In one reaction, a pi-allyl complex containing this element undergoes a Walden inversion in an oxidative addition step that allows a nucleophile to substitute an alkene. Barium sulfate poisons this element in a reduction reaction that produces (15[1])aldehydes. Reducing an acetate with phosphine activates this element in one reaction, and this element is regenerated by copper chloride to catalyze the oxidation of ethylene into acetaldehyde (15[1])during the (*) Wacker process. (10[1])This element catalyzes a reaction that forms carbon-carbon bonds with an organoboron species and a halide. Heck, Negishi, and Suzuki won the 2010 (10[1])Nobel (10[2])Prize in Chemistry for work on cross-coupling (-5[1])reactions catalyzed by this metal. For 10 points, name this expensive platinum-group metal found in Lindlar’s catalyst, with symbol Pd. ■END■ (10[3])