Attempts toward a Silyl-Stabilized Dicoordinate Borylene: Insertion of Carbon Dioxide into the B-Si Bond.

One-electron reduction of the carbene-stabilized borane (Me-cAAC)B(Cl)Si(SiMe), , with potassium naphthalenide gave the radical (Me-cAAC)B(Cl)Si(SiMe), . A subsequent one-electron reduction of yielded the dicoordinate borylene (Me-cAAC)BSi(SiMe), , which rapidly underwent intramolecular C-H activation to give cyclo-(Me-cAAC)B(H)Si(SiMe), , irrespective of the employed reaction conditions. Compound could be stabilized as the carbonyl complex (Me-cAAC)B(CO)Si(SiMe), , that gave upon irradiation with a UV light under a CO atmosphere. In contrast, the two-electron reduction of under an atmosphere of CO yielded a mixture of products of which (Me-cAAC)B(Cl)(H)C(O)OSi(SiMe), , could be separated and structurally characterized. Compound is a rare example of CO insertion into a B-E (E = heavier main group element) bond in which boron functions as a nucleophile, thereby mimicking transition metal-mediated carboxylation. The mechanism for the formation of from the purported boryl anion intermediate [(Me-cAAC)B(Cl)Si(SiMe)], , was analyzed computationally.