Techniques in the Handling of Highly Reduced ... - ACS Publications

Chapter 3

Techniques in the Handling of Highly Reduced Organometallics John E. Ellis

Downloaded by UNIV MASSACHUSETTS AMHERST on October 6, 2012 | http://pubs.acs.org Publication Date: November 24, 1987 | doi: 10.1021/bk-1987-0357.ch003

Department of Chemistry, University of Minnesota, Minneapolis, M N 55455

Procedures used and developed in our laboratory for the synthesis, isolation and characterization of highly air sensitive organometallic compounds are reviewed. Details of the inert atmosphere purification system, vacuum line and specialized glassware employed in these operations are also presented.

The o b j e c t i v e o f t h i s a c c o u n t i s t o d e s c r i b e some o f t h e a p p a r a t u s and p r o c e d u r e s used i n t h i s l a b o r a t o r y f o r t h e s y n t h e s i s , i s o l a t i o n and p u r i f i c a t i o n o f h i g h l y m o i s t u r e and oxygen s e n s i t i v e organom e t a l l i c compounds. S p e c i a l a t t e n t i o n w i l l be g i v e n t o t h e i n e r t gas p u r i f i c a t i o n system, vacuum l i n e , t r a n s f e r methods and s p e c i a l i z e d g l a s s w a r e and a s s o c i a t e d a p p a r a t u s employed i n t h e s e o p e r a t i o n s . T h i s treatment i s n o t i n t e n d e d t o be a complete g u i d e t o t h e s y n t h e s i s and h a n d l i n g o f a i r s e n s i t i v e m a t e r i a l s , b u t i t i s hoped t h a t the d e t a i l s and o b s e r v a t i o n s p r e s e n t e d h e r e i n w i l l be e s p e c i a l l y u s e f u l t o n o v i c e s i n t h i s a r e a and t h o s e who have n o t had t h e o p p o r t u n i t y t o v i s i t l a b o r a t o r i e s i n w h i c h such c h e m i s t r y i s r o u t i n e l y c a r r i e d out. U n d o u b t e d l y , t h e b e s t g e n e r a l c o m p i l a t i o n o f such p r o c e d u r e s and t e c h n i q u e s i s t h e r e c e n t l y p u b l i s h e d book by D.F. S h r i v e r and M.A. Drezdzon. (_1) S e v e r a l o f t h e diagrams o f a p p a r a t u s p r e sented h e r e i n represent r a t h e r simple m o d i f i c a t i o n s o f glassware i n i t i a l l y observed i n o t h e r l a b o r a t o r i e s , j o u r n a l a r t i c l e s , espec i a l l y J o u r n a l o f Chemical Education, Inorganic Syntheses, c a t a l o g s of s c i e n t i f i c g l a s s w a r e ( e s p e c i a l l y Ace G l a s s and Kontes G l a s s Companies), and o t h e r sources.(2-12) However, u n l i k e most drawings i n t h e l i t e r a t u r e , t h e ones p r e s e n t e d h e r e i n a r e s u f f i c i e n t l y d e t a i l e d t o be s e n t d i r e c t l y t o t h e g l a s s b l o w e r f o r f a b r i c a t i o n . H o p e f u l l y t h i s u s e f u l f e a t u r e w i l l warrant t h e i r i n c l u s i o n . Any l a b o r a t o r y i n v o l v e d i n o r g a n o m e t a l l i c r e s e a r c h s h o u l d have a v a i l a b l e a v a r i e t y o f methods f o r t h e h a n d l i n g o f m a t e r i a l s o f d i v e r s e p h y s i c a l and c h e m i c a l p r o p e r t i e s . These i n c l u d e g l o v e boxes, h i g h and medium vacuum l i n e s and a s s o c i a t e d g l a s s w a r e and a p p a r a t u s .

0097-6156/87/0357-0034S09.00/0 © 1987 American Chemical Society

In Experimental Organometallic Chemistry; Wayda, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.


3.

ELLIS

Techniques in the Handling of Highly Reduced Organometallics 35

A l t h o u g h some o r g a n o m e t a l l i c r e s e a r c h groups conduct p r a c t i c a l l y a l l of t h e i r s y n t h e t i c o p e r a t i o n s i n h i g h l y e f f i c i e n t (and e x p e n s i v e ! ) commercial g l o v e boxes, we p r e f e r to use a g l o v e box m a i n l y f o r the p r e p a r a t i o n o f samples f o r s p e c t r o s c o p i c and e l e m e n t a l a n a l y s i s , t r a n s f e r and w e i g h i n g of s o l i d r e a c t a n t s o r p r o d u c t s and s t o r a g e of samples. I n g e n e r a l , i t has been our e x p e r i e n c e t h a t o r g a n o m e t a l l i c s s u r v i v e b e t t e r i n the atmosphere s u p p l i e d by a v a c u u m - i n e r t gas manif o l d t h a n t h a t of a g l o v e box, even a f t e r the d r y t r a i n charge of the g l o v e box (Vacuum Atmospheres Corp.) has been r e g e n e r a t e d . For t h i s r e a s o n h i g h l y s e n s i t i v e s o l i d s s h o u l d be s t o r e d i n s e a l e d g l a s s ampoules, S c h l e n k tubes o r o t h e r v e s s e l s w h i c h a r e impermeable t o a i r , r a t h e r than screw capped v i a l s o r b o t t l e s i n a g l o v e box. Indeed, many o f the s u b s t a n c e s t h a t members of our group r o u t i n e l y h a n d l e appear t o be more e f f i c i e n t i n removing oxygen o r m o i s t u r e from an " i n e r t " atmosphere than the p u r i f i c a t i o n t r a i n of our g l o v e box. For t h i s r e a s o n , m a t e r i a l s t o be s u b m i t t e d f o r e l e m e n t a l a n a l y s i s a r e handled w i t h p a r t i c u l a r c a r e . A f t e r the samples a r e p l a c e d i n ampoules, w h i c h a r e s e a l e d t o a m o d i f i e d S c h l e n k tube, the ampoules a r e evacuated and r e f i l l e d t h r e e o r f o u r times w i t h i n e r t gas s u p p l i e d from our vacuum l i n e . They a r e t h e n s e a l e d o f f , i n s p e c t e d a f t e r a day w i t h a hand l e n s o r m i c r o s c o p e f o r sample d e t e r i o r a t i o n and sent out f o r a n a l y s i s i f e v e r y t h i n g l o o k s s a t i s f a c t o r y . A l s o , i n so f a r as p o s s i b l e , samples s u b m i t t e d f o r a n a l y s i s a r e handled o n l y i n s o l v e n t f r e e g l o v e boxes. Other groups have emphasized the i m p o r t a n c e of u s i n g h i g h vacuum (10"' to 10~6 t o r r ) l i n e s i n o r g a n o m e t a l l i c r e s e a r c h . While t h i s t e c h n i q u e i s almost mandatory f o r the h a n d l i n g of m i l l i g r a m q u a n t i t i e s of h i g h l y a i r s e n s i t i v e m a t e r i a l s , e s p e c i a l l y when they a r e p r e s e n t i n d i l u t e s o l u t i o n s or of h i g h m o l e c u l a r w e i g h t , p h y s i c a l s t u d i e s where t r a c e s of o x i d a t i o n p r o d u c t s cannot be t o l e r a t e d , quant i t a t i v e t r a n s f e r s o f gases o r the d i s t i l l a t i o n and s u b l i m a t i o n o f t h e r m a l l y s e n s i t i v e m a t e r i a l s o f low v o l a t i l i t y , i t can be an i n e f f i c i e n t and o v e r l y r i g o r o u s way t o do o r g a n o m e t a l l i c c h e m i s t r y . For these r e a s o n s , most of the o p e r a t i o n s i n t h i s l a b o r a t o r y a r e conducted on t h e bench w i t h a d o u b l e m a n i f o l d medium vacuum (10~1 t o 10~3 t o r r ) l i n e such as the one d e s c r i b e d l a t e r i n t h i s a r t i c l e . T h i s i s a f l e x i b l e system w h i c h i s s u i t a b l e f o r most o p e r a t i o n s one w i l l encounter i n o r g a n o m e t a l l i c o r o r g a n i c s y n t h e s e s and r e q u i r e s l i t t l e maintenance a f t e r assembly. P r o v i d e d r e a c t i o n s a r e conducted w i t h c a r e on a r e a s o n a b l e s c a l e (ca. 25 mmole), t h e r e s h o u l d be m i n i m a l problems w i t h r e a c t a n t or product d e c o m p o s i t i o n by a i r . P r i n c i p a l advantages of t h i s t e c h n i q u e over t h o s e i n v o l v i n g g l o v e boxes o r h i g h vacuum l i n e s i n c l u d e r e l a t i v e l y s m a l l space r e q u i r e ments, low c o s t , e x c e l l e n t f l e x i b i l i t y and ease of m a n i p u l a t i o n s , and f a c i l e t r a n s f e r s of s o l u t i o n s by s y r i n g e or c a n n u l a e . A s i g n i f i cant d i s a d v a n t a g e , however, i s t h a t a p e r s o n p e r f o r m i n g an operat i o n w i t h a vacuum l i n e on an open bench o r i n a hood o f t e n needs to be more h i g h l y t r a i n e d , m e t i c u l o u s and a c u t e l y aware of p o t e n t i a l dangers than the i n d i v i d u a l who i s c a r r y i n g out r o u g h l y t h e same t a s k i n a g l o v e box, where m i s t a k e s and/or equipment f a i l u r e a r e l e s s l i k e l y to r e s u l t i n p e r s o n a l i n j u r y . One of t h e most common m i s t a k e s made w i t h a vacuum l i n e i s f o r one t o u n w i t t i n g l y open a tap on the l i n e t o a f l a s k c o n t a i n i n g a i r w h i l e a n o t h e r v e s s e l i s b e i n g evacuated. I f the l a t t e r f l a s k c o n t a i n s a h i g h l y oxygen s e n s i t i v e


