Nitrogen-rich ligands

Many of the newly developed pyrotechnics are based on metal complexes with very nitrogen-rich ligands, mainly tetrazole derivatives (Fig. 2.17). Unlike conventional... 

Since the early 1980s rich thermal and photochemical redox chemistries of Os =N species containing nonlabile oxidation-resistant nitrogen donor ligands have emerged. However, there are only a few examples of ruthenium(VI) nitrido complexes of this type, and their redox chemistry is largely unexplored. 

A practical six-step synthesis of ( l-camptothecin has been achieved utilizing HR as a key reaction. Intramolecular reaction of the optically pure quinoline chloride 221 with the enamide moiety gave pure (5)-camptothecin (222) after recrystallization in 64% yield under usual conditions [101]. It should be added that chlorides of heterocyclic compounds such as pyridines and quinolines are activated by electron-attracting nitrogens and react smoothly without using electron-rich ligands. 

V(V)-containing con lexes have also been proposed as IMA s (19,32). The coordination chemistry of vanadium(V) and vanadium(rV) usually involves oxygen-rich ligands, but nitrogen- and sulfur-bonding are also well-represented... 

Also in the divalent state, Pd and Pt show the class-b characteristic of preferring CN and ligands with nitrogen or heavy donor atoms rather than oxygen or fluorine. Platinum(IV) by contrast is more nearly class-a in character and is frequently reduced to Pt by P- and Aj-donor ligands. The organometallic chemistry of these metals is rich and varied and that involving unsaturated hydrocarbons is the most familiar of its type. 

Epoxidations of chiral allenamides lead to chiral nitrogen-stabilized oxyallyl catioins that undergo highly stereoselective (4 + 3) cycloaddition reactions with electron-rich dienes.6 These are the first examples of epoxidations of allenes, and the first examples of chiral nitrogen-stabilized oxyallyl cations. Further elaboration of the cycloadducts leads to interesting chiral amino alcohols that can be useful as ligands in asymmetric catalysis (Scheme 2). 

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