A mechanistic study of the hydroselenation of alkynes catalyzed by Pd (PPh3) 4 and Pt (PPh3) 4 has shown that the palladium complex gives products of both Se H and Se Se bond addition to the triple bond of alkynes, while the platinum complex selectively catalyzes Se H bond addition. The key intermediate of PhSeH addition to the metal center, namely Pt (H)(SePh)(PPh3) 2, was detected by 1H-NMR spectroscopy. The analogous palladium ...