@ 1974 KARL DEE SMITH ALL RIGHTS RESERVED ORGANOSCANDIUM CHEMISTRY by KARL DEE SMITH A DISSERTATION Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Chemistry in the Graduate School of The University of Alabama UNIVERSITY, AL1\BAMA 1973 --- e···· ACKNOWLEDGMENTS The author wishes to express his deep appreciation to: Dr. D. F. Smith and Dr. B. W. Ponder for their understanding, encouragement, and guidance throughout the course of this research. Steve Seale for his many hours spent in setting up a workable computer library to permit the completion of this work to become a reality. Merle Watson for his many services rendered in the making of the special glass apparatus needed throughout the course of this work. The computer operators, Steve Watson, Mike Webb, Bob McGwier, Al Martin, and Bill Gammon for their cooperation in efficiently running the hundreds of computer programs needed for the completion of this work. Sam Hassel, G. M. Nichols, and Harold Moore for their many services rendered in the maintenance, stockroom, and electronics fields, respectively. The secretaries for their services rendered. Segail Friedman for typing the final manuscript of this work. His wife, Becky, .and to Angela and Christopher for their confidence, encouragement, understanding, and love shown in every way. ii TABLE OF CONTENTS Page ACKNOWLEDGivIENTS • • ii LIS'l' OF TABLES . iv LIST OF FIGURES • vi Chapter I. INTRODUCTION 1 II. EXPERIMENTAL METHODS 9 Inert Atmosphere Glove Box . 9 Reagents and Solvents . • • • 9 Preparation of Compounds . • • • . • • • . 11 Preparation of Samples . • . • • • . • • 18 Computer Programs . • . • . • • . 19 Instrumentation ;, . • • • . • • • 20 III. RESULTS AND DISCUSSION 22 Dicyclopentadienylscandium Chloride Dimer . 22 Tricyclopentadienylscandium . • . • . 41 Trichlorotris(tetrahydrofuran)scandium . 63 Bis (indenyl) magnesium . • • . • • 84 IV. CONCLUSIONS . 112 REFERENCES ..•.• 114 I iii I ......___ LIST OF TABLES Table Page 1. Elemental Analysis of Scc1 . • • • • . • • 14 3 2. Elemental Analysis of Mg(C H ) • • • . • . 16 9 72 3. Elemental Analysis of Sc(C H ) . • . • 18 5 53 a,b 4. Final Atomic Positional Parameters for <c H ) ScCl . 27 [ 5 52 ]2 a, b 4 5. Anisotropic Temperature Factors (x 10 ) for [<c H ) sccl . 29 5 5 2 )2 6. Observed and Calculated Structure Factors for the Dicyclopentadienylscandium Chloride Dimer . 31 0 7. Interatomic Distances (A) and Angles (deg) for [<c H ) ••• • •••••••••• 37 5 5 2 scc1]2 8. Best Weighted Least-Squares Planes for [( CS HS ) 2 S cC 1] 2 • • • • • • • • • • • • 4 0 . a, b , .9 Fina. 1 Atomic Positiona1 Parameters for Tricyclopentadienylscandium. • . 48 a b 4 lo. A·niso t ropic· Tempera-uret Fae tors , (x 10 ) for Tricyclopentadienylscandium. • • . • . 49 11. Ob served and Calculated Structure Factor Amplitudes for Tricyclopentadienylscandium 50 0 12. Interatomic Distances (A) and Angles (deg) for Tricyclopentadienylscandium 55 iv } ; Table Page 13. Comparison of Metal-Cyclopentadienyl Carbon Bond Distances ... •. •• 57 14. Best Weighted Least-Squares Planes for Tricyclopentadienylscandium ..•.• 58 15. Comparison of Crystal Data for Sc(C H ) 5 5 3 and Sm(C H ) .•. .•••.••• 63 5 5 3 a 16. Final Atomic Positional Parameters for ScC1 (C H O) • . • • • • • . • • 69 3 4 8 3 . a, b 4 17. Anisotropi� Temperature Factors (x 10 ) for ScC1 (C H O) . • . • • . • • . • • 70 3 4 8 3 18. Observed and Calculated Structure Factors for Trichlorotris(Tetrahydrofuran)scandium • . • 71 0 19. Interatomic Distances (A) and Angles (deg) for ScC1 (C H O) . • • . • 79 3 4 8 3 20. Best Weighted Least-Squares Planes for ScC1 (C H o) . • • • • . • . 84 3 4 8 3 a, b 21. Final Atomic Positional Parameters for Diindenylmagnesium 91 a b 4 22. Anisotropic Temperature Factors , (x 10 ) for Diindenylmagnesium . • . 93 23. Observed and Calculated Structure Factor Amplitudes for Bis(indenyl)magnesium 95 0 24. Interatomic Distances (A) for Angles (deg) for Diindenylmagnesium 104 25. Best Weighted Least-Squares Planes for Diindenylmagnesium .•..••. •. 110 V i LIST OF FIGURES Figure Page 1. Molecular structure of the dicyclopenta­ dienylscandium dimer which lies in a general position in the unit cell •. • 33 2. Molecular structure of the dicyclopenta­ dienylscandium dimer which lies on a center of symmetry in the unit cell .• 35 3. Structure and unit cell packing of_ tricyclopenta­ dienylscandium. The atoms are displayed as the 50% probability ellipsoids for thermal motion • . • • • • • . • • • • • 52 '4. Bond distances and angles within the cyclopentadienyl groups for Sc(C H ) • . • • • • • • •••••• 60 5 5 3 5. The coordination sphere of the scandium ion with the 50% probability envelopes of the anisotropic thermal ellipsoids • .