Synthesis and Characterization of Molecules and Π

SYNTHESIS AND CHARACTERIZATION OF MOLECULES AND π- CONJUGATED MATERIALS CONTAINING LOW-COORDINATE PHOSPHORUS By XUFANG CHEN Submitted in partial fulfillment of the requirements For the degree of Doctor of Philosophy Thesis Advisor: Dr. John D. Protasiewicz Department of Chemistry CASE WESTERN RESERVE UNIVERSITY January, 2005 CASE WESTERN RESERVE UNIVERSITY SCHOOL OF GRADUATE STUDIES We hereby approve the dissertation of ______________________________________________________ candidate for the Ph.D. degree *. (signed)_______________________________________________ (chair of the committee) ________________________________________________ ________________________________________________ ________________________________________________ ________________________________________________ ________________________________________________ (date) _______________________ *We also certify that written approval has been obtained for any proprietary material contained therein. ii Table of Contents Dedication ………………………………..………………………………………... i Table of Contents ………………………………………………………………….. ii List of Tables ……………………………………………………………………… v List of Figures ……………………………………………………………………... vi List of Schemes ……………………………………………………………………. x Acknowledgements ………………………………………………………………... xiv List of Abbreviations ……………………………………………………………… xv Abstract ……………………………………………………………………………. xvii Chapter 1. Introduction..………………………………………………………... 1 1.1 Compounds with Multiple Bonds of Heavier Main Group Elements 1 1.1.1 Short History……………………………………………………….. 1 1.1.2 Recent Developments………………………………………………. 6 1.2 Bonding in Heavier Main Group Elements………………………… 10 1.3 Carbon-Phosphorus Analogy……………………………………….. 13 1.4 Proposed Work……………………………………………………… 18 1.4.1 Reactivity study of phosphanylidene-σ4-phosphoranes…………….. 18 1.4.2 Conjugated oligomers and polymers containing low-coordinate phosphorus centers…………………………………. 20 1.4.3 Synthesis of DmpPF2 and its reactivity study………………………. 26 1.5 References…………………………………………………………... 28 iii 4 Chapter 2. Cycloaddition of Phosphanylidene-σ -phosphoranes ArP=PMe3 and Quinones to Yield 1,3,2-dioxaphospholanes…………………… 37 2.1 Introduction…………………………………………………………. 37 2.2 Results and Discussion……………………………………………… 40 2.3 X-ray Structural Analysis…………………………………………… 44 2.4 NMR Spectroscopic Analyses……………………………………… 47 2.5 Possible Mechanisms……………………………………………….. 53 2.6 Conclusions…………………………………………………………. 55 2.7 Experimental Section……………………………………………….. 56 2.8 References………………………………………………………….. 60 Chapter 3. A Cyclic Diphosphinite by a Formal [4+4] Cycloaddition Reaction of β-phosphaenone………………………………………………….. 62 3.1 Introduction…………………………………………………………. 62 3.2 Results and Discussion……………………………………………... 63 3.2.1 Synthesis of a Cyclic Diphosphinite………………………………... 63 3.2.2 X-ray Structural Analysis of the Cyclic Diphosphinite 6…………... 64 3.3 NMR Spectroscopic Studies………………………………………... 67 3.4 Possible Mechanism………………………………………………… 74 3.5 Conclusions…………………………………………………………. 75 3.6 Experimental Section……………………………………………….. 76 3.7 References…………………………………………………………... 78 Chapter 4. Synthesis of meta-Terphenyl Iodo and Dichlorophosphine Derivatives Bearing Methoxy Groups……………………………… 80 iv 4.1 Introduction…………………………………………………………. 