EXPERIMENTAL ORGANOMETALLIC CHEMISTRY

36


m a t e r i a l an e x p l o s i o n c o u l d r e s u l t . T h i s i s p a r t i c u l a r l y a problem w i t h h i g h l y reduced m e t a l c a r b o n y l s w h i c h w i l l o f t e n explode when exposed t o even s m a l l amounts of a i r i n a c l o s e d system. A c a r d i n a l r u l e t o be observed when u s i n g any vacuum l i n e i s t h a t o n l y one v e s s e l s h o u l d be open to t h e vacuum chamber a t any g i v e n time. Any contemplated v i o l a t i o n of t h i s r u l e must be weighed v e r y c a r e f u l l y ! Many o t h e r h a z a r d s a r e a s s o c i a t e d w i t h the use of vacuum l i n e s w h i c h a r e beyond the scope o f t h i s b r i e f r e p o r t . I n t h i s r e g a r d , p a r t 2 of S h r i v e r and Drezdzon (1) s h o u l d be read soon and t h o r o u g h l y i f you a r e a newcomer t o the w o r l d o f vacuum l i n e s ! The

I n e r t Atmosphere P u r i f i c a t i o n System

A l t h o u g h some a u t h o r s have recommended the use of h i g h p u r i t y i n e r t gases w i t h o u t f u r t h e r p u r i f i c a t i o n (12) due to the r e a l p o s s i b i l i t y of i n t r o d u c i n g i m p u r i t i e s d u r i n g passage through a p o o r l y designed or contaminated " p u r i f i c a t i o n " system, an e f f e c t i v e gas p u r i f i c a t i o n t r a i n can be e x c e e d i n g l y important i n r e d u c i n g oxygen and m o i s t u r e to t o l e r a b l e l e v e l s . Our r e s e a r c h has r e q u i r e d the use o f such a system. One can purchase " r e s e a r c h g r a d e " n i t r o g e n o r argon w h i c h c o n t a i n s l e s s t h a n 10 ppm t o t a l i m p u r i t i e s , but i t i s p r o h i b i t i v e l y expensive f o r normal s y n t h e t i c work. P r e p u r i f i e d grades of n i t r o g e n o r argon (99.998 mole % p u r e ) a r e r e p o r t e d to c o n t a i n l e s s than 3 ppm H2O and 10 ppm o r 3 ppm 0 , r e s p e c t i v e l y ( 1 3 ) , w h i c h a r e a c c e p t a b l e l e v e l s f o r many purposes i n o r g a n o m e t a l l i c c h e m i s t r y . I f the i n e r t gas i n c y l i n d e r s were always of u n i f o r m and s p e c i f i e d p u r i t y , one c o u l d undoubtedly do much o r g a n o m e t a l l i c c h e m i s t r y w i t h o u t a gas p u r i f i c a t i o n system, but i t has been our e x p e r i e n c e t h a t t h i s i s g e n e r a l l y not t h e case. Indeed, p r e p u r i f i e d grades of these gases a t l e a s t from our s u p p l i e r s - or even "house n i t r o g e n " w h i c h i s o b t a i n e d from the e v a p o r a t i o n o f l i q u i d n i t r o g e n and c i r c u l a t e d throughout Departmental l a b o r a t o r i e s - w i l l o f t e n cause h y d r o c a r b o n s o l u t i o n s of T i C l ^ o r Zn(02^)2 to smoke, i n d i c a t i n g t h a t unaccept a b l e l e v e l s of m o i s t u r e o r oxygen, r e s p e c t i v e l y , a r e p r e s e n t . If the system i s p r o p e r l y c o n s t r u c t e d ( i . e . , f r e e of l e a k s ) of m a t e r i a l s which a r e impermeable t o a i r and i s m a i n t a i n e d c o n t i n u o u s l y a t p o s i t i v e p r e s s u r e , improved o r a t l e a s t r e p r o d u c i b l e r e s u l t s i n organom e t a l l i c r e s e a r c h should be o b t a i n e d , u n l e s s the process i s c a t a l y z e d or promoted by a d v e n t i t i o u s oxygen o r m o i s t u r e ! A schematic drawing of t h e i n e r t atmosphere p u r i f i c a t i o n system used i n our l a b o r a t o r y i s shown i n F i g u r e 1. F e a t u r e s of t h i s system a r e as f o l l o w s : 1. A l l components a r e g l a s s o r m e t a l except T e f l o n f e r r u l e s and stopcock plugs. 2. Swagelok (or G y r o l o k ) f i t t i n g s and copper t u b i n g p r o v i d e f l e x i b i l i t y and m i n i m i z e the use o f f r a g i l e g l a s s c o n n e c t i o n s . 3. T e f l o n f r o n t f e r r u l e s i n Swagelok f i t t i n g s p r o v i d e l e a k f r e e g l a s s to copper s e a l s and e l i m i n a t e the need f o r more expensive and f r a g i l e Kovar o r o t h e r m e t a l t o g l a s s s e a l s . 4. The c a t a l y s t i s m a i n t a i n e d a t about 150 C t o i n c r e a s e i t s oxygen a b s o r p t i o n c a p a c i t y (about 5x t h a t a t 25 C). 5. Wherever p o s s i b l e , g r e a s e l e s s c o n n e c t i o n s are i n c o r p o r a t e d to m i n i m i z e maintenance. W i t h normal use and source gas p u r i t y , the BASF c a t a l y s t and m o l e c u l a r s i e v e s need to be r e g e n e r a t e d a p p r o x i m a t e l y once every 5-6 y e a r s . 2



Safety bubbler

Fig.3

To p o w e r v Supply

SWAGELOK

75 MM,

80 CM, H MM 01) CAPILLARY

D

Ε

F

F i g u r e 1.

Schematic v i e w o f t h e i n e r t

TUBING

3/8 IN OP '.L/*::s TUBING

T, 3/8 IN

3/8 IN OD COPPER TUBING

C

X 3/8 IN

SWAGELOK UNION, l/k

TUBING

To v a c u u m line

P r e s s u r e control bubbler

JOINT

TUBING

OF MERCURY

system.

12 CM COLUMN

SURGE F LAS Κ

ID O-RING SEAL 12 LITER

15 MM

5 CM, 3/8 IN OD GLASS

SWAGELOK UNION, 3/8 IN

20 CM COLUMN OF MERCURY

gas p u r i f i c a t i o n

L

Κ

J

I

Η

G

I D E N T I F I C A T I O N OF COMPONENTS AND DIMENSIONS

A

IN OD COPPER

From or Ar* source

2

Β

A

N


ο

ex.

Ct

ίο a.

«s.

W

38



6.

The system i s m a i n t a i n e d a t about 12 cm Hg p o s i t i v e p r e s s u r e . I n c o r p o r a t i o n o f a 10 or 12 l i t e r surge f l a s k p e r m i t s t h e f i l l i n g of up to a 2 l i t e r v e s s e l w i t h o u t c r e a t i n g a n e g a t i v e p r e s s u r e (VERBOTEN!) o r h a v i n g t o g r e a t l y i n c r e a s e t h e f l o w r a t e o f gas through t h e p u r i f i e r . The o p t i o n a l N u j o l b u b b l e r assembly p r o v i d e s a q u a l i t a t i v e measure o f f l o w r a t e . A l t h o u g h many groups now use M n O - v e r m i c u l i t e o r s i l i c a g e l as an oxygen scavenger, we f i n d t h a t the s t a n d a r d c o m m e r c i a l l y a v a i l a b l e BASF c a t a l y s t works s a t i s f a c t o r i l y f o r our r e s e a r c h and can be r e g e n e r a t e d a t s u b s t a n t i a l l y lower temperatures than t h e manganese based m a t e r i a l (see réf. 1 pp. 74-80). D e t a i l e d diagrams o f the components of the i n e r t gas p u r i f i c a t i o n system a r e shown i n F i g u r e s 2-5. Although o - r i n g s e a l j o i n t s a r e s p e c i f i e d f o r many c o n n e c t i o n s , we have e x p e r i e n c e d c o n s i d e r a b l y more d i f f i c u l t y (and o c c a s i o n a l a n g u i s h ) i n s e t t i n g up p u r i f i c a t i o n t r a i n s w i t h t h e s e r a t h e r i n f l e x i b l e j o i n t s than w i t h s t a n d a r d ground s p h e r i c a l ( i . e . , b a l l and s o c k e t ) j o i n t s . U n f o r t u n a t e l y , the l a t t e r must be c a r e f u l l y checked f o r warps and hand-lapped i f n e c e s s a r y ; however, i f they a r e l u b r i c a t e d w i t h A p i e z o n H or Τ grease and w e l l matched, c h a n n e l l i n g i s g e n e r a l l y not a problem even a f t e r s e v e r a l y e a r s as l o n g as t h e i n t e r n a l gas p r e s s u r e i s not too g r e a t . Perhaps the b e s t s o l u t i o n would be t o use o - r i n g b a l l j o i n t s ( a v a i l a b l e from Kontes o r Ace G l a s s Co.). These a r e about t w i c e t h e p r i c e of o - r i n g s e a l j o i n t s but have the f l e x i b i l i t y of s p h e r i c a l j o i n t s and the advantage o f o - r i n g s e a l j o i n t s i n t h a t they a r e g r e a s e l e s s , a l t h o u g h a l i g h t c o a t i n g o f A p i e z o n Η o r Τ on the o - r i n g i s recommended. Another d e s i r a b l e s u b s t i t u t i o n f o r our s p e c i f i e d components would be to use g r a p h i t e o r V e s p e l f r o n t f e r r u l e s ( a v a i l a b l e from s u p p l i e r s of chromatography equipment) i n s t e a d of the T e f l o n v a r i e t y f o r g l a s s - m e t a l t u b i n g c o n n e c t i o n s . F e r r u l e s made o f T e f l o n tend t o c o l d - f l o w which o f t e n n e c e s s i t a t e s r e t i g h t e n i n g or r e p l a c i n g of the f e r r u l e a f t e r some time. G r a p h i t e based f e r r u l e s a r e e a s i l y deformed but do not tend t o " c o l d f l o w " . A summary o f t h e s o u r c e s and approximate p r i c e s f o r the compo nents o f the i n e r t gas p u r i f i c a t i o n system i s i n c l u d e d i n T a b l e I . Even a t 1987 p r i c e s , one s h o u l d be a b l e t o assemble one of t h e s e systems f o r l e s s than $1000. A l t h o u g h i t i s not recommended, one p u r i f i c a t i o n l i n e can s e r v e more t h a n one vacuum l i n e . Vacuum-Inert Atmosphere M a n i f o l d F i g u r e 6 d e p i c t s a s i m p l i f i e d f i v e tap v e r s i o n o f our double mani f o l d vacuum l i n e . T h i s assembly i s shown as b e i n g about 5 f e e t l o n g but can be made c o n s i d e r a b l y s h o r t e r as a f o u r tap l i n e and/or i f o n l y one c o l d t r a p i s u s e d . t I n many ways t h e d e s i g n i s s u p e r i o r

