Bridging Methylene to Bridging Acyl Conversion in Heterobinuclear Rh/Ru Complexes: Models for Adjacent-Metal Involvement in Bimetallic Catalysts

Reversible Discrete-to-Extended Metal-Organic Polyhedra Transformation by Sulfonic Acid Surface Functionalization

Metal-organic polyhedra (MOPs) are molecular porous units in which desired functionalities can be installed with precise geometrical and compositional control. By combing two complementary chemical moieties, such as sulfonic acid groups and Rh(II)-carboxylate paddlewheel, we synthesized a robust water-soluble cuboctahedral MOP with excellent features in both solution and solid states. Herein, we demonstrate that the superior chemical stability of the Rh₂ unit and the elevated number of functional groups on the surface (24 per cage) result in a porous cage with high solubility and stability in water, including acidic, neutral, and basic pH conditions. We also prove that the sulfonic acid-rich form of the cage can be isolated through postsynthetic acid treatment. This transformation involves an improved gas uptake capacity and the capability to reversibly assemble the cages into a three-dimensional (3D) metal-organic framework (MOF) structure. Likewise, this sulfonic acid functionalization provides both MOP and MOF solids with high proton conductivities (>10^-3 S cm^-1), comparable to previously reported high conducting metal-organic materials. The influence of the MOP-to-MOF processing in the gas adsorption capacity indicates that this structural transformation can provide materials with higher and more controllable porous properties. These results illustrate the high potential of acidic MOPs as more flexible porous building units in terms of processability, structural complexity, and tunability of the properties.

Unusual cyanide and methyl binding modes at a dicobalt macrocycle following acetonitrile C-C bond activation

This communication describes the C-C bond activation of acetonitrile and the trapping of the methyl and cyanide fragments by macrocyclic, dicobalt complexes. Both products display unique structural features as a result of the constraints imposed by the macrocycle. The bridged species [(3PDI2)Co2(μ-CN)(PMe3)2][OTf] ([Co2CN]+) exhibits atypical Co-CN-Co binding, and upon either phosphine dissociation or oxidation, the flexible ligand framework is able to switch between different binding modes of μ-cyanide. Further, the bridging methyl species [(3PDI2)Co2(μ-CH3)(PMe3)][OTf] ([Co2CH3]+) is the first structurally characterized dicobalt complex with a bridging methyl group.

Hydroformylation of vinyl acetate and cyclohexene over TiO2 nanotube supported Rh and Ru nanoparticle catalysts

TiO2 nanotube (TNT) supported Rh and Ru nanoparticle catalysts were prepared via impregnation-photoreducing procedure and characterized with various methods. Their catalytic performances in hydroformylation were evaluated by using vinyl acetate and cyclohexene as substrates. The results indicate that the presence of Ru in the catalysts can enhance the catalytic activity of catalysts for the hydroformylation of vinyl acetate, but do not play the same role in the hydroformylation of cyclohexene; the sequence of loading metal has a significant effect on the catalytic performances of the title catalysts. Additionally, it is found that Ru/TNTs shows catalytic activity for the hydroformylation of vinyl acetate though it does not for the hydroformylation of cyclohexene.

Transmetalation supported by a Pt(II)-Cu(I) bond

Passing Me over: platinum-to-copper methyl transfer is observed upon collision-induced dissociation (CID) of the cations formed by the interaction of the [(R(3)P)Cu](+) fragment with [(dmpe)PtMe(2)] (R=Me, Ph, Cy, tBu; dmpe=bis(dimethylphosphino)ethane; see X-ray crystal structure of coordination spheres for R=tBu). The thermochemistry of these processes for R=Me is investigated by mass-spectrometric methods.

