METAL-ORGANIC COMPOUNDS

Molybdenum

Chelates,

Esters,

and

Organometallics

1

JOHN G. DEAN, HERBERT KAY, and MELVIN L. LARSON

Downloaded by MONASH UNIV on March 1, 2016 | http://pubs.acs.org Publication Date: January 1, 1959 | doi: 10.1021/ba-1959-0023.ch033

Climax Molybdenum Co., 500 Fifth Ave., New York 36, Ν. Y.

Molybdenum, a transition element, displays multiple valence states and a great complexing tendency. Molybdenum chelates, esters, and organometallics are the important industrial compounds. Chelates are formed with nitrogen, sulfur, and oxygen linkages. Esters are derivatives of molybdic acid with alcohols, phenols, or hydroxy acids. The organometallic com pounds comprise alkyl and aryl derivatives as well as complexes with carbonyls, cyanides, olefins, and acet ylenes. The preparation and physical properties of some of these compounds are indicated.

Molybd

e n u m h a s s h a r e d i n t h e renascence of i n t e r e s t i n m e t a l s c h e m i s t r y w h i c h w a s s p a r k e d b y u r a n i u m a t t h e s t a r t of W o r l d W a r I I . M o l y b d e n u m ' s o t h e r congeners of s u b g r o u p s V I of t h e P e r i o d i c C h a r t , c h r o m i u m a n d t u n g s t e n , h a v e s i m i l a r l y p r o v e d t o be h e a v y m e t a l s w i t h a n u n u s u a l c h e m i s t r y . A l t h o u g h o v e r 9 0 % of t h e m o l y b d e n u m p r o d u c e d i s c o n s u m e d i n m e t a l l u r g i c a l a p p l i c a t i o n s of i n c r e a s i n g i m p o r t a n c e , a n i n d u s t r i a l c h e m i c a l t e c h n o l o g y i s also t a k i n g s h a p e w i t h t h e e x p a n d i n g use of m o l y b d e n u m i n c a t a l y s t s , colors, a n d l u b r i c a n t s . M o l y b d e n u m , w i t h v a l e n c e states of 0, 2, 3, 4, 5, a n d 6, i s a t r a n s i t i o n e l e m e n t c a p a b l e of f o r m i n g m a n y s t a b l e c o m p o u n d s . I t also h a s e n o r m o u s c o m p l e x i n g p o w e r , e s p e c i a l l y i n t h e h i g h e r v a l e n c e s . T h e c o m b i n a t i o n of s e v e r a l v a l e n c e p o s s i b i l i t i e s a n d u n u s u a l c o m p l e x i n g c a p a c i t y leads t o a g r e a t v a r i e t y of possible o r g a n i c a n d i n o r g a n i c derivatives. T h e c h e m i s t r y of m o l y b d e n u m , w h e t h e r i t i s i n t h e field of i n o r g a n i c s o r o r g a n i c s , is e x c e e d i n g l y c o m p l i c a t e d . T h e c o m p l i c a t i o n s h a v e b e e n c o m p o u n d e d b y i n a c c u r a c i e s i n d a t a a n d the related interpretations to be found i n t h e early l i t e r a t u r e . T h e vast progress i n s t r u c t u r a l c h e m i s t r y i s , h o w e v e r , r a p i d l y p o i n t i n g t h e w a y f o r g e n e r a l understanding a n d agreement. I n s p i t e of t h e c o m p l i c a t i o n s of m o l y b d e n u m c h e m i s t r y , a t least one l a r g e class of m o l y b d e n u m organics—the chelates—is familiar to the industrial chemist. M o l y b d e n u m c o m p o u n d s of t h i s t y p e a r e w i d e l y u s e d f o r t h e p r e p a r a t i o n of b r i l l i a n t o r g a n i c p i g m e n t s , a n a p p l i c a t i o n w h i c h consumes a b o u t 450,000 p o u n d s of m o l y b d e n u m a y e a r . M o l y b d e n u m chelates a r e t r e a t e d first i n t h i s p a p e r , because of t h e i r firm p o s i t i o n i n industrial chemistry. M o l y b d e n u m esters h a v e been e x t e n s i v e l y discussed, p a r t i c u l a r l y i n t h e o l d e r l i t e r a t u r e . A l t h o u g h t h e y do n o t a t p r e s e n t receive a n y k n o w n c o m m e r c i a l a p p l i c a t i o n s , t h e y a r e discussed as t h e second i m p o r t a n t class of o r g a n o m o l y b d e n u m , 1

Present address, Stewart L a n e , Wilton,

Conn.

357

In METAL-ORGANIC COMPOUNDS; Advances in Chemistry; American Chemical Society: Washington, DC, 1959.

ADVANCES IN CHEMISTRY SERIES

358

M o l y b d e n u m c o m p o u n d s w h i c h b e l o n g t o t h e o r g a n o m e t a l l i c class, a t least i n t h e b r o a d e r sense of t h i s t e r m , h a v e been i n t e n s i v e l y s t u d i e d i n recent y e a r s . A l t h o u g h m o l y b d e n u m , l i k e m a n y of the o t h e r t r a n s i t i o n m e t a l s , does n o t r e a d i l y f o r m t r u e a l k y l a n d a r y l d e r i v a t i v e s , i t does f o r m a series o f c o m p o u n d s w h i c h c a n best b e d e s c r i b e d as s u b s t i t u t e d c a r b o n y l s . B e c a u s e of t h e i r g r e a t i n t e r e s t i n f u n d a m e n t a l c h e m i s t r y a n d t h e i r p o t e n t i a l i t i e s f o r i n d u s t r i a l u t i l i z a t i o n , t h i s g r o u p o f c o m p o u n d s is discussed a t some l e n g t h i n t h e f i n a l section of t h i s p a p e r . O n e reason f o r t h e i n c r e a s e d t e m p o o f r e s e a r c h a n d d e v e l o p m e n t w o r k o n m o l y b d e n u m c h e m i c a l s is t h a t a w i d e r v a r i e t y o f m o l y b d e n u m c o m p o u n d s s u i t a b l e as r e s e a r c h reagents h a s been p r e p a r e d . M o l y b d e n u m c a r b o n y 1, t h e p e n t a c h l o r i d e a n d o t h e r h a l i d e s , a n d a v a r i e t y of soluble i s o p o l y a n d h e t e r o p o l y salts h a v e r e c e n t l y been a d d e d t o t h e sulfide, o x i d e , a n d s i m p l e m o l y b d a t e s as m a t e r i a l s a v a i l a b l e for r e s e a r c h p u r p o s e s .


