CHARACTERIZATION OF THE INTERMEDIATES IN THE HYDROFORMYLATION REACTION CATALYZED BY PLATINUM DIPHENYLPHOSPHINOUS ACID COMPLEXES

This report describes the reactivity of compounds of the type (Ph2POHOPPh2)PtHL (1), in particular the reactions related to hydroformylation. Ligands L carrying alkenyl and alkynyl groups (Ph2PCH2CH=CH2, Ph2PCH=CH2, P(CH2CH=CH2)3, Ph2POC2H4CH=CH2, Ph2POC2H4C=CH) undergo intramolecular insertion into the adjacent platinum-hydride bond. Diphenylvinylphosphine initially gives a phosphaplatinacyclopropane, which rearranges to (Ph2POHOPPh2)PtPh2PCH2CH2 (10), a phospha-platinacyclobutane complex for which the crystal structure has been determined (C38H35O2p3Pt, space group P21/c, Z = 4, a = 10.622 Å, b = 13.217 Å, c = 24.563 Å, β = 96.66 (2)°). Alkene insertion can take place via a five-coordinate species, whereas the insertion of carbon monoxide seems to require a four-coordinate species with carbon monoxide as one of the ligands in the square plane. Prolonged hydroformylation with 1 gives rise to the formation of inactive complexes, which are shown to be dimeric platinum complexes containing a phosphido and a hydrido bridge. The crystal structure of one of these dimers has been determined, [(Ph2POHOPPh2)Pt]2(μ-PPh2) μ-H) (17a; C60H53O4P5Pt2-C7H8, space group P21/n, Z = 4, a = 15.745 Å, b = 15.151 Å, c = 25.677 Å, β = 99.43 (2)°). Surprisingly, the phosphido anion stems from diphenylphosphinous acid via reduction with acylplatinum complexes and not from triphenylphosphine. © 1990, American Chemical Society. All rights reserved.