Synthesis and Characterization of an Oxo-Centered Homotrimetallic Uranium(IV)- Cyclobutadienyl Dianion Complex

Josef Boronski, Laurence Doyle, Ashley Wooles, John Seed, Stephen Liddle

Research output: Contribution to journalArticlepeer-review

Abstract

Reaction of [Li2{C4(SiMe3)4}(THF)2] (1) with [U(η5-C5Me5)I2(THF)] (2) produced the oxo-centered homotrimetallic uranium-pentamethylcyclopentadienyl complex [{U(η5 -C5Me5)(µ-I)2}3{µ3- O}{Li(THF)3}0.5]2[Li(THF)4] (3) as the only isolable product in very low yield. In contrast, reaction of 2 with [Mg{C4(SiMe3)4}(THF)3] (4) produced the oxo-centered homotrimetallic uranium(IV)- cyclobutadienyl complex [{U(C4[SiMe3]4)(µ-I)2}3{µ3-O}][Mg(THF)6] (5). The solid state structure of 5 reveals average U-C and U-C4 centroid distances of 2.574(7) and 2.355(7) Å, respectively, and displacement of the silicon atoms from the C4 plane ranging from 0.478(13) to 0.6528(12) Å. Variable temperature magnetic susceptibility measurements on powdered 5 confirm the exclusively uranium(IV) formulation with no evidence found for any uranium···uranium magnetic coupling. Quantum chemical calculations suggest polarized uranium-cyclobutadienyl bonding interactions, but underscore the essentially exclusive π-bonding nature of these linkages with no δ-bonding component. This π-bonding also accounts for the displacements of the silyl groups from the C4- plane, which maximises U-C4 orbital overlap. The compounds reported here have been variously characterized by single crystal X-ray diffraction, ATR-IR spectroscopy, elemental analysis, SQUID magnetometry, and quantum chemical calculations.
Original languageEnglish
JournalOrganometallics
Publication statusAccepted/In press - 14 Apr 2020

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