Synthesis, Structural Analysis, and Functional Group Interconversion in the [closo-B₁₀H₈-1,10-X₂]^2– (X = CN, [OCRNMe₂]⁺, OCOR, and [OH₂]⁺) Derivatives

Derivatives [closo-B₁₀H₈-1,10-(CN)₂]^2– and [closo-B₁₀H₈-1,10-(OCHNMe₂)₂], efficiently obtained from [closo-B₁₀H₈-1,10-(IPh)₂] by nucleophilic substitution with CN^– and DMF, were envisioned as precursors to diacid [closo-B₁₀H₈-1,10-(COOH)₂]^2– and to dihydroxy derivative [closo-B₁₀H₈-1,10-(OH)₂]^2–, respectively. Attempts at hydrolysis or reduction of the dinitrile gave no reaction or complex mixtures of products. In contrast, the DMF adduct was cleanly hydrolyzed to diformate [closo-B₁₀H₈-1,10-(OCHO)₂]^2– and subsequently to protonated dihydroxy [closo-B₁₀H₈-1,10-(OH₂)₂]. The latter was O-acylated with PhCOCl. Crystal and molecular structures of five derivatives were established by single crystal XRD methods and compared to those for other [closo-B₁₀H₈-1,10-X₂]^2– derivatives. Trends in molecular geometry in the series and also reactivity of the dinitrile and intermediates were corroborated and correlated with DFT results (B3LYP/TZVP) by analysis of bonding, charge distribution and vibrational frequencies.