Ligand structures tetradentate ligands

Mixed N,S,0 donor sets are useful to compare the coordination ability and the structural consequences of various donor sets and to induce a variety of structural properties. The solid-state structures of [Ni(pyzs)]BF4, [Ni(pyrs)]BF4 and [Ni(pyzo)]BF4 containing dissymetric tetradentate ligands with N2S2 (543) and N2SO (544) donor sets are square planar.1397 The phenolate-based complexes are essentially planar in nitromethane, but distorted octahedral in methanol, while thiophenolate-containing complexes remain square planar in both solvents. 

In a major breakthrough, Suzuki and co-workers29 demonstrated that a tetradentate ligand produced the bis -oxojdicopper II) complex (4) (each copper ion has a square planar structure,... 

In order to construct new types of binding and activating models of dioxygen molecules, Jitsukawa, Masuda and their co-workers have synthesized a novel group of tripodal tetradentate ligands and successfully utilized them in the formation of mononuclear copper(II) complexes with novel structural features (complexes (473)-(488)).395-403 This group of ligands has four... 

A tetradentate ligand 2- bis[2-(2-pyridyl)ethyl]aminomethyl phenolate complexes zinc with an N30 donor set including pyridyl and phenolic groups. The X-ray structure reveals that a dimeric... 

In the bifunctional radiopharmaceuticals, Tc and Re complexes that are suitable for coupling to antibodies are almost square-pyramidal oxo complexes of tetradentate ligands, as mentioned earlier. Spies et al. [65] recently studied the syntheses and structures of rhenium complexes with a tetradentate NS3 tripod ligand 2, 2,, 2"-nitrilotris(ethanethiol) (l in Fig. 9) as an interesting alternative to the oxo complex. Such ligands could lead to weakly polar, trigonal-bipyramidal complexes in which the metal atom is more strongly shielded than in the square-pyramidal oxo complexes. Schemes for the syntheses... 

Using a tetradentate ligand, Rees and Moreno have proposed the first example of a monomeric barium bis-alkoxide (26). The proposed solution structure (Fig. 2) was determined based on ciyoscopic and spectroscopic data. One notable characteristic of this monomeric barium alkoxide is that it is an ambient temperature liquid. Although the compound exists as a monomer in the solution state, oligomeric species prevail in the absence of solvent. This phenomenon has been ob-... 

About twenty years ago we reported on the di-isothiocyanato iron(II) complex of the tetradentate ligand tpa (tris(2-pyridylmethyl)amine) [7] (6). It was shown that this complex exhibits the spin crossover phenomenon with a critical temperature Tm of about 170 K. Several different solvated phases of the same system have since been characterized by Chansou et al. [8]. The unsolvated phase which can be isolated from an aqueous solution has been investigated by nuclear forward scattering (NFS), nuclear inelastic scattering (NIS) [9], extended x-ray absorption fine structure (EXAFS) spectroscopy, conventional Mossbauer spectroscopy, and by measurements of the magnetic susceptibility (SQUID) [10-13]. The various measurements consistently show that the transition is complete and abrupt and it exhibits a hysteresis loop between 102 and 110 K. 

Kruger, H.-J., Peng, G. and Holm, R. H. (1991) Low-potential nickel(III,II) complexes - new systems based on tetradentate amidate thiolate ligands and the influence of ligand structure on potentials in relation to the nickel site in [NiFe]-hydrogenases. Inorg. Chem., 30, 734-42. 

Two five-coordinate Mn =0 complexes with N2O2 tetradentate ligands Ph4P[MnOL] (L= 1,2-bis(2-methyl-2-oxypropanamido)benzene and 1,2-bis(2,2-diphenyl-2-hydroxyethanamido)benzene) have been prepared and structurally characterized (12) and (13), respectively.These complexes and the 0x0 complexes discussed in the next section may have utility in oxo-transfer reactions to organic substrates such as olefins and ethers. 

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