Some dienyl complexes of iron

The work is based on the fast that cyclohexadiene and cycloheptadiene may be bonded to the transition metals like cyclopentadiena by losing one hydrogen atom to give the respective dienyl complexes. It is mainly concerned with studies of six and seven membered rings forming dienyl complexes with iron. Tricarbonyl-cyclohexadienyl iron II O6H7Fe(CO)3 and trioarbonyl-cycloheptadienyliron C7H9Fe(CO)3, (cations), iso-electronic with tricarbonyl cyclohexadienylmanganese(O), were treated with different nucleophilic agents, while efforts have also been made to prepare 'sandwich' type dienyl complexes of iron by nucleophilic hydride ion attack on cationic arena complexes. Tricarbonyl-cycloheptadienyliron(II) tetrafluoroborate reacts with potassium iodide to give iododicarbonyl-cycloheptadienyliron. This known neutral compound gave tetracarbonyl-di-cycloheptadienyldiiron when treated with sodium. The related bridged compound, i.e. tetracarconyk- cyclohoptadienyl-cyclopentadienyl-di-iron was obtained by reaction of the same iodide with sodium cyclopentadienide. Cyanide ion also replaced the iodine and yielded cyanodicarbonyl-cycloheptadienyliron. The reactions were applied to tricarbonyl-cyclohexadienyliron (II) tetrafluoroborate. They gave iodo-dicerbonyl-cyolohexadienylron which was further treated with sodiun amalgam giving tetracarbonyl-di-cyclohexadienyl-di-iron, with sodium cyclopentadienide yielding tetracarbonyl cyclohexadienyl-cyclopentadienyl-di-iron and with potassium cyanide giving cyanodicarbonyl-cyclohexadienyliron. In an attempt to find out the electrophilicity of the ligand, tricarbonyl-cyclohexadienyliron(II) tetrafluoroborate was reacted with phenyl-lithium, under different conditions. It gave only tetracarbonyl-di-cyclohexadienyl-di-iron and an unstable oil. This oil yielded tricarbonyl-cyolohexadienyliron(II) tetrafluoroborate on reaction with tritylfluoroborate. Further reactions of the cations with sodium methoxide and with the sodium salt of diethyl malonate afforded tricarbonyl-methoxy-cyclohexa-1,3-diene iron and tricarbonyl-di (ethoxylcarbonyl)methyl-cyclohexa-1,3-diene iron respectively. The same cation when treated with potassium cyanide in acetone gave tricarbonyl-cyanoeyclohexa-1,3-diene-iron. All the above-mentioned nucleophiles are abstracted by trityl fluoroborate except the di(ethoxycarbonyl) methyl group. The same reaction scheme was followed with tricarbonyl-cyclo-heptadienyliron(II) tetrafluoroborate in the preparations of tricarbonyl-ethoxycyclohepta-1,3-diene iron, tricarbonyl (ethoxycarbonyl)methyl-cyclo heptadiena-iron and cyanocyclohepta-1,3-diene-iron. The structure of all these compounds have been fully discussed. Iododioarbonyl-cycloheptadenyliron when refluxed in mesitylene in the presence of aluminium chloride gave the cycloheptadienyl-mesitylene-iron cation isolated as a reineckate and hexafluorophosphate. The di-mesityleneiron cation was reduced by lithium aluminium hydride and sodium borohydride. It gave bis(trimethyl-cyclohexadienyl) iron This method of production was tried on dibenzene-iron cation which is unstable in water. An orange crystalline compound was obtained but could not be fully cheraoterised due to the small yield Both lithium aluminium hydride and sodium borohydride reduced mesitylene-cyclopentadienyliron triiodide yielding (trimethyl-cyclohexadienyl)-cyclopentadienyliron. Benzene-cyclopentadieayliron iodide did not react with sodium methoxide, the sodium salt of diethyl malonate or potassium tertiary but-oxide. However it does react with sodium borohydride and methyl lithium yielding cyclohexadienyl-cyclopentadienyliron and methyl -cyclohexadienyl-cyclopentadisnyliron respectively. Certain electrophilic substitution reactions have also been attempted with cyclohexadienyl-cyclepentadienyl iron. Dicarbonyl-cyclopentadienylcyclohexeneironhexafluorophoaphate has been treated with different nucleophilic agents. Cyclohexyl-dicarbonyl-cyclopentadienyliron is produced when the cation is reduced with sodium borohydride. The compound is again converted into the original cation when reacted with trityl fluoroborate and into iododioarbonyl-cyclopentadienyliron and cyanodicarbonyl-cyclopentadienyl-iron when the cation is treated with potassium iodide and potassium cyanide respectively. The effect of other nucleophilic agents on this cation has also been studied