Catalysts, homogeneous ligand types

Lanthanide-based catalysts, despite finding a lot of application in homogeneous catalysis, can be rather problematic due to the lability of some ligand types and the versatility of their coordination chemistry in the -1-3 oxidation state this makes the controlled synthesis of single-site Ln complexes a quite ambitious goal [92]. McLain and coworkers first demonstrated the high potential of a homoleptic yttrium complex Y(OCH2CH2NMe2)3 as ROP catalyst for the preparation of PLA from rac-lactide and that it promotes a rapid and controlled polymerization... 

In addition, Buchwald has reported polymer-bound versions of the biphenylyl dialkyl-phosphines. As shown in Chart 4, the ligand is tethered to Merrifield resin through a 2 -OH on the biphenylyl group. The scope for reactions was similar to that of homogeneous catalysts bearing these types of ligands. Catalysts were recycled four times starting with 2 mol %... 

Soon after the initial discovery of this trimerization reaction, Wilke and coworkers found that the versatility and reactivity of such catalyses is enhanced when homogeneous zerovalent nickel catalyst are being used [6b, 13]. Catalysts of this type can either be generated from Ni complexes with ligands that can easily be substituted by BD (eg., Ni[CDT], Ni[COD]2) ( naked Nickel [6b]), or from Ni complexes that are reduced in the presence of BD (almost any reducing agent will serve) [6] a typical example is [Ni(acac)2]-Al(OEt)Et2. Condensed nickel vapor has also been shown to be active [13]. 

Porphyrins and related tetrapyrrole macrocyclic ligands are one of the most prominent ligand types in coordination chemistry. Their occurrence in metallo-enzymes, their application as inorganic dyes and photosensitisers, their use as homogeneous catalysts, mainly for oxidation or oxygenation reactions, and their outstanding role in coordination chemistry is in general well documented. ... 

The homogeneous hydrogenation of functionalized carbonyl compounds gives remarkable results with catalysts of the type RUX2L (X = halide, L = atropisomeric ligands). These bis(trialkyl phosphine) ligands have a C2 axis. BINAP is their main representative. ... 

Different to the charge-positive cyclam-type systems, neutral Ni11 complexes (652) with Jager-type ligands are remarkably selective and persistent homogeneous catalysts for the electrochemical reduction of C02 to oxalate.1642... 

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