Synthesis and reactivity of electroactive carbon sulfide ligands and studies on modifications of nucleic acids.

摘要

The beginning of the thesis focuses on the synthesis and interconversion of two anionic carbon sulfide ligands, namely C₂S₄ 2− (tetrathiooxalate, TTO) and C₄S₆ 2−. The synthesis of TTO was accomplished by using a modified electrochemical apparatus and a new method for purification. A reliable route to analytically pure C₄S₆2− was accomplished by a two-step synthesis involving oxidation of TTO. Electrochemical studies of both free ligands demonstrate similarities between the two species.; The reaction of TTO and C₄S₆2− with metal carbonyls was investigated. Some limitations of TTO as a ligand were discovered. Reaction of W(S₂C₂Ph₂) ₂(CO)₂ with TTO gave an electrochemically active ditungsten species, and reaction with C₄S₆2− showed degradation of C₄S₆2− into C₂S₄n−.; Synthesis of TTO complexes of transition metals was accomplished by using (Cp*MCl₂)₂, M = Rh and Ir, to give Cp*₂M ₂Cl₂(μ-C₂S₄) complexes. The non-innocent redox nature of C₂S₄2− within these metal complexes was monitored structurally; specifically, the reduction of M₂C₂S₄2− to M₂ C₂S₄4− was observed and characterized. This was the first system to show the conversion of a TTO-complex to an ethylenetetrathiolate complex. The analogous complex Cp*₂Rh₂Cl₂(μ-C ₄S₆) was also synthesized.; Cp*₂Rh₂(μ-C₂S₄) was used as a building block to create larger ensembles with new bonding modes of C ₂S₄. The electrochemical behavior of Cp*₂Rh ₂(μ-C₂S₄) led to the discovery of a tetrarhodium species, [Cp*₄Rh₄(C₂S₄)₂ ]2+. The ability of the bridging C₂S ₄4− to donate electrons was probed by reaction of Cp*₂Rh₂(μ-C₂S₄) with [Cp*Ru(NCCH ₃)₃]+ and [Cp*Rh(NCCH₃)₃] 2+ to give [Cp*₃Rh₂Ru(C₂S₄)] + and [Cp*₆Rh₆(C₂S₄) ₂]4+, respectively.; Finally, a separate study into the selective selenization of nucleic acid oligonucleotides was pursued. By using the soluble Se-transfer agent (i-PrC₅H₄)₂TiSe₅ in a new method with solid-phase phosphoramidite oligonucleotide synthesis, a mono-, di-, tri-, and tridecanucleotide of DNA with one phosphoroselenoate modification as well as a dinucleotide of RNA modified with one phosphoroselenoate were synthesized. The utility of phosphate backbone modifications in nucleic acid chemistry has been pursued for phosphorothioates and may now be studied for selenium analogues.