Carbon?Halogen Bond Activation with Powerful Heavy Alkaline Earth Metal Hydrides

Reaction of [(DIPePBDI)SrH]2 with C6H5X (X=Cl, Br, I) led to hydride-halogenide exchange (DIPePBDI=HC[(Me)CN-2,6-(3-pentyl)phenyl]2). Conversion rates increase increasing halogen size (F<Cl<Br<I). C6H5F was slow and ill-defined but addition C6H4F2 gave smooth hydride-fluoride exchange. After THF the full range Sr halogenides structurally characterized: [(DIPePBDI)SrX ? THF]2 (X=F, Cl, I). Mixtures AeN“2 PhSiH3 in situ formed less defined more robust Ae metal hydride clusters (AexN”yHz, Ae=Ca, Sr, Ba N“=N(SiMe3)2) which are able hydrodefluorinate C6H5F. (Ca<Sr<Ba). Also alkylfluorides (1-F-hexane, F-cyclohexane, 1-F-adamantane) could be converted but, due solubility problems species, fastest conversion found for Sr. These AeN”2/PhSiH3 mixtures also SF6 at room temperature give undefined decomposition products. Addition Me6Tren a SrN“2/PhSiH3 crystallization [Sr6N”2H9 (Me6Tren)3+][SrN“3?]; Me6Tren=tris[2-(dimethylamino)ethyl]amine). hydrodefluorination, Sr6N”4F8 (Me6Tren)2 characterized. Dissolution cluster growth larger Sr16N“8F24 (THF)12 is DFT calculations support that hydrodehalogenation halobenzenes follows concerted nucleophilic aromatic substitution mechanism (cSNAr).