Molybdenum Chelates M o l y b d e n u m chelate c o m p o u n d s consist of c o m p l e x e s w i t h M o — Ν — C , M o — S — C , and M o — Ο — C linkages. M o s t of the k n o w n compounds are complex molybdate a n i o n s p r o b a b l y f o r m e d b y chelate c o o r d i n a t i o n w i t h p o l y b a s i c acids a n d p o l y h y d r o x y compounds like oxalic acid, phthalic acid, salicylic acid, a n d catechol. O f the m a n y chelate c o m p o u n d s w h i c h h a v e been s a t i s f a c t o r i l y c h a r a c t e r i z e d w i t h d i s t i n c t i v e p r o p erties, those i n v o l v i n g M o — Ν — C b o n d i n g h a v e e v o k e d t h e greatest c o m m e r c i a l i n t e r est t h u s f a r . Molybdenum-Nitrogen-Carbon System. P e r h a p s the best k n o w n o f these M o — Ν — C c o m p l e x e s are those used i n the m a n u f a c t u r e of o r g a n i c p i g m e n t s f o r t h e p r i n t i n g i n k i n d u s t r y . B a s i c dyestuffs s u c h as m e t h y l v i o l e t , V i c t o r i a p u r e b l u e , B r i l l i a n t G r e e n , R h o d a m i n e 6 G , a n d Thioflavine Τ are precipitated b y phosphomolybdic a c i d t o give t h e P M A colors, a n d b y p h o s p h o t u n g s t o m o l y b d i c a c i d t o g i v e t h e P M T A colors (40). A g o o d e x a m p l e o f a p h o s p h o m o l y b d a t e t o n e r o r c o l o r l a k e i s s h o w n b y t h e sug gested c h e m i c a l f o r m u l a f o r the c o m p l e x w i t h m e t h y l v i o l e t :

NHMe T h e s e o r g a n i c p i g m e n t s a r e c h a r a c t e r i z e d b y b r i l l i a n c e , s t r e n g t h , a n d resistance t o light, heat, a n d water. T h e s t r u c t u r e o f t h e P M A colors i s v e r y s i m i l a r t o t h a t o f t h e s t a r t i n g dyestuffs, m o s t o f w h i c h exist as salts, u s u a l l y c h l o r i d e s o r sulfates. T h e f o r m a t i o n o f a P M A c o l o r i s s i m p l y t h e r e p l a c e m e n t , i n s o l u t i o n , o f a l i g h t w e i g h t anion* b y a m u c h h e a v i e r one, t h u s c a u s i n g p r e c i p i t a t i o n . T h e p h o s p h o m o l y b d a t e a n i o n c a n r e p l a c e a h a l i d e a n i o n i n o n e o f t h e d y e s t u f f s ; a p p r o x i m a t e l y six o r s e v e n m o l e c u l e s o f d y e a r e r e q u i r e d f o r each m o l e c u l e of p h o s p h o m o l y b d i c a c i d used (40). P M A colors a r e m a n u f a c t u r e d b y a t h r e e - s t e p p r o c e s s : s o l u t i o n o f t h e dyestuff i n water a t controlled p H a n d t e m p e r a t u r e ; p r e p a r a t i o n of the complex acid solution f r o m s o l u b l e p h o s p h a t e a n d m o l y b d a t e salts w i t h t h e a d d i t i o n o f m i n e r a l a c i d t o b r i n g t h e p H w i t h i n t h e r a n g e o f 3 t o 4 a t a t e m p e r a t u r e of 20° t o 3 0 ° C ; a n d a d d i t i o n o f t h e c o m p l e x a c i d s o l u t i o n t o t h e dyestuff s o l u t i o n a t a c o n t r o l l e d r a t e a n d w i t h c o n trolled agitation. T h e precipitated pigment is then stabilized b y heating, followed b y a f i n a l t r e a t m e n t w i t h excess o f t h e c o m p l e x a c i d (40). P r o d u c t i o n o f P M A a n d P M T A colors as o r g a n i c p i g m e n t s represents t h e m o s t i m p o r t a n t single u s e f o r m o l y b d e n u m c o m p o u n d s . A n n u a l w o r l d c o n s u m p t i o n of


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359

m o l y b d e n u m i n t h i s a p p l i c a t i o n t o t a l s 450,000 p o u n d s , w i t h t h e p r i n t i n g i n k i n d u s t r y a c c o u n t i n g f o r a p r e d o m i n a n t p o r t i o n o f t h i s m a r k e t . O t h e r areas w here these b r i l l i a n t colors find a p p l i c a t i o n are i n t h e t i n t i n g a n d s h a d i n g o f w h i t e p a p e r t o offset t h e y e l lowness o f n a t u r a l p a p e r s t o c k , i n t h e m a n u f a c t u r e of c o l o r e d p a p e r , a n d i n w a t e r colors a n d enamels f o r c h i l d r e n ' s t o y s . T


O t h e r v i v i d colors m i g h t b e p r o d u c e d f r o m h e t e r o p o l y a c i d s a n d v a r i o u s basic o r g a n i c d y e s . A m o n g l i k e l y s t a r t i n g m a t e r i a l s f o r n e w o r g a n i c p i g m e n t s are s i l i c o m o l y b d i c a c i d s w i t h a m o l y b d e n u m - s i l i c o n a t o m i c r a t i o of 12 t o 1, a n d p h o s p h o m o l y b d i c a c i d w i t h a m o l y b d e n u m - p h o s p h o r u s r a t i o of 18 t o 2, b o t h a v a i l a b l e as t h e s o d i u m salts. T h e r e are i n n u m e r a b l e o t h e r p o s s i b i l i t i e s , because a t least 2 5 different elements f u n c t i o n as h e t e r o a t o m s i n d i s t i n c t h e t e r o p o l y m o l y b d a t e a n i o n s (5). A n y one o f these h i g h - w e i g h t a n i o n s is a p o t e n t i a l p r e c i p i t a t i n g agent f o r basic o r g a n i c d y e s t o g i v e newcolor lakes a n d toners. V a l u a b l e dyes w i t h g r e a t a f f i n i t y f o r n a t u r a l o r a r t i f i c i a l t e x t i l e fibers, p a r t i c u l a r l y casein, c a n b e p r o d u c e d f r o m m o l y b d e n u m oxide a n d t h e t e t r a s u l f o n i c d e r i v a t i v e s o f p h t h a l o c y a n i n e dyes, o r b y t h e r e a c t i o n o f t h e m o n o s u l f o n i c d e r i v a t i v e o f a n a r o m a t i c c o m p o u n d s u c h as p h t h a l i c a n h y d r i d e w i t h t h e m e t a l l i c oxide i n t h e presence o f u r e a (27). M e t a l l i z e d d i a z o dyes f o r a n i m a l fibers h a v e also been m a d e t h r o u g h t h e c h e l a t i n g a c t i o n of m o l y b d e n u m . T h e s e p r o d u c t s , d a r k - c o l o r e d p o w d e r s o f v a r i e d shades o f b r o w n , are w a t e r - s o l u b l e (8). r

S o l u t i o n s o f m o l y b d a t e s h a v e also b e e n f o u n d t o g i v e a s t r o n g , y e l l o w p r e c i p i t a t e w i t h a s a l i c y l h y d r o x a m i c a c i d ; t h e p r o d u c t dissolves r e a d i l y i n a l c o h o l . T h i s c o l o r e d complex possibly contains quinquevalent m o l y b d e n u m i n t h e anion, the probable f o r m u l a f o r w h i c h is M o 0 C H 0 N . S i m i l a r colorations have been observed w i t h b e n z y h y d r o x a m i c a c i d . T h e s e colors h a v e been suggested as tools f o r t h e c o l o r i m e t r i c e s t i m a t i o n o f v a n a d i u m i n t h e presence of m o l y b d e n u m a n d u r a n i u m (2). O t h e r c o m p l e x e s i n t h e M o — Ν — C s y s t e m a r e those f o r m e d b y m o l y b d e n u m hexacarbonyl or molybdenum pentachloride, and pyridine. Satisfactory characteriza t i o n of t h e sexivalent coordination s u b s t i t u t i o n derivatives of m o l y b d e n u m h e x a c a r b o n y l h a s been a c c o m p l i s h e d b y H i e b e r o n t h e f o l l o w i n g c o m p o u n d s , w h i c h h e s y n t h e s i z e d (14)2

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M o ( C O ) - 3 pyridine M o ( C O * · o-phenanthroline M o ( C O ) - p y r i d i n e , o-phenanthroline 3