80 4.2 Results and Discussion……………………………………………… 81 4.2.1 Synthesis and NMR Spectroscopic Analysis of m-Terphenyl Iodides Bearing Methoxy Groups………………………………….. 81 4.2.2 X-ray Crystal Structures of m-Terphenyl Iodides Bearing Methoxy Groups…………………………………………………… 84 4.2.3 Synthesis of m-terphenyl Dichlorophosphines Bearing Methoxy Groups……………………………………………………. 86 4.3 Conclusions…………………………………………………………. 92 4.4 Experimental Section……………………………………………….. 93 4.5 References…………………………………………………………... 99 Chapter 5. Synthesis and Characterization of 2,6-Dimesitylphenyl Difluorophosphine………………………………………………….. 101 5.1 Introduction…………………………………………………………. 101 5.2 Results and Discussion……………………………………………… 101 5.2.1 Synthesis and NMR Spectroscopic Studies of DmpPF2……………. 101 5.2.2 Reactivity Studies of DmpPF2………………………………………. 104 5.2.3 X-ray Crystal Structure of DmpPF2………………………………… 106 5.3 Conclusions…………………………………………………………. 108 5.4 Experimental Section……………………………………………….. 110 5.5 References…………………………………………………………... 113 Chapter 6. Synthesis and Characterization of Phosphaalkene Polymers……….. 115 6.1 Introduction…………………………………………………………. 115 v 6.2 Results and Discussion……………………………………………... 120 6.3 Synthesis of New Tetraarylphenyl Difunctional Ligands………….. 129 6.4 Conclusions………………………………………………………… 131 6.5 Experimental Section……………………………………………….. 133 6.6 References………………………………………………………….. 138 Chapter 7. Synthesis and Characterization of Phosphaalkenes and Phosphaalkynes……………………………………………………... 143 7.1 Introduction…………………………………………………………. 143 7.1.1 General Introduction of Phosphaalkynes…………………………… 143 7.1.2 Synthesis of Phosphaalkynes……………………………………….. 145 7.1.3 Reactivity and Coordination Chemistry of Phosphaalkynes……….. 146 7.2 Results and Discussion……………………………………………… 149 7.2.1 Synthesis and Characterization of m-Terphenyl Phosphaalkenes and Phosphaalkynes………………………………. 149 7.2.2 X-ray Crystal Structure Analysis of DmpC≡P……………………... 156 7.2.3 Reactivity of Dibromophosphaalkenes and Phosphaalkynes………. 157 7.3 Proposed Mechanism for the Formation of Phosphaalkynes………. 159 7.4 Synthesis of Br2C=PC6(p-t-BuPh)4P=CBr2………………………… 162 7.5 Conclusions………………………………………………………… 167 7.6 Experimental Section………………………………………………. 169 7.7 References………………………………………………………….. 174 Bibliography ………………………………………………………………………. 178 vi List of Tables Table 1 Relative energies (kcal/mol) of σ and π bonds in group 14 and 15 homonuclear double bonds ……………………………………………. 12 Table 2 Selected bond lengths and angles for DmpPF2…………………………. 107 Table 3 Selected IR data of simple phosphaalkenes……………………………. 126 Table 4 Selected phosphaalkynes synthesized by elimination of hexamethyldisiloxane and their physical properties ………………….. 145 vii List of Figures Figure 1 Schematic representation of the s-p energy separation and orbital sizes for 2nd and 3nd row elements………………………………….. 12 Figure 2 Schematic diagram for band gaps in alkenes, phosphaalkenes……... 13 Figure 3 Highest occupied molecular orbitals of imine and phosphaethylene.. 14 Figure 4 Representations of singlet and triplet states of phosphinidenes and carbenes………………………………………………………… 16 Figure 5 Schematic cartoon of the band gaps in conjugated alkene and phosphaalkene systems………………………………….. 