Abstract
Mononuclear transition metal carbonyl complexes (h1-TCNE)Cr(CO)2(C6Me6) and (h1-L)Mn(CO)2(h5-C5MenH5-n) with s (end-on) coordinated ligands L = TCNE, 2,5-dimethyl-7,8-dicyano-p-quinone diimine, TCNQ and the complexes (h2-TCNE or h2-TCNQ)M(CO)5 (M = Cr W) and (h2-fumarodinitrile)Mn(CO)2(h5-C5Me5) with a p (side-on) coordinated polycyano ligand have been studied by cyclic voltammetry (TCNE complexes) and electron absorption spectroscopy. Redn. potentials of the complexes were found above and below the values of free TCNE, indicating varying degrees of metal-to-ligand electron transfer in the ground state. This electron transfer is confirmed by vibrational spectroscopy and UV/visible/near-IR spectral response on C5R5 ligand modification. Solvent-induced dissocn. into the simultaneously ESR detectable paramagnetic metal fragment and the anion radical of the ligand was obsd. in one instance. Intense charge-transfer (MLCT/LMCT) transitions of the complexes occur in the visible and near-IR part of the spectrum. The p-coordinated complexes were found to exhibit a very different spectral response towards solvent variation than the s-bonded derivs. on SciFinder(R)
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