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A l t h o u g h m e r c a p t a n s d i d n o t react w i t h m o l y b d e n u m h e x a c a r b o n y l t o f o r m a sulfur-bonded derivative, thiophenol reacted w i t h m o l y b d e n u m t r i c a r b o n y l p y r i d i n e t o f o r m m o l y b d e n u m d i c a r b o n y l t h i o p h e n a t e p y r i d i n e (IS). Molybdenum-Oxygen-Carbon System. O n l y o n e g r o u p of c o m p o u n d s c o n t a i n i n g t h e m o l y b d a t e a n i o n n u c l e u s — t h a t of t h e c o m p l e x e s w i t h o x a l i c a c i d — h a s b e e n s y s t e m a t i c a l l y s t u d i e d . T h e o x a l a t e d e r i v a t i v e s of m o l y b d e n u m ( V I ) are m o s t e a s i l y p r e p a r e d b y d i s s o l v i n g m o l y b d i c o x i d e i n a n aqueous s o l u t i o n o f a n o x a l a t e (20). T h e equimolar complex, H + [ M o 0 ( C 0 ) ] ~ , can undergo photochemical autoreductionoxidation i n a i r w i t h f o r m a t i o n of m o l y b d e n u m blue, a m o l y b d e n u m oxide h y d r a t e of valence intermediate between m o l y b d e n u m ( V ) a n d m o l y b d e n u m ( V I ) . I n a n early G e r m a n p a t e n t , a p h o t o g r a p h i c a p p l i c a t i o n of t h i s p h o t o c h e m i c a l r e a c t i v i t y of t h e o x a l a t e is d e s c r i b e d (19). A l k a l i a n d a m m o n i u m salts o f t h i s c o m p l e x a p p e a r t o be m o r e stable f o r m s t h a n t h e a c i d . T h e o x a l a t e d e r i v a t i v e s o f m o l y b d e n u m ( V ) are stable i n a i r . P r e p a r e d b y t h e r e d u c t i o n o f a n aqueous s o l u t i o n o f a m m o n i u m m o l y b d a t e a n d t h e o x a l a t e salt (1), these are r e d c r y s t a l l i n e c o m p l e x e s t o w h i c h the f o l l o w i n g s t r u c t u r e has been a s s i g n e d : M + [ M o 0 ( C 0 ) ] - ( M + = H + , K + , N H + , y B a + , pyridinium). T h e r e a c t i o n of e l e c t r o l y t i c a l l y f o r m e d m o l y b d e n u m t r i h y d r o x i d e w i t h o x a l i c a c i d i n t h e absence of a i r i s r e p o r t e d t o f o r m m o l y b d e n u m ( I I I ) oxalates (38). W h e n h e a t e d i n a i r , these c o m p o u n d s d e c o m p o s e t o oxalates of i s o p o l y m o l y b d i c a c i d s . Some 2

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less w e l l c h a r a c t e r i z e d m o l y b d e n u m ( I I I ) d e r i v a t i v e s o f s o d i u m s a l i c y l a t e a n d d i s o d i u m phthalate have been prepared b y reaction w i t h M M o C l o r M M o C l (M+ = NH +, K + ) {If). S y n t h e s e s o f p o o r l y c h a r a c t e r i z e d m o l y b d a t e c o m p l e x e s f r o m o - h y d r o x y p h e n o l s , s u c h as c a t e c h o l , o r p y r o g a l l o l (10), h a v e been r e p o r t e d . T h e c a t e c h o l d e r i v a t i v e s o f a m m o n i u m d i t h i o m o l y b d a t e h a v e also b e e n d e s c r i b e d (11).


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6

4

A m i n o - a n d h y d r o x y - s u b s t i t u t e d a r o m a t i c c o m p o u n d s f o r m c o m p l e x e s w i t h soluble m o l y b d a t e s t o y i e l d p e r m a n e n t r e d - b r o w n colors i n d y e i n g a n i m a l fibers. T h e d y e i n g process is c a r r i e d o u t b y s o a k i n g f u r fibers i n a 4 % a q u e o u s s o l u t i o n o f p y r o g a l l o l , f o l l o w e d b y a s e c o n d s o a k i n g i n a n a m m o n i a c a l s o l u t i o n o f m o l y b d i c a c i d (18). S p i r i t or o i l varnishes are converted t o stains i n a like m a n n e r . A n e w m e t a l c o a t i n g process i n w h i c h a s o l u b l e p h o s p h a t e a n d a c o m p l e x b e t w e e n a s o l u b l e m o l y b d a t e a n d a p o l y h y d r i c p h e n o l a r e t h e f e a t u r e d i n g r e d i e n t s has b e e n a p p l i e d c o m m e r c i a l l y . U s e d t o p r e t r e a t i r o n a n d steel p a r t s p r i o r t o p a i n t i n g o r finishing i n s o m e o t h e r m a n n e r , i t p r e v e n t s c r a c k i n g a n d flaking o f t h e f i n i s h i f t h e p a r t m u s t b e f a b r i c a t e d a f t e r p a i n t i n g . T h i s r e s u l t i s a t t r i b u t e d t o a dense a n d a m o r p h o u s p h o s p h a t e c o a t i n g w h i c h w i l l w i t h s t a n d c o n s i d e r a b l e w o r k i n g (82). Q u e b r a c h o i s t h e m o s t c o m m o n l y u s e d p o l y h y d r i c p h e n o l i n t h i s c o a t i n g process, b u t sumac t a n n i n , catechol, resorcinol, hydroquinone, pyrogallol, pyrogallic acid, gallic a c i d , a n d p h l o r o g l u c i n o l h a v e also b e e n u s e d (9). C o a t i n g s o l u t i o n s c o n t a i n i n g 2 ounces o f t h e c o m p l e x m i x t u r e s p e r g a l l o n p r o d u c e h a r d , c o n t i n u o u s p h o s p h a t e c o a t ings a v e r a g i n g 100 m g . p e r s q u a r e foot of f e r r o u s m e t a l s u r f a c e . T h e c h a r a c t e r i z a t i o n o f c o v a l e n t chelate d e r i v a t i v e s has been l i m i t e d t o m o l y b d e n u m acetylacetonates. Y e l l o w , s o l i d m o l y b d e n u m ( V I ) a c e t y l a c e t o n a t e has been p r e p a r e d b y a c o n d e n s a t i o n r e a c t i o n o f a c e t y l a c e t o n e w i t h m o l y b d i c o x i d e (26). T h i s compound must be isolated a t reduced temperatures i n order t o prevent decomposition t o m o l y b d e n u m b l u e (25). U s i n g W a r d l a w ' s m o l y b d e n y l m o n o c h l o r i d e h y d r a t e (89), M o r g a n p r e p a r e d a water-soluble m o l y b d e n u m ( I I I ) acetylacetonate, w h i c h was r e a d i l y a i r - o x i d i z e d t o a green m o l y b d e n u m ( V ) a c e t y l a c e t o n a t e , s o l u b l e i n b o t h w a t e r a n d o r g a n i c s o l v e n t s . D a t a have recently been obtained f o r a complex w i t h ethylenediamine tetraacetate. T h e r e are two m o l y b d e n u m atoms per l i g a n d of ethylenediamine tetraacetate, a s t r u c t u r e w h i c h a p p e a r s u n i q u e a m o n g s u c h c o m p l e x e s (28). O t h e r c o m p o u n d s , p r e s u m a b l y chelates, a r e t h e b e n z o i n o x i m e a n d 8 - q u i n o l i n o l c o m p l e x e s w h i c h a r e u s e d f o r p r e c i p i t a t i o n o f m o l y b d e n u m f r o m aqueous a c i d molybdate solutions. M o l y b d e n u m a n d a c e t y l - o r b e n z o y l a c e t o n e are c l a i m e d t o f o r m c o l o r e d chelates, w h i c h , w h e n added t o a m o n o m e r i n a p o l y m e r i z a t i o n system, give colored p o l y m e r s (6). Molybdenum-Sulfur-Carbon System. B e c a u s e M o — S b o n d s are less i o n i c t h a n M o — Ο b o n d s a n d s u l f u r has a g r e a t e r c o v a l e n t c o o r d i n a t i n g t e n d e n c y t h a n o x y g e n , organic sulfur complexes of m o l y b d e n u m should be more soluble i n organic m e d i a a n d less r e a c t i v e t o w a r d tpie c o m m o n i o n i z e d reagents. M a l a t e s t a has carried o u t a systematic study of m o l y b d e n u m xanthates a n d d i t h i o c a r b a m a t e s (24), b o t h o f w h i c h are p r o b a b l y s t a b i l i z e d b y t h e f o l l o w i n g basic chelate g r o u p : S

