Amphiphilicity in Oxygen Atom Transfer Reactions of Oxobis(iminoxolene)osmium Complexes.

Oxobis(iminoxolene)osmium(VI) compounds (ap)OsO (ap = 2-(4-RCHN)-4,6-BuCHO) are readily deoxygenated by phosphines and phosphites to give five-coordinate (ap)Os(PR') or six-coordinate (ap)Os(PR'). Structural data indicate that this net two-electron reduction is accompanied by apparent oxidation of the iminoxolene ligands due to their greater ability to engage in π donation to the reduced deoxy form of the osmium complex. In (ap)Os(PR'), the HOMO is a ligand-based combination of the iminoxolene redox-active orbitals, while the LUMO is a highly covalent metal-iminoxolene π* orbital.

High-valent osmium iminoxolene complexes.

2-(Arylamino)-4,6-di-tert-butylphenols containing 4-substituted phenyl groups (RapH2) react with oxobis(ethylene glycolato)osmium(vi) in acetone to give square pyramidal bis(amidophenoxide)oxoosmium(vi) complexes. A mono-amidophenoxide complex is observed as an intermediate in these reactions. Reactions in dichloromethane yield the diolate (Hap)2Os(OCH2CH2O).

Highly covalent metal-ligand π bonding in chelated bis- and tris(iminoxolene) complexes of osmium and ruthenium.

The bis(aminophenol) 2,2'-biphenylbis(3,5-di-tert-butyl-2-hydroxyphenylamine) (ClipH) forms trans-(Clip)Os(py) upon aerobic reaction of the ligand with {(p-cymene)OsCl} in the presence of pyridine and triethylamine. A more oxidized species, cis-β-(Clip)Os(OCHCHO), is formed from reaction of the ligand with the osmium(vi) complex OsO(OCHCHO), and reacts with MeSiCl to give the chloro complex cis-β-(Clip)OsCl. Octahedral osmium and ruthenium tris-iminoxolene complexes are formed from the chelating ligand tris(2-(3',5'-di-tert-butyl-2'-hydroxyphenyl)amino-4-methylphenyl)amine (MeClampH) on aerobic reaction with divalent metal precursors.