Degree Type

Dissertation

Date of Award

1992

Degree Name

Doctor of Philosophy

Department

Chemistry

First Advisor

Robert J. Angelici

Abstract

Sulfur coordinated thiophene ([eta][superscript]1(S)-Th) complexes of (Cp(CO)(L)Ru([eta][superscript]1(S)-Th) (BF[subscript]4 (L = CO or PPh[subscript]3 and Th = T, 2-MeT, 3-MeT, 2,5-Me[subscript]2T, Me[subscript]4T, benzo (b) thiophene (BT) and dibenzothiophene (DBT)) have been synthesized. Equilibrium constants, K[superscript]', for the displacement of thiophene (T) by methyl-substituted thiophenes and BT, Cp(CO)[subscript]2Ru([eta][superscript]1(S)-T)[superscript]+ + Th leftharpoons Cp(CO)[subscript]2Ru([eta][superscript]1(S)-Th)[superscript]+ + T, increase with an increasing number of methyl groups in the thiophene: T(1.00) 2-MeT (410) > BT (100) > 2,5-Me[subscript]2T (23). Rate constants (10[superscript]6k[subscript]1, s[superscript]-1) for thiophene dissociation in the analogous Cp(CO)(PPh[subscript]3)Ru([eta][superscript]1(S)-Th)[superscript]+ complexes decrease as follows: T (1400) > 2-MeT (220) > 3-MeT (170) > 2,5-Me[subscript]2T (130) > BT (70) > DBT (17) > Me[subscript]4T (5.8). In general, methyl groups on the thiophene (Th) increase K[superscript]' and decrease k[subscript]1 which suggests that electron-releasing methyl groups thiophene binding to the metal. Trends in K[superscript]' and k[subscript]1 follow those of thiophenes adsorbing to HDS catalysts;The 2-benzothienyl complexes, Cp(PMe[subscript]3)[subscript]2Ru(2-BTyl) (1) and Cp(CO)(PPh[subscript]3)Ru(2-BTyl) (2) are prepared form reactions of 2-benzothienyllithium with Cp(PMe[subscript]3)[subscript]2RuX (X = Cl, CF[subscript]3SO[subscript]3) and Cp(CO)(PPh[subscript]3)RuCl. Protonation of 2 with CF[subscript]3CO[subscript]3H gives the [eta][superscript]1(S)-benzo (b) thiophene(BT) complex Cp(CO)(PPh[subscript]3)Ru([eta][superscript]1(S)-BT)[superscript]+ (4). The analogous protonation of 1 appears to initially add H[superscript]+ to the S atom in the BTyl ligand; this intermediate subsequently rearranges to the [eta][superscript]1(S)-BT complex, Cp(PMe[subscript]3)[subscript]2Ru([eta][superscript]1(S)-BT[superscript]+ (3). These reactions suggest a possible pathway for deuterium exchange in the 2-position of benzothiophene over hydrodesulfurization catalysts;The deuterodesulfurization (DDS) of thiophene was investigated over PbMo[subscript]6.2S[subscript]8 at 400°C using a flow-microreactor. The product 1,3-butadiene (BDE), which is likely to be the first desulfurized product under these conditions, was analyzed for deuterium content by [superscript]2H NMR and mass spectrometries. At different levels of thiophene conversion (0.86-10.2%), the amount of deuterium incorporated into BDE remains constant at 3.47 D atoms per BDE molecule. Unconverted thiophene incorporates 0.42 D atoms at 10.2% thiophene conversion but only 0.05 D atoms at 0.86% conversion. Reaction of 2,5-dihydrothiophene (2,5-DHT) with D[subscript]2 at 200°C over PbMo[subscript]6.2S[subscript]8 liberates BDE as the only hydrocarbon product. The BDE, however, incorporates no deuterium. Thiophene, H[subscript]2S and 2,5-DHT effectively poison the catalyst, inhibiting both BDE hydrogenation and deuterium exchange. Results of this study are used to indicate which thiophene HDS mechanisms most likely occur under these conditions over PbMo[subscript]6.2S[subscript]8.

DOI

https://doi.org/10.31274/rtd-180813-11379

Publisher

Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/

Copyright Owner

John William Benson

Language

en

Proquest ID

AAI9311477

File Format

application/pdf

File Size

179 pages

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