Some comments on the mechanism of the preparation of (Et4N)2B10H10 by thermolysis of Et4NBH4

The volatile intermediate Et₃NBH₃ was isolated during the thermolysis of Et₄NBH₄ at 185°C for 16 hr under dynamic vacuum. The rate of decomposition of Et₄NBH₄ was studied. Separate thermolyses of Et₄NBH₄ (or Et₃NBH₃) with closo B₉H₉^2?nido B₉H^?₁₂, or arachno B₉H₁₄^? did not produce B₁₀H₁₀^2? as the major product. These results are inconsistent with the “build-up” mechanism previously proposed for the thermolytic convertion of BH ₄^? to B₁₀H₁₀^2? and a new mechanism is required.