Ru(II) Complexes with Protic- and Anionic-Naked-NHC Ligands for Cooperative Activation of Small Molecules

Protic- or anionic-NHCs with a classical-NHC in a single [Ru(CNC)(PPh3)2Cl]Cl pincer complex: direct comparison of structure & electronic properties and heterolytic H2 splitting

Herein, we report the first set of pincer complexes 1 and 2 with the general formula [Ru(CNC)(PPh3)2Cl]Cl having a protic- and classical-NHC in the same molecule and nearly identical environments. Deprotonation of the protic-NHC complex 2 with one equivalent of base leads to the formation of anionic-NHC complex 2'. These complexes allow a direct comparison of protic- and anionic-NHCs with the classical-NHC ligand. A comparison of the molecular structure indicated that the metal carbene bond length trend is anionic-NHC > protic-NHC > classical-NHC. The electrochemical investigation revealed the electron donation tendency is classical-NHC > protic-NHC and anionic-NHC > protic-NHC. Cooperation between the metal and the ligand is indicated by the reaction of 2' with H2 gas at 1 atm pressure and 110 °C to give the Ru-hydride complex 3.

Ru-Catalyzed and Selenium-Directed Selective Formation of ortho- and Dialkenylated Selanes, Mixed Organoselenoethers, and Isoselenochromenes

Herein, the Ru-catalyzed chemo- and regioselective formation of four novel organoselenium compounds is established. Mono- and dialkenylated selanes were formed by the Se-directed o-C-H activation of benzyl(phenyl)selanes with alkynes. Unprecedented debenzylative/dearylative hydroselenations of alkynes were performed by slightly varying the amount of catalyst and temperature. Catalyst-driven direct formation of novel isoselenochromenes is also recorded. Altogether, 45 new organoseleno compounds were synthesized in good amounts with varieties of alkynes and selanes. This is the first report of its kind to deal with the synthesis of novel, challenging, and unusual organoseleno compounds in one reaction.