Synthesis and structural characterization of rac-2-[(diphenylphosphino)methyl]ferrocenecarboxylic acid, its selected derivatives and some rhodium complexes

Abstract

rac-2-[(Diphenylphosphino)methyl]ferrocenecarboxylic acid ( 1) was prepared in a good yield from rac-2-( N, N-dimethylaminomethyl)bromoferrocene ( 2) via rac-2-(hydroxymethyl)bromoferrocene ( 4) and rac-2-[(diphenylphosphino)methyl]bromoferrocene ( 5), and further converted to the respective phosphine oxide ( 6), phosphine sulfide ( 7) and methyl ester ( 8). The phosphines 1 and 8 were studied as ligands in rhodium complexes. The reaction of di-μ-chloro-bis[chloro-(η 5-pentamethylcyclopentadienyl)rhodium(III)] with the stoichiometric amounts of 1 and 8 yielded the corresponding mononuclear complexes with P-monodentate ligands: [RhC 2(η 5-C 5Me 5)(L-κ P)], 9 and 10, respectively. Attempted deprotonation of 9 with LiBu or KO t-Bu gave intractable mixtures, in which the parent complex 9 as the major component was accompanied by two new compounds, likely the diastereoizomeric phosphinocarboxylate complexes. A defined O, P-chelating phosphinocarboxylate complex, [ SP-4-2]-carbonyl-[ rac-2-{(diphenylphosphino)methyl}ferrocenecarboxylato-κ 2 O, P]-tricyclohexylphosphinerhodium(I) ( 12), was obtained from the displacement of acetylacetonate(1−) (acac) ligand in [Rh(acac)(CO)(PCy 3)] (Cy = cyclohexyl) with acid 1. The structures of 1, 6 · CHCl 3, and 7 · 1/2 CH 2Cl 2, 10, and hydrated complexes 9 and 12 were determined by single-crystal X-ray diffraction.