Site-specific doping of silver atoms into a Au25 nanocluster as directed by ligand binding preferences

For the first time site-specific doping of silver into a spherical Au₂₅ nanocluster has been achieved in [Au₁₉Ag₆(MeOPhS)₁₇(PPh₃)₆] (BF₄)₂ (Au₁₉Ag₆) through a dual-ligand coordination strategy. Single crystal X-ray structural analysis shows that the cluster has a distorted centered icosahedral Au@Au₆Ag₆ core of D₃ symmetry, in contrast to the I_h Au@Au₁₂ kernel in the well-known [Au₂₅(SR)₁₈]⁻ (R = CH₂CH₂Ph). An interesting feature is the coexistence of [Au₂(SPhOMe)₃] dimeric staples and [P–Au–SPhOMe] semi-staples in the title cluster, due to the incorporation of PPh₃. The observation of only one double-charged peak in ESI-TOF-MS confirms the ordered doping of silver atoms. Au₁₉Ag₆ is a 6e system showing a distinct absorption spectrum from [Au₂₅(SR)₁₈]⁻, that is, the HOMO–LUMO transition of Au₁₉Ag₆ is optically forbidden due to the P character of the superatomic frontier orbitals.

For the first time site-specific doping of silver into a spherical Au₂₅ nanocluster has been achieved in [Au₁₉Ag₆(MeOPhS)₁₇(PPh₃)₆] (BF₄)₂. It is a 6e system showing quite a different absorption spectrum from [Au₂₅(SR)₁₈]⁻.     

Rendering hydrophobic nanoclusters water-soluble and biocompatible

Hydrophobic and hydrophilic nanoclusters embody complementary superiorities. The means to amalgamate these superiorities, i.e., the atomic precision of hydrophobic clusters and the water dissolvability of hydrophilic clusters, remains challenging. This work presents a versatile strategy to render hydrophobic nanoclusters water-soluble—the micellization of nanoclusters in the presence of solvent-conjoined Na⁺ cations—which overcomes the above major challenge. Specifically, although [Ag₂₉(SSR)₁₂(PPh₃)₄]³⁻ nanoclusters are absolutely hydrophobic, they show good dissolvability in aqueous solution in the presence of solvent-conjoined Na⁺ cations (Na₁(NMP)₅ or Na₃(DMF)₁₂). Such cations act as both counterions of these nanoclusters and surface cosolvent of cluster-based micelles in the aqueous phase. A combination of DLS (dynamic light scattering) and aberration-corrected HAADF-STEM (high angle annular dark field detector scanning transmission electron microscopy) measurements unambiguously shows that the phase-transfer of hydrophobic Ag₂₉ into water is triggered by the micellization of nanoclusters. Owing to the excellent water solubility and stability of [Ag₂₉(SSR)₁₂(PPh₃)₄]³⁻[Na₁(NMP)₅]₃⁺ in H₂O, its performance in cell staining has been evaluated. Furthermore, the general applicability of the micellization strategy has been verified. Overall, this work presents a convenient and efficient approach for the preparation of cluster-based, biocompatible nanomaterials.

The presence of solvent-conjoined cations, [Na₁(NMP)₅]⁺ or [Na₃(DMF)₁₂]³⁺, induces the micellization of hydrophobic nanoclusters, rendering these nanoclusters water-soluble and biocompatible.     

Coordination Chemistry of Diiodine and Implications for the Oxidation Capacity of the Synergistic Ag+/X2 (X=Cl,Br, I) System

