IN CHEMISTRY Submitted to the Graduate Faculty of Texas

THE THERMAL MATRIX REACTION OF SOME

TRIS(DIAMINE)CHROMIUM(III)

COMPLEXES

by

LARRY KAY SVEUM, B . S .

A THESIS

IN

CHEMISTRY

Submitted to the Graduate Faculty of Texas Technological College

in Partial Fulfillment of the Requirements for

the Degree of

MASTER OF SCIENCE

/IC

ACKNOWLEDGMENT

I am deeply indebted to Professor Wesley W.

Wendlandt for his direction of this work, and to the

other members of the committee, Professors Robert G.

Rekers and Gordon Fuller for their helpful criticism.

Appreciation is gratefully acknowledged to the

United States Air Force Office of Molecular Research

for its financial support of this research.

ii

TABLE OF CONTENTS

Page

ACKNOWLEDGMENT ii

LIST OF TABLES v

LIST OF FIGURES vi Chapter

I. STATEMENT OF THE PROBLEM I

II. REVIEW OF THE LITERATURE 3

III. EXPERIMENTAL METHODS 8

M a t e r i a l s 8 Methods of Prepara t ion of Complexes . . . . 9

I , 2 -Ethaned iamine Complexes of Ghromium(lII) S a l t s 9

I ,2 -Propanediamine Complexes of Ghromium(lII) 10

1 ,3-Propanediamine Complexes of Chromium(III) 12

Methods of A n a l y s i s 15 A n a l y s i s f o r Chromium Content 15 A n a l y s i s f o r H a l i d e and

Thiocyanate Contents 15 A n a l y s i s f o r N i t r o g e n Content 15

Ins t rumenta l Methods 16 Vacuum Thermogravimetric S t u d i e s 16 R e f l e c t a n c e S p e c t r o s c o p y S t u d i e s 16

Matr ix S t u d i e s 16

IV. EXPERIMENTAL RESULTS AND DISCUSSION

A n a l y t i c a l R e s u l t s . . . . 2 l R e s u l t s of t h e Study of the

T r i s ( l , 2 - e t h a n e d i a m i n e ) C h r o m i u m ( I I I ) Compounds 21

R e s u l t s of t h e Study o f the T r i s ( 1 , 2 - p r o p a n e d i a m i n e ) C h r o m i u m ( I I I ) Compounds • 31

Lii

iv

Chapter * Page

Results of the Study of the Tris(l,3-propanediamine)Chromium(IIl) Compounds 40

Results of the Reaction Mechanism Study . . . 47

V. CONCLUSION AND SUMMARY 60

LIST OF REFERENCES 62

LIST OF TABLES

Table Page

1. Analysis of Tris(Diamine)Chromium(III) Compounds 22

2. Minimum Volatilization Temperatures of Ammonium S a l t s 28

3 . Resul t s of Heating Matrices of T r i s -(I,2-Ethanediamine)Chromium(III) Compounds and Ammonium Salts . • • • . . • 30

4. Temperature and Time Required to Purify the Bis(I,2-Ethanediamine) Compounds 32

5. Analysis of the Bis(I,2-Ethanediamine) Compounds 34

6. Results of Heating Matrices of Tris(l,2-Propanediamine)Chromium(lII) Compounds with Ammonium Salts 35

7. Temperature and Time Required to Purify the Bis(l,2-Propanediamine) Compounds . . . 45

8 . Analys i s of Bis( l ,2-Propanediamine) Compounds 46

9. Results of Heating Matrices of Tris(I,3-Propanediamine)Chromium(III) Compounds with Ammonium Salts . . . . . . . 48

10. Temperature and Time Required to Purify the Bis(1,3-Propanediamine) Compounds 49

1 1 . Analys i s of Bis(I ,3-Propanediamine) Compounds 50

12 . Reaction of [Cr(en)3] l3 with Various Matrix Compounds 52

LIST OF FIGURES

Figure Page

1. Apparatus Used to React and Purify the Matrix Mixture 19

2 . Vacuum Thermogravimetric Curves of Various Ammonium Salts . . . . . . . . . 23

3 . Vacuum Thermogravimetric Curves of Various Ammonium Salts 25

4. Reflectance Spectra of Various (I,2-ethanediamine)Chromium(III) Compounds 36

5. Reflectance Spectra of Various (l,2-ethanediamine)Chromium(IIl) Compounds 38

6. Reflectance Spectra of Various (l,2-propanediamine)Chromium(HI) Compounds 41

7 . Ref lec tance Spectra of Various Bis(l ,2-propanediamine)Chromium(III) Compounds . . • • • 4 3

8 . Ref l ec tance Spectra of Various (l ,3-propanediamine)Chromium(III) Compounds • 53

9 . Proposed Mechanism for the Thermal Matrix React ion 36

10. Mass Spectrometer Cinrve of M/e of l7 Versus Temperature 58

v i

CHAPTER I

STATEMENT OF THE PROBLEM

Chromium(III) salts form a series of complexes

with I,2-ethanediamine, 1,2-propanediamine, and l,3-propane<

diamine of formulas, CCr(en)3]X3, rCr(pn)3J X3, and

rCr(tn)3]X3, (where X = various anions, en = 1,2-ethane-

diamine, pn = 1,2-propanediamine, and tn = 1,3-propane-

diamine)• When these complexes are heated in air, the

tris(I,2-ethanediamine)chromium(III) and tris(1,2-

propanediamine) chromium(III) complexes containing chloride

and thiocyanate anions undergo a deamination reaction to

form the bis(diamine) complexes of the formulas,

CCr(en)2X2]X and CCr(pn)2X2]X, (X = Cl" and SON"). The

complexes containing chloride anions form the cis-isomer

while the complexes containing thiocyanate anions form

the trans-isomer.

However, if a mixture of an ammonium salt and the

tris(l,2-ethanediamine)chromium(III) complexes are heated,

the bis(diamine) complexes of the formula, cis-

CCr(en)2X2]X (X = F", Cl", SCN", Br") are obtained. The

order of ease of substitution of halogen for I,2-ethane

diamine is: F">SCN">Cl">Br". This order holds regardless

of wtiether the anion was a part of the complex or of the

ammonium s a l t .

The purpose of th i s invest igat ion i s to study the

p o s s i b i l i t y of devising a method for preparing pure

£iS-CCr(en)2X2Jx,(X = various anions) , by u t i l i z i n g the

s o l i d s t a t e deamination reaction of [Cr(en)3lY3 complexes

(Y = Cl", SCN", Br", or I") in the presence of a s o l i d -

s ta te matrix of the ammonium s a l t . The matrix deamination

of t r i s (1,2-propanediamine)chromium(III) and tr i s ( l ,3 -pro«

panediamine)ciiromium(IIl) complexes and the possible

appl icat ion of th i s method to the preparation of several

bis(diamine)chromium(III) complexes of 1,2-propanediamine

and I,3-propanediamine were a lso to be invest igated .

