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

1H NMR global diatropicity in copper hydride complexes

Understanding the magnetic response of electrons in nanoclusters is essential to interpret their NMR spectra thereby providing guidelines for their synthesis towards various target applications. Here, we consider two copper hydride clusters that have applications in hydrogen storage and release under standard temperature and pressure. Through Born-Oppenheimer molecular dynamics simulations, we study dynamics effects and their contributions to the NMR peaks. Finally, we examine the electrons' magnetic response to an applied external magnetic field using the gauge-including magnetically induced currents theory. Local diatropic currents are generated in both clusters but an interesting global diatropic current also appears. This diatropic current has contributions from three μ₃-H hydrides and six Cu atoms that form a chain together with three S atoms from the closest ligands resulting in a higher shielding of these hydrides' ¹H NMR response. This explains the unusual upfield chemical shift compared to the common downfield shift in similarly coordinated hydrides both observed in previous experimental reports.

Electrospray Ionization Tandem Mass Spectrometry and DFT Survey of Copper(I) Ate Complexes Containing Coordinated Borohydride Anions

Copper(I) borohydride ate complexes of the type Cat⁺[XCu(BH₄)]^- have been previously postulated as intermediates in the reactions of copper salts with borohydride. Negative ion electrospray ionization of an acetonitrile solution of copper(I) phenylacetylide with a 10-fold excess of sodium borohydride (NaBH₄) revealed the formation of a diverse range of mononuclear, dinuclear and trinuclear cuprates with different numbers of BH₄^-, H^- and CN^- ligands, the latter likely being formed by abstraction of CN^- from the acetonitrile solvent. Collision-induced dissociation was used to examine the fragmentation reactions of the following borohydride containing cuprates: [Cu(H)(BH₄)]^-, [Cu(BH₄)₂]^-, [Cu(BH₄)(CN)]^-, [Cu₂(H)(BH₄)₂]^-, [Cu₂(H)₂(BH₄)]^-, [Cu₂(BH₄)₂(CN)]^-, [Cu₂(H)(BH₄)(CN)]^-, [Cu₃(H)(BH₄)₃]^-, [Cu₃(H)₂(BH₄)₂]^-, [Cu₃(H)₃(BH₄)]^-, [Cu₃(BH₄)₂(CN)₂]^-, and [Cu₃(H)(BH₄)₂(CN)]^-. In all cases, BH₃ loss is observed. For many of the dinuclear and trinuclear complexes cluster fragmentation by loss of CuH was also observed. In the case of [Cu₂(H)₂(BH₄)]^- and [Cu₃(H)₃(BH₄)]^-, loss of H₂ was also observed. DFT calculations were used to explore potential structures of the various borohydride-containing cuprates and to predict the overall reaction energetics for the various fragmentation channels.

Dissection of bicapped octahedral copper hydride cluster to form two chiral tetrahedral copper hydride cluster series exhibiting auto deracemization and photoluminescence

Three series of copper hydride clusters [Cu₈H₆L₆]²⁺ (1), [Cu₄HX₂L₄]⁺ where X^- = Cl^- (2a), Br^- (2b), I^- (2c), N₃^- (2d) and SCN^- (2e), and [Cu₄HX₃L₃] where X^- = Br^- (3b) and I^- (3c) (L = 2-(diphenylphosphino)pyridine, dppy) were synthesized and characterized by single-crystal X-Ray crystallography and standard spectroscopic techniques. The metal core of 1, Cu₈, can be described as a bicapped octahedron, while those of 2 and 3 series adopt tetrahedral structures. The hydride positions were deduced from difference electron density maps and corroborated by NMR and DFT calculations. For 1, there are two μ₄-H^-, one each in the two tetrahedral cavities of the two capping atoms and four μ₃-H^- on the six triangular faces around the waist of the octahedron. For [Cu₄HX₂L₄]⁺ and [Cu₄HX₃L₃] series, the single μ₄-H^- resides in the center of the Cu₄ tetrahedron. It was found that these three series of copper clusters are intimately connected and can convert from one to another under specific reaction conditions. Their transformation pathways were investigated in detail. Spontaneous resolution to form optically pure enantiomeric single crystals was observed for [Cu₄H(SCN)₂L₄]⁺ (2e) and [Cu₄HBr₃L₃] (3b). Photoluminescence was observed for [Cu₄HX₂L₄]⁺, as well as [Cu₄HX₃L₃] with strong emissions from green to yellow regions.

