Attempts at generating metathesis-active Fe(IV) and Co(IV) complexes via the reactions of (silox) 2 M(THF) 2, [(silox) 3 M][Na(THF) 2 ] (M = Fe, Co), and related species with propellanes and triphenylboron

Metathetical syntheses of (silox) 2 M(THF) 2 ( 1 -M, Fe, Co), [(silox) 3 M]Na(THF) 2 ( 2 -M, Fe, Co), and (silox) 3 Fe(THF) ( 3 ) are presented, as are X-ray structural studies of 1 -Co, 2 -Fe, and 2 -Co. Exposure of these complexes to 1.1.1-propellane ( 111P, C 5 H 6 ) and 1,3-dehydroadamantane ( AdP ), which are known progenitors of ROMP-active alkylidenes with ruthenium, failed to elicit similar reactivity. A total of 28 complexes were subjected to 111P in attempts to make “Fe(IV)” alkylidenes capable of some form of olefin metathesis with no success. At best, catalytic ring-opening to 3- exo -methylene cyclobutylidene was evidenced. The addition of triphenylboron as a Lewis acid failed to aid in metal complex formation of the propellanes, but an unusual rearrangement of AdP was noted. In addition, 2 -Fe catalyzed the conversion of 111P to 3- exo -methylene cyclobutylidene, which added twice to Ph 3 B, affording a structurally characterized product, Ph(κ-CH=CMeCH 2 BPh( c C 4 H 4 -1-Ph,3-CH 2 ) ( 4 ), which features cyclobutyl-ring-opening, migration, and phenyl migration.