• 73 6. Molecular view of trichlorotris(tetrahydro­ furan)scandium with the 40% probability envelopes of the anisotropic thermal ellipsoids . 75 7. Structure and unit cell packing of trichlorotris­ (tetrahydrofuran)scandium. The atoms are displayed as the 40% probability ellipsoids for thermal motion . • • • . • 77 8. View looking down the Cl-Sc-0 axis displaying the configuration of the THF rings • . • • • 82 vi Figure Page 9. Illustration of magnesium(l) and its associated indenyl rings . .•••. 97 10. View of magnesium(2) and its associated indenyl rings . 99 11. Structure and unit cell packing of bis(indenyl)magnesium . 102 12. Bond distances and angles within the indenyl groups for Mg(C H ) .•.•.•.••..• 107 9 7 2 vii CHAPTER I INTRODUCTION The element scandium has been known for over one hundred years, but its coordination chemistry has been little studied. The lack of attention has been due, in part, to the difficulty of obtaining a pure source of scandium, although both the metal and oxide are now commercially available in high purity. Scandium is the first member of the 3d transition 1 2 series and has a 3d 4s ground state electronic configura­ tion. The +III oxidation state is the only one known. It is in many respects quite similar to yttrium and the lanthanides (1) although the di stinctly smaller radius of the scandium(III) ion affords some noteworthy difference s in chemistry. Several coordination compounds of scandium have been synthesized recently (2), although few structural character­ izations of scandium complexes have been reported. At the time this work was initia.ted only the structural character­ ization of the scandium formate complex (3), Sc(HCOO} , had 3 1 - 2 been reported. In this compound, -the scandium(III) ions are six-coordinate in a polymeric framework with formate ions acting as bridging groups. X-ray structural character­ izations of dicyclopentadienylscandium chloride (4), tricyclopentadienylscandium (5), and trichlorotris(tetra­ hydrofuran)scandium have now been carried out. In addition, the X-ray structure of tris(acetylacetonato)scandium(III) (6) has been recently reported. Other organoscandium compounds which have been characterized by means other than X-ray methods are dicyclo­ pentadienylscandium acetate, (c H ) ScOCOCH ; dicyclopenta­ 5 5 2 3 dienylscan.dium acetylacetonate, (C H ) ScAcac; (allyl) 5 5 2 dicyclopentadienyscandium, (c H ) sc(CH CH=CH ); and 5 5 2 2 2 (dicyclopentadienyl)phenylethynylscandium, (C H ) ScC=CPh 5 5 2 (7,8). Molecular weight measurements and infrared studies showed dicyclopentadienylscandium acetate to be · dimeric with bridging acetate groups. Dicyclopentadienylscandium acetylacetonate is monomeric and infrared studies showed the acetylacetonate to be bidentate. It was indicated that (allyl)dicyclopentadienylscandium was monomeric and the spin decoupled PMR spectrum confirmed the symmetrical nature of the allyl group. It was suggested that 3 (dicyclopentadienyl) phenylethynylscandium is associated to some extent with probably bridging PhC=C groups (9). Stable organoscandium compounds characterized so far are those containing anions in which unsaturation is present and TI bonding may occur between the organic anion and the scandium(III) ion. Attempts to synthesize alkyl-scandium compounds have met with limited success. There has been no confirmation (7) of the reported synthesis of Sc(Et)3-Et2o (10). The scandium-ethyl species' instability may be due to the alkene elimination reaction which is a well known method t i I of decomposition of transition metal alkyls (11). Recently, Witt and Melson (12) reported the synthesis of organoscandium I f compounds containing the trimethylsilylmethyl anion. This I anion has been used to prevent alkene elimination reactions and enable compounds containing transition metal-carbon I bonds to be isolated (11, 13, 14, 15). They isolated the two From available infrared and mass spectral evidence it was concluded that both compounds contain covalent Sc-C bonds. With the lack of unsaturation in the anion these bonds should be purely sigma in type. They propose that the com­ pounds are polymeric with both terminal and bridging 4 trimethylsilylmethyl anions where the terminal Sc-C bonds are 2-electron, 2-center bonds whereas the bridging bonds are weaker 2-electron, 3-center bonds. The isolation of these compounds containing Sc-C sigma bonds suggests that the instability of the scandium­ ethyl species is due to a facile decomposition process, e.g., ethylene elimination (16) rather than an instability inherent with scandium-carbon bonds. The structural studies of many organoscandium com­ plexes should determine their potential catalytic applica­ bility. In view of the importance of other first row transi­ tion elements