NMR study of intermediates in the bulky diphosphite modified rhodium catalysed hydroformylation

Article abstract of DOI:10.1016/S0022-328X(97)00027-2

The stoichiometric hydroformylation reaction of allyldiphenylphosphine with RhH(CO)₂(2) (2 is a bulky diphosphite) was studied using ¹H and ³¹P NMR spectroscopy. Reaction of equimolar amounts in benzene resulted in the formation of RhH(CO)(CH₂=CHCH₂PPh₂)(2) in which all three phosphorus ligands are coordinated equatorially (4). When 4 was heated, hydride migration occurred leading to two products. Migration to the terminal carbon gave 5, Rh(CO)(PPh₂CH₂CH₂CH₂)(2). Migration of the hydride to the internal carbon atom was rapidly followed by CO insertion, resulting in the acyl compound 6, containing a five-membered rhodacycle. Complex 6 did not undergo reaction with H₂. Reaction of 5 with CO reversibly yielded acyl complex 7, containing a six-membered rhodacycle. Hydrogenation of 5 yielded 8, the diphenylpropylphosphine analogue of 4.