On rhodium complexes bearing H-spirophosphorane derived ligands: Synthesis, structural and catalytic properties

We investigated the coordination properties of H-spirophosphoranes towards rhodium ion. Symmetrical phosphorus ligands: HP(OCH2CH2NH)2 L1, HP(OCH2CMe2NH)2 L2, HP(OCMe2CMe2O)2 L3, HP(OC6H4NH)2 L4, and unsymmetrical phosphorus ligands: HP(OCMe2CMe2O)(OCH2CMe2NH) L5, HP(OCMe2CMe2O)(OC6H4NH) L6 were found to coordinate to rhodium precursor [Rh(CO)2Cl]2 exclusively in protonated κ2-P,E (E = N, O) bidentate fashion, yielding complexes [Rh(CO)ClL] 1–6. The complexes were characterised by spectroscopic methods. The molecular structures of the ligand L6 complexes 3, 5 and 6 were determined by single-crystal X-ray diffraction. The catalytic activity of the complexes was determined in hydroformylation reaction of 1-hexene. Complexes 1 and 2 appeared to be active in isomerisation reactions yielding 76 and 62% of 2-hexene. When used with six-fold excess of triphenylphosphite P(OPh)3 as a modified ligand, the most active catalyst 1 in hydroformylation reaction produced 66% of aldehydes and 22% of 2-hexene.