tThe l i n e i s a m o d i f i e d v e r s i o n of one Stan Wreford f i r s t assembled as a graduate s t u d e n t i n A l a n Davison's group a t M.I.T. Stan a p p a r e n t l y borrowed t h e d e s i g n from Hans B r i n t z i n g e r s l a b a t the U n i v e r s i t y of M i c h i g a n , where he d i d undergraduate r e s e a r c h . ?



3. ELLIS


IDENTIFICATION A

S . J .

50/30

BALL

Β

35

MM

C

60

MM

D

70-75

MM

OD

Ε

30

MM

ID

ORSJ

F

75

MM

COMPONENTS

AND

JOINT

G

70

CM

H

25

MM

I

80-85

CM

J

70

MM

OD

Κ

50

MM

L

60

MM

OD OD

NOTE:

Figure

OF

2.

FLANGE

ORSJ

=

Oxygen r e m o v a l

O-RING

tower and

SEAL

outer

DIMENSIONS

OD

FLANGE

JOINT

column f o r

thermal

insulation.



20

KONTES

5 CM

C

D

Ε

ORSJ

F i g u r e 3.

K826500,

15 MM OD

Β

CM

15 MM ID

A

NOTE:

MM

OF

CM 50/30

0-** MM

TUBING

SEAL

JOINT

SOCKET

K826500,

= O-RING

S.J.

Κ ORSJ

10

KONTES

2 5 MM

9 MM ID

ORSJ

AND G L A S S

3 5 MM OD

J

I

H

G

F

COMPONENTS

Connection

1

10 MM OD 8 MM OD

Ρ

30 MM ID

6 CM

7 5 MM

Ο

Ν

M

L

DIMENSIONS

Top and bottom component o f oxygen removal tower.

0-8

IDENTIFICATION

A

Rottom

D

TOP Connect ion


ORSJ

w ΝΗ Η »

η η Χ

ΝΗ

>

Η

ο sw

>

Ο

50

Ο

>

w Η

s

S

W


3.

ELLIS

Techniques in the Handling of Highly Reduced Organometallics

Glass wool support

IDENTIFICATION OF COMPONENTS AND GLASS TUBING DIMENSIONS A

3/8 IN COPPER TUBING

G

75 MM

Β

SWAGELOK UNION, 3/8 IN

Η

90 MM OD

C

50 MM; 3/8 IN OD GLASS

I

60 CM

D

50 MM

J

100-110 MM OD FLANGE

Ε

60 MM OD

Κ

10 CM

F

S . J . 75/50 SPHERICAL JOINTS. GREASE WITH APIEZON H OR Τ

L

15 MM ID O-RING SEAL JOINT

F i g u r e 4.

M o l e c u l a r s i e v e tower.


4

1


15

25

50

40

10

A

Β

C

D

Ε

ID

MM O D

MM O D

MM

MM

MM

JOINT

OF

GLASS

J

I

H

G

F

CM

CM

CM

10

MM

EXTRA

10

*»0

25

COMPONENTS

GLASS

DISPERSION

DIMENSIONS

COARSE

AND

N u j o l b u b b l e r assembly o f t h e gas p u r i f i c a t i o n system.

SEAL

F i g u r e 5.

O-RING

IDENTIFICATION


TUBE

Χ

S3

ο 33 w S

>

Μ Η

ο s

>

ο

Ο

>

2 M Ζ Η

w w

X

W


F

G

Double m a n i f o l d

Ν

F i g u r e 6.

2 5 MM

Ç A . 150 CM

M

vacuum l i n e

OD LENGTH

e x c l u d i n g manometers.

TOTAL

MM

MM

MM

K 8 2 6 5 0 0 , 0-4

CM

12 40 25

Ε

HIGH VACUUM, HOLLOW PLUG

KONTES

3 WAY

L

ABOVE J O I N T

4 MM,

MM

S.T. 14/35 INNER J O I N T

10

OD

K

GLASS SPURS,

C

D

150

I

MM

28 MM

H

—>

To a 75-1001/m vacuum Pump

DIMENSIONS

Rg-n

J

75 MM 150 MM

Β

SPHERICAL JOINTS

S.J.

A

35/20

I D E N T I F I C A T I O N OF GLASS COMPONENTS AND

•A


STOPCOCKS

ο

ft.

ft.

to

t

«ο

§: 3'

s>

5*

Co

g

W


44


T a b l e I . Summary of Sources and Approximate Cost f o r Components o f the I n e r t Gas P u r i f i c a t i o n System

1.

Swagelok U n i o n , 1/4 χ 3/8 Cat. No. B600-6-4 @ 2.65

Crawford F i t t i n g Co. 29500 S o l o n Road S o l o n , Ohio 44139

2.65

2.

Swagelok T, 3/8 χ 3/8 χ 3/8 Cat. No. B600-3 @ 6.05

Crawford F i t t i n g Co. 29500 Solon Road S o l o n , Ohio 44139

18.15

3.

Swagelok T e f l o n f r o n t f e r r u l e 3/8 i n . T-603-1 @ 1.06

Crawford F i t t i n g Co. 29500 Solon Road Solon, Ohio 44139

5.30

4.

Swagelok U n i o n 3/8 χ 3/8 Cat. No. B600-6 @ 2.65

Crawford F i t t i n g Co. 29500 Solon Road S o l o n , Ohio 44139

5.30

5.

C a t a l y s t Tower and Outer Column ( F i g u r e 2)

Local f a b r i c a t i o n at 65.00 G l a s s Technology S e r v i c e (Univ. o f M i n n e s o t a )

6.

Top and Bottom C o n n e c t i o n f o r C a t a l y s t Tower ( F i g u r e 3)

Local f a b r i c a t i o n at 183.00 G l a s s Technology S e r v i c e (Univ. o f M i n n e s o t a )

7.

BASF o r R3-11 C a t a l y s t (1 kg)

Chemical Dynamics 42.00 P.O. Box 395 ( o r 28.00/kg South P l a i n f i e l d , NJ f o r 5 kg 07080 unit) (201) 753-5000

Nichrome o r Chromel A Wire (50 f t . , B+S 20 Gauge, c a . 0.65 ohm/ft.)

Any Lab. Apparatus D i s t r i b u t o r such as Sargent Welch

15.00

Molecular

Local Fabrication

80.00

10. M o l e c u l a r S i e v e s , 13X, 4-8 mesh ( c a . 5 l b . )

Fisher S c i e n t i f i c

30.00

11. Surge F l a s k , 12 l i t e r

Local f a b r i c a t i o n

57.00

12. O p t i o n a l N u j o l B u b b l e r Assembly ( F i g u r e 5)

Local fabrication

92.00

13. C a p i l l a r y T u b i n g , 8 mm OD, 2 χ 4ft.

Fisher Scientific

9.

S i e v e Tower ( F i g u r e 4)

8.00

Not i n c l u d e d i n l i s t i s copper and g l a s s t u b i n g , two p r e s s u r e r e l i e f b u b b l e r s , n e e d l e v a l v e f o r c o n t r o l o f t h e s o u r c e g a s , gas r e g u l a t o r , mercury, and power s u p p l y f o r C a t a l y s t Tower. TOTAL ESTIMATED COST (1984-1985 PRICES) OF SYSTEM: $700.00



3.

