Donor–Acceptor Stabilized Tetra(silanimine)

The synthesis of an oligo­(silanimine) is described. The reaction of the amidinato silylene [LSiN­(SiMe₃)₂] (<b>1</b>, L = PhC­(N<i>t</i>Bu)₂) with SiI₄ in toluene afforded a mixture of the silanimine [LSi­(I)­NSiI₃] (<b>2</b>), SiMe₃I, and Si₂I₆. The mechanistic studies showed that <b>1</b> reacts with SiI₄ to form the silyl ionic intermediate “{LSi­(I)­N­(SiMe₃)₂}⁺{SiI₃}⁻”, which then eliminates SiMe₃I and “SiI₂” to form the silanimine intermediate “LSi­(I)­NSiMe₃”. It further undergoes a substitution with another molecule of SiI₄ to form a mixture of <b>2</b> and SiMe₃I. In addition, “SiI₂” undergoes an oxidative addition with SiI₄ to form Si₂I₆. Subsequently, compound <b>2</b> reacted with [LiN­(SiMe₃)­Ar] to form the silanimine [LSi­(I)­NSiI₂N­(SiMe₃)­Ar] (<b>6</b>, Ar = 2,6-<i>i</i>Pr₂C₆H₃), which was then treated with KC₈ to give the donor–acceptor stabilized tetra­(silanimine) [LSiN­(SiMe₃)­SiNAr]₂ (<b>7</b>). It comprises four formal silanimine “>SiN-” units, which are linked together. Compounds <b>2</b>, <b>6</b>, and <b>7</b> were characterized by NMR spectroscopy and X-ray crystallography

B–H Bond Activation by an Amidinate-Stabilized Amidosilylene: Non-Innocent Amidinate Ligand

The activation of B–H and B–Cl bonds in boranes by base-stabilized low-valent silicon compounds is described. The reaction of the amidinato amidosilylene–borane adduct [L­{Ar­(Me₃Si)­N}­SiBH₃] [<b>1</b>; L = PhC­(N<i>t</i>Bu)₂, and Ar = 2,6-<i>i</i>Pr₂C₆H₃] with MeOTf in toluene at room temperature formed [L­{Ar­(Me₃Si)­N}­SiBH₂OTf] (<b>2</b>). [LSiN­(SiMe₃)­Ar] in compound <b>2</b> then underwent a B–H bond activation with BH₂OTf in refluxing toluene to afford the B–H bond activation product [LB­(H)­Si­(H)­(OTf)­{N­(SiMe₃)­Ar}] (<b>3</b>). On the other hand, when compound <b>2</b> was reacted with 4-dimethylaminopyridine in refluxing toluene, another B–H bond activation product [(μ-κ1:κ1-L)­B­(H)­(DMAP)­Si­(H)­{N­(Ar)­SiMe₃}]­OTf (<b>4</b>) was afforded. Mechanistic studies show that “(μ-κ1:κ1-L)­B­(H)­(OTf)­Si­(H)­{N­(Ar)­SiMe₃}” (<b>2A</b>) is the key intermediate in the reactions mentioned above. The formation of <b>2A</b> is further evidenced by the activation of the B–Cl bond in PhBCl₂ by the amidinato silicon­(I) dimer [LSi:]₂ to form the B–Cl bond activation product [(μ-κ1:κ1-L)­B­(Cl)­(Ph)­Si­(Cl)]₂ (<b>6</b>). Compounds <b>2–4</b> and <b>6</b> were characterized by nuclear magnetic resonance spectroscopy and X-ray crystallography