Homogene katalytische hydrierung von aldehyden in substanz mit IrH3(PPh3)3 (2023)

A new family of rhodium and iridium compounds with the bulky tris(ortho-methoxyphenyl) phosphine (PAn₃) was synthesized and characterized by NMR methods. The X-ray crystal structures of RhCl(PAn₃)(COD) (1) and Ir[(PBz₃)(PAn₃)(COD)]PF₆ (4) have been determined. A stabilizing agostic interaction has been crystallographically observed in both compounds, due to the steric hindrance of the ortho-substituted phosphine ligand and its presence has been associated to the fluxional behavior shown by the complexes on the NMR timescale in solution. Iridium complexes containing PBz₃ and/or PAn₃ have been evaluated as catalyst precursors for the hydrogenation of trans-cinnamaldehyde (CNA), and their activities have also been compared to those of other iridium complexes containing bulky phosphine ligands, such as PTol₃ (tris-ortho-tolyl-phosphine). The catalytic experiments show that irrespectively of the phosphine combination, all of the evaluated catalysts prevalently hydrogenate the CC moiety. However, the product selectivity can be tuned by changing either the substrate/catalyst ratio or the phosphine ligand at the metal center. The catalyst with PAn₃ proved to be more efficient and also gave higher yields of the enol product, indicating that stereoelectronic effects are responsible for the changes in selectivity.

Five iridium complexes containing bidentate phosphine ligands, IrH(CO)(PPh₃)(BPPB) [BPPB=1,2-bis(diphenylphosphino)benzene] (1), IrH(CO)(PPh₃)(BISBI) [BISBI=2,2′-bis(diphenylphosphinomethyl)-1,1′-biphenyl] (2), IrH(CO)(PPh₃)(BDNA) [BDNA=1,8-bis(diphenylphosphinomethyl)naphthalene] (3), IrH(CO)(PPh₃)(BDPX) [BDPX=1,2-bis(diphenylphosphinomethyl)benzene] (4), and IrHCl(CO)(PCP) [PCP-H=1,3-bis(diphenylphosphinomethyl)benzene] (5) were synthesized. Their compositions and structures were identified by elemental analysis, FTIR, ${}^{\mathrm{<mtext>31</mtext>}}\text{P{}{}^{\mathrm{<mtext>1</mtext>}}\text{H}}$ NMR and ${}^1\text{H}$ NMR. The molecular structure of IrH(CO)(PPh₃)(BDNA) determined by single crystal X-ray diffraction indicated a trigonal bipyramidal structure with the three phosphorus atoms in the equatorial plane. The crystal belonged to triclinic system, P1 space group, a=11.47Å, b=11.65Å, c=19.20Å, α=81.95°, β=75.60°, γ=70.60°, and Z=2. The catalytic hydrogenation activities and selectivities of the five complexes as catalysts for citral and cinnamaldehyde were investigated. Complexes 1–4 showed high selectivity for the hydrogenation of CO group in citral. High selectivity for the hydrogenation of CO group in cinnamaldehyde catalyzed by complex 4 could be obtained in the presence of excess amount of ligand (BDPX).

A series of new hydridocarbonyl ruthenium(II) complexes containing chelating diphosphine ligands of the type [RuHCl(CO)(PPh₃)(L-L)] [L-L = Ph₂PCH₂PPh₂ 2, Ph₂PCH₂CH₂PPh₂ 3, Ph₂PCH₂CH₂CH₂PPh₂ 4, cis-Ph₂PCHCHPPh₂ 5 and Fe(η⁵-C₅H₄PPh₂)₂ 6] has been prepared by the reactions of [RuHCl(CO)(PPh₃)₃] 1 with Ph₂PCH₂PPh₂ [dppm, bis(diphenylphosphino)methane], Ph₂PCH₂CH₂PPh₂ [dppe, 1,2-bis(diphenylphosphino)ethane], Ph₂PCH₂CH₂CH₂PPh₂ [dppp, 1,3-bis(diphenylphosphino)propane], cis-Ph₂PCHCHPPh₂ [dppv, cis-1,2-bis(diphenylphosphino)ethylene] and Fe(η⁵-C₅H₄PPh₂)₂ [(dppf, 1,1′-bis(diphenylphosphino)ferrocene] in boiling PhMe. The compounds 2–6 are moderately stable in solution. The new compounds were characterized by elemental analysis, IR and ¹H NMR spectroscopy. Compounds 1–6 have been shown to catalyse the homogeneous hydrogenation of the CC bond of cyclohexene; some relations between structures and catalytic activities are described. The Arrhenius activation energy of cyclohexene for compound 4 is 33.0 kJ mol⁻¹.

Kinetic and mechanistic studies of the homogeneous hydrogenation of benzaldehyde were carried out using the cationic complex [RuH(CO)(NCMe)₂(PPh₃)₂]BF₄ (1) as the catalyst precursor, which was very efficient under mild reaction conditions in 2-methoxyethanol as the solvent. The experimental rate law was found to be r=(K₁k₂/1 + K₁[PhCHO])[Ru][PhCHO][H₂] (K₁ = 1.9 M⁻¹; k₂ = 12.5 M⁻¹ s⁻¹) which can be approximated to r=k_cat[Ru][PhCHO][H₂] (k_cat = 20 M⁻² s⁻¹). The activation parameters and the kinetic isotope effect were also calculated. The kinetic data and the coordination chemistry related to the hydrogenation of benzaldehyde are consistent with a mechanism involving the addition of hydrogen as the rate-determining step of the catalytic cycle.