/

\

II—O—S—Mo R = a l k o x y or d i a l k y l a m i n o T h e s e c o m p o u n d s a r e p r e p a r e d b y r e d u c t i o n o f a n aqueous s o l u t i o n o f t h e m o l y b d a t e a n d t h e a l k a l i m e t a l s a l t o f t h e d i t h i o a c i d . R e c e n t w o r k has d e m o n s t r a t e d t h a t o n l y t h e m o l y b d e n u m ( V ) i o n f o r m s t h e x a n t h a t e (29). T h e s e c o m p o u n d s are soluble i n organic solvents, insoluble i n water, a n d undergo oxidative decomposition u p o n s t a n d i n g . T h e d i a l k y l d i t h i o e a r b a m a t e s are s i m i l a r i n s t r u c t u r e t o t h e x a n t h a t e s , b u t a r e less



361

w e l l defined, because o f tendencies t o u n d e r g o p o l y m e r i z a t i o n . T h e y a r e m o r e stable t h a n t h e x a n t h a t e s a n d less soluble i n o r g a n i c s o l v e n t s . T h e u s e o f n a t u r a l m o l y b d e n u m d i s u l f i d e as a s o l i d film l u b r i c a n t a d d i t i v e t o chassis greases has b e e n d e s c r i b e d (36). O t h e r l u b r i c a t i n g a p p l i c a t i o n s i n t h e a u t o m o t i v e field a w a i t t h e d e v e l o p m e n t o f s t a b l e d i s p e r s i o n s o f m o l y b d e n u m disulfide i n o i l m e d i a . One a p p r o a c h t o this p r o b l e m has been t o synthesize oil-soluble m o l y b d e n u m s u l f u r o r g a n i c c o m p o u n d s w h i c h a p p e a r t o d e c o m p o s e as t h e f r i c t i o n - i n d u c e d t e m p e r a t u r e increases. A m o l y b d e n u m sulfide film i s r e p o r t e d t o b e c o n t i n u o u s l y d e p o s i t e d o n t h e m e t a l surfaces. S u c h o r g a n i c c o m p o u n d s c o u l d b e a d d e d t o e x t r e m e - p r e s s u r e a n d h y p o i d gear oils t o i m p r o v e l u b r i c i t y a n d t o p r e v e n t m e t a l - t o - m e t a l c o n t a c t a t f r i c t i o n interfaces.


H u g e l h a s r e p o r t e d t h e seizing t i m e s f o r v a r y i n g a p p l i e d l o a d s o n a 4 - b a l l t e s t i n g m a c h i n e , u s i n g a n S A E 3 0 o i l w i t h 2 % of a m o l y b d e n u m d e c y l x a n t h a t e a d d e d . This d e c y l x a n t h a t e is of t h e g e n e r a l f o r m u l a :

RO-C—S ι

0.

v

\

S—C—OR

/ \ / Mo—0—Mo

\

R O - C — ^ S — C — O R II II S S where R m a y be h e x y l , octyl, decyl, o r dodecyl. O f these c o m p o u n d s , t h e d e c y l x a n t h a t e w a s f o u n d t o h a v e o p t i m u m s o l u b i l i t y a n d s t a b i l i t y (16). H u g e l ' s d a t a i n d i c a t e t h a t t h i s c o m p o u n d as a l u b r i c a n t a d d i t i v e p r e v e n t s s e i z i n g u n d e r e x t r e m e pressure c o n d i t i o n s , reduces w e a r , a n d m a i n t a i n s a w e l l - l u b r i c a t e d m o t i o n . A d d i t i o n a l w o r k is i n progress w i t h t h e x a n t h a t e a n d t h i o c a r b a m a t e s t o i m p r o v e t h e s t a b i l i t y o r shelf l i f e o f these a d d i t i v e s . S i m i l a r l u b r i c a t i n g a p p l i c a t i o n s are p r o p o s e d f o r t h e a l k y l - s u b s t i t u t e d a m m o n i u m salts o f t e t r a t h i o m o l y b d i c a c i d , ( R N H ) M o S . T h e s e salts are p r e p a r e d b y r e a c t i o n of t h e a m i n e h y d r o c h l o r i d e w i t h a m m o n i u m o r a l k a l i m e t a l t e t r a t h i o m o l y b d a t e i n aqueous solution : 3

2

4

2RNH .HC1 + Na MoS -> (RNH ) MoS + 2NaCl 2

2

4

3

2

4

T h e s e c o m p o u n d s a p p a r e n t l y h a v e some s o l u b i l i t y i n s o l v e n t s s u c h as p o l y a l k y l e n e g l y c o l s ( U c o n fluids) a n d i n f a t t y a c i d oils, b u t are i n s o l u b l e i n p e t r o l e u m s o l v e n t s a n d c a n b e d i s s o l v e d i n w a t e r o n l y w i t h d i f f i c u l t y (3). C h e l a t e s as C a t a l y s t R a w M a t e r i a l s . S e v e r a l p a t e n t s h a v e r e c e n t l y c l a i m e d t h e use o f o r g a n o m o l y b d e n u m c o m p o u n d s as r a w m a t e r i a l s f o r s u p p o r t e d c a t a l y s t s , i n o r d e r t o a v o i d t h e u s u a l e v o l u t i o n of a m m o n i a v a p o r s f r o m a m m o n i u m m o l y b d a t e b y i m p r e g n a t i n g a c a t a l y s t c a r r i e r w i t h m o l y b d e n u m o x a l a t e i n a q u e o u s s o l u t i o n (33). A n o t h e r a p p l i c a t i o n p r o p o s e s t h e u s e of m o n o e t h y l a m m o n i u m tetrathiomolybdate ( p r o b a b l y a n e t h y l - s u b s t i t u t e d a m m o n i u m salt o f t e t r a t h i o m o l y b d i c a c i d , m a d e as d e s c r i b e d a b o v e ) as a h y d r o g e n a t i o n - d e h y d r o g e n a t i o n c a t a l y s t m a t e r i a l . T h e c a r r i e r c o a t i n g , a f t e r c a l c i n i n g a t 3 0 0 ° C , is r e p o r t e d t o b e m o l y b d e n u m t r i s u l f i d e . O n l y a f t e r n i t r o g e n t r e a t m e n t a t 4 4 0 ° C . are coatings o f c r y s t a l l i n e m o l y b d e n u m disulfide o b t a i n e d (37). R e c o g n i t i o n t h a t s u b s e x i v a l e n t m o l y b d e n u m i s t h e a c t i v e c a t a l y s t i n a v a r i e t y of c h e m i c a l r e a c t i o n s m a y l e a d t o f u r t h e r u t i l i z a t i o n o f t h e o r g a n i c c o m p l e x e s as molybdenum catalyst raw materials. T h e multivalent forms ( + 3 to + 6 ) of t h e o x a l a t e c o m p l e x e s m a k e these l i k e l y choices f o r s u c h m a t e r i a l s . S o l u b i l i t y l i m i t a t i o n s of these oxalates, h o w e v e r , d i r e c t a t t e n t i o n t o t h e i r u s e i n t w o t y p e s of c a t a l y s t s : supported catalysts, w h i c h require that the m o l y b d e n u m be i n a water-soluble f o r m ; a n d c a t a l y s t s w h i c h are u s e d as i n s o l u b l e c r y s t a l s o r a m o r p h o u s gels i n v a p o r o r l i q u i d phase r e a c t i o n s .