Selective formation of cis-diacyl, cis-PPh(2)R rhodium(III) complexes by the reaction of rhodium(III) cis-diacyl, trans-PPh(2)R complexes with aliphatic diamines

The cis-diacyl, trans-PPh(2)R complex [RhCl(PPh(2)(o-C(6)H(4)CO))(2)(pyridine)] () reacts with substituted aliphatic diamines to afford selectively cationic cis-diacyl, cis-PPh(2)R, diamine derivatives [Rh(PPh(2)(o-C(6)H(4)CO))(2)(NN')](+) (NN' = 1,2-diphenylethylenediamine, 2; 1,2-propanediamine, 3; N-methylethylenediamine, 4; N,N-dimethylethylenediamine, 5; N,N'-dimethylethylenediamine, 6; N,N,N'-trimethylethylenediamine, 7) with high stereoselectivity depending on the N-donor ligand employed. Complexes 2 and 3 contain a single isomer, while 4 is a mixture of two isomers, 4a and 4b. Formation of 4a occurs first and is followed by isomerisation to 4b until the equilibrium 4a:4b = 1:4 ratio is attained. In contrast, 5 and 6 contain a single isomer. More basic amino groups prefer positions trans to an acyl group while less basic amino groups are trans to a phosphine group. The preferred intramolecular N-H...O hydrogen bond formation between an amino and an acyl coordinated ligands, trans to the phosphorus atoms, appears to be relevant to the selectivity observed. 7 is a mixture of two isomers 7a and 7b in a 7a:7b = 5.7:1 ratio. N,N,N',N'-tetramethylethylenediamine or N,N'-diphenylethylenediamine led to the elimination of the N-donor ligands and the formation of a mixture of isomers of [Rh(2)(mu-Cl)(mu-PPh(2)(o-C(6)H(4)CO))(2)(PPh(2)(o-C(6)H(4)CO))(2)](+) (), where the Rh atoms are triply bridged by two acyl groups in a head-to-tail arrangement and by a chloride. The reaction of [Rh(PPh(2)(o-C(6)H(4)CO))(2)(ndmeen)]ClO(4) (5) with acids led to the displacement of the diamine and the formation of a [8a](+):[8b](+):[8c](+) = 1:1:3 mixture. 8c, containing the weakest sigma-donor oxygen atoms trans to the strongest sigma-donor acyl groups, represents the most electronically favourable geometry for . All the complexes were fully characterized spectroscopically. Single crystal X-ray diffraction analysis was performed on 5, 6, 8a and 8b.

Mechanistic Investigations of Imine Hydrogenation Catalyzed by Dinuclear Iridium Complexes

Treatment of [Ir2(mu-H)(mu-Pz)2H3(NCMe)(PiPr3)2] (1) with one equivalent of HBF4 or [PhNH=CHPh]BF4 affords efficient catalysts for the homogeneous hydrogenation of N-benzylideneaniline. The reaction of 1 with HBF4 leads to the trihydride-dihydrogen complex [Ir2(mu-H)(mu-Pz)2H2(eta2-H2)(NCMe)(PiPr3)2]BF4 (2), which has been characterized by NMR spectroscopy and DFT calculations on a model complex. Complex 2 reacts with imines such as tBuN=CHPh or PhN=CHPh to afford amine complexes [Ir2(mu-H)(mu-Pz)2H2(NCMe){L}(PiPr3)2]BF4 (L = NH(tBu)CH2Ph, 3; NH(Ph)CH2Ph, 4) through a sequence of proton- and hydride-transfer steps. Dihydrogen partially displaces the amine ligand of 4 to form 2; this complements a possible catalytic cycle for the N-benzylideneaniline hydrogenation in which the amine-by-dihydrogen substitution is the turnover-determining step. The rates of ligand substitution in 4 and its analogues with labile ligands other than amine are dependent upon the nature of the leaving ligand and independent on the incoming ligand concentration, in agreement with dissociative substitutions. Water complex [Ir2(mu-H)(mu-Pz)2H2(NCMe)(OH2)(PiPr3)2]BF4 (7) hydrolyzes N-benzylideneaniline, which eventually affords the poor hydrogenation catalyst [Ir2(mu-H)(mu-Pz)2H2(NCMe)(NH2Ph)(PiPr3)2]BF4 (11). The rate law for the catalytic hydrogenation in 1,2-dichloroethane with complex [Ir2(mu-H)(mu-Pz)2H2(OSO2CF3)(NCMe)(PiPr3)2] (8) as catalyst precursor is rate = k[8]{p(H2)}; this is in agreement with the catalytic cycle deduced from the stochiometric experiments. The hydrogenation reaction takes place at a single iridium center of the dinuclear catalyst, although ligand modifications at the neighboring iridium center provoke changes in the hydrogenation rate. Even though this catalyst system is also capable of effectively hydrogenating alkenes, N-benzylideneaniline can be selectively hydrogenated in the presence of simple alkenes.