Phosphorus donor macrocycles

Macrocyclic complexes of type [M11LX2] (where L = (190) and X = C1, Br, I, and NCS) have been synthesized. These complexes appeared exceptionally stable relative to other manganese(II) phosphine complexes. They can be manipulated in air for minutes without decomposition, a finding that was ascribed to the steric protection afforded by this macrocyclic ligand species. 

Mass spectrometry studies have demonstrated the formation of a number of 1 1 crown polyether complexes of manganese(II) as cationic species in the gas phase.  

A number of solvent extraction experiments have demonstrated that individual crown ethers in combination with a lipophilic sulfonic acid (such as didodecylnaphthalene sulfonic acid) are efficient, synergistic phase transfer agents for manganese(II) from aqueous solution into an organic phase. The X-ray structure of the manganese di-t-butylnaphthalenesul-fonate with cyclohexano-15-crown-5 ether as its toluene solvate has been reported.  

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Virtually all types of metal ions have been complexed with macrocyclic ligands.2-7 Complexes of transition metal ions have been studied extensively with tetraaza macrocycles (Chapter 21.2). Porphyrin and porphyrin-related complexes are of course notoriously present in biological systems and have been receiving considerable investigative attention (Chapter 22).8 Macrocyclic ligands derived from the Schiffbase and template-assisted condensation reactions of Curtis and Busch also figure prominantly with transition metal ions.6,7 The chemistry of these ions has been more recently expanded into the realm of polyaza, polynucleating and polycyclic systems.9 Transition metal complexes with thioether and phosphorus donor macrocycles are also known.2... 

Complexes with mixed-donor macrocycles and with all-phosphorus and all-sulfur macrocycles 257... 

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. 

The phosphorus macrocycles are made via template condensation of coordinated polyphosphine ligands and a dibromoalkane (equation 8).60 A more recently reported method involves a template-assisted single-stage ring closure (equation 9).61 The arsenic donor macrocycles are synthesized by reacting lithiated polyarsanes with a dichloroalkane (equation 10).62... 

Classification of macromonocycles (Figure 2) can be made on the basis of donor atom, i.e. nitrogen, oxygen, sulfur, phosphorus, arsenic and mixed donor systems, as well as topicity, i.e. mono- versus di- or poly-topic. The planar nitrogen donor macrocycles and other tetraaza macro-... 

There are a number of macrocycles with phosphorus donors only, or with mixed sets of P and N or P and S donors, for example, (10-LXXXa and b). 

The simple mixed donor macrocycles (14) at one time were the major sonrce of study of the influence of the incorporation of soft phosphorus and arsenic donors into macrocycles. Mixed oxygennitrogen macrocycles have been studied quite extensively, since they serve as bridges for examining the coordination tendencies of the aza macrocycles and the oxa crown ethers. 

Simple mixed donor macrocycles, such as aza oxa, aza thia, oxa thia, and analogous phospha and arsa analogs are generally achieved via combinations of the routes used for synthesis of the pure donor analogs. Since the possibilities are so extensive they will not be treated here, but are found elsewhere. New mixed donor phosphorus techniques have been devised for phospha-thia and phospha-aza macrocycles. ... 

The alkylation technique successfully explored for linking cis-disposed nitrogen and sulphur donor atoms has been extended to phosphorus. The macrocyclic com-potmd benzo-[15]aneP4, isolated as the complex [Ni(L1203)]Cl2, was synthesised by the template reaction shown in Scheme 5-2. Note that the terminal coordinated phosphorus donor atoms can be involved in the chelate-forming template reaction only after their deprotonation, which is facihtated by the electron-withdrawing effect of the metal ion and the presence of a base (K2CO3). 

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. 

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. 

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