362


B e c a u s e m a n y o f t h e o r g a n i c c o m p l e x e s n o w u n d e r i n v e s t i g a t i o n are o i l - s o l u b l e , t h e i r p o t e n t i a l c a t a l y t i c use i n h o m o g e n e o u s h y d r o c a r b o n r e a c t i o n s is of g r e a t i n t e r e s t . T h e x a n t h a t e s a n d t h i o c a r b a m a t e s are also o i l - s o l u b l e a n d offer a m e a n s o f m a n u f a c t u r i n g m o l y b d e n u m sulfide c a t a l y s t s , b o t h s u p p o r t e d a n d u n s u p p o r t e d . N e w m o l y b d e n u m esters h a v e a s i m i l a r p o t e n t i a l i n c a t a l y t i c a p p l i c a t i o n s .

Molybdenum

Esters

O v e r 5 0 y e a r s ago, R o s e n h e i m d e s c r i b e d t h e existence o f a d i m e t h y l ester o f m o l y b d i c a c i d (34), p r e p a r e d b y a d d i n g m o l y b d i c oxide d i h y r a t e t o m e t h a n o l . C r i t i c a l p r e s e n t - d a y r e - e x a m i n a t i o n o f t h i s c l a i m s t r o n g l y suggests t h a t a n a l c o h o l a t e a n d n o t a n ester w a s f o r m e d . R o s e n h e i m (35) has m o r e r e c e n t l y d e s c r i b e d t h e o n l y k n o w n s i m p l e ester t y p e compound, triphenoxymolybdenum dichloride, M o C l ( O C H ) . I t was p r e p a r e d b y t h e r e a c t i o n o f 1 m o l e of m o l y b d e n u m p e n t a c h l o r i d e w i t h 4 m o l e s o f p h e n o l i n c a r b o n d i s u l f i d e , g i v i n g a d a r k , r e d - p u r p l e , c r y s t a l l i n e s o l i d . T h i s c o m p o u n d is soluble i n c a r b o n d i s u l f i d e a n d benzene, a n d is r e p o r t e d t o b e h y d r o l y t i c a l l y s t a b l e , a l t h o u g h s u c h h y d r o l y t i c s t a b i l i t y h a s n o t been c o n f i r m e d . T h e p h e n o x y c o m p o u n d i s p r o b a b l y s t a b i l i z e d b y d o u b l e b o n d resonance i n v o l v i n g t h e benzene r i n g . I t i s n o t k n o w n u n d e r w h a t c o n d i t i o n s m o l y b d e n u m a l k o x i d e s c a n be s y n t h e s i z e d a n d w h e t h e r t h e y exist i n a s t a b l e f o r m . O t h e r cresylic acids, derivatives of salicylic acid, catechol, a n d 2 - h y d r o x y - m - t o l u i c a c i d , f o r m s i m i l a r esters w h i c h c o m p l e x w i t h o r g a n i c a n d i n o r g a n i c bases.


2

Organomolybdenum

6

5

3

Compounds

C o t t o n has r e c e n t l y r e v i e w e d t h e s u b j e c t of a l k y l a n d a r y l d e r i v a t i v e s o f t h e t r a n s i t i o n m e t a l s ( 7 ) . F o r t h e p u r p o s e of h i s p a p e r , he defined o r g a n o m e t a l l i c compounds exclusively i n terms of a l k y l a n d a r y l derivatives of a m e t a l . I n i t , three o t h e r p a r a l l e l classes o f m e t a l - c a r b o n b o n d e d c o m p o u n d s are b r i e f l y d i s c u s s e d : 1. C a r b o n y l s , cyanides, a n d cyanide complexes, isocyanides, a n d acetylides 2. Olefinic or acetylenic compounds 3. C y c l o p e n t a d i e n y l derivatives T h e o n l y a l k y l a n d a r y l d e r i v a t i v e s of m o l y b d e n u m r e p o r t e d i n t h a t r e v i e w were t h e p h e n y l m o l y b d e n u m c o m p o u n d s o f H e i n , a b o u t w h i c h t h e r e has been m u c h d i s p u t e . I n f o r m a t i o n c o n c e r n i n g classes 1 a n d 3 has r e c e n t l y been m a d e a v a i l a b l e . M o l y b d e n u m c a r b o n y l i s r e g a r d e d as t h e p a r e n t c o m p o u n d f o r t h e c y c l o p e n t a d i e n y l s a n d c a n be c o n s i d e r e d a n o r g a n o m e t a l l i c , as c a n i t s c y c l o p e n t a d i e n y l d e r i v a t i v e s , i n t h i s p a p e r . T h e p r o n o u n c e d s h o r t e n i n g of t h e M o — C b o n d d i s t a n c e r e l a t i v e t o t h a t e x p e c t e d f r o m t h e s u m of c o v a l e n t r a d i i i n d i c a t e s e x t e n s i v e 7r-bonding i n t h e c a r b o n y l . O n t h e o t h e r h a n d , t h e M o — C b o n d force c o n s t a n t is i n t h e e x a c t r a n g e t o b e e x p e c t e d f o r single e l e c t r o n - p a i r b o n d s b e t w e e n m o l y b d e n u m a n d c a r b o n . M o l y b d e n u m H e x a c a r b o n y l . M o l y b d e n u m hexacarbonyl is the most stable c o m p o u n d a m o n g t h e M o — C b o n d e d classes, because of o c t a h e d r a l , e l e c t r o n - p a i r c o o r d i n a t i o n , a n d c o v a l e n t b o n d i n g . I t is r e l a t i v e l y s i m p l y m a d e i n g o o d y i e l d s a n d t h u s lends itself r e a d i l y t o c o m m e r c i a l a p p l i c a t i o n . T h e best p r e p a r a t i o n t e c h n i q u e t o d a t e is t h a t w h i c h was d e s c r i b e d b y K o c h e s h k o v (21), as m o d i f i e d b y t h e B e l l L a b o r a t o r i e s . T h e r e a c t i o n is c a r r i e d o u t i n a n a u t o c l a v e u s i n g a n h y d r o u s m o l y b d e n u m p e n t a c h l o r i d e d i s s o l v e d i n e t h e r . F i n e l y d i v i d e d zinc is used as b o t h a m e t a l l i c c a t a l y s t a n d a r e d u c i n g agent f o r t h e c h l o r i d e . P r e s s u r e s o f c a r b o n m o n o x i d e v a r y f r o m 600 t o 1100 p.s.i. w i t h a n a v e r a g e p r e s s u r e o f a b o u t 800 p . s . i . A u t o c l a v e t e m p e r a t u r e s h a v e v a r i e d w i d e l y a r o u n d r o o m t e m p e r a t u r e , because of t h e e x o t h e r m i c n a t u r e of t h e r e a c t i o n a n d of t h e v a r i a t i o n s i n t h e c o o l i n g t e c h n i q u e . A recent p a t e n t suggests t h e use o f a n a l u m i n u m a l l o y p o w d e r , c o n t a i n i n g



363

5 0 % copper, 4 5 % a l u m i n u m , a n d 5 % zinc, instead of a l l zinc. W i t h this alloy, a 9 0 % y i e l d o f t h e c a r b o n y l i s o b t a i n e d a t 1 0 0 ° C . a n d 1500 p.s.i. i n a r e a c t i o n t i m e o f 3 h o u r s (17).

