Cluster transformation of [Cu3(μ3-H)(μ3-BH4)((PPh2)2NH)3](BF4) to [Cu3(μ3-H)(μ2,μ1-S2CH)((PPh2)2NH)3](BF4) via reaction with CS2. X-ray structural characterisation and reactivity of cationic clusters explored by multistage mass spectrometry and computational studies.

Abstract

The copper nanocluster [Cu3(μ3-H)(μ3-BH4)LPh3](BF4), 1a·BF4 (LPh = (PPh2)2NH = dppa), can potentially react with substrates at either the coordinated hydride or borohydride sites. Reaction of 1a·BF4 with CS2 has given rise to [Cu3(μ3-H)(μ2,μ1-S2CH)LPh3](BF4), (2a·BF4), which was structurally characterised using electrospray ionisation (ESI) with high-resolution mass spectrometry (HRMS), X-ray crystallography, NMR, IR and UV-Vis spectroscopy. The copper(i) atoms adopt a planar trinuclear Cu3 geometry coordinated on the bottom face by a μ3-hydride, on the top face by a μ2,μ1-dithioformate and surrounded by three bridging LPh ligands. Reaction of 1a·BF4 with elemental sulfur gives the known cluster [Cu4(LPh-H + 2S)3](BF4), (3·BF4), which was structurally characterised via X-ray crystallography. ESI-MS of 2a·BF4 produces [Cu3(H)(S2CH)LPh3]+ and its gas-phase ion chemistry was examined under multistage mass spectrometry conditions using collision-induced dissociation (CID). The primary product, [Cu3(H)(S2CH)LPh2]+, formed via ligand loss, undergoes further fragmentation via loss of thioformaldehyde to give [Cu3(S)LPh2]+. DFT calculations exploring rearrangement and fragmentation of the model system [Cu3(H)(S2CH)LMe2]+ (LMe = (PMe2)2NH = dmpa) provide a feasible mechanism. Thus, coupling of the coordinated hydride with the dithioformate ligands gives [Cu3(S2CH2)LMe2]+, which then undergoes CH2S extrusion via C-S bond cleavage to give [Cu3(S)LMe2]+.