3chloropropyl)methylamine, respectively in yields of about 80%. Both macrocycles were highly air sensitive, colorless, distillable viscous oils, and both were isolated as a mixture of two 3 1
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0097-6156/81/0171-0473$05.00/0 © 1981 American Chemical Society
In Phosphorus Chemistry; Quin, L., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.
Downloaded by UNIV OF LIVERPOOL on December 10, 2015 | http://pubs.acs.org Publication Date: November 11, 1981 | doi: 10.1021/bk-1981-0171.ch097
474 PHOSPHORUS CHEMISTRY
In Phosphorus Chemistry; Quin, L., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.
KYBA AND HEUMULLER
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i s o m e r s . Thus V I i n CeV& e x h i b i t e d two s i n g l e t s i n t h e p r o t o n d e c o u p l e d *P NMR s p e c t r u m a t δ -58.1 a n d -64.0 ppm i n a n a r e a r a t i o o f 62:38, a n d s i m i l a r l y , V I I i n CeD6 g a v e s i n g l e t s a t - 5 5 . 1 and -61.5 ppm ( a r e a r a t i o 6 9 : 3 1 ) . The m a j o r i s o m e r s o f V I a n d V I I show no f l u x i o n a l i t y a t t e m p e r a t u r e s a s l o w a s -90°C i n t o l u e n e s o l u t i o n a s o b s e r v e d b y P NMR s p e c t r o s c o p y . I n c o n t r a s t , t h e m i n o r i s o m e r s e x h i b i t e d c o a l e s c e n c e t e m p e r a t u r e s a t c a . -60°C, a n d w i t h f u r t h e r c o o l i n g , two p e a k s a r o s e ( l o w t e m p e r a t u r e l i m i t i n g ¥ NMR a b s o r p t i o n s a t 6 -70.2 a n d -60.0 ppm) f o r V I a n d t h r e e p e a k s a t δ - 7 4 . 1 , - 5 4 . 6 , a n d -44.5 ppm f o r V I I . Treatment o f a benzene s o l u t i o n o f V I w i t h an excess o f n i c k el c h l o r i d e i n methanol r e s u l t e d i n the p r e c i p i t a t i o n o f a y e l l o w powder. T h i s was r e c r y s t a l l i z e d f r o m m e t h a n o l t o g i v e a i r - s t a b l e y e l l o w - o r a n g e c r y s t a l s (60%) w i t h t h e s t o i c h i o m e t r y (VI) NiCl2·3MeOH ( b y c o m b u s t i o n a n a l y s i s ) . When t h i s r e c r y s t a l l i z e d c o m p l e x was t r e a t e d w i t h e x c e s s aqueous s o d i u m c y a n i d e i n t h e p r e s e n c e o f C6D6 a t room t e m p e r a t u r e f o r 10 m i n V I was r e g e n e r a t e d , b u t now t h e ¥ NMR a b s o r p t i o n s a t δ -58.1 a n d -64.0 ppm w e r e i n a n a r e a r a t i o o f 95:5. S i m i l a r treatment of V I I w i t h n i c k e l c h l o r i d e l e d to a dark o i l y p r e c i p i t a t e which r e q u i r e d c o n s i d e r a b l e manipula tion to partially purify i t . Treatment w i t h sodium c y a n i d e a s above l e d t o t h e r e g e n e r a t i o n o f V I I a l s o e n r i c h e d i n t h e major isomer (85:15). E x a m i n a t i o n o f D r e i d i n g and C o r e y - P a u l i n g - K o l t u n g m o l e c u l a r models r e v e a l s t h a t t h e t r a n s - l i g a n d (b) cannot c h e l a t e a m e t a l i o n w i t h o u t s e v e r e s t e r i c i n t e r a c t i o n s w h i l e t h e c i s - ( a ) c a n do so e a s i l y . The f a c t t h a t t h e n i c k e l ( I I ) c o m p l e x a t i o n - c y a n i d e décomplexâtion s e q u e n c e l e a d s t o e n r i c h m e n t o f t h e m a j o r i s o m e r s of V I and V I I l e a d s us t o p o s t u l a t e t h a t the major isomers a r e t h e c i s - ( a ) s p e c i e s . We h a v e e q u i l i b r a t e d V i a a n d V I b t h e r m a l l y t o a r a t i o o f 58:42; t h u s t h e m a c r o c y c l i z a t i o n g i v e s a n o n - e q u i l i b r i u m m i x t u r e f a v o r i n g t h e c i s i s o m e r , a n a l o g o u s t o P P h a n d AsMe m a c r o c y c l i z a t i o n s t h a t we h a v e d e s c r i b e d r e c e n t l y (1,7_, 8) . 3
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Acknowledgement. We a r e most g r a t e f u l t o t h e A i r F o r c e O f f i c e o f S c i e n t i f i c R e s e a r c h (AFOSR-79-0090) a n d t h e R o b e r t A. W e l c h F o u n d a t i o n ( F 573) f o r g e n e r o u s s u p p o r t o f t h i s work.
Literature Cited. 1.
2.
For the previous paper in the series, Phosphino-macrocycles, see Kyba, E.P.; Davis, R.E.; Hudson, C.W.; John, A.M.; Brown, S.B.; McPhaul, M.J.; Liu, L.-L.; Glover, A.C. J . Am. Chem. Soc. 1981, 103, 0000. Stelter, O. in "Topics in Phosphorus Chemistry", Volume 9, Griffith, E . J . and Grayson, Μ., Editors, Wiley Interscience, New York, 1972, p. 433.
In Phosphorus Chemistry; Quin, L., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.
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3. 4. 5.
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6. 7. 8.
Booth, G. in "Organic Phosphorus Compounds", Volume 1, Kosolapoff, G.M. and Maier, L . , Editors, Wiley Interscience, New York, 1972, p. 433. Bard, R.R.; Bunnett, J . F . ; Traber, R.P. J . Org. Chem. 1979, 44, 4918. Kyba, E.P.; Rines, S.P.; Owens, P.O.; Chou, S.-S.P.; Tetra hedron Lett. 1981, 22, 1875. Kyba, E.P.; Chou, S.-S.P. J . Org. Chem. 1981, 46, 860. Kyba, E.P.; John, A.M.; Brown, S.B.; Hudson, C.W.; McPhaul, M.J.; Harding, A.; Larsen, K.; Niedzwiecki, S.; Davis, R.E. J . Am. Chem. Soc. 1980, 102, 139. Kyba, E.P.; Chou, S.-S.P. J . Am. Chem. Soc. 1980, 102, 7012.
RECEIVED
June 30, 1981.
In Phosphorus Chemistry; Quin, L., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.
