X-RAY-ABSORPTION STUDIES OF THE D-ORBITAL OCCUPANCIES OF SELECTED 4D/5D TRANSITION-METALS COMPOUNDED WITH GROUP-III/IV LIGANDS

X-ray-absorption spectroscopy (XAS) is used to explore the systematic variations in the 4d/5d transition-metal {T = Au, Pt, Ir, Re, Pd, Ag} d-orbital occupancy in binary T-X compounds {X = Al, Ga, In, Si, Ge, Sn}. Specifically, the strength of the white line (WL) feature at the T-L2,3 edges is used to quantify the changes in the d-orbital occupancy induced by T-X bond formation. Systematic chemical trends in bonding-induced d-orbital-occupancy changes, evidenced by the data, are discussed. A charge-transfer scale (C scale) is developed to approximately summarize the number of T-d holes created in all of the T1-xXx compounds studied. Comparison with the electronegativity scale emphasizes that, although the C scale deals with a more restricted type of charge transfer, it provides insight into the T-X bonding that is not contained in the traditional scale.