Nitrogen based ligands for

The most common catalysts for ATRP are complexes based on a copper(T) halide and nitrogen based ligand(s). Various ligands have been employed and those most frequently encountered are summarized in Table 9.5. Typically, four nitrogens coordinate to copper. The bidentate bipyridyl (bpy) ligands 132-133 are known to form a 2 1 complex. The tetradentate ligands are expected to form a 1 1 complex. 

Table 1 Structural parameters for Cu11 complexes with nitrogen-based ligands...

For many years nitrogen-based ligands were the ligands of choice for the asymmetric hydrosilylation of ketones and especially pyridincoxazolincs were highly effective [25], In Figure 18.14 a few typical examples have been collected. 

Here, I focus on application of ruthenium complexes as catalysts for the cyclopropanation of olefins with diazoesters to describe their catalytic activity, stereoselectivity, and enantioselectivity together with structural analysis of intermediary carbene complexes, especially with nitrogen-based ligands including porphyrin derivatives [4,5]. 

In the cupric ion-catalyzed reaction of primary aromatic diamines with oxygen four key steps can be recognized (shown for a monoamine with nitrogen base ligands left out for convenience) ... 

Brookhart and co-workers [79-81] introduced catalysts based largely on chelating, nitrogen-based ligands that are active for the homopolymerization of ethylene and the copolymerization of ethylene with 1-olefins and polar comonomers (31). Ni, Co, Fe or Pd are used as late transition metals. The diimine ligands have big substituents to prevent 6-hydride elimination. Ni(II) or Pd(II) complexes form cations by combination with MAO and polymerize ethylene to highly branched polymers with molecular weights up to one million. The activities reach TON... 

If we use iron(II) porphyrins without facial protection as models of the active site of hemoproteins, the five-coordinate state does not form. Addition of aromatic, nitrogen-based ligands in a noncoordinating solvent preferentially gives symmetrical six-coordinate complexes. The formation of such complexes, called hemochromes, is favored over pentacoordination because the equilibrium constant is greater for the addition of the second ligand (Xg) than for the first (ASb)... 

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