ELLIS


t o a c o m m e r c i a l l y a v a i l a b l e u n i t from the Ace G l a s s Co. In p a r t i c u l a r , the presence of standard taper o r , a l t e r n a t i v e l y , o - r i n g b a l l c o n n e c t i o n s on each tap p e r m i t the attachment of a r e a c t i o n v e s s e l d i r e c t l y to the vacuum l i n e v i a a g l a s s o r m e t a l a d a p t e r . This pro cedure m i n i m i z e s c o n t a m i n a t i o n problems a s s o c i a t e d w i t h the use of p l a s t i c (e.g. Tygon) or b u t y l r u b b e r t u b i n g . These types of t u b i n g a r e not o n l y permeable t o oxygen and m o i s t u r e but a l s o absorb s o l v e n t v a p o r s which may then combine w i t h r e a c t a n t s or p r o d u c t s . t t F l e x i b l e s t a i n l e s s s t e e l t u b i n g i s e x t r e m e l y u s e f u l when t h e p r e s e n c e of p l a s t i c o r rubber t u b i n g i s u n d e s i r a b l e , y e t c o n s i d e r a b l e f l e x i b i l i t y i s n e c e s s a r y between t h e vacuum l i n e and a p p a r a t u s . The use of f l e x i b l e SS t u b i n g s h o u l d be c o n s i d e r e d f o r any l o n g term o p e r a t i o n s i n v o l v i n g a i r s e n s i t i v e m a t e r i a l s w h i c h must be l e f t open t o a manometer, gaseous r e a c t a n t o r i n e r t atmosphere l i n e . For example, i n F i g u r e 7, a t y p i c a l assembly f o r c o n d u c t i n g a r e a c t i o n under an atmosphere of c a r b o n monoxide i s shown. T h i s a p p a r a t u s has p r o v e n t o be u s e f u l i n the s y n t h e s i s o f e x t r e m e l y a i r s e n s i t i v e m a t e r i a l s such as Ti(C0>3(dmpe) o r C ^ H T i ( C O ) ^ ~ by low t e m p e r a t u r e r e d u c t i v e c a r b o n y l a t i o n s conducted a t near a t m o s p h e r i c p r e s s u r e over a p e r i o d o f 10-12 h o u r s . ( 1 6 ) F l e x i b l e SS t u b i n g i s a l s o p a r t i c u l a r l y u s e f u l f o r s u b l i m a t i o n s conducted under dynamic vacuum c o n d i t i o n s . I n t h i s case U l t r a - T o r r f i t t i n g s s h o u l d be used. F i g u r e 8 shows a c r o s s - s e c t i o n a l v i e w of the vacuum l i n e w h i c h d e t a i l s the manometer d e s i g n . Manometers a r e a t t a c h e d to each vacuum tap t o p e r m i t f a c i l e h a n d l i n g o f gaseous r e a c t a n t s o r low b o i l i n g s o l v e n t s such as l i q u i d ammonia o r d i m e t h y l e t h e r . Mano meters a r e i m p o r t a n t f o r p r e s s u r e measurements p a r t i c u l a r l y d u r i n g reduced p r e s s u r e d i s t i l l a t i o n s . They a r e a l s o e x t r e m e l y u s e f u l f o r c h e c k i n g evacuated a p p a r a t u s f o r l e a k s and f u n c t i o n as s i m p l e p r e s sure r e l i e f v a l v e s f o r ordinary d i s t i l l a t i o n s or r e a c t i o n s i n which gases a r e e v o l v e d . The d e s i g n may be s i m p l i f i e d by h a v i n g one mano meter s e r v e two taps v i a a t h r e e way Τ b o r e s p r i n g loaded s t o p c o c k 2

5

t t A q u a l i t a t i v e i d e a o f the p e r m e a b i l i t y of b u t y l r u b b e r (e.g., F i s h e r 14-168B) o r Tygon vacuum t u b i n g to a i r may be gained by i n i t i a l l y f i l l i n g a meter l e n g t h of t u b i n g w i t h pure argon or n i t r o gen, l e a v i n g the c o n t e n t s u n d i s t u r b e d f o r 12 h o u r s o r more and t h e n f l u s h i n g the gas from the t u b i n g i n t o a v e s s e l c o n t a i n i n g a h i g h l y a i r s e n s i t i v e compound i n s o l u t i o n (e.g., Na-C^QHg i n t e t r a h y d r o f u r a n or chromous c h l o r i d e i n w a t e r ) . I n v a r i a b l y , enough a i r w i l l have d i f f u s e d through t h e t u b i n g w i t h i n t h i s p e r i o d t o cause s i g n i f i cant d e c o m p o s i t i o n of t h e t e s t m a t e r i a l . T h i s o b s e r v a t i o n s h o u l d s e r v e as ample w a r n i n g t o those who use rubber o r p l a s t i c c o n n e c t i o n s between a v a c u u m - i n e r t gas l i n e and r e a c t i o n a p p a r a t u s i n v o l v i n g h i g h l y a i r s e n s i t i v e m a t e r i a l s . The l a t t e r s h o u l d e i t h e r be c l o s e d to t h e t u b i n g , i f l e f t f o r extended p e r i o d s of t i m e , o r connected to the vacuum l i n e by nonpermeable m a t e r i a l s .



9 MM ID O - R I N G

KOVAR-GLASS

SWAGELOK

D

Ε

1/4

IN

1/4

IN OD

JOINT

STOPCOCK

EQUIPPED

OF

50 MM 12

60 MM 1/4

H I J Κ

IN OD

MM OD

7 5 MM

G

COPPER

SS T U B I N G , LENGTH

DIMENSIONS

CAJON 24 IN

AND

F

COMPONENTS

If

IN

TUBING

1/4

F i g u r e 7. Diagram showing t h e u s e of f l e x i b l e s t a i n l e s s s t e e l t u b i n g f o r c o n d u c t i n g r e a c t i o n s under an atmosphere o f c a r b o n monoxide o r o t h e r gas.

UNION,

SEAL,

SEAL

MM T E F L O N

C

0-3

ROTAFLO

Β

90°

TWO NECK R E A C T I O N V E S S E L WITH A 9 0 ° S T O P C O C K

A

IDENTIFICATION

Tap from vacuum line

F r o m the. C O purification system


OD

w

η Χ

ο

>

ο s

>

Ο » Ο

>

Η

I

w

W


3. ELLIS


rnercury

bubbler

F i g u r e 8. C r o s s - s e c t i o n a l view o f t h e vacuum l i n e showing a manometer. Continued on next page.

American Chemical Society Library 1155 16th St., N.W. Washington, D.C. 20036



IDENTIFICATION


COMPONENTS A

25

Β

INERT

C

40

MM

D

12

CM

Ε

50

MM

F

6-12

G

VACUUM

H

10

MM

I

10

CM

J

30

CM

Κ

65

MM

L

9

M

KONTES

Ν

8

DIMENSIONS

MM

MM

GAS

CHAMBER

MM CHAMBER OD

ID

ORSJ K826500,

MM O D

NOTES:

SEE

AND

OF

GLASS

ORSJ

FIGURE

ORIENTATION

0-4

CAPILLARY

= O-RING

10 OF

MM

FOR THE

THE 3

SEAL

JOINT

CORRECT WAY

STOPCOCK

F i g u r e 8.

Continued.



3. ELLIS


w i t h o u t g r e a t l y r e d u c i n g t h e f l e x i b i l i t y o f t h e system. Another v i e w o f t h e manometer i s d e p i c t e d i n F i g u r e 9, w h i c h a l s o shows an o p t i o n a l Nujol bubbler. T h i s b u b b l e r i s sometimes u s e f u l f o r cond u c t i n g o p e r a t i o n s near a t m o s p h e r i c p r e s s u r e o r q u a l i t a t i v e l y d e t e r m i n i n g t h e f l o w r a t e o f t h e i n e r t gas through a t a p b e f o r e opening a f l a s k , e t c . t o t h e atmosphere w i t h a c o u n t e r c u r r e n t o f n i t r o g e n o r argon. I d e a l l y , manometers s h o u l d be f u s e d d i r e c t l y t o t h e vacuum l i n e to minimize the p o s s i b i l i t y of l e a k s , but i n p r a c t i c e t h i s i s i n c o n v e n i e n t when t h e apparatus must be d i s a s s e m b l e d , u n l e s s a competent glassblower i s i n residence. For t h i s reason o - r i n g s e a l , s p h e r i c a l o r o - r i n g b a l l and s o c k e t j o i n t s a r e used i n t h i s connect i o n . We have a l s o t e s t e d t h e somewhat more e x p e n s i v e S o l v - s e a l j o i n t s ( F i s c h e r and P o r t e r Co.) and f i n d t h a t they have no p a r t i c u l a r advantage i n t h i s o r o t h e r a p p l i c a t i o n s . The r e l a t i v e i n f l e x i b i l i t y o f o - r i n g s e a l j o i n t s i s n o t a s e r i o u s problem h e r e . A l t h o u g h Kontes T e f l o n s t o p c o c k s a r e s p e c i f i e d f o r t h e manometers, any h i g h vacuum T e f l o n s t o p c o c k s h o u l d be s a t i s f a c t o r y . F i g u r e 10 d e p i c t s p o s s i b l e o r i e n t a t i o n s o f t h e s t o p c o c k s on t h e vacuum l i n e . Other components of t h e vacuum l i n e a r e i l l u s t r a t e d i n F i g u r e s 11 and 12. The l a r g e bore g l a s s vacuum s t o p c o c k s shown i n F i g u r e 11 may be r e p l a c e d by h i g h vacuum T e f l o n s t o p c o c k s p r o v i d e d t h e i r o - r i n g s a r e f a i r l y i n e r t to solvent vapors. O-rings made o f r e m a r k a b l y i n e r t K a l r e z (Ace G l a s s Co.) can be used but a r e e x t r e m e l y e x p e n s i v e . The m o l e c u l a r s i e v e t r a p shown i n F i g u r e 12 i s p a r t i c u l a r l y u s e f u l i n m i n i m i z i n g c o n t a m i n a t i o n o f t h e i n e r t gas p u r i f i c a t i o n t r a i n by s o l v e n t s o r v o l a t i l e reagents. Such a t r a p , c o o l e d w i t h CO^-iPrOH, i s e s p e c i a l l y i m p o r t a n t whenever r e a c t i o n s i n v o l v i n g l i q u i d ammonia a r e done on t h e l i n e . Ammonia v a p o r c a n e a s i l y b a c k - d i f f u s e i n t o an u n p r o t e c t e d i n e r t gas p u r i f i c a t i o n t r a i n and r u i n much subsequent c h e m i s t r y i f the problem i s n o t d e t e c t e d i n t i m e . F o r t h i s r e a s o n , a l l l i q u i d ammonia c h e m i s t r y i n t h i s l a b o r a t o r y i s g e n e r a l l y done on o n l y one o r two s e l e c t e d benches. C o n t a m i n a t i o n of t h e " i n e r t g a s " by many s u b s t a n c e s can s e r i o u s l y harm experiments conducted on t h e l i n e and must always be suspected when r e a c t i v e m a t e r i a l s decompose o r s l o w l y d i e under m y s t e r i o u s c i r c u m s t a n c e s . Such c o n t a m i n a t i o n can a r i s e from slow r e l e a s e o f absorbed s p e c i e s from a m o l e c u l a r s i e v e column (or t r a p ! ) and/or rubber o r p l a s t i c t u b i n g . The p r e v i o u s l y ment i o n e d tendency f o r such t u b i n g s ( e s p e c i a l l y Tygon) t o s t r o n g l y absorb (and then r e l e a s e ) s o l v e n t v a p o r and m o i s t u r e may be more o f a problem t h a n t h e i r i n h e r e n t p e r m e a b i l i t y t o a i r when u s i n g t h e s e m a t e r i a l s as f l e x i b l e c o n n e c t i o n s on a vacuum l i n e . Even vapor as innocuous as t e t r a h y d r o f u r a n , one o f t h e most commonly used s o l v e n t s i n o r g a n o m e t a l l i c c h e m i s t r y , c a n cause d e c o m p o s i t i o n o f s t r o n g e l e c t r o p h i l e s such as T i C l ^ (which fumes s t r o n g l y i n n i t r o g e n o r a r g o n contaminated by t e t r a h y d r o f u r a n v a p o r ) o r T a C l ^ a t room temperature. I n c l o s i n g t h i s s e c t i o n , a c o n s i d e r a t i o n o f some p r o s and cons of u s i n g a l l g l a s s s t o p c o c k s on a d o u b l e m a n i f o l d vacuum l i n e i s a p p r o p r i a t e , p a r t i c u l a r l y i n v i e w o f Wayda and Dye's r e c e n t d e s i g n


