tris(l-propylenediamine)cobalt(lIl) chloride.

In document Stereospecific effects of asymmetric ligands in cobalt (III) complexes (Page 96-100)

3 + Fig 5.22 Rotatory Dispersion Curves? (l) L[Co(l-pn)3 ]v^ ;

L- tris(l-propylenediamine)cobalt(lIl) chloride.

Ethylenediamine (3.58ml, 0.90g/ml.), 1-propylenediamine (26.1ml, 0.304g/ml.) and hydrochloric acid (53.62ml, 1.00N) were added to a solution of cobalt(ll) chloride hexahydrate (l2.75g) in water (150ml). Activated charcoal (5g.) was added and air was bubbled through the mixture for 24hrs. After the charcoal had been filtered off and washed till the washings were colourless, hydrochloric acid (10ml,

3N) was added and the solution evaporated at 70° to a very small volume. Ethanol (300ml.) was added and the precipitated product collected at the pump, washed with ethanol and acetone and dried at 60°. The yield was 18.1g (90%)•

A chromatographic column (3M diameter) was prepared using cellulose (500g.) and water-saturated n-butanol. A small amount

(l.5g.) of the above reaction product was applied to the column in solution in a mixture of water-saturated n-butanol (400ml.) and diy n-butanol (200ml.) and developed with water-saturated n-butanol/ ION hydrochloric acid (97.5/2.5). Suction was applied at the bottom of the column to maintain a steady rate of flow. Four bands

appeared and were collected separately. The entire reaction product was treated in this way. Ihe complex chlorides were extracted

from the butanol solution by shaking with several lots (50ml. ea.) of water, until no more colour remained in the butanol. These aqueous extracts were evaporated almost to diyness on a steam-bath under a stresm of air, and ethanol added to precipitate the products.

The f i r s t band o f f th e column had [ a ]

5893 -4 0 °, [a 1*461 * -2 8 8 °, which v a lu e s in c r e a s e d to -4 4 ° and -306°

r e s p e c t i v e l y on b e in g re-chrom atogram m ed. (The l a s t t h r e e bands were r e s e r v e d f o r f u r t h e r stu d y )*

When th e [ C o (l- p n )3 ]C l3 r e a c t i o n m ix tu r e , p re p a re d by th e

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m ethod o f Dwyer and h i s cow orkers , was chrom atographed on a c e l l u l o s e column d ev elo p ed w ith n -b u ta n o l/w a te r/lO N h y d r o c h lo r ic a c id (60*10*30), two f r a c t i o n s s e p a r a te d , th e f i r s t and l a r g e s t o f which had [a ], -4 6 ° and [a ], -294 . Com parison o f th e f i r s t band o f th e above ch ro m a to g ra p h ic s e p a r a tio n w ith t h i s compound on a p a p e r chrom atogram u s in g th e same s o lv e n t showed them t o be i d e n t i c a l (F ig* 5*21)* 2he r o t a t o r y d i s p e r s i o n curve was p re p a re d f o r a 0*1^4 s o l u t i o n ( F ig . 5*22).

A n aly ses f o r [Co (C gH ^N gJ^JC l^

C H N

C a lc u la te d * 27*88 7 .8 0 21.68 Found! 27.91 7 .8 7 21.38

L - E th y le n e d ia m in e b is ( l- p r o p y le n e d ia m in e ) c o b a lt( ill) c h lo r id e 2 - h y d r a te . The second band o f f th e column ( [ a ] = -6 8 ° , [a ] 54g-j. * -2 2 4 ° , [ a ] 5780 * -9 4 ° ) was re -c h ro m a to g r araned u n d e r th e o r i g i n a l c o n d itio n s , a sm all f o r e - r u n d is c a r d e d , and -the m ain band c o l l e c t e d a s b e f o r e ,

[ a ] 58g 3 ° -7 0 ° , [ a ] ^ ^ = -3 2 2 ° . T h is p ro d u c t ( l .6 1 g ) was shaken i n w a te r (30m l, 50°) w ith s i l v e r 1 - t a r t r a t e ( l .5 0 g ) f o r lO m ins. The s i l v e r c h lo r id e was f i l t e r e d o f f and th e volume re d u c ed to 5m l. when th e d ia s te r e o is o m e r p r e c i p i t a t e d , was c o l l e c t e d a t th e pump and

washed with ice-water (lml). This moist product was dissolved in ION hydrochloric acid (lml.) and evaporated at 70° until a crust formed. Ethanol was added to precipitate the LfCo^-pn^enJClg.SHgO, and the first fraction - [ttjgggg =-76°, “ -336°,

[a] * -100° - was the purest. It was dried at 100° under vacuum and its rotatory dispersion curve prepared using a 0.1$?

aqueous solution (Fig. 5*23).