Table I.

Properties of Molybdenum


Formula Molecular weight Appearance Melting point, °C. Specific gravity Solubility Water Ether at 30° C . JP4, jet fuel JP5, jet fuel M I L 7808, lube oil Vapor pressure 80° to 150° C. 0° to 50° C . Stability Water Air Acids Strong basic solutions Bromine vapor Heats of combustion Heat of formation Q at 25° C . calcd. Heat capacity Specific heat p

Hexacarbonyl

Mo(CO) 264.01 White crystals, diamagnetic Volatile, decomposes below 150° C . 1.96 6

Insoluble 2.5 wt.% 30° C./10.99 g./l.; 50° C . 18.30 g./l. 7.78 17.90 3.96 11.95 logio ρ = 11.406 - 3654/JT logio ρ = 11.795 - 3800/7 (ρ in mm. of mercury, Τ in °K.) Stable Stable Stable Decomposes Decomposes, forms Μ0ΒΓ4 507.58 kcal./mole 506.69 233.12 0.22804 + 0.0 848< - 0.0 1264*2 0.22974 + 0.0s2202i - 0.05379* (c values are per unit weight of molybde num contained and apply to tempera ture range 20° to 78° C.) 4

6

2

p

T h e p h y s i c a l properties of the c a r b o n y l c o m p o u n d a r e shown i n T a b l e I . I t s a p p a r e n t l a c k o f t o x i c i t y m a y be d u e i n l a r g e m e a s u r e t o i t s l o w v a p o r p r e s s u r e a t room temperature, i n contrast to t h e other carbonyls w h i c h m a y have appreciable v a p o r p r e s s u r e e v e n a t r o o m t e m p e r a t u r e a n d hence a r e v e r y p o i s o n o u s i f i n h a l e d . M o l y b d e n u m c a r b o n y l m a y be t h e r m a l l y decomposed a t l o w temperatures i n a v a r i e t y o f a t m o s p h e r e s t o y i e l d films o f m o l y b d e n u m m e t a l , m o l y b d e n u m c a r b i d e , a n d m o l y b d e n u m sulfides a n d oxides. T h i s p r o p e r t y m a k e s m o l y b d e n u m c a r b o n y l i n t e r e s t i n g as a m a t e r i a l i n m a n y p y r o l y t i c p l a t i n g processes. Coatings o n metallic a n d nonmetallic—for example, ceramic—particles have wide c o m m e r c i a l i m p l i c a t i o n s . P r o b a b l y the most i m p o r t a n t of the products obtained thus far are the alloys w i t h c a r b o n a n d t h e carbides. C o h e r e n t a n d adherent coatings of t h e c a r b i d e s o n a base m e t a l h a v e been m a d e b y a d j u s t i n g t h e p l a t i n g c o n d i t i o n t o g i v e a n y v a l u e o f c a r b o n c o n t e n t f r o m zero t o a b o u t 3 5 a t o m i c % . T h e h a r d n e s s depends p r i m a r i l y o n t h i s c a r b o n c o n t e n t i n t h e p l a t e , some c o a t i n g s b e i n g h a r d e r t h a n sapphire. N e w carbides of m o l y b d e n u m a n d alloys supersaturated w i t h carbon have also b e e n p r o d u c e d . P l a t i n g c a n b e c a r r i e d o u t a t t e m p e r a t u r e s as l o w as 1 5 0 ° C . a n d t h u s , i n t h e presence o f o t h e r substances l i k e c a r b o n m o n o x i d e , h y d r o g e n sulfide, a n d w a t e r r e a c t i o n s occur w h i c h could n o t be produced i n another w a y . E q u i l i b r i u m data relating t e m p e r a t u r e a n d gas c o m p o s i t i o n f o r t h e p r e p a r a t i o n of p l a t e c o m p o s i t i o n s c o n t a i n i n g g i v e n q u a n t i t i e s of c a r b o n , s u l f u r , o r o x y g e n h a v e b e e n p r e s e n t e d b y L a n d e r a n d G e r m e r (22). P u r e m o l y b d e n u m c o a t i n g s m a y h a v e a p p l i c a t i o n i n e l e c t r o n i c o r e l e c t r i c a l devices, i n t h e field o f h i g h t e m p e r a t u r e s , a n d i n c a t a l y t i c a p p l i c a t i o n s . T h e h a r d a l l o y s w i t h c a r b o n , a n d t h e c a r b i d e s , m a y p r o v i d e g o o d w e a r i n g surfaces f o r b e a r i n g s , dies, r o l l s , gages, a n d o t h e r tools. M o l y b d e n u m sulfide, f o r m e d v i a v a p o r p l a t i n g , m a y b e u s e f u l as a l u b r i c a t i n g film, as a s e m i c o n d u c t o r , a n d as a c a t a l y s t o n a v a r i e t y o f n o n m e t a l l i c supports.



364

Aryl Isocyanide Derivatives Malatesta

(25) h a s p r e p a r e d

molybdenum

h e x a a r y l isocyanides,

Mo (CNR) , 6

i n l o w y i e l d s by r e a c t i o n o f a r y l i s o c y a n i d e s w i t h m o l y b d e n u m t r i c h l o r i d e i n a l c o h o l . These compounds undergo slow decomposition i n air. n—C H Mo(CO) 5

5

MOTT—C5H5

6

M o l y b d e n u m h e x a c a r b o n y l reacts w i t h cyclopentadiene o r w i t h s o d i u m c y c l o p e n t a diene i n t e t r a h y d r o f u r a n t o g i v e a series o f c y c l o p e n t a d i e n y l m o l y b d e n u m of w h i c h ferrocene i s t h e p r o t o t y p e .

compounds,

T h e m o l y b d e n u m atom is bonded t o the

cyclo

pentadienyl ring b y a delocalized a n d essentially covalent b o n d .

T h e r e are no covalent

bonds between a p a r t i c u l a r carbon atom a n d the m o l y b d e n u m

atoms.

T h e f o l l o w i n g series o f r e a c t i o n s i l l u s t r a t e s t h e r a n g e o f s t a b l e c o m p o u n d s w h i c h


h a v e b e e n m a d e i n t h i s n e w class (30) : Preparation of Intermediates C H N a + M o ( C O ) -> C I I M o ( C O ) N a + S C O 6

6

6

5

s

3

C H M o ( C O ) N a + H O Ac 5

5

C H Mo(CO) H + NaOAc

3

Typical

5

5

3

Reactions

2 C H M o ( C O ) H + A i r -> C 5 H M o ( C O ) M o C H 5 + H 0 5

5

3

5

6

5

2

C H M o ( C O ) H + C C U -> C H M o ( C O ) C l + C H C 1 5

5

3

5

5

3

C H M o ( C O ) N a + C H I -> C H M o ( C O ) C H 5

5

3

3

5

5

3

3

3

+ Nal

T h e structure of biscyclopentadienyl carbonyl, has b e e n

t h e subject

71—C H Mo—(CO) MOTJ—C H , 5

of m u c h discussion i n recent

months.

