Electrospray mass spectrometry study on polynuclear Pd (II) and Ni(II) complexes of 3,6,9,16,19,22-hexaazatricyclo[22.2.2.2(11,14)] triaconta-11,13,24,26(1),27,29-hexaene

Polynuclear Pd(II) and Ni(II) complexes of macrocyclic: polyamine 3,6,9,16, 19,22-hexaazatricyclo [22. 2. 2. 2(11,14)]-triaconta 11, 13, 24, 26 (1), 27 , 29-hexaene (L) in solution were investigated by electrospray ionization m ass spectrometry (ESIMS). For methanol solution of complexes M2LX4 (M = Pd( II) and Ni (II), X = Cr and I-), two main clusters of peaks were observed w hich can he assigned to [M2LX3](+) and [M2LX2](2+). When Pd2LCl4 was treate d with 2 or 4 mol of AgNO3, it gave rise formation of Pd2LCl2 (NO3)(2) (.) H2O and [Pd2L(H2O)(m)(NO3)(n)]((4-n)+), respectively. ESMS spectra show tha t the dissociation of the former in the ionization process gave peaks of [P d2LCl2](2+) and [(Pd2LCl2)NO3](+), while dissociation. of the later gave th e peaks of [Pd2L(CH3CO2)(2)](2+) and {[Pd2L(CH3CO2)(2)]. (NO3)}(+) in the p resence of acetic acid. Similar species were observed for Pd2LI4 when treat ed with 4 mol of AgNO3. When [Pd2L . (H2O)(m)(NO3)(n)]((4-n)+) reacted with 2 mol of oxalate anions at 40 degreesC, [Pd4L2(C2O4)(2)(NO3)(2)](2+) and [ Pd4L2(C2O4)(2)n . (NO3)](3+) were detected. This implies the formation of s quare-planar molecular box Pd4L2(C2O4)(2)(NO3)(4) in which C2O42- may act a s bridging ligands: as confirmed by crystal structure analysis. The dissoci ation form and the stability of complex cations in gaseous state are also d iscussed. This work provides an excellent example of the usefulness of ESIM S in the identification of metal complexes in solution.