Copper phosphates and phosphinates with pyridine/pyrazole alcohol co-ligands: Synthesis and structure

Copper Phosphinate Complexes as Molecular Precursors for Ethanol Dehydrogenation Catalysts

Nowadays, the production of acetaldehyde heavily relies on the petroleum industry. Developing new catalysts for the ethanol dehydrogenation process that could sustainably substitute current acetaldehyde production methods is highly desired. Among the ethanol dehydrogenation catalysts, copper-based materials have been intensively studied. Unfortunately, the Cu-based catalysts suffer from sintering and coking, which lead to rapid deactivation with time-on-stream. Phosphorus doping has been demonstrated to diminish coking in methanol dehydrogenation, fluid catalytic cracking, and ethanol-to-olefin reactions. This work reports a pioneering application of the well-characterized copper phosphinate complexes as molecular precursors for copper-based ethanol dehydrogenation catalysts enriched with phosphate groups (Cu-phosphate/SiO2). Three new catalysts (CuP-1, CuP-2, and CuP-3), prepared by the deposition of complexes {Cu(SAAP)}n (1), [Cu6(BSAAP)6] (2), and [Cu3(NAAP)3] (3) on the surface of commercial SiO2, calcination at 500 °C, and reduction in the stream of the forming gas 5% H2/N2 at 400 °C, exhibited unusual properties. First, the catalysts showed a rapid increase in catalytic activity. After reaching the maximum conversion, the catalyst started to deactivate. The unusual behavior could be explained by the presence of the phosphate phase, which made Cu2+ reduction more difficult. The phosphorus content gradually decreased during time-on-stream, copper was reduced, and the activity increased. The deactivation of the catalyst could be related to the copper diffusion processes. The most active CuP-1 catalyst reaches a maximum of 73% ethanol conversion and over 98% acetaldehyde selectivity at 325 °C and WHSV = 2.37 h-1.

pH-Dependent structural diversity of a 2-pyridinemethanol Cu complex and its relatively strong magnetic exchange coupling via hydrogen bonding

The diversity of the self-assembled structures of a Cu complex via hydrogen bonding, including a square planar unit, is reported. The Cu complex forms two self-assembled structures by hydrogen bonding, depending on the acidity of the recrystallization conditions. A linear chain structure can be produced under acidic conditions, and a three-dimensional network structure is observed under basic conditions. The linear chain structure is constructed from intermolecular sharing of a hydrogen atom between two 2-pyridinemethanolate units, with an OO distance of 2.412(1) Å and an O-H-O bond angle of 170(3)°. The linear chain structure exhibits relatively strong magnetic coupling (J = -9.91(2) cm^-1) via hydrogen bonding between Cu atoms; this coupling was also confirmed by electron spin resonance experiments. Thermochromic behavior was also observed for the complex.

Intriguing structural chemistry of neutral and anionic layered monoalkylphosphates: single-source precursors for high-yield ceramic phosphates

A simple protocol for multi-gram synthesis of unstable and normally inaccessible phosphate monoesters ROPO₃H₂ is reported, apart from demonstration of their thermal instability and utility as starting materials for metal phosphate single source precursors.

Role of 4,4′-bipyridine versus longer spacers 4,4′-azobipyridine, 1,2-bis(4-pyridyl)ethylene, and 1,2-bis(pyridin-3-ylmethylene)hydrazine in the formation of thermally labile metallophosphate coordination polymers

Uncoordinated N-donors spacers in the title compounds facilitate interesting orthogonal H-bonding, leading to the formation of 3-D polymeric networks.

Bis(acetato-κO)bis-[2-(pyridin-2-yl)ethanol-κ(2)N,O]copper(II)

The title compound, [Cu(CH₃COO)₂(C₇H₉NO)₂], is a monomeric complex with an octa­hedral geometry. The Cu^II atom is located on an inversion center and is coordinated by acetate and 2-(pyridin-2-yl)ethanol ligands. The acetate group is coordinated in a monodentate manner, while the 2-(pyridin-2-yl)ethanol is coordinated as a bidentate ligand involving the endocyclic N atom and the hy­droxy O atom of the ligand side chain. An intra­molecular hydrogen bond is observed between the hy­droxy O atom and the non-coordinated acetate O atom. No classical inter­molecular hydrogen-bond contacts were observed. However, the crystal packing is effected by C—H⋯O inter­actions, which link the mononuclear entities into layers parallel to the bc plane.