Synthesis and characterisation of a novel nickel trihydride. Crystal structure of [{Ni(dippe)}2H3][BPh4](dippe = Pri2PCH2CH2PPri2)

Abstract

The reaction of anhydrous NiBr₂ with 1,2-bis(diisopropylphosphino)ethane (dippe) in ethanol yielded the orange complex [NiBr₂(dippe)]1. This compound reacted with NaBH₄ in ethanol to yield the dimeric trihydride [{Ni(dippe)}₂H₃]⁺, isolable as its tetraphenylborate salt 2a, for which the crystal structure has been determined. The structure suggests that there is one bridging hydride, the other two (one attached to each Ni) being terminal. An analogous complex containing the bulky phosphine 1,2-bis(dicyclohexylphosphino)ethane has also been prepared. These binuclear trihydrides are non-rigid and undergo rapid scrambling of the hydride ligands in solution even at –85 °C. All the compounds were characterised by IR and NMR spectroscopy and microanalysis.