22 Figure 6 Structural diagram for 3,4,5,6-tetrachlorobenzo-2-(2,6-dimesitylphenyl)-1,3,2-dioxaphospholane, 3a……………………………….. 45 Figure 7 Packing diagram for 3,4,5,6-tetrachlorobenzo-2-(2,6-dimesityl-phenyl) -1,3,2-dioxaphospholane illustrating π-stacking in the crystal……... 46 Figure 8 Structural diagram for 3,5-di-tert-buytlbenzo-2-(2,6-dimesitylphenyl)-1,3,2-dioxaphospholane, 4a……………………………….. 46 Figure 9 31P NMR spectrum of 3,4,5,6-tetrachlorobenzo-2-(2,6-dimesitylphenyl)-1,3,2-dioxaphospholane, 3a in CDCl3…………………….. 47 Figure 10 31P NMR spectrum of 3,4,5,6-tetrachlorobenzo-2-(2,4,6-tri- tert-butylphenyl) -1,3,2-dioxaphospholane, 3b in CDCl3………….. 48 Figure 11 31P NMR spectrum of 3,5-di-tert-buytlbenzo-2-(2,6-dimesitylphenyl)-1,3,2-dioxaphospholane, 4a in CDCl3…………………….. 48 Figure 12 31P NMR spectrum of 3,5-di-tert-butylbenzo-2-(2,4,6-tri- viii tert-butylphenyl)-1,3,2-dioxaphospholane, 4b in CDCl3…………... 49 1 Figure 13 H NMR spectrum of 1,3,2-dioxaphospholane, 3a in CDCl3………. 50 1 Figure 14 H NMR spectrum of 1,3,2-dioxaphospholane, 4a in CDCl3………. 52 Figure 15 Low field (aromatic range) of 1H NMR spectrum of 1,3,2-dioxaphospholane, 4a in CDCl3……………………………… 52 Figure 16 High field (methyl range) of 1H NMR spectrum of 1,3,2-dioxaphospholane, 4a in CDCl3……………………………… 53 31 Figure 17 P NMR spectrum for the reaction mixture of DmpP=PMe3 with acenaphthoquinone in CHCl3…………………………………. 64 Figure 18 ORTEP drawing of one of the independent molecules of cyclic diphosphinite 6………………………………………………. 65 Figure 19 Structure of the eight-membered ring in 6 and schematic structure of the lowest energy configuration of 1,5-cyclooctadiene………….. 66 Figure 20 The π – π interactions between two molecules in the crystal unit cell 66 31 Figure 21 P NMR spectrum of cyclic diphosphinite 6 in CDCl3……………. 69 1 Figure 22 H NMR spectrum of cyclic diphosphinite 6 in CDCl3…………….. 69 1 1 Figure 23 H- H COSY spectrum of cyclic diphosphinite 6 in CD3COCD3…. 70 1 Figure 24 Variable temperature H NMR spectra for compound 6 in C6D5Br.. 73 Figure 25 1H NMR spectrum of 2,6-di(2,6-dimethoxyphenyl)iodobenzene in CDCl3……………………………………………………………. 83 Figure 26 1H NMR spectrum of 2,6-di(2,4,6-trimethoxyphenyl)iodobenzene in CDCl3……………………………………………………………. 83 Figure 27 ORTEP drawing of 2,6-di(2,6-dimethoxyphenyl)iodobenzene, 7….. 85 ix Figure 28 ORTEP drawing of 2,6-di(2,4,6-trimethoxyphenyl)iodobenzene, 8... 86 Figure 29 31P NMR spectrum of 2,6-di(2,6-dimethoxyphenyl) phenyldichlorophosphine in CDCl3……………………………….. 88 Figure 30 2,6-di(2,6-dimethoxyphenyl)phenyldichlorophosphine……………. 91 31 1 Figure 31 P { H} NMR spectrum of DmpPF2 in CDCl3……………………. 103 1 Figure 32 H 600 MHz NMR spectrum of DmpPF2 in CDCl3………………... 103 1 Figure 33 H 300 MHz NMR spectrum of DmpPCl2 in CDCl3……………….. 104 Figure 34 X-ray crystal structure of DmpPF2…………………………………. 108 Figure 35 Two possible orientations for PF2 unit in DmpPF2……………….... 108 Figure 36 UV-vis Absorption spectra of soluble polymer 10d and its oligomer A in CHCl3……………………………………………….. 124 Figure 37 Fluorescence spectra of soluble polymer 10d and its oligomer A (CHCl3) relative to (E)-stilbene…………………………………….

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