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Interfacial Catalysis at Oil/Water Interfaces
Published in Alexander G. Vdlkdv, Interfacial Catalysis, 2002
In catalysis the excess of a phosphine ligand is often necessary because it preserves the active species in the medium [2a]. However, it retards to some extent the co-ordination of the alkene to the metal center. Recent studies, performed by Monflier and coworkers, have shown that the water-soluble TPPTS ligand could reduce the rate of the reaction by another effect. Indeed, TPPTS can be included partially in the cyclodextrin hydrophobic cavity [53,54]; NMR measurements, observation by UV-visible spectroscopy and circular dichroism, as well as scanning tunneling microscopy are consistent with a 1:1 inclusion complex in which the phosphorus atom would be incorporated into the torus of the β-CD. NMR investigations carried out on ( m-sulfonatophenyl)diphenylphosphine have shown that a phenyl group is incorporated [55]. Thus, the phosphorus ligand could modify the association constant of the alkene with the cyclodextrin so that the mass transfer between the two phases could be decreased.
Syntheses, structures, and immobilization of ruthenium(II) complexes with alkoxysilane groups functionalized N,N′-diamine and phosphine ligands
Published in Journal of Coordination Chemistry, 2020
Jiao Ji, Li-Miao Shi, Fule Wu, Zhi-Feng Xin, Ai-Quan Jia, Qian-Feng Zhang
The organometallic ruthenium(II) complexes have a wide range of applications in homogeneous catalysis, in which ligands coordinated to a ruthenium metal center play an important role, exhibiting significant impact on catalyst efficiency, stability, and activity [1–3]. It is well known that phosphine ligands have a variety of structures due to their spatial configuration and electronic properties (strong σ-donors, as well as good π-acceptors). The typical structures of phosphine ligands are PR3 (R = alkyl, aryl, alkoxyl), which are extensively employed in the synthesis of transition metal complexes [4]. Compared with phosphine ligands, nitrogen-containing ligands have better stability for the change of the central metal atom and the strength of the coordination bonds. Moreover, the catalytic activity of the nitrogen-containing transition metal complexes in catalytic reactions could be changed by the steric effects [5–7]. To date, some transition metal complexes with phosphine and N,N′-diamine ligands have been prepared and tested in different catalytic reactions, such as silylation of arylalkynes, nitrile hydration, transfer hydrogenation of ketones, and Suzuki and Heck cross-coupling reactions [7‒11]. For example, Carniato reported a hetero-bimetallic carbonyl cluster stabilized by Ph2PCH2CH2Si(OEt)3 [12]. It was rather unusual, because normally compounds incorporating the –Si(OEt)3 or –Si(OMe)3 group are oily or waxy materials, which generally refuse to crystallize [13]. Moreover, the Si(OR)3 groups have the ability to condense with surface OH groups of inorganic supports and form the immobilizing sol–gel materials [14].
N-Heterocyclic carbene-Pd(II)-PPh3 complexes as a new highly efficient catalyst system for the Sonogashira cross-coupling reaction: Synthesis, characterization and biological activities
Published in Journal of Coordination Chemistry, 2018
L. Boubakri, L. Mansour, A. H. Harrath, I. Özdemir, S. Yaşar, N. Hamdi
Phosphine ligands have emerged as some of the most widely utilized ligands in catalysis. Phosphines are used because of their activation of a metal center toward desired reactivity. In particular, ligands including trialkylphosphines [24–26] and dialkyl(2-biphenyl)phosphines [27–29] have emerged as the most widely used. Carbene ligands have been used as well [30–34].