Synthesis of Aminosilane Chemical Vapor Deposition Precursors and Polycarbosilazanes through Manganese-Catalyzed Si–N Dehydrocoupling

Compounds that feature Si–N
bonds are of widespread importance
to the electronics and coating industries. Aminosilanes and polysilazanes
are currently prepared by adding amines to halosilanes, an inefficient
methodology that generates stoichiometric quantities of ammonium salt
waste. Herein, we describe the syntheses of aminosilane chemical vapor
deposition precursors, polycarbosilazanes, and perhydropolysilazane
through the ambient-temperature dehydrocoupling of amines to silane
(SiH4). Specifically, the β-diketiminate manganese
hydride dimer [(2,6‑iPr2PhBDI)­Mn­(μ-H)]2 has been used to catalyze the formation of commercial aminosilane
monomers from secondary and primary amines, highly cross-linked polycarbosilazane
powders from diamines and triamines, and perhydropolysilazane from
ammonia. The mechanism of dehydrocoupling was explored, and the addition
of isopropylamine to [(2,6‑iPr2PhBDI)­Mn­(μ-H)]2 resulted in σ-bond metathesis
to eliminate H2 and generate [(2,6‑iPr2PhBDI)­Mn­(μ-NHiPr)]2. In the presence of SiH4, H–Si addition
across newly formed Mn–N bonds regenerates the precatalyst,
offering a straightforward catalytic cycle for halogen-free Si–N
bond formation.