Cyclopentadienyl ruthenium chalcogenides

Amarasekera, Jayantha

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Description

Title

Cyclopentadienyl ruthenium chalcogenides

Author(s)

Amarasekera, Jayantha

Issue Date

1989

Doctoral Committee Chair(s)

Rauchfuss, Thomas B.

Department of Study

Chemistry, Inorganic

Discipline

Chemistry, Inorganic

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

Chemistry, Inorganic

Language

eng

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.

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Copyright 1989 Amarasekera, Jayantha

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