Formation of Carbon-Carbon Triply Bonded Molecules from Two Free Carbyne Radicals via a Conical Intersection.
The recent proposal (Bogoslavsky, B.; Levy, O.; Kotlyar, A.; Salem, M.; Gelman, F.; Bino, A. Angew. Chem., Int. Ed.2012, 51, 90-94) that metallo-alkylidyne complexes decompose in aqueous solution and give rise to free carbynes, which couple to yield acetylenes, is examined here theoretically. On the basis of the known marker reactions of carbynes in the doublet and quartet state, it is concluded that most of the reactivity patterns observed in the Bino experiment arose from quartet carbynes. Indeed, theory shows that quartet carbynes can be funneled to acetylene via a conical intersection. Moreover, many of the minor products are also identified as markers of the quartet carbynes. Carbynes formation in their doublet state is a minor channel that branches from the conical intersection and leads to the formation of dienes and olefins in the Bino experiment. Thus, we show that conical intersections are important also in thermally initiated reactions. Coupled to the experimental approach, the study opens a window to studies of carbynes under mild conditions.
†Institute of Chemistry and ‡The Lise Meitner-Minerva Center for Computational Quantum Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 91904 Jerusalem, Israel.
David
D
Danovich
†Institute of Chemistry and ‡The Lise Meitner-Minerva Center for Computational Quantum Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 91904 Jerusalem, Israel.
Avi
A
Bino
†Institute of Chemistry and ‡The Lise Meitner-Minerva Center for Computational Quantum Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 91904 Jerusalem, Israel.
Sason
S
Shaik
CASSCF; carbyne coupling; molybdenum ethylidyne complexes; multireference CI; spin allowed process; surface crossing