Rhodium complexes with phosphine and diazabutadiene ligands. Their properties as hydrogenation catalysts. Molecular structure of RhCl(COD)P(p-C6H4F)3

The complexes RhCI(COD)L (I), [Rh(COD)(R- DAB-R′)L]ClO4 (II), and [RhH2(R-DAB-R′)L2]- CIO4 (III), (COD = 1,5-cyclooctadieno, R-DAB-R′= NH2NC(CH3)C(CH3)NNH2, L = P(pC6H4F)3),have been obtained and characterized by IR and 1H NMR. The molecular structure of I was elucidated by X-ray study. Crystals are monoclinic, space group P21/c. Unit cell parameters are: a= 11.145(2), b = 11.991(4), c= 18.356(5) ) Å, β = 99.35(1)°, Z = 4, R = 0.072, R w = 0.081, for 5081 reflections with I≥ 2σ(I). The catalytic activity of complexes I, II and III in the n-hexene hydrogenation processes has been studied, at different temperatures at a constant pressure of H2, in acetone. Compound I presents an induction period that decreases with the increase of temperature. At room temperature (23 °C) the activity follows the order I ≤ II≤III. When T increases this order changes to II ≤ III≤ I. A selectivity towards cis-2-hexene formation has been observed.