Synthesis and Insertion Chemistry of Mixed Tether Uranium Metallocene Complexes

Abstract

The synthesis of mixed tethered alkyl uranium metallocenes has been investigated by examining the reactivity of the bis(tethered alkyl) metallocene [(η(5)-C(5)Me(4)SiMe(2)CH(2)-κC)(2)U] (1) with substrates that react with only one of the U-C linkages. The effect of these mixed tether coordination environments on the reactivity of the remaining U-C bond has been studied by using CO insertion chemistry. One equivalent of azidoadamantane (AdN(3)) reacts with 1 to yield the mixed tethered alkyl triazenido complex [(η(5)-C(5)Me(4)SiMe(2)CH(2)-κC)U(η(5)-C(5)Me(4)SiMe(2)-CH(2)NNN-Ad-κ(2)N(1,3))]. Similarly, a single equivalent of CS(2) reacts with 1 to form the mixed tethered alkyl dithiocarboxylate complex [(η(5)-C(5)Me(4)SiMe(2)CH(2)-κC)U(η(5)-C(5)Me(4)SiMe(2)-CH(2)C(S)(2)-κ(2)S,S')], a reaction that constitutes the first example of CS(2) insertion into a U(4+)-C bond. Complex 1 reacts with one equivalent of pyridine N-oxide by C-H bond activation of the pyridine ring to form a mixed tethered alkyl cyclometalated pyridine N-oxide complex [(η(5)-C(5)Me(4)SiMe(2)CH(2)-κC)(η(5)-C(5)Me(4)SiMe(3))U(C(6)H(4)NO-κ(2)C,O)]. The remaining (η(5)-C(5)Me(4)SiMe(2)CH(2)-κC)(2-) ligand in each of these mixed tethered species show reactivity towards CO and tethered enolate ligands form by insertion. Subsequent rearrangement have been identified in [(η(5)-C(5)Me(4)SiMe(3))U(C(5)H(4)NO-κ(2)C,O)(η(5)-C(5)Me(4)SiMe(2)C(=CH(2))O-κO)] and [(η(5)-C(5)Me(4)SiMe(2)CH(2)NNN-Ad-κ(2)N(1,3))U(η(5)-C(5)Me(4)SiMe(2)C(=CH(2))O-κO)].

Synthesis and Reduction of Uranium(V) Imido Complexes with Redox‐Active Substituents

“…Similar compounds to side product 5 have been synthesized by insertion of organic azides into U−C bonds by the Evans and Bart groups . The precedent for azide insertion into U−C bonds further supports the proposal that 2‐azidonaphthalene inserts into the U−C bond of U IV [CH 2 SiMe 2 N(SiMe 3 )][N(SiMe 3 ) 2 ] 3 .…”

“…The side product 5 was likely formed by reaction of 2-azidonaphthalene with the in situ generated cyclometalated compound, U IV [CH 2 SiMe 2 NSiMe 3 ][N(SiMe 3 ) 2 ] 2 ,w hich is ac ommon byproduct of the chemistry of U III [N(SiMe 3 ) 2 ] 3 . [61,62] Similar compounds to side product 5 have been synthesized by insertion of organic azides into UÀCb onds by the Evans [24,63,64] and Bartg roups. [40] The precedent fora zide insertion into UÀCb onds furthers upports the proposal that 2-azidonaphthalene insertsi nto the UÀCb ond of U IV [CH 2 SiMe 2 N(SiMe 3 )][N(SiMe 3 ) 2 ] 3 .A nX -ray structure of compound 5 was obtained ( Figure 1), which showedt hat the U(1)À N(4) and U(1)ÀN(6) bond lengths were 2.408(2) and 2.453(2) , respectively.T he similarb ond lengthsi mplied that the negative chargew as delocalized across the triazenido moiety.T he average UÀN amide bond length was 2.2771 (16) ,w hich was similar to those in previously reported uranium(IV)m etallacycle complexes.…”

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

“…Heating complexes of the form Cp*(C 8 H 8 )UR (R = Me, Ph) generates (η 8 -C 8 H 8 )(η 5 :η 1 -C 5 Me 4 CH 2 )U ( 63) with a loss of RH. 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.…”

Applications of boroxide ligands in supporting small molecule activation by U(iii) and U(iv) complexes

“…The formation of oxo complexes with structures such as UL n vO, [21][22][23] L n UuO 13,24 or U-O-U 25 N-oxide to a metal is not unique, although relatively rare. 13,[26][27][28][29] The solid-state structure reveals a U IV complex with a distorted octahedral geometry with the boroxide ligands in the equatorial positions and the pyridine N-oxide ligands in the axial positions ( Fig. 3).…”