Reductive Cyclotetramerization of CO to Squarate by a U(III) Complex; the X-ray Crystal Structure of [(U(n-C8H6{SiiPr3-1,4}2)(n-C5Me4H)]2(m-n2:n2-C4O4)
journal contribution
posted on 2023-06-07, 23:09authored byOwen T Summerscales, Geoff Cloke, Peter B Hitchcock, Jennifer C Green, Nilay Hazari
The U(III) mixed-sandwich compound [U(¿-C5Me4H)(¿-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(¿-C8H6{SiiPr3-1,4}2)(¿-C5Me4H)]2(µ-¿2:¿2-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(¿-COT)(¿-Cp)]2(µ-¿1:¿2-C3O3)] to form the squarate complex [U(¿-COT)(¿-Cp)]2(µ-¿2:¿2-C4O4)] is exothermic by 136 kJ mol-1.