A NEGATIVE-ION ELECTROSPRAY MASS-SPECTROMETRIC STUDY OF COMPLEXES IN SOLUTION FORMED BETWEEN UNINEGATIVE TRIPODAL OXYGEN OR NITROGEN LIGANDS AND ALKALI-METAL IONS AND ALKALI-METAL HALIDES

Negative ion electrospray mass spectra have been observed from 50:50 i-propanol/water solution for the sodium salts of uninegative tripodal oxygen ligands of the type [(C5H5)Co(P(O)(OR)(2))(3)](-) (=[L](-)) (R=Me, Et, i-Pr) and solutions of the potassium salt of the uninegative tripodal hydridotris(pyrazole)borate ligand [HB(pz)(3)](-). The sodium salts of the oxygen ligands all give negative ion ES mass spectra which show not only a peak due to the free anion, but also other peaks which may be assigned to [NaL(2)](-), [Na(2)L(3)](-), and in the case of R=Me even [Na(3)L(4)](-). These results are consistent with the known trimeric and polymeric structures of the sodium salts of several of these type of organometallic ligands confirming that these oligomeric structures are at least partially retained in solution. Addition of alkali and metal halides to the solutions of NaL leads to negative ion ES mass spectra showing ions assigned to alkali metal halide adducts of the types ([L](-)+n(NaCl)) (n=1-9) and ([NaL(2)](-)+n(NaCl)) (n=1-8) etc. Fewer alkali metal halides are adducted to the anions with larger alkali metal ions. Lithium chloride also strongly adducts to [L](-), but it causes dissociation of the associated species containing more than one [L](-) group. In contrast, only [HB(pz)(3)](-) and [K(HB(pz)(3))(2)](-) are observed in the negative ion ES mass spectrum of K[HB(pz)(3)] and alkali metal halides do not form observable adducts with this anion.