The reactions of [Ir(κ3N,N,H-Tai)(COD)] and [Ir(κ3N,N,H-PhBai)(COD)] (where Tai = HB(azaindolyl)3 and PhBai = Ph(H)B(azaindolyl) 2) with carbon monoxide result in the formation of Z-type iridium-borane complexes supported by 7-azaindole units. Analysis of the reaction mixtures involving the former complex revealed the formation of a single species in solution, [Ir(η1-C8H 13){κ3N,N,B-B(azaindolyl)3}(CO) 2], as confirmed by NMR spectroscopy. In the case of the PhBai complex, a mixture of species was observed. A postulated mechanism for the formation of the new complexes has been provided, supported by computational studies. Computational studies have also focused on the reaction step involving the migration of hydrogen from boron (in the borohydride group) to the iridium center. These investigations have demonstrated a small energy barrier for the hydrogen migration step (ΔG298 = 10.3 kcal mol-1). Additionally, deuterium labeling of the borohydride units in Tai and PhBai confirmed the final position of the former borohydride hydrogen atom in the resulting complexes. The importance of the "third azaindolyl" unit within these transformations and the difference in reactivity between the two ligands are discussed. The selective coordination properties of this family of metallaboratrane complexes have also been investigated and are discussed herein. © 2013 American Chemical Society.

The selectivity of the mixed-sandwich U(III) complexes of the type [U(η-C8H6{SiiR3-1,4} 2)(η-CpR′)] (R = Me, iPr; R′ = Me4H, Me5, Me4iPr, Me 4SiMe3, Me4Et) toward the reductive coupling of CO to form uranium-bound oxocarbons has been explored. In this context, the new U(III) mixed-sandwich complexes [U(η-C8H6{Si iPr3-1,4}2)(η-CpMe4TMS)], [U(η-C8H6{SiiPr3-1,4} 2)(η-CpMe4iPr)], [U(η-C8H 6{SiiPr3-1,4}2)(η-Cp Me4Et)], [U(η-C8H6{SiMe3-1,4} 2)(η-Cp*)], and [U(η-C8H 6{SiMe3-1,4}2)(η-CpMe4TMS)] have been prepared and structurally characterized. The reactivity toward CO is dominated by the "global" sterics around the uranium center, while selectivity for oxocarbon formation is largely regulated by the steric bulk of the CpR′ ligand. Accordingly, with excess CO [U(η-C 8H6{SiiPr3-1,4}2)(η- CpMe4TMS)] and [U(η-C8H6{Si iPr3-1,4}2)(η-CpMe4iPr)] show no reactivity, [U(η-C8H6{SiMe3-1,4} 2)(η-CpMe4TMS)] is completely selective for the formation of the ynediolate complex [U(η-C8H 6{SiMe3-1,4}2)(η-CpMe4TMS)] 2(μ-η1:η1-13C 2O2), [U(η-C8H6{SiiPr 3-1,4}2)(η-Cp*)] affords only the deltate complex [U(η-C8H6{SiiPr3-1,4} 2)(η-Cp*)]2(μ-η2: η2-C3O3), and [U(η-C8H 6{SiiPr3-1,4}2)(η-CpMe4H)] gives solely the squarate complex [U(η-C8H6{SiiPr 3-1,4}2)(η-CpMe4H)]2(μ- η2:η2-C4O4). Additionally, the squarate moiety has been removed from the uranium center in the last complex by reaction with Me3SiCl to afford the TMS ester of squaric acid, C4O2(OTMS)2. © 2012 American Chemical Society.

The novel bimetallic bis(pentalene) complex Ti2(μ:η5,η5-Pn†)2 (Pn† = C8H4(SiiPr3-1,4)2) has been synthesised and structurally characterised. Structural data show a Ti-Ti distance of 2.399(2) å, consistent with a strong metal-metal interaction, which DFT calculations best describe as a double bond with σ and π components. © 2013 The Royal Society of Chemistry.

The facile two-electron reduction of the phosphaalkyne tBuC=P by the U III cyclopentadienyl-pentalene mixed-sandwich complex [U(η5-C5Me5){η8-C 8H4(SiiPr3)2}] is reported. A single-crystal X-ray structural analysis of the diuranium(IV) product [(U{η5-C5Me5}{η8-C 8H4(SiiPr3)2})2(μ- tBuCP)] shows that it contains a slightly unsymmetrical, bridging μ-η2:η1- ligated phosphaalkene dianion. © 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.