title: Synthesis, Structural Characterization, and Gas-Phase Unimolecular Reactivity of Bis(diphenylphosphino)amino Copper Hydride Nanoclusters [Cu3(X)(μ3-H)((PPh2)2NH)3](BF4), Where X = μ2-Cl and μ3-BH4.
abstract: An electrospray ionization mass spectrometry (ESI-MS) survey of the types of cationic copper clusters formed from an acetonitrile solution containing a 1:1:20 mixture of tetrakis(acetonitrile)copper(I) tetrafluoroborate [Cu(MeCN)4(BF4)], bis(diphenylphosphino)amine (dppa = (Ph2P)2NH = L), and NaBH4revealed a major peak, which based on both the accurate masses and isotope distribution was assigned as [Cu3(BH4)(H)(L)3]+. This prompted synthetic efforts resulting in isolation of the dppa ligated trinuclear copper hydride nanoclusters, [Cu3(μ2-Cl)(μ3-H)(L)3](BF4) and [Cu3(μ3-BH4)(μ3-H)(L)3](BF4), which were subsequently structurally characterized using high resolution ESI-MS, X-ray crystallography, NMR, and IR spectroscopy. The X-ray structures reveal a common structural feature of the cation, in which the three copper(I) ions adopt a planar trinuclear Cu3geometry coordinated on the bottom face by a μ3-hydride and surrounded by three dppa ligands. ESI-MS of [Cu3(μ2-Cl)(μ3-H)(L)3](BF4) and [Cu3(μ3-BH4)(μ3-H)(L)3](BF4) produces [Cu3(μ2-Cl)(μ3-H)(L)3]+and [Cu3(μ3-BH4)(μ3-H)(L)3]+. The unimolecular gas-phase ion chemistry of these cations was examined under multistage tandem mass spectrometry conditions using collision-induced dissociation (CID). CID of both cations proceeds via ligand loss to give [Cu3(μ3-H)(X)(L)2]+, which is in competition with BH3loss in the case of X = BH4. DFT calculations on the fragmentation of [Cu3(μ3-BH4)(μ3-H)(LMe)3]+suggest that BH3loss produces the hitherto elusive [Cu3(μ3-H)(μ2-H)(LMe)3]+, which undergoes further fragmentation via H2loss. CID of the deuterium labeled cluster [Cu3(μ3-D)(μ3-BD4)(L)3]+reveals that the competing losses of ligand and BD3yield [Cu3(μ3-BD4)(μ3-D)(L)2]+and [Cu3(D)2(L)3]+as primary products, which subsequently fragment via further losses of BD3or a ligand to give [Cu3(D)2(L)2]+. The coordinated hydrides in the latter ion are activated toward elimination of D2to give [Cu3(L)2]+. Loss of HD and 2HD are minor channels, consistent with higher DFT predicted endothermicities to form [Cu3(D)(L)(L-H)]+and [Cu3(L-H)2]+.
authors.affiliation: School of Chemistry and Bio21 Molecular Science and Biotechnology Institute, University of Melbourne , 30 Flemington Road, Parkville, Victoria 3010, Australia.
authors.forename: Jiaye
authors.initials: J
authors.lastname: Li
authors.affiliation: School of Chemistry and Bio21 Molecular Science and Biotechnology Institute, University of Melbourne , 30 Flemington Road, Parkville, Victoria 3010, Australia.
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: White
authors.affiliation: CSIRO Manufacturing , Bayview Avenue, Clayton, Victoria 3168, Australia.
authors.forename: Roger J
authors.initials: RJ
authors.lastname: Mulder
authors.affiliation: School of Chemistry and Bio21 Molecular Science and Biotechnology Institute, University of Melbourne , 30 Flemington Road, Parkville, Victoria 3010, Australia.|Department of Biochemistry and Molecular Biology, University of Melbourne , 30 Flemington Road, Parkville, Victoria 3010, Australia.
authors.forename: Gavin E
authors.initials: GE
authors.lastname: Reid
authors.affiliation: School of Chemistry and Bio21 Molecular Science and Biotechnology Institute, University of Melbourne , 30 Flemington Road, Parkville, Victoria 3010, Australia.
authors.forename: Paul S
authors.initials: PS
authors.lastname: Donnelly
authors.affiliation: School of Chemistry and Bio21 Molecular Science and Biotechnology Institute, University of Melbourne , 30 Flemington Road, Parkville, Victoria 3010, Australia.
authors.forename: Richard A J
authors.initials: RA
authors.lastname: O'Hair