LASER-ABLATION FTICR MASS-SPECTROMETRY OF METAL SULFIDES - GASEOUS ANIONIC [NIXSY] CLUSTERS

Laser (Nd/YAG, 1064 nm) ablation of Ni3S2 or NiS, monitored by Fourier transform ion cyclotron resonance mass spectrometry, yields at least 28 [Ni(x)S(y)]- ions, ranging from [NiS]- to [Ni15S10]-. The x,y combinations are 1,1; 1,2; 1,3; 2,2; 2,3; 3,2; 3,3; 4,4; 4,5; 5,4; 6,4; 6,5; 7,5; 7,6; 8,5; 8,6; 8,7; 9,6; 9,7; 10,7; 10,8; 11,7; 11,8; 12,7; 12,8; 12,11; 13,8; 15,10. [Ni2S2]- and [Ni5S4]- are unaffected by collisions with argon at 2 x 10(-7) mbar, while the ions [NiS2]-, [Ni3S3]-, and [Ni4S4]- decompose in ca 0.05 s under the same conditions. Evidence for isomeric ions with differing reactivities could be obtained for [Ni3S3]-, but sensitivity limitations precluded reactivity measurements for larger ions. Geometrical structures are postulated for all ions, based on established structural principles, and correspond in many cases to the structures of condensed phase clusters, devoid of terminal ligands.