C-13 NMR-STUDIES OF OXO-CENTERED TRINUCLEAR CHROMIUM(III) COMPLEXES OF THE GENERAL FORMULA [CR3O(O2CR)6(L)3]+ (R=ME, PH, L=H2O,PY)

C-13 NMR resonances of a series of oxo-centered trinuclear chromium co mplexes have been observed and assigned. A pi-delocalization mechanism dominates where ligands contain aromatic substituents or bridging car boxylate functionalities, consistent with the presence of a metal cent er where to first approximation unpaired electrons reside solely in t2 g orbitals. A contrast is made between the delocalization mechanism in these complexes and those of their isostructural Mn and Fe analogues.