Structural Diversity in Molecular Nickel Phosphide Carbonyl Nanoclusters

The reaction of [Ni-6(CO)(12)](2-) as a [NBu4](+) salt in CH2Cl2 with 0.8 equiv of PCl3 afforded [Ni14P2(CO)(22)](2-). In contrast, the reactions of [Ni-6(CO)(12)](2-) as a [NEt4](+) salt with 0.4-0.5 equiv of POCl3 afforded [Ni22-xP2(CO)(29-x)](4-) (x = 0.84) or [Ni39P3(CO)(44)](6-) by using CH3CN and thf as a solvent, respectively. Moreover, by using 0.7-0.9 mol of POCl3 per mole of [NEt4](2)[Ni-6(CO)(12)] both in CH3CN and thf, [Ni23-xP2(CO)(30-x)](4-) (x = 0.82) was obtained together with [Ni22P6(CO)(30)](2-) as a side product. [Ni23-xP2(CO)(30-x)](4-) (x = 0.82) and [Ni22P6(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 [NBu4](2)[Ni14P2(CO)(22)] (two different polymorphs, P2(1)/n and C2/c), [NEt4](4)[Ni23-xP2(CO)(30-x)]center dot CH3COCH3 center dot solv (x = 0.82), [NEt4](2)[Ni22P6(CO)(30)]center dot 2thf, [NEt4](4)[Ni22-xP2(CO)(29-x)]center dot 2CH(3)COCH(3)(x = 0.84) and [NEt4](6)[Ni39P3(CO)(44)]center dot C6H14 center dot 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, Ni5P pentagonal pyramid, Ni7P monocapped trigonal prism, Ni8P bicapped trigonal prism, Ni9P monocapped square antiprism, Ni10P sphenocorona, Ni10P bicapped square antiprism, and Ni12P icosahedron.