Oxo and Hydroxo Organometallic Complexes of Tantalum: Soluble Molecular Models of Tantalum Oxide

The tantalum complex [TaCp*Cl<sub>2</sub>{2,6(OOC)<sub>2</sub>py-κ<sup>2</sup><i>O</i>,<i>O</i>}] (<b>1</b>) has been synthesized by reaction of [TaCp*Cl<sub>4</sub>], Cp* = η<sup>5</sup>-C<sub>5</sub>Me<sub>5</sub>, with 2,6-pyridinedicarboxylic acid. Complex <b>1</b> reacts with AgOTf, OTf = trifluoromethylsulfate, to yield the new tantalum carboxylate derivative [TaCp*Cl(OTf){2,6(OOC)<sub>2</sub>py-κ<sup>2</sup><i>O</i>,<i>O</i>}] (<b>2</b>) or with KOH to render the dinuclear oxo compound [TaCp*(μ-O){2,6(OOC)<sub>2</sub>py-κ<sup>2</sup><i>O</i>,<i>O</i>}] <sub>2</sub> (<b>3</b>). The reaction of <b>3</b> with H<sub>2</sub>O and HOTf gives the dinuclear hydroxo derivative [{TaCp*{2,6(OOC)<sub>2</sub>py-κ<sup>2</sup><i>O</i>,<i>O</i>}}<sub>2</sub>(μ-OH)<sub>3</sub>](OTf) (<b>5</b>). The structures of complexes <b>1</b>, <b>2</b>, <b>3</b>, and <b>5</b> have been established by X-ray diffraction methods.