Transition-metal (Au, Pt, Ir, Re) bonding to Al,Si,Ge: X-ray-absorption studies

We report transition-metal (T) L₂ and L₃ near-edge x-ray-absorption spectroscopy measurements on more than a score of T-X compounds with T=Au, Pt, Ir, and Re and X=Al, Si, and Ge. We correlate the strength of the (2p{→}5d)-related ``white line'' feature at these edges to the degree of chemical-bonding-induced 5d-orbital charge transfer in these materials. Similar bonding trends are shown to be present in 1:2:2 compounds involving these T and X elements. Finally, the bonding-induced charge-transfer effects in such T-X compounds are discussed along with the Pauling electronegativity scale. [L. Pauling, The Nature of the Chemical Bond (Cornell University Press, New York, 1960), p. 93.]