Mixed Donor Polydentate Ligands

The mixed donor polydentate ligands Pr -N(CH2CH2PPh2)2 (PNP) and Et2NCH2CH2N(CH2CH2PPh2)2 (P2N2) have been reacted with [Ir(COD)(OMe)]2 to produce complexes that were active in the reduction of PhCH=CHCOMe [39]. Conversions of 90% with modest selectivity were achieved in 2-4 h in pro-pan-2-ol at 83 °C. At 140 °C in cyclopentanol, similar results are obtained in less than 30 min. 

Mixed Donor Atom Ligands 32.4.9.1 Open polydentate ligands... 

Diverse examples of polydentate ligands that feature S-donors in concert with N-, 0-, and also P-donors have appeared. Didentate mixed donor sulhir ligands have been reviewed. 

Polydentate nitrogen donor tripod ligands are discussed in this section. Mixed donor ligands containing nitrogen donors are discussed in Section 6.8.11. 

Manganese(III) complexes with a variety of oxygen ligands comprise the largest group next to those with mixed donor set polydentate ligands. The majority of these complexes are polynuclear. 

Nickel(H) complexes with ligands containing mixed donor atoms, in general N, O and S, are innumerable. In die present section we will mention complexes which are the archetypes or are suitable for the description of the properties of all complexes of the same type. Nickel complexes with hybrid polydentate ligands containing either P or As have been discussed in Section 50.5.4. 

Mixed Donor Ligands 54.L9.1 Open polydentate species... 

The field has been the subject of several reviews of the properties, structures, and stability of numerous ligands and their complexes, including both mixed donor open-chain and macrocyclic polydentates. " Detailed reports of coordination chemistry that focus on the metal include many examples of mixed donor ligand systems. The nature of this article requires that only limited references are cited herein as examples, but these include some key reviews readers may access original work through these reviews or else by structure searching from compounds represented in line drawings that appear here. 

Central to the stability and chemistry of complexes formed by mixed donor ligands are two key concepts of coordination chemistry. The first is the chelate effect, which applies to all polydentate ligands, and reflects the increase in stability of a type of complex as monodentate donor molecnles are replaced by polydentates with donors linked by chelate rings. The hard-soft acid-base theory is particnlarly relevant to mixed donor ligands where donors of distinctly different character may bind to a central metal ion. The like prefers like concept means hard nonpolarizable donor atoms (N and O, for example) bond preferentially to hard nonpolarizable metal... 

Other polydentate and macrocyclic mixed-donor ligands 365... 

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