Pyridonate ligands

A review of dinuclear complexes of Ir1 bridged via 2-pyridone ligands (N/O donor atoms), by Rawson and Winpenny, has been published in 1995.673... 

The coordination behavior as well as the tautomerization equilibria of the new pyridone ligands was studied in detail by NMR and computational methods. For all three the data obtained strongly support a pseudo-bidentate hydroxypyridine-pyridone binding mode. 

Since the two tautomers - the hydroxypyridine 1A and the pyridone IB - equilibrate rapidly, mixing of two pyridone ligands with different donor sites would afford... 

The work on dinuclear complexes with two bridging oe-pyridone ligands, has been carried out mainly by two research groups, i.e., those led by Cotton and Lippard. 

A hexanuclear cobalt(II) metallocrown has been reported by Thornton and co-workers 166). Reaction of Na(OMe) with cobalt(II) acetate and Hmhp in MeOH apparently gives [Co6Na(mhp)i2]" ", and anion was not located in a highly disordered crystal structure. A 5deld is not reported, and crystallization required a period of months. The structure contains six tetrahedral Co(ll) centers, each bound to two N and two O donors from pyridonate ligands. Six of these oxygen atoms lie within the metallocycle, and form an ideal cavity for coordination of sodium. 

The only homoleptic cage described above is [Copfchpjig] 45, and therefore one might conclude that, in the absence of other influences, pyridonates favour structures based on tetrahedra. However, structures featuring pyridonates are found in virtually all the categories, chiefly due to the coordinative flexibility of the ligands. There is also a marked difference between the coordination chemistry of the 6-chloro- and 6-methyl-2-pyridonate ligands, due to electronic factors which influence the coordi-... 

Bis(pyridonate) zirconium complex 14, bearing sterically demanding pyridonate ligands, can be synthesized via protonolysis (Scheme 15), and is an active precatalyst for the intramolecular hydroamination of aminoalkenes to generate pyrrolidine and... 

Figure 17 The structure of [Coi3(chp)2o(phth)2(OH)2] with all C atoms of pyridonate ligands except C2 removed for clarity (shading Co, hatched O, open N, striped C, lines).

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