CHAPTER II

REVIEW OF THE LITERATURE

In 1904, Pfeiffer and co-workers(1,2) first pre

pared the I,2-ethanediamine complexes of chromium(IIl).

They found tl at prolonged heating of tris(l,2-ethane

diamine) chromium( III) chloride at 160°C and of tris-

(l,2-ethanediamine)chromi\im(III) thiocyanate at 130^0

caused a loss of one mole of I,2-ethanediamine per mole

of complex and concommitant rearrangement to form cis-

[Cr(en)2Cl23Cl and trans-CCr(en)2(SCN)2lsCN, respectively.

Rollinson and Bailar(3), in 1944, attempted to re

peat the work of Pfeiffer and found that regardless of the «

experimental conditions, such as heating periods of as

long as one month, temperatures from 160^C to 220* C, and

the use of surface extenders, tris(1,2-ethanediamine)-

chromium(IIl) chloride did not yield cis-[Cr(en)2 CI2] Cl

although tris(l,2-ethanediamine)chromium(III) thiocyanate

deaminated and rearranged to trans-fCr(en)9(SCN)2^SCN.

Upon examination of their preparation schemes, the authors

discovered one difference in the procedures used. In the

preparation of tri8(I,2-ethanediamine)chromium(III) thio

cyanate, Rollinson and Bailar reacted ammonium thiocyanate

with tris(1,2-ethanediamine)chromium(III) sulfate, while

3

their preparation of tris(I,2-ethanediamine)chromium(III)

chloride involved the reaction of I,2-ethanediamine with

anhydrous chromium(lll) chloride. Pfeiffer, et al (1,2),

on the other hand, prepared both compounds by reacting

ammonium chloride or ammonium thiocyanate with tris(I,2-

ethanediamine)chromium(III) sulfate to obtain tris(l,2-

ethanediamine)chromium(III) chloride and tris(l,2-

ethanediamine)chromium(III) thiocyanate, respectively.

Rollinson and Bailar then heated a sample of tris(1,2-

ethanediamin^hromium(lll) chloride contaminated with a

small amount of ammonium chloride and within a short heat

ing period obtained the compound, cis-CCr(en)2Cl23Cl. They

concluded that the thermal deamination of tris(l,2-ethane-

diaminebhromium(III) chloride was catalyzed by traces of

ammonium chloride while the deamination of tris(I,2-ethane

diamine) chromium( III) thiocyanate was catalyzed by ammonium

thiocyanate. By further work, Rollinson and Bailar deter

mined that the most favorable temperatures for the deamina

tion reactions were 210®C and 140°C for the tris(l,2-

ethanediamine)chromium(III) chloride and tris(I,2-ethane

diamine) chromium( I II) thiocyanate, respectively.

Later, O'Brien and Bailar(4) prepared the tris-

(I,2-ethanediamine)chromium(III) complexes in which the

anions were chloride, bromide, thiocyanate, nitrite, nitrate,

cyanate, cyanide, sulfate and oxalate, and the tris(1,2-

propanediamine )chromium( III) complexes in which the anions

were chloride, bromide, iodide and thiocyanate. They

found that only the chloride and thiocyanate complexes of

the two diamines thermally deaminated to yield the bis-

(diamine) complexes upon extensive heating, even in the

presence of the ammonium salt of the corresponding anion.

They obtained the cis-isomer with the chloride complexes

while the trans-isomer was obtained with the thiocyanate

complexes. They found the reaction temperature for the

deamination of tris (1,2-pro pane diamine) chromium (I II) chlo

ride to be 175®C and that of tris(1,2-propanediamine)

chromium(III) thiocyanate to be 110°C.

Rock(5) thoroughly investigated the thermal deami

nation of tris(I,2-ethanediamine)chromium(III) chloride

and found that the actual catalyst for the deamination was

I,2-ethanediamine dihydrochloride which was formed by the

reaction of ammonium chloride with the first molecules of

I,2-ethanediamine evolved by the complex. Also, he found

that oxidation of the complex was a competing reaction un

less steps were taken to remove oxygen or air from the

system. He carried out the thermal deamination reaction

while passing nitrogen gas and/or steam through the system

or by refluxing the material in an inert organic solvent.

The evolved 1,2-ethanediamine was caught in a Barrett trap.

In 1961, Bear and Wendlandt(6) investigated the

thermal dissociation of tris(I,2-ethanediamine)chromium-

III) chloride and thiocyanate and tris(1,2-propanediamine)

chromium(III) chloride and thiocyanate by thermogravi

metric analysis(TGA)(in air) and differential thermal

analysis(DTA) (in helium). They studied the effect of

catalytic amounts of the ammonium halides and ammonium

thiocyanate on the kinetics of the thermal deamination of

the tris(I,2-ethanediamine) and tris(I,2-propanediamine)-

chromium(lll) complexes. In each case, the activation en

ergy was lower in the presence of the ammonium salt of

the corresponding anion. From these data they found that

one mole of I,2-ethanediamine was lost per mole of complex,

which was followed by decomposition to the metal oxide.

Bear(7) also investigated the dissociation of the tris

(l,3-propanediamine)chromium(III) complexes. He detected

no intermediates in the decomposition of the anhydrous

complexes to the oxide, Cr203.

In 1965, Wendlandt and Stembridge(8) reported the

solid-state reaction of ammonium and alkali metal salts

with tris(I,2-ethanediamine)chromium(III) complexes. They

studied the reaction by preparing a matrix of the alkali

or ammonium salt containing a sample of the tris(I,2-ethane

diamine )chromium( I I I) complex and following the reaction by

high temperatxire reflectance spectroscopy and dynamic re

flectance spectroscopy(DRS). They found that in certain

cases, the anion of the ammonium or alkali metal salt would

replace the anion of the tris(I,2-ethanediamine)chromium-

(III) complex during the deamination of the tris(diamine)

complex to the bis (diamine) complex, whereas earlier workers

found that only the tris(l,2-ethanediamine)chromium(III)

chloride or thiocyanate deaminated to the bis(diamine) com

plex. The order of the ease of substitution of the ammo

nium salt anions for I,2-ethanediamine was found to be:

F">SCN">Cl">BR''>I"* while the order of substitution of al

kali metal salt anions for I,2-ethanediamine was found to

be: SCN">F">Cl">Br">l". The reversal in the order of SCN"

and F" was attributed to the decrease in reactivity of the

fluoride ion in the alkali metal salt matrix. In this study

no evidence for substitution of iodide ion for the diamine

ligand was found up to a temperatiire of 225^0.

CHAPTER III

EXPERIMENTAL METHODS

The i,2-ethanediamine used in this investigation

was obtained from the Fisher Scientific Company, Fair

Lawn, New Jersey. The 1,2-propanediamine was obtained from

Eastman Organic Chemicals, Distillation Products Industries,

Rochester 3, New York. The 1,3-propanediamine used was

obtained from the American Cyanamid Company, New York 20,

New York.

