Type Of Phosphine Ligand Research Articles

Highly Regioselective Modular Assembly of 3-Phosphonyl Polysubstituted Pyridines through Radical Cascade Cyclization of 1,5-Enynes with Phosphine Oxide by Photoinitiation.

A series of 3-phosphonyl polysubstituted pyridine were first synthesized by photocatalysis, combining a phosphonyl radical cascade reaction, Boc deprotection, and aromatization. This strategy can avoid the difficulties of activating the C3-H bond on pyridine to synthesize 3-phosphonylpyridine under mild conditions. Furthermore, by constructing different enynes, we can achieve the metal-free modular synthesis of 3-phosphonyl polysubstituted pyridine, which will be transferred into a new type of phosphine ligand. This is of significance for organometallic catalysis. The regioselective control and detailed reaction mechanism of the cascade reaction are explained by DFT calculations.

Phosphinofulvene Enolate Ligands in Ruthenium Complexes by Ferrocene Photolysis under Solar Radiation

Ruthenium complexes containing a new type of phosphine ligand were obtained through photochemical transformations. The process involves the irradiation of (phosphinoferrocenylcarbonyl)ruthenium derivatives with visible light (tungsten halogen lamp) to yield complexes with κ2‐P,O phosphinofulvene enolate ligands after the formal loss of the “CpFe+” (Cp = cyclopentadienyl) entity. A tandem reaction that involves the irradiation of a mixture of a (hydroxymethyl)ferrocenylphosphine ligand and (arene)ruthenium precursors is also possible. The reaction proceeds through the coordination of the hydroxy phosphine ligands, evolution to hydrido ketone (or hydrido aldehyde) complexes and subsequent evolution to the fulvene derivatives. The process also occurs under solar radiation. The photolysis reaction was studied at different wavelengths of the visible spectrum by irradiation with light‐emitting diodes (LEDs). Positive results were obtained when irradiation was performed in the wavelength region corresponding to the metal‐to‐ligand charge‐transfer (MLCT) band that is characteristic of the acylferrocenyl moiety. The use of green light (λ = 530 nm) gave the best results, and the reaction did not proceed under higher‐wavelength light or in the dark. A non‐coordinated phosphinoferrocenylcarbaldehyde ligand also evolved under solar radiation, but a complex mixture was obtained; thus, the selectivity increases significantly if the ruthenium centre is present.

Investigation of the Thermal Properties of a Series of Copper Selenide Cluster Molecules

The thermal properties of a series of the six copper selenide cluster molecules [Cu26Se13(PEt2R)14] (R = Ph, Et), [Cu44Se22(PEt2Ph)18], [Cu70Se35(PEt2R)23] (R = Ph, Et) and [Cu140Se70(PEt3)34] have been investigated along with a characterization of their thermolysis products. For all cluster molecules the phosphine ligand shells are cleaved at temperatures between 60°C and 200°C depending on the experimental conditions (Helium gas flow or vacuum), the type of phosphine ligand and the size of the cluster molecules. The residues of the thermal treatment to 150°C were found to be nanostructured Cu2Se with crystallite sizes of approximately 12–16 nm which means that the 1–2.5 nm sized cluster cores of the precursor cluster molecules simultaneously grow during this process. A mixture of processes and factors including the strength of the Cu–P bond, the boiling point of the phosphine ligand as well as the thermal stability of the copper selenide clusters against formation of the bulk material determine the shape of the TGA curves. We found some indications in the TGA along with differential scanning calorimetry (DSC), which suggest that the cleavage of the phosphine ligands is probably mostly determined by the tendency of the metastable clusters to form the bulk material meaning their thermodynamic stability and not by the strength of the Cu–P bond. The data for the series of PEt3 ligated clusters reveal that this stability is dependent on the size of the cluster molecules.

Oxidative Addition of N‐Halosuccinimides to Palladium(0): The Discovery of Neutral Palladium(II) Imidate Complexes, which Enhance Stille Coupling of Allylic and Benzylic Halides.

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Oxidative addition of N-halosuccinimides to palladium(0): the discovery of neutral palladium(II) imidate complexes, which enhance Stille coupling of allylic and benzylic halides

The Stille coupling of organostannanes and organohalides, mediated by air and moisture stable palladium(II) phosphine complexes containing succinimide or phthalimide (imidate) ligands, has been investigated. An efficient synthetic route to several palladium(II) complexes containing succinimide and phthalimide ligands, has been developed. cis-Bromobis(triphenylphosphine)( N-succinimide)palladium(II) [(Ph 3P) 2Pd( N-Succ)Br] is shown to mediate the Stille coupling of allylic and benzylic halides with alkenyl, aryl and allyl stannanes. In competition experiments between 4-nitrobromobenzene and benzyl bromide with a cis-stannylvinyl ester, (Ph 3P) 2Pd( N-Succ)Br preferentially cross-couples benzyl bromide, whereas with other commonly employed precatalysts 4-nitrobromobenzene undergoes preferential cross-coupling. Furthermore, preferential reaction of deactivated benzyl bromides over activated benzyl bromides is observed for the first time. The type of halide and presence of a succinimide ligand are essential for effective Stille coupling. The type of phosphine ligand is also shown to alter the catalytic activity of palladium(II) succinimide complexes.

