Strong metal-to-ligand charge transfer bands observed in Ni K- and L-edge XANES of planar Ni complexes

Polarized Ni K-edge and L-edge XANES spectra were measured for some planar Ni complexes with low-spin 3d(8) configuration, K2Ni(CN)(4). H2O Ni(Hdmg)(2 ) (Hdmg: 2,3-butanedione dioximato) and [(n-C4H9)(4)N](2)[Ni(mnt)(2)] (mnt: 1,2-dicyanovinylene-1,2-dithiolato). In all the spectra, strong satellite bands are found in addition to the lowest Ni Is, 2p-->3d* atomic lines. The se an mostly assigned to the metal-to-ligand charge transfer (MLCT) transit ions to unoccupied states with dominant ligand pi* components, in good agre ement with ab initio molecular orbital predictions. The low-lying ligand pi * orbital is essential in interpreting the metal K-edge and L-edge XANES of 3d transition metal compounds.