The three diamines were dried by the method of

Putnam and Kobe(9). This method consisted of refluxing

the diamine with sodium hydroxide pellets for four hours,

separating the diamine layer from the water-sodium hydroxide

layer, and then distilling the diamine. The first and last

portions of the distillate were discarded.

The chromium(IIl) sulfate, x-l^ydrate. Analytical

Reagent Grade, and the chromium(III) chloride. 6-hydrate

were obtained from the Mallinckrodt Chemical Works, St.

Louis, Missouri.

All other chemicals used in the preparation and

analysis of the complexes were of reagent quality.

8

Methods of Preparation of Complexes

1,2-Ethanediamine Complexes of Chromlum(III) Salts

The tris(1,2-ethanediamine)chromiiim(III) complexes,

!lCr(en)33X3 (where X represents Cl", Br", I", SCN", and

%S0^^"), were prepared by the method of Rollinson and

Bailar(3). Chromium(III) sulfate, x- y ^ rate was dehydrated

by heating in an oven at 105®C. After the first day of

heating, the originally lumpy material was ground to a fine

powder and returned to the oven for an additional day.

The anhydrous chromium(III) sulfate was then reacted with

anhydrous I,2-ethanediamine in a one to three mole ratio

and heated in a flask fitted with a reflux condenser on a

steam bath. The green colored chromium(III) sulfate slow

ly changed color from green through purple to brown and

then to orange. As the reaction proceeded, the flask was

shaken vigorously at periodic intervals to prevent caking.

After the reaction mixture had turned solid, the shaking

was discontinued, however the vessel was not removed from

the steam bath until the reaction mixture was an orange

color. The product was washed thoroughly with ethanol to

remove any excess I,2-ethanediamine and then air dried.

Tr is(1,2-ethanediamine)chromium(III) chloride

was prepared by a metathetical reaction between

[Cr(en)312(204)3 and hydrochloric acid. The

lCr(en)^J2^^^6)3 complex was dissolved in the minimum amount

of five per cent hydrochloric acid solution (to retard the

10

aquation reaction). This solution was mixed with a 100

per cent excess of concentrated hydrochloric acid dis

solved in a 50 per cent larger volume of ethanol. The re

sulting solution was cooled to ice temperature and the

yellow solid was filtered, washed with ethanol, diethyl

ether, and allowed to dry in the air. The compound was

purified by ?recrystallization from water.

The Qther tris(I,2-ethanediamine)chromium(III)

complexes were prepared by reacting CCr(en)3lCl3 with the

ammonium or sodium salt of the corresponding anion. A

100 per cent excess of the appropriate sodium or ammonium

salt was added to a water solution of the £Cr(en)3]Cl3 and

the mixture cooled to ice temperature. The resultant yel

low solid was filtered, washed with ethanol and diethyl

ether, and air dried. The complexes were purified by re-

crystallization from water.

Tris(l,2-ethanediamine)chromium(lII) nitrate, the

one exception, was prepared by the reaction of CCr(en)3l2

(80^)3 with concentrated nitric acid. A 100 per cent ex

cess of concentrated nitric acid was added to a saturated

solution of CCr(en)3]2(204)3 and then ethanol was added to

cause precipitation. The salt was filtered, washed with

ethanol and diethyl ether, and air dried.

1.2-Propanediamine Complexes of ChromiumClII)

The tris(l,2-propanediamine)chromium(III) complexes

[Cr(pn)3lX3 (where X represents Cl", Br", I", SCN", and

II

2«

%204 ), were prepared by the method of O'Brien and Bailar

(4). This method involved the preparation of the tris-

(l,2-propanediamine)chromium(III) sulfate from the an

hydrous 1,2-propanediamine and dried chromium(III) sulfate.

The tris(1,2-propanediamine) complex was used as a start

ing material for the preparation of the other members of

this series.

Tris(1,2-propanediamine) chromium(III) sulfate was

prepared in the same manner as Cr(en)3 2(20^)3. Dried

chromium(lll) sulfate was treated with anhydrous 1,2-

propanediamine in a one to three mole ratio and the mixtxire

was added to a flask fitted with a reflux condenser. The

reactants were heated on a steam bath with occasional

vigorous shaking until the tris(1,2-propanediamine)chromium-

III) complex had formed. The complex was then washed with

ethanol to remove any excess 1,2-propanediamine and then

allowed to dry in air.

The other tris(l,2-propanediamine)chromium(lII)

complexes were prepared by a methathetical reaction be

tween tris(l,2-propanediamine)chromium(III) sulfate and

the corresponding ammoniiam salt. A saturated solution of

the sulfate complex was mixed with a lOO per cent excess

of a saturated solution of the ammonium salt of the de

sired anion. The mixture was then cooled in an ice bath

and the new complex was filtered, washed, with ethanol and

diethyl ether, and dried in air.

12

It has been found(4) that tris(I,2-propanediamine)-

chromium(III) chloride is too soluble to be prepared by

this method. Rather, a solution of the tris sulfate com

plex was reacted with a solution of an equivalent amount

of barium chloride. After standing for several hours, the

barium sulfate precipitate was filtered off and ethanol was

added to the filtrate to cause precipitation of the chlo

ride complex. After filtration, the CCr(pn)3"]Cl3 was washed

with ethanol followed by diethyl ether and allowed to dry

in air.

l.3-Propanediamine Complexes of ChromiumClII)

The method of Schlaefer and Kling(lO) was used for

the preparation of the tris(l,3-propanediamine)chromium(III)

complexes. This method consisted of treating anhydrous

chromium(III) chloride with anhydrous 1,3-propanediamine.

The starting material, freshly prepared chromium(III) chlo

ride, was prepared by the method of Fernelius(ll). Thirty-

seven grams of hydrated chromium(III) chloride, CrCl3

6-hydrate, was placed in a 500 ml distilling flask. The

flask was placed in a furnace in such a manner that the arm

and neck of the flask were on the outside. The arm of the

flask was connected to a water condenser and a receiver

for the liquids produced during the reaction was placed in

an ice bath and connected to the condenser. Since phosgene

was produced, the entire reaction was carried out in the

hood. The furnace was turned on, and when the temperature

13

of the flask reached lOO^C, the hot vapor of carbon tetra

chloride was passed into the flask. At approximately

300^0, a condensate of water and carbon tetrachloride be

gan to collect in the receiver. The reaction was complete

\ên the temperature of the furnace reached 650°C. The

furnace was allowed to cool and the flask removed. The

product was Removed from the flask and refluxed with 6 N

hydrochloric acid for 24 hours to remove basic constitu

ents. The product was filtered, washed with hot water,

and dried in an oven at 120°C.

