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 Na[rac-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.