The reactions of acids and alkyl iodides with [Fe2(η-C5H5)2(CNMe)4] and related complexes
Abstract
The very high nucleophilicity and basicity of the N atoms of the µ-CNR ligands in [Fe2(η-C5H5)2(CO)(CNMe)3] and [Fe2(η-C5H5)2(CNR)4][R = Me (black isomer) or Et] is illustrated by their ability to react with R′I (R′= Me, Et, or Prn) to give in turn [Fe2(η-C5H5)2L(CNR)(µ-CNR){µ-CN(R)R′}]I and [Fe2(η-C5H5)2L(CNR){µ-CN(R)R′}2]I2(L = CO or CNR). The strong acid HPF6·Et2O gives [Fe2(η-C5H5)2(CNR)2{µ-CN(R)H}2][PF6]2 which with [Fe2(η-C5H5)2(CNR)4] forms [Fe2(η-C5H5)2(CNR)2(µ-CNR){µ-CN(R)H}][PF6]. These all contain N–R′ or N–H bonds. Weak acids such as PhCO2H or MeCO2H (= HA) form only [Fe2(η-C5H5)2(CNR)2(µ-CNR){µ-CN(R)H}][A] complexes, but somewhat stronger acids (HA = CH3–nClnCO2H where n= 1–3) form both these and [Fe2(η-C5H5)2(CNR)2{µ-CN(R)H}2][A]2 derivatives. For these salts there is strong spectroscopic evidence for hydrogen bonding of the type NH ⋯ A–. Although the residual basicity of the µ-CNMe ligand in [Fe2(η-C5H5)2(CNMe)2(µ-CNMe)(µ-CNMe2)]I is illustrated by its reaction with HPF6 to give [Fe2(η-C5H5)2(CNMe)2{µ-CN(Me)H}(µ-CNMe2)]I[PF6]·H2O, the reaction of [Fe2(η-C5H5)2(CNMe)2(µ-CNMe){µ-CN(Me)H}][PF6] with Mel results in dimer cleavage to a salt of the [Fe(η-C5H5)(CNMe)3]+ cation. The brown form of [Fe2(η-C5H5)2(CNMe)4], which is a mixture of the black isomer and another, reacts with MeI to give a mixture of [Fe2(η-C5H5)2(CNMe)2(µ-CNMe)(µ-CNMe2)]I and [Fe(η-C5H5)(CNMe)2I], whilst with CCl3CO2H it gives a mixture of [Fe2(η-C5H5)2(CNMe)2(µ-CNMe){µ-CN(Me)H}][CCl3CO2] and an unidentified [Fe(η-C5H5)(CNMe)2X] species. The i.r. and 1H n.m.r. spectra of the various products are reported and discussed.
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