Acyl chloride carbon insertion into dicarbaborane cages – new route to tricarbollide cages

Abstract

Reactions between the arachno-6,9-C 2 B 8 H 14 dicarbaborane and acyl chlorides, RCOCl, in the presence of amine bases in CH 2 Cl 2 , followed by acidification with conc. H 2 SO 4 at 0 °C, generate in high yields a series of neutral alkyl and aryl tricarbollides of structure 8-R-nido-7,8,9-C 3 B 8 H 11 (where R = alkyls and aryls). These skeletal alkylcarbonation (SAC) reactions are consistent with an aldol-type condensation between the RCO group and open-face dicarbaborane hydrogen atoms, which is associated with the insertion of the acyl chloride RC unit into the structure under elimination of three extra hydrogen atoms as H 2 O and HCl. The reactions thus result in an effective cross-coupling between R and the tricarbollide cage. High-temperature reactions between 8-Ar-nido-7,8,9-C 3 B 8 H 11 (where Ar = Ph, 1-C 10 H 7 , and 2-C 10 H 7 ) compounds and [CpFe(CO) 2 ] 2 produced the first types of monoaryl substituted twelve-vertex ferratricarbollide complexes of general constitution [1-(CpFe)-closo-ArC 3 B 8 H 10 ] with three different arrangements of cluster carbon vertexes. The Fe-complexation is accompanied by extensive rearrangement of the cluster carbon atoms over the twelve-vertex cage and the complexes isolated can be regarded as ferrocene analogues.