The synergistic Ag⁺/X₂ system (X=Cl, Br, I) is a very strong, but ill‐defined oxidant—more powerful than X₂ or Ag⁺ alone. Intermediates for its action may include [Ag_m(X₂)_n]^m+ complexes. Here, we report on an unexpectedly variable coordination chemistry of diiodine towards this direction: ( A )Ag‐I₂‐Ag( A ), [Ag₂(I₂)₄]²⁺( A ⁻)₂ and [Ag₂(I₂)₆]²⁺( A ⁻)₂⋅(I₂)_x≈0.65 form by reaction of Ag( A ) ( A =Al(OR^F)₄; R^F=C(CF₃)₃) with diiodine (single crystal/powder XRD, Raman spectra and quantum‐mechanical calculations). The molecular ( A )Ag‐I₂‐Ag( A ) is ideally set up to act as a 2 e⁻ oxidant with stoichiometric formation of 2 AgI and 2 A ⁻. Preliminary reactivity tests proved this ( A )Ag‐I₂‐Ag( A ) starting material to oxidize n‐C₅H₁₂, C₃H₈, CH₂Cl₂, P₄ or S₈ at room temperature. A rough estimate of its electron affinity places it amongst very strong oxidizers like MF₆ (M=4d metals). This suggests that ( A )Ag‐I₂‐Ag( A ) will serve as an easily in bulk accessible, well‐defined, and very potent oxidant with multiple applications.     

A Novel Concept for the Synthesis of Multiply Doped Gold Clusters [(M@AunM′m)Lk]q+

Heterometal‐doped gold clusters are poorly accessible through wet‐chemical approaches and main‐group‐metal‐ or early‐transition‐metal‐doped gold clusters are rare. Compounds [M(AuPMe₃)₁₁(AuCl)]³⁺ (M=Pt, Pd, Ni) ( 1 – 3 ), [Ni(AuPPh₃)_(8?2n)(AuCl)₃(AlCp*)_n] (n=1, 2) ( 4, 5 ), and [Mo(AuPMe₃)₈ (GaCl₂)₃(GaCl)]⁺ ( 6 ) were selectively obtained by the transmetalation of [M(M′Cp*)_n] (M=Mo, E=Ga, n=6; M=Pt, Pd, Ni, M′=Ga, Al, n=4) with [ClAuPR₃] (R=Me, Ph) and characterized by single‐crystal X‐ray diffraction and ESI mass spectrometry. DFT calculations were used to analyze the bonding situation. The transmetalation proved to be a powerful tool for the synthesis of heterometal‐doped gold clusters with a design rule based on the 18 valence electron count for the central metal atom M and in agreement with the unified superatom concept based on the jellium model.     

Platinum(II), palladium(II), nickel(II), and gold(I) complexes of the “electrospray-friendly” thiolate ligands 4-SC5H4N− and 4-SC6H4OMe−

The series of platinum(II), palladium(II), and nickel(II) complexes [ML₂(dppe)] [M = Ni, Pd, Pt; L = 4–SC₅H₄N or 4–SC₆H₄OMe; dppe = Ph₂PCH₂CH₂PPh₂] containing pyridine-4-thiolate or 4-methoxybenzenethiolate ligands, together with the corresponding gold(I) complexes [AuL(PPh₃)], were prepared and their electrospray ionization mass spectrometric behavior compared with that of the thiophenolate complexes [M(SPh)₂(dppe)] (M = Ni, Pd, Pt) and [Au(SPh)(PPh₃)]. While the pyridine-4-thiolate complexes yielded protonated ions of the type [M + H]⁺ and [M + 2H]²⁺ ions in the Ni, Pd, and Pt complexes, an [M + H]⁺ ion was only observed for the platinum derivative of 4-methoxybenzenethiolate. Other ions, which dominated the spectra of the thiophenolate complexes, were formed by thiolate loss and aggregate formation. The X-ray crystal structure of [Pt(SC₆H₄OMe–4)₂(dppe)] is also reported.     

Cation-Induced dimerization of nickel(II), platinum(II), and palladium(II) meso-tetra(benzo-15-crown-5)porphyrinates

Cation-induced dimerization of nickel(II), platinum(II), and palladium(II) meso-tetra(benzo-15-crown-5)porphyrinates (Ni(II)TCP, Pd(II)TCP, and Pt(II)TCP) on treatment with potassium thiocyanate in a chloroform-methanol solution has been studied by electronic absorption spectroscopy. The formation of [{MTCP}₂(K⁺)₄](SCN^?)₄ in solution induces a hypsochromic shift of the Soret band and a bathochromic shift of the β-band with respect to their positions in the spectrum of MTCP. The equilibrium constants (K) for the 2MTCP + 4K⁺ = [{MTCP}₂(K⁺)₄] processes at 20°C are determined to be as follows: log K _Ni(II)TCP = 27.31 ± 1.67, logK _Pd(II)TCP = 27.16 ± 1.43, and logK _Pt(II)TCP = 26.15 ± 1.56.     

