BETA-DIKETONES CONTAINING A FERROCENYL GROUP - SYNTHESIS, STRUCTURAL ASPECTS, PK(A)(1), VALUES, GROUP ELECTRONEGATIVITIES AND COMPLEXATION WITH RHODIUM(I)

1-Ferrocenyl-4,4,4-trifluorobutane-1,3-dione (ferrocenoyltrifluoroacet one, Hfctfa, pK(a)(1) = 6.53 +/- 0.03), 4,4,4-trichloro-1-ferrocenylbu tane-1,3-dione (trichloroferrocenoylacetone, Hfctca, pK(a)(1) = 7.15 /- 0.02), 1-ferrocenylbutane-1,3-dione (ferrocenoylacetone, Hfca, pK(a )(1) = 10.01 +/- 0.02), 1-ferrocenyl-3-phenylpropane-1,3-dione (benzoy lferrocenoylmethane, Hbfcm, pK(a)(1) = 10.41 +/- 0.02) and 1,3-diferro cenylpropane-1,3-dione (diferrocenoylmethane, Hdfcm, pK(a)(1) = 13.1 /- 0.1) were prepared by Claisen condensation of acetylferrocene with an appropriate ester under the influence of sodium amide, sodium ethox ide or lithium diisopropylamide. The group electronegativity of the fe rrocenyl group is 1.87 (Gordy scale) as inferred from a linear beta-di ketone pK(a)(1)- group electronegativity relationship as well as from a linear methyl ester IR carbonyl stretching frequency-group electrone gativity relationship. Complexes [Rh(beta-diketone)(cod)] were obtaine d in yields approaching 80% by treating the beta-diketones with [Rh2Cl 2(cod)(2)], while the copper(II) chelates form just as readily. Treatm ent of all [Rh(beta-diketone)(cod)] complexes with 1,10-phenanthroline (phen) and some of its derivatives resulted in substitution of the be ta-diketone ligand to form [Rh(cod)(phen)](+). The uncomplexed beta-di ketones are increasingly stabletowards the OH- nucleophile in the orde r Hdfcm (apparent most unstable) < Hfctfa < Hbfcm < Hfctca < Hfca (mos t stable). Asymmetric enolisation in the direction furthest from the f errocenyl group was observed for all beta-diketones. This finding is c onsidered to be the result of resonance driving forces rather than ind uctive electronic effects of substituents on the pseudo-aromatic beta- diketone core.