Synthesis and Coordination of Isomeric Phosphinoferrocene Sulfonates

Two isomeric phosphinoferrocene sulfonic acids representing methylene congeners of 1′‐(diphenylphosphino)ferrocene‐1‐sulfonic acid, viz. Ph 2 PCH 2 fcSO 3 H (HL 1 ) and Ph 2 PfcCH 2 SO 3 H (HL 2 , fc = ferrocene‐1,1′‐diyl) are synthesized and isolated as the stable crystalline ammonium salts (Et 3 NH)L 1 and (Et 2 NH 2 )L 2 . Additional salts with 1,4‐diazabicyclo[2.2.2]octane (dabco), namely, (dabcoH 2 )(L 1 ) 2 and (dabcoH)L 2 , are prepared for structural characterization by single‐crystal X‐ray diffraction analysis. Salts (Et 3 NH)L 1 and (Et 2 NH 2 )L 2 are further studied as ligands in palladium(II) complexes containing the [2‐(dimethylamino‐κ N )methyl]phenyl‐κ C 1 (L NC ) auxiliary ligand. With [(L NC )Pd(μ‐Cl)] 2 , the salts reacted under cleavage of the dimeric precursor to produce anionic phosphine complexes (Et 3 NH)[(L NC )PdCl(L 1 ‐κ P )] and (Et 2 NH 2 )[(L NC )PdCl(L 2 ‐κ P )]. Subsequent chloride removal with AgNO 3 or, alternatively, the direct reaction of (Et 3 NH)L 1 and (Et 2 NH 2 )L 2 with the acetate‐bridged dimer [(L NC )Pd(μ‐OAc)] 2 afforded the corresponding neutral phosphinosulfonate complexes that crystallized as the cyclic O,P‐bridged trimer [(L NC )PdCl(μ(P,O)‐L 1 )] 3 and hexamer [(L NC )PdCl(μ(P,O)‐L 2 )] 6 , respectively. This behavior highlights the hybrid and hemilabile nature of the heteroditopic phosphinosulfonate donors in reactions with the soft Pd(II) ions.