Tricyanomethane or Dicyanoketenimine-Silylation makes the Difference

Area of Science:

• Organometallic Chemistry
• Pseudohalide Chemistry
• Synthetic Chemistry

Background:

• Pseudohalides, like tricyanomethanide [C(CN)3]-, are versatile chemical species.
• Protonated HC(CN)3 is a very strong acid but unstable, prone to decomposition.
• Silylated compounds offer enhanced kinetic stability compared to protonated analogues.

Purpose of the Study:

• To investigate the stepwise silylation of the tricyanomethanide anion [C(CN)3]-.
• To synthesize and characterize novel silylated pseudohalide compounds.
• To explore the reactivity and structural properties of these new species.

Main Methods:

• Stepwise silylation reactions of [C(CN)3]-.
• Synthesis of [Me3Si][C(CN)3] and the dicationic species [(Me3Si-NC)3C]2+ as a [B(C6F5)4]- salt.
• Quantum chemical calculations for thermodynamic and bonding analysis.

Main Results:

• Silylation of [C(CN)3]- occurs at terminal nitrogen atoms, not the central carbon.
• Formation of the dicyanoketenimine [Me3Si-NC-C(CN)2] as the initial product.
• Generation of the highly symmetrical dication [(Me3Si-NC)3C]2+.

Conclusions:

• Silylation provides a kinetically stabilized alternative to protonation for pseudohalides.
• The regioselectivity of silylation at nitrogen atoms is a key finding.
• The synthesized dicationic species represents a novel and intriguing molecular structure.