EXPERIMENTAL ORGANOMETALLIC CHEMISTRY E

h~


Nujol

IDENTIFICATION OF COMPONENTS AND DIMENSIONS 25

MM

I

10 CM

20

MM

J

50

MM

KONTES K826500, 0-4 MM

8

MM OD

K

30 CM

MM

L

80 CM

75

9 MM ID ORSJ

M

8 MM OD, CAPILLARY

25

MM OD

Ν

15 CM

25

CM

0

13 CM

NOTE:

Ρ 4 CM COLUMN OF MERCURY ORSJ = O-RING SEAL JOINT

F i g u r e 9. S i d e v i e w o f a manometer and N u j o l b u b b l e r o f t h e vacuum l i n e .

vacuum inert gas

^
y

Left h a n d e d line

X/g-

Right handed

line

F i g u r e 10. Top v i e w o f t h e m a n i f o l d showing p o s s i b l e o r i e n t a t i o n s of t h e s t o p c o c k .




3. ELLIS

IDENTIFICATION AND A

S.J.

Β

50

MM MM OD

35/20

C

20

1 0 MM O B L I Q U E PLUG STOPCOCK

E

S.T. 45/50 JOINTS

F

30

CM

G

20

MM OD

H

50

MM OD

I

10

CM

J

18-20

Κ

S.J.

L

25

COMPONENTS

BALL

D

JOINT

BORE,

GROUND

HOLLOW

GLASS

CM 35/20

SPHERICAL

JOINTS

MM

NOTE : LAR„E C O C K S MAY B E COMPONENT D

F i g u r e 11.

OF

DIMENSIONS

BORE T E F L O N SUBSTITUTED

STOP FOR

C o l d t r a p assembly o f t h e vacuum l i n e .



F r o m gas purification unit


4»

R u g of glass w o o l

IDENTIFICATION AND A

S.J.

OF

COMPONENTS

DIMENSIONS 35/20

BALL

JOINT

Β

15 MM OD

C

50 MM

D

KONTES

Ε

75

MM

F

30

MM

G

50

MM

OD

H

2 5 MM

OD

I

25

MM

J

15

MM

ID

O-RING

SEAL

Κ

SWAGELOK

UNION,

3/8

L

3/8

Figure

IN

12.

K826500,

COPPER

0 - 8 MM

JOINTS IN

TUBING

Molecular

sieve

trap.



3.

ELLIS


w h i c h uses o n l y s t o p c o c k s w i t h T e f l o n p l u g s , (14) Perhaps the p r i n c i p a l advantage i s u s i n g g l a s s s t o p c o c k s r e l a t i v e t o the T e f l o n v a r i e t y i s t h e i r r e s i s t a n c e t o s c r a t c h i n g t and f o u l i n g by bumped s o l u t i o n s , v o l a t i l e s o l i d s , etc. This l a t t e r property i s e s p e c i a l l y i m p o r t a n t w i t h a medium vacuum l i n e on w h i c h s y n t h e s e s and p u r i f i c a t i o n of i n o r g a n i c or o r g a n o m e t a l l i c m a t e r i a l s a r e r o u t i n e l y c a r r i e d out. Almost i n v a r i a b l y , a r a t h e r n a s t y c o n c o c t i o n of d e b r i s f i n d s i t s way through the s t o p c o c k o r i f i c e i n t o the vacuum chamber over a p e r i o d of time. The performance of a T e f l o n s t o p c o c k can be s e r i o u s l y i m p a i r e d under t h e s e c o n d i t i o n s . Another advantage of g l a s s over T e f l o n s t o p c o c k s w i t h r e s p e c t to a d o u b l e m a n i f o l d vacuum l i n e i s t h a t e v a c u a t i o n and r e f i l l o p e r a t i o n s i n v o l v i n g s m a l l volumes a r e conducted more e a s i l y i n one smooth o p e r a t i o n . For example, w i t h the Wayda-Dye l i n e mentioned p r e v i o u s l y ( 1 4 ) , two independent T e f l o n s t o p c o c k s must be m a n i p u l a t e d t o a c h i e v e the same r e s u l t . D i s a d v a n t a g e s i n u s i n g a l l g l a s s i n s t e a d of T e f l o n s t o p c o c k s a r e c o n s i d e r a b l e , the most important o f w h i c h i s u n d o u b t e d l y the r e q u i r e m e n t t h a t they be g r e a s e d . Grease i s o f t e n i n t r i n s i c a l l y troublesome s t u f f t o a p r a c t i c i n g s y n t h e t i c c h e m i s t . I t c h a n n e l s and thereby a l l o w s a i r t o get i n t o the system, c o n t a m i n a t e s o t h e r w i s e pure compounds, o c c a s i o n a l l y r e a c t s w i t h m a t e r i a l s and can be e a s i l y l e a c h e d out of s t o p c o c k s and j o i n t s by s o l v e n t v a p o r . C h a n n e l l i n g can be e s p e c i a l l y p r o b l e m a t i c i f components of a g l a s s s t o p c o c k do not e x a c t l y match. Grease a l s o t r a p s s o l v e n t v a p o r , w h i c h can g r e a t l y d e c r e a s e t h e vacuum of t h e system. Another s i g n i f i c a n t problem w i t h a l l g l a s s vacuum s t o p c o c k s i s t h a t the components a r e g e n e r a l l y not i n t e r c h a n g e a b l e . O f t e n the e n t i r e s t o p cock must be r e p l a c e d i f e i t h e r the b a r r e l or p l u g i s damaged. R e p a i r of vacuum l i n e s c o n t a i n i n g g l a s s s t o p c o c k s can a l s o be more d i f f i c u l t than t h o s e c o n t a i n i n g T e f l o n p l u g s s i n c e the l i n e must g e n e r a l l y be degreased b e f o r e r e p a i r , p a r t i c u l a r l y i f the e n t i r e l i n e i s t o be p l a c e d i n an* a n n e a l i n g oven. Another s e r i o u s problem i s t h a t g l a s s s t o p c o c k b a r r e l s can be e a s i l y warped d u r i n g r e p a i r and/or annealing. G l a s s b l o w e r s a r e not always as c a r e f u l as they s h o u l d be i n r e p a i r s of t h i s s o r t , p a r t i c u l a r l y when the r e p a i r i s made c l o s e t o the b a r r e l o f a s t o p c o c k . Anyone who uses h i g h vacuum g l a s s s t o p cocks should l e a r n how t o hand-lap or r e g r i n d warped ones f o r t h i s reason. By m a s t e r i n g t h i s s i m p l e t e c h n i q u e (which i s d i s c u s s e d i n some d e t a i l on page 163 of r e f e r e n c e 1) many t r i p s t o the g l a s s blower and c o n s i d e r a b l e money can be saved. A f i n a l d i s a d v a n t a g e o f custom ground g l a s s s t o p c o c k s i s one of economics: they a r e c o n s i d e r a b l y more e x p e n s i v e t o manufacture t h a n T e f l o n s t o p c o c k s and the c o s t d i f f e r e n t i a l between t h e s e two items seems t o be s t e a d i l y i n c r e a s i n g . I f t h i s t r e n d c o n t i n u e s , h i g h vacuum g l a s s s t o p c o c k s may be p r i c e d out of the market i n the not too d i s t a n t future. A summary of the approximate p r i c e s f o r t h e components of the d o u b l e m a n i f o l d vacuum l i n e i s shown i n T a b l e I I . A more r e c e n t e s t i m a t e (10/86) from our g l a s s b l o w i n g shop ( l a b o r : $24/hr)

t T h i s i s a s e r i o u s problem w i t h T e f l o n p l u g s , e s p e c i a l l y t h o s e w h i c h do not have r e p l a c e a b l e o - r i n g s , such as ones marketed by C o r n i n g g l a s s ( R o t a - f l o s t o p c o c k s ) and J . Young L t d . of London.



