Synthesis and Electronic Structure of Reduced Bis(imino)pyridine Manganese Compounds

Abstract

Abstract The synthesis and electronic structure of reduced aryl‐substituted bis(imino)pyridine manganese compounds have been explored. Stirring a THF slurry of [( iPr PDI)MnCl 2 ] { iPr PDI = 2,6‐(2,6‐ i Pr 2 –C 6 H 3 N=CMe) 2 C 5 H 3 N} with excess Na and catalytic (0.5 mol‐%) naphthalene furnished the bis(THF) compound [( iPr PDI)Mn(THF) 2 ]. Performing the reduction with excess Na(Hg) in toluene furnished the bis(chelate) manganese compound [( iPr PDI) 2 Mn]. For both compounds, a combination of EPR spectroscopy, magnetic measurements and metrical parameters determined from X‐ray diffraction established high‐spin Mn II compounds with reduced, redox‐active bis(imino)pyridine ligands. Substitution of the THF ligands with carbon monoxide yielded [( iPr PDI)Mn(CO) 2 ], a low‐spin Mn I , d 6 compound with an experimentally observed bis(imino)pyridine‐centred radical. Oxidation and reduction of this compound furnished [( iPr PDI)Mn(CO) 3 ] + and [( iPr PDI)Mn(CO) 2 ] – , respectively, and provided a series of three manganese carbonyl compounds over three oxidation states. Elucidation of the electronic structure of these compounds established that oxidation events within the series are ligand‐ rather than manganese‐based, most likely a result of the stable low‐spin Mn I , d 6 electron configuration imparted by the strong‐field carbonyl ligands.