T-Space at The University of Toronto Libraries >
School of Graduate Studies - Theses >
Please use this identifier to cite or link to this item:
|Title: ||Ligand-based Reactions of Metal Bis- and Trisdithiolenes: Fresh Insights into Old Reactions and New Frontiers|
|Authors: ||Harrison, Daniel|
|Advisor: ||Fekl, Ulrich|
|Issue Date: ||21-Apr-2010|
|Abstract: ||Metal dithiolenes [M(S2C2R2)n] have been studied for decades because of their interesting chemical and spectroscopic properties, which are related to the unusual electronic properties of the dithiolene ligand. The ligand-based reactivity of metal bisdithiolenes [M(S2C2R2)2] toward alkenes has been proposed for use in alkene purification schemes. According to the proposal, compounds Ni(S2C2R2)2 (R=CF3,CN) react with simple alkenes to form stable S,S-interligand adducts and the alkene can be released from the adduct by reduction. We showed that Ni(S2C2(CF3)2)2 reacts with ethylene and 1-hexene to form, preferentially, S,S-intraligand adducts, which rapidly decompose to inactive metal-containing materials and dihydrodithiins. However, the product selectivity can be significantly modified so that stable S,S-interligand adducts are obtained as dominant products by adding [Ni(S2C2(CF3)2)2]- to Ni(S2C2(CF3)2)2/alkene reaction mixtures. Mechanistic implications are discussed.
Next, the reactions of Pt(S2C2(CF3)2)2 with 2,3-dimethyl-1,3-butadiene are addressed. Prior to our report, only symmetry-allowed S,S-interligand adducts had been observed as products in the reactions between conjugated dienes and metal bisdithiolenes. We discovered a novel mode of diene binding, where two dienes bind to one dithiolene ligand of Pt(S2C2(CF3)2)2, in an C,S-intraligand fashion, forming a new chiral bisthioether ligand.
From bisdithiolenes, the focus shifts to new mixed-ligand molybdenum trisdithiolenes [Mo(S2C2(CF3)2)2(S2C6H4) and Mo(S2C6H4)2(S2C2(CF3)2)]. These complexes rapidly and cleanly bind ethylene, in an S,S-intraligand fashion, as predicted by MO arguments. The resulting intraligand adducts are sufficiently stable to be characterized, in contrast to the nickel bisdithiolene case. The metal-chelated dihydrobenzodithiin, formed upon ethylene addition, can be substituted with a variety of donor ligands, allowing access to new types of molybdenum dithiolenes. We have recently extended these studies to catalytic reactions: Mo(S2C2(CF3)2)2(S2C6H4) was used as a catalyst to form dihydrobenzodithiins from (S2C6H4)2 and a variety of alkenes, in the first example of dithiolene-based reactivity being exploited for carbon-heteroatom bond-forming catalysis.
Finally, the synthesis, characterization and redox reactivity of a new Fe2Ni bis-double-decker complex is described, demonstrating for the first time a sandwich complex of a metal bisdithiolene with both NiS2C2 rings in an η5 π-donating mode. For the radical cation, experimental and computation evidence indicates that the lone electron is delocalized over the entire molecule.|
|Appears in Collections:||Doctoral|
Department of Chemistry - Doctoral theses
This item is licensed under a Creative Commons License
Items in T-Space are protected by copyright, with all rights reserved, unless otherwise indicated.