SYNTHESIS, CHARACTERIZATION AND STRUCTURE OF RHODIUM(I) CARBONYL-COMPLEXES WITH O,P-CHELATING 1'-(DIPHENYLPHOSPHINO)FERROCENECARBOXYLATE ORP-MONODENTATE 1'-(DIPHENYLPHOSPHINO)FERROCENECARBOXYLIC ACID

The reaction of 1'-(diphenylphosphino)ferrocenecarboxylic acid (Hdpf) with [{Rh(mu-X)(CO)(2)}(2)] (X = Cl or Br) afforded rhodium(I) complex es trans-[Rh(Hdpf-P)(2)X(CO)] containing the ligand as the P-bonded ph osphine. On the other hand, pentane-2,4-dionato rhodium(I) complexes r eacted with Hdpf by an acid-base reaction yielding novel O,P-chelated rhodium(I) complexes and pentane-2,4-dione (Hacac). The compound [Rh(a cac)(CO)(2)] reacted with 2 equivalents of Hdpf to give trans-[Rh(dpf- O,P)(Hdpf-P)(CO)] which exhibits proton exchange between the two forms of the ligand. Likewise, related complexes [Rh(acac)(PR3)(CO)], where PR3 = PCy3, PPh3 or PPh(2)Fc (Cy = cyclohexyl, Fc = ferrocenyl), affo rded the corresponding complexes trans-[Rh(dpf-O,P)(PR3)(CO)]. The for mation of the O,P chelates is regioselective and might be considered a s a rather unusual displacement of pentane-2,4-dionate by the phosphin ocarboxylate dpf(-) with concurrent proton exchange. All the compounds were characterized by H-1,C-13, (31)p and IR spectroscopies and by FA B mass spectrometry. The crystal structure determination of trans-[Rh( dpf-O,P)(PCy3)(CO)] confirmed the presence of an unprecedented heteroa nnular O,P-chelating ferrocene ligand.