Some complexes are stable enough to be sampled by MALDI (which can ionize solid samples). Depending on the instrumentation available to you, there may be several different matrices (or none needed for some compounds) and laser settings that might help. https://en.wikipedia.org/wiki/Matrix-assisted_laser_desorption/ionization
You could also try using a DART to ionize your sample (either from solid or dmso solution) https://en.wikipedia.org/wiki/DART_ion_source
What are the molecular weight range you are talking and your samples characteristics to be part of matrices, and response o other mass techniques! Are the MALDI-TOF, ES, FAB-MS (may work) techniques and the instrument is available, try NCL, Pune.