2 research outputs found
Reductive Silylation of the Uranyl Ion with Ph<sub>3</sub>SiOTf
The
reaction of 2 equiv of Ph<sub>3</sub>SiOTf with UO<sub>2</sub>(dbm)<sub>2</sub>(THF) (dbm = <i>O</i>CÂ(Ph)ÂCHCÂ(Ph)<i>O</i>) and UO<sub>2</sub>(<sup>Ar</sup>acnac)<sub>2</sub> (<sup>Ar</sup>acnac = Ar<i>N</i>CÂ(Ph)ÂCHCÂ(Ph)<i>O</i>; Ar =
3,5-<sup>t</sup>Bu<sub>2</sub>C<sub>6</sub>H<sub>3</sub>) results
in the formation of UÂ(OSiPh<sub>3</sub>)<sub>2</sub>(dbm)<sub>2</sub>(OTf) (<b>1</b>) and [UÂ(OSiPh<sub>3</sub>)<sub>2</sub>(<sup>Ar</sup>acnac)<sub>2</sub>]Â[OTf] (<b>2</b>), respectively,
in good yield
Oxidation of the 14-Membered Macrocycle Dibenzotetramethyltetraaza[14]annulene upon Ligation to the Uranyl Ion
Reaction
of Li<sub>2</sub>(tmtaa) (tmtaaH<sub>2</sub> = dibenzotetramethyltetraaza[14]Âannulene)
with 1 equiv of [UO<sub>2</sub>Cl<sub>2</sub>(THF)<sub>3</sub>], in
an attempt to form <i>cis</i>-[UO<sub>2</sub>(tmtaa)], affords
the bisÂ(uranyl) complex [LiÂ(THF)<sub>3</sub>]Â[LiÂ(THF)<sub>2</sub>]Â[(UO<sub>2</sub>Cl<sub>2</sub>)<sub>2</sub>(tmtaa)] (<b>1</b>) as a
red-brown crystalline solid in modest yield. Complex <b>1</b> can be synthesized rationally by reaction of Li<sub>2</sub>(tmtaa)
with 2 equiv of [UO<sub>2</sub>Cl<sub>2</sub>(THF)<sub>3</sub>]. Under
these conditions, it can be isolated in 44% yield. In the solid state,
complex <b>1</b> features two [UO<sub>2</sub>Cl<sub>2</sub>]Â fragments that are bridged by a
highly puckered (tmtaa)<sup>2–</sup> ligand. Both uranyl fragments
feature normal uranyl metrical parameters (U–O (av.) = 1.78
Å, O–U–O = 176.8(3)° and 178.0(3)°).
The most notable structural feature of <b>1</b>, however, is
the presence of a lithium cation that coordinates to an oxo ligand
from each uranyl fragment. In contrast to the Li<sub>2</sub>(tmtaa)
reaction, addition of [KÂ(DME)]<sub>2</sub>[tmtaa] to 1 equiv of [UO<sub>2</sub>Cl<sub>2</sub>(THF)<sub>3</sub>] results in formation of the
2e<sup>–</sup> oxidation products of (tmtaa)<sup>2–</sup>. Three isomers of C<sub>22</sub>H<sub>22</sub>N<sub>4</sub> (compounds <b>2</b>, <b>3</b>, and <b>4</b>) were isolated as a
mixture of orange crystals in 41% combined yield. All three isomers
were characterized by X-ray crystallography. We hypothesize that these
ligand oxidation products are formed upon decomposition of the unobserved
cis uranyl intermediate, <i>cis</i>-[UO<sub>2</sub>(tmtaa)],
which undergoes a facile intramolecular redox reaction