Stabilisation of a Strontium Hydride with a Monodentate Carbazolyl Ligand and its Reactivity

The molecular strontium hydride 2 [(${}^{dtbp}$Cbz)SrH(L)]${}_2$ (L=benzene, toluene) was isolated and stabilized by employing a sterically demanding carbazole ligand (${}^{dtbp}$Cbz=1,8-bis(3,5-ditertbutylphenyl)-3,6-ditertbutylcarbazolyl). Compound 2 was synthesized via phenylsilane metathesis with the corresponding amide (${}^{dtbp}$Cbz)SrN(SiMe${}_3$)${}_2$ and characterized by ${}^1$H NMR, XRD and vibrational spectroscopy methods. We further investigated the stoichiometric reactivity of 2 towards carbon monoxide, azobenzene and trimethylsilylacetylene, showing three distinct reactivity pathways: addition, reduction and deprotonation. The reaction of 2 with carbon monoxide yields the ethenediolate complex 4 via addition, while with azobenzene reduction of the N−N double bond and release of hydrogen were observed, affording a heteroleptic strontium complex with a radical azobenzenyl ligand (5). The terminal alkyne is deprotonated by the hydride moiety to give the acetylide complex 6.