Using electrospray ionization-tandem mass spectrometry to explore formation and gas-phase chemistry of silver nanoclusters generated from the reaction of silver salts with NaBH4 in the presence of bis(diphenylarsino)methane

Electrospray ionization-mass spectrometry (ESI-MS) of mixtures of AgBF4 or AgNO3 with the capping ligand bis(diphenylarsino)methane ((Ph2 As)2 CH2 = dpam) in a solution of acetonitrile revealed the formation of the following cations: [Ag(CH3 CN)(dpam)]+ , [Ag(dpam)2 ]+ , [Ag2 (Cl)(dpam)2 ]+ , and [Ag3 (Cl)2 (dpam)3 ]+ . Addition of NaBH4 to these solutions results in the formation of the cluster cations [Ag2 (BH4 )(dpam)2 ]+ , [Ag2 (BH4 )(dpam)3 ]+ , [Ag3 (H)(BH4 )(dpam)3 ]+ , [Ag3 (BH4 )2 (dpam)3 ]+ , [Ag3 (H)(Cl)(dpam)3 ]+ , and [Ag3 (I)(BH4 )(dpam)3 ]+ , as established by ESI-MS. Use of NaBD4 confirmed that borohydride is the source of the hydride in these clusters. An Orbitrap Fusion LUMOS mass spectrometer was used to explore the gas-phase unimolecular chemistry of selected clusters via multistage mass spectrometry (MSn ) experiments employing low-energy collision-induced dissociation (CID) and high-energy collision-induced dissociation (HCD) experiments. The borohydride containing clusters fragment via two competing pathways: (i) ligand loss and (ii) B-H bond activation involving BH3 loss. Density functional theory (DFT) calculations were used to calculate the energetics of the optimized structures for all precursor ions, fragment ions, and neutrals and to estimate the reaction endothermicities. Generally, there is reasonable agreement between the most abundant product ion formed and the predicted endothermicity of the associated reaction channel. The DFT calculations predicted that the novel dimer [Ag2 (BH4 )(dpam)2 ]+ has a paddlewheel structure in which the dpam and BH4 - ligands bridge both silver centers.

Hydride, chloride, and bromide show similar electronic effects in the Au9(PPh3)83+ nanocluster

Hydride and halide ligands in gold nanoclusters exhibit an unexpected similar electronic relationship, suggesting an underlying chemical linkage between them.

Structural characterization and gas-phase studies of the [Ag10H8(L)6]2+ nanocluster dication

The reactions between silver salts and borohydrides produce a rich set of products that range from discrete mononuclear compounds through to silver nanoparticles and colloids. Previous studies using electrospray ionization mass spectrometry (ESI-MS) to track the cationic products in solutions containing sodium borohydride, silver(i) tetrafluoroborate and the bisphosphine ligands, L, bis(diphenylphosphino)methane (dppm) and bis(diphenylphosphino)amine (dppa) have identified the dications [Ag₁₀H₈(L)₆]²⁺. Here we isolate and structurally characterize [Ag₁₀H₈(dppa)₆](BF₄)₂, and [Ag₁₀H₈(dppa)₆](NO₃)₂via X-ray crystallography. Both dications have nearly identical structural features consisting of a Ag₁₀ scaffold with the atoms lying on vertices of a bicapped square antiprism. DFT calculations were carried out to suggest potential sites for the hydrides. Ion-mobility mass spectrometry experiments revealed that [Ag₁₀H₈(dppa)₆]²⁺ and [Ag₁₀H₈(dppm)₆]²⁺ have similar collision cross sections, while multistage mass spectrometry experiments were used to compare their unimolecular gas-phase chemistry. Although the same initial sequential ligand loss followed by cluster fission and H₂ evolution is observed, the more acidic N-H of the dppa provides a more labile H for H₂ loss and H/D scrambling processes as revealed by isotope labelled experiments.

