THE CHEMISTRY OF SOME LEWIS ACID-BASE ADDUCTS OF PENTAB0RANE(9) AND HEXABORANE(10) DISSERTATION Presented In Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University By Michael Lee Denniston, B.A., M.Sc * % * * * * The Ohio State University 1970 Approved by Adviser Department of Chemistry ACKNOWLEDGMENTS I would like to express my appreciation to Dr. Sheldon.Shore for his continued encouragement through­ out my graduate career. 1 am indebted to my many friends and colleagues for their warm friendship and professional assistance. My late Father, my Mother, Ann and Nicky deserve special appreciation for their unfailing patience and moral support, This work was financed by a grant from the National Science Foundation. ii VITA August 29, 19^^ Born - Odessa, Texas 1966 . B.A., Knox College, Galesburg, Illinois 1966-1968 . o Teaching Assistant, Department of Chem­ istry, The Ohio State University, Columbus, Ohio 1968 . o . M.Sc., The Ohio State University, Columbus, Ohio 1968-1970 . , . Research Assistant, Department of Chem­ istry, The Ohio State University, Columbus, Ohio PUBLICATIONS M. L. Denniston and S. G. Shore, Abstracts from 158th National Meeting of the American Chemical Society, New York, N.Y., September, I969. Paper No. INOR 104 FIELDS OF STUDY Major Field: Inorganic Chemistry Studies in the Chemistry of Boron Hydrides. Professor Sheldon G. Shore Studies in the Chemistry of the Group III and Group IV Elements: Professor Eugene P. Schram Studies in the Chemistry of Transition Metals: Profes­ sors Daryle H. Busch, Andrew Wojcicki, and Devon Meek iii TABLE OF CONTENTS Page ACKNOWLEDGMENTS ....................................... ii VITA .......................................................iii LIST OP T A B L E S ................. viii LIST OF ILLUSTRATIONS................................ ix INTRODUCTION ............................................ 1 I. LEWIS ACID-BASE CHEMISTRY OF PENTABORANE(9) . 2 II. LEWIS ACID-BASE CHEMISTRY OF HEXABORANE(10) . 5 III. STATEMENT OF THE PROBLEM ..... ............. 6 EXPERIMENTAL ........................................... 7 I. APPARATUS .................................. 7 A. The Vacuum System and Inert Atmosphere Equipment II. PHYSICAL AND CHEMICAL MEANS OF CHARACTER­ IZATION ....................................... 9 A. Nuclear Magnetic Resonance Spectra B. Infrared Spectra C. X-Ray Powder Patterns D. Mass Spectra E. Cryoscopic Molecular Weight F. Analyses G. Hydrolyses H. Melting Points III. SOLVENTS AND REAGENTS . ...................... 15 IV. LEWIS ACID BASE ADDUCTS OF PENTABORANE(9) . l8 IV TABLE OP CONTENTS (Contd.) Page A. The Reaction of Pentaborane(9) with TrimethyIphosphine 1. The Reaction in Absence of Solvent 2. The Reaction in the Presence of Solvent; the Preparation of a) The Reaction of BsjHgCPCCHgjglg with Excess Lewis Base b) The Characterization of the Adduct (CHgjgPBgH^PCCHg)] c) The Attempted Reaction of B5Hg[P(CH2 )3]2 with 2-Butyne d) The Attempted Reaction of B^Hg[P(CH3 )3]2 with Hydridic Reagents B. The Reaction of Pentaborane(9) with DimethyIphosphine 1. The Preparation of B^Hg[P(GH3,)2H]2 a) The Addition of Excess Lewis Base to B^HgCPCCHgïgH]., b) The Pyrolysis of B3Hg[P(CHg)2H ]2 C. The Attempted Formation of a Penta­ borane (9) - Phosphine Adduct D. The Reaction of Pentaborane(9) with TriphenyIphosphine E. The Reaction of Pentaborane(9 ) with a Ditertiary Phosphine, 2PCR2OE2? 