Tris(l,3-propanediamine)chromium(III) chloride was

prepared by placing 20 g of the freshly prepared chromium

(III) chloride into a dry 250 ml flask. To this was added

a mixture of 50 ml of anhydrous 1,3-propanediamine and 150

ml of anhydrous diethyl ether. The flask was closed with a

drying tube containing sodium hydroxide pellets. After one

hour, the solid was broken up with a spatula, and the ether

distilled off by use of a steam bath. The red-brown solid

gradually expanded and formed a yeIlow-brown mass which al

most filled the flask. The flask was cooled, the product

was removed from the flask and was dissolved in 100 ml of

water and 10 ml of concentrated hydrochloric acid, the mix

ture was filtered, and the filtrate was cooled in an ice

bath. The light yellow crystals \îch formed were filtered,

washed with diethyl ether and air dried. The crude product

was purified by recrystallization from water. A second

14

crop of crystals was obtained by adding ethanol to the fil

trate until precipitation almost occured. The solution was

then cooled in an ice bath and a second filtration per

formed.

Tris(l,3-propanediamine)chromium(III) bromide was

prepared by dissolving 10 g of tris(I,3-propanediamine)

chromium(lll) chloride in 40 ml of water and adding 20 ml

of concentrated hydrobromic acid. The solution was cooled

in an ice bath and the complex bromide precipitated out.

The product was filtered and washed with 95 per cent ethanol.

The product was removed from the filter and the preceding

scheme was repeated twice more. The purified tris(1,3-pro

panediamine) chromium( III) bromide was filtered and washed

with ethanol and diethyl ether. The product was dried in

an oven at 50°C.

Tris(l,3-propanediamine)chromium(III) iodide and

thiocyanate were prepared by dissolving 10 g of tris (1,3-

propanediamine)chromium(III) chloride in 50 ml of water.

Ten milliliters of cold saturated sodium iodide or ammonium

thiocyanate were added and the mixture was cooled in an ice

bath. The product was filtered and washed with ethanol.

The crude product was redissolved and reprecipitated twice.

Finally, the solid was washed with diethyl ether and dried

at 40^0.

All of the complexes used in this study which con

tained water of hydration were dried prior to use at a

15

temperature of approximately 70°C in an electrically heated

vacuum desiccator.

Methods of Analysis

Analysis for Chromium Content

The complexes used in this study were analyzed for

chromium content by ignition to the oxide, Cr203. A weighed

sample of the complex was placed in a tared crucible and

intimately mixed with oxalic acid and then slowly heated

to the decomposition temperature. The mixture was then

heated in a muffle furnace at 700°C for one to two hours.

Analysis for Halide and Thiocyanate Contents

The complexes used in this study were analyzed for

halide or thiocyanate content by titration with a standard

ized silver nitrate solution, using dichloroflucreseein as

an absorption indicator. All of the titrations were per

formed in tungsten light to minimize darkening of the sil

ver halide or thiocyanate precipitate.

Analysis for Nitrogen Content

The complexes prepared in this study were analjrzed

for nitrogen by the Dumas method on a Coleman Model 29

Automatic Nitrogen Analyzer. The sample sizes varied from

10-20 mg, the combustion furnaces were held at 700° and SOO^C

while the post heater was held at 550^0. The carbon di

oxide source was a gas cylinder supplied with Coleman Grade

16

carbon dioxide from the Matheson Company, Joliet, Illinois.

Instrumental Methods

Vacuum Thermogravimetric Studies

The vacuum thermogravimetric studies were carried

out on a thermobalance consisting of an Ainsworth vacuum

recording balance(12) equipped with a furnace wound with re

sistance wire, a furnace programmer, a two pen strip chart

recorder, and a vacuum system. The sample was placed in a

platinum bucket suspended below the left balance pan. The

vacuum was maintained with a mercury diffusion pump backed

with a mechanical rotary pump. Sample sizes ranged from

10 to 30 mg, a heating rate of approximately 5°C per minute

was employed, and a pressure of approximately 30 microns of

Hg in the vacuum system was maintained.

Reflectance Spectroscopy Studies

The reflectance spectrum of each compound of the

study by employing a Beckman Model DK-2A recording spectro-

reflectometer.

Matrix Studies

The solid-state deamination studies were performed

using an intimate mixture consisting of a specific tris-

(diamine)chromium(III) complex and an excess of the de

sired ammonium salt. The mixture was prepared by gentle

grinding of the components with a small mortar and pestle

17

until a uniform blend was obtained.

A sample of the above mixture was then transferred

to a capillary tube and heated in a Thomas-Hoover Uni-melt

capillary melting point apparatus. If a color change oc

curred during the heating process, the temperature and the

color were noted. Then a sample of the mixture was heated

to this temperature until reaction was complete. The re

action product was cooled and its reflectance spectrum re

corded. The remaining sample was then transferred to a

platinum boat and heated at the reaction temperature for

approximately 15 minutes. The furnace was then evacuated

to approximately O.l mm Hg and heated to the sublimation

or dissociation temperature of the ammonium salt until the

excess salt was removed. The sublimation temperature of

each of the various ammonium salts used in this study was

determined by vacuum thermogravimetry.

The vacuum sublimation apparatus and reaction ves

sel consisted of a vertical tube furnace into which the

platinum boat was lowered. The furnace was equipped with

a cold-finger condenser to trap the sublimated ammonium

salt and a thermocouple for temperature detection. The top

of the furnace led to an acetone-dry ice trap and then to a

mechanical vacuum pump. The furnace was heated by re

sistance wire from a variable transformer and the thermo

couple leads went to an ice bath reference junction and

then to a pjnrometer for temperature read out. A block

18

diagram of the react ion and sublimation assembly i s shown

in Fig . I .

19

Figure I

Apparatus Used to React and

Purify the Matrix Mixture

A - Furnace

B - Thermocouple

C - Cold Finger Condenser

D - Vacuum Release

E - Thermocouple Leads to Ice Junction and Pyrometer

F - To a Cold Trap and Vacuum Pump

G - Platinum Crucible

H - Power Supply

20

- ^ & k

n <E)

o

CHAPTER IV

EXPERIMENTAL RESULTS AND DISCUSSION

Analytical Results

The analyses of the tris (diamine) chromium (HI)

compounds are given in Table 1. These data were obtained

by the methods previously described.

Results of the Study of the

Tris(l>2-ethanediamine)chromium(III) Compounds

The minimum temperature at which each of the vari

ous ammonium salts, employed as matrix materials, vola

tilized (sublimation or decomposition) was determined by

vacuum thermogravimetric analysis (TGA). The samples

were heated at a linear heating rate and the temperatures

at vîch appreciable rates of mass loss occurred were

used as the minimum volatilization temperatxires. The vacu

um TGA was continued until all of the mass loss occurred

to determine ^êther a residue remained. The vacuum TGA

curves of the ammonium salts are shown in Figures 2 and 3.

