Stereochemistry of Four-coordinate Chelate Compounds of Schiff Bases and Their Analogues

Abstract

The problem of the configuration of the chelate group and the metal ring in chelates of transition metals with Schiff bases and their analogues is discussed, and the influence of various factors analysed, in particular the nature of the central metal atom and the steric and electronic effects of the ligands. Various types of conformational changes in conjugated metal rings in bicyclic and tricyclic chelates are surveyed, and factors influencing these changes are noted. The conformation of the non-conjugated metal rings in tricyclic chelates is discussed. A list of 188 references is included.

Bis(2-{[5-fluoro-2-(trifluoromethyl)phenyl]iminomethyl}phenolato-κ2N,O)copper(II)

“…There has been continuing interest in bis-bidentate Schiff base Cu(II) complexes because the ligands display a wide range of geometric arrangements in the solid state, from ideal transsquare-planar to deformed tetrahedral (Bluhm et al, 2003;(Lacroix et al, 2004). In investigations of these complexes based on bis-bidentate Schiff base ligands, both electronic effects (Maslen et al, 1975) and crystal packing (Panova et al, 1980) have been invoked as the driving forces responsible for the distortion. In this paper, we report the synthesis and crystal structure of the title complex, (I).…”

Rational design of metal coordination compounds with azomethine ligands

“…44 ± 48 Complexes with Schiff bases of 2-formylpyrrole 13 5, 12, 20, 21, 49 ± 55 and 2-formylbenzimidazole 14 43, 56 ± 60 studied earlier belong to azomethine complexes containing the fivemembered MN 4 coordination unit. It should be emphasised that chelates of type 13 were generated under the conditions of chemical 5,12,20,21 and electrochemical 49 ± 55 syntheses, whereas chelates 14 were prepared only by the electrochemical method 56 ± 60 because of the rather low acidity of the N7H bond in benzimidazole. This approach was also employed in the synthesis of chelate compounds 15 and 16 with the use of pyrrolebased aldimine ligands possessing nitrogen-55 or sulfur-containing 61 fragments.…”

“…Such ligand systems are involved in complexes 91 ± 94. 12,24 Salicylaldehyde-based azomethine complexes have been studied for many years. 12,173 In these complexes, additional coordination can occur through the dimethylaminoalkyl substituents.…”

“…12,24 Salicylaldehyde-based azomethine complexes have been studied for many years. 12,173 In these complexes, additional coordination can occur through the dimethylaminoalkyl substituents. For example, a ligand of this type is present in the structurally characterised manganese chelate 95.…”

{4,6-Dichloro-2-[(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)iminomethyl]phenolato-κ2N,O}copper(II)

“…There has been continuous interest in bis-bidentate Schiff base Cu II complexes because, in the solid state, the ligands display a wide range of geometric arrangements around copper, from ideal trans-square-planar to deformed tetrahedral geometry (Bluhm et al, 2003;Lacroix et al, 2004). In investigations of these complexes based on bis-bidentate Schiff base ligands, both electronic effects (Maslen & Waters, 1975) and crystal packing (Panova et al, 1980) have been invoked as the driving forces responsible for the distortion. In this paper, we report the synthesis and crystal structure of the title complex, (I).…”