34425-71-3Relevant articles and documents
Synthesis of Ether-Functionalized and Sterically Demanding Molybdenum Alkylidyne Complexes
àrias, òscar,Ehrhorn, Henrike,H?rdter, Johanna,Jones, Peter G.,Tamm, Matthias
, p. 4784 - 4800 (2019/01/04)
The synthesis of ether-functionalized molybdenum benzylidyne complexes [ArC-Mo{OC(CF3)2Me}3] (6, Ar = para-methoxyphenyl; 7, Ar = 2,4,6-trimethoxyphenyl) and of the sterically demanding benzylidyne complex [{2,4,6-(i-Pr)3C6H2}C-Mo{OC(CF3)2Me}3] are presented, together with their spectroscopic characterization, molecular structures, and catalytic activity in alkyne metathesis. Complexes 6 and 7 feature intermolecular contacts between the para-methoxy group and the molybdenum center that give rise to 1D-polymeric structures in the solid state. The preparation of other functionalized alkylidyne complexes, [ArC-Mo{OC(CF3)2Me}3] (Ar = 2-(i-PrO)C6H4, 8-MeO-Naph, 2,6-(i-Pr)2C6H3), was also attempted, but only the acyl precursors [ArC(=O)Mo(CO)5]- could be isolated. The synthesis of the molybdenum acyl complexes was challenging, and appropriate alternative protocols were developed.
Exploring electronic and steric effects on the insertion and polymerization reactivity of phosphinesulfonato pdii catalysts
Neuwald, Boris,Falivene, Laura,Caporaso, Lucia,Cavallo, Luigi,Mecking, Stefan
supporting information, p. 17773 - 17788 (2014/01/17)
Thirteen different symmetric and asymmetric phosphinesulfonato palladium complexes ([{(X1-Cl)-μ-M}n], M=Na, Li, 1= X(P^O)PdMe) were prepared (see Figure 1). The solid-state structures of the corresponding pyridine or lutidine complexes were determined for (MeO)21-py, (iPrO)21-lut, (MeO,Me2)1-lut, (MeO)31-lut, CF31-lut, and Ph1-lut. The reactivities of the catalysts X1, obtained after chloride abstraction with AgBF4, toward methyl acrylate (MA) were quantified through determination of the rate constants for the first and the consecutive MA insertion and the analysis of β-H and other decomposition products through NMR spectroscopy. Differences in the homo- and copolymerization of ethylene and MA regarding catalyst activity and stability over time, polymer molecular weight, and polar co-monomer incorporation were investigated. DFT calculations were performed on the main insertion steps for both monomers to rationalize the effect of the ligand substitution patterns on the polymerization behaviors of the complexes. Full analysis of the data revealed that: 1) electron-deficient catalysts polymerize with higher activity, but fast deactivation is also observed; 2) the double ortho-substituted catalysts (MeO)21 and (MeO)31 allow very high degrees of MA incorporation at low MA concentrations in the copolymerization; and 3) steric shielding leads to a pronounced increase in polymer molecular weight in the copolymerization. The catalyst properties induced by a given P-aryl (alkyl) moiety were combined effectively in catalysts with two different non-chelating aryl moieties, such as cHexO/(MeO)21, which led to copolymers with significantly increased molecular weights compared to the prototypical MeO1. Catalyst control: The influence of steric and electronic effects on the reactivity of phosphinesulfonato PdII catalysts in polymerization and copolymerization is explored through experimental and DFT methods. A comparison of thirteen different X(P O)PdMe catalysts ((P O)= κ2-P,O-R1R2PC6H 4SO2O; see figure) reveals insights into the catalyst reactivity toward methyl acrylate and ethylene, their influence on the polymer microstructure, and the decomposition pathways. The unraveling of these relations provides guidelines for a directed choice of catalysts. Copyright
Preparative and Structural Chemistry of Diastereomeric Derivatives of 3-PhosphanylpyrroIidine and Their Palladium(II) Complexes -Asymmetric Grignard Cross-Coupling Reaction
Nagel, Ulrich,Nedden, Hans Guenter
, p. 989 - 1006 (2007/10/03)
The preparation of both diastereomeric derivatives of 3-(diphenylphosphanyljpyrrolidine with chiral (tetrahydrofuran2-yl}methyl and [(/V-neopentyl)pyrrolidin-2-yl]methyl groups as substituents on the pyrrolidine nitrogen atom and of (2S,4S)-l-benzyl-4-(diphenylphosphanyl)-2-(methoxymethyljpyrrolidine is reported. [3S,P(fiS)]-3-(phenylphosphanyljpyrrolidine, bearing an additional chiral center on phosphorus, is the starting material for the preparation of phosphanes, in which one phenyl group of the PPh2 moiety is substituted by an 2-methoxyphenyl (= An) or 2,4,6-trimethoxyphenyl (= TMP) group. PdI2 complexes of these ligands were separated into diastereomers by chromatography on silica gel columns. The structural chemistry of these novel phosphane diastereomers and their PdI2 complexes is investigated by X-ray crystallography and NMR. At the P,N-coordinated palladium center displacement of an iodide anion is found for P,N,N' ligands only. In the nickel complex catalysed cross-coupling reaction, yielding 3-phenyl-l-butene, we obtain the highest enantioselectivities in the case of simple l-alkyl-3-(diphenylphosphanyl)pyrrolidine ligands. The enantioselectivity obtained with diastereomeric derivatives, bearing additional ether or amine ligating sites is mainly determined by the chiral center in 3-position of the 3-(phosphanyl)pyrrolidine part of these ligands. Optimisation of enantioselectivity with these ligands can be carried out by a variation of the ligand to nickel ratio and by the choice of the vinyl halide used as starting compound. The catalytic cycle must contain at least one catalytically active species, bearing more than one ss-aminoalkylphosphane ligand. VCH Verlagsgesellschaft mbH,.
