Mechanistic Studies of Cyclopentadienyl Ring-Slippage: A TRIR and DFT Study via Photolysis of (η1-C5Cl5)Mn(CO)5

22 August 2018, Version 1
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

Ring slip is among the most widely invoked ligand distortions in organometallic chemistry, yet very few ring slipped geometries have been directly characterized. Here we investigate the ultrafast photochemistry of (η1-C5Cl5)Mn(CO)5 to characterize the “reverse ring-slip” processes that result upon ligand dissociation from this complex in polar and nonpolar solvents. (η1- C5Cl5)Mn(CO)5 readily undergoes dicarbonyl-loss upon photoexcitation across a range of UV-excitation wavelengths, and the fac- ile ejection of a second-CO during the reverse ring-slip process is shown to occur due to a mechanism that relies on the enthalpy released during the reverse ring-slip. This mechanistic paradigm is potentially widespread in organometallic reactions involving changes in ligand hapticity, carrying implications for the expansive range of Cp-ligated organometallic complexes. Experiments in CH2Cl2 solution observe formation of a solvent-coordinated product upon coordination of CH2Cl2 to the monocarbonyl-loss spe- cies. An energetic barrier to solvent coordination is present due to the need for rearrangement of the ring geometry from a three- center M-C-Cl coordination to η1 coordination to accommodate the incoming solvent molecule. Density functional theory calculations are used to investigate the structures of the experimentally observed intermediates, as well as to explore the relevance of these experiments to analogous complexes containing the more commonly encountered Cp (C5H5) and Cp* (C5Me5) cyclopentadienyl ligands.

Keywords

Time-resolved infrared spectroscopy
ultrafast spectroscopy
Organometallic photochemistry
Density Functional Theory

Comments

Comments are not moderated before they are posted, but they can be removed by the site moderators if they are found to be in contravention of our Commenting Policy [opens in a new tab] - please read this policy before you post. Comments should be used for scholarly discussion of the content in question. You can find more information about how to use the commenting feature here [opens in a new tab] .
This site is protected by reCAPTCHA and the Google Privacy Policy [opens in a new tab] and Terms of Service [opens in a new tab] apply.