Triphenyl-phosphine and -arsine analogues which facilitate the electrospray mass spectrometric analysis of neutral metal complexes

Abstract

The six triarylphosphines PPh_n(C₆H₄OMe-p)_3–n and PPh_n(C₆H₄NMe₂-p)_3–n(n = 0–3) and the arsine As(C₆H₄OMe-p)₃ (L) have been synthesized and examined for their use in the electrospray mass spectrometric (ESMS) study of metal complexes. This has been tested with selected examples of the complexes [Mo(CO)₄L₂], [Fe(CO)₃L₂], [Fe(CO)₄L], [Ru₃(CO)₉L₃], cis-[PtCl₂L₂], [PdCl₂L₂] and [AuCl(L)]. All of the metal carbonyl complexes of these ligands gave [M + H]⁺ ions in their spectra, while in contrast the analogous PPh₃ complexes do not, suggesting that these electrospray-friendly ligands should be useful for the characterisation of a wide range of complexes by ESMS. The incorporation of the ligands into metal halide complexes however does not allow the observation of [M + H]⁺ ions, with ions formed by the previously reported halide-loss mechanism being the only ones observed.