Pyrazole-pyridine-pyrazole (NNN) ruthenium(II) complex catalyzed acceptorless dehydrogenation of alcohols to aldehydes

CO2-mediated hydrogen storage and release cycles realized by a bimetallic ruthenium complex in pure water

CO2-mediated liquid H2 storage is a promising technology; however, it typically requires additives such as bases, which increase both cost and energy consumption. Herein, a bimetallic Ru complex is fabricated that catalyzes reversible cycles of CO2 hydrogenation to formic acid (FA) and FA dehydrogenation in pure water without any additives. The H2 storage and release cycles are controlled simply by varying the H2 pressure at 80 °C. Moreover, the system maintains its activity over at least 15 cycles (240 h), achieving a cumulative H2 storage of nearly 2000 μmol. Labeling experiments using 13CO2 and D2 confirm the origins of the C and H atoms in FA. This efficient, green, and mild system demonstrates potential for sustainable hydrogen energy applications.

A well-defined phosphine-free metal-ligand cooperative route for N-alkylation of aromatic amines via activation of renewable alcohols catalyzed by NNN pincer cobalt(II) complexes

This study presents the direct N-alkylation of aromatic amines using greener primary alcohols as alkyl donors, catalyzed by base metal-derived Co(II) catalysts via the borrowing hydrogen (BH) method. Two well-defined phosphine-free NNN-type pincer ligands (L1 and L2) were synthesized and utilized to prepare cobalt(II) catalysts C1 and C2. The catalysts were well characterized by UV-vis, IR, HRMS, and single-crystal X-ray diffraction studies. The catalysts C1 and C2 were utilized for the N-alkylation of various aromatic, heteroaromatic as well as aromatic diamines, and a wide substrate scope total of 30 derivatives was explored with isolated yields up to 95%. Two antihistamine drug precursors for tripelennamine and mepyramine were synthesized on a gram scale for the large-scale applicability of the current protocol. Various control experiments were also performed to explore the possible reaction intermediates and reaction pathway. Cobalt(II) intermediates involved in the catalytic cycle were also characterized by the HRMS study.

Synthesis and characterization of heptacoordinated molybdenum(II) complexes supported with 2,6-bis(pyrazol-3-yl)pyridine (bpp) ligands

Functional pincer ligands that engage in metal-ligand cooperativity and/or are capable of redox non-innocence have found a great deal of success in catalysis. These two properties may be found in metal complexes of the 2,6-bis(pyrazol-3-yl)pyridine (bpp) ligands. With this goal in mind, we have attempted the coordination of 2,6-bis(5-trifluoromethylpyrazol-3-yl)pyridine (LCF3) and its tBu analogue 2,6-bis(5-tert-butylpyrazol-3-yl)pyridine (LtBu) to Mo(0) by reactions with mixed phosphine/carbonyl complexes [Mo(CO)2(MeCN)n-1(PMe3-nPhn)5-n] 1-3 (1 ≤ n ≤ 3). These afforded mixtures of several Mo compounds among which low yields of heptacoordinated Mo(II) complexes [Mo(CO)2(bpp)(PMe3-nPhn)2] 4a-c (LCF3-supported) and 5a-c (LtBu-supported) bearing a doubly deprotonated bpp ligand were systematically produced. More selective syntheses of 4a-c and 5a-c were achieved by repeating these experiments in the presence of an oxidant (AgOAc or Ag2O), with moderate to good yields. 4a-c and 5a-c were characterized by means of NMR, IR and UV-Vis spectroscopies, sc-XRD and cyclic and square-wave voltammetries for 4a, 4b and 5b. The deprotonated LtBu ligand in 5a-c is re-protonated with 2 equiv. of HOTf to afford the dicationic [Mo(CO)2(LtBu)(PMe3-nPhn)2][OTf]2 complexes 6a-c. Acidic treatment of 4a-c led to the decomposition of the complexes.

Micropores in Hollow Organic Cage Nanocapsule as a Size Exclusion Gate: Cage Entrapped Pd(II)-Catalyst for Efficient Cross-Coupling Reaction

Hollow porous organic capsules (HPOCs) with an entrapped active catalyst have nanosized cavities, providing the benefits of a nanoreactor, as well as separation of the catalysts from the reaction medium via pores acting as a size-exclusion gate. Such purpose-built HPOCs with desired molecular weight cutoffs offer the advantages of semipermeable membrane separation and a sustainable chemical process that excludes energy-extensive separation. Here, we report a newly synthesized HPOC with an entrapped Pd(PPh3)2Cl2 as the catalyst for demonstrating a Suzuki-Miyaura coupling reaction as a proof of concept.