Ligands cyclophosphazene

The diazaphosphane or aminoiminophosphane ligands with a NPN framework are another subclass of cyclophosphazenes. These compounds with both phosphorus in oxidation state (111) [104-110] and (V) [111-112] have been employed in the synthesis of four membered heterocycles and coordination chemistry with group 13 derivatives. Several complexes of trivalent phosphorus derivatives with both aluminum halide and alkyls are known as illustrated for 48 in Scheme 21 [113-119]. The structure determination of 48 confirms the formation of a four membered metallacycle [116, 117],... 

V. Cyclophosphazene-Based Ligands and their Coordination Chemistry... 

Togni and co-workers have used the convergent methodology to link phosphine-containing chiral ferrocene ligands on the cyclophosphazene core to obtain dendrimeric structures of the type 37 (Fig. 21) (201). The reaction with the cyclophosphazene end occurs by the replacement of the P-Cl bond and by the formation of the P-0 bond. The dendrimers contain twelve and sixteen ferrocene moieties respectively. The phosphine units present can coordinate to Rh(I) to afford metallic dendrimers, which have been shown to be excellent catalysts for the enantioselective hydrogenation of dimethyl itaconate. The product... 

The comparison of the two sets of %ILS values allows us to conclude that MYKOMET 63 appears to be actually as active as MYKO 63, but not more active. In other words, the graft of methylated aziridinyl ligands on a six-membered cyclophosphazene ring does not significantly improve the antitumoral activity with respect to the non-methylated isologues. However, because MYKOMET 63 possesses only a slight toxicity compared to MYKO 63, the new drug reported here may be of interest for eventual clinical use, no matter what difficulties are encountered in its synthesis. 

A third feature which stimulates interest in cyclophosphazenes is their behaviour as ligands towards transition metals [7,8]. Several types of coordination pattern involving either the skeletal ring nitrogen atoms and/or suitable exocyclic substituent donor atoms have been documented (Fig. 2). This area of research has been receiving widespread attention in recent years [7],... 

Various aspects of the chemistry of cyclophosphazenes have been discussed in earlier chapters, viz. synthesis (see Scheme 2.1), electronic structure (see Section 4.1.2.2 and Figure 4.2), macrocyclic ring systems (see Section 6.2.2 and Figure 6.4) and ligand behaviour (see 7.20 and 7.21 in Section 7.1.3). Phos-phazene polymers are considered in Section 11.4.3. In this section, emphasis will be placed on new developments in cyclophosphazene chemistry that are not covered elsewhere in this book. 

A solution of the metal chloride(hydrated or anhydrous) and the cyclophosphazene in the required stoichiometry(metal ligand 1 1 or 1 2) in methanol or methyl ethyl ketone was heated under reflux for... 

Cyclophosphazenes with macrocyclic ligands form a part of a general review about supramolecular interactions in synthetic procedures. The correlation between structure and NMR ( C and P) parameters for tris(2,3-naph-thalenedioxy)cyclotriphosphazene and tris(o-phenylenedioxy)cyclotriphos-phazene has been reviewed. ... 

Togni et al.169 synthesized dendrimers using a cyclophosphazene core and 16 peripheral chiral ferrocenyl ligands (Figure 10.13). The periphery of these ferrocenyldiphosphine metallo-dendrimers was decorated with [Rh(COD)2][BF4] to instill the desired catalytic properties necessary to reduce dimethyl itaconate. These metalloconstructs showed 98% ee, which compared well with the 99% ee obtained with monomeric Rh-based josiphos catalyst. 

Cyclophosphazenes as scaffolds for the construction of multi-site coordination ligands 01CSR193. 

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