Mapping the pathway of heteroborane isomerisation: Two parallel “1,2→1,7” isomerisations of a crowded molybdacarborane and the isolation of isomerisation intermediates

McIntosh, Ruaraidh D.; Ellis, David; Giles, Barry T.; Macgregor, Stuart A.; Rosair, Georgina M.; Welch, Alan J.

doi:10.1016/j.ica.2006.01.023

Cited by 16 publications

(5 citation statements)

References 48 publications

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“…C-atom isomerised species of (Z-C 7 H 7 )MoPh 2 C 2 B 9 H 9 have also been isolated. 16 DFT calculations showed that these Mo-based metallacarboranes showed a room temperature isomerization route similar to that observed for the hightemperature isomerization of the C x B x carborane from 1.2 to 1.7.…”

Section: A2 Metallacarboranes With Icosahedral Carborane Clusterssupporting

confidence: 66%

Metallacarboranes and their interactions: theoretical insights and their applicability

et al. 2012

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Section: A2 Metallacarboranes With Icosahedral Carborane Clusterssupporting

confidence: 66%

Metallacarboranes and their interactions: theoretical insights and their applicability

et al. 2012

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“…The intermediate formed ( IM ) has a boat conformation of the upper C 2 B 4 belt and η 6 -coordination of the rhodium atom. A few examples of similar complexes with η 6 -coordination of a metal atom are known in the literature, moreover, they were shown to be intermediates in cage rearrangements of icosahedral molybdacarboranes . The second step of the reaction ( IM → 4 ) has a significantly lower barrier ( TS2 : Δ H ⧧ = 17.3 kcal/mol) and could be most easily rationalized by a single 90° rotation of the B7–C3 edge of the intermediate IM (Scheme ).…”

Section: Results and Discussionmentioning

confidence: 99%

Polyhedral Rearrangements in the Complexes of Rhodium and Iridium with Isomeric Carborane Anions [7,8-Me₂-X-SMe₂-7,8-nido-C₂B₉H₈]⁻ (X = 9 and 10)

et al. 2017

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Polyhedral rearrangement of iridacarborane 1,2-Me2-3,3-(cod)-4-SMe2-3,1,2-closo-IrC2B9H8 (1) proceeds in a solution at RT and affords a product of 1,2 → 1,7 isomerization 1,8-Me2-2,2-(cod)-7-SMe2-2,1,8-closo-IrC2B9H8 (2). Rhodium derivative 1,2-Me2-3,3-(cod)-4-SMe2-3,1,2-closo-RhC2B9H8 (3) is significantly more stable toward heating than iridium complex 1 and isomerizes at 110 °C by 1,2 → 1,2 and 1,2 → 1,7 reaction schemes with 1,2 → 1,2 being the predominant route forming 1,2-Me2-4,4-(cod)-8-SMe2-4,1,2-closo-RhC2B9H8 (4) and 1,8-Me2-2,2-(cod)-7-SMe2-2,1,8-closo-RhC2B9H8 (5). Complexes 4 and 5 were characterized by 11B{1H}–11B{1H} COSY NMR spectrometry. A mechanism of 1,2 → 1,2 isomerization of 3 to 4 was proposed on the basis of DFT calculations. Reaction of the thallium salt Tl[7,8-Me2-9-SMe2-7,8-nido-C2B9H8] (CarbTl) with [Cp*RuCl]4 in THF furnishes new ruthenacarborane 1,2-Me2-3-(Cp*)-4-SMe2-3,1,2-closo-RuC2B9H8 (6). Heating of 6 at 80 and 144 °C leads to the partial and complete decomposition, respectively. Interaction of CarbTl with [Cp*IrCl2]2 in the presence of TlPF6 provides two new Ir(III) complexes [1,2-Me2-3-(Cp*)-4-SMe2-3,1,2-closo-IrC2B9H8]PF6 (7PF6) and 1,2-Me2-3-(Cp*)-4-SMe-3,1,2-closo-IrC2B9H8 (8) both stable upon heating in boiling tetrachloroethane (146 °C). A new 10-substituted charge-compensated carborane [7,8-Me2-10-SMe2-7,8-nido-C2B9H9] (9) was synthesized via an interaction of dicarbollide dianion [7,8-Me2-7,8-nido-C2B9H9]2– with dimethyl sulfide and acetaldehyde in acidic media. Thallium salt of 9 Tl[7,8-Me2-10-SMe2-7,8-nido-C2B9H8] (10) reacts with [(cod)IrCl]2 furnishing positional isomer of 1 with a symmetrical emplacement of SMe2 substituent complex 1,2-Me2-3,3-(cod)-8-SMe2-3,1,2-closo-IrC2B9H8 (11). Iridacarborane 11 requires elevated temperatures to undergo cage isomerization and converts upon heating at 110 °C to two new compounds 1,8-Me2-2,2-(cod)-11-SMe2-2,1,8-closo-IrC2B9H8 (12) and 1,2-Me2-4,4-(cod)-9-SMe2-4,1,2-closo-IrC2B9H8 (13) as a result of 1,2 → 1,7 and 1,2 → 1,2 rearrangements respectively with 13 being the minor product. The structures of 2, 6, 7PF6, 8, 10, 12, and 13 were determined by single-crystal X-ray diffraction.

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“…Knowledge of how molecular rearrangement might affect macroscale properties is therefore essential. Complexation of metals by carboranes appears to lower the rearrangement barrier to ambient conditions, 7,8 affecting their macroscale properties. 6 There have been several theoretical 9 and experimental 7,10-12 investigations into the mechanisms of rearrangement.…”

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confidence: 99%

Thermal rearrangement mechanisms in icosahedral carboranes and metallocarboranes

2013

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Ab initio MD and potential energy surface sampling has been used to study the rearrangement processes in carboranes and their derivatives. A new mechanism is found, in addition to those previously proposed. The fact that theoretical activation energies are lower than those observed experimentally, and the differing activity of technetium and rhenium complexes, are rationalised by orbital symmetry constraints.

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Mapping the pathway of heteroborane isomerisation: Two parallel “1,2→1,7” isomerisations of a crowded molybdacarborane and the isolation of isomerisation intermediates

Cited by 16 publications

References 48 publications

Metallacarboranes and their interactions: theoretical insights and their applicability

Metallacarboranes and their interactions: theoretical insights and their applicability

Polyhedral Rearrangements in the Complexes of Rhodium and Iridium with Isomeric Carborane Anions [7,8-Me₂-X-SMe₂-7,8-nido-C₂B₉H₈]⁻ (X = 9 and 10)

Thermal rearrangement mechanisms in icosahedral carboranes and metallocarboranes

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Mapping the pathway of heteroborane isomerisation: Two parallel “1,2→1,7” isomerisations of a crowded molybdacarborane and the isolation of isomerisation intermediates

Cited by 16 publications

References 48 publications

Metallacarboranes and their interactions: theoretical insights and their applicability

Metallacarboranes and their interactions: theoretical insights and their applicability

Polyhedral Rearrangements in the Complexes of Rhodium and Iridium with Isomeric Carborane Anions [7,8-Me2-X-SMe2-7,8-nido-C2B9H8]− (X = 9 and 10)

Thermal rearrangement mechanisms in icosahedral carboranes and metallocarboranes

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Polyhedral Rearrangements in the Complexes of Rhodium and Iridium with Isomeric Carborane Anions [7,8-Me₂-X-SMe₂-7,8-nido-C₂B₉H₈]⁻ (X = 9 and 10)