Liquid injection field desorption/ionization of transition metal fluoride complexes

Metal fluoride complexes that are extremely sensitive to air and water have been characterized by liquid injection field desorption/ionization (LIFDI) mass spectrometry. Dilute solutions of fluoride complexes of nickel, rhodium, titanium, zirconium and ruthenium in toluene and tetrahydrofuran were examined by LIFDI methods on a time-of-flight mass spectrometer. All the spectra of nickel, titanium and zirconium complexes exhibited the molecular ion as base peak. The ruthenium and rhodium complexes showed M−HF]⁺ as base peaks but the molecular ions were easily detected. The nickel complexes do not provide useful mass spectra by EI or ESI methods. Only the titanium and zirconium species showed evidence of the fluoride ligands in the ESI spectra. Two new nickel fluoride complexes are formed by C-F activation reactions with 2,3,5,6-tetrafluoro-4-dimethylaminopyridine and 2,3,5,6-tetrafluoro-4-methoxypyridine yielding trans-NiF{2-C₅NF₃(4-NMe₂)}(PEt₃)₂ and trans-NiF{2-C₅NF₃(4-OMe)}(PEt₃)₂, respectively. The crystal structure of trans-NiF{2-C₅NF₃(4-NMe₂)}(PEt₃)₂ shows typical square planar coordination at nickel with an Ni-F distance of 1.8521(9) Å.