5

6

W h i l e i t was

5

5

initially

believed t h a t i t was essentially a " t r i p l e - d e c k e r s a n d w i c h , " recent x - r a y diffraction studies a t t h e M a s s a c h u s e t t s I n s t i t u t e of T e c h n o l o g y

show

d i m e r of a c y c l o p e n t a d i e n y l m o l y b d e n u m t r i c a r b o n y l .

that t h e molecule

is a

T h e r e are n o c a r b o n y l b r i d g e s

t o f o r m a s u p e r s a n d w i c h a n d t h e m o l e c u l e i s n o t l i n e a r (^1).

Alkyl Cyclopentadienyl Derivatives From

the 7r-cyclopentadienyl

molybdenum

t r i c a r b o n y l h y d r i d e , a n u m b e r of

c o m p o u n d s w i t h a m e t a l - t o - c a r b o n s i g m a b o n d h a v e b e e n p r e p a r e d as i n d i c a t e d by t h e a b o v e series o f r e a c t i o n s reacting a l k y l halides w i t h

The

(81).

following alkyl

derivatives were

prepared by

7i-C H MO(CO) Na: 5

5

3

7T-C H Mo(CO) CH 5

5

3

3

7r-C H Mo(CO) C H 5

5

3

2

5

7 r - C H M o ( C O ) iso C H 5

5

3

3

7

A l l o f these c o m p o u n d s are d i a m a g n e t i c a n d a r e r e a d i l y s o l u b l e i n p e t r o l e u m ( 3 0 ° t o 6 0 ° C . ) a n d i n the usual organic solvents. at

ether

T h e y sublime easily i n h i g h v a c u u m

temperatures f r o m 2 5 ° t o 5 0 ° C . a n d have a noticeable camphoraceous

odor. I n

o r g a n i c s o l v e n t s , a l l t h e c o m p o u n d s are s l o w l y d e c o m p o s e d b y a i r . T h e s t a b i l i t y o f these c o m p o u n d s i s i n v e r s e l y p r o p o r t i o n a l t o t h e l e n g t h o f t h e carbon chain i n the a l k y l group.

The methyl compound

begins t o decompose i n a i r

after a few days a n d u p o n heating i n v a c u u m a t 1 1 0 ° C .

T h e ethyl compound is

n o t i c e a b l y less s t a b l e a n d t h e i s o p r o p y l c o m p o u n d e v e n less s t a b l e . T h e compounds a r e a l l y e l l o w a n d a r e soluble i n water a n d unaffected T h e y a r e a t t a c k e d b y a c i d s a n d bases, b u t d o n o t f o r m c a t i o n s .

by it.

Halogens react t o

f o r m the a l k y l halides a n d the 7r-cyclopentadienyltricarbonyl halides.


DEAN, KAY, AND LARSON—MOLYBDENUM CHELATES, ESTERS, AND ORGANOMETALLICS Cyclopentadienyl Carbonyl

365

Hydride

A y i e l d of C H M o ( C O ) H of 9 0 % based o n m o l y b d e n u m h e x a c a r b o n y l was obtained b y the reaction shown above. T h e hydride sublimes at 1 0 ~ m m . of m e r c u r y a n d 5 0 ° C . I n n o n p o l a r s o l v e n t s , s u c h as p e t r o l e u m e t h e r , t h e h y d r i d e i s d e c o m p o s e d t o a b l a c k m a s s b y a i r . H o w e v e r , i n p o l a r s o l v e n t s , s u c h as t e t r a h y d r o f u r a n , s m o o t h o x i d a t i o n t o 7 r - C H M O ( C O ) M 0 7 r - C H o c c u r s (31). 5

5

3

2

5

5

5

6

5

Reaction o f t h e h y d r i d e i n a n excess o f c a r b o n tetrachloride gives 7 r - C H M o ( C O ) C l and C H C 1 at 25°C. T h e c h l o r i d e exists a s o r a n g e - r e d c r y s t a l s , d e c o m p o s i n g a t 1 4 5 ° C . w i t h o u t m e l t i n g . I t is o n l y s l i g h t l y s o l u b l e i n p e t r o l e u m , b u t is soluble i n p o l a r organic solvents w i t h o u t decomposition. T h e bromide a n d iodide have also b e e n p r e p a r e d f r o m t h e h y d r i d e . R e d c r y s t a l s o f these h a l i d e s m e l t a t 1 5 0 - 1 ° C . a n d 13Φ-5°0., respectively. 5

5

3

3

T h e c o m p o u n d , 7 r - C H M o ( C O ) N O , c a n be m a d e b y d i r e c t a c t i o n o f n i t r i c o x i d e on the h y d r i d e i n a n organic solvent. T h i s c o m p o u n d forms stable orange crystals, m e l t i n g a t 8 5 . 2 - 5 . 7 ° C . a n d is r e a d i l y s o l u b l e i n o r g a n i c s o l v e n t s w i t h o u t d e c o m p o s i t i o n .


5

5

2

Dibenzene Molybdenum T h e o t h e r o u t s t a n d i n g d e v e l o p m e n t i n o r g a n o m e t a l l i c r e s e a r c h is t h e s y n t h e s i s a n d characterization of dibenzene compounds of c h r o m i u m , m o l y b d e n u m , a n d tungsten b y F i s c h e r (12). T h i s u n i q u e d i s c o v e r y has c l e a r e d u p t h e p e r p l e x i n g q u e s t i o n of t h e n a t u r e o f t h e s u p p o s e d p h e n y l c h r o m i u m a n d m o l y b d e n u m c o m p o u n d s o f H e i n (13). D i b e n z e n e m o l y b d e n u m (as w e l l as c h r o m i u m a n d t u n g s t e n ) has b e e n f o u n d t o possess a hexagonal, prismatic, centrosymmetric structure. D i b e n z e n e m o l y b d e n u m is s y n t h e s i z e d f r o m m o l y b d e n u m p e n t a c h l o r i d e first as a n aqueous s o l u b l e c a t i o n ( u n s t a b l e i n a i r ) , w h i c h i s t h e n r e d u c e d t o a c o m p o u n d t h a t is v e r y u n s t a b l e i n a i r , is s o l u b l e i n o r g a n i c s o l v e n t s , a n d i s also n e u t r a l . T h e f o r m a t i o n of t h e c a t i o n i s c a r r i e d o u t i n a b o m b h e a t e d t o 1 5 0 ° C . T h e following equation shows the synthesis : 3MoCl

5

+ 4A1 + 6 C H 6

6

- ^ Î I » 3 M o ( C H ) + A1C1 + 3A1C1 150° c

6

6

2

4

3

A f t e r h y d r o l y s i s of the complex, the cation is reduced b y a new reducing agent, ( N H ) 2 C ( S 0 K ) 2 , diaminomethane d i s u l f o n i u m potassium. A s the n e u t r a l dibenzene m o l y b d e n u m i s u n s t a b l e i n a i r , care m u s t b e t a k e n t o e x t r a c t a n d s u b l i m e i t u n d e r oxygen-free conditions. Dibenzene m o l y b d e n u m t h e r m a l l y decomposes a t 100°C. t o give a m e t a l m i r r o r . 2

2

Future Objectives Research a n d development on organomolybdenum compounds are expanding a t a p a c e c h a r a c t e r i s t i c o f t h e e n t i r e field o f m e t a l c h e m i c a l s . T h e a b o v e d i s c u s s i o n has been d e v o t e d t o t h e c h e l a t e s , esters, a n d o r g a n o m e t a l l i c c o m p o u n d s o f m o l y b d e n u m . O n l y t h e chelates h a v e f o u n d e x t e n s i v e c o m m e r c i a l u t i l i z a t i o n a s b r i l l i a n t l y c o l o r e d o r g a n i c p i g m e n t s a n d a s m e t a l c o a t i n g s . A m o r e c o m p l e t e s u m m a r y o f uses a n d p o t e n t i a l uses f o r these c o m p l e x e s i s p r e s e n t e d i n T a b l e I I . C a t a l y s t s a n d n e w pigments appear t o hold considerable promise f o r future utilization of organo molybdenum compounds. P r e p a r a t i o n of the chelate derivatives depends largely u p o n the a v a i l a b i l i t y of soluble compounds o f m o l y b d e n u m . M o l y b d i c oxide a n d s o d i u m m o l y b d a t e have b e e n g e n e r a l l y u s e d as s t a r t i n g m a t e r i a l s f o r t h e chelates. O t h e r s i m p l e , i s o p o l y s a l t s a n d heteropolymolybdates are now becoming familiar t o organic chemists. M o l y b d e n u m p e n t a c h l o r i d e is a c o n v e n i e n t s t a r t i n g m a t e r i a l f o r t h e k n o w n ester, t r i p h e n o x y m o l y b d e n u m dichloride and m o l y b d e n u m hexacarbonyl f o r the organometallics.



