Synthesis and coordination of a hybrid phosphinoferrocene sulfonamide ligand

Abstract

In order to expand the family of hybrid phosphinoferrocene ligands, a novel phosphinoferrocene sulfonamide ligand, Ph₂PfcNHSO₂Me (1, fc = ferrocene-1,1′-diyl), was synthesised through a reaction between P-protected phosphinoamine Ph₂PfcNH₂·BH₃ and MeSO₂Cl followed by deprotection of the Ph₂PfcNHSO₂Me·BH₃ (2) intermediate. Compound 1 coordinates as a functional phosphine ligand, producing Pd(II) complexes [PdCl(μ-Cl)(1-κP)]₂ (4) or [PdCl₂(1-κP)₂] (5) from [PdCl₂(cod)] (cod = cycloocta-1,5-diene) depending on the stoichiometry. The reaction of 1 with [(L^NC)Pd(μ-Cl)]₂ also produces a phosphine complex, [(L^NC)PdCl(1-κP)] (6; L^NC = 2-[(dimethylamino-N)methyl]phenyl-κC¹), which was converted into the neutral bis-chelate complex [(L^NC)Pd(Ph₂PfcNSO₂Me-κ²P,N)] (7) upon treatment with potassium tert-butoxide; the corresponding cationic chelate [(L^NC)Pd(Ph₂PfcNHSO₂Me-κ²P,O)]⁺ could not be isolated. All compounds were characterised by elemental analysis and spectroscopic methods (NMR, IR and MS). In addition, the crystal structure of 1, 2, and 4–7 were determined (for solvated compounds in some cases), and the electrochemical properties of 1, 2, 6 and 7 were studied by cyclic voltammetry.