Late-metal catalysts for ethylene homo- and copolymerization.

Iron Catalysis in Organic Synthesis

Precise control of polyolefin stereochemistry using single-site metal catalysts.

Surface functionalization of nano-magnetic nanoparticles is a well-designed way to bridge the gap between heterogeneous and homogeneous catalysis. The introduction of magnetic nanoparticles (MNPs) in a variety of solid matrices allows the combination of well-known procedures for catalyst heterogenization with techniques for magnetic separation. Magnetite is a well-known material, also known as ferrite (Fe3O4), and can be used as a versatile support for functionalization of metals, organocatalysts, N-heterocyclic carbenes, and chiral catalysts. It is used as a support for important homogeneous catalytically active metals such as Pd, Pt, Cu, Ni, Co, Ir, etc. to obtain stable and magnetically recyclable heterogeneous catalysts. Homogeneous organocatalysts can be successfully decorated with linkers/ligands on the surface of magnetite or alternatively the organocatalysts can be directly immobilized on the surface of magnetite. The functionalized magnetically retrievable catalysts or nanocatalysts that are increasingly being used in catalysis, green chemistry and pharmaceutically significant reactions are summarized in this review.

Nano-magnetite (Fe3O4) as a support for recyclable catalysts in the development of sustainable methodologies

2.3. [4 + 4] Cycloadditions 1058 2.4. Photocycloadditions of Aromatic Compounds 1058 2.4.1. Benzene Derivatives 1058 2.4.2. Condensed Aromatic Compounds 1060 3. Photochemical Rearrangements 1061 4. Cyclizations 1064 4.1. Pericyclizations 1064 4.2. Norrish−Yang Reaction 1066 5. Photochemical Extrusion of Small Molecules 1067 6. Photochemical Electron Transfer 1068 6.1. Photochemical Electron-Transfer Reactions with a Catalytic Sensitizer 1068

Photochemical Reactions as Key Steps in Organic Synthesis

The catalytic reductive amidation of an al- dehyde (hexanal) with an amide (acetamide) is re- ported. Apart from the desired N-hexylacetamide, the two isomeric unsaturated intermediates as well as hexanol are produced together with higher mass products that arise from aldol condensation and di- A coupling of the aldehyde. Screening of differ- ent catalyst precursor salts, ligands and reaction con- ditions led to the finding that the catalytic system based on the (cyclooctadiene)rhodium chloride dimer, (RhA2, in combination with the ligand xantphos and an acid co-catalyst results in high selec- tivity for the desired product. Under optimized con- ditions nearly full conversion is reached with high se- lectivity to the desired N-alkylamide and with a very high N-alkylamide/alcohol ratio, while producing only small amounts of by-products. The scope of the reaction has been investigated using different amides as well as aldehydes; the results show the general ap- plicability of this novel reaction, but with electron- withdrawing amides the selectivity to N-alkylamide is lower. NMR studies showed that the nucleophilic addition of acetamide to hexanal is acid catalyzed, forming N-(1-hydroxyhexyl)acetamide in equilibrium with both hexanal and the dehydrated unsaturated imides. A catalytic mechanism is proposed in which a strong acid such as HOTs acts as a co-catalyst by establishing a rapid chemical equilibrium between the aldehyde, acetamide and the intermediates. Fur- thermore, it is proposed that the presence of acid causes a change in catalytic species, enabling a cation- ic Rh/xantphos hydrogenation catalyst to selectively hydrogenate the intermediates to N-hexylacetamide in the presence of hexanal.

Rhodium-Catalyzed Homogeneous Reductive Amidation of Aldehydes

Structure, Dynamic Behavior, and Catalytic Activity of a Novel Ruthenium Cyclopentadienyl Complex with a Tridentate P,P,O Ligand

The synthetic pathways towards Pd-II complexes of functionalized bidentate diphenylphosphane ligands of the type [Pd(ligand)(anion)(2)] and [Pd(ligand)(2)](anion)(2) have been investigated. Eighteen different ligands have been used in combination with strongly (acetate, OAc-) or weakly (tosylate, OTs-) coordinating anions, The solid-state structure of some representative complexes was determined with X-ray crystallography. It is shown that the solid-state structures are fully retained in solution, The formation of [Pd(ligand)-(anion)(2)]-type complexes was studied in detail by H-1- and P-31-NMR spectroscopy. Depending on the Ligand structure, the complex is formed instantaneously, via a polynuclear intermediate or is not formed at all. Complex formation is demonstrated to depend on the length and rigidity of the ligand backbone and on the steric bulk at the ortho position of the phenyl rings on phosphorus, It was also found that the coordinating ability of the anions can alter the structure of the kinetic and/or thermodynamic product.

NMR Spectroscopic Studies of Palladium(II) Complexes of Bidentate Diphenylphosphane Ligands with Acetate and Tosylate Anions: Complex Formation and Structures

Remarkable activity of the isomerization catalyst [RuCp(PPh3)2](OTs) in O-allylation of phenol with allyl alcohol

Several palladium complexes with bidentate phosphine ligands were tested for their activity in the O-allylation of phenols with allyl alcohol. The use of C3-bridged bidentate phosphine ligands results in very high selectivity for O-allylation. The reactions do not require stoichiometric amounts of additives to control the chemoselectivity. Especially, catalysts with gem-dialkyl substituted C3-bridged bidentate phosphine ligands perform very well, resulting in a (equilibrium) conversion of ∼50% of phenol with a selectivity of 99% for O-allylation. The use of diallyl ether as the allylating agent results in a significant increase in phenol conversion while maintaining high selectivity for O-allylation. Apart from Pd(OAc)2 as catalyst precursor, Pd(dba)2 was also employed, making it possible to use other types of phosphine or phosphite ligands. With the palladium catalytic system not only phenol, but also aliphatic alcohols can be allylated, as well as aromatic and aliphatic amines.

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Papers

Rhodium-Catalyzed Homogeneous Reductive Amidation of Aldehydes

Structure, Dynamic Behavior, and Catalytic Activity of a Novel Ruthenium Cyclopentadienyl Complex with a Tridentate P,P,O Ligand

NMR Spectroscopic Studies of Palladium(II) Complexes of Bidentate Diphenylphosphane Ligands with Acetate and Tosylate Anions: Complex Formation and Structures

Remarkable activity of the isomerization catalyst [RuCp(PPh3)2](OTs) in O-allylation of phenol with allyl alcohol

Palladium–diphosphine complexes as catalysts for allylations with allyl alcohol