54

i n d i c a t e d t h a t i t s h o u l d be p o s s i b l e t o c o n s t r u c t t h i s double mani f o l d l i n e and a c c e s s o r i e s (items 1-6) f o r about $1500. A l s o shown i s p r i c e i n f o r m a t i o n on t h e f l e x i b l e s t a i n l e s s s t e e l t u b i n g assembly. The t u b i n g and f i t t i n g s a r e a v a i l a b l e from t h e C a j o n Company, 32550 Old South M i l e s Road, S o l o n , Ohio 44139.


Table I I .

Approximate Cost f o r Components o f t h e Vacuum-Inert Gas L i n e

1.

M o l e c u l a r S i e v e Trap i n c l u d i n g 3/8 i n . Swagelok U n i o n

A l l items f a b r i c a t e d $108.00 by G l a s s Tech. S e r v i c e U n i v e r s i t y o f Minnesota

2.

Double M a n i f o l d Vac. L i n e (5 t a p s )

610.00

3.

Manometers (5) @ 57.50 Cost o f t h e system c a n be reduced somewhat by i n c o r p o r a t i n g o n l y 2 o r 3 manometers. However, the system w i l l be a c c o r d i n g l y l e s s f l e x i b l e .

287.00

4.

O p t i o n a l N u j o l Bubblers

118.00

5.

C o l d Trap Assembly i n c l u d i n g t r a p s

6.

G l a s s C o n n e c t i o n t o Vacuum Pump

(2) @ 59.00

160.00 30.00

Not i n c l u d e d i n t o t a l c o s t : F l e x i b l e t u b i n g and c o n n e c t i o n s , vacuum pump, clamps, Dewars and a McLeod gauge. TOTAL ESTIMATED COST (1984-1985 PRICES) OF LINE: 7.

$1,300

F l e x i b l e S t a i n l e s s S t e e l Tubing Assembly a. G l a s s a d a p t o r , 14/35 o u t e r , two 9 mm ID o - r i n g seal joints

18.00

b.

Swagelok U n i o n s , 1/4 χ 1/4 B400-6 @ 1.80

7.20

c.

F l e x i b l e SS t u b i n g , 1/4 OD, 24 i n . 321-4-X-24 @ 58.50

d.

S l e e v e I n s e r t f o r SS t u b i n g 1/4 OD 304-4-XBA @ 2.00

e.

K o v a r - G l a s s S e a l , 1/4 OD @ 10.00

f.

O-ring

117.00

8.00 40.00

S e a l J o i n t s (4) @ 5.00

20.00 Est. Total:

$210.00

S p e c i a l i z e d Glassware and Techniques I n t h i s f i n a l s e c t i o n some o f t h e s p e c i a l i z e d g l a s s w a r e

and t e c h -



3.

ELLIS


n i q u e s we use i n c o n d u c t i n g bench top o r g a n o m e t a l l i c c h e m i s t r y w i l l be r e v i e w e d . I n c l u d e d i n t h i s s e c t i o n w i l l be a d i s c u s s i o n of a low temperature f i l t r a t i o n a p p a r a t u s , s o l v e n t c o l l e c t i o n u n i t , s o l v e n t s t o r a g e f l a s k s and a s i m p l e s i d e arm r e a c t i o n f l a s k w h i c h we now use e x t e n s i v e l y i n our r e s e a r c h . An a p p a r a t u s w h i c h has proven t o be p a r t i c u l a r l y u s e f u l f o r doing l i q u i d ammonia c h e m i s t r y and the f i l t e r i n g of t h e r m a l l y u n s t a b l e o r g a n o m e t a l l i c s i s our low temperature f i l t r a t i o n a p p a r a t u s d e p i c t e d i n F i g u r e 13.(15) T h i s d e s i g n i s not c o m m e r c i a l l y a v a i l a b l e and has the advantage t h a t the c o o l a n t l e v e l extends down i n t o the lower g r o u n d - g l a s s j o i n t . A l t h o u g h we have s p e c i f i e d an a l l g l a s s s t o p c o c k i n the d e s i g n , c l e a r l y s u b s t i t u t i o n of a T e f l o n s t o p c o c k c o u l d be advantageous. A l s o , the top i n n e r j o i n t may be r e p l a c e d by an o u t e r j o i n t w h i c h would f a c i l i t a t e the use of s e p t a . Two d i f f e r e n t s e t o f dimensions a r e i n d i c a t e d . The l a r g e r u n i t i s u s e f u l f o r f i l t e r i n g up t o a l i t e r o f s o l u t i o n , w h i l e the s m a l l e r u n i t i s more convenient f o r the i s o l a t i o n o f s o l i d s a t low t e m p e r a t u r e s . S o l v e n t c o l l e c t i o n u n i t and s o l v e n t s t o r a g e f l a s k s w h i c h we use a r e shown i n F i g u r e s 14 and 15, r e s p e c t i v e l y . Improvements of the s o l v e n t c o l l e c t i o n u n i t over those c o m m e r c i a l l y a v a i l a b l e i n c l u d e the use of vacuum T e f l o n s t o p c o c k s as w e l l as the d i r e c t f u s i o n of a w a t e r c o o l e d condenser (or a l t e r n a t i v e l y , a d r y i c e - a c e t o n e condenser f o r low b o i l i n g s o l v e n t s ) t o a v o i d the use of greased s t a n d a r d t a p e r joints. S u p p l i e r s o f t e n recommend the use o f T e f l o n s l e e v e s o r T e f l o n coated standard taper j o i n t s f o r greaseless a p p l i c a t i o n s , but we have not found these items to be s a t i s f a c t o r i l y vacuum t i g h t . On the top of t h e condensor i s f u s e d a n o t h e r T e f l o n s t o p c o c k w h i c h i s connected v i a a Τ p i e c e t o a mercury b u b b l e r and the vacuum l i n e . A l t h o u g h we p r e f e r a c o m b i n a t i o n of g l a s s and copper t u b i n g i n these c o n n e c t i o n s , b u t y l r u b b e r can be used i f one i s c a r e f u l t o evacuate and r e f i l l s e v e r a l times b e f o r e a d m i t t i n g i n e r t gas i n t o the d i s t i l l a t i o n u n i t . P o s s i b l e improvements i n the d e s i g n of the s o l v e n t c o l l e c t i o n u n i t i n c l u d e the use o f an o - r i n g b a l l j o i n t f o r the s o l v e n t t a k e o f f t a p , w h i c h would p r e v e n t s t o p c o c k g r e a s e c o n t a m i n a t i o n , i n c o r p o r a t i o n of a thermometer w e l l , d i r e c t f u s i o n of a V i g r e u x column t o the s o l v e n t c o l l e c t i o n u n i t and r e p l a c e m e n t of the r i g h t angled T e f l o n s t o p c o c k on the r e s e r v o i r w i t h an Ace G l a s s " F l i c k i t " v a l v e (Andrea Wayda i s thanked f o r t h i s s u g g e s t i o n ) . The l a t t e r would have t o c o n t a i n K a l r e z o - r i n g s t o w i t h s t a n d hot s o l v e n t v a p o r , however. F r e s h l y d i s t i l l e d s o l v e n t can e i t h e r be s t o r e d i n t h e one l i t e r r e s e r v o i r of the c o l l e c t i o n u n i t o r i n a s o l v e n t s t o r a g e f l a s k ( F i g u r e 15). S o l v e n t can be c o n v e n i e n t l y removed by c a n n u l a o r s y r i n g e v i a the r i g h t angled s t o p c o c k a f t e r removal of the T e f l o n p l u g under a c o u n t e r c u r r e n t of n i t r o g e n o r argon (a v a r i e t y of r u b b e r s e p t a w i l l f i t i n o r o v e r t h e b a r r e l s o f these s t o p c o c k s , thus p e r m i t t i n g t r a n s f e r o f the s o l v e n t under p o s i t i v e p r e s s u r e and f a i r l y r i g o r o u s a n a e r o b i c c o n d i t i o n s ) . I n r e c e n t y e a r s , our group has u t i l i z e d even s i m p l e r s o l v e n t s t o r a g e f l a s k s w h i c h a r e e a s i l y made by s e a l i n g a r i g h t a n g l e d T e f l o n s t o p c o c k t o t h e top of round bottom, o r F l o r e n c e f l a s k s ( F i g u r e 16). We have made s i m i l a r c o n t a i n e r s from 15 and 40 ml c o n i c a l shaped graduated c e n t r i f u g e tubes w h i c h a r e p a r t i c u l a r l y u s e f u l f o r s t o r a g e and d i s p e n s i n g o f l i q u i d organop h o s p h i n e s , d e u t e r a t e d s o l v e n t s and o t h e r l i q u i d s under p o s i t i v e




F i g u r e 13. next page.

Low-temperature f i l t r a t i o n a p p a r a t u s . C o n t i n u e d on


3. ELLIS


IDENTIFICATION

OF

COMPONENTS AND

DIMENSIONS


LARGE UNIT

SMALL UNIT

A

11

CM

10

CM

Β

20

CM

20

CM

C

11

CM

10

CM

D

25

MM

25

CM

Ε

40

MM

40

MM

F

70

MM

35

MM OD

G

120

80

MM OD

H

12

MM

12

MM

I

12

MM

12

MM OD

J

8

MM

Κ

4

MM t

L

S.T.

