Isopolyoxorhenates observed by positive ion electrospray mass spectrometry

Unknown positive ion isopolyoxorhenates have been observed using electrospray ionization mass spectrometry (ESI+). The ESI+ studies of ammonium and alkali metal (Na+ and K+) perrhenate salts in aqueous solution at pH 4.5 show the existence of the series [Ax+1ReVIIxO4x]+ (where x=1–5 and A=NH4+, Na+ and K+). In the potassium perrhenate system, the series [Kx+2ReVReVIIxO4x+3]+ (x=0–4) has also been characterised. All of these four series have {AReO4} as the aggregation unit. In the ammonium perrhenate system, the monomeric Re(VII)-containing species, [(NH4)2(H2ReO5)]+, [(NH4)3(HReO5)]+ and [(NH4)4(ReO5)]+ were also detected.