54 Recent Results on Open-Chain and Cyclic Phosphanes and Organylphosphanes
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MARIANNE BAUDLER Institut für Anorganische Chemie der Universität Köln, Greinstrasse 6, D-5000 Köln 41, FRG
Compounds containing a skeleton of cumulated P-P bonds have been rare until recently, as they are in general highly reactive. This means that they can easily be oxidized and have a strong tendency to disproportionate. Nevertheless, considerable progress has been achieved in this field lately. Thereby a significant analogy of phosphorus- to carbon-chemistry became apparent with respect to structural features. Phosphorus Hydrides Since 1965 we have found an unexpected number of binary phos phorus hydrogen compounds in addition to the well-known hydrides PH and P H (Table I). These phosphanes have been detected in the hydrolysis products of calcium phosphide or in the thermolysis products of P H (1,2) by mass spectroscopy. Only the compounds Ρ H , P H , Ρ H , and P H could be isolated in pure form so far, whereas the other phosphanes have been obtained only as mixtures. As the detailed structures are mostly unknown, a P-NMRspectro scopic investigation was initiated. Beginning with tetraphosphane(6), the structural situation of the open-chain phosphanes becomes more and more complex due to the existence of constitu tional and configurational isomers. The low temperature P{ H}3
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NMR s p e c t r u m o f Ρ Η c o u l d b e s i m u l a t e d v e r y s a t i s f a c t o r i l y b y t h e 4 6 s u p e r p o s i t i o n o f two A A B B ' - s p i n s y s t e m s f o r t h e d,1- a n d mesoisomer o f n-P^H a n d o n e AB s p i n s y s t e m f o r i - P ^ H ^ w i t h a b r a n c h ed P - s k e l e t o n (3). I n a s i m x l a r way t h e f o u r NMR s p e c t r o s c o p i c a l l y d i s t i n g u i s h a b l e i s o m e r s o f pentaphosphane(7) have been i d e n t i f i e d . The b r a n c h e d i - P ^ H ^ shows t h e h i g h e s t r e l a t i v e f r e q u e n c y . The c h e m i s t r y o f t h e h i g h e r h o m o l o g u e s o f PH^ was u n t i l t h e p r e s e n t a l m o s t unknown. We h a v e t h e r e f o r e i n v e s t i g a t e d f i r s t t h e m e t a l l a t i o n o f d i p h o s p h a n e (5). The r e a c t i o n o f P^H^ w i t h n - B u L i or L i P H y i e l d s the polyphosphide L i ^ P · 3 s o l v e n t s ^ a s t h e f i n a l product. A s i g n i f i c a n t feature o f the t r i c y c l i c P ion i s i t s f l u c t i o n a l behavior which i s analogous t o t h a t i n bu||valene, a s f o u n d b y s t u d y i n g t h e t e m p e r a t u r e d e p e n d e n c e o f t h e P-NMR s p e c 1
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0097-6156/81/0171-0261$05.00/0 © 1981 American Chemical Society In Phosphorus Chemistry; Quin, Louis D., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.
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