All of the ammonium salts, except ammonium chromate,

ammonium molybdate, and ammonium dihydrogen phosphate, de

composed to leave no residue. The latter three salts were

21

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o 00

o CO

r-l CO

CNi

CM 00

CM

o

vO CO

(X)

o uo

o>

o

00

m

CM

o m .-4

VO

U \- 00 ON

o o

NO

CO NO

UO

CM

00 CM

ON

CM NO

NO 00 uo

CO NO

NO

CM

CM

CM

f-4 UO

r>. CO CO 00

CM CM

00

o CO NO CM CM

CM

00

00

o

00

CM »-l

o

00

ON NO NO

CO

2: o

00 CO

00 CO

00 CM

00 CM

NO in

CO ^

CO

u

CO uo

NO

CO NO

NO

uo NO

ITS CO

NO

o o

ON CM

^ o

CO r-l

o CO

^\ G (U

v-^ U

(J

CO U

CQ

CO ^-s

n <D v^

CO H-l

CO <^ G 0)

> . i i ^

.<!J

CO U

CQ

CO ^\ G CU

^ ^

P.

CO h-l

• s / - v G cu v ^

.<!3.

CO r-4

u CO

/ - \

c 4J v ^

.6.

2; o CO

N - /

CO y^K

G U

y»^

U

CO U

(£)

^3, / - N

c 4-1 \^

u

23

Figure 2

Vacuum Thermogravimetric Curves

of Various Ammonium Salts

A - (NH4)5 M07O24.4H2O

B - NH4Bj!

C - NH4CI

D - NH4I

E - NH4F

F - NH4SCN

24

100 200 3C0 400 TEMPERATURE CO

ixÔ

25

Figure 3

Vacuum Thermogravimetric Curves

of Various Ammonium Salts

A - (NH4)2204

B - (NH4)22208

C - (NH4)H2P04

D - (NH4)22203

E - NH4NO3

F - (NH4)2C204

G - (NH4)2Cr04

26

100 200 300 400 TEMPERATURE CO

u> T

27

therefore excluded from any further studies. As can be

seen, ammonium chloride, ammonium fluoride, ammonium bro

mide, ammonium iodide, ammonium thiocyanate, ammonium ace

tate, ammonium oxalate, ammonium formate, ammonium thio-

sulfate, ammonium nitrate, ammonium persulfate, and ammo

nium sulfate all volatilized between 75° and 225°C. The

minimum temperatures of volatilization for these ammonium

salts are listed in Table 2.

Stembridge(8) found that tris(diamine) chloride

yields the bis(diamine) chloride, fluoride, and thio-

cynate complexes, while the tris(diamine) bromide yields

the bis(diamine) bromide, chloride, fluoride, and thiocya

nate complexes. With these data and the order of anion re

placement being: NCS">F">Cl">Br">l", a trend is indicated

in which the tris (diamine) iodide might be the most desir

able starting material (the tris(diamine) complex which

yields the largest number of bis(diamine) complexes). The

most desirable starting material was found by heating a

matrix of a particular tris (diamine) complex with each of

the ammonium salts to the reaction temperature and then

identifying the bis(diamine) complex which is formed by

the characteristic peak maxima obtained from its reflect

ance spectrum. This process was repeated with each tris-

(diamine) complex and the most desirable starting material

was found to be the tris(diamine)chromium(III) iodide.

Since Stembridge(8) determined that the solid-state

28

TABLE 2

MINIMUM VOLATILIZATION TEMPERATURES OF AMMONIUM SALTS

• ' Volatilization Compound ' Temperatures(°C)

NH4CI 150

NH4F 75

NH4Br 210

NH4I 150

NH4SCN 75

NH4(0Ac) 115

(NH4)2C204 75

NH4(H002) 105

(NH4)2S203 150

NH4NO3 125

(NH4)22208 225

(NH4)2204 210

29

matrix reaction between tr is (1,2-ethanediamine) chromium( III)

complexes and ammonium chloride, bromide, fluoride, and

thiocyanate did occur, the remaining ammonium salts were in

vestigated to determine vêther they would react in a solid-

state matrix to yield the bis(diamine)chromium(III) com

plex. This was accomplished by heating a sample of the

matrix mixture, which consisted of a 5:1 mole ratio of am

monium salt to tris(diamine) complex, in a capillary tube

melting point apparatus and observing the sample visually.

It was found tjiat ammonium oxalate, ammonium acetate, am-

monium formate and ammonium iodide caused the matrix re

action to occur. This was noted by the distinct blue or

violet color of the bis(diamine) complex in the sample at

165°, 115°, 105°, and 230°C, respectively. The ammonium

salts containing the sulfate, nitrate, thiosulfate, and the

persulfate anions gave either no reaction (sulfate) or a

rapid oxidation-reduction reaction (nitrate, thiosulfate,

and persulfate). These compounds were then disregarded in

all further studies. The results of the thermovisual

study are shown in Table 3.

The large scale preparation of the bis(diamine)-

chromium(IIl) complexes was carried out in the apparatus

shown in Figure I. A one to two gram sample of the matrix

mixture was placed in a platinum crucible which was inserted

into the vertical tube furnace. The furnace was heated to

the reaction temperature and allowed to remain there for

30

TABLE 3

RESULTS OF HEATING MATRICES OF TRIS(I,2-ETHANEDIAMINE) CHROMIUM(III) COMPOUNDS AND AMMONIUM SALTS

Matrix Mixture Tempera-t u r e ( o c ) Observation

LCr(en)3]Cl3 + NH4CI

[Cr(en)3']Cl3 + NH4SCN

[Cr(en)3']Cl3 + NH4F

[Cr(en)3']Br3 + NH4Br

[Cr (en) 3313 + NH4I

[Cr (en) 3313 + NH4HCO2

[Cr (en) 3^13 + NH4OAC

[ p r ( e n ) 3 l l 3 + (NH4)2C204

[Cr (en) 3313 + (NH4)2S04

ICr(en)33l3 + NH4NO3

rCr(en)3] l3 + (NH4)22203

[Cr(en)3] l3 + (NH4)22208

150

80

90

225

230

105

115

165

>250

125

75

25

Violet

Violet

Violet

Violet

Violet

Violet

Violet

Violet

color

color

color

color

color

color

color

color

No reaction

Black decomposition product



31

15 minutes while the sample reacted. The one exception to

the 15 minutes reaction time was the sample containing am

monium iodide which required one hour to react. The fur

nace was then evacuated and the reaction mixture was puri

fied by vacuum volatilization of the excess ammonium salt.

The length of time necessary for purification was

determined by weighing the sample and crucible at various

intervals. When constant weight was obtained for two

weighings, purification was considered complete. For some

matrix mixtures it was found that a temperature higher than

the minimum volatilization temperature of the ammonium

salt was necessary to purify the bis(diamine) complex in a

reasonable length of time. This fact will be explained

further during the discussion of the mechanistic study.

The purification temperatures and times necessary for the

various matrix mixtures are shown in Table 4.

The bis(diamine) complexes were characterized by

elemental analysis and by reflectance spectroscopy. The

analytical results are listed in Table 5 while the re

flectance spectra are shown in Figures 4 and 5, The re

flectance spectra peak maxima of the various bis(diamine)

complexes consisted of two peaks, one in the 500-560 mu

range and the other in the 375-400 mu range.

