1 research outputs found
Diamine Bis(phenolate) as Supporting Ligands in Organoactinide(IV) Chemistry. Synthesis, Structural Characterization, and Reactivity of Stable Dialkyl Derivatives
No full textThe homoleptic compounds [U(salan-R<sub>2</sub>)<sub>2</sub>] (R = Me (<b>1</b>), <sup>t</sup>Bu (<b>2</b>)) were prepared in high yield by salt-metathesis reactions between
UI<sub>4</sub>(L)<sub>2</sub> (L = Et<sub>2</sub>O, PhCN) and 2 equiv
of [K<sub>2</sub>(salan-R<sub>2</sub>)] in THF. In contrast, the reaction
of the tetradentate ligands salan-R<sub>2</sub> with UI<sub>3</sub>(THF)<sub>4</sub> leads to disproportionation of the metal and to
mixtures of U(IV) [U(salan-R<sub>2</sub>)<sub>2</sub>] and [U(salan-R<sub>2</sub>)I<sub>2</sub>] complexes, depending on the ligand to M ratio.
The reaction of K<sub>2</sub>salan-Me<sub>2</sub> ligand with U(IV)
iodide and chloride salts always leads to mixtures of the homoleptic
bis-ligand complex [U(salan-Me<sub>2</sub>)<sub>2</sub>] and heteroleptic
complexes [U(salan-Me<sub>2</sub>)X<sub>2</sub>] in different organic
solvents. The structure of the heteroleptic complex [U(salan-Me<sub>2</sub>)I<sub>2</sub>(CH<sub>3</sub>CN)] (<b>4</b>) was determined
by X-ray studies. Heteroleptic U(IV) and Th(IV) chloride complexes
were obtained in good yield using the bulky salan-<sup>t</sup>Bu<sub>2</sub> ligand. The new complexes [U(salan-<sup>t</sup>Bu<sub>2</sub>)Cl<sub>2</sub>(bipy)] (<b>5</b>) and [Th(salan-<sup>t</sup>Bu<sub>2</sub>)Cl<sub>2</sub>(bipy)] (<b>8</b>) were crystallographically
characterized. The salan-<sup>t</sup>Bu<sub>2</sub> halide complexes
of U(IV) and Th(IV) revealed good precursors for the synthesis of
stable dialkyl complexes. The six-coordinated alkyl complexes [Th(salan-<sup>t</sup>Bu<sub>2</sub>)(CH<sub>2</sub>SiMe<sub>3</sub>)<sub>2</sub>] (<b>9</b>) and [U(salan-<sup>t</sup>Bu<sub>2</sub>)(CH<sub>2</sub>SiMe<sub>3</sub>)<sub>2</sub>] (<b>10</b>) were prepared
by addition of LiCH<sub>2</sub>SiMe<sub>3</sub> to the chloride precursor
in toluene, and their solution and solid-state structures (for <b>9</b>) were determined by NMR and X-ray studies. These complexes
are stable for days at room temperature. Preliminary reactivity studies
show that CO<sub>2</sub> inserts into the An–C bond to afford
a mixture of carboxylate products. In the presence of traces of LiCl,
crystals of the dimeric insertion product [Th<sub>2</sub>Cl(salan-<sup>t</sup>Bu<sub>2</sub>)<sub>2</sub>(μ-η<sup>1</sup>:η<sup>1</sup>-O<sub>2</sub>CCH<sub>2</sub>SiMe<sub>3</sub>)<sub>2</sub>(μ-η<sup>1</sup>:η<sup>2</sup>-O<sub>2</sub>CCH<sub>2</sub>SiMe<sub>3</sub>)] (<b>11</b>) were isolated. The structure
shows that CO<sub>2</sub> insertion occurs in both alkyl groups and
that the resulting carboxylate is easily displaced by a chloride anion
