Pyridyl-type ligands

A ruthenium(IV) 0x0 complex containing pyridyl-type ligands, [Ru (0)(N40)l (see Figure 14 for structures of ligand), has been generated by electrochemical oxidation of [Ru (N40)(0H2)] in aqueous solution (pH > 3.5). This species was found to disproportionate to Ru" and Ru in acidic solution." ... 

Metal ions such as Rh(III), Ir(III), Pd(II), Pt(II) and Pt(IV) may be used, although pyridyl-type ligands are less appropriate in these cases since they do not provide the required orbital energy levels. In such cases, combinations of pyridyl and N—C carbanion ligands, such as deprotonated 2-phenylpyridine, are beginning to prove useful. 

Linear multinuclear metal complexes are attracting attention in the context of molecular electronics due to their projected use as molecular wires. 01igo(pyridyl)amido ligands are efficient scaffolds for lining up several Ni11 ions like a string. The first structurally characterized trinickel complex of this type, [Ni3(dpa)4Cl2] (dpa = bis(2-pyridyl)amide), showed a nearly linear Ni3 unit with Ni—Ni distances of around 244 pm.209 Penta-, hepta-, and nonanuclear systems have... 

Pyridyl-containing ligands have already been discussed but the large body of work involving bipyridyl type ligands is represented here. Bipyridine and polybipyridine ligands in particular have found application with zinc in the formation of supramolecular structures and examples will be mentioned in Section 6.8.4.9. 

Another type of tri-imine complexes containing terpyridyl type ligands, in which the inner pyridyl ring has been replaced by an amino moiety, such as di-(2-pyridylmethyl)-amine (dpma) and di-(2-pyridylmethyl)methylamine (medpma) has been described... 

The surface adsorbing groups, X, are most satisfactory when they belong to a-donor and 7r-acceptor synergic-type ligands such as 4-pyridyl-N, thio-SH, disulfide S-S, and phosphine P, which are appropriate for coordination to a Group 11 metal such as Au. 

Dinucleating tpa-type ligand (282) tpa = tris(2-pyridyl-methyl)amine. 

Transition metal catalysts encapsulated within the ligand-template nanoreactor G, P(Py)s [ZnJs, have been applied to catalyze industrially relevant processes such as hydroformylation and Heck reaction. Nanoreactor [G 3 Rh(CO)(acac)] encapsulates a Rh-species that contains only one tris(meta-pyridyl)phosphine ligand, P(m-Py)3, surrounded by three Zn-porphyrins or Zn-salphens. Under syngas pressure (H2/CO), rhodium species like Rh(CO)(acac)P(Py)3 transform into a complex of type HRh(CO)3P(Py)3, which is the active species for the hydroformylation reaction, hi this reaction terminal alkenes are converted into linear and/or branched aldehydes, and the ratio of these products strongly depends on the specific catalyst applied. Hydroformylation of 1-octene by encapsulated rhodium, [G 3 HRh(CO)3], resulted in a 10-fold rate enhancanent compared... 

More recently, platinum complexes containing pyridyl type of ligands have been used to afford polyynes (Fig 8.38) [69]. 

Costas and coworkers have shown recently that manganese complexes based on BPMEN-type ligands (where BPMEN is bis((pyridin-2-yl)methyl)ethylene-l,2-diamine, Figure 11.11) show enhanced activity in the epoxidation of alkenes with H2O2 in the presence of excess acetic add, albeit with lower activity and with a narrower substrate scope than for the pyridyl-tmtacn based systems reported in the same study (see above. Table 11.7) [102]. 

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