A fast atom bombardment mass spectrometry study of transition metal carbonyl cluster compounds

Abstract

The use of fast atom bombardment (FAB) mass spectrometry for the characterization of several transition metal cluster compounds is described and compared with that of electron impact (EI) mass spectrometry. The FAB mass spectra of the series [H 2Os 7(CO) 22− n ] ( n = 0, 1 and 2) afforded high abundance quasi-molecular ions [ MH] +, only when obtained in a CO-saturated 3-nitrobenzyl alcohol (NBA) matrix; loss of CO ligands ( n = 0, 1) to yield [H 2Os 7(CO) 20] occurred in the argon saturated matrix and under the EI mass spectrometry conditions. No molecular signals were detected in the EI mass spectra of the series [HIr 4(CO) 10(μ-PPh 2)], [HIr 4(CO) 9(PPh 3)(μ-PPh 2)] and [(PhMe 2)AuIr 4(CO) 10(μ-PPh 2)], but their FAB mass spectra in NBA matrix displayed [ MH] + ions and fragment ions that are easily correlated to the structures of these species. The FAB mass spectra of compounds [MIr 4(CO) 9L(η 5-C 5Me 5)(μ 4-PPh)] (M = Rh, Ir; L = CO, PPh 2Me) in NBA matrix exhibited [ MH] + ions and fragment ions corresponding to loss of CO and of HPh from the PPh ligand. Comparative studies of the reactions of [HIr 4(CO) 10(μ-PPh 2)] and [(Bu 4N)(Ir 4(CO) 11Br)] with PPh 3 to give [HIr 4(CO) 9(PPh 3)(μ-PPh 2)] and [Ir 4(CO) 11(PPh 3), respectively, on the FAB probe tip and in solution have established a correlation between species observed by FAB mass spectrometry and those present in the reaction mixture.