Synthesis and characterization of new multiply bonded binuclear complexes with polydentate phosphines /
| Main Author: | |
|---|---|
| Other Authors: | , , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1993.
|
| Subjects: | |
| Online Access: | ProQuest, Abstract Link to OAKTrust copy |
| Abstract: | Several series of compounds of the types Mo2X4L4 and M2(μ-Y)2X4L4 (M = Mo, Re) with polydentate phosphine ligands will be reported. In the meso and racemic Mo2X4(tetraphos-1) (X = Cl, Br) series, two new types of geometrical isomers, namely 1,2,5,7/1,2,6,8 and 1,2,6,7/1,2,5,8 enantiomeric pairs, of Mo2X4L4 complexes were obtained. While the two central phosphorus donor atoms coordinate to different Mo centers in the complexes of the racemic ligand, they coordinate to the same Mo atom in the complex of the meso ligand, thus giving the bischelating/single-bridging coordination mode in the former and the chelating/double-bridging mode in the latter. The average Mo[4]Mo bond distances, 2.154 A and 2.190 A for racemic and meso diastereomers, respectively, are different 0 by 0.037 A, but they both fall within the range of the distances established for Mo-Mo quadruple bonds. The average of the four smallest torsional angles is 18.8° or 30.0° for the racemic or meso diastereomers, respectively. Another quadruply bonded compound, rac-Mo[4]MoCl4(η^3-tetraphos-2 )(PEt3), displays much shorter Mo[4]Mo bond distance (2.132(3) A) and smaller torsional angles with an average of 11.7°. It can be assigned as enantiomeric 1,2,5,7/1,2,6,8 type of isomer. The 31P {1H} NMR spectrum of this complex displays five multiplets corresponding to five magnetically different phosphorus nuclei, and it affords a unique system to study 31P - 31P coupling, through the connecting chain between phosphorus nuclei and/or through the metal-metal quadruple bond, in quadruply bonded dinuclear compounds. With use of the structural data for all the compounds with tetraphos-1 and tetraphos-'2 ligands, the correlation between Mo[4]Mo bond distances and cos2x has been shown to be an inverse linear function with a correlation coefficient of 0.9672. Three new edge-sharing bioctahedral compounds, Mo2Cl6(eLTTP), Mo2CI4- [Et2PCH2CH2P(Ph)CH2P(Ph)]2, and Re2Cl6(tetraphos-1 ) will also be presented. Among them are two types of geometrical isomers, namely 1,2.7,8 and 1,2,5,6 types, the first of which has not previously been reported in the literature. Several interesting features in the synthesis and structure of these compounds will be discussed. |
|---|---|
| Item Description: | Vita. "Major subject: Chemistry." |
| Physical Description: | xiv, 151 leaves : illustrations ; 28 cm |
| Bibliography: | Includes bibliographical references. |