Results of the Study of the

Tris (l.2-propanediaTnine)chromium(III) CoT pouncs

32

TABLE 4

TEMPERATURE AND TIME REQUIRED TO PURIFY THE BIS(1,2-ETHANEDIAMINE) COMPOUNDS

Product

Cis - CCr(en)2Cl2lCl

Cis - CCr(en)2(NCS)2']NCS

Cis - rcr (en)2 F2IF

Cis - £Cr(en)2Br2"lBr

Cis - r:Cr(en)2l2DI

Cis - £Cr(en)2(HC02)2]HC02

Cis - LCr(en)2(OAc)2"]OAc

CCr(en)2C20zp2^2^4

P u r i f i c a t i o n Temperature(°C)*

150

175

125

210

220

i ^''^

190

190

P u r i f i c a t i o n Time (hr)

6

5

4

6

10

7

7

8

33

No previous matrix studies have been performed on

these compounds, therefore the first step in the study was

to determine if the solid-state matrix deamination reaction

did occur and if so, to determine the most desirable start

ing tris (diamine) complex. This was done by heating the

matrix mixture in a capillary tube in the melting point ap

paratus and observing any reaction visually. If the re

action looked favorable, a larger sample of the matrix was

heated and after reaction, the reflectance spectrum was re

corded. It was assumed that the order of anion replacement

for the matrix reaction of the tris(l,2-propanediamine)-

chromi\im(lIl) complexes would be the same as that observed

for the tris(l,2-ethanediamine)chromium(III) complexes. If

this is true, the most desirable starting material should

be the tris(l,2-propanediamine)chromium(III) iodide. How

ever, upon heating a matrix of the compound in the melting

point apparatus the first observable reaction was a de

composition to a black product at approximately 210°C. This

eliminated the tris(l,2-propanediamine)chromium(III) iodide

as a starting material. The process was now repeated using

tris(l,2-propanediamine)chromium(III) bromide as the start

ing material. All of the ammonium salts caused a reaction

to a violet product between 115°C and 2l5°C except the

iodide, which decomposed to a brown product at 230°C, The

results of the study are shown in Table 6, Reflectance

spectroscopy was then used to show that the bis(diamine)

34

m

<

en

i

a B I

CM

(X4

o M en 3

^ o (4 0)

4J O

V4 O O

H

E M

^ •

Z O (D

•O

^

o

o a o o

1-4

r*. .

pv CO

CM r-l .

00 CO

ON •

00 f-l

CM i-l •

o CM

CO •

00 r-A

r*. NO .

00 •-I

u PQ

CM .

NO uo

o rn .

00

m

« •

CM f4

O NO •

CO i-i

CM •

CM •-I

CM NO .

CM f-l

<f •

ON

CO f-A •

o r-i

CO •

ON

i-l St •

ON

^ .

NO CM

O CO .

00 CM

UO •

<^ •-4

rH

o . uo »-i

r-l .

•l-CM

liO < ! •

a <!• CM

'if .

r-l CM

ON NO .

CM CM

*;!' .

00 I-l

<f CM •

00 r-l

CO •

r* r-l

CM ON •

NO r-l

ON •

m r-l

<t o . NO r-4

r-l •

d• r-l

ON 00 •

^ r-l

NO .

00 r-l

r-l »d-,

00 r-l

Si-.

r*. r^

O r-l •

r«. 1-4

o CM r-l o CM

G <D

k

u

CM

8 en

CM U « CM

G 0)

u

M

fP. M

rpti ^^ en

\^

E •Ii {Z4

rj5j /-v CM

HC

O

\m.^

CM CM CM CM

G O

G 0)

G 0)

I

col I

ml I

ml O P

C 0)

il

u <: o

u <: o CM

c

I

O CM O CM

o CM

CM

0) >*^ u P.

35

TABLE 6

RESULTS OF HEATING MATRICES OF TRIS(1,2-PROPANEDL/U<INE) CHROMIUM(III) COMPOUNDS WITH AMMONIUM SALTS

Matrix Mixture

CCr(pn)3ll3 + NH4CI

[Cr(pn)33l3 + NH4Br

rCr(pn)37l3 NH4I

rCr(pn)3:?Br3 + NH4CI

rCr(pn)3'3Br3+ NH4Br

[Cr(pn)3JBr3 + NH4F

rCr(pn)3]Br3 + NH4I

[Cr(pn)3lBr3 + NH4SCN

[Cr(pn)3;Br3 + NH4HCO2

[Cr(pn)37Br3 -*• NH4OAC

[Cr(pn)3lBr3 + (NH4)2C204

Tempera-ture(oc) Observation

210

220

210-260

210

215

150

230

170




Violet

Violet

Pale green

Brown decomposition product

Dark red

115

150

200

Violet

Violet

Blue gray

36

Figure 4

Ref l ec tance Spectra of Various ( I ,2 -e thanediamine)

Chromium(lII) Compounds

A. [Cr(en)3 l l3 -

B. C i s - [ C r ( e n ) 2 l 2 l l

C. Cls.-ECr(en)2Cl2lCl

D. Cis-rCr(en)2F2lF

E. Cis-LCrCen)2Br2lBr

37

10-

20

30

A •/•.. x •.. \ • ' \ ' • • • . . \

40

UJ

o z ? o ;^5o IL. UJ

60

\ /

\ /

V \

• • - . . \ « w

\

T V

\

\

7 0 -

8 0 -

9 0 -

« 400 WAVELENGTH (M/4)

"50^ ToC

38

Figure 5

Ref l ec tance Spectra of Various ( l ,2 -e thanediamine)

Chromium(III) Compounds

A. [Cr(en)2C2C4l2C204

B« Cis-CCr(en)2(OAc)2l(OAc)

C. £is-/;Cr(en)2(NCS)2l(NCS)

D. Cis-CCr(en)2(HC02)2lHC02 •

39

80

90-

\ .

X 4 0 0 500 600

V.AVE LENGTH (M>U) 700

40

compounds formed were not a l l the same compound. The r e

f l e c t a n c e spectra curves are shown in Figures 6 and 7. Each

spectrum had two peak maxima, one ranging from 500-560 mfi

and the other from 375-420 m i.

The large s c a l e preparation and p u r i f i c a t i o n

operat ions were then carr ied out in the same apparatus and

in the same manner as the preparation and p u r i f i c a t i o n of

the dianionobis(1 ,2-ethanediamine)chromium(III) complexes.

The p u r i f i c a t i o n temperatures and times are a l s o e s s e n

t i a l l y the same as those obtained from the b i s ( 1 , 2 -

ethanediamine) complexes. These r e s u l t s are l i s t e d in

Table 7. The a n a l y t i c a l r e s u l t s of the b i s (1 ,2 -propane

diamine) complexes are l i s t e d in Table 8 .

