Ligand structures pentadentate ligands

Pentadentate ligands with N4S donors based on methyl 2-aminocyclopent-l-ene-l-dithiocar-boxylate with pendent pyrazolyl groups (113) form complexes with zinc including a structurally characterized trigonal-bipyramidal zinc compound.891... 

Scheme 1). In addition to the determination of molar conductivity, magnetic moment, and IR spectra, the complex was characterized by X-ray structural analysis (4). This indicates that the cationic complex with neutral H2dapsox is symmetrically coordinated as a pentadentate ligand. Co(II) occurs in a PBP environment with water and methanol molecules in apical positions (Fig. 1). Although the side chains are symmetrically coordinated, Co-O(eq) bond lengths differ significantly. 

In order to examine the effect of varying the charge on the pentadentate ligand on both the structure and characteristics of the produced Ni(II) complexes, the complexes [Ni(Hdapsox)(MeOH)2]C104... 

Fe2(daps)Cl2(EtOH)2] (53) have been structurally characterized (Table II). The first two represent monomeric complexes with neutral pentadentate ligands, whereas the third is a binuclear complex with tetra-deprotonated daps4- as a heptadentate ligand and two non-equivalent Fe(III) ions, one in a PBP and the other one in an octahedral environment (53). 

Since these intermediates were characterized (10) as monomeric PBP complexes of Fe(III) with a dianionic acyclic pentadentate ligand, it was the intention to isolate and structurally characterize some of them, since no examples of such structures have been reported in the literature. With this aim, the [Fe(dapsox)(H20)2]C104 complex 12 was synthesized, which is analogous to the intermediate [Fe(dapsox)Cl(H20)]. The results of an X-ray structural analysis (Fig. 6) confirmed the PBP structure of the complex and double deprotonation of the ligand. This structure is the first example of a monomeric structure of Fe(III) with an anionic pentadentate ligand and confirms previously suggested hydrolytic processes (10) which led to the production of complex 10. 

The novel pentadentate ligand (K NCI CI NHCI CXNF CHa, tamdn (l,5,9-triamino-5-methyl-3,7-diazanonane), could be shown to coordinate to cobalt(III), and the brown dicobalt peroxo- and green dicobalt superoxo-bridged dimers [(tamdn)Co(p-02)Co(tamdn)]4+/5+ could be prepared (19). An X-ray crystal structure of the superoxo species (redrawn in Fig. 2) showed the expected structure. In addition, spectroscopic studies supported an analogous structure for the peroxo species. 

Most of the complexes [NiL] given by the potentially pentadentate ligands (IX) and (X) (Table 97) are five-coordinate high-spin and possess an essentially trigonal bipyramidal structure (320).2320-2322 In contrast with the aforementioned complexes, those formed by the ligands (VIII) which possess the less flexible ethylene bridging chain are essentially square planar.2313,2318... 

Noteworthy are the complexes obtained with the pentadentate ligands derived from the condensation of 2,6-diacetylpyridine with various substituted hydrazines (XI Table 98). These complexes have been found to be seven-coordinate with pentagonal bipyramidal structure where the pentadentate ligand invariably has its five donor atoms in the equatorial plane. The two residual coordination sites in the axial positions are occupied by two water molecules (325).2361-2364... 

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