om6b00858_si_004.cif (1.83 MB)

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)

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posted on 08.02.2017, 20:45 by Mikhail M. Vinogradov, Yulia V. Nelyubina, Alexander A. Pavlov, Valentin V. Novikov, Nikita V. Shvydkiy, Alexander R. Kudinov
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.