Ligand-stabilized Nickel and Palladium Boride Colloids

A route to the first ligand stabilized nickel and palladium boride colloids with core diameters of 1.4 and 1.6 nm is described. The particles are formed by reaction of the metal complexes Cl2M(PR3)2 (M = Ni, Pd, PR3 = PPr3, PBu3) with B2H6 in toluene at room temperature with 40–70% yield. The characterization of the pyrophoric brown powders occurred by elementary analyses, resulting in smallest formula units, which then could be extended to averaged molecular formulas by mass determinations, using an analytical ultracentrifuge: [Ni6B10Cl1.5(PPr3)]12.5 (1), [Ni6B10Cl1.5(PBu3)]8.5 (2), [Pd4B6Cl(PPr3)]16.5 (3), and [Pd4B6Cl(PBu3)]16.5 (4). From the masses of the colloid cores and their roughly calculated densities the size of the boride particles could be estimated. The diameters of 1.6 nm for 1, 3, and 4 are identical within the experimental error. Only 2 seems to have a slightly reduced diameter of 1.4 nm. 1–4 can be dispersed in inert organic solvents in any concentration. To confirm these relatively uncertain values high resolution transmission electron microscopy has been used. Investigations of 1 and 3 show indeed an averaged particle size of 1.6 ± 0.3 nm in agreement with the data derived from the mass determinations. Surprisingly most of the observed particles appear to have amorphous structure. This finding is supported by X‐ray powder diffraction experiments, as no significant reflex data could be registered. 31P and 11B NMR measurements have been performed too, however, do not contribute to further characterization. Ligandstabilisierte Nickel‐ und Palladiumborid‐Kolloide Es wird ein Weg zu den ersten ligand‐stabilisierten Nickel‐ und Palladiumborid‐Kolloiden mit Kerndurchmessern von 1,4 und 1,6 nm beschrieben. Die Teilchen bilden sich bei der Reaktion der Metallkomplexe Cl2M(PR3)2 (M = Ni, Pd; PR3 = PPr3, PBu3) mit B2H6 in Toluol bei Raumtemperatur in 40–70% Ausbeute. Die Charakterisierung der pyrophoren braunen Pulver erfolgte durch Elementaranalysen, die zu kleinsten Formeleinheiten führten, welche dann durch Molmassebestimmungen mittels analytischer Ultrazentrifuge zu gemittelten Molekülformeln erweitert werden konnten: [Ni6B10Cl1,5(PPr3)]12,5 (1), [Ni6B10Cl1,5(PBu3)]8,5 (2), [Pd4B6Cl(PPr3)]16,5 (3) und [Pd4B6Cl(PBu3)]16,5 (4). Aus den Massen der Kolloidkerne und ihren ungefähr berechneten Dichten konnte die Größe der Boridpartikel abgeschätzt werden. Die Durchmesser von 1,6 nm für 1, 3, und 4 sind innerhalb der Fehlergrenzen gleich. Nur 2 schei