Synthesen und Schwingungsspektren der homoleptischen Acetonitrilkomplex-Kationen [Au(NCCH3)2]+, [Pd(NCCH3)4]2+, [Pt(NCCH3)4]2+ und des Adduktes CH3CN · SbF5. Kristallstrukturen der Salze [M(NCCH3)4][SbF6]2 · CH3CN,M = Pd,Pt

The Syntheses and Vibrational Spectra of the Homoleptic Metal Acetonitrile Cations [Au(NCCH₃)₂]⁺, [Pd(NCCH₃)₄]²⁺, [Pt(NCCH₃)₄]²⁺, and the Adduct CH₃CN · SbF₅. The Crystal and Molecular Structures of [M(NCCH₃)₄][SbF₆]₂ · CH₃CN, M = Pd or Pt Solvolyses of the homoleptic metal carbonyl salts [M(CO)₄][Sb₂F₁₁]₂, M = Pd or Pt, in acetonitrile leads at 50 °C both to complete ligand exchange for the cations as well as to a conversion of the di-octahedral anion [Sb₂F₁₁]^– into [SbF₆]^– and the molecular adduct CH₃CN · SbF₅ according to: [M(CO)₄][Sb₂F₁₁]₂ + 7 CH₃CN → [M(NCCH₃)₄][SbF₆]₂ · CH₃CN + 2 CH₃CN · SbF₅ + 4 CO M = Pd, Pt The monosolvated [M(NCCH₃)₄][SbF₆]₂ · CH₃CN are obtained as single crystals from solution and are structurally characterized by single crystal x-ray diffraction. Both salts are isostructural. The cations are square planar but the N–C–C-sceletial groups of the ligands depart slightly from linearity. The new acetonitrile complexes as well as [Au(NCCH₃)₂][SbF₆] and the adduct CH₃CN · SbF₅ are completely characterized by vibrational spectroscopy.     

Cu Doping-Induced Transformation from [Ag62S12(SBut)32]2+ to [Ag62−xCuxS12(SBut)32]4+ Nanocluster

The change in the valence state of nanocluster can induce remarkable changes in the properties and structure. However, achieving the valence state changes in nanoclusters is still a challenge. In this work, we use Cu²⁺ as dopant to “oxidize” [Ag₆₂S₁₂(SBu^t)₃₂]²⁺ (4 free electrons) to obtain the new nanocluster: [Ag_62−xCu_xS₁₂(SBu^t)₃₂]⁴⁺ with 2 free electrons. As revealed by its structure, the [Ag_62−xCu_xS₁₂(SBu^t)₃₂]⁴⁺ (x=10∼21) has a similar structure to that of [Ag₆₂S₁₂(SBu^t)₃₂]²⁺ precursor and all the Cu atoms occupy the surface site of nanocluster. It′s worth noting that with the Cu atoms doping, the [Ag_62−xCu_xS₁₂(SBu^t)₃₂]⁴⁺ nanocluster is more stable than [Ag₆₂S₁₂(SBu^t)₃₂]²⁺ at higher temperature and in electrochemical cycle. This result has laid a foundation for the subsequent application and exploration. Overall, this work reveals crystals structure of a new Ag−Cu nanocluster and offers a new insight into the electron reduction/oxidation of nanocluster.     

