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Title:Cyclopentadienyl ruthenium chalcogenides
Author(s):Amarasekera, Jayantha
Doctoral Committee Chair(s):Rauchfuss, Thomas B.
Department / Program:Chemistry, Inorganic
Discipline:Chemistry, Inorganic
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Chemistry, Inorganic
Abstract:The interaction of transition metal complexes with H$\sb2$S, SH$\sp{-}$ and S$\sbsp{2}{2-}$ ligands is of interest because of their chemical relevance to metal sulfide hydrodesulfurization (HDS) catalysts. Ruthenium sulfur complexes are of interest because of the favorable catalytic properties of RuS$\sb2$ which can act as HDS catalyst as well as an electrocatalyst. The purpose of this thesis was to synthesize, characterize, and study the reactivity of ruthenium compounds containing SH, H$\sb2$S and S$\sbsp{2}{2-}$ ligands.
The electron rich ruthenium hydrosulfide complex CpRu(PPh$\sb3)\sb2$SH (1) was synthesized from CpRu(PPh$\sb3)\sb2$Cl and NaSH. In contrast to the parent chloride, CpRu(PPh$\sb3)\sb2$Cl, 1 undergoes complete monocarbonylation to CpRu(PPh$\sb3$)(CO)(SH). The complex 1 easily undergoes protonation to the H$\sb2$S complex, (CpRu(PPh$\sb3)\sb2$(SH$\sb2)\rbrack\sp{+}$ and alkylation to the thiol complex, (CpRu(PPh$\sb3)\sb2$(RSH)) $\sp{+}$. These complexes can also prepared directly from the highly reactive CpRu(PPh$\sb3)\sb2$OTf (OTf = CF$\sb3$SO$\sb3)$ (2) and H$\sb2$S and RSH respectively. The H$\sb2$S complex is labile, and establishes an equilibrium with hydrogen involving the dihydride complex (CpRu(PPh$\sb3)\sb2$H$\sb2\rbrack\sp{+}$.
Thermolysis of 1 in toluene forms the phosphine free Cp$\sb4$Ru$\sb4$S$\sb4$. The solid state structure of (MeCp)$\sb4$Ru$\sb4$S$\sb4$ consists of a distorted cubane configuration with two Ru-Ru bonds. The electron rich nature of this cubane is reflected in its electrochemistry which reveals two reversible one-electron oxidations.
Complex 1 undergoes a two electron oxidation to $\lbrack$CpRu(PPh$\sb3$)$\sb2\rbrack\sb2$($\mu$-S$\sb2$)$\sp{2+}$ (3) containing a bridging persulfide ligand. The structural and electrochemical properties of 3 suggest that the persulfide ligand serves as a powerful $\pi$-donor to the ruthenium centers. The persulfide complex 3 can be easily reduced to the monocation $\lbrack$CpRu(PPh$\sb3$)$\sb2\rbrack\sb2$($\mu$-S$\sb2$)$\sp{+}$, but the neutral species is too reducing to be isolated. Complex 3 can also be prepared from 2 and elemental sulfur. The reaction of 2 with the sulfur transfer reagent, thiirane does not give 3, instead the thiirane complex $\lbrack$CpRu(PPh$\sb3$)$\sb2$(SC$\sb2$H$\sb4$)$\rbrack\sp{+}$, which was structurally characterized.
The reaction of 1 with sulfur gave two ruthenium polysulfides, cyclo - $\lbrack$CpRu(PPh$\sb3$)$\rbrack\sb2$S$\sb{\rm x}$ (x = 4, 6). The structure of $\lbrack$(MeCp)Ru(PPh$\sb3$)$\rbrack\sb2$S$\sb6$ consists of a bicyclic Ru$\sb2$S$\sb6$ core with short Ru-S bonds. These metal-sulfur multiple bonds induce a transannular bonding, similar to S$\sbsp{8}{2+}$. The structure of ((MeCp)Ru(PPh$\sb3$)) $\sb2$S$\sb4$ suggest a delocalized $\pi$-network, and accordingly it shows rich electrochemistry. These $\lbrack$CpRu(PPh$\sb3$)$\rbrack\sb2$S$\sb{\rm x}$ (x = 4, 6) complexes can also be prepared from the reaction of $\lbrack$Bu$\sb4$N$\rbrack\sb2$S$\sb6$ and 2 or 3.
The selenium analogue of 3 can be prepared from the reaction of CpRu(PPh$\sb3$)$\sb2$OTf and elemental selenium. The similar reaction of (MeCp)Ru(PPh$\sb3$)$\sb2$OTf and selenium gives $\lbrack$(MeCp)Ru(PPh$\sb3$)$\rbrack\sb2$Se$\sbsp{4}{2+}$ as the major product, which contains a Ru$\sb2$Se$\sb4$ core with $\eta\sp1$, $\eta\sp2$ -Se$\sb2$ ligands.
Issue Date:1989
Rights Information:Copyright 1989 Amarasekera, Jayantha
Date Available in IDEALS:2011-05-07
Identifier in Online Catalog:AAI8916209
OCLC Identifier:(UMI)AAI8916209

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