Antitumor activity of the mixed phosphine gold species chlorotriphenylphosphine-1,3-bis(diphenylphosphino)propanegold(I).

The title compound has been designed for antitumor activity based on structural features of related known antitumor gold agents, that is, gold-monophosphine and gold-diphosphine derivatives. It is a gold complex that contains both types of phosphine ligands, thus suggesting a possible synergistic action. The results of a single crystal X-ray structure determination of this molecule show the metal surrounded by 3 P atoms and one Cl anion in a distorted tetrahedral arrangement. The chloro anion, however, is weakly bound to the metal and so the species shows ionic character. The P NMR study, performed in solution, confirms the structural features observed in the solid and, in addition, indicates partial formation of other known gold(I)-diphosphine antitumor agents. The ionic character and strong Au-P bonds of this novel gold(I) species are similar to those of the most active antitumor gold compounds so far studied. The former feature contributes to solubility in biological fluids, and the latter prevents fast biomolecular attack. In addition, the title compound is less lipophilic, a feature recently correlated to lower liver toxicity. The title compound shows in vitro antitumor activity in the two initial National Cancer Institute protocols against human tumors. In the first screening, a unique dose (0.10 mM) of the title compound reduced cell growth of MCF7 (breast cancer), NCI-H460 (lung cancer), and SF-268 (Central Nervous System cancer-CNS) to 5, 8, and 11%, respectively. In the second protocol a 60-cell line panel was analyzed with the title compound concentration in the 0.1 mM-0.01 microM range. The highest activity was for the breast tumor cell line MCF7 with a LC(50) less than 0.01 microM. LC(50) values in the micromolar range were obtained for 29 cell lines. With the exception of leukemia, these micromolar activities were observed in at least one cell line for each subgroup tumor (non small lung, colon, CNS, melanoma, renal, prostate, breast, and ovarian). The leukemia inactivity was unexpected, as all antitumor gold(I) phosphine compounds in the literature described thus far are active. Melanoma was the most sensitive subgroup screened (five out of seven cell lines).

Novel nickel(II) and cobalt(II) catalysts based on poly-salen type ligands for the dimerization of propylene

A series of poly-salen type Ni(II) and Co(II) complexes were prepared, and the catalytic behavior in the dimerization of propylene has been studied in combination with aluminum co-catalysts and phosphine ligands. The effects of various reaction factors, such as the type of phosphine ligand and the P/Ni ratio, the type of aluminum co-catalyst and its quantity, particularly the nature of the nickel and cobalt complexes, were also examined. The results indicated that the productivity of the catalytic system was strongly dependent on the steric character of poly-salen ligand in the Ni(H) and Co(II) complexes. It was also found that reaction temperature deeply affected the performance of the catalytic system in the presence of phosphine ligand and alkyl aluminum promoter, and higher regioselectivities to 2,3-dimethylbutenes (2,3DMB) in the dimers were observed with incorporation of bulky and basic PCy3 into the nickel and cobalt catalysts. An extremely high activity in the propylene dimerization (TOF up to 221,000 h(-1)) was obtained with the 2b system under suitable conditions, which was much higher than that obtained with the corresponding monomeric salen system. However, it seemed difficult to realize recycling of the catalysts owing to the restrict dependence of catalytic activity with its solubility, at least under the adopted conditions. (C) 2002 Elsevier Science B.V. All rights reserved.

Transition Metal Phosphine Complexes Possessing Phase Transfer Function. Preparation and Reactivities of Palladium Complexes Containing Quaternary Ammonium Groups

Abstract A new type of phosphine ligands (L) bearing quaternary ammonium as a functional group was synthesized. Their palladium complexes, PdBr2L2, readily underwent halogen exchange with powdered NaI under two-phase conditions, and efficiently catalyzed the fluorocarbonylation of phenyl bromide with powdered KF at atmospheric pressure of CO.

Functional trimethylphosphine derivatives. 23. (Phosphinomethyl)aluminum compounds: (phosphinomethyl)aluminates as a novel type of phosphine ligand and x-ray structures of [(TMEDA)(THF)Li(Me2PCH2)AlMe3] and [(TMEDA)Li(Me2PCH2)2AlMe2

Functional trimethylphosphine derivatives. 23. (Phosphinomethyl)aluminum compounds: (phosphinomethyl)aluminates as a novel type of phosphine ligand and x-ray structures of [(TMEDA)(THF)Li(Me2PCH2)AlMe3] and [(TMEDA)Li(Me2PCH2)2AlMe2