Stabilization of NH- Group Adjacent to Naked Silicon(II) Atom in Base Stabilized Aminosilylenes

Aminosilylene, comprising reactive NH- and Si(II) sites next to each other, is an intriguing class of compounds due to its ability to show diverse reactivity. However, stabilizing the reactive NH- group next to the free Si(II) atom is challenging and has not yet been achieved. Herein, we report the first examples of base stabilized free aminosilylenes Ar*NHSi(PhC(NtBu)2) (1 a) and Mes*NHSi(PhC(NtBu)2) (1 b) (Ar*=2,6-dibenzhydryl-4-methylphenyl and Mes*=2,4,6-tri-tert-butylphenyl), tolerating a NH- group next to the naked Si(II) atom. Remarkably, 1 a and 1 b exhibited interesting differences in their reactivity upon heating. With 1 a, an intramolecular C(sp3)-H activation of one of the benzhydryl methine hydrogen atoms to the Si(II) atom produced the five-membered cyclic silazane 2. However, with 1 b, a rare 1,2-hydrogen shift to the Si(II) atom afforded a silanimine 3, with a hydride ligand attached to an unsaturated silicon atom. Further, the coordination capabilities of 1 a were also tested with Ru(II) and Fe(0) precursors. Treatments of 1 a with [Ru(eta 6-p-cymene)Cl2]2 led to the isolation of a eta 6-arene tethered complex [RuCl2{Ar*NHSi(PhC(tBuN)2)-kappa 1-Si-eta 6-arene}] (4), whereas with the Fe(CO)5 precursor a Fe(0) complex [Fe(CO)4{Ar*NHSi(PhC(tBuN)2)-kappa 1-Si}] (5) was obtained. Density functional theory (DFT) calculations were conducted to shed light on the structural, bonding, and energetic aspects in 1-5. This paper describes the isolation of the first examples of free aminosilylenes 1 a and 1 b having -NH group next to the naked Si(II) atom. Aminosilylenes showed unique reactivity upon heating; an intramolecular C(sp3)-H activation with 1 a afforded cyclic silazane, whereas 1 b showed a rare 1,2-hydrogen shift to afford rare silanimine.image