Coordination Chemistry of Diiodine and Implications for the Oxidation Capacity of the Synergistic Ag+/X2 (X=Cl,Br, I) System

The synergistic Ag⁺/X₂ system (X=Cl, Br, I) is a very strong, but ill‐defined oxidant—more powerful than X₂ or Ag⁺ alone. Intermediates for its action may include [Ag_m(X₂)_n]^m+ complexes. Here, we report on an unexpectedly variable coordination chemistry of diiodine towards this direction: ( A )Ag‐I₂‐Ag( A ), [Ag₂(I₂)₄]²⁺( A ^?)₂ and [Ag₂(I₂)₆]²⁺( A ^?)₂?(I₂)_x≈0.65 form by reaction of Ag( A ) ( A =Al(OR^F)₄; R^F=C(CF₃)₃) with diiodine (single crystal/powder XRD, Raman spectra and quantum‐mechanical calculations). The molecular ( A )Ag‐I₂‐Ag( A ) is ideally set up to act as a 2 e^? oxidant with stoichiometric formation of 2 AgI and 2 A ^?. Preliminary reactivity tests proved this ( A )Ag‐I₂‐Ag( A ) starting material to oxidize n‐C₅H₁₂, C₃H₈, CH₂Cl₂, P₄ or S₈ at room temperature. A rough estimate of its electron affinity places it amongst very strong oxidizers like MF₆ (M=4d metals). This suggests that ( A )Ag‐I₂‐Ag( A ) will serve as an easily in bulk accessible, well‐defined, and very potent oxidant with multiple applications.     

Highly trifluoromethylated platinum compounds

The homoleptic, square‐planar organoplatinum(II) compound [NBu₄]₂[Pt(CF₃)₄] ( 1 ) undergoes oxidative addition of CF₃I under mild conditions to give rise to the octahedral organoplatinum(IV) complex [NBu₄]₂[Pt(CF₃)₅I] ( 2 ). This highly trifluoromethylated species reacts with Ag⁺ salts of weakly coordinating anions in Me₂CO under a wet‐air stream to afford the aquo derivative [NBu₄][Pt(CF₃)₅(OH₂)] ( 4 ) in around 75 % yield. When the reaction of 2 with the same Ag⁺ salts is carried out in MeCN, the solvento compound [NBu₄][Pt(CF₃)₅(NCMe)] ( 5 ) is obtained in around 80 % yield. The aquo ligand in 4 as well as the MeCN ligand in 5 are labile and can be cleanly replaced by neutral and anionic ligands to furnish a series of pentakis(trifluoromethyl)platinate(IV) compounds with formulae [NBu₄][Pt(CF₃)₅(L)] (L=CO ( 6 ), pyridine (py; 7 ), tetrahydrothiophene (tht; 8 )) and [NBu₄]₂[Pt(CF₃)₅X] (X=Cl ( 9 ), Br ( 10 )). The unusual carbonyl–platinum(IV) derivative [NBu₄][Pt(CF₃)₅(CO)] ( 6 ) is thermally stable and has a ν_CO of 2194 cm^?1. The crystal structures of 2? CH₂Cl₂, 5 , [PPh₄][Pt(CF₃)₅(CO)] ( 6′ ), and 7 have been established by X‐ray diffraction methods. Compound 2 has shown itself to be a convenient entry to the chemistry of highly trifluoromethylated platinum compounds. To the best of our knowledge, compounds 2 and 4 – 10 are the organoelement compounds with the highest CF₃ content to have been isolated and adequately characterized to date.     

Coordination/organometallic polymers based on diphosphine and diisocyanide ligands

This paper reviews various coordination/ organometallic polymers in which the metal atoms are incorporated in the backbone using diphosphine and diisocyanide ligands. Such ligands includes diphosphines of the type bis(diphenylphosphino)alkane where alkane is (CH₂)_m with m = 1, 3-6, bis(diphenylphosphino)acetylene (dpa), and bis(dimethylphosphino)methane (dmpm), and diisocyanides such as 1,8-diiso-cyano-p-menthane (dmb) and p-diisocyanotetra-methylbenzene (ditmb). The metal fragments are monocations such as Cu⁺, Ag⁺, and Au⁺, dinuclear species such as Pd₂(dmb)₂²⁺, Pd₂(dppm)₂²⁺, M₂(dmpm)₃²⁺ (M = Cu, Ag), and clusters such as M₄(dmb)₄²⁺ (M = Pd, Pt).     