366

Table II.

Uses for Molybdenum Organics Present Commercial Uses P M A and P M T A color lakes and toners for printing inks, tints, water colors, show card inks, wax crayons, colored paper, and enamels for children's toys

Bonding Mo—N—C

Type Chelates

Metal coatings using phenolic complex

Mo—O—C Mo—S—C

Casein dyes from phthalocyanine derivatives Metallized diazo dyes; colorimetric analyses Catalysts Lubricants

Esters

MoCl2(OC H )8

Catalysts

Organometallics

Mo(CO)

Vapor plating Catalysts Catalysts Ion exchange resins New plastics Modified resins

6

6

6

C H Mo(CO) H B


Potential Uses New toners from other heteropoly acids

6

3

Organomolybdenum compounds, derived from molybdenum hexacarbonyl, are receiving systematic attention i n industrial a n d academic laboratories a t t h e present t i m e . M o l y b d e n u m c a r b o n y l , c o n s i d e r e d as t h e p a r e n t of t h e k n o w n o r g a n o m e t a l l i c s , has p r o v e d p r a c t i c a l f o r t h e v a p o r p l a t i n g of m e t a l l i c m o l y b d e n u m o r i n t e r m e t a l l i c films o n m e t a l o r c e r a m i c surfaces. V a p o r p l a t i n g m a y b e a s a t i s f a c t o r y a l t e r n a t i v e t o e l e c t r o p l a t i n g , w h i c h h a s n e v e r p r o v e d c o m p l e t e l y feasible f o r m o l y b d e n u m . C y c l o p e n t a d i e n y l d e r i v a t i v e s a r e t h e s u b j e c t of intense, f u n d a m e n t a l s t u d y . P o t e n t i a l uses f o r these o r g a n o m e t a l l i c s a r e also suggested i n T a b l e I I . A p p l i c a t i o n r e s e a r c h w i l l f o l l o w t h e s y n t h e s i s a n d c h a r a c t e r i z a t i o n of a n y of these s t a b l e d e r i v a tives.

Literature Cited (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15) (16) (17) (18) (19) (20) (21) (22) (23) (24) (25) (26) (27) (28)

Barbieri, G. Α., Malguti, Α., Mem. accad. sci. ist. Bologna 9, 3-8 (1951-52). Bhaduri, A. S., Ray, P., Sci. and Culture (Calcutta) 18, 97-8 (1952). Brit. Patent Appl. 765,507 (Jan. 6, 1955). Bucknall, W. R., Carter, S. R., Wardlaw, W., J. Chem. Soc. 1927, 518-19. Climax Molybdenum Co., Chem. Data Bull. 12, "Properties of Heteropolymolyb -dates," 1956. Coates, J . W., Crawford, J . W. C. (to Imperial Chemical Industries), Brit. Patent 582,899 (Dec. 2, 1946). Cotton, F. Α., Chem. Revs. 55, 551-90 (1955). Crossley,M.L., Shafer, L . M. (to Calco Chemical Co.), U . S. Patent 2,136,650 (Nov. 15, 1939). Dodd, S. R., Ayres, E. F. (to Oakite Products), Ibid.,2,502,441 (April 4, 1950). Fernandes, L., Gazz. chim. ital. 55, 424-40 (1925). Fernandes, L., Palazzo, F., Ibid.,57, 567-74 (1927). Fischer, E. O., Hafner, W., Z. anorg. u. allgem. Chem. 286, 146-8 (1956). Hein, F., Angew. Chem. 51, 507 (1938). Hieber, W., Muhlbauer, F., Z. anorg. u allgem. Chem. 221, 337-48 (1935). Hieber, W., Scharfenburg,C.,Ber. deut. chem. Ges. 73B, 1012-21 (1940). Hugel, M . G., Rev. inst.franç.pétrole et Ann. combustibles liquides 10, 1280-83 (October 1955). Hurd, D. T. (to General Electric Co.), U. S. Patent 2,554,194 (May 22, 1951). Killeffer, D. H., Linz, Α., "Molybdenum Compounds," pp. 171-2, Interscience, New York, 1952. Ibid., pp. 193-4. Ibid.,p. 195. Kocheshkov et al., Doklady Akad. Νauk S.S.S.R. 26, 54-6 (1940). Lander, J. J., Germer, L. H., Trans. Am. Inst. Mech. Engrs. 175, 648-92 (1948). McKaveny, J. P., Frieser, H., Anal. Chem. 29, 290 (1957). Malatesta, L., Gazz. chim. ital. 69, 408-16 (1934) ; 752-62 (1939). Malatesta, L., Sacco, Α., Gabaglio, M., Ibid., 82, 548-51 (1952). Morgan, G. T., Castell, R. A. S., J. Chem. Soc. 1928, 3252-6. Montecatini Soc. generale per l'industria mineraria, French Patent 848,736 (Nov. 6, 1939). Pecsok, R. L., Sawyer, D . T., J. Am. Chem. Soc. 78, 5496 (1956). In METAL-ORGANIC COMPOUNDS; Advances in Chemistry; American Chemical Society: Washington, DC, 1959.


367

(29) Pilipenko, A. T., Gredchina, G. I., Trudy. Komissii. Anal. Khim. Akad. Νauk S.S.S.R. 3, 178-87 (1951). (30) Piper, T. S., Wilkinson, G., J. Inorg. & Nuclear Chem. 3, 321-31 (1955). (31) Ibid., 3 (1956), TP 104-24. (32) Price, Donald, Ind. Eng. Chem. 47, 1511 (1955). (33) Riedl, F. J. (to Universal Oil Products Co.), U. S. Patent 2,753,310 (July 3, 1956). (34) Rosenheim, Α., Bertheim, Α., Ζ. anorg. Chem. 34, 437 (1903). (35) Rosenheim, Α., Nernst, C., Z. anorg. u. allgem. Chem. 214, 209-24 (1933). (36) Smith, Ε. E., Symposium on Additives in Lubricants, Division of Petroleum Chemis try, 130th Meeting, ACS, Atlantic City, N . J., September 1956. (37) Spengler, G., to Alpha Molykote Corp., private communication. (38) Wardlaw, W., Parker, W. H., J. Chem. Soc. 127, 1312 (1925). (39) Wardlaw, W., Wormell, R. L., Ibid., 125, 2370 (1924). (40) Williams, W. W., Conley, J., Ind. Eng. Chem. 47, 1507 (1955). (41) Wilson, F. C., Shoemaker, D. P., Naturwissenschaften 43, 57 (1956).


RECEIVED for review May 10, 1957. Accepted June 1, 1957.


METAL-ORGANIC COMPOUNDS

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