M

STURDY

Ν

60

OD

MM OD

MM

OD ROD

34/45

8

MM

2

MM t

S.T.

GLASS FRIT

30

ROD

24/40

HOOKS MM

FRIT

+NOTE: T H E 2 A N D 4 MM OBLIQUE B O R E VACUUM S T O P C O C K S MAY B E REPLACED WITH TEFLON S T O P C O C K S TO GOOD ADVANTAGE

F i g u r e 13.

Continued.



F i g u r e 14.

Solvent c o l l e c t i o n u n i t .

Continued on next page.



3. ELLIS


A

50

MM

Β

25

MM

C

13

CM

D

15

MM

Ε

KONTES

F

15

G

ACE

H

15-25

I

8

OD

OD K826500,

0-8

MM

CM

MM

NOTES:

8192-03,

0-3

MM

MM OD

1.

EFFICIENT

DRY

CONDENSORS

ARE

ICE

-

J

S.T.

Κ

75

MM

L

12

MM

M

25

MM

Ν

40

MM

Ο

8

Ρ

THERMOMETER

Q

1000

R

O R I E N T A T I O N OF STOPCOCK F WITH R E S P E C T TO THE BOTTOM OF THE R E S E R V O I R TO P E R M I T NEARLY COMPLETE REMOVAL OF SOLVENT WITH A NEEDLE

iPROH

FUSED

24/40

INNER

MM G L A S S

ML

AND/OR

DIRECTLY

ROD WELL

RESERVOIR

WATER

ONTO

COOLED

THE

RESERVOIR. 2.

THE BOTTOM OF THE U N I T IS TO BE CONNECTED BY A S . T . 2 4 / 4 0 J O I N T C A S S H O W N ) OR P R E F E R A B L Y BY D I R E C T F U S I O N TO A 12 INCH V I G R E U X OR S I M I L A R C O L U M N , W H I C H I S C O N N E C T E D T O T H E S O L V E N T P O T BY 24/40 JOINTS.

3.

ONLY

TWO

VIEW

OF

F i g u r e 14.

STOPCOCKS THE

ARE

SHOWN

ON

JOINT

THE

SIDE

UNIT.

Continued.




60

F i g u r e 15.

S o l v e n t s t o r a g e f l a s k . Continued

on next page.


3.

ELLIS


IDENTIFICATION

OF

COMPONENTS


AND

DIMENSIONS

A

75

Β

12-25

MM MM

C

S.T.

24/40

D

ACE

8192-03

Ε

25

MM

F

30

MM

G

40

MM

H

15-20°

I

500-2000

OUTER

OD

ML

NOTE: T H E S I D E ARM STOPCOCK IS O R I E N T E D SO A N E E D L E W I L L REACH TO T H E B O T T O M O F T H E F L A S K WHEN S O L V E N T IS REMOVED

F i g u r e 15.

Continued.

F i g u r e 16. I n e x p e n s i v e s o l v e n t s t o r a g e f l a s k from w h i c h o r o t h e r l i q u i d s a r e d i s p e n s e d by c a n n u l a o r s y r i n g e .


solvent


62


p r e s s u r e and s t r i c t l y a n a e r o b i c c o n d i t i o n s ( F i g u r e 1 7 ) . By employ i n g these v o l u m e t r i c c o n t a i n e r s one can a v o i d t h e use o f s y r i n g e s which o f t e n contaminate reagents. A l s o approximate d e n s i t i e s o f l i q u i d s c a n be e a s i l y determined w i t h t h i s a p p a r a t u s . Although the second s t o p c o c k may seem s u p e r f l u o u s , we have found t h a t t h e T e f l o n s t o p c o c k s used f o r t h e p r i m a r y s e a l o c c a s i o n a l l y p e r m i t s l o w e n t r y of a i r , p a r t i c u l a r l y i f the o - r i n g o r T e f l o n plug i s scratched. Some l i q u i d s a l s o a t t a c k o - r i n g s . F o r t h e s e reasons t h e a l l g l a s s s t o p c o c k ( l u b r i c a t e d w i t h A p i e z o n H o r Τ g r e a s e ) f u n c t i o n s as a u s e f u l "second l i n e o f d e f e n s e " and can be q u i t e i m p o r t a n t i n t h e l o n g term s t o r a g e o f h i g h l y r e a c t i v e l i q u i d s o u t s i d e o f a drybox. Of course t h e b e s t and cheapest method f o r l o n g term s t o r a g e o f r e a c t i v e l i q u i d s i s t o s e a l them i n g l a s s , b u t t h i s method i s n o t always p r a c t i c a l o r c o n v e n i e n t . A p a r t i c u l a r l y u s e f u l and i n e x p e n s i v e r e a c t i o n v e s s e l i s shown i n F i g u r e 18. T h i s i s s i m p l y a s i d e arm, one neck round bottom f l a s k , equipped w i t h a r i g h t a n g l e d T e f l o n s t o p c o c k , so l i q u i d s c a n be added o r removed v i a t h e b a r r e l o f t h e s t o p c o c k as i l l u s t r a t e d i n F i g u r e 19. I n t h i s f a s h i o n one can m i n i m i z e exposure o f an a i r

f-20 Corning 8140 centrifuge tube

F i g u r e 17. C o n i c a l shaped v o l u m e t r i c s t o r a g e v e s s e l f o r a i r sensitive liquids.



3. ELLIS


Front view

F i g u r e 18. stopcock.

Side

view

Reaction v e s s e l incorporating a r i g h t angle

Teflon

Cannula Rotaflo 0-3 mm"

Flexible tubing open to a Nujol or mercury bubbler

Rotaf lo 0-3 mm

Flexible tubjng from the vacuum line.open to a pressurized source of inert gas

F i g u r e 19. I l l u s t r a t i o n showing t h e t r a n s f e r o f a l i q u i d by c a n n u l a from a s t o r a g e f l a s k i n t o t h e r e a c t i o n v e s s e l v i a t h e b a r r e l of t h e r i g h t a n g l e T e f l o n s t o p c o c k .


64


s e n s i t i v e m a t e r i a l t o t h e atmosphere when adding r e a c t a n t s , removing samples f o r IR s p e c t r a , e t c . on t h e bench. I t i s much more l i k e l y t h a t a e r i a l o x i d a t i o n w i l l o c c u r i f t h e sample i s removed v i a t h e 24/40 j o i n t o f t h e f l a s k than from t h e s t o p c o c k b a r r e l . Exposure o f t h e r e a c t i o n m i x t u r e t o s t o p c o c k grease i s a l s o m i n i m i z e d i n t h i s fashion.


C o n c l u d i n g Remarks I n t h i s a r t i c l e I have attempted t o r e v i e w the most i m p o r t a n t a s p e c t s o f apparatus and t e c h n i q u e s used i n o u r l a b o r a t o r y f o r t h e h a n d l i n g o f o r g a n o m e t a l l i c compounds. Very l i t t l e was mentioned c o n c e r n i n g a c t u a l procedures i n c a r r y i n g o u t o r g a n o m e t a l l i c r e a c t i o n s o r t h e p u r i f i c a t i o n o f m a t e r i a l s , which a r e m a t t e r s o f t r e mendous importance. But o t h e r a r t i c l e s i n t h i s volume address t h i s important t o p i c . I n c l o s i n g , however, i t i s perhaps u s e f u l t o s t r e s s t h a t s u c c e s s i n t h e c h a l l e n g i n g , r e w a r d i n g and r a t h e r f a s t paced a r e a o f o r g a n o m e t a l l i c c h e m i s t r y r e q u i r e s more than good equipment, i d e a s and t i m i n g . One must r e g u l a r l y r e a d t h e c u r r e n t l i t e r a t u r e , ( e x p e r i m e n t a l s e c t i o n s c a n be e s p e c i a l l y h e l p f u l ) , have a s t r o n g work e t h i c and develop e x c e l l e n t l a b o r a t o r y t e c h n i q u e . I t i s a l s o i m p o r t a n t t o be p e r s i s t e n t , r e s i l i e n t , and have a h e a l t h y measure o f d e d i c a t i o n and f a i t h t h a t t h e e f f o r t i s w o r t h w h i l e ! Acknowledgements The N a t i o n a l S c i e n c e F o u n d a t i o n and P e t r o l e u m Research Fund, admini s t e r e d by the American Chemical S o c i e t y , have g e n e r o u s l y p r o v i d e d f i n a n c i a l a s s i s t a n c e f o r r e s e a r c h which d i r e c t l y l e d t o t h e development o r t e s t i n g o f many o f t h e t e c h n i q u e s d i s c u s s e d h e r e i n . I am a l s o v e r y g r a t e f u l t o many d e d i c a t e d co-workers who have h e l p e d over a p e r i o d o f s e v e r a l y e a r s i n t h e d e s i g n and t e s t i n g o f a p p a r a t u s . Andrea Wayda i s acknowledged f o r many h e l p f u l d i s c u s s i o n s o f t e c h n i q u e s i n o r g a n o m e t a l l i c c h e m i s t r y as w e l l as h e r n o t so g e n t l e p r o d d i n g t o f i n i s h t h i s a r t i c l e ! A l s o , a s i n c e r e thank you t o P r o f e s s o r Du S h r i v e r f o r h i s e x t r e m e l y u s e f u l book, "The M a n i p u l a t i o n o f A i r S e n s i t i v e Compounds", w h i c h has s e r v e d me w e l l f o r many y e a r s and remains a g o l d mine o f i n f o r m a t i o n f o r a l l concerned i n this field. F i n a l l y , I would l i k e t o acknowledge my former a d v i s o r , P r o f e s s o r A l a n D a v i s o n , who s t r o n g l y encouraged a c r e a t i v e and i m p r o v i s a t i o n a l approach t o o r g a n o m e t a l l i c and i n o r g a n i c c h e m i s t r y .

