text: Vaska published ca. eighty journal articles on the coordination chemistry of transition metals, homogeneous catalysis, and both organometallic and bioinorganic chemistry. His years at Mellon were especially productive. With J.W. Di Luzio in 1962 he first described the iridium compound which became known as Vaskas complex, trans-IrCl(CO)[P(CH)]  Working with a series of coworkers, he demonstrated that this iridium(I) complex undergoes a variety of reactions with small molecules. For example, it oxidatively adds H to give a dihydride. He subsequently discovered that his complex reversibly bound O, which was then a startling achievement. He discovered the main reactions of oxidative addition, a process that is central to homogeneous catalysis in organometallic chemistry.  He demonstrated a number of important substituent effects on the oxidative addition, such as the greater reactivity of Ir(I) vs. Rh(I) and the stabilization of oxidative adducts by iodide vs.' chloride.