title: Reductive cyclotetramerization of CO to squarate by a U(III) complex: the X-ray crystal structure of [(U (eta-C8H6{SiiPr3-1,4}2)(eta-C5Me4H)]2(mu-eta2: eta2-C4O4).
abstract: The U(III) mixed-sandwich compound [U(eta-C5Me4H)(eta-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 degrees C and 1 bar pressure in toluene solution to afford the crystallographically characterized dimer [(U(eta-C8H6{SiiPr3-1,4}2)(eta-C5Me4H)]2(mu-eta2: eta2-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(eta-COT)(eta-Cp)]2(mu-eta1: eta2-C3O3)] to form the squarate complex [U(eta-COT)(eta-Cp)]2(mu-eta2: eta2-C4O4)] is exothermic by 136 kJ mol-1.
authors.affiliation: The Department of Chemistry, School of Life Sciences, University of Sussex, Brighton BN1 9QJ, United Kingdom.
authors.forename: Owen T
authors.initials: OT
authors.lastname: Summerscales
authors.forename: F Geoffrey N
authors.initials: FG
authors.lastname: Cloke
authors.forename: Peter B
authors.initials: PB
authors.lastname: Hitchcock
authors.forename: Jennifer C
authors.initials: JC
authors.lastname: Green
authors.forename: Nilay
authors.initials: N
authors.lastname: Hazari