Density functional studies on the Pauson-Khand reaction

The Pauson-Khand reaction represents a one-step Co-2(CO)(8)-catalyzed synth esis of cyclopentenone through [2 + 2 + 1] assembly of one molecule each of alkene, alkyne, and carbon monoxide. Density functional studies (B3LYP/631 LAN) on the reaction pathway of the Pauson-Khand (PK) reaction reported her e for the first time provides-valuable information on the structures and en ergetics of various intermediates and transition states. The PK reaction co nsists of olefin insertion, CO insertion, and reductive elimination steps. The olefin insertion step was found to be an irreversible step that determi nes the stereo- and regiochemistry of the overall reaction. The following s teps are low activation energy processes and reversible. The bond-forming e vents occur only on one of the two metal atoms, while the second metal atom not only acts as an anchor that fixes the metal cluster to the organic sub strate but also exerts electronic influences on the reaction at the first a tom.