Electrospray mass spectrometric investigation of the relative ligand properties of EPh3 ligands (E=P, As, Sb or Bi) towards Ag and Cu

Electrospray mass spectrometry (ESMS) has been used to investigate the relative ligand properties of the triphenylpnictogen ligands EPh₃ (E=P, As, Sb and Bi) towards silver(I) and copper(I) ions. It is found that the preferred species formed increase in coordination number from two for PPh₃ in Ag(PPh₃)₂]⁺ to four for SbPh₃ in Ag(SbPh₃)₄]⁺, consistent with the decreasing donor ligand ability and increasing metal –E bond length in the series PPh₃–AsPh₃–SbPh₃. With BiPh_3, the spectra were complex, suggesting considerable decomposition. These studies also suggest that silver(I) and copper(I) ions will have widespread utility in the characterisation of tertiary stibine ligands, as has been described previously for phosphines and arsines. These studies demonstrate the power of the ESMS technique in determining the donor properties of a related series of ligands, and this information is of significance in coordination chemistry.