u-vinylidene and n-1-cyclopropenyliron complexes :

Abstract

The reaction chemistry of the bridging vinylidene iron dimers was explored and the chemistry of the double bond proved to be the most fertile. The bridging vinylidene was converted to the bridging alkylidene by protonation followed by reduction.

The unusual conversion of a series of substituted 1,1-dichlorocyclopropenes into a series of substituted bridging vinylidene iron dimers via 1,3-bond cleavage of the cyclopropyl ring during the phase transfer catalyzed reaction of ((mu)-CO) (eta)('5)-cyclopentadienyliron carbonyl dimer, OH('-), and the 1,1-dichlorocyclopropane was mechanistically investigated. Two probable intermediates, substituted 1-chlorocyclopropane substituted (1-((eta)('5)-cyclopentadienyl) (dicarbonyl)iron)-1-cyclopropenes were synthesized and characterized.

The removal of a hydride on C-3 of the 1-((eta)('5)-cyclopentadienyl) dicarbonyliron-1-cyclopropene forms the metalated-cyclopropenium salt. This cyclopropenium salt could then be reacted with a nucleophilic copper reagent to form new 1-(eta)('5)-cyclopentadienyl(dicarbonyl)iron-1-cyclopropene.

The chemistry of the intermediate 1-((eta)('5)-cyclopentadienyl(dicarbonyl)iron)-1-cyclopropene was investigated. The reaction of the double bond has two competing processes, addition versus ring opening. The reaction with tetracyanoethylene forms a bicyclic addition product resulting from the direct addition of tetracyanoethylene across the double bond. The reaction with H('+) is substitution dependent. The protonation of the unsubstituted 1-((eta)('5)-cyclopentadienyl)(dicarbonyl)iron-1-cyclopropene apparently forms the cyclopropyl carbene, while the substituted 1-((eta)('5)-cyclopentadienyl)dicarbonyl-iron-1-cyclopropene rearrange to form the cationic allene complex.