Structural Diversity in Molecular Nickel Phosphide Carbonyl Nanoclusters.

The reaction of [Ni ₆ (CO) ₁₂ ] ^2- as a [NBu ₄ ] ⁺ salt in CH ₂ Cl ₂ with 0.8 equiv of PCl ₃ afforded [Ni ₁₄ P ₂ (CO) ₂₂ ] ^2- . In contrast, the reactions of [Ni ₆ (CO) ₁₂ ] ^2- as a [NEt ₄ ] ⁺ salt with 0.4-0.5 equiv of POCl ₃ afforded [Ni _{22- x} P ₂ (CO) _{29- x} ] ^4- ( x = 0.84) or [Ni ₃₉ P ₃ (CO) ₄₄ ] ^6- by using CH ₃ CN and thf as a solvent, respectively. Moreover, by using 0.7-0.9 mol of POCl ₃ per mole of [NEt ₄ ] ₂ [Ni ₆ (CO) ₁₂ ] both in CH ₃ CN and thf, [Ni _{23- x} P ₂ (CO) _{30- x} ] ^4- ( x = 0.82) was obtained together with [Ni ₂₂ P ₆ (CO) ₃₀ ] ^2- as a side product. [Ni _{23- x} P ₂ (CO) _{30- x} ] ^4- ( x = 0.82) and [Ni ₂₂ P ₆ (CO) ₃₀ ] ^2- were separated owing to their different solubility in organic solvents. All the new molecular nickel phosphide carbonyl nanoclusters were structurally characterized through single crystal X-ray diffraction (SC-XRD) as [NBu ₄ ] ₂ [Ni ₁₄ P ₂ (CO) ₂₂ ] (two different polymorphs, P 2 ₁ / n and C 2/ c ), [NEt ₄ ] ₄ [Ni _{23- x} P ₂ (CO) _{30- x} ]·CH ₃ COCH ₃ ·solv ( x = 0.82), [NEt ₄ ] ₂ [Ni ₂₂ P ₆ (CO) ₃₀ ]·2thf, [NEt ₄ ] ₄ [Ni _{22- x} P ₂ (CO) _{29- x} ]·2CH ₃ COCH ₃ ( x = 0.84) and [NEt ₄ ] ₆ [Ni ₃₉ P ₃ (CO) ₄₄ ]·C ₆ H ₁₄ ·solv. The metal cores' sizes of these clusters range from 0.59 to 1.10 nm, and their overall dimensions including the CO ligands are 1.16-1.63 nm. In this respect, they are comparable to ultrasmall metal nanoparticles, molecular nanoclusters, or atomically precise metal nanoparticles. The environment of the P atoms within these molecular Ni-P-CO nanoclusters displays a rich diversity, that is, Ni ₅ P pentagonal pyramid, Ni ₇ P monocapped trigonal prism, Ni ₈ P bicapped trigonal prism, Ni ₉ P monocapped square antiprism, Ni ₁₀ P sphenocorona, Ni ₁₀ P bicapped square antiprism, and Ni ₁₂ P icosahedron.