Supramolecular assembly and transfer hydrogenation catalysis with ruthenium(II) complexes of 2,6-di(1H-pyrazol-3-yl)pyridine derivatives

Abstract

)]) were screened for activity towards transfer hydrogenation of acetophenone in refluxing 2-propanol. The chloride salt catalysts are active but show a significant induction period, which may imply decomposition of the complexes during the reaction. However the activity of the PF 6 salt is much higher, which shows that competition between chloride and substrate for the metal center is a significant factor in catalysis by these compounds.4

Synthesis and Structures of NCN Pincer-Type Ruthenium and Iridium Complexes Bearing Protic Pyrazole Arms

“…Pincer-type ruthenium complexes bearing the protic NNN-LH 2 and its derivative are known to catalyze transfer hydrogenation of ketones with 2-propanol . To assess the impact of the central aryl group in the NCN-LH 2 pincer ligand on the catalysis, we compared the catalytic performance of the NCN pincer-type complexes 2 and the NNN analogue.…”

“…The tunable nature of the steric and electronic parameters for these purposes is one of the distinctive traits of the pincer-type ligands. Protic pyrazole is an attractive pendant group in the pincer-type ligand to modulate the coordination sphere through hydrogen bonding and proton transfer. , During our extensive study on metal–ligand cooperation in the coordination chemistry of the protic N-heterocycles, , we have recently been interested in the NNN pincer-type 2,6-bis­(pyrazol-3-yl)­pyridine (NNN-LH 2 ; Chart ) complexes furnished with two protic pyrazole arms − and investigated their proton-donating ability and metal–ligand cooperation. Particularly remarkable is the disproportionation of hydrazine into dinitrogen and ammonia catalyzed by a protic pincer-type iron complex, wherein electron transfer between the complex and the substrate molecule is associated with the proton transfer .…”

Protic NNN and NCN Pincer‐Type Ruthenium Complexes Featuring (Trifluoromethyl)pyrazole Arms: Synthesis and Application to Catalytic Hydrogen Evolution from Formic Acid

“…We and others have already demonstrated that the treatment of [RuCl 2 (PPh 3 ) 3 ] with LH 2 ‐type ligands yields the corresponding NNN pincer‐type bis(pyrazole) ruthenium(II) complexes [RuCl(LH 2 )(PPh 3 ) 2 ]Cl. In contrast, the reaction with CF 3 ‐LH 2 proved to give a complicated mixture containing a small amount of the deprotonated complex [RuCl(CF 3 ‐LH)(PPh 3 ) 2 ] ( 1 a ).…”

NNN Pincer‐functionalized Porous Organic Polymer Supported Ru(III) as a Heterogeneous Catalyst for Levulinic Acid Hydrogenation to γ‐Valerolactone

“…[48][49][50][51][52][53][54] Ru complexes of 3-bpp ligand derivatives have demonstrated high catalytic efficiencies for ketone-to-alcohol transfer hydrogenation, a key step in the hydrogenation of LA to GVL. [55][56][57] A heterogeneous Ru molecular catalyst with 3-bpp-based POPs, combining the function of the Ru 3-bpp catalyst system with the advantage of a solid support, would be of interest for both scientific and industrial applications.…”

“…The electronic and steric properties of 3‐bpp ligands are tunable, and multiple transition metal‐based 3‐bpp complexes have been reported for diverse catalytic applications [48–54] . Ru complexes of 3‐bpp ligand derivatives have demonstrated high catalytic efficiencies for ketone‐to‐alcohol transfer hydrogenation, a key step in the hydrogenation of LA to GVL [55–57] . A heterogeneous Ru molecular catalyst with 3‐bpp‐based POPs, combining the function of the Ru 3‐bpp catalyst system with the advantage of a solid support, would be of interest for both scientific and industrial applications.…”