Nature of mercury inclusion in intermediate 6-valence electron [M@Au8Hgx(PPh3)8]n+ (M = Au,Pd, Pt; x = 0-2) protected gold superatoms: Insights from relativistic density functional theory calculations

Superatomic clusters offer useful templates displaying distinctive physical and chemical characteristics. Here, we explore the [M@Au₈(PPh₃)₈]ⁿ⁺ (M = Au, n = 3; Pd, Pt, n = 2) robust framework to gain an understanding of the nature of the inclusion of mercury atoms at Au₄ faces, leading to [M@Au₈Hg_x(PPh₃)₈]ⁿ⁺ (x = 1, 2). Our results show a weak interaction of about 25 kcal mol⁻¹ per Hg atom, which is mainly of electrostatic character, followed by orbital and London dispersion-type interactions. This weak interaction can be understood as the formation of host-guest species, for which the inherent electronic and optical properties of the [M@Au₈(PPh₃)₈] cluster along the series do not vary to a large extent. This demonstrates that, in [M@Au₈Hg_x(PPh₃)₈], each Hg can be considered an inclusion atom rather than a dopant element, where the parent cluster is able to act as a Lewis acid host. Furthermore, the viable formation of such species can serve as useful examples to stimulate future experimental characterization of inclusion complexes involving related superatomic structures with available open faces.     

Binuclear platinum(I) complexes with bis(dimethylphosphino)methane ligands: evidence for both short- and long-range NMR trans-influences

The diplatinum(I) complexes or complex ions [Pt₂X₂(μ-dmpm)₂] (X = Cl or I), [Pt₂X(PPh₃)(μ-dmpm)₂]⁺] (X = I, Br or Me), and [Pt₂(PPh₃)₂(μ-dmpm)₂]²⁺, where dmpm = Me₂PCH₂PMe₂, have been prepared and characterized by ¹H and ³¹P NMR spectroscopy. In the linear X-Pt-Pt-Y unit the trans-influence of X is felt primarily at the PtPt bond, but groups X having a very high trans-influence (X = H or Me) can also exert a weaker long-range trans-influence on the PtY bond.     

Camouflaging Structural Diversity: Co‐crystallization of Two Different Nanoparticles Having Different Cores But the Same Shell

Two ligand‐protected nanoscale silver moieties, [Ag₄₆(SPhMe₂)₂₄(PPh₃)₈](NO₃)₂ and [Ag₄₀(SPhMe₂)₂₄(PPh₃)₈](NO₃)₂ (abbreviated as Ag₄₆ and Ag₄₀, respectively) with almost the same shell but different cores were synthesized simultaneously. As their external structures are identical, the clusters were not distinguishable and become co‐crystallized. The occupancy of each cluster was 50 %. The outer shell of both is composed of Ag₃₂S₂₄P₈, which is reminiscent of fullerenes, and it encapsulates a well‐studied core, Ag₁₄ and a completely new core, Ag₈, which correspond to a face‐centered cube and a simple cube, respectively, resulting in the Ag₄₆ and Ag₄₀ clusters. The presence of two entities (Ag₄₀ and Ag₄₆ clusters) in a single crystal and their molecular formulae were confirmed by detailed electrospray ionization mass spectrometry. The optical spectrum of the mixture showed unique features which were in good agreement with the results from time‐dependent density functional theory (TD‐DFT).     

Luminescence Regulation of Silver‐Thiolate Clusters Protected by 1,2‐Dithiolate‐o‐carborane

Engineering the surface of the metal clusters with the core structure maintained and tuning their luminescence in a wide range is still a challenge in the nanomaterial research. We modified six mono‐pyridyl ligands with different electronic effects (conjugation effect or induction effect) on a superatomic silver cluster [Ag₁₄(C₂B₁₀H₁₀S₂)₆(CH₃CN)₈] (denoted as Ag₁₄) through in situ site‐specific surface engineering, and obtained the corresponding clusters [Ag₁₄(C₂B₁₀H₁₀S₂)₆(CH₃CN)₆(L₁/L₂)₂] (denoted as NC‐1, 2, L₁/L₂ = 4‐acetylpyridine/ 4‐carboxypyridine) and [Ag₁₄(C₂B₁₀H₁₀S₂)₆(L₃/L₄/L₅/L₆)₈] (denoted as NC‐3, 4, 5, 6, L₃/L₄/L₅/L₆ = 4‐phenylpyridine/4‐(1‐naphthyl)pyridine/9‐(4‐pyridine)anthracene/9‐(4‐pyridine)pyrene). Through the modification of the Ag₁₄ cluster, a wide‐range luminescence from blue to red was realized. This work might provide a practical guide for improving the emission performance of metal clusters via surface engineering.     

