A novel chiral ferrocene-based amidine/amidinato ligand and its rhodium complexes

The N,N'-bisferrocenyl-substituted chiral formamidine 1 (N,N'-bis[(S)-2-{(1R)-1-(diphenylphosphino)ethyl}ferrocen-1-yl]formamidine) was prepared from commercially available {(1R)-1-(dimethylamino)ethyl}ferrocene by a multistep procedure in an overall yield of 29%. Deprotonation of I followed by addition of [Rh2Cl2(COD)(2)] yielded the (formamidinato)rhodium(l) complex 2 [(N,N'-bis[(S)-2-{(1R)-1-(diphenylphosphino)ethyl}ferrocen-1-yl]formamidinato)rhodium(l)]. Direct reaction of formamidine I with [Rh2Cl2(COD)(2)] led to complex 10 [(k-NP-bis[(S)-2-{(1R)-1-(diphenylphosphino)ethyl}ferrocen-1-yl]formamidine)(chloro)(77 (eta(4)-1,5-cyclooetadiene)rhodium(l)], which was converted to 2 upon addition of base. Oxidative addition of methyl chloride or methyl iodide to 2 yielded the trans adducts 11 [(N,N'-bis[(S)-2-{(1R)-1-(diphenylphosphino)ethyl}ferrocen-1-yl]formamidinato)(chloro)(methyl)rhodium(Ill)] and 12 [(N,N'-bis[(S)-2-{(1R)-1-(diphenylphosphino)ethyl}ferrocen-1-yl]formamidinato)(iodo)(methyl)rhodium(Ill)], the configurations of which were determined by means of NMR and, in the case of the Rh(111) methyl chloride adduct 11, by X-ray analysis.