Tetra-amido ligands

FIGURE 3.12 Tetra-amido ligands and nonheme iron(IV) oxo synthetic complexes. 

Chemical structure of a tetra amido macrocyclic ligand... 

A large number of structurally characterized bis(trimethylsilyl)amido complexes now exist Table 5 gives a representative selection of monometallic homoleptic compounds, both base-free and with coordinated ethers. Other examples are known with coordinated fiuorobenzenes, isonitriles,methylated pyridines, various amines (TMEDA, PMDTA, TMPDA (Tetra-methylpropylenediamine), BzNMe2 (benzyldimethylamine)), Ph PO, (Bu"0)(Pr )C0, and l,3-(Pr )2-3,4,5,6-tetrahydropyrimid-2-ylidene. Their structures illustrate the complex interactions between metal size, ligand bulk, and molecular structure that exist with these metals. For example, among the alkali metal base-free species, the unsolvated Li derivative crystallizes as a cyclic trimer, whereas the Na salt is found both as a trimer " and as infinite chains of [Na-N(SiMe3)2—] units. The potassium, rubidium, and caesium derivatives exist as discrete dimers in the solid state, constructed around planar [M—N-]2 frameworks. 

Sykes and his co-workers have made a detailed study of the metalion reduction of ju.-amido-/a-(ligand)-bis[tetra-amminecobalt(m)] complexes where ligand = sulphato, selenato, phosphato, oxalato, and... 

In a different approach to the design of a two-electron redox system, we appended the ferrocene firagment to a tetra-aza macrocode (a further example of an LrX system) the functionalized ligand should incorporate a d metal centre and should promote its redox activity. The tetra-aza macrocycle we have chosen is dioxocyclam, 9. This ligand, which can be prepared throu reaction of diethylmalonate with 2.3.2-tet, on addition of 2 eqmvalents of a strong base incorporates in aqueous solution a Cu ion, with simtdtaneous extrusion of two protons from the two amido groups [19]. 

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