The ratio of ethylenediamine to 1 -propylenediamine in this

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compound was determined by the method of Dwyer, Garvan and Shulman . The compound (0.5g) was decomposed by heating with sodium sulphide

(2g), potassium hydroxide (0.4g) and sodium hydroxide (5g), and the liberated diamine extracted into benzene (3 lots, 7ml each) which was filtered, dried overnight over potassium hydroxide pellets, and

again filtered. It was titrated against standard hydrochloric acid using methyl orange, and its rotation measured in a 2dm. tube. From the value [a]

5893 -34.4 for pure 1-propylenediamine, the ratio en/l-pn was calculated as l/2.

Analyses for [ C o t C g H ^ N g ^ C g H g N g ) J O l ^ O

C H N

Calculateds 23.47 7.82 20.54

Founds 23.63 7.52 20.36

L-Bis(ethylenediamine)l-propylenediaminecobalt(lIl)chloride 1. hydrate. The third fraction off the column ([a l5fcl9^ * -103°, ■ -360°) (l.23g) was shaken with silver 1-tartrate (l.l8g) in water (20ml)

filtrate evaporated to 5ml. and cooled to give a fraction which, on treatment with hydrochloric acid (3ml, ION), precipitation

with ethanol, collection on a suction filter and washing with ethanol,

had rotations ■ -110°, “ -370° for a 0*E$ aqueous

solution in a 1dm. tube* Further fractions had lower rotations. The ethylenediamine/l-propylenediamine ratio was determined as above *

For the benzene solution

0*5893 * "0 *30° 111 a 2dm* tube* 5ml# m 14*85ml. l.OON nitric acid

whence en/l-pn = 1.92/^ ( ~ 2/^).

The rotatory dispersion curve for a 0*1^ solution of this compound is shown in Fig. 5*24*

Analyses for [CoCCgH^Ng) ( C ^ g N ^ l C l ^ g O

C H N

Calculated* 22.25 7*47 22.25

Found j 22*50 7.29 22.66

I)-Tris(l-propylenediamine)cobalt(lIl)chloride 0.5 hydrate.

The fourth and last fraction from the column was subjected to further separation on a Whatman 3mm# paper sheet. A saturated aqueous solution of the mixture was applied as a thin band and developed, using n-butanol/water/concentrated perchloric acid

(70320*10), into four bands which were cut off and extracted quantitatively into water. The three slowest moving bands were

reserved for further study* The first band was dissolved in exactly

Its rotations a 5fc,g3 - 40.18°, & 5461 ■ 40.32°, gave [m ]5893 » 41540° and [M]5461 - 42740°•

When the fairly pure D [Co(l-pn)3 ]l3 separated hy Dwyer, Garvan

22

and Shulman , was developed on a 3” diameter cellulose column with water-saturated n-butanol/lON hydrochloric acid (97.5/2.5) the majority of the mixture ran in the second hand which was eluted in the usual way, isolated, recrystallised from water-acetone, collected at the pump, washed with acetone and air-dried. For this compound

[m ]56q3 * 41580°, ■ 42960, which is in good agreement with the above measurements. Rirthennore when a spot of this isomer was run on the paper chromatogram described above it remained level with the fastest moving band. The rotatory dispersion curve of this chloride was prepared using a 0.1^ solution (Fig. 5.22).

Analyses for [Co(C3H 1C)N 2 )3 ]Cl3 0.5 HgO

C H N

Calculatedi 27.25 7.88 21.20

Found: 27.44 8.08 21.14

P-Ethylenediaminebi8(1-propylenediamine)cobalt(III)perchlorate l.hydrate.

In document Stereospecific effects of asymmetric ligands in cobalt (III) complexes (Page 96-100)