Groups 4, 5 and 6 organometallic chemistry supported by new sterically demanding aryloxides

The compound 3,5-di-tert-butyl-2,6-diphenylphenol has recently been shown to be immune to intramolecular C-H bond activation due to steric demand of the meta-substituents. This importance of ortho-phenylphenoxides has prompted us to begin an investigation of the chemistry associated with related ortho-(1-naphthyl)-phenols and ortho-(ortho-tolyl)-phenols. This study is stimulated by the potential chirality of such ligands. 3,5-di-tert-butyl-2,6-di(1-naphthyl)phenol, 3,5-di-tert-butyl-2,6-di(ortho-tolyl)phenol and 3,5-di-methyl-2,6-di(1-naphthyl)phenol have been obtained. 1H NMR and X-ray crystallographic studies of the phenols and synthesized transition metal compounds have shown these phenols to be of the chiral form due to the orientation of the ortho-substituents on the phenyl ring. [CpTi(OAr)2Me2] has been found to be an active olefin polymerization catalyst in the presence of [B(C6F5) 3]. The synthesis and characterization of several the new Nb and Ta complexes [CpM(OAr)Cl3] has also been performed. Recent findings provide evidence of the first instance of a four electron reductive cleavage of O2 or Ar'N=NAr' at a single metal site. In a collaborative effort, Eisenstein, et. al. have performed a theoretical study into a possible mechanism for this unprecedented one-metal reduction of azobenzene. The addition of dry dioxygen, nitrosobenzene and diazo compounds to saturated solutions of [W(OC6HPh3-eta 6-C6H5)(OC6HPh4-2,3,5,6)(PMe 3)] results in the formation of the bis(oxo), oxo-imido and (bis)imido species [W(OC6HPh4-2,3,5,6) 2(X)(X')(PMe3)] (X = O, NAr' , NAr'; X' = O, O, NAr '), respectively. The formation of [W(OC6HPh 4-2,3,5,6)2(NTol)2(PMe3)] was amenable to kinetic studies using 1H NMR techniques. We have successfully made a kinetic model that fits the experimental data with a high degree of certainty for the very complex mechanism involved in this reaction.