Phenylpyridine ligands

Figure 9.22 DTA-TGA trace for Ni(NCS)2(4-Phpy)4 4C6H6 showing the endothemic loss first of benzene and then the 4-phenylpyridine ligands in two distinct stages. (Reprinted with permission from IUCr).

It is important to note that the electronic effects in this system are complicated by the fact that there are two different carboxylate ligands and two different arylpyridine ligands, each of which plays a different role in the C-O bond-forming process. However, overall, the data are consistent with a transition state like 21 or 22 for this transformation (Eq. 21). Notably, reductive elimination could also occur with the other (inequivalent) phenylpyridine ligand. 

Solution processable cyclotriphosphazene OLEDs can be formed through direct substitution at phosphorus Polyaromatic substituted phosphazene (2) has one pendant group containing nitrogen for potential complexation with a metal. In this example, two 2-phenylpyridine ligands are complexed to the iridium metal center. 

Au( N) CI3 adducts are readily obtained by reaction of AU2CI6 or [ AuCU] with a variety of substituted heterocyclic ligands including 2-phenylpyridine [9], 2-benzylpyridines [10],... 

D., Yang, C.-T, Ranford, J.D., Vittal, J.J. and Lee, P.F. (2003) Synthesis, characterization, and biological activities of 2-phenylpyridine gold(lll) complexes with thiolate ligands. Dalton Transactions, (17), 3376. 

The most frequently reported mixed C/N-donor ligands are the 2-phenylpyridine anion, ppy (170), orthometalated 2,2 -bipyridine, C3N bpy (171), and derivatives, for example (172). 

Scheme 7 TTF-based molecules that contain the C-deprotonated-2-phenylpyridine (ppy) ligand...

The photoactive ligands can be phenylpyridines, quinoline derivatives, or benzimidazoles and the ancillary ligand can be selected from the following structures in addition to the photoactive ligand itself (Scheme 3.78) [291]. 

A broad range of metal centers have been used for the complexation of functional ligands, including beryllium [37], zinc, transition metals such as iridium [38], and the lanthanide metals introduced by Kido [39], especially europium and terbium. Common ligands are phenanthroline (phen), bathophenanthrolin (bath), 2-phenylpyridine (ppy), acetylacetonate (acac), dibenzoylmethanate (dbm), and 11 thenoyltrifluoroacetonate (TTFA). A frequently used complex is the volatile Eu(TTFA)3(phen), 66 [40]. 

Comparisons between the electronic structures (using a ZINDO analysis) of [Ru(bpy)3] " and [Ru(bpy)(NH3)4], and between related pairs of compounds where bpy is replaced by 2,2 -bipyrazine or 1,2-benzoquinonediimine, show that bpy is unable to accept extra electron density from the metal center whereas the opposite is true for 1,2-benzoquinonediimine. The acceptor properties of the 2,2 -bipyrazine ligand fall between those of bpy and 1,2-benzoquinonediimine. Using the Fenske-Hall method, the electronic structures of [Ru(bpy)3 (ppy) ] "A (Hppy = 2-phenylpyridine) have been investigated. The coordinated ppy is a C,A-donor. The electronic structures of the heteroleptic complexes exhibit a separation of the Ru—C and Ru—N f7-bonding character. It is proposed that the observed preference for cis- over trans- and for fac- over nrer-isomers may arise from the enhanced cr-donating ability of the C atom when it is trans to an N rather than C-donor. ... 

These catalysts, 11-13, show good enantioselectivity ranging from 80 to 95% ee in the epoxidation of conjugated cfs-di- and tri-substituted olefins. Epoxidation of "good substrates such as 2,2-dimethylchromene derivatives proceeds with excellent enantioselectivity (>95% ee). Since the results obtained with these first-generation Mn-salen catalysts have been reviewed [21,33], only typical examples are shown in Table 6B.1. These reactions are usually carried out in the presence of donor ligand [34] such as 4-phenylpyridine A -oxide with terminal oxidants such as iodosylbenzene and sodium hypochlorite as described above. However, the use of some other terminal oxidants under well-optimized conditions expands the scope of the Mn-salen-... 

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