Article,

The nature of reduced and excited states of p-electron-deficient complexes between tricarbonylhalorhenium and diimine ligands

, and .
Inorganic Chemistry, 29 (16): 2909--2914 (1990)
DOI: 10.1021/ic00341a010

Abstract

(m-L)Re(CO)3X2 (X = Cl, Br) with the bridging bis-chelate ligands L = 2,2'-bipyrimidine, 2,5-bis(2-pyridyl)pyrazine, 3,6-bis(2-pyridyl)-1,2,4,5-tetrazine, and 2,2'-azopyridine were synthesized. Coordination of 2 Re(CO)3X fragments causes a pronounced lowering of the ligand p* LUMOs, the dinuclear 2,2'-azopyridine complexes being reduced most easily at $\sim$+0.45 V vs. SCE. The resulting anion-radical complexes were characterized by ESR and, in part, by their visible absorption and CO vibrational spectra. ESR data data rule out a Re(0) or Re(0)/Re(I) formulation for the singly reduced monomers and dimers and show the spectral effect of X- loss for the labile mononuclear (bpy.bul.-)Re(CO)3Br (bpy = 2,2'-bipyridine). The well-sepd. long wavelength absorption bands from metal-ligand charge-transfer transitions of the most p-electron-deficient neutral complexes display a distinct structure. A comparison is made between the electronic structures of a-diimine complexes with W(CO)4, Re(CO)3X, and Ru(bpy)22+ fragments. on SciFinder(R)

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