Cleavage reactions of some metal-to-metal quadruple bonds with carbon monoxide.
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| Other Authors: | , , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1984.
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| Subjects: | |
| Online Access: | Link to OAKTrust Copy Link to ProQuest Copy |
| Abstract: | The reactions of the quadruply-bonded dimers Mo(,2)Cl(,4)(PR(,3))(,4) and (n-Bu(,4)N)(,2)Re(,2)Cl(,8) with carbon monoxide are investigated, and the molybdenum complexes are subject to a detailed kinetic study. The reactions of toluene solutions of the complexes Mo(,2)Cl(,4)(PR(,3))(,4) with CO, PR(,3) = PMe(,3), PEt(,3), P-n-Bu(,3), PMe(,2)Ph, and PEt(,2)Ph, were studied in an attempt to elucidate the mechanism of the metal-metal bond cleavage. The products in the case of PR(,3) = PEt(,3) or P-n-Bu(,3) were known to be MoCl(,2)(CO)(,3)(PR(,3))(,2) and the reduced species trans-Mo(CO)(,4)(PR(,3))(,2). The oxidized product from the reaction is phosgene, probably produced by reductive elimination of COCl(,2). The reaction is found to be initiated by dissociation of one phosphine ligand, and the eventual metal-metal bond cleavage requires two molecules of carbon monoxide. An important step in the reaction involves an equilibrium between a loosely-bound dimer and reactive monomers, giving rise to a rate law that is half-order in {complex}. The extent of phosphine dissociation is found to be strongly influenced by steric considerations; thus, the dimers containing PMe(,3) and PMe(,2)Ph are unreactive while those containing PEt(,3), P-n-Bu(,3), or PEt(,2)Ph are cleaved by carbon monoxide at a relatively rapid rate. Reaction conditions of 80-90(DEGREES)C and > 1400 psi CO pressure were required to effect convenient rates of reaction of acetonitrile solutions of (n-Bu(,4)N)(,2)Re(,2)Cl(,8). The detailed mechanism is unknown, but two products of the reaction are characterized by X-ray crystallography: the major product, Re(CO)(,5)Cl, and a minor one, cis-{Re(CH(,3)CN)(,4)(CO)(,2)}(,2){ReCl(,6)}. Additional amounts of the ReCl(,6)('2-) ion were precipitated with excess alkali metal ion. The presence of both Re('I) and Re('IV) species in the product mixture suggests a disproportionation process involving the Re('III) species in the Re(,2)Cl(,8)('2-) ion. |
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| Item Description: | Typescript (photocopy). Vita. "Major subject: Chemistry." |
| Physical Description: | x, 93 leaves : illustrations ; 29 cm |
| Bibliography: | Includes bibliographical references (leaves 89-92). |