Showing papers by "Georgina M. Rosair published in 2014"

Asymmetric 1,8/13,2,x-M2C2B10 14-vertex metallacarboranes by direct electrophilic insertion reactions; the VCD and BHD methods in critical analysis of cage C atom positions

Abstract: The isolation of six isomeric, low-symmetry, dicobaltacarboranes with bicapped hexagonal antiprismatic cage structures, always in low yield, is described from reactions in which 13-vertex cobaltacarborane anions and sources of cobalt-containing cations were present. The vertex-to-centroid distance (VCD) and boron–H distance (BHD) methods are used to locate the correct C atom positions in the cages, thus allowing the compounds to be identified as 1,13-Cp2-1,13,2,10-closo-Co2C2B10H12 (1), 1,8-Cp2-3-OEt-1,8,2,10-closo-Co2C2B10H11 (2), 1,13-Cp2-1,13,2,9-closo-Co2C2B10H12 (3), 1,8-Cp2-1,8,2,4-closo-Co2C2B10H12 (4), 1,13-Cp2-1,13,2,4-closo-Co2C2B10H12 (5) and 1,8-Cp2-1,8,2,5-closo-Co2C2B10H12 (6). It is shown that a common alternative method of cage C atom identification, using refined (as B) Ueq values, does not work well, at least in these cases. Having identified the correct isomeric forms of the six dicobaltacarboranes, their syntheses are tentatively rationalised in terms of the direct electrophilic insertion of a {CpCo+} fragment into [CpCoC2B10]− anions and it is demonstrated that compounds 1, 4, 5 and 6 can be successfully prepared by deliberately performing such reactions.

Synthesis, characterization, crystal structure, and DNA binding of two copper(II)–hydrazone complexes

Abstract: Two new Cu(II)–hydrazone complexes, [Cu(L)(Hbpe)ClO4]·ClO4·[Cu(L)Cl] (1) and [Cu(HL)2]·15ClO4·05OH (2) (where HL = (E)-N′-(1-(pyridine-2-yl)ethylidene)benzohydrazide and bpe = trans-1-(2-pyridyl)-2-(4-pyridyl)ethylene), have been synthesized and characterized by physicochemical methods The structures of the complexes have been established by single-crystal X-ray diffraction direct methods, which reveal that the metal ions have distorted square-pyramidal and square-planar geometries in 1, and a distorted octahedral geometry in 2 DNA binding of HL, 1, and 2, performed by UV–vis titration in tris-buffer medium, yielded binding constants, which are 95 × 103, 188 × 104, and 466 × 104 M−1, respectively Viscosity measurements suggest a surface or groove-binding mode of interaction between CT-DNA with HL, 1, and 2

How to Make 8,1,2‐closo‐MC2B9 Metallacarboranes

Abstract: Three examples of the rare 8,1,2-closo-MC2B9 isomeric form of an icosahedral metallacarborane have been isolated as unexpected trace products in reactions. Seeking to understand how these were formed we considered both the nature of the reactions that were being undertaken and the nature of the coproducts. This led us to propose a mechanism for the formation of the 8,1,2-closo-MC2B9 species. The mechanism was then tested, leading to the first deliberate synthesis of an example of this isomer. Thus, deboronation of 4-(η-C5H5)-4,1,8-closo-CoC2B10H12 selectively removes the B5 vertex to yield the dianion [nido-(η-C5H5)CoC2B9H11]2−, oxidative closure of which affords 8-(η-C5H5)-8,1,2-closo-CoC2B9H11 in moderate yield.

Definitive crystal structure of 1,1'-bis-[1,2-dicarba-closo-dodeca-borane(11)].

Abstract: In the title compound, C4H22B20, the two {1,2-closo-C2B10H11} cages are linked across a centre of inversion with a C—C distance of 1.5339 (11) A. By careful analysis of the structure, it is established that the non-linking cage C atom is equally disordered over cage vertices 2 and 3.

Crystal structure of 1,1'-bis[1,7-dicarba-closo-dodeca-borane(11)].

Abstract: In the title compound, C4H22B20, the two {1,7-closo-C2B10H11} cages are linked across a centre of inversion, with C—C = 1.5401 (16) A. The position of the second non-linking cage C atom was established unambiguously by geometric and crystallographic methods and there is no evidence of C/B disorder.