Synthesis of Boronated Amidines by Addition of Amines to Nitrilium Derivative of Cobalt Bis(Dicarbollide)

Abstract

A series of novel cobalt bis(dicarbollide) based amidines were synthesized by the nucleophilic addition of primary and secondary amines to highly activated B-N⁺≡C-R triple bond of the propionitrilium derivative [8-EtC≡N-3,3'-Co(1,2-C₂B₉H₁₀)(1',2'-C₂B₉H₁₁)]. The reactions with primary amines result in the formation of mixtures of E and Z isomers of amidines, whereas the reactions with secondary amines lead selectively to the E-isomers. The crystal molecular structures of E-[8-EtC(NMe₂)=HN-3,3'-Co(1,2-C₂B₉H₁₀)(1',2'-C₂B₉H₁₁)], E-[8-EtC(NEt₂)=HN-3,3'-Co(1,2- C₂B₉H₁₀)(1',2'-C₂B₉H₁₁)] and E-[8-EtC(NC₅H₁₀)=HN-3,3'-Co(1,2-C₂B₉H₁₀)(1',2'-C₂B₉H₁₁)] were determined by single crystal X-ray diffraction.

Keywords: amidines; cobalt bis(dicarbollide); nitrilium derivatives; nucleophilic addition reactions; structure; synthesis.