THE REACTION OF R,S AND R,R/S,S-[FE-2(ETA,ETA-C5H4CH(NME(2))CH(NME(2))C5H4)(CO)(2)(MU-CO)(2)] AND [FE-2(ETA,ETA-C5H4CH2CH(NME(2))C5H4)(CO)(2)(MU-CO)(2)] WITH ALKYLATING-AGENTS - PREPARATION, STRUCTURE AND SPECTRA OF [FE-2(ETA,ETA-C5H4CH(NME(2))CH(NME(3))C5H4)(CO)(2)(MU-CO)(2)](+) AND [FE-2(ETA,ETA-C5H4CH2CH(NME(3))C5H4)(CO)(2)(MU-CO)(2)](+) SALTS

The reagents MeI and MeOSO(2)CF(3) methylate R,S-[Fe-2{eta,eta-C5H4CH(NMe(2))CH(NMe(2))C5H4}(CO)(2)(mu-CO)(2)], 1, its R,R/S,S isomer 2, and [Fe-2{eta,eta-C5H4CH2CH(NMe(2))C5H4}(CO)(2)(mu-CO)(2)], 3, at one N atom only. Subsequent anion exchange gives salts of the R,S and R,R/S,S-[Fe-2{eta,eta-C5H4CH(NMe(2))CH(NMe(3))C5H4}(CO)(2)(mu-CO)(2)](+) and [Fe-2{eta,eta- C5H4CH2CH(NMe(3))C5H4}(CO)(2)(mu-CO)(2)](+) cations, [4]X, [5]X and [6]X, respectively (X(-) = Cl-, Br-, I-, [SO3CF3](-), [PF6](-) or [BPh(4)](-)). The H-1-NMR spectra of the cations show that rotation about the C-NMe(3) bond and rotation-inversion of NMe(2) groups can be slowed in [4](+) and [5](+) but not in [6](+), but there is no evidence for partial rotation about the ring-linking C-C bond in any cation, as there is in free 1. The chemical shifts of the Me(3)NC-H and, to a lesser extent, the cyclopentadienyl hydrogen atoms only of all three cations are strongly dependent on the nature of the anion X(-) and the solvent. This is attributed to strong interactions between the Me(3)NC-H hydrogen atom and the solvent or anion, which decrease along the series X(-) = Cl- > Br- > I- > [SO3CF3](-) > [PF6](-) > [BPh(4)](-). There is indirect evidence for Me(2)N- > CH(NMe(3))(+) interactions in [4](+) and [5](+). Attempts to prepare the X(-) = F- salts failed. Reactions of [4][SO3CF3] with [n-Bu(4)N]F in tetrahydrofuran/acetonitrile gave [4][H4F5] whilst [5][SO(3)CF3] and [Et(4)N]F.2H(2)O in dichloromethane gave [5][H5F6]. In acetonitrile [Et(4)N]F.2H(2)O acts a source of [OH](-) ions. It brings about Me(3)N and H+ elimination from [4][SO3CF3] to give an enamine [Fe-2{eta,eta-C5H4CHC(NMe(2))C5H4}(CO)(2)(mu-CO)(2)], a water-gas shift mediated Me(3)N displacement by H- from [5][SO3CF3] to give 3, and converts [6][SO3CF3] to [6][OH]. X-ray diffraction has been used to determine the crystal and molecular structures of R,S-[Fe-2{eta,eta-C5H4CH(NMe(2))CH(NMe(3))C5H4}(CO)(2)(mu-CO)(2)]I.2MeCN and R,S-[Fe-2{eta,eta-C5H4CH(NMe(2))CH(NMe(3)) C5H4}(CO)(2)(mu-CO)(2)][SO3CF3].CH2Cl2. Despite the very different H-1-NMR spectra of these salts in solution, both cations have structures based on that of 1 with methylation of the NMe(2) group that is transoid to a cyclopentadienyl ring rather than that which is transoid to a hydrogen atom. Bond lengths and bond angles are similar to those found in 1, 2 and related species.