Osmium complexes amines

Nitrosating agents, 22 144, 145 Nitrosation, electrophilic, 22 144-152 Nitrosoarene complexes, osmium, 37 254 iV-Nitrosobis(trifluoromethyl) amine, 16 29, 30 )-Nitrosobis(trifluoromethyl) hydroxylamine, 16 46... 

C. Che u. C. Poon, Pure Appl. Chem. 60, 1201-1204 (1988) Macrocyclic Amine Complexes of Iron, Ruthenium, and Osmium". 

Ruthenium(IIl) and Osmium(Hl) Amine and Ammine Complexes. Only a few amine complexes of Os111 are known, but for Ru111 there are several types and some of their reactions have been given in Fig. 26-F-3. Both elements form 2,2 -bipyridine and 1,10-phenanthroline complexes. 

Oxidation of Alcohols and Amines using Osmium Tetroxide. Recent reports have shown that benzyUc amines can be oxidized to yield nitriles using an oxidizing system that includes catalytic osmium tetroxide. Unfortunately, only benzyUc amines could be successfully oxidized, with aliphatic derivatives giving rise to complex reaction mixtures (eq 41). ... 

Coordination Compounds. Osmium in oxidation states from +2 to +8 forms a wide range of complexes with nitrogen ligands. Amine... 

Like mthenium, amines coordinated to osmium in higher oxidation states such as Os(IV) ate readily deprotonated, as in [Os(en) (NHCH2CH2NH2)] [111614-75-6], This complex is subject to oxidative dehydrogenation to form an imine complex (105). An unusual Os(IV) hydride, [OsH2(en)2] [57345-94-5] has been isolated and characterized. The complexes of aromatic heterocycHc amines such as pyridine, bipytidine, phenanthroline, and terpyridine ate similar to those of mthenium. Examples include [Os(bipy )3 [23648-06-8], [Os(bipy)2acac] [47691-08-7],... 

In summary, the reaction of osmium tetroxide with alkenes is a reliable and selective transformation. Chiral diamines and cinchona alkakoid are most frequently used as chiral auxiliaries. Complexes derived from osmium tetroxide with diamines do not undergo catalytic turnover, whereas dihydroquinidine and dihydroquinine derivatives have been found to be very effective catalysts for the oxidation of a variety of alkenes. OsC>4 can be used catalytically in the presence of a secondary oxygen donor (e.g., H202, TBHP, A -methylmorpholine-/V-oxide, sodium periodate, 02, sodium hypochlorite, potassium ferricyanide). Furthermore, a remarkable rate enhancement occurs with the addition of a nucleophilic ligand such as pyridine or a tertiary amine. Table 4-11 lists the preferred chiral ligands for the dihydroxylation of a variety of olefins.61 Table 4-12 lists the recommended ligands for each class of olefins. 

This new process has one unexpected benefit the rates and turnover numbers are increased substantially with the result that the amount of the toxic and expensive 0s04 is considerably reduced (usually 0.002 mole %). The rate acceleration is attributed to formation of an Os04-alkaloid complex, which is more reactive than free osmium tetroxide. Increasing the concentration of 1 or 2 beyond that of 0s04 produces only negligible increase in the enantiomeric excess of the diol. In contrast quinuclidine itself substantially retards the catalytic reaction, probably because it binds too strongly to osmium tetroxide and inhibits the initial osmylation. Other chelating tertiary amines as well as pyridine also inhibit the catalytic process. 

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