Showing papers by "Georgina M. Rosair published in 2015"
TL;DR: A computational study of 1,1'-bis(o-carborane) is in excellent agreement with a recently-determined precise crystallographic study and establishes that the {1',2'-closo-C2B10H11} fragment is electron-withdrawing compared to H.
Abstract: Examples of singly-metallated derivatives of 1,1′-bis(o-carborane) have been prepared and spectroscopically and structurally characterised. Metallation of [7-(1′-1′,2′-closo-C2B10H11)-7,8-nido-C2B9H10]2− with a {Ru(p-cymene)}2+ fragment affords both the unisomerised species [1-(1′-1′,2′-closo-C2B10H11)-3-(p-cymene)-3,1,2-closo-RuC2B9H10] (2) and the isomerised [8-(1′-1′,2′-closo-C2B10H11)-2-(p-cymene)-2,1,8-closo-RuC2B9H10] (3), and 2 is easily transformed into 3 with mild heating. Metallation with a preformed {CoCp}2+ fragment also affords a 3,1,2-MC2B9-1′,2′-C2B10 product [1-(1′-1′,2′-closo-C2B10H11)-3-Cp-3,1,2-closo-CoC2B9H10] (4), but if CoCl2/NaCp is used followed by oxidation the result is the 2,1,8-CoC2B9-1′,2′-C2B10 species [8-(1′-1′,2′-closo-C2B10H11)-2-Cp-2,1,8-closo-CoC2B9H10] (5). Compound 4 does not convert into 5 in refluxing toluene, but does do so if it is reduced and then reoxidised, perhaps highlighting the importance of the basicity of the metal fragment in the isomerisation of metallacarboranes. A computational study of 1,1′-bis(o-carborane) is in excellent agreement with a recently-determined precise crystallographic study and establishes that the {1′,2′-closo-C2B10H11} fragment is electron-withdrawing compared to H.
32 citations
TL;DR: In this paper, the structural trans influence of σ-bonded carborane was investigated and it was shown that the trans influence is greater than that of Cl and sp2 N but less than sp2 C and sp3 C. In all three structures studied (1, 2 and 2·2THF) the metal atom is slightly distorted from square-planar towards tetrahedral (τ4 values of 0.30, 0.33 and 0.11, respectively).
16 citations
TL;DR: C-atom identification was accomplished by both the vertex-to-centroid distance and boron-hydrogen distance methods, and, in both cases, the structure established crystallographically is fully consistent with the spectroscopic data.
Abstract: Both rac-[1-(1'-4'-Cp-4',1',12'-closo-CoC2B10H11)-4-Cp-4,1,12-closo-CoC2B10H11]·2THF (Cp is cyclopentadienyl and THF is tetrahydrofuran) or [Co2(C5H5)2(C4H22B20)]·2C4H8O, (1), and meso-[1-(1'-4'-Cp-4',1',12'-closo-CoC2B10H11)-4-Cp-4,1,12-closo-CoC2B10H11] or [Co2(C5H5)2(C4H22B20)], (2), were prepared by thermolysis of a rac/meso mixture of the precursor species [1-(1'-4'-Cp-4',1',6'-closo-CoC2B10H11)-4-Cp-4,1,6-closo-CoC2B10H11] and were separated, spectroscopically characterized and studied crystallographically. Cage C-atom identification was accomplished by both the vertex-to-centroid distance and boron-hydrogen distance methods, and, in both cases, the structure established crystallographically is fully consistent with the spectroscopic data. Both the rac-(1) and meso-(2) forms share the same overall conformation (Co-C-C'-Co' ca 136°) and show clear evidence of intramolecular steric crowding resulting in tilted cyclopentadienyl ligands.
6 citations
TL;DR: One-electron reduction of 3-Cp-3,1,2-closo-CoC2B9H11 followed by heating to reflux in DME induces isomerisation to 4,1-2-isomer, a compound previously only synthesised at much higher temperatures (>380 °C).
Abstract: One-electron reduction of 3-Cp-3,1,2-closo-CoC2B9H11 followed by heating to reflux in DME (b.p. 85 °C) induces isomerisation to 4-Cp-4,1,2-closo-CoC2B9H11, a compound previously only synthesised at much higher temperatures (>380 °C). The 4,1,2-isomer has been thoroughly characterised both spectroscopically and crystallographically.
4 citations
TL;DR: A new polymorph of the title compound 2-(η-C5H5)-2,1,7-closo-CoC2B9H11, [Co(C5 H5)(C2H11B9)], in the space group P21/n has been characterized, including the unambiguous location of both cage C atoms.
Abstract: A new polymorph of the title compound 2-(η-C5H5)-2,1,7-closo-CoC2B9H11, [Co(C5H5)(C2H11B9)], in the space group P21/n has been characterized, including the unambiguous location of both cage C atoms. The precision of this study is an order of magnitude greater than that of the first polymorph [C2/c; Lopez et al. (2010). Collect. Czech. Chem. Commun. 75, 853–869].
3 citations
1 citations
TL;DR: In the title compound, [Rh(C2H11B9)(NO3)(C18H15P)2]·2.2CH2Cl2, studied as a 2.2-solvate of what was assumed to be dichloromethane, the nitrate ligand lies cis with respect to both cage C atoms and displays a pronounced preferred exopolyhedral ligand orientation (ELO).
Abstract: In the title compound, [Rh(C2H11B9)(NO3)(C18H15P)2]·2.2CH2Cl2, studied as a 2.2-solvate of what was assumed to be dichloromethane, the nitrate ligand lies cis with respect to both cage C atoms. Accordingly, the compound displays a pronounced preferred exopolyhedral ligand orientation (ELO) which is traced to both the greater trans influence of the cage B over the cage C atoms and the greater trans influence of the triphenylphosphane ligands over the nitrate ligand. The overall molecular architecture therefore agrees with that of a number of similar 3-L-3,3-L'2-3,1,2-closo-MC2B9H11 species in the literature.