The cleavage of diborane was presented in a recent lecture, and it was said that the borane could be cleaved unsymmetrically if sterics allowed, or symmetrically if they did not, as shown in the image below:
However, no mechanism for this cleavage was provided, nor can it be found in Housecroft and Sharpe's "Inorganic Chemistry", our course textbook, nor can I find much about it online.
I have postulated such a mechanism:
Is it known how this cleavage occurs, and if it does indeed follow this mechanism? Is my attempt a reasonable proposition?