Alternative syntheses and X-ray diffraction analyses of the parent tricarbaborane compounds [nido-7,8,9-C3B8H11]−, [nido-7,8,10-C3B8H11]− and [1-(η5-C5H5)-closo-1,2,4,10-FeC3B8H11]

Reaction of the neutral tricarbaborane nido-7,8,9-C3B8H12 (1) with triethylamine in CH2Cl2 led to quantitative deprotonation and isolation of the corresponding Et3NH+ salt of the [nido-7,8,9-C3B8H11]− anion (2). This was converted into PSH+ and Me4N+ salts via metathetic cation exchange. Heating of the solid Me4N+[7,8,9-C3B8H11]− in mineral oil at 350 °C for 2 h resulted in thermal rearrangement and isolation of the cage isomeric compound Me4N+[7,8,10-C3B8H11]−. Finally, compound 1 was directly complexed via reaction with [CpFe(CO)2]2 (Cp = η5-C5H5) to generate the ferratricarbollide sandwich [1-Cp-closo-1,2,4,10-FeC3B8H11] (4) in 60% yield. The structures of all the generic compounds of tricarbollide chemistry, 1 (PSH+ salt), 2 (MePPh3+salt), and 4, were established unambiguously by an X-ray diffraction analysis.