Macrocyclic ligands phosphorus-containing

Based on donor atom type, macrocyclic ligands can be considered to span two extreme types. First there are those systems which chiefly contain nitrogen, sulfur, phosphorus, and/or arsenic donors. These macrocycles tend to have considerable affinity for transition and other heavy metal ions they usually show much less tendency to form stable complexes with ions of the alkali and alkaline earth metals. The present discussion will be restricted to a consideration of a selection of such ligands and their complexes. 

Phosphorus-containing macrocycles, 990, 996, 998 macrocychc effect, 1002 ring size, 1003 stereochemistry, 1003 Phosphorus heterocycles transition metal complexes, 1041 Phosphorus ligands, 989-1061 ir-acid series, 1033 bonding, 1030-1041 cone angle concept, 1012 trigonal bipyramidal complexes, 1036 Phosphorus oxychloride metal complexes, 500 Phosphorus ylides transition metal complexes, 1056 Phosphorylation biological, 978 Phosvitin, 975 Photochromism... 

Phosphorus-containing macrocycles have not proved to be popnlar ligands owing, in part, to their difficult multistage synthesis. We arbitrarily define phosphorus macrocycles as those with 10 or more ring members, at least one of which is phosphorus. It should be noted that the usual purpose of... 

The basic pathways for the synthesis of phosphorus-containing macrocyclic substances are high dilution techniques and template reactions. The use of the template route enables the assembly of the triphosphine macrocyclic ligand L8, obtained as its complex with tricarbonylmolybdenum [3]. Cyclooligomerisations of molybdenum-coordinated alkenylphosphines [3] were also investigated [2], The synthesis of (CO)3Mo(L8) and (CO)3Mo(L1199) was carried out in 70-85% yield in a manner similar to that described earlier (Eq. 5.1) [3]. 

Leung P-H, Liu A, Mok KF et al (1999) Synthesis and coordination chemistry of a 14-membered macrocyclic ligand containing one phosphorus, two sulfur and one ambidentate sulfoxide donor sets. J Chem Soc Dalton Trans Inorg Chem 8 1277-1282... 

As well as sulfur, macrocycles containing other large donors such as tertiary phosphorus or arsenic atoms are also known, although the metal-ion chemistry of such ligands has been somewhat less explored. In part, this reflects the synthetic difficulties often encountered in the preparation of ligands containing these heteroatoms structures (49) (Horner, Walach Kunz, 1978), (50) (Kauffmann Ennen, 1981), and (51) (Mealli etal., 1985) provide three representative examples of such macrocycles. 

In Table 108 significant examples of nickel(II) complexes with mixed-donor macrocycles of various denticity are reported. Apart from the nitrogen atoms, the heteroatoms in the macrocyclic rings are usually either O or S, or in a few cases P. Few examples of nickel complexes with macrocycles containing all-sulfur or all-phosphorus donor atoms have been reported to date they are also included in Table 108. In nickel(II) complexes formed by mixed-donor penta- and hexa-dentate ligands the oxygen atoms of the macrocycle are often only weakly coordinated or are not coordinated at all. 

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