Alkylation of Boron Hydrides

This dissertation has been 62-830 microfilmed exactly as received HARRIS, Samuel William, 1930- THE ALKYLATION OF BORON HYDRIDES. The Ohio State University, Ph.D., 1956 Chemistry, inorganic University Microfilms, Inc., Ann Arbor, Michigan THE ALKYLATION OF BORON HYDRIDES DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio S tate U n iv ersity By SAMUEL WILLIAM HARRIS, B. A., M. S. ii ii ti it 11 tt The Ohio S tate U n iv ersity 1956 Approved by: Deparwn^it of Chemistry ACKNOWLEDGEMENT The author wishes to express his appreciation to Professors A. B. Garrett and H. H. Sisler for their guidance during the course of this investigation. He would also like to thank Dr. John Norman of Olin-Mathieson for the mass spectrographic analysis of one of the compounds prepared. He would also like to express his appreciation to other members of Research Foundation Project 116-D for the cooperation which was received in various phases of his work. TABLE OF CONTENTS Page I . P u rp o s e.............. 1 II. Historical ............................ ...................................................... 2 A. P rep aratio n 3 B. Chemical P ro p e rtie s 3 C. Structure 6 III. Experimental Techniques ............................................................... 9 A. High Vacuum System 9 B. Experimental Procedures 15 1. Reaction Procedures 15 2. Analysis of the Reaction 18 3. Analytical Methods 22 4. Physical. Characterization 25 C. M aterials 26 IV. Experimental Results ............................................................ 30 A. Reactions of Decaborane 30 1. Friedel-Crafts Reactions 30 2. Grignard Reaction 40 B. Reactions of Pentaborane 40 1. Pentaborane and Methyl Iodide 40 2. Pentaborane and Methyl Chloride 50 3. Pentaborane and Methyl Bromide 51 4. Pentaborane and Ethyl Iodide 52 5. Pentaborane and Ethyl Chloride 60 6. Pentaborane and Ethyl Bromide 61 7. Pentaborane and Methylene Iodide 63 8. Pentaborane and Formaldehyde or Paraformaldehyde 65 i i i TABLE OF CONTENTS (c o n t.) Page C. Reactions of sec-But.ylpentaborane 66 D. Reactions of Pentaborane and Methylpenta- borane with Halides . 75 1. Pentaborane and Hydrogen Halides 75 2. Methylpentaborane and Hydrogen Halides 75 3. Methylpentaborane and Methyl Halides 75 V. Discussion and Conclusions ................................... BO A. General 80 B. S tru ctu re 82 C. Theory of Reaction 84 VI. Summary................... 91 Bibliography 93 Autobiography 95 iv LIST OF TABLES Table Page I. Reactions of Decaborane with Methyl Iodide ............................. 31 II. Reactions of Decaborane with Ethyl Iodide ............... .; .............34 III. Reaction of Decaborane with Ethylene .............................. 38 IV. Reactions of Pentaborane with Methyl Iodide ......................... 43 V. Vapor Pressure of Methylpentaborane-9 ............................... 47 VI. Reaction of Pentaborane with Methyl Chloride ........................ 51 VII. Reaction of Pentaborane with Methyl Bromide ............................ 52 VIII. Reactions of Pentaborane with Ethyl Iodide .......................... 54 IX. Vapor Pressure of Ethylpentaborane-9 ................. 58 X. Reaction of Pentaborane with Ethyl Chloride .......................... 61 XI. Reaction of Pentaborane with Ethyl Bromide .......... 62 XII. Reaction of Pentaborane with Methylene Iodide ........... 64 XIII. Reaction of sec-Butylpentaborane with Methyl Chloride ... 66 XIV. Vapor Pressure of Methyl-sec-but ylpentaborane 72 XV. Reactions of Pentaborane with Hydrogen Chloride .................. 76 XIV. Reactions of Pentaborane with Hydrogen Halides .................. 77 XVII. Reactions of Methylpentaborane with Hydrogen Halides .... 78 XVIII. Reactions of Methylpentaborane with Methyl Halides 79 v LIST OF ILLUSTRATIONS Figure Page 1. Structure of Pentaborane ..................................................... .. 7 2. Structure of Decaborane ...................................................... ................8 3 . Vacuum S y stem.......................... 11 4. Fractionation Train ............................................ 12 5 . Reaction Vessel ....................................................... 14 6. Tube Opener ..................... 14 7. Carbon Dioxide Train .............................................................................. 16 8. Infrared Spectrum of Fraction 1, Reactions 19 and 20 ............ 33 9. Infrared Spectrum of Fraction 3> Reactions 19 and 20 ...............33 10. Infrared Spectrum of Fraction 2, Reactions 21 and 22 ...... 36 11. Infrared Spectrum of Fraction 3> R eactions 21 and 2 2 ...............36 12. Infrared Spectrum of Decaborane ....................................................... 37 13. Infrared Spectrum of Methylpentaborane ........................ 