Event Type
Research Presentation
Academic Department
Chemistry
Start Date
25-4-2022 12:00 AM
End Date
25-4-2022 12:00 AM
Description
When M2L10 complexes containing two rhenium(III) atoms in a quadruple bond react with an excess of a bridging diphosphine ligand Ph2PCH2PPh2, the bond order decreases and the rhenium is reduced to rhenium(II). The diphosphine ligands can adopt a cis-cis, cistrans, or trans-trans configuration. NMR spectra of compounds that adopt the ciscis arrangement show unusually large downfield shifts for one of the bridgehead methylene hydrogens (P-CH2-P). To understand the unusual chemical shift, the hydrogens first have to be assigned. The strategy for making these assignments has been to try to make compounds where one of the hydrogens has been replaced with another group (e.g., CH3 or CN). All efforts to make cis-cis-type compounds containing Ph2PCH(CH3)PPh2 (dppmMe) or Ph2PCH(CN)PPh2 (dppmCN) have been unsuccessful. However, reactions of rhenium-containing starting materials with these derivatized ligands have produced compounds with many unforeseen properties, including unexpected solubilities and colors. These reactions may also have produced a sample with the characteristics of a trans configuration of ligands.
Dirhenium Compounds Containing the Diphosphine Ligands Ph2PCH2PPh2, Ph2PCH(CN)PPh2, or Ph2PCH(CH3)PPh2: a Comparative Study
When M2L10 complexes containing two rhenium(III) atoms in a quadruple bond react with an excess of a bridging diphosphine ligand Ph2PCH2PPh2, the bond order decreases and the rhenium is reduced to rhenium(II). The diphosphine ligands can adopt a cis-cis, cistrans, or trans-trans configuration. NMR spectra of compounds that adopt the ciscis arrangement show unusually large downfield shifts for one of the bridgehead methylene hydrogens (P-CH2-P). To understand the unusual chemical shift, the hydrogens first have to be assigned. The strategy for making these assignments has been to try to make compounds where one of the hydrogens has been replaced with another group (e.g., CH3 or CN). All efforts to make cis-cis-type compounds containing Ph2PCH(CH3)PPh2 (dppmMe) or Ph2PCH(CN)PPh2 (dppmCN) have been unsuccessful. However, reactions of rhenium-containing starting materials with these derivatized ligands have produced compounds with many unforeseen properties, including unexpected solubilities and colors. These reactions may also have produced a sample with the characteristics of a trans configuration of ligands.
Comments
Under the direction of Dr. Daniel R. Derringer.