Synthesis, structure, and condensed-phase reactivity of [Ag3(μ3-H)(μ3-BH4)LPh3](BF4) (LPh = bis(diphenylphosphino)amine) with CS2

Electrospray ionisation mass spectrometry (ESI-MS) was used to monitor the reaction of AgBF<small>₄</small>, bis(diphenylphosphino)amine (dppa = (Ph<small>₂</small>P)<small>₂</small>NH = L<small>^Ph</small>) and NaBH<small>₄</small> in acetonitrile and thereby direct the synthesis of the silver nanocluster [Ag<small>₃</small>(μ<small>₃</small>-H)(μ<small>₃</small>-BH<small>₄</small>)L<small>^Ph</small><small>₃</small>](BF<small>₄</small>), <strong>3b·BF<small>₄</small></strong>, formed <em>via</em> reaction of AgBF<small>₄</small>, bis(diphenylphosphino)amine (dppa = (Ph<small>₂</small>P)<small>₂</small>NH = L<small>^Ph</small>) and NaBH<small>₄</small> in acetonitrile. The X-ray structure of <strong>3b·BF<small>₄</small></strong> highlights that the cation adopts a planar trinuclear Ag<small>₃</small> geometry surrounded by three dppa ligands and coordinated on the bottom face by a μ<small>₃</small>-hydride and on the top face by a μ<small>₃</small>-BH<small>₄</small>. The solution phase structure of <strong>3b·BF<small>₄</small></strong> was characterised by multinuclear NMR and DOSY NMR, which showed that the borohydride anion remains bound in the [Ag<small>₃</small>(μ<small>₃</small>-H)(μ<small>₃</small>-BH<small>₄</small>)L<small>^Ph</small><small>₃</small>]<small>⁺</small> cluster cation in solution. ESI-MS and <em>in situ</em><small>¹</small>H and HSQC NMR spectroscopy reveals that <strong>3b·BF<small>₄</small></strong> reacts with CS<small>₂</small> in solution at the BH<small>₄</small> site to yield [Ag<small>₃</small>(H)(S<small>₂</small>CH)L<small>^Ph</small><small>₃</small>]<small>⁺</small>, <strong>4b</strong>, which has to date eluded structural characterisation <em>via</em> X-ray crystallography due to lack of formation of suitable crystals. The gas-phase ion chemistry of [Ag<small>₃</small>(H)(S<small>₂</small>CH)L<small>^Ph</small><small>₃</small>]<small>⁺</small> was examined under multistage mass spectrometry conditions using collision-induced dissociation (CID) and compared to that of the previously examined copper analogue, [Cu<small>₃</small>(H)(S<small>₂</small>CH)L<small>^Ph</small><small>₃</small>]<small>⁺</small>. While both cluster cations fragment <em>via</em> ligand loss, the CID spectra of the resultant [M<small>₃</small>(H)(S<small>₂</small>CH)L<small>^Ph</small><small>₂</small>]<small>⁺</small> are different. Unlike [Cu<small>₃</small>(H)(S<small>₂</small>CH)L<small>^Ph</small><small>₂</small>]<small>⁺</small>, which solely undergoes loss of thioformaldehyde to give [Cu<small>₃</small>(S)L<small>^Ph</small><small>₂</small>]<small>⁺</small>, [Ag<small>₃</small>(H)(S<small>₂</small>CH)L<small>^Ph</small><small>₂</small>]<small>⁺</small> gives a richer CID spectrum with fragmentation channels that include ligand loss, CH<small>₂</small>S loss and reductive elimination of dithioformic acid. DFT calculations exploring rearrangement and fragmentation of the model systems [M<small>₃</small>(H)(S<small>₂</small>CH)L<small>^Me</small><small>₂</small>]<small>⁺</small> ((Me<small>₂</small>P)<small>₂</small>NH = dmpa = L<small>^Me</small>) were used to suggest plausible mechanisms and examine the energetics of the three competing channels: ligand loss, CH<small>₂</small>S loss and reductive elimination of dithioformic acid.