Synthesis and Reactivity of a U(IV) Dibenzyne Complex

Reaction of UCl₄ with 6 equiv of 2-Li-C₆H₄CH₂NMe₂ affords the U­(IV) dibenzyne complex [Li]₂[U­(2,3-C₆H₃CH₂NMe₂)₂(2-C₆H₄CH₂NMe₂)₂] (<b>1</b>), which can be isolated as a dark blue solid in 40% yield. Complex <b>1</b> represents a rare example of a structurally characterized dibenzyne complex, and its solid-state metrical parameters suggest that the two benzyne ligands are best described with the dianionic metallacyclopropene resonance form. The reactivity of <b>1</b> with a variety of electrophiles and oxidants, including benzophenone, 1-azidoadamantane, and benzonitrile, was also explored. Reaction of <b>1</b> with 2 equiv of benzophenone affords the insertion product [Li]­[U­(2-C₆H₃CH₂NMe₂-3-C<i>O</i>Ph₂)₂(2-C₆H₄CH₂NMe₂)] (<b>3</b>) as a red-orange solid in 61% yield, concomitant with formation of 1 equiv of 2-Li-C₆H₄CH₂NMe₂. Reaction of <b>1</b> with 2 equiv of PhCN also affords an insertion product, [Li]­[Li­(Et₂O)]­[U­(2,3-C₆H₃CH₂NMe₂)­(2-C₆H₃CH₂NMe₂-3-C­(Ph)<i>N</i>)­(2-C₆H₄CH₂NMe₂)₂] (<b>4</b>), as a green-brown crystalline solid in 21% yield. In an attempt to oxidize <b>1</b> to U­(VI), the reaction of <b>1</b> with 2 equiv of AdN₃, in the presence of 2 equiv of 12-crown-4, was probed. This reaction only yields the U­(IV) insertion product [Li­(12-crown-4)₂]­[Li]­[U­(2-C₆H₃CH₂NMe₂-3-(<i>N</i>-N<i>N-</i>Ad))₂(2-C₆H₄CH₂NMe₂)₂] (<b>5</b>) as a red crystalline solid in 42% yield. No evidence for the formation of a U­(VI) imido complex is observed in the reaction mixture

Synthesis and Reactivity of a U(IV) Dibenzyne Complex

Reaction of UCl₄ with 6 equiv of 2-Li-C₆H₄CH₂NMe₂ affords the U­(IV) dibenzyne complex [Li]₂[U­(2,3-C₆H₃CH₂NMe₂)₂(2-C₆H₄CH₂NMe₂)₂] (<b>1</b>), which can be isolated as a dark blue solid in 40% yield. Complex <b>1</b> represents a rare example of a structurally characterized dibenzyne complex, and its solid-state metrical parameters suggest that the two benzyne ligands are best described with the dianionic metallacyclopropene resonance form. The reactivity of <b>1</b> with a variety of electrophiles and oxidants, including benzophenone, 1-azidoadamantane, and benzonitrile, was also explored. Reaction of <b>1</b> with 2 equiv of benzophenone affords the insertion product [Li]­[U­(2-C₆H₃CH₂NMe₂-3-C<i>O</i>Ph₂)₂(2-C₆H₄CH₂NMe₂)] (<b>3</b>) as a red-orange solid in 61% yield, concomitant with formation of 1 equiv of 2-Li-C₆H₄CH₂NMe₂. Reaction of <b>1</b> with 2 equiv of PhCN also affords an insertion product, [Li]­[Li­(Et₂O)]­[U­(2,3-C₆H₃CH₂NMe₂)­(2-C₆H₃CH₂NMe₂-3-C­(Ph)<i>N</i>)­(2-C₆H₄CH₂NMe₂)₂] (<b>4</b>), as a green-brown crystalline solid in 21% yield. In an attempt to oxidize <b>1</b> to U­(VI), the reaction of <b>1</b> with 2 equiv of AdN₃, in the presence of 2 equiv of 12-crown-4, was probed. This reaction only yields the U­(IV) insertion product [Li­(12-crown-4)₂]­[Li]­[U­(2-C₆H₃CH₂NMe₂-3-(<i>N</i>-N<i>N-</i>Ad))₂(2-C₆H₄CH₂NMe₂)₂] (<b>5</b>) as a red crystalline solid in 42% yield. No evidence for the formation of a U­(VI) imido complex is observed in the reaction mixture