Diverse Reactivity of Amidinate-Supported Boron Centers with the Hypersilyl Anion and Access to A Monomeric Secondary Boron Hydride: data

Diverse reactivity of the bulky tris(trimethylsilyl)silyl substituent [Si(SiMe₃)₃], also known as the hypersilyl group, was observed for amidinate supported dichloro- and phenylchloroborane complexes. Treatment of the dichloroborane with potassium tris(trimethylsilyl)silyl led to the activation of backbone β-carbon center and formation of saturated four-membered heterocyclic chloroboranes Rʹ{Si(SiMe₃)₃}C(NR)₂BCl (Rʹ = Ph, R = Cy (3); Rʹ = Ph, R = iPr (6); (Rʹ = tBu, R = Cy (8)), whereas the four-membered amidinate hypersilyl substituted phenyl borane 4 [PhC(NCy)₂B(Ph){Si(SiMe₃)₃}] was observed for the case of an amidinate supported phenylchloroborane. The highly deshielded ¹¹B NMR spectroscopic resonance and the distinct difference in ²⁹Si NMR spectrum confirmed the presence of a σ-donating hypersilyl effect on compounds 3, 6 and 8. Reaction of 3 with the Lewis acid AlCl₃ led to the formation complex 11 in which an unusual cleavage of one of the C–N bonds of the amidinate backbone is observed. Nucleophilic substitution at the boron center of saturated chloroborane 3 with phenyllithium generated phenylborane derivative 12, whereas the secondary monomeric boron hydride 13 was observed after treatment with alane (AlH₃). All compounds (2‒13) have been fully characterized by NMR spectroscopic and single-crystal X-ray structure determination studies. The experimental procedures, characterization data and computational data is provided here.

Research results basec upon these data are published at http://doi.org/10.1021/acs.inorgchem.4c00612