Fluorophosphine complexes of rhodium(I). Part III. Ligand-exchange studies in some dirnethylaminodifluorophosphinerhodium(I) complexes

Abstract

Di-µ-chloro-tetrakis(ethylene)dirhodium reacts with an excess of dimethylaminodifluorophosphine at room temperature affording the monomeric complex RhCl(PF₂NMe₂)₃. When [RhCl(C₂H₄)₂]₂ and Me₂NPF₂ react in a 1 : 4 molar ratio the product is the dimeric complex [RhCl(PF₂NMe₂)₂]₂. Both complexes exist as discrete entities in solution, and addition of PF₂NMe₂ to [RhCl(PF₂NMe₂)₂]₂ quantitatively affords RhCl(PF₂NMe₂)₃. The dimer is readily regenerated by pyrolysis of RhCl(PF₂NMe₂)₃in vacuo. [RhCl(PF₂NMe₂)₂]₂ reacts with potassium amalgam in the presence of PF₂NMe₂ to yield K[(PF₂NMe₂)₄Rh] and undergoes bridge cleavage with triphenylphosphine without loss of PF₂NMe₂ to afford RhCl(PF₂NMe₂)₂(PPh₃). The latter has been assigned a cis-stereochemistry on the basis of its ¹⁹F n.m.r. spectrum. The easy phosphine exchange processes occurring in these complexes have been established by ¹⁹F and ¹H n.m.r. studies. The monosubstituted complex RhCl(PF₂NMe₂)(PPh₃)₂ is the product from the reaction between a 1 : 1 molar ratio of RhCl(Ph₃P)₃ and PF₂NMe₂. Both RhCl(PF₂NMe₂)₃ and [RhCl(PF₂NMe₂)₂]₂ act as catalysts for the decarbonylation of benzaldehyde.