Reversible stereospecific extrusion of ethylene from a 1,2-diosmacyclobutane. Determination of stereochemistry by liquid-crystal NMR

The authors now report that the loss of ethylene from (..mu..-1,2-ethanediyl)octacarbonyldiosmium (1) is stereospecific. In a reaction analogous to the desorption of an olefin from a metal surface, undergoes facile ethylene loss. As 1 is related to cyclobutane by the isolobal analogy between Os(CO)/sub 4/ and CH/sub 2/, the loss of ethylene from 1 can be compared to the fragmentation of cyclobutane into two ethylenes - a classic example of a reaction forbidden by orbital symmetry as a concerted process. One would, therefore, expect the loss of ethylene from 1 to be forbidden as a concerted process and to occur by a diradical mechanism leading to loss of stereochemistry.