Polyamine Donors

Formation of complexes such as (51) and (52), which have a very high ionic charge and contain several metal centres, has been noted.300 

Baker and J. C. Bailar, Proceedings 16th International Conference on Chemistry of Coordination Compounds. Dublin, 1974. 

Pentaethylenehexamine (l,14-diamino-3,6,9,12-tetra-azatetradecane) reacts with [Co(NH3)5Br]Br2 in aqueous solution in the presence of active charcoal to form [CoL]C13, nH20 (in the presence of NaCl). Geometrical and optical isomers were separated by column chromatography, and structures assigned on the basis of n.m.r., absorption, i.r., and c.d. spectra.301 The structure of ( —)589-[CoL][Co(CN)6], 3H20 [L = AWIV. /V -tetrakis-(2 -aminoethyl)-l,2-diaminopropane] has been reported, and has the absolute configuration AAA.302 

The isomers of [P glycinatotriethylenetetra-aminecobaltpii)]24 have been separated by a cation-exchange resin,303 and an X-ray investigation was performed on a crystal containing both the A-( — )589-(RR) and -(RS) diastereoisomers. 

The configurations of trans-[Co(cyclam)(CN)Br]+ and trans-[Co(cyclam)(N3)Cl] + (cyclam = 1,4,8,11-tetra-azacyclotetradecane) have been assigned on the basis of i.r. and absorption spectral evidence. trans-[Co(cyclam)X(OH2)]2+ (X = CN, NCS, or 

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Arginine serves as the formamidine donor for creatine biosynthesis, participates in polyamine biosynthesis, and provides the nitrogen of nitric oxide (NO). 

Complexation of Cd with a series of polyamine macrocycles, but also related open-chain polyamines, comprising or attached to the 2,2 -bipyridine (bipy) and 1,10-phenanthroline (phen) moieties, has been studied by combined UV/vis spectrometry and potentiometry.24 Formation constants and distribution diagrams of the species present have been evaluated. As a result the thermodynamic stabilities, i.e., the formation constants, are lower for the bipy- and phen-contain-ing ligands than those for Cd complexes with aliphatic oligoaza macrocycles containing the same number of N donors. The probable reason is loss of flexibility of the ligands caused by the size and stiffness of the inserted heteroaromatic moieties. 

Other structural features that have acceleratory influences in the base hydrolysis of Co(III) systems are (i) the incorporation of a pyridine ligand in the coordination sphere and (ii) the incorporation of a flat secondary nitrogen donor system in the polyamine ligand skeleton (5) (structures C and D in Fig. 17). 

The subject matter of this chapter will be subdivided into sections concerning template synthesis of the complexes structural and thermodynamic properties of the complexes with synthetic cyclic polyamines complexes with mixed-donor macrocycles reactivity of the complexes cryptates and complexes with phthalocyanines and porphyrins. 

Nitrogen-bound diazeniumdiolates (IV-diazeniumdiolates or 1-amino-substituted diazen-l-ium-l,2-diolates) spontaneously produce NO under physiological conditions.34 This class of NO donors is synthesized by exposing polyamine precursors to high pressures of NO (Scheme 9.1). 

This polyamine has predominantly a donor character, is expected to render the coordinated metal ion electron-rich, imposes virtually no steric constraints, and may thus be construed as a chelating analogue of the pentaammine donor set (NH3)5. This contribution reviews the progress we have made in the study of pyN4 complexes, highlighting similarities and differences in the coordination chemistry of other square-pyramidal chelators along the way. 

Copper(II) polyamine complexes are substitutionally labile, in a manner similar to the corresponding nickel(II) complexes. This means that individual donor atoms may at times decoordinate and thus be available for derivatization reactions, e.g., with suitable carbonyl compounds. More complex ligands may thus be constructed, including macrocycles (35), polymacrocycles (36 38), and concave chelators (35). The copper(II) complex of 1 was synthesized as a starting material for reactions aiming at the derivatization of the pentaamine ligand (24-28). 

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