45 14. Infrared Spectrum of Pentaborane .......................... 46 15. Vapor Pressure of Methylpentaborane-9 ........................ 49 16. Infrared Spectrum of Ethylpentaborane-9 ......................... 56 17. Vapor Pressure of Ethylpentaborane-9 ...................... 57 18. Infrared Spectrum of Methyl-sec-butylpentaborane .................... 69 19. Infrared Spectrum of sec-Butylpentaborane ........................... 70 20. Vapor Pressure of Methyl-sec-but ylpentaborane .................. 74 v i THE A1KYLATI0N OF THE BORON HYDRIDES I . Purpose The purpose of this work was the preparation of alkyl derivatives of pentaborane-9 and decaborane. In planning this work, there was very little previous work to serve as a guide. However, two possible syntheses of alkyl derivatives of pentaborane and decaborane were proposed. They a re : 1. A halogen derivative of the boron hydride was to be prepared and then be reacted with an organom etallic compound such as the Grignard reagent; + nX2 y BioHi4— + BiQHi4_nXn + nRMgX nB^n + 2. A study was to be made of the reaction of an alkyl halide with the boron hydride in the presence of and in the absence of c a ta ly s ts ; B5H9 + nRX Bsffe^Rn + nHX B10H14 + nRX sa t B T o H ^ n R n + nHX . 1 II. Historical The volatile hydroborons were first prepared and characterized by A. Stock"*" and co-workers in the early 1900*s. He reported 1. Stock, A., "The Hydrides of Silicone and Boron," Cornell University Press, Ithaca, New York, 1933. the volatile compounds B2H6, Bi,.Hl0, B5Ife, B5Hn , B6H10 and B ^H ^. These compounds have the following physical properties. Name Formula Melting Point Boiling Point Diborane b2h 6 -165.5 -92.5 Tetraborane B4H10 -120 16 Pentaborane-9 B5H9 -48.6 58 Pentaborane-11 B5Hn -123 65 Hexaborane BgHto -65 — Decaborane B10Hii* 99.5 213 These volatile hydroborons have aroused a great deal of interest because of their unusual formulas and their chemical properties. Extensive studies have been made on the chemistry of these compounds. This work has dealt chiefly with aiborane and is well summarized by Stock-'-, and in a review by Schlesinger and Burg^. Most of this work is of only slight interest here, and will 2. Schlesinger and Burg, Chem. Rev.. 31» 1 (1942). not be repeated in detail, but w ill be only summarized, with 2 3 emphasis on the points which are of interest for the present work. A. Preparation The modern method for preparation of diborane involves the reduction of boron halides by hydrides such as sodium hydride or lithium aluminum hydride. The other boron hydrides are then pre pared from diborane. Tetraborane is the chief product of the slow decomposition of diborane which occurs at ordinary temperatures. The other boron hydrides are prepared by the pyrolysis of diborane at higher temperatures, the yields of the various hydrides being dependent upon the conditions of the pyrolysis. B. Chemical P ro p erties Thermal Stability. The most stable of the hydroborons are pentaborane-9 and decaborane, which do not decompose until temperatures of about 170°C. The other hydroborons decompose at much lower temperatures into other hydrides and hydrogen. Reducing Agents and Lewis Acids. The hydroborons are very powerful reducing agents. All of them react with oxygen and water at ordinary temperatures, the reaction with oxygen being explosive w ith a l l except w ith decaborane, which re a c ts b u t slowly. Oxygen does not react to give complete oxidation of the boron to boric acid. Reaction with water leads to the formation of hydrogen and boric acid quantitatively if the hydrolysis is carried out for a sufficient length of time. With diborane, hydrolysis is complete in a few seconds, but pentaborane-9 and decaborane require several days at 100°C to insure complete hydrolysis. This reaction is used for analysis of the hydroborons and their derivatives. The hydroborons react vdth the halogens to replace one or more of the hydrogens vdth a halogen; the number of hydrogens which are replaced is dependent upon the halogen and hydroboron involved. The best characterized products are those from diborane and deca borane. Diborane vdth chlorine gives boron trichloride, but vdth bromine and iodine, monohalides of diborane are obtained. Deca borane with iodine gives a diiododecaborane which has been shown to have the same basic structure as decaborane itself-^. Other higher 3. Schaeffer, R., Abstracts of Papers Presented at the Cincinnati Meeting of the American Chemical Society, 1955 » P» 37Q. iodinated derivatives have been prepared, but these are not as well characterized. Bromo derivatives of decaborane are formed by the action of bromine on decaborane, but these are not as well characterized as the

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