[MP_y]⁺ and [M_xP_y]^- Clusters Generated by Laser Ablation and Investigated by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

Laser (1064 nm) ablation of pressed mixtures of red phosphorus with powders of the metals cobalt or nickel generates positive ions [MP_y]⁺ (y = 2,4,6,8) and negative ions [M_xP_y]^-, monitored by Fourier transform ion cyclotron resonance (FTICR) mass spectrometry. At least 110 negative ions have been identified, more for Co than for Ni. The ions [M_xP_y]^- are distributed through the range 2 ≤ x ≤ 16, 4 ≤ y ≤ 17, with [Co_xP₈]^- (x = 2, 3, 4, 5), [Co_xP₁₀]^- (x = 5, 6, 7), [Ni_xP₆]^- (x = 4, 5, 7, 8), and [Ni_xP₈]^- (x = 2, 3, 4, 6, 7) as more abundant ions. The best negative ion spectra are obtained with 10:1 M/P mixtures, and high laser powers. The preponderance of even numbers of P atoms suggests that P₂ units are bound to the metals, and this is supported by the collisional dissociation of [MP_y]⁺ ions (M = Co and Ni, y = 2, 4, 6) where loss of P₂ is the major pathway. For both [CoP₈]⁺ and [NiP₈]⁺ initial loss of P₄ is important. The reactions of [MP₂]⁺, [MP₄]⁺ and [MP₈]⁺ with σ-ligands ammonia and methanol, and π-ligands C₂H₂, C₂H₄ and C₆H₆, involve addition and substitution processes.