Resu l t s of the Study of the

Tris( l .3-propanediamine)chromium(III) Compounds

The r e a c t i o n of tr is( l ,3-propanediamine)chromium-

( I I I ) complexes in a matrix of ammonium s a l t s did not

fo l low the trend s e t by the t r i s ( I , 2 - e t h a n e d i a m i n e ) and

the tr i s ( l ,2 -propanediamine)chromium(III ) complexes.

There seemed t o be no order of anion replacement and no

t r i s (diamine) complex \ ^ i c h i s the most des i rab le as a

s t a r t i n g m a t e r i a l . The anion which i s s u b s t i t u t e d for the

1,3-propanediamine may come from the i o n i c sphere of the

t r i s (1 ,3 -propaned iamine ) complex at the lowest r e a c t i o n

temperature or i t may come from the anion of the ammonium

41

Figure 6

Ref l ec tance Spectra of Various (1,2-propanediamine)

chromium(III) Compounds

A. CCr(pn)3]B^3

B. C i s - [Cr(pn)2F2T F

C. Cis-rCr(pn)9(NCS)9lNCS

D. Cis-[Cr(pn)2Cl2lCl

42

500 600 WAVELENGTH (M/4.)

43

Figure 7

Reflectance Spectra of Various Bis(1,2-propanediamine)


A. Ci3-rCr(pn)7Br2"lBr - •

B. i2is-[Cr(pn)2(HC02)2lHC02

C, £Cr(pn)2C204"]2C204

44

500 ^ WAVELENGTH (M/^)

45

TABLE 7

TJ PERATURE AND TIME REQUIRED TO PURIFY THE BIS(1,2-PR0PANEDIAMINE) COMPOUNDS

P u r i f i c a t i o n P u r i f i c a t i o n Product Temperature(OC)* Time (hr)

£ i s - CCr(pn)2Cl2':jCl 160 5

Cis - CCr(pn)2(NCS)2lNCS 190 4

£ i s - CCr(pn)2F2DF 130 4

Cis - CCr(pn)2Br2llBr 2lO 8

Cis - CCr(pn)2(H002)23H002 175 8

Cis - CCr(pn)2(OAc)2lOAc 180 7

46

u 25

00

M

<

<

o

I

CM

cn M

o cn M

:3

c ^ o

4) • XI U 4J O O 4>

X!

§ O

^ •

^ u 2 O

0) x: H

/-s O

o

•o c

a o p

p

ON

St CO

NO •

St CO

.

CM

U

CO

St

c St .

St

ON

8

NO St

CO

5 «iO

CO CO

ON

CM CO

ON

CM

o CM CM

St

CM

NO ON •

NO

o ON

CM 00

NO

CO CO

00

CO

ON

00

CO

NO •

CM CO

o o CM

CM CM •

o CM

O

CM

uo

en

1 3 . f-l

o CM

§. &

I

•si

CM • CM

CM O

u z CM /^

a u p u I

CM

8 rSi /^ CM O O

CM X

U4

CNI

c OK %.• U P

EM CM

G

u p

c

I I

•)l ml «|

d 8 d 3

CM •

CM CM

ON

CO

00

• UO CM

o CO •

UO CM

uo

uo NO

UO

a o

u

o

St

o CM P CM

CM CM

G Oi

a b

o CM O c

/"^ G

1 P

47

salt if the mixture is heated to higher temperatures. When

both reactions occur in a small temperature range, the

anion which has moved into the coordination sphere may be

either from the ionic sphere of the complex or from the

ammonium salt or a mixture may be obtained. Therefore, to

have confidence in obtaining the desired complex, the

matrix mixtujre must consist of a tris (diamine) and ammon

ium salt which have the same anion. This was shown by heat

ing various matrix mixtures in a melting point apparatus.

The results of this study are shown in Table 9.

Large scale preparations were carried out only with

matrices consisting of a tris(diamine) complex and am

monium salt having the same anion. Since this reduced

the utility of this method for the synthesis of the bis-

(diamine) complexes, it was only carried out for the chlo

ride, bromide, and thiocyanate. The reaction temperatures

of these matrices are also shown in Table 9. These bis-

(diamine) compounds were purified in the same manner as

previously discussed and required approximately the same

temperatures and purification times. These results are

shown on Table 10, The compounds were characterized by

elemental analysis and by reflectance spectra. These re

sults are shown in Table II and Figure 8.

Results of the Reaction Mechanism Study

All of the reactions previously discussed involve

48

TABLE 9

RESULTS OF HEATING MATRICES OF TRIS(1,3-PROPANEDIAMINE) CHROMtUM(III) COMPOUNDS WITH AMMONIUM SALTS

Matrix Mixture

CCr(tn)3l(NCS)3 + NH4CI

[Cr(tn)3l(NCS)3 + NH4Br

[Gr(tn)33(NCS)3 -i- NH4SCN

[Cr(tn)33Cl3 + NH4SCN

CCr(tn)37Cl3 + NH4CI

[Gr(tn)3;]Cl3 + NH4Br

[Cr(tn)3[jBr + NH4Br

Temperature (°C)

145 200 135 210

125

200

200

205

195

Observation

Red Violet Red Violet

Red

Violet

Violet

Violet

Violet

49

TABLE 10

TEMPERATURE AND TIME REQUIRED TO PURIFY THE BIS (1,3-PROPANEDIAMINE) COMPOUNDS

P u r i f i c a t i o n P u r i f i c a t i o n Product Temperature(^C)* Time (hr)

Cis - rCr(tn)2Cl£]Cl 160 5

Cis - [Cr(tn)2Br27Br 210 8

Cis - [Cr(tn)2(NCS)2lNCS 190 4

50

M

i I

CO

tn

M

EM

o cn

^ o u

o «

§ o

*M ^ • ^ u as o

0)

§ o

U4

o 0)

a o p

p NO

St CO

ON NO

• <t CO

in .

CM

CM

00

NO

NO ON

• NO

u PCk

8 NO NO

ON

<t

ON

00

o c ^

CM 00

NO

CO

00 •

CO CO

NO

CO CO

ON O • •

^ St

ON 00

CO

f - l

p m CM p-4

P CM

/ - \ G iJ

^4 CQ

m CM u CQ CM

/"^ G P

cn p Zi

CM <^\ cn o 2: \^ CM

< N

c 4J

ana

n) m| ml

d ^ dl

51

the substitution of one diamine by two anions in the co

ordination sphere of the central metal ion. However, the

anions seem to have little relation to the anions in the

ionic sphere of the central complex ion, since the sub

stituted anions come from the ammonium salt in some cases

and from the ionic sphere in others. In an attempt to

postulate a meciianism for these reactions, tris(1,2-

ethanediamine)chromium(III) iodide was heated with vari

ous matrix mixtures and the mixtures were observed visual

ly. The iodide complex was employed since it has no tend

ency to deaminate thermally to ci8-diiodobis(I,2-ethane

diamine )chromium( I II) iodide(8) and it is also the most

desirable starting material for the matrix reactions. Thus,

if the violet colored cis-dichlorobis(I.2-ethanediamine)-

chromium(III) chloride is obtained, it must be due to re

action with the matrix and not thermal deamination. The

results of the study are given in Table 12.

