Synthesis, reactivity, and crystal amidinate structures of ferrocene-substituted derivatives

Reaction of FcLi (Fc = ferrocenyl) with DCC (DCC = 1,3-dicyclohexylcarbodii mide), followed by the addition of water, yields the ferrocene-containing a midine Fc(NCy)NHCy in 50% yield. The amidine is readily deprotonated by LiN (SiMe3)(2) or NaN(SiMe3)(2) to yield alkali metal amidinates, [FcC(NCy)(2)] Li and [FcC(NCy)(2)]Na, in high yields. These serve as convenient sources o f [FcC(NCy)(2)](-) for a wide range of salt-metathesis reactions with trans ition metal halides. Reactions of [FcC(NCy)(2)]Li with 0.5 equivalents MX2 (M = Fe, Co; X = Cl, Br) form the paramagnetic 4-coordinate derivatives [Fc C(NCy)(2)](2)M. Reaction of [FcC(NCy)(2)]Na with CpFe(CO)(2)I affords the c arbamoyl derivative CpFe(CO)[FcC(NCy)N(Cy)C(O)]. Although not thermally lab ile, a CO ligand is readily lost upon UV irradiation to give the amidinate derivative CpFe(CO)[FcC(NCy)(2)]. The addition of (CO)-C-13 (50 psig) to a solution of CpFe(CO)[FcC(NCy)(2)] results in the rapid exchange of CO at 25 degreesC. Heating this solution to 80 degreesC results in the partial form ation of the carbamoyl species by a formal CO insertion into an Fe-N bond. Reaction of [FcC(NCy)(2)]Li with 0.5 equivalents [Rh(CO)(2)(mu -Cl)](2) for ms orange [FcC(NCy)(2)]Rh(CO)(2) in good yield. Cyclic voltammetry measurem ents in THF reveal a quasi-reversible oxidation at E-1/2 = + 0.46 V followe d by an irreversible oxidation at + 1.49 V (vs. Cp2Fe). Chemical oxidation of [FcC(NCy)(2)]Rh(CO)(2) with AgBF4 generates the amidine-containing produ ct {[FcC(NCy)-NHCy]Rh(CO)(2))[BF4]. (C) 2001 Elsevier Science B.V. All righ ts reserved.