Uranium(IV) Alkyl Complexes of a Rigid Dianionic NON-Donor Ligand: Synthesis and Quantitative Alkyl Exchange Reactions with Alkyllithium Reagents

Abstract

Reaction of [(XA2)UCl3{K(dme)3}] (XA2 = 4,5-bis(2,6-diisopropylanilino)-2,7-di-tert-butyl-9,9-dimethylxanthene) with 2 equiv of ((trimethylsilyl)methyl)lithium or neopentyllithium afforded red-orange [(XA2)U(CH2SiMe3)2] (1) and dark red [(XA2)U(CH2CMe3)2] (2), respectively. Reaction of 1 with an additional 1 equiv of LiCH2SiMe3 in THF yielded yellow [Li(THF) x ][(XA2)U(CH2SiMe3)3] (3), and reaction of [(XA2)UCl3{K(dme)3}] with 3 equiv of methyllithium in dme afforded yellow [Li(dme)3][(XA2)UMe3] (4). Reaction of 1 with 2.1 equiv of LiCH2CMe3 in benzene resulted in rapid conversion to 2, with release of 2 equiv of LiCH2SiMe3. Similarly, reaction of 1 with 3.3 equiv of MeLi in THF provided 4 as the [Li(THF) x ]+ salt, accompanied by 2 equiv of LiCH2SiMe3. These unusual alkyl exchange reactions resemble salt metathesis reactions, but with elimination of an alkyllithium instead of a lithium halide. Addition of a large excess of LiCH2SiMe3 to 2 or 4 did not generate detectable amounts of 1 by NMR spectroscopy, suggesting that the equilibrium in these reactions lies far to the side of complexes 2 and 4. In contrast, the reaction of [(XA2)Th(CH2SiMe3)2] (1-Th) with 2.2 equiv of LiCH2CMe3 yielded an approximate 1:1:3:1 mixture of [(XA2)Th(CH2CMe3)2] (2-Th), [(XA2)Th(CH2SiMe3)(CH2CMe3)] (5-Th), LiCH2SiMe3, and LiCH2CMe3.

Achievements in uranium alkyl chemistry: celebrating sixty years of synthetic pursuits

“…5) was possible by adding 3.3 equivalents of MeLi to (XA 2 UCl 3 )(K-(dme) 3 ) in dme, followed by extraction with toluene to remove KCl and LiCl. 64 The molecular structure of 34 shows one U-C distance (2.377(9) Å) within the range observed for the neutral derivatives, with the others (2.493(8) and 2.506(9) Å) being longer, most likely due to an increase in coordination number and overall anionic charge on the complex. Unlike 32 and 33, no signals were noted in the 1 H NMR spectrum for the methyl Fig.…”

“…98 The resonance for the methylene appears at −67.4 ppm in the 1 H NMR spectrum for 63. Single crystals were isolated as the THF adduct, (η 8 -C 8 H 8 )-(η 5 :η 1 -C 5 Me 4 CH 2 )U(THF) (64), and analysis showed two crystallographically independent molecules in the unit cell. The U-C distances of 2.586(7) and 2.596(6) Å are longer than is typical for non-cyclometallated uranium(IV) species, but are on the order of those observed for 61.…”

Potassium and Yttrium Complexes of a Rigid Bis‐Phosphido POP‐Donor Ligand

“…Ancillary ligands play a critical role in defining the thermal stability and reactivity of metal complexes, and we have previously explored the use of rigid 4,5‐bis(anilido)xanthene ligands in actinide and lanthanide chemistry. For example, the XA 2 [4,5‐bis(2,6‐diisopropylanilido)‐2,7‐di‐ tert ‐butyl‐9,9‐dimethylxanthene] pincer ligand was employed for the synthesis of thorium(IV), uranium(IV) and uranium(III) chloro complexes,, as well as dialkyl complexes of tetravalent thorium, and uranium (Figure ), thorium(IV) monoalkyl cations, and a thorium(IV) dication , . Furthermore, we recently reported the synthesis of Y, Lu and La derivatives of the XN 2 [4,5‐bis(2,4,6‐triisopropylanilido)‐2,7‐di‐ tert ‐butyl‐9,9‐dimethylxanthene] ligand, including monoalkyl derivatives (Figure ) which are highly active catalysts for alkene and alkyne hydroamination ,…”

Lanthanides and actinides: Annual survey of their organometallic chemistry covering the year 2013

“…Reaction of [K(DME) 3 ](XA 2 )UCl 3 (XA 2 = 4,5-bis(2,6-diisopropylanilino)-2,7-di-tert-butyl-9,9-dimethylxanthene) with 2 equiv. of ((trimethylsilyl)methyl)lithium or neopentyllithium afforded red-orange (XA 2 )U(CH 2 SiMe 3 ) 2 and dark red (XA 2 )U(CH 2 CMe 3 ) 2 , respectively (Scheme 183) [155].…”

“…In contrast, the reaction of (XA 2 )Th(CH 2 SiMe 3 ) 2 with 2.2 equiv. of LiCH 2 CMe 3 yielded an approximate 1:1:3:1 mixture of (XA 2 )Th(CH 2 CMe 3 ) 2 , (XA 2 )Th(CH 2 SiMe 3 )(CH 2 CMe 3 ), LiCH 2 SiMe 3 , and LiCH 2 CMe 3 [155].…”