Dataset Information

Synthesis, Electronic Properties and Reactivity of [B₁₂ X₁₁ (NO₂ )]^2- (X=F-I) Dianions.

ABSTRACT: Nitro-functionalized undecahalogenated closo-dodecaborates [B₁₂ X₁₁ (NO₂ )]^2- were synthesized in high purities and characterized by NMR, IR, and Raman spectroscopy, single crystal X-diffraction, mass spectrometry, and gas-phase ion vibrational spectroscopy. The NO₂ substituent leads to an enhanced electronic and electrochemical stability compared to the parent perhalogenated [B₁₂ X₁₂ ]^2- (X=F-I) dianions evidenced by photoelectron spectroscopy, cyclic voltammetry, and quantum-chemical calculations. The stabilizing effect decreases from X=F to X=I. Thermogravimetric measurements of the salts indicate the loss of the nitric oxide radical (NO^. ). The homolytic NO^. elimination from the dianion under very soft collisional excitation in gas-phase ion experiments results in the formation of the radical [B₁₂ X₁₁ O]^2-. . Theoretical investigations suggest that the loss of NO^. proceeds via the rearrangement product [B₁₂ X₁₁ (ONO)]^2- . The O-bonded nitrosooxy structure is thermodynamically more stable than the N-bonded nitro structure and its formation by radical recombination of [B₁₂ X₁₁ O]^2-. and NO^. is demonstrated.

SUBMITTER: Asmis KR

PROVIDER: S-EPMC7756457 | biostudies-literature | 2020 Nov

REPOSITORIES: biostudies-literature

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Publications

Synthesis, Electronic Properties and Reactivity of [B12 X11 (NO2 )]2- (X=F-I) Dianions.

Asmis Knut R KR Beele Björn B BB Jenne Carsten C Kawa Sebastian S Knorke Harald H Nierstenhöfer Marc C MC Wang Xue-Bin XB Warneke Jonas J Warneke Ziyan Z Yuan Qinqin Q

Chemistry (Weinheim an der Bergstrasse, Germany) 20201005 64

Nitro-functionalized undecahalogenated closo-dodecaborates [B12 X11 (NO2 )]2- were synthesized in high purities and characterized by NMR, IR, and Raman spectroscopy, single crystal X-diffraction, mass spectrometry, and gas-phase ion vibrational spectroscopy. The NO2 substituent leads to an enhanced electronic and electrochemical stability compared to the parent perhalogenated [B12 X12 ]2- (X=F-I) dianions evi ...[more]

PMID: 33017100

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Project description:Dianionic nido-[C2B10]2- species are key intermediates in the polyhedral expansion from 12- to 13-vertex carboranes and metallacarboranes, and the isomer adopted by these nido intermediates dictates the isomeric form of the 13-vertex product. Upon reduction and metallation of para-carborane up to five MC2B10 metallacarboranes can be produced (Angew. Chem., Int. Ed., 2007, 46, 6706), the structures of which imply the intermediacy of 1,7-, 3,7-, 4,7-, 7,9- and 7,10-isomers of the nido-[C2B10]2- species. In this paper we use density functional theory (DFT) calculations to characterise the reduction of closo-C2B10H12 carboranes and the subsequent isomerisations of the nido-[C2B10H12]2- dianions. Upon reduction para-carborane initially opens to [1,7-nido-C2B10H12]2- (abbreviated to 1,7) and [4,7-nido-C2B10H12]2- (4,7) and isomerisation pathways connecting 1,7 to 7,9, 4,7 to 7,10 and 1,7 to 3,7 have been characterised. For ortho- and meta-carborane the experimental reduction produces 7,9 in both cases and computed pathways for both processes are also defined; with ortho-carborane rearrangement occurs via7,8, whereas with meta-carborane 7,9 is formed directly. The 7,9 isomer is the global minimum nido-structure. The characterisation of these isomerisation processes uncovers intermediates that adopt new structural motifs that we term basket and inverted nido. Basket intermediates feature a two-vertex basket handle bridging the remaining 10 vertices; inverted nido intermediates are related to known nido species, in that they have 5- and 6-membered belts, but where the latter, rather than the former, is capped, leaving a 5-membered open face. These new intermediates exhibit similar stability to the nido species, which is attributed to their relation to the 13-vertex docosahedron through the removal of 5-connected vertices. Isomerisation pathways starting from nido geometries are most often initiated by destabilisation of the cluster through a DSD process causing the 3-connected C7 vertex to move into a 4-connected site and a neighbouring B vertex to become 3-connected. The ensuing rearrangement of the cluster involves processes such as the pivoting of a 4-vertex diamond about its long diagonal, the pivoting of two 3-vertex triangles about a shared vertex and DSD processes. These processes are all ultimately driven by the preference for carbon to occupy low-connected vertices on the open 6-membered face of the resulting nido species.

Dataset Information

Synthesis, Electronic Properties and Reactivity of [B₁₂ X₁₁ (NO₂ )]^2- (X=F-I) Dianions.

Publications

Synthesis, Electronic Properties and Reactivity of [B<sub>12</sub> X<sub>11</sub> (NO<sub>2</sub> )]<sup>2-</sup> (X=F-I) Dianions.

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