Air-stable nickel(II) borohydrides as prohydrides: Reactions with halocarbons and aerial carbon dioxide

Abstract

Non-noble metal hydrides are highly attractive reagents owing to their involvement in the reactions of environmental and industrial interest. However, they are often cumbersome to isolate as a shelf-stable reagent. Herein, we have described the synthesis of non-noble metal hydrides by simple manual grounding of Ni(II)-chelates and NaBH4 in open air at room temperature without using organic solvents. Two nickel(II) complexes of tetradentate N4 ligands, [(LNHCy)Ni(CH3CN)(H2O)](ClO4)2 and [(tren)Ni(CH3CN)2](BPh4)2, were synthesized and their solid-state structures were confirmed by single crystal X-ray diffraction studies. Both the nickel complexes were manually ground with sodium borohydride in open air to produce corresponding nickel(II)-borohydrides that were characterized using FT-IR spectroscopy and powder X-ray diffraction techniques. Further, the borohydrides (prohydrides) activate the C-X bond in benzyl bromide, CDCl3, trityl chloride and iodobenzene to yield toluene, CHDCl2, triphenylmethane and benzene; the borohydrides reacted with trityl cation and air in acetonitrile solution to yield triphenylmethane and carbonate.