ja063222r_si_003.cif (29.83 kB)

Reductive Cyclotetramerization of CO to Squarate by a U(III) Complex:  The X-ray Crystal Structure of [(U (η-C8H6{SiiPr3-1,4}2)(η-C5Me4H)]2(μ-η2: η2-C4O4)

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posted on 02.08.2006, 00:00 by Owen T. Summerscales, F. Geoffrey N. Cloke, Peter B. Hitchcock, Jennifer C. Green, Nilay Hazari
The U(III) mixed-sandwich compound [U(η-C5Me4H)(η-C8H6{SiiPr3-1,4}2)(THF)] 1 may be prepared by sequential reaction of UI3 with K[C5Me4H] in THF followed by K2[C8H6{SiiPr3-1,4}2]. 1 reacts with carbon monoxide at −30 °C and 1 bar pressure in toluene solution to afford the crystallographically characterized dimer [(U(η-C8H6{SiiPr3-1,4}2)(η-C5Me4H)]2(μ−η2: η2−C4O4) 2, which contains a bridging squarate unit derived from reductive cyclotetramerization of CO. DFT computational studies indicate that addition of a 4th molecule of CO to the model deltate complex [U(η-COT)(η-Cp)]2(μ−η: η−C3O3)] to form the squarate complex [U(η-COT)(η-Cp)]2(μ−η2: η2−C4O4)] is exothermic by 136 kJ mol-1.