Regioselective reactions of electrophilic iron dicarbonyl cations, [(η5-C5R5)(CO)2Fe]+ (R = H, CH3) with heterofunctional amine ligands

The reactions of the ether salts [(η5-C5R5)(CO)2Fe(E)]BF4, (R = H, E = Et2O; R = CH3, E = THF) with various ligands possessing two different coordination sites have been investigated. It was established that [(Cp(CO)2Fe(OEt2)]BF4 (Cp = η5-C5H5), 1, and [Cp*(CO)2Fe(THF)]BF4 (Cp* = η5-C5(CH3)5), 2, react with 1-aminopropanol, 4-methoxybenzylamine and 3-aminopropyltriethoxysilane to give only mononuclear complexes of the type [(η5-C5R5)(CO)2Fe(L)]+, irrespective of the reactant ratios. On the other hand, the reaction of 1 with one equivalent of 4-aminobenzonitrile (ABN) furnished both mononuclear and dinuclear complexes, [Cp(CO)2Fe(ABN)]+ and [{Cp(CO)2Fe}2(μ-ABN)]2+ isolated as tetrafluoroborate salts, with the mononuclear complex being the major product. The reaction of [(η5-C5R5)(CO)2Fe(E)]BF4 with 1,4-phenylenedimethanamine (PDA) afforded only the dinuclear complex [{(η5-C5R5)(CO)2Fe}2(μ-PDA)]2+ regardless of the reactant ratios. The reaction of 2 with one equivalent of the compound [Cp(CO)2Fe(ABN)]BF4 gave the mixed ligand salt [Cp(CO)2Fe(ABN)Fe(CO)2Cp*](BF4)2. The reactions of dipropylamine with [Cp(CO)2Fe(OEt2)]BF4 gave the dipropylamine salt [Cp(CO)2Fe{NH(CH2CH2CH3)2}]BF4. All these compounds are reported for the first time and have been fully characterized by 1H NMR, 13C NMR, IR spectroscopy and elemental analysis. Molecular structures of [Cp(CO)2Fe{NH(CH2CH2CH3)2}]BF4, [Cp*(CO)2Fe{NH2(CH2)2CH2OH}]BF4 and [Cp*(CO)2Fe(NH2C6H4OCH3)]BF4 have been confirmed by single crystal X-ray crystallography.

Graphical abstractThe reactions of [(η5-C5H5)(CO)2Fe(Et2O)]BF4 and [(η5-C5(CH3)5)(CO)2Fe(THF)]BF4 with heterofunctional amine ligands (NH2(CH2)2CH2OH, NH2CH2C6H4OCH3, NH2(CH2)3Si(OCH2CH3)3, NH2C6H4CN) and homofunctional 1,4-phenylenedimethanamine have been investigated. The heterofunctional ligands selectively bind to the metal via the amine centre. The molecular structures of [Cp*(CO)2Fe{NH2(CH2)2CH2OH}]BF4, [Cp*(CO)2Fe{NH2CH2C6H4OCH3}]BF4 and [Cp(CO)2Fe{NH(CH2CH2CH3)2}]BF4 have been confirmed by single crystal x-ray crystallography.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Novel monometallic and bimetallic amine complexes of iron have been synthesized. ► The cations [C5R5(CO)2Fe]+ (R = H, CH3) selectively bind to NH2 functionality. ► Structures of [Cp*(CO)2FeL]+ (L = NH2(CH2)3OH, NH2CH2C6HO4CH3) have been determined. ► Structure and synthesis of [(C5H5)(CO)2Fe{NH(CH2CH2CH3)2]+ are also reported.