DOCTORAL DISSERTATION SERIES STA&/£/T/£S Of Af£7ML COA/ff£ f£ S t i t l e w /T A / M / c / / / w e c o v m m m l m & £ /v £ £ ¥ GM /(L/d a u t h o r /& £ / UNIVERSITY P £ /V A /' S T A T S C O £l. DATE Pk o. 3 2 4 ! DEGREE_ _ PUBLICATION NO. \U UNIVERSITY MICROFILMS *< A N N A R B O R ■ M I C H I G A N The Pennsylvania State College The Graduate School Department of Chemistry The Stabilities of Metal Complexes With Amines Which Contain Sulfur or Oxygen A the s is ^7 Sly C-onick Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy August 1951 Approved: ACKNOWLEDGEMENT The author wishes to express his sincere thanks to Dr. W. C. Fernelius, who suggested this problem, for his help and encouragement in the prosecution of this research. The author is indebted to Dr. B. E. Douglas and Dr. G. G* Haas for their timely advice and many helpful suggestions. The author also wishes to thank The Office of Naval Research, under whose sponsorship this work was conducted. TABLE OF COFTE17TS Intro iuct ion 1 A. Discussion of type of work done in past 1 o 3. Statement of objectives of thesis 4 II. lie tiro do for the determination of complexity constants 4 A. Electrode potentials B. Spectrophotometrie 4 4 G. Solubility methods D. Distribution 5 E. Bjerrum's method D 1. Complex formation Is stepwise 5 2. Definition of terms 7 3. Equations used in the calculations 8 III. The coordination process 13 IV. Experimental procedure 15 V. Preparation of reagents 20 A. Buffer salt solutions 20 B. Hetal salt solutions 20 G. Acids 24 D. Ligands 24 1. 2-Thenylamine 24 2 • 2-Fur furyl amine 24 3.' Benzyl amine 25 4. 1,3-Dlamino-2-propanol 26 5. Preparation of sulfur-containing amines 26 a. The use of ethylenimine 26 page b. Bis(2-aminoethyl)sulfide " 27 c. 2 - An i n o e t hy 1 mercaptan 28 d. Methyl 2-aminoethyl sulfide 29 e. 1, 8-DiamIno-o,6-clIthIaoctane 31 f • E i s(2- amino ethyl)di sulf ide 32 VI. Experimental. section 54 A. The coordinating ability of benzylamine, 54 2-thenylamine, and 2-furfury 1 amine 3. The coordination of bis(2-aminoethyl)sulfIde 40 C# The coordination of methyl 2-aminoethyl sulfide 47 D. The coordination of 1,8-diamino-3,6-dithiaoctane 53 B. The coordination of 1,3-diamino-2-propanol 59 F. The coordination of 2-aminoethyl mereaptan 64 G-. The coordination of bis (2- amino ethyl) disulfide 71 VII. Thermodynamics of complex formation 72 Summary 79 Appendix A -------- Calculation of acid dissociation constants of amines Appendix B -------- Calculation of formation constants of metal complexes I. INTRODUCTION Although that branch of inorganic chemistry which deals with metal complexes is a very extensive one, until recently most of the workers confined their investigations to the syn­ thetic and stereochemical aspects of these complexes. Lig­ ands of many types were synthesized and complexes of these ligands with various metal ions were prepared.^ This work led in a very general way to a better understanding of those factors which influence the stability of complexes, but with­ out quantitative data it was impossible to correlate much of the information. Abegg and Bodlander^ were among the firs t to investigate quantitatively the stabilities of several types of complexes. Prom their data they found that, in general, the stability of the complexes increased with an Increase in the electron­ egativity of the metal Ion. As yet it was not clearly recog­ nized, as Bjerrum has now shown, that complex formation Is a stepwise process. To understand the coordination process more completely it is necessary to consider the Individual steps as well as the overall process. The relatively small amount of work which has been done on the stabilities of com­ plexes is due In part to the lack of adequate experimental methods for carrying out such studies. The method developed by Bjerrum provides a new tool to carry out such Investiga­ tions with rapidity and accuracy in those systems in which it is applicable. With the publication or Bjerrum1s treatis Metal Ammine Formation in Aqueous Solution” in 1941 a new impetus was given to the study of the stability of complexes Bjerrum'-' has shown that one can determine the formation constants of metal ions with ligands that are either acidic or basic in nature by the measurement of the hydrogen ion activity in aqueous solutions containing a known amount of metal ion and coordinating agent. Rather extensive investi­ gations have been carried out using mono- and poly-amines^>4, 5,22 ancfi derivatives of salicylaldehyde as ligands. 6*30 work has revealed that there is a general order of stabili­ ties for the metal ions in complexes which is preserved although the ligand is varied. The question then arises, can ~a similar order of stabilities be observed for the atoms of the ligand which donate the electron pair for the forma­ tion of a metal-ligand bond? If such an order does exist, what is its variation from atom to atom? The major portion of the work undertaken here concerns itself with a study of the coordinating ability of sulfur as compared to nitrogen. To make such a comparison a number of amines containing sulfur in the form of a sulfide linkage were synthesized. This choice of compounds was made for several reasons: (1) one Is concerned with molecules which are sterically very similar to many polyamines which have already been studied; (2) the formation constants of these polyamines are available for comparison purposes; (3) the ligands are of the same charge type; (4) the rapid, simple, and accurate Bjerrum method can be used. Thermodynamic data were also obtained by determining the complexity constants at several temperatures. It was thus possible to obtain an Idea of the heats of formation and entropy changes involved In the coordination process. The metal ions used In the studies were all divalent except for silver. These ions were known to complex with polyamines such as ethylenedfamine• Because the data was to be compared with data obtained for polyamines, the metal Ions chosen were the same as those used In the studies with polyamines. II. METHODS FOR THE DETERMINATION OF COMPLEXITY CONSTANTS For* th© ©quilibrium process ^ M NA where M is th© metal ion and. A is the coordinated group (omitting charges on the ions wherever they occur), the com' plexity constant is defined by the expression There are many methods described in the literature whereby one can determine K^. I. Electrode potential measurements can be used when one of the species involved in the equilibrium is an Ion for which a reversible electrode can be constructed. II. Spectrophotometrically it is possible to determine formation constants if the compounds adsorb in a suitable region of the spectrum, the adsorption being proportional to the concentration of the complex• III* Solubility of slightly soluble salts in solutions of varying ligand concentration. IV* Distribution methods involving immiscible liquids such that the reaction can take place in only one or the liquids while one of the reactants is solu­ ble in both phases. Other methods have been used, such as transference techniques and meaaiirement of vapor tension, but all of the methods referred to above are rather tedious and frequently of limited applicability. V. The Bjerrum Method. Bjerrum3 has shown that, in general, the formation of a complex MA-^ Is stepwise such that one has to deal with a series of equili­ bria of the type M-f-A MA MA-t-A — MAg man_! + a ^==: man the individual formation constants are then given by and the overall formation constant; K^, sometimes called the complexity constant, Is the product of the Individual con­ stants •