Ruthenium Complexes Bearing N–H Acidic Pyrazole Ligands

Abstract

Chelate ligands containing at least one pyrazole group were treated with RuCl2(PPh3)3, RuHCl(CO)(PPh3)3 and RuH2(CO)(PPh3)3 to form ruthenium complexes bearing protic N–H groups in close proximity to the catalytically active ruthenium centre. In the case of the hydridoruthenium complex RuHCl(CO)(PPh3)3 the resulting complexes also contain abasic hydrido ligand. The combination of acidic and basic hydrogen species in one molecule and the arising two‐site reactivity was thoroughly investigated spectroscopically and by DFT calculations. Catalytic tests on the hydrogenation and transfer hydrogenation of acetophenone showed a general activity of these systems.

Iron(ii) complexes of 2,6-di(1H-pyrazol-3-yl)-pyridine derivatives with hydrogen bonding and sterically bulky substituents

“…8 While [Fe(3-bpp) 2 ] 2+ itself has been well studied, the synthesis of substituted analogues of 3-bpp is poorly developed. A number of 5,5'-disubstituted 3-bpp derivatives (Scheme 1, R = R' ≠ H) have been reported in recent years, 9 and studied for catalysis and small molecule activation, 14 as components in dye-sensitised solar cells, 15 and in self-assembly systems. 16 However, few of these have thus far been applied to spincrossover chemistry, 11,17 which is surprising given the unusual chemistry of 2 ] 2+ itself.…”

“…9 The method depends on the slow Claisen condensation between pinacolone and dimethyl pyridine-2,6-dicarboxylate, and so may not be applicable for all substituent combinations. However, it could be used to make other 5,5'-disubstituted 3-bpp derivatives containing just one tertbutyl group (Scheme 1; R = tBu, R' = any substituent), which could be of value for catalysis 14 and photosensitiser applications 15 as well as for SCO.…”

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

“…Asian J. 2018,13,[73][74][75][76][77][78][79][80] www.chemasianj.org complete conversion to the conjugateda cid-base pair, 1a and [RuCl(tBu-LH 2 )(PPh 3 ) 2 ]OTf (2b), took place in the 1 HNMR criteria. Formation of 1a in this reactiona lso establishes the reversibility of the protonation of 1a.M eanwhile, am ixture of 1a and 2b under the same conditions remained unchanged in a separatee xperiment.…”

Recent advances in the synthesis and applications of 2,6-dipyrazolylpyridine derivatives and their complexes

“…52,101,[142][143][144][145][146][147][148][149] Appending extra donor groups onto the 3-bpp skeleton gives further scope for high-nuclearity complex formation. Thus, the diphenoxo derivative L 19 66,72,[163][164][165] None of these studies used a chiral bpp derivative as co-ligand, although those are easily accessible for the 1-bpp series. 6 Bubbling O 2 195 The number of miscellaneous complexes of 3-bpp derivatives is much smaller but 10 more varied, [196][197][198][199] and includes manganese(II), 196 samarium(III) 198 and gold(III) 199 compounds.…”