Synthesis, Structure, and Reactivity of the Uranium Bipyridyl Complex [{η⁵-1,2,4-(Me₃Si)₃C₅H₂}₂U(bipy)]

Abstract

Reduction of [{η 5 -1,2,4-(Me 3 Si) 3 C 5 H 2 } 2 UCl 2 ] (1) using potassium graphite (KC 8 ) in the presence of 2,2′-bipyridine forms the uranium bipyridyl metallocene [{η 5 -1,2,4-(Me 3 Si) 3 C 5 H 2 } 2 U(bipy)] (2) in good yield, which was studied by various techniques. Complex 2 constitutes an excellent starting material for further reactions with small molecules for which two dominant reaction patterns emerge: (a) in the presence of CuI, Ph 2 E 2 (E = S, Se), organic azides, diazenes, diazoalkanes, and CS 2 , complex 2 delivers a {η 5 -1,2,4-(Me 3 Si) 3 C 5 H 2 } 2 U-(II) fragment. (b) In contrast, C−C bond coupling occurs when 2 is exposed to the thio-ketone Ph 2 CS, the aldehyde p-MePhCHO, the ketones Ph 2 CO and (CH 2 ) 5 CO, and the seleno-ketone (p-MeOPh) 2 CSe to yield 15), and [{η 5 -1,2,4-(Me 3 Si) 3 C 5 H 2 } 2 U{(bipy){(p-MeOPh) 2 CSe}}] (16), respectively. On the contrary, the imido complex [{η 5 -1,2,4-(Me 3 Si) 3 C 5 H 2 } 2 UNCHPh(C 10 H 7 N 2 )] ( 17) is isolated from the reaction of 2 with PhCN.

Influence of the 1,2,4-Tri-tert-butylcyclopentadienyl Ligand on the Reactivity of the Uranium Bipyridyl Metallocene [η5-1,2,4-(Me3C)3C5H2]2U(bipy)

“…1 H NMR (C 6 D 6 ): δ 18.23 (s, 2H, phenyl), 15.90 (s,2H,NCH),8.44 (s,18H,C(CH 3 ) 3 ), 5.82 (s, 4H, phenyl), −2.76 (br s, 36H, C(CH 3 ) 3 ) ppm; other proton resonances were not observed. 13 C,63.14;H,7.73;N,3.07. Found: C,63.15;H,7.74;N,3.04.…”

Intrinsic reactivity of [η5-1,3-(Me3Si)2C5H3]2U(η4-C4Ph2) in small molecule activation

“…All organic solvents were freshly distilled from sodium benzophenone ketyl immediately prior to use. KC 8 , 14 [η 5 -1,3-(Me 3 Si) 2 C 5 H 3 ] 2 UCl 2 ( 1 ), 9 a ,15 and [η 5 -1,2,4-(Me 3 Si) 3 C 5 H 2 ] 2 UCl 2 ( 2 ) 16 were prepared according to literature methods. All other chemicals were purchased from Aldrich Chemical Co. and Beijing Chemical Co. and used as received unless otherwise stated.…”

“…Young NMR tube charged with [η 5 -1,3-(Me 3 Si) 2 C 5 H 3 ] 2 U(η 4 -C 4 Ph 2 ) ( 3 ; 17 mg, 0.02 mmol) and C 6 D 6 (0.2 mL). Resonances of 7 and those of diphenylbutadiyne and Ph 3 CCH(C 2 H 2 ) 2 CCPh 2 ( 1 H NMR (C 6 D 6 ): δ 7.29 (m, 3H, phenyl), 7.00 (m, 22H, phenyl), 6.43 (d, J = 9.8 Hz, 2H, C H ), 5.92 (d, J = 9.8 Hz, 2H, C H ), 4.92 (s, 1H, C H )) 16 were observed by 1 H NMR spectroscopy (100% conversion) when this solution was kept at room temperature for 30 min.…”

Synthesis and Reactivity of the Uranium Bipyridyl Metallocene [η5-1,3-(Me3C)2C5H3]2U(bipy)

“…Frequently employed redox-active ligands include 2,2′-bipyridine, 1,4-diazabutadiene, pyridine diimine, and arenes, which can accept electrons in their lowest unoccupied molecular orbitals and deliver them to the actinide atom when necessary. An early example represents the work by Gambarotta and coworkers utilizing the redox-active naphthalene to successfully isolate well-characterized thorium arene complexes, which mimic the reactivity of a divalent thorium­(II) compound. , Our own studies have focused on diimine ligands, such as 2,2′-bipyridine (bipy), and several well-behaved bipy actinide metallocenes, such as [η 5 -1,2,4-(Me 3 C) 3 C 5 H 2 ] 2 An­(bipy) (An = Th, U), (η 5 -C 5 Me 5 ) 2 An­(bipy) (An = Th, U), [η 5 -1,3-(Me 3 C) 2 C 5 H 3 ] 2 Th­(bipy), [η 5 -1,3-(Me 3 Si) 2 C 5 H 3 ] 2 U­(bipy), and [η 5 -1,2,4-(Me 3 Si) 3 C 5 H 2 ] 2 U­(bipy), which have been reported in recent years . Their ability to act as transfer reagents for Cp 2 An­(II) fragments allowed us to investigate a broad array of different transformations .…”

“…An early example represents the work by Gambarotta and coworkers utilizing the redox-active naphthalene to successfully isolate well-characterized thorium arene complexes, which mimic the reactivity of a divalent thorium­(II) compound. , Our own studies have focused on diimine ligands, such as 2,2′-bipyridine (bipy), and several well-behaved bipy actinide metallocenes, such as [η 5 -1,2,4-(Me 3 C) 3 C 5 H 2 ] 2 An­(bipy) (An = Th, U), (η 5 -C 5 Me 5 ) 2 An­(bipy) (An = Th, U), [η 5 -1,3-(Me 3 C) 2 C 5 H 3 ] 2 Th­(bipy), [η 5 -1,3-(Me 3 Si) 2 C 5 H 3 ] 2 U­(bipy), and [η 5 -1,2,4-(Me 3 Si) 3 C 5 H 2 ] 2 U­(bipy), which have been reported in recent years . Their ability to act as transfer reagents for Cp 2 An­(II) fragments allowed us to investigate a broad array of different transformations . Although the principle reactivity patterns of uranium-containing compounds are similar, we also noted some differences depending on the cyclopentadienyl ligand or substrate employed.…”