Scheme 28. (A) Structure of monosulfonated triphenylphosphine (52). (B) ESI(–)-MS of Pd(PPh₃)₄ + [PPN][52 ^–] + 100 × (PhI + PhC₂H + NEt₃) in CH₂Cl₂. Inset: isotope pattern match for [Pd(52 ^–)(PPh₃)(Ph)(C₂Ph)]. (C) Intermediates that were directly observed by ESI(–)-MS and the proposed catalytic cycle. Reproduced from ref. 104 with permission from the Royal Society of Chemistry.