Coordination chemistry of ester-functionalized cp ligands: synthesis and catalytic activity of [Rh{CpCO2(CHPh)2OH}(NBD)] and [Rh{CpCO2(CH2)3OH}(NBD)]

Two new sodium hydroxyalkoxycarbonylcyclopentadienide salts Narac-CpCO₂(CHPh)₂OH] (1) and Na(2S,3S)-CpCO₂(CHPh)₂OH] (2) were prepared by reaction of NaCp with the five-membered cyclic carbonates cis-4,5-diphenyl-1,3-dioxolan-2-one and (4S,5S)-4,5-diphenyl-1,3-dioxolan-2-one. The reaction of these salts with Rh(NBD)Cl]₂ gave Rh{rac-CpCO₂(CHPh)₂OH}(NBD)] (3) and (−)-Rh{(2S,3S)-CpCO₂(CHPh)₂OH}(NBD)] (4) whose catalytic activity in the hydroformylation of hex-1-ene and styrene has been investigated and compared with that of the previously reported rhodium complexes Rh{CpCO₂(CHR)₂OH}(NBD)] (R=H, Me). In addition we also discuss some preliminary results regarding the behavior of these complexes in the hydrogenation of the same substrates. The reactivity of NaCp toward the six-membered cyclic carbonate 1,3-dioxan-2-one has also been studied and it has been found that the reaction leads to two cyclopentadienide anions CpCO₂(CH₂)₃OH]⁻ (5) and CpCO₂(CH₂)₃OC(O)O(CH₂)₃OH]⁻ (6) in amounts strictly dependent on the carbonate/NaCp stoichiometric ratio.