Experimental verification of diverging mechanisms in the binding of ether, thioether, and sulfone ligands to a dirhodium tetracarboxylate.
Complexation of the oxygen atom in 2-butylphenylethers and sulfur in 2-butylphenylthioethers to a rhodium atom in dirhodium tetracarboxylate Rh((II)) (2)[(R)-(+)-MTPA](4) is compared. Oxygen atoms complex via electrostatic attraction exclusively leading to an increase in alpha effects on C-2 complexation shifts in the sequence OCH(3) > F > Br > NO(2). However, that trend is opposite in thioethers. This can be rationalized by an additional highest occupied molecular orbital (HOMO)-LUMO interaction and the response of this interaction upon complex formation shifts. Thereby, an experimental evidence was found for the existence of the HOMO-LUMO binding mechanism which has been proposed previously based on theoretical considerations and indirect spectroscopic evidence. Sulfones hardly bind to Rh((II)) (2)[(R)-(+)-MTPA](4). Diastereomeric dispersion effects at (13)C and (1)H signals can be observed for all compounds indicating that enantiodifferentiation is easy in all classes of functionalities.
Mattiza
Jens T
JT
Leibniz University Hannover, Institute of Organic Chemistry, Schneiderberg 1B, D-30167 Hannover, Germany.
Meyer
Vera J
VJ
Duddeck
Helmut
H
D001665:Binding Sites; D003198:Computer Simulation; D004987:Ethers / Q000737:chemistry*; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy; D009942:Organometallic Compounds / Q000737:chemistry*; D013440:Sulfides / Q000737:chemistry*; D013450:Sulfones / Q000737:chemistry*
D004987:Ethers; D008024:Ligands; D009942:Organometallic Compounds; D013440:Sulfides; D013450:Sulfones; C519986:dirhodium tetracarboxylate