Literature Cited 1. 2. 3.

Shriver, D.F.; Drezdzon, M.A. The Manipulation of Air Sensitive Compounds; 2nd Edition; Wiley-Interscience: New York, 1986. Brauer, G., Ed. Handbook of Preparative Inorganic Chemistry; 2nd Edition; Academic Press: New York, 1963; Vol. 1 and 2. Dodd R.E.; Robinson, P.L. Experimental Inorganic Chemistry; Elsevier: Amsterdam, 1957.


3. ELLIS

4. 5. 6. 7.


8. 9. 10. 11. 12. 13. 14. 15. 16.


Eisch, J.J.; King, R.B. Organometallic Syntheses; Academic Press: New York, 1965, Vol. 1; 1981, Vol. 2. Jolly, W.L., The Synthesis and Characterization of Inorganic Compounds ; Prentice-Hall: New York, p. 170. Yamamoto, A. Organotransition Metal Chemistry; Wiley-Inter science: New York, 1986; Ch. 5. Herzog, S; Dehnert, J.; Luhder, K. In Technique of Inorganic Chemistry; Johassen, H.B. Ed.; Interscience-Wiley: New York, 1968; Vol. 7, pp. 119-149. DeLiefde Meijer, H . J . ; Janssen, J.J.; Van Der Kerk, G.J.M. Studies in the Organic Chemistry of Vanadium; Institute for Organic Chemistry T.N.O.: Utrecht, Netherlands, 1963; pp. 41-58. Kramer, G.W.; Levy, A.B.; Midland, M.M. In Organic Syntheses Via Boranes, Brown, H.C., Ed.; J . Wiley and Sons: New York, 1975, Ch. 9. Burlicht, J . How to Use Ace No-air Glassware; Ace Glass Inc.: Vineland, New Jersey, 1970; Pamphlet No. 570. Lane, C.F.; Kramer, G.W. Aldrichim. Acta 1977, 10, 11 (Aldrich Chemical Co. Periodical). Gill, G.B.; Whiting, D.A. Aldrichim. Acta 1986, 19, 31. Handbook of Compressed Gases, Compressed Gas Association, Van Nostrand Reinhold: New York, 1981. Wayda, A . L . ; Dye, J.L.; J. Chem. Ed., 1985, 62, 356 Warnock, G.F.P.; Ellis, J . E . , J . Am. Chem. Soc., 1984, 106, 5016 and references cited therein. Kelsey, B.A.; Ellis, J . E . ; J . Am. Chem. Soc., 1986, 108, 1344; Chi, K.M.; Frerichs, S.R.; Stein, B.K.; Blackburn, D.W.; Ellis, J . E . ; submitted for publication.

RECEIVED

July 31,

1987


Chapter 3: Application 1

Preparation and Isolation of Crystalline Samples Using Low-Temperature Solution Techniques


Malcolm H . Chisholm and David L. Clark Department of Chemistry, Indiana University, Bloomington, IN 47405

Attached is a schematic drawing (Fig. 1) of a low-temperature reaction vessel for the high yield preparation and isolation of thermally unstable compounds. The dimensions of a typical reaction vessel are summarized in a). The Kontes valve may either be sealed directly to the glass, or connected via Tygon tubing depending on the air sensitivity of the materials used. The reactant solution is placed on the frit, and the Kontes valve closed under nitrogen. The closed end of the vessel is then immersed in liquid nitrogen just below the f r i t as shown in b). This provides the vacuum to pull the solution through the f r i t and into the closed end of the vessel where it is frozen at -196°C. The volatile reactant is then condensed into the vessel, and the vessel sealed with a torch as indicated in b). The vessel may then be warmed to the desired reaction temperature and ultimately cooled to -78°C in a Dewar of dry ice as shown in c). This procedure obviously mandates the use of a solvent such as toluene to avoid freezing at this temperature. Ideally, crystals w i l l grow at -78°C as indicated in c). When crystals are present, the vessel is inverted, and placed in liquid nitrogen just below the constriction to pull the f i l t r a t e solution into the receiving bulb. This procedure w i l l deposit crystals on the frit. The vessel is then sealed at thé constriction leaving the f i l t r a t e in the bulb and crystals in a fritted ampule as shown in d). Caution: care should be used to get a uniform and tempered seal i n step b) to avoid cracking when immersing i n l i q u i d nitrogen. RECEIVED

August 13,

1987

0097-6156/87/0357-066$06.00/0

© 1987 American Chemical Society



a)

15mm

b)

reactant solution

crystals!

c)

i4P

Λ Dewar

sealed glass

frozen filtrate

crystals

F i g u r e 1. Schematic drawing o f a low-temperature r e a c t i o n v e s s e l f o r the h i g h y i e l d p r e p a r a t i o n and i s o l a t i o n o f t h e r m a l l y u n s t a b l e compounds.

Dewar

Kontes valve

frozen solution

porous ^.fritted disk

2cm

^


1

ο

I

g

5'

I

ο

ο

a.

Ο

>

ο

ο

X

η X


Recrystallization Apparatus for Air-Sensitive Compounds Alan E . Friedman and Peter C. Ford


Department of Chemistry, University of California, Santa Barbara, CA 93106

Described here is a crystallization apparatus that uses vapor transfer as the method of slowly exchanging the solvents. This technique allows small quantities of air and moisture sensitive organometallic complexes to be crystallized easily under an inert atmosphere to give X-ray diffraction quality crystals. A Schlenk tube (Figure 1) is modified so that a deep dish sample v i a l can be easily placed inside in a small glass cup to provide s t a b i l i t y . For convenience a ring-like glass handle is placed on the sample v i a l to assist in i t s removal once crystals have formed. The 24/40 stopper of the Schlenk tube is also altered with a hook placed on the inside to hoist the sample v i a l . Lastly, a syringe port is set on the side of the Schlenk tube to provide access to both the outside and inside of the sample v i a l . A recrystallization is accomplished by placing a sample of the solid material into the sample v i a l which is then placed into the Schlenk tube. The Schlenk tube is evacuated and/or flushed with the appropriate oxygen free gas by several pump/fill cycles. A minimum of degassed solvent in which the sample is soluble is then added to the sample v i a l via syringe techniques through the septum covering the syringe port. A second degassed solvent, in which the sample is known to be insoluble, is then placed i n the outside part of the Schlenk tube so that gaseous diffusion from the outside to the sample containing v i a l can occur. After a few days crystals w i l l begin to form. For materials that are thermally sensitive the apparatus may be placed i n a refrigerator or freezer during this time. Use of this apparatus may be modified for assembly within a dry box. The advantage of this technique over similar methods is the compactness of the apparatus allowing i t to be oven dried and i t s convenience for use with vacuum lines and syringe techniques. Another advantage is the relative convenience by which crystals can be removed from the v i a l . One main limitation is the small size of the inner v i a l which may overflow i f the "outer" solvent is the more volatile of the two. RECEIVED July 31, 1987 0097-6156/87/0357-0068$06.00/0

© 1987 American Chemical Society



3.2

FRIEDMAN AND FORD

Recrystallization Apparatus

69

F i g u r e 1. C r y s t a l l i z a t i o n A p p a r a t u s : The h o l l o w 24/40 s t o p p e r i s f i t t e d w i t h a hook t h a t extends 5 cm below t o the r i n g o f the 1 cm sample v i a l . The s y r i n g e p o r t i s made from 7 mm t u b i n g w h i l e a 2 mm h o l l o w p l u g , h i g h vacuum s t o p c o c k i s u s e d on the sidearm. The d i a m e t e r o f the main body i s 3.5 cm w h i l e the o v e r a l l l e n g t h i s 20 cm.



Inert Atmosphere Apparatus for U V Photochemical Reactions William C. Trogler


Department of Chemistry, D-006, University of California at San Diego, La Jolla, CA 92093

Small (1-5 g) scale UV photolysis of air sensitive compounds can be performed in quartz Schlenk tubes, or in conventional Schlenkware with the use of a UV transparent quartz stopper. The latter apparatus is easily adapted to low temperature irradiations. Large scale (10-50 g) UV photochemical reactions use quartz immersion well reactors. Medium pressure Hg-arc lamps are the preferred radiation sources for synthetic applications. This report summarizes conventional methods for UV irradiation of air sensitive organometallic compounds at ambient or subambient temperatures. Of the irradiation sources available (V) the medium pressure Hanovia 450 W arc lamp systems (2) are of moderate price, reliable, and versatile in our experience. Caution: Powerful arc lamps can cause eye damage or blindness within seconds and UV pro tective goggles (available from most scientific supply houses) must be worn. Never look directly at the radiation source. For safety of other workers lamps should be enclosed i n a vented box with baffles. If Pyrex transmits enough UV radiation for an efficient reaction, as for photochemical reactions of metal-metal bonded complexes (3)» then conventional Schlenkware can be used for photolysis and no special glassware is needed. Since a 2 mm thick wall of Pyrex transmits only 10$ of the UV light at 300 nm, UV transparent quartz reaction vessels are often needed for photoreactions of mononuclear organometallic complexes. Quartz Schlenk tubes are inexpensive if made from standard quartz tubing closed at one end, and attached to a graded seal. The desired stopcock and joint are attached to the Pyrex end of the seal. Stock tubing and seals with 1 cm I.D. to 3-1/2 inch I.D. are available commercially (4). Although the curved surface of a quartz tube reflects much light, the apparatus is effective for moderate scale reactions (

Techniques in the Handling of Highly Reduced ... - ACS Publications

Recommend Documents