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.

Non-symmetrical bis(aminoalkyl)phosphinates: new ligands with enhanced binding of Cu(ii) ions

Novel, non-symmetrical bis(aminoalkyl)phosphinic acids exhibit enhanced efficiency in Cu(ii) ion binding.

trans-Dichlorido-tetra-kis-[(di-methyl-phosphor-yl)methanaminium-κO]cobalt(II) tetra-chloridocobaltate(II)

The asymmetric unit of the title structure, [CoCl₂(C₃H₁₁NOP)₄][CoCl₄]₂, consists of one half of the trans-dichlorido­tetra­kis­[(di­methyl­phosphor­yl)methanaminium]cobalt(II) tetra­cation lying on an inversion center and one tetra­chloridocobaltate(II) dianion on a general position. Four O-coordinated cationic (di­methyl­phosphor­yl)methanaminium (dpmaH⁺) ligands occupy the equatorial coordination sites, whereas the chloride ligands occupy axial positions of the roughly o­cta­hedral coordination polyhedron of the cobalt metal center. Intra­molecular hydrogen bonds between the aminium groups and the O atom of the phosphoryl groups and additional hydrogen bonds between the aminium groups and the chloride ligands are present. Furthermore, four of the six H atoms not involved in intra­molecular bonding of each cobalt(II) tetra­cation form weak hydrogen bonds to four adjacent tetra­chloridocobaltate(II) counter-anions. By these inter­molecular hydrogen bonds, one-dimensional polymeric strands are formed along the b-axis direction. The hydrogen bonding is analyzed using the graph-set method and the structural similarity with dpmaHCl is discussed.

Pseudosymmetric fac-di-aqua-trichlorido[(di-methyl-phosphor-yl)methanaminium-κO]manganese(II)

In the title compound, [Mn(C₃H₁₁NOP)Cl₃(H₂O)₂], the Mn^II metal center has a distorted o­cta­hedral geometry, coordinated by the three chloride ligands showing a facial arrangement. Two water mol­ecules and the O-coordinated dpmaH cation [dpmaH = (di­methyl­phosphor­yl)methanaminium] complete the coordination sphere. Each complex mol­ecule is connected to its neighbours by O—H⋯Cl and N—H⋯Cl hydrogen bonds. Two of the chloride ligands and the two water ligands form a hydrogen-bonded polymeric sheet in the ab plane. Furthermore, these planes are connected to adjacent planes by hydrogen bonds from the aminium function of cationic dpmaH ligand. A pseudo-mirror plane perpendicular to the b axis in the chiral space group P2₁ is observed together with inversion twinning [ratio = 0.864 (5):0.136 (5)].

Synthesis, characterization, and in vivo skeletal localization of a new 99mTc-based multidentate phosphonate chelate: 5-Amino-1,3-bis(ethylamine-(N,N dimethyl diphosphonic acid) acetamido) benzene

The tetraphosphonate ligand, 5-amino-1,3-bis(ethylamine-(N,N-dimethyl diphosphonic acid) acetamido) benzene (IPTMP) used in the present study was prepared from 5-nitroisophthalate dimethylester to label with radionuclide for targeted diagnosis and therapy. The synthesized multidentate phosphonate ligand was characterized on the basis of spectroscopic techniques, which exhibited good metal ion control properties when complexed to (99m)Tc with high in vitro and in vivo stability. Excellent quality bone images of rabbit were imaged showing rapid clearance of background activity and visualization of skeleton at 1h.

Redox-active pH-responsive molecules: ferrocenylphosphonic acid, ferrocenylmethylphosphonic acid and 1,1′-ferrocenylbisphosphonic acid. Structural determination of FcPO3Na2·5H2O

The acidity constants of the reduced and oxidized species of ferrocenylphosphonic acids FcPO3H2, FcCH2PO3H2 and fc(PO3H2)2 (Fc = (eta5-C5H5)Fe(eta5-C5H4), fc = (eta5-C5H4)Fe(eta5-C5H4)) in water have been evaluated by potentiometric, 31P NMR, and electrochemical methods. The oxidized forms are more acidic than the reduced ones. The interaction between the redox centre and the charged oxygen atoms of the phosphonate group is shown to be electrostatic. The maximum oxidation shift DeltaE between the protonated and unprotonated species increases with the number of charges of the substrate and decreases with the increase of the distance between the ferrocenyl centre and the oxygen atoms of the phosphonate group. The structure of FcPO3Na2.5H2O is determined. The compound crystallizes in the monoclinic system. It is lamellar with an inorganic layer formed by tetramers Na4O14, the ferrocenyl groups occupying the interlamellar space.

Copper(II) complexes of some N-substituted bis(aminomethyl)phosphinate ligands. An integrated EPR study of microspeciation and coordination modes by the two-dimensional simulation method

Copper(II) complexes of bis(aminomethyl)phosphinic acid (L1), bis(N-glycino-N-methyl)phosphinic acid (L2), bis(N-benzylglycino-N-methyl)phosphinic acid (L3), bis(l-prolino-N-methyl)phosphinic acid (L4) and bis(iminodicarboxymethyl-N-methyl)phosphinic acid (L5) were studied in aqueous solution by pH-potentiometric and electron paramagnetic resonance (EPR) spectroscopic methods. The EPR spectrum packages recorded at various ligand-to-metal concentration ratios and pH's were analyzed (after matrix rank analysis by the method of residual intensities as a complementary method) by the two-dimensional computer simulation method, which simultaneously determines the formation constants and the EPR parameters of the various (micro)species. L1 forms mono and bis complexes in different protonation states; for the other ligands, the mono complexes are always prevalent. For steric reasons, the formation of CuL is shifted to increasingly higher pH regions in the sequence L2, L3 and L4. CuLH was identified for L3, L4 and L5, and also CuLH(2) for L4 and L5. Cu(2)L(2) was found in small amounts for L3 and L4, while it predominates at pH>4 for L5. For L5, Cu(2)L(2)H(2) was also detected. For the ligands that form dimeric metal complexes in equimolar solution or at a ligand excess, Cu(2)L is formed at a metal ion excess. Ligation of the phosphinate O was suggested by indirect proofs in the protonated complexes of L1. For the ligands L2, L3 and L4, the copper(II) coordination in various species in different protonation states is reminiscent of that in the mono and bis complexes of simple amino acids. For the bis(aminomethyl)phosphinates, however, the cis positions of the amino groups in CuL are ensured by the structure of the ligand, and the isomers differ from each other in the (equatorial or axial) position of the second carboxylate group.