Eco-Friendly New Ligands for Catalistys Design: Chemistry of Multidentate O-Functionalized Cp Ligands and Rh-Coordination”

New Catalysis Methodologies aimed to reduce toxicity for human health and environment[1] constitute a recognized target for Sustainable Chemistry. Our studies concern new ligands design and development by using non-injurious solvents, moderate conditions and no waste products. Currently our group is involved on the synthesis and characterization of new water soluble polydentate cyclopentadienyl derivatives, tethering from 1 to 3 alcoholic pendants NaCpO,O,O = Na[C5H5-nRn] [n=1,2,3 R = CH(CH2)3CHOH]. Substitution reaction is performed either by one or multistep protocol. Recycle leads to complete conversion. The reaction discriminates by impeded rotation (atropisomerism) either position (1,2,4) or central chirality sequence, shown by the cycloalkyl stereocentres. Reaction products result only two among all the possible isomers. Rhodium coordination of OH-tethered triply functionalized Cyclopentadienyl ligands stereospecifically selects the less congested enantioface, affording a unique planar chiral stereoisomer (pS or M) (LL)Rh{C5H2[CH(CH2)3CHOH]3} (LL = CO, COD, CH2CH2, NBD), whose nature was determined by different spectroscopic means (ESI-Ms, UV, CD, IR). X-ray diffraction studies in the case of [(NBD)RhCpO,O,O] identifies one of the two diasteroisomer as [1(R,S), 2(S,R), 4(S,R)]C5H2[C*H(CH2)3CHOH]3}, confirming the suggested structure in solution performed by n.O.e. and bidimensional NMR experiments. The latter complex shows high solubility (Ko/w=0.86) and high stability in water (over one week). Further coordination abilities of alcoholic pendants towards Titanium affording poly-alkoxy aggregate systems have also been explored. Preliminary investigations on the new class of hydrophilic Rhodium complexes as mediator for transfer hydrogenation of carboxyl olefins will be also reported. [1] (a) Cornils, B.; Herrmann, W.A.; Aqueous-Phase Organ ometallic Catalysis Wiley-VCH ed. 2002. (b) Cornils B; Herrmann.A. Multiphase Homogenous Catalysis Wiley-VCH ed. 2005.