Preparation of Dinuclear Phosphine-Bridged Palladium(II) Species and Their Silica-Bound Analogues as Catalysts for the Cyclization of Aminoalkynes

Chemoselective Hydrogenation with Supported Organoplatinum(IV) Catalyst on Zn(II)-Modified Silica

Well-defined organoplatinum(IV) sites were grafted on a Zn(II)-modified SiO₂ support via surface organometallic chemistry in toluene at room temperature. Solid-state spectroscopies including XAS, DRIFTS, DRUV-vis, and solid-state (SS) NMR enhanced by dynamic nuclear polarization (DNP), as well as TPR-H₂ and TEM techniques revealed highly dispersed (methylcyclopentadienyl)methylplatinum(IV) sites on the surface ((MeCp)PtMe/Zn/SiO₂, 1). In addition, computational modeling suggests that the surface reaction of (MeCp)PtMe₃ with Zn(II)-modified SiO₂ support is thermodynamically favorable (Δ G = -12.4 kcal/mol), likely due to the increased acidity of the hydroxyl group, as indicated by NH₃-TPD and DNP-enhanced ¹⁷O{¹H} SSNMR. In situ DRIFTS and XAS hydrogenation experiments reveal the probable formation of a surface Pt(IV)-H upon hydrogenolysis of Pt-Me groups. The heterogenized organoplatinum(IV)-hydride sites catalyze the selective partial hydrogenation of 1,3-butadiene to butenes (up to 95%) and the reduction of nitrobenzene derivatives to anilines (up to 99%) with excellent tolerance of reduction-sensitive functional groups (olefin, carbonyl, nitrile, halogens) under mild reaction conditions.

Novel iminopyridine derivatives: ligands for preparation of Fe(ii) and Cu(ii) dinuclear complexes

A series of imino- and amino-pyridine ligands based on dihydrobenzofurobenzofuran (BFBF) and methanodibenzodioxocine (DBDOC) backbones have been synthesized. These ligands form exclusively dinuclear complexes with metals such as iron(II) and copper(II). The structures for complexes 15, 16, 18, 19, 20, 21, 23, and 24 were determined by X-ray crystallography. The complexes show large distances for the metal nuclei and different geometries depending on the nature of the metal. An octahedral geometry was observed for the iron(II) complexes, while copper(II) complex 24 showed a distorted trigonal bipyramidal geometry. The iron(II) complexes showed activity as catalysts in the cycloaddition of CO2 to epoxides, obtaining moderate yields of cyclic carbonates.

Facile preparation of homo- and hetero-dimetallic complexes with a 4-phosphino-substituted NHC ligand. Toward the design of multifunctional catalysts

A series of bimetallic complexes have been synthesized that are supported by a 4-phosphino-substituted NHC ligand. The use of this stable ligand reduces the number of synthetic steps and allows for a wide range of metal combinations to be introduced into the complexes.

An approach to bimetallic catalysts by ligand design

New diphosphines based on benzofurobenzofuran and dibenzodioxocin backbones, forming exclusively bimetallic complexes were designed and synthesized. Depending on the ligand to metal ratio, face-to-face bimetallic complexes or syn-chloride bridged dimeric complexes were formed as main reaction products. The structures of the rhodium complexes of the new ligands 4, 7, 10, 13, 16 were established in solution by NMR, IR, and MS spectroscopy. The molecular structures of the syn-chloride bridged dimeric complexes [Rh(2)(CO)(2)(mu-Cl)(2)(4)] (22), [Rh(2)(CO)(2)(mu-Cl)(2)(10)] (24), and the face-to-face bimetallic complexes [Rh(CO)Cl(4)](2) (17), [Rh(CO)Cl(10)](2) (19), and [Rh(CO)Cl(13)](2) (20) were confirmed by X-ray crystallography. Ligands 4, 7, 10, 13, 16, and SPANphos were tested in rhodium catalyzed methanol carbonylation at 150 degrees C and 22 bar of CO gas, showing high activities under catalytic conditions.

Thermal properties of metal-metal bonded Pd(I) complexes supported onto porous Vycor glass

Thermal behavior of the complexes Pd2(dppm)2Cl2, Pd2(dppm)2(SnCl3)Cl and Pd2(dppm)2(SnCl3)2 (dppm = bis[diphenylphosphino(methane)], ((C6H5)2PCH2P(C6H5)2) in the solid state and immobilized onto porous Vycor glass was studied. Similar decomposition mechanisms were observed for the solid and immobilized complexes, with a small thermal stabilization upon immobilization. The decomposition products were characterized by X-ray diffractometry, Raman and diffuse reflectance infrared spectroscopy, which indicated the presence of a mixture of metallic palladium and oxidized species such as PdO,condensed phosphates, SnO2 and SnP2O7. According to X-ray diffractometry, the decomposition products of the immobilized complexes presented higher amounts of PdO than the solid-state residues, probably as an effect of interactions with silanol groups present in the glass surface.

Electronic Structures and Spectroscopic Properties of Mono- and Binuclear d8 Complexes: A Theoretical Exploration on Promising Phosphorescent Materials

The structures of trans-[M(2)(CN)(4)(PH(2)CH(2)PH(2))(2)] (M = Pt (1), Pd (2), and Ni (3)), trans-[Pt(2)X(4)(PH(2)CH(2)PH(2))(2)] (X = Cl (4) and Br (5)), and trans-[M(CN)(2)(PH(3))(2)] (M = Pt (6), Pd (7), and Ni (8)) in the ground state were optimized using the MP2 method. Frequency calculations reveal that the weak metal-metal interaction is essentially attractive for 1, 2, 4, and 5 but not for 3. The TD-DFT calculations associated with the polarized continuum model (PCM) were performed to predict absorption spectra in CH(2)Cl(2) solution. Experimental spectra are well reproduced by our results. With respect to analogous mononuclear d(8) complexes (6-8), a large red shift of the absorption wavelength was calculated for the binuclear d(8) complexes (1-3). Relative to 1 with unsaturated CN- donors, introduction of saturated halogen donors into 4 and 5 changes their electronic structures, especially the HOMO and LUMO. The TD-DFT and subsequent unrestricted MP2 calculations predict that 1 produces the lowest-energy d --> p emission while 2-5 favor the d --> d emissions, agreeing with experimental observations.