2 F. Reaction of Pentaborane(9) with Trimethyla­ mine TABLE OF CONTENTS (Contd.) Page 1. Preparation of B^HgCNfCHg):;]^, V. LEWIS ACID-BASE ADDUCTS OF HEXABORANE(IO) .... 56 A. The Reaction of Hexabcrane(10) with TrimethyIphosphine 1. Preparation of BgH2^Q[P(CH^)g]2 a) Reaction of Excess Lewis Base with BgH^Q[P(CH2 )g]2 B. Attempted Formation of a Hexahorane- Phosphine Adduct C. Reaction of Hexaborane(lO) with TriphenyIphosphine 1. Preparation of DISCUSSION................................................ 71 I. THE ROLE OF SOLVENT IN THE REACTION OF PENTABORANE(9) AND TRIMETHYLPH08PHINE ......... 71 II. THE EFFECT OF LEWIS BASE STRENGTH ON THE STABILITY OF A GIVEN A D D U C T .................... 73 III. THE EFFECT OF LEWIS ACID STRENGTH ON THE STABILITY OF A GIVEN A D D U C T .............................. 75 IV. PROPOSED STRUCTURES OF THE PENTAB0RANE(9) AND HEXABORANE(IO) ADDUCTS .......................... 76 A. The Equations of Balance B. The Proposed Structure of BcHg[P(CHo)g]2 C. The Proposed Structure of BcHg[N(CHo)3]2 D. The Proposed Structure of BgH^QEPCCH^;^J2 V. THE REACTION OF B j-Hq [P(CHo ),]p WITH A THIRD MOLE OF LEWIS BASE . 7 ........................ 101 Vi TABLE OF CONTENTS (Contd.) Page VI. THE REACTION OF B6H2o[P(CHg)g]2 WITH EXCESS LEVFES B A S E ........................................ 109 SUMMARY .......................o ..........................112 BIBLIOGRAPHY................ Il4 vil LIST OP TABLES Table Page 1 . X-Ray Powder Data for B^Hg[P(CH2 )g]2 . 22 2 . Mass Spectral Data for B^H^CP(CH^)^^2 * * * ... 24 3. Mass Spectral Data for (CH2 )2PB2H%P(CH2 )g . ... 34 4. X-Ray Powder Data for (CH2 )gPB2H^P(CHg)2 . 42 5. X-Ray Powder Data for igPCzHyPCCgHsig] ............. 51 6 . X-Ray Powder Data for B^Hg[N(CHg)g]2 . • . 55 7. Mass Spectral Data for BGH^QCPCCHg)^]^, . 60 8. X-Ray Powder Data for BgHio[P(CHg)3]2 . 64 9. X-Ray Powder Data for BgHiQ[P(CgH^)g]2 • . 69 10. Reaction of Excess Lewis Base with BgHgCPCCHgiglg .......................... 101 11. Reaction of Excess Lewis Base with B6H^q [P(CH3)3]2 .......................... 110 viii LIST OP ILLUSTRATIONS Figure Page 1. Tensiometric Titration for the System ............................ 20 2. The Mass Spectrum of BgH^[P(CH2)3 ] 2 .............. 28 3. The Infrared Spectrum of B^Hg[P(CH3 )3 ] 2 ......... 29 4. The Mass Spectrum of (CHgjgPBgH^PCCHg)^ ..... 39 5. The Infrared Spectrum of (CHgjgPBgH^PCCHg)] . 4l 6. The Infrared Spectrum of B^Hg[P(CHg)2H ]2 .... 46 7. The Infrared Spectrum of B5Hg[(CgH^)2PCH2CH2P(CgH^)2] ................. 50 8. The Infrared Spectrum of B^Hg[N(CH3 )3]2 ......... 54 9. Tensiometric Titration for the System .......................... 57 10. The Mass Spectrum of BgH2oCP(CH2 )3 ] 2 ........... 59 11. The Infrared Spectrum of BgH^Q[P(CH3 )3]2 .... 65 12. The Infrared Spectrum of BgHQ_Q[P(CgH^)2]2 . 70 13. Some Possible Structure for the B^H^î Anion . 80 14. The Boron-11 and Proton NMR Spectra of B^H^CPCCH^)^]^ ................................. 82 15. The Boron-11 NMR Spectrum of 2I2 upon Simultaneous Irradiation at 60 MHz .... 84 16. The Boron-11 NMR Spectrum of B^Hg[N(CH3)3]2 at Low Temperature ................. 