Electrospray mass spectrometry of metal carbonyl complexes

Methods are described for characterising neutral metal carbonyl complexes using electrospray mass spectrometry, by converting them into ions with suitable reagents. Ionisation techniques included addition of OMe- generating [M + OMe](-) species, addition of Ag+ or Na+ ions giving the appropriate positive ion, abstraction of acidic hydrogen forming [M-H](-) ions, or (in rare cases) oxidation giving radical cations [M](.+). The methods can be used on pure compounds or on mixtures. Fragmentation in the mass spectrometer can be minimised so that identification of parent species is unambiguous. Applications are demonstrated with a wide range of compounds including mononuclear and polynuclear binary carbonyls, and with derivatives containing phosphine; cyclopentadienyl, pi-arene, sigma-aryl and other ligands.