Synthetic and Mechanistic Studies of Organometallic Compounds to Activate NO2 and Organic Compounds.

Pt(IV) complexes of L2Pt(CH3)3NO2 (L2 = 1,2- bis(diphenylphosphino)ethane (dppe) or 1,2- bis(diphenylphosphino)benzene (dppbz)) were synthesized and characterized. On thermolysis in relatively nonpolar solvents, benzene-d6 and THF-d8, the complexes undergo competitive C-C (ethane), C-N (nitromethane), and C-O (methyl nitrite) reductive elimination. Heating in acetone-d6 the C-C reductive elimination is favored in polar solvent. With the addition of acid scavenger, PVP, C-N and C-O reductive elimination are observed in high yield in benzene-d6 and THF-d8. Mechanistic studies determined that the reactions are initiated by dissociation of NO2- , leaving a cationic five coordinate Pt(IV) intermediate. The C-N and C-O products are then formed by an SN2 attack on a methyl by the dissociated NO2-. C-C reductive elimination is in competition with nucleophilic attack and forms solely from the cationic intermediate. The complex (E)-2,4-di-tert-butyl-6-((3,5-di-tert-butyl-2 hydroxybenzylidene)amino)phenol bismuth phenyl ((ONCO)BiPh) was successfully synthesized and characterized. Attempts to synthesize the Bi(V) complex, (ONCO)BiPh(OAc)2, proved to be difficult. Under oxidizing conditions the ONCO ligand will dissociate from the bismuth and oxidize to form 5,7-di-tert-butyl-2-(2-hydroxy-3,5-di-tert-butylphenyl)benzoxazole. Utilizing tetradentate ligands like 6,6'-(piperazine-1,4-diylbis(methylene))bis(2,4-di-tert-butylphenol) or 6,6'-((1,4-diazepane-1,4-diyl)bis(methylene))bis(2-(tert-butyl)-4-methoxyphenol) could bypass the oxidation of the ligand due to the tetradentate ligands being bound more tightly then ONCOH2. Ipso nitration of boronic acids and boronic acid pinacol esters can be achieved using NO2 (g). Boronic acids and electron rich boronic pinacol esters typically do not need a catalyst to form the nitro-deboronation product, but the less reactive boronic acid pinacol esters and electron poor boronic acids seem to need a catalyst to form the desired product. Several transition metal compounds showed catalytic activity in reactions, however the most suitable catalyst was found to be IrPy3Cl3. Under these conditions good to excellent yields can be obtained.