Formation and gas phase fragmentation reactions of ligand substitution products of platinum(II) complexes via electrospray ionization tandem mass spectrometry †

Abstract

Solution phase ligand substitution reactions of [Pt(dien)Cl]+ and [Pt(Me5dien)Cl]+ (Me5dien = N,N,N′,N′′,N′′-pentamethyldiethylenetriamine) have been monitored using electrospray ionization mass spectrometry. The [Pt(Me5dien)Cl]+ ion undergoes much slower ligand substitution than [Pt(dien)Cl]+, which is consistent with the crystal structure of [Pt(Me5dien)Cl]+ determined, which suggests steric crowding (relative to the [Pt(dien)Cl]+ structure) induced by the buttressing methyl groups. In addition, the gas phase collision induced dissociation reactions of [Pt(dien)X]n+ ions (n = 1, X = bromide, iodide, thiocyanate, cyanate, azide or nitrite; n = 2, X = pyridine) formed via solution phase ligand substitution have been examined. In most cases the ligand is lost as HX, giving rise to the co-ordinatively unsaturated [Pt(dien) − H]+ ion. Noteable exceptions include n = 1, where X = N3− or NO2−, which instead exhibit ligand fragmentation via loss of N2 and NO respectively to yield the novel platinum species [Pt(dien)N]+ and [Pt(dien)O]+. The structures of these ions have been examined using density functional calculations at the B3LYP/LAV1S level of theory.