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

The six triarylphosphines PPhn(C6H4OMe-p)(3-n) and PPhn(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)(4)L-2], [Fe(CO)(3)L-2], [Fe(CO)(4)L], [Ru-3(CO)(9)L-3], 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.