Platinum Complexes of Rigid Bidentate Phosphine Ligands in the Hydroformylation of 1-Octene

The synthesis of the two novel diphosphine compounds 1,2-bis(3-(diphenylphosphino)-4-methoxyphenyl)benzene (1; Terphos), and 1,2-bis(2-diphenylphosphino)benzene (2), both
derived from a terphenyl backbone structure, are described. Straightforward synthetic routes
have been employed to obtain these ligands in good yields from cheap starting materials.
The coordination of ligands 1 and 2 with PtCl2(cod) has been studied by NMR spectroscopy,
and the X-ray crystal structures of the resulting complexes 4 and 5 were determined. The
31P NMR spectra of the mononuclear products demonstrate solely cis coordination for both
bidentate ligands, with corresponding coupling constants JPt-P of 3810 Hz (cis-[PtCl2(1)],
complex 4) and 3712 Hz (cis-[PtCl2(2)], 5). The bite angles P1−Pt−P2 were 98.74 and 105.89°,
respectively, in the distorted square-planar complexes. The new diphosphines have been
applied in the platinum/tin-catalyzed hydroformylation of 1-octene, and both ligands give
active and selective platinum catalysts.