87 17. The Proton NMR Spectrum of BcHq[N(CHo)q]2at - 2 0 ° 88 ix LIST OP ILLUSTRATIONS (Contd.) Figure Page 18. Some Possible Structures for the Anion . 93 19. The Boron-11 and Proton NMR Spectrum of BgHioC (UH3)3]2 at Room T e m p e r a t u r e ........... 95 20. The Boron-11 NMR Spectrum of B^H]^o[P(CH2)g]2 upon Simultaneous Irradiation at60 MHz .... 96 21. The Boron-11 NMR Spectrum of BgH]_o[P(CHo)o]2 at Low T e m p e r a t u r e ................... 97 22. The Boron-11 NMR Spectrum of BgHiQ[P(CH3)3]2 at 55* 98 23. The Boron-11 and Proton NMR Spectra of (CHgigPBgH^PfCHg)] ......................... 105 INTRODUCTION In recent years there has been a great deal of research concerning reactions of Lewis bases with a number of boron hydrides (1). The majority of the pub­ lished literature in this area has described the inter­ action of diborane(6), tetraborane(lO) and decaborane(l4) with such Lewis bases as substituted amines or phosphines However, until the present time very little has been known concerning the addition of Group V Lewis bases to the boron hydrides pentaborane(9) or hexaborane(10). I. LEWIS ACID-BASE CHEMISTRY OF PENTAB0RANE(9) The manner in which Lewis bases such as amines and phosphines Interact with pentaborane(9) has been unknown for a number of years. The reactions which have been reported are quite complex and the products often depend upon such factors as temperature, ratio of reactants, and the strength of the Lewis base used (1). The additions of trimethyIphosphine, triphenyl- phosphine and trimethylamine to pentaborane(9) which have been previously reported, illustrate the influence of these factors on the reaction products. Burg (2) has reacted pentaborane(9) with excess trimethyIphosphine at 200°C and obtained trime thyIphos- phine-borane, a trace of hydrogen and a polymeric material. Several years later, Jeffers (3) found that by reacting either trimethyIphosphine or triphenyIphosphine with pentaborane(9) at room temperature, he could obtain a white adduct of empirical formula B^H^L2 (L = PCCgH^)^ or PCCHg)^). Hough (4) confirmed this formulation and reported that upon standing, these compounds decomposed to B^HgL and BHgL species. Recently a group of Russian workers (5) have reported that pentaborane(9) and trl- niethyIphosphine reacted at low temperature in a 1:5 ratio to form initially B^Hg[P(CH2 )2]2 , on warming decom­ posed to trimethyIphosphine-borane and a polymeric sub­ stance. The reaction of pentaborane(9) and excess tri- methylamine has been carefully studied by Burg (6). He has found that by mixing the two species at -79° a white solid adduct of composition B^Hg[N(CHg)^2 was formed. The adduct which was formed decomposed at room temperature to give a yellow polymeric substance and trimethylamine- borane, A paper which was published that same year by several Russian chemists (7) has reported identical prop­ erties for this 2:1 adduct Although certain nitrogen-containing bases have been shown to be weaker than the analogous phosphine bases (8) toward borane (BHg), the only stable adduct of pentaborane ( 9 ) with a Group V Lewis base was reported in a paper by Muetterties (9) as a 1:1 adduct of pentaborane (9) and N, N, N* N*tetramethylethylenediamine.