Thermodynamic and Kinetic Studies of the Cis

Thermodynamic and Kinetic Studies of the Cis -...

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Thermodynamic and Kinetic Studies of the Cis-Trans Isomerization of Molydenum- tetracarbonyldiphosphine Dan Mitchell 28 th October 28, 2008 Abstract This experiment compares the stability of cis and trans isomers of Molydenum tetracarbonyl diphosphine and the mechanism by which the ligands exchange. The results were obtained using Infrared Spectroscopy by measuring the absorbance of the change in the virational frequencies for the cis CO stretches and how the absorbance changes over time while being heated. The results show the…………. . Also, the mechanism for the exchange of triethly phosphine and tri-n-butyl phosphine is intramolecuar and the triphenyl phisphine is mostly intramolecular though we cannot discount the possibility for some intramolecular exchange.
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Introduction This experiment measured fluxuation between the cis and trans isomers of Molydenum- tetracarbonyldiphosphine and ligand exchange of how the ligands exchange positions. Di substituted octahedral complexes can exhibit both cis and trans stereochemistries which when heated above the activation energy for isomerisation will form an equilibrium between the two isomers favoring the forward reaction to trans over cis cisMo(CO) 4 L 2 trans-Mo(CO) 4 L 2 Back bonding When bonded to a metal center the CO ligand undergoes back bonding, which can be explained using molecular orbital diagrams. http://qcwizards.chem.warwick.ac.uk/~bailey/Research.htm
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The carbonyl ligand donates 2 electrons from its HOMO orbital to the metal center forming a sigma bond. The metal can then donate electron density into the LUMO pi antibonding
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Thermodynamic and Kinetic Studies of the Cis -...

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