“Click”‐Like η6‐Metalation/Demetalation of Aryl Iodides as a Means of Turning “ON/OFF” Halogen Bond Donor Functionality

摘要

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)3PF6 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)3PF6. 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(C6H5I)+ with diazobicyclo2.2.2octane (DABCO) is established by NMR spectroscopy. CpRu(C6H5I)BPh4 and CpRu(1,4‐C6H4I2)BPh4 co‐crystallize with DABCO and the structure of CpRu(1,4‐C6H4I2)BPh4?DABCO?Et2O is reported. DFT calculations support amplification of the XBing capabilities of aryl iodides upon CpRu+‐metalation.