Phosphorus macrocycles

Kyba and his coworkers have made numerous phosphorus-containing macrocycles and many of these are recorded in the tables at the end of this chapter. In addition, this group has prepared and reported quite a number of arsinocycles. The observations concerning phosphorus macrocycles apply in general to the arsinocycles as well, but the inversion barrier is even higher for the latter than the former. ... 

Quite recently, Ciampolini and coworkers have reported the synthesis of two isomeric mked oxygen-phosphorus macrocycles and the crystal structures of their cobalt complexes. Synthesis of macrocycle 27 was accomplished by condensation of 1,2-bis-(phenylphosphino)ethane dianion with 2,2 -dichlorodiethyl ether in THE. The two isomers of 27 were isolated in 1.5% and 2% yield. The synthesis is formulated in Eq. (6.17), below. 

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... 

In view of the widespread use of tertiary phosphines in coordination chemistry, it is somewhat surprising that phosphorus-containing macrocycles have not evoked more interest. In part this is undoubtedly due to experimental difficulties. The synthesis of P macrocycles is doubly difficult, since the usual difficulties and hazards of phosphorus(III) chemistry are compounded by the complexities and low yields of multistage heterocyclic macrocyclic syntheses. Because of these difficulties, the development of synthetic methods has been slow. Mann s survey73 of the heterocyclic derivatives of P, As, Sb and Bi did not mention phosphorus macrocycles and recent textbooks74,75 give them only cursory mention. 

This chapter describes phosphorus heterocycles with greater than six-membered rings, which appeared in the literature after 1995. For the phosphorus macrocycles published before 1996, see reviews by Pabel and Wild in CHEC-II(1996) < 1996CHEC-II(9)947> and by Caminade and Majoral <1994CRV1183>. 

Phosphorus macrocycles can exist in a variety of conformations, a number of which are stable. The barrier for inversion of phosphate is 146.4kJmoH. Hence there are five conformations possible for the tetraphosphorus macrocycle (12). Two are preferred the one in which the macrocyclic benzo groups are trans (55) and that in which they are cis (56). ... 

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... 

It is not within the scope of this article to detail the preparative aspects of organophosphorus chemistry (see Phosphorus Organophosphorus Chemistry). We limit ourselves to indicating the two basic routes to phosphorus macrocycles. The first route utihzes the conventional synthetic methods of organometaUic chemistry and is illustrated by Ciampolini and coworkers here, but others could... 

The alternative route to phosphorus macrocycles uses the coordinating properties of phosphine ligands to assemble the macrocycle precursors in favorable conformations using a transition metal as a template. The general principles are illustrated in Scheme 4, developed by Cooper and coworkers. This template synthesis of macrocycles may occur fortuitously for example, Musker and coworkers fortuitously dimerized their ligand (41) to afford the macrocycle [16]aneP2S2 (44). 

Quantitative data are sparse for phosphorus macrocycle complex stabilities. However, the broad thermodynamic principles that apply to nitrogen systems should apply to those of phosphorus. The macrocylic effect is the net effect of a number of factors, inter alia changes in entropy, enthalpy, pH, solvent effects, ring size, and conformation, that results... 

The N3 groups linked to thiophosphoryl funetions are good leaving groups for regioselective nueleophilic substitutions on maeromolecules sueh as phosphorus macrocycles (161) (e.g. Scheme 48). ... 

The subject of macrocyclic conformation is complex and will be illustrated here by reference to Kyba s systems. These 11- " and 14-membered phosphorus macrocycles exist in various conformations. The barrier to inversion for phosphines is approximately 146.4kJmol , but some conformations are remarkably stable. For example, 2,6,10-triphenyl-2,6,10-triphosphabi-cyclo[9.4.0]pentadeca-l l(l),12,14-triene (11) has three conformers (a-c in Figure 1). When a xylene solution of (11) is refluxed (135 °C, 1 h), only (a) is obtained when crystallized. The phenyl groups at the 2-P and 10-P remain cis, although the 6-P does invert, but the crystallization process favours conformer (a) over (b). The equilibrium (a) (b) is displaced to the LHS by removal of (a) as it... 

The catalytic activity of the phosphorus macrocycle complexes 23 (R = iBu, M = Re(CO)2Cl and Re(CO)2H) in cyclic alkenes polymerisation was studied. Addition of norbornene to the solution of activated catalyst results in the strongly exothermic reaction proceeding at a reasonable rate at 0 °C. The behaviour of the... 

Bauer I, Habicher WD, Antipin IS et al (2004) Phosphorus macrocycles and cryptands. Russ Chem Bull 53 1402-1416... 

Mathey F, Mercier F, Le Floch P (1999) New carbon-phosphorus macrocycles. Phosphorus Sulfur Silicon Relat Elem 144—146 251-256... 

Avarvari N, Maigrot N, Ricard L et al (1999) Synthesis and X-ray crystal structures of silacalix[n]phosphinines the st sp2-based phosphorus macrocycles. Chem Eur J 5 2109-2118... 

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