The iridium(I)-perchlorato complex, Ir(ClO₄)(CO)(PPh₃)₂ catalyses the hydrogenation of aldehydes to alcohols at 25°C under atmospheric pressure of hydrogen.

Tetrahedron Letters, Volume 55, Issue 27, 2014, pp. 3648-3651

A simple and efficient procedure for the synthesis of iodoarenes is developed which involves the sequential diazotization–iodination of aromatic amines with sodium nitrite, nanomagnetic supported sulfonic acid, and potassium iodide under solvent-free conditions at room temperature.

Molecular Catalysis, Volume 475, 2019, Article 110503

Herein we report a novel homogeneous catalysis–liquid/solid separation catalytic system for highly effective recycling of homogeneous catalyst based on a phosphine-functionalized polyether guanidinium ionic liquid (P-PolyGIL) with a room temperature liquid/solid phase transition characteristic. This novel catalytic system has perfectly integrated the advantages of both the homogeneous and biphasic catalysis to realize the combination of the high activity, easy catalyst recycling and long service-life of the catalyst without a significant loss of the activity, selectivity and Rh for more than 30 cycles in the Rh-catalysed hydroformylation of higher olefins. The long service-life of the catalyst could be attributed to the efficient and practical strategy of the catalyst separation.

European Journal of Medicinal Chemistry, Volume 81, 2014, pp. 253-266

A novel series of symmetrically substituted 3,3-dibenzyl-4-hydroxy-3,4-dihydro-1H-quinolin-2-ones was synthesized and tested as antimicrobials. The minimum inhibitory concentration (MIC) values of the most active heterocycles were slightly higher than those exhibited by levofloxacin, employed as comparator. Structural factors affecting the activity were explored along three diversification points, including the substituents of the aromatic rings of the 3-benzyl moieties, as well as the functionalization of both, the homocyclic ring of the heterocycle and the quinolonic nitrogen atom. 6-Chloro and 3,3-bis(4′-chlorobenzyl) derivatives showed the lower MIC values. Optimally substituted heterocycles were synthesized, which exhibited enhanced activity.

Chalcogenide Glasses, 2014, pp. 3-35

The methods of preparation of chalcogenide glasses for infrared fiber optics with low content of limiting impurities have been developed. The methods are based on solidification of glass-forming melts prepared by melting the initial high-purity elements in evacuated silica ampoule and purified additionally with chemical and distillation procedures. The effect of impurities (oxygen, hydrogen, carbon, sulfur, inclusions) on optical transmission of glasses was determined. The optical, thermal and crystallization properties of glasses were studied. Chalcogenide glass-based, low loss, multimode and single-mode optical fibers are produced with technical and operation characteristics sufficient for a number of cutting-edge applications. Factors affecting the optical absorption of glasses and optical fibers are analyzed.

Polyhedron, Volume 120, 2016, pp. 134-141

The carboxylic amides N-methylbenzamide (HLa), phthalimidine (HLb) and pyridine-2-one (HLc) were diphenylphosphino-functionalized (with ClPPh₂ and a base, n-BuLi for HLa, triethylamine for HLb and HLc) to yield the N-PPh₂ derivatives of N-methylbenzamide (1a) and of phthalimidine (1b) as well as the O-PPh₂ derivative 2-diphenylphosphinoxypyridine (1c). Thus, 1a and 1b represent P,O-chelate ligands, whereas 1c is a P,N-chelate ligand. Both P,O-ligands (1a, 1b) react with [RuCl₂(PPh₃)₃] in a two-step fashion to form mono-chelates with trans-situated Cl atoms (2a, 2b) upon using a 1:1 stoichiometric ratio or Cl-trans bis-chelates (3a^II, 3b^II) upon using two equivalents of the chelator. In contrast, reaction of [RuCl₂(PPh₃)₃] and the P,N-chelator 1c in 1:1molar ratio immediately produced a bis-chelate (3c^I) with an all-cis orientation of the ligands (while 50% of the [RuCl₂(PPh₃)₃] starting material remained unreacted). Compound 3c^I slowly isomerizes to the Cl-trans isomer (3c^II). All isolated compounds were characterized with multi-nuclear NMR spectroscopy, single-crystal X-ray diffraction and elemental analysis.

Coordination Chemistry Reviews, Volumes 304–305, 2015, pp. 55-72

This review is focused on the photocatalytic properties of the Re(I) compounds in the reduction of H⁺ and their use in solar energy conversion. Different systems are discussed in terms of the photosensitizer – usually containing the core [ReX(CO)₃diimine]⁺ – and mechanistic details are provided. The effect of the axial ligand and coordination of solvent water or TEOA on hydrogen evolution rates is also discussed. Supramolecular systems that mimic enzymes by combining both the photsenzitizer and the catalyst are also presented.