"Click"-Like η6 -Metalation/Demetalation of Aryl Iodides as a Means of Turning "ON/OFF" Halogen Bond Donor
Andrew W Kelly1, K Travis Holman1
1Department of Chemistry, Georgetown University, Box 571227, Washington, DC 20057, USA.
Abstract:
η6 -Metalated aryl halides are recognized as a class of halogen bond (XB) donors. Click-like η6 -metalation/demetalation of aryl iodides by cyclopentadienylruthenium(II) ([CpRuII ]+ ) is shown to turn ON/OFF (amplify/suppress) XB donor functionality. [CpRu(MeCN)3 ][PF6 ] is shown to react quantitatively with iodobenzenes (ArIn , n=1,2) to yield [CpRu(η6 -ArIn )][PF6 ] compounds. Photochemical demetalation (405 nm) quantitatively reverts these compounds to ArIn and [CpRu(MeCN)3 ][PF6 ]. Crystal structures of [CpRu(ArXn )]+ salts show that the [CpRu(ArIn )]+ cations are strong, charge-assisted XB donors analogous to iodopyridinium cations. XB-induced association of [CpRu(C6 H5 I)]+ with diazobicyclo[2.2.2]octane (DABCO) is established by NMR spectroscopy. [CpRu(C6 H5 I)][BPh4 ] and [CpRu(1,4-C6 H4 I2 )][BPh4 ] co-crystallize with DABCO and the structure of [CpRu(1,4-C6 H4 I2 )][BPh4 ]⋅DABCO⋅Et2 O is reported. DFT calculations support amplification of the XBing capabilities of aryl iodides upon [CpRu]+ -metalation.
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