Cooperative H2 Activation on Dicopper(I) Facilitated by Reversible Dearomatization of an "Expanded PNNP Pincer" Ligand

A naphthyridine-derived expanded pincer ligand is described that can host two copper(I) centers. The proton-responsive ligand can undergo reversible partial and full dearomatization of the naphthyridine core, which enables cooperative activation of H2 giving an unusual butterfly-shaped Cu4 H2 complex.

Embryonic brass: pseudo two electron Cu/Zn clusters

The isoelectronic M₇ clusters [Cu₃Zn₄](Cp*)₅ and {[Cu₂Zn₅](Cp*)₅}⁺ were isolated as unique species pushing the boundaries of the Wade–Mingos rules.

The isoelectronic M₇ clusters [Cu₃Zn₄](Cp*)₅ (1) and {[Cu₂Zn₅](Cp*)₅}⁺ (2) are described. While 1 can be isolated only as a minor side product from the reaction of Cu(CH₃CO₂) with equimolar amounts of [Zn₂Cp*₂] with the trigonal cluster [CuZn₂](Cp*)₃ as the major product, 2 is available in acceptable yields from the reaction of [CuZn₂](Cp*)₃ with the Cp*Zn₂-transfer-reagent [Cp*Zn₂(Et₂O)₃][BAr₄^F]. The trigonal bipyramidal Cu/Zn-clusters exhibit exceptional bonding situations: with formally only one skeleton electron pair they can be regarded as highly electron deficient. However, a detailed DFT analysis reveals that the cluster bonding is supported by 3d orbital contributions of the trigonal metal base unit. The data contribute to the development of an advanced tool-box for synthesis of Hume-Rothery intermetallic (e.g. brass) inspired clusters.

Oxidation States, Stability, and Reactivity of Organoferrate Complexes

We have applied a combination of electrospray-ionization mass spectrometry, electrical conductivity measurements, and Mössbauer spectroscopy to identify and characterize the organoferrate species R _nFe _m^- formed upon the transmetalation of iron precursors (Fe(acac)₃, FeCl₃, FeCl₂, Fe(OAc)₂) with Grignard reagents RMgX (R = Me, Et, Bu, Hex, Oct, Dec, Me₃SiCH₂, Bn, Ph, Mes, 3,5-(CF₃)₂-C₆H₃; X = Cl, Br) in tetrahydrofuran. The observed organoferrates show a large variety in their aggregation (1 ≤ m ≤ 8) and oxidation states (I to IV), which are chiefly determined by the nature of their organyl groups R. In numerous cases, the addition of a bidentate amine or phosphine changes the distributions of organoferrates and affects their stability. Besides undergoing efficient intermolecular exchange processes, several of the probed organoferrates react with organyl (pseudo)halides R'X (R' = Et, ⁱPr, Bu, Ph, p-Tol; X = Cl, Br, I, OTf) to afford heteroleptic complexes of the type R₃FeR'^-. Gas-phase fragmentation of most of these complexes results in reductive eliminations of the coupling products RR' (or, alternatively, of R₂). This finding indicates that iron-catalyzed cross-coupling reactions may proceed via such heteroleptic organoferrates R₃FeR'^- as intermediates. Gas-phase fragmentation of other organoferrate complexes leads to β-hydrogen eliminations, the loss of arenes, and the expulsion of organyl radicals. The operation of both one- and two-electron processes is consistent with previous observations and contributes to the formidable complexity of organoiron chemistry.

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 AgBF₄, bis(diphenylphosphino)amine (dppa = (Ph₂P)₂NH = L^Ph) and NaBH₄ in acetonitrile.

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

[Cu₃(μ₃-H)(μ₃-BH₄)((PPh₂)₂NH)₃](BF₄) reacts with CS₂ to produce [Cu₃(μ₃-H)(μ₂,μ₁-S₂CH)((PPh₂)₂NH)₃](BF₄), whose cation loses CH₂S upon ligand loss.

Mono- and polynuclear Ag(i) complexes of N-functionalized bis(diphenylphosphino)amine DPPA-type ligands: synthesis, solid-state structures and reactivity

DPPA-type ligands (Ph₂P)₂N(p-Z)C₆H₄ (Z = H, SMe, OMe) led to Ag(i) complexes of various nuclearities and an unexpected influence of the para-substituent Z is observed, including for CH₂Cl₂ activation.