The oxidation states, syntheses and properties of diruthenium tetracarboxylates /
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| Other Authors: | , , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1989.
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| Subjects: | |
| Online Access: | Link to OAKTrust copy |
| Abstract: | The question of the existence of compounds of the type Ru₂ (O₂CR)₄²⁺, which would have Ru₂⁶⁺ cores, has been examined. Systematic studies have led unambiguously to the conclusion that there is no evidence for the existence of Ru₂ (O₂CR)₄²⁺ type complexes. First, one of their homologues, Ru₂ (O₂CC₂H₅)₄²⁺ (superscript n), was prepared using the methods given for the reported Ru₂(O₂CCH₃)₄²⁺ compound; an X-ray crystallographic study showed that it was Ru₂(O₂CC₂H₅)₄⁺. Then, reinvestigations of the reported Ru₂ (O₂CR)₄²⁺ (R = Me and CF₃) compounds indicated that they were actually Ru₂ (O₂CR)₄⁺ type species. Ru₂(O₂CCH₃)₄Cl-which has a Ru₂⁵⁺ metal-metal center--reacts with L-HO₂CCH(OH)C₆H₅ (Hmand) to form disproportionation products, Ru₂(mand)₄(H₂O)₂ and [Ru₃(O(mand)₆(H₂O)₃]⁺. The former product was characterized by x-ray crystallography and magnetic measurements. This is the first time a Ru₂(O₂CR)₄ compound has been made directly, on a preparative scale, from a Ru₂(O₂CR)₄⁺ compound. Our magnetic studies of Ru₂(O₂CPh)₄ and Ru₂(O₂CCH₃)₄ have led to the conclusion that Ru₂(O₂CR)₄ compounds have a (delta symbol)²π⁴(delta symbol)²(delta symbol)*²π*² electronic configuration. Their magnetic moments in the temperature range 6-298 K can be well fitted by postulating that a ³A₂(subscript g) state, derived from a (delta symbol)²π⁴(delta symbol)²(delta symbol)*²π*² configuration, undergoes a second order splitting to give a non-magnetic ground state (S(subscript z)= 0) and a state with S(subscript z)= (plus or minus sign) 1. Our conclusion is fully supported by ESR measurements and structural relationships between the Ru₂(O₂CR)₄⁺, Ru₂(O₂CR)₄, and Ru₂(RNNNR)₄ compounds. In studies of the absorption spectra of Ru₂(O₂CCH₃)₄ (MeOH) ₂ at 6 K, no (delta symbol)- (delta symbol)* or π* -(delta symbol)* transition was observed. This is consistent with the assignment of the electronic configuration as (delta symbol)²π⁴(delta symbol)²(delta symbol)*²π*² According to this configuration and perturbation theory, the CD spectrum of Ru₂[ L-O₂CCH(OH)C₆H₅]₄(H₂O)₂ was interpreted by using the absolute conformation from the crystal structure of Ru₂[ L-O₂CCH(OH)C₆H₅]₄(H₂O)₂. The polarized spectra of tetragonal crystals of Mo₂(O₂CCPh₃)₄3CH₂Cl₂at 6 K were studied. Well-resolved z-polarization or xy-polarization spectra were observed in the direction parallel or perpendicular to the molecular z axis. The spectra have been interpreted based on the assignment of the electronic origin to the (delta symbol) - (delta symbol)* transition. Hot band studies verified the assignments of the (delta symbol)² -(delta symbol)*and the vibronic transitions. The (delta symbol) - (delta symbol)*transition energy in this molecule without axial coordination is essentially the same as that of other dimolybdenum tetracarboxylates with axial coordination. |
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| Item Description: | Typescript (photocopy). Vita. "Major subject: Chemistry." |
| Physical Description: | xi, 116 leaves : illustrations ; 29 cm |
| Bibliography: | Includes bibliographical references. |