Electrospray Mass Spectrometric Studies of Two Palladium-Allyl Complexes of the Trost Standard Ligand

Two allyl-palladium(II) complexes bearing the Trost standard ligand (1), i.e., [(C(3)H(5))Pd(S,S-1)](+)CF(3)(-)SO(3)(-) and [(c-C(6)H(9))Pd(S,S-1)](+)BArF(-) (BArF(-) = [B((3,5-(CF(3))(2))C(6)H(3))(4)](-)), are investigated using electrospray ionization (ESI) mass spectrometry. Both species form abundant quasi-molecular ions [(C(3)H(5))Pd(S,S-1)](+) and [(c-C(6)H(9))Pd(S,S-1)](+), respectively. At elevated concentrations of the solutions admitted to the ESI source, significant aggregation to binuclear species is observed, which agrees with recent results from solution chemistry. Consistent with solution-phase studies, the tendency of clustering is much less pronounced for the bulky BArF(-) counterion compared to the smaller Inflate.