Synthesis, structure and gas-phase reactivity of the mixed silver hydride borohydride nanocluster [Ag3(μ3-H)(μ3-BH4)L(Ph)3]BF4 (L(Ph) = bis(diphenylphosphino)methane).

Borohydrides react with silver salts to give products that span multiple scales ranging from discrete mononuclear compounds through to silver nanoparticles and colloids. The cluster cations Ag3(H)(BH4)L3 are observed upon electrospray ionization mass spectrometry of solutions containing sodium borohydride, silver(I) tetrafluoroborate and bis(dimethylphosphino)methane (L(Me)) or bis(diphenylphosphino)methane (L(Ph)). By adding NaBH4 to an acetonitrile solution of AgBF4 and L(Ph), cooled to ca. -10 °C, we have been able to isolate the first mixed silver hydride borohydride nanocluster, [Ag3(μ3-H)(μ3-BH4)L(Ph)3]BF4, and structurally characterise it via X-ray crystallography. Combined gas-phase experiments (L(Me) and L(Ph)) and DFT calculations (L(Me)) reveal how loss of a ligand from the cationic complexes Ag3(H)(BH4)L3 provides a change in geometry that facilitates subsequent loss of BH3 to produce the dihydride clusters, Ag3(H)2Ln (n = 1 and 2). Together with the results of previous studies (Girod et al., Chem. - Eur. J., 2014, 20, 16626), this provides a direct link between mixed silver hydride/borohydride nanoclusters, silver hydride nanoclusters, and silver nanoclusters.