It can be seen that cis-dichlorobis(l.2-ethane-

diamine)chromium(III) chloride is obtained with all those

matrices \diich are capable of furnishing the acid, HCl, or

a proton. No product is obtained in the case of tetra-

methylammonium chloride, potassium chloride, or cesium chlo

ride. Thus, a proton is necessary for the thermal matrix

reaction. Since the ammonium salts dissociate at fairly

low temperatures to yield ammonia and the corresponding acid,

the first step of the mechanism must be the protonation of a

52

TABLE 12

REACTION OF [Gr(en)3']l3 WITH VARIOUS MATRIX COMPOUNDS

Matrix Compound Reaction Temp(°C) Results or Product

CH3NH3CI

(CH3)2NH2C1

(CH3)3NHCI

(CH3)4NCi

KCl

CsCl

HCl(g)

170 Ci s - rCr(en)2ClJCl

160 Cis-rCr(en)9Cl9lCl

160 Cis-CCr(en)2Cl2lCl

255 - 275 Black-colored product, gas evolution

300 No reaction

300 No reaction

145 Cis- [Cr(en)2Cl2lCl

53

Figure 8

Reflectance Spectra of Various (1,3-propanediamine)


A. CGr(tn)37cl3

B. £is-[Cr(tn)2(SCN)2"]SCN

C. Ci8-[Cr(tn)2Cl27Cl

D. Cis-[Cr(tn)2Br2]Br

54

UJ o z < I -o UJ -j50f-u. UJ

a:

70

80

«

90 L

KX)

. . • .

» . • • •

500 600 WAVELENGTH (M/t)

; & Tfe

55

I,2-ethanediamine nitrogen atom followed by breaking of the

chromium-nitrogen bond. This is followed by protonation

of the second 1,2-ethanediamine nitrogen atom and the sub

sequent breaking of the second chromium-nitrogen bond. The

proposed mechanism is shown in Figure 9. The overall re

action, on the basis of this mechanism, is

llCr(en)3lX3(s) + 2NH4X(s) - ^

iLia-[Cr(en)2X2lX(s) + en-2HX(s)

+ 2NH3(g).

It has been shown by Stembridge(8) that on heating

tris(l,2-ethanediamine)chromium(IIl) chloride, either alone

or containing traces of ammonium chloride, I,2-ethanediamine

is one of the reaction products. However, by using mass

spectral techniques(13), it was found that if an excess of

the ammonium halide is present, l,2-ethanediamine«2HX and

ammonia are obtained, as shown in Figure 10. Apparently

in the former reaction, I,2-ethanediamine•2HCI is the cata

lyst in the reaction and deprotonates to yield I,2-ethane

diamine, \île in the matrix reaction the ammonium chloride

must be the catalyst.

56

Figure 9

Proposed Mechanism for the

Thermal Matrix Reaction

A. Thermal dissociation of ammonium salt.

B. Deamination of tris(diamine) complex.

57

p»

X

X 1h?n ro

o

X

o

I X CVJ

5S ••iw ^ * : < * r » ^ - : ; * '

Figure 10

Mass Spectrometer Curve of M/e of 17

Versus Temperature

59

cr; o 0.1 CO

^ !

5a KX) 150 200 TEMPERATURE (TC)

250

CHAPTER V

CONCLUSION AND SUMMARY

The reactions studied in this investigation show

a relatively straight forward scheme for the preparation

of many bis(diamine)chromium(III) complexes from a solid-

state matrix of the corresponding tris (diamine) chromium-

(III) complex and an ammonium salt. It is apparent that

the preparation of the bis (1,2-ethanediamine )chromium( 111)

complexes has the most universal application. This is due

primarily to the inertness of the tris(l,2-ethanediamine)-

chromium(lll) iodide with respect to thermal deamination

in the absence of a catalyst and to the low temperatures

at vîch the thermal matrix reactions occnir. The prepa

ration of bis(l,2-propanediamine)chromium(III) complexes

from a matrix of tris(l,2-propanediamine)chromium(III)

complexes and ammonium salts has one limitation in that

the reaction temperatures are higher. Thus, some of the

bis (diamine) complexes may be unstable at the temperature

at which they are formed. The matrix reaction involving

tris(l,3-propanediamine)chromium(III) complexes and am

monium salts is the most restricted. Only matrices which

contain ammoniiom salts and tris (diamine) complexes having

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the same anion may be employed with certainty of obtaining

the desired bis(diamine) complex.

This method of 83mthesis is dependent upon the

nature of the ammonium salt. It cannot be employed if the

ammonium salt volatilizes to leave a residue, since then

purification cannot be achieved by vacuum sublimation. It

cannot be employed with ammonium salts which are too re

active either by oxidation or reduction, since then the

entire tris(diamine) complex decomposes.

A mechanism has been postulated which describes

the thermal matrix reaction which takes place with all

three tris (diamine)chromium( III) complexes and is con

sistent with all the data which is available. This mechan

ism can be used to describe the thermal deamination re

action as well as the matrix reaction.

LIST OF REFERENCES

! • P. P f e i f f e r , P. Koch, G. Lando, and A. Trieschmann, g e r i c h t e Der Deutschen Chemischen G e s e l l s c h a f t . 5;, A1S5 (1564). -^

2. p. Pfeffer, P. Koch, G. Lando, and A. Trieschmann, erichte Der Deu Li, 4275 (1^04). terichte Der Deutschen Chemischen Gesellschaft.

3. C. L. Rollinson and J. C. Bailar, Jr., Journal of the American Chemical Society. 66. 641 (1944),

4. T. D. 0«Brien and J. C. Bailar Jr., Journal of the American Chemical Society. 67, 1856 (1945)

5. M. Rock, Doctoral Dissertation. The University of Maryland, 1960.

6. J. L. Bear and W. W. Wendlandt, Journal of Inorganic and Nuclear Chemistry. 17, 286 (1961)

7. J. L. Bear, Doctoral Dissertation, Texas Technological College, 1960.

8. W. W. Wendlandt and C. H, Stembridge, Journal of Inorj anic and Nuclear Chemistry, 27, 575 (1965).

9. G, L. Putnam and K. A, Kobe, Transactions of the Electrochemical Society, 74, 610 (1938)

10. H. L. Schlaefer and A. Kling, Zeitschrift fur Anorganische und Allgemeine Chemie, 302, I (1959).

11. W. C. Fernelius, Inorganic Synthesis, II, New York: McGraw-Hill Book Company, Inc., (1946) pp. 193-196.

12. W. W. Wendlant, Thermal Methods of Analysis, Inter-science Publishers, Division of John Wiley & Sons, New York, (1964).

13. W. W. Wendlandt and T. M. Southern, Analytica Chemica Acta. 32. 405 (1965).

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IN CHEMISTRY Submitted to the Graduate Faculty of Texas