Characterization of large cationic transition-metal-gold clusters by fast atom bombardment mass spectroscopy (FABMS). New rhenium-gold and platinum-gold clusters: [Au4Re(H)4[P(p-tol)3]2(PPh3)4]+, [Au2Re2(H)6(PPh3)6]+, and [Au6Pt(PPh3)7]2+

Abstract

Fast atom bombardment mass spectroscopy has been used to examine a large number of cationic phosphine-containing transition-metal-fold clusters including polyhydrides, which ranged in mass from 1000 to 4000. Many of these clusters have been previously characterized and were examined in order to test the usefulness of the FABMS technique. Results showed that FABMS is excellent in giving the correct molecular formula including the number of hydride ligands, and when combined with NMR, conductance and analytical data gave complete and reliable characterization. Four new complexes have been synthesized and completely characterized by the above techniques. These are (Au/sub 2/Pt(PPh/sub 3/)/sub 4/NO/sub 3/)NO/sub 3/, (Au/sub 6/Pt(PPh/sub 3/)/sub 7/)(BPh/sub 4/)/sub 2/, (Au/sub 2/Re/sub 2/(H)/sub 6/(PPh/sub 3/)/sub 6/)PF/sub 6/, and (Au/sub 4/Re(H)/sub 4/(P(p-tol)/sub 3/)/sub 2/(PPh/sub 3/)/sub 4/)PF/sub 6/. The FABMS of these and other similar cationic and dicationic clusters with use of m-nitrobenzyl alcohol (MNBA) as the matrix always gave well-resolved peaks for either the parent molecular ion (M)/sub 7/ or the ion pair (M + X)/sup +/ where X = the counterion. Comparison of observed and calculated isotopic ion distributions for these peaks reliably gave the correct molecular formulas. Cluster fragments were also observed that in general resulted from loss of one ormore » more of the following species: PPh/sub 3/, H, CO, Ph, AuPPh/sub 3/. Small peaks that resulted from the addition of matrix fragments to unsaturated cluster ions were also observed.« less