Alternating Array Stacking of Ag26Au and Ag24Au Nanoclusters

An assembly strategy for metal nanoclusters using electrostatic interactions with weak interactions, such as C?H???π and π???π interactions in which cationic [Ag₂₆Au(2‐EBT)₁₈(PPh₃)₆]⁺ and anionic [Ag₂₄Au(2‐EBT)₁₈]^? nanoclusters gather and assemble in an unusual alternating array stacking structure is presented. [Ag₂₆Au(2‐EBT)₁₈(PPh₃)₆]⁺ [Ag₂₄Au(2‐EBT)₁₈]^? is a new compound type, a double nanocluster ion compound (DNIC). A single nanocluster ion compound (SNIC) [PPh₄]⁺ [Ag₂₄Au(2‐EBT)₁₈]^? was also synthesized, having a k‐vector‐differential crystallographic arrangement. [PPh₄]⁺ [Ag₂₄Au(2,4‐DMBT)₁₈]^? adopts a different assembly mode from both [Ag₂₆Au(2‐EBT)₁₈(PPh₃)₆]⁺ [Ag₂₄Au(2‐EBT)₁₈]^? and [PPh₄]⁺ [Ag₂₄Au(2‐EBT)₁₈]^?. Thus, the striking packing differences of [Ag₂₆Au(2‐EBT)₁₈(PPh₃)₆]⁺ [Ag₂₄Au(2‐EBT)₁₈]^?, [PPh₄]⁺ [Ag₂₄Au(2‐EBT)₁₈]^? and the existing [PPh₄]⁺ [Ag₂₄Au(2,4‐DMBT)₁₈]^? from each other indicate the notable influence of ligands and counterions on the self‐assembly of nanoclusters.     

Das SCN–-Ion als ambidenter Ligand – Synthese und Kristallstrukturen von (Bu4N)4[Ag2Fe2(SCN)12] und (Et4N)2 [Ag2Fe(SCN)6]

The SCN^– Ion as an Ambidentate Ligand – Synthesis and Crystal Structures of (Bu₄N)₄[Ag₂Fe₂(SCN)₁₂] and (Et₄N)₂ [Ag₂Fe(SCN)₆] In (Bu₄N)₄[Ag₂Fe₂(SCN)₁₂] · 2 CH₃NO₂ ( 1 ) and (Et₄N)₂[Ag₂Fe(SCN)₆] ( 2 ) the ambidentate SCN^– anions link Ag⁺ with Fe³⁺ and Fe²⁺ centers, respectively. The tetranuclear anions in 1 are built from [Fe(NCS)₆]^3– groups connected by Ag⁺ ions. In 2 the same bridging pattern leads to polymeric anionic chains containing [Fe(NCS)₆]^4– groups linked by Ag⁺ ions. (Bu₄N)₄[Ag₂Fe₂(SCN)₁₂] · 2 CH₃NO₂ ( 1 ): a = 1184.10(10), b = 1370.80(10), c = 1776.5(2) pm, α = 99.090(10), β = 102.100(10), γ = 100.360(10)°, V = 2715.5(4) · 10⁶ pm³, space group P1; (Et₄N)₂[Ag₂Fe(SCN)₆] ( 2 ): a = 1607.0(2), b = 1006.92(9), c = 1096.13(9) pm, V = 1773.7(3) · 10⁶ pm³, space group Pnnm.     

Photocatalytic Reduction of Ag2SO4 by Dawson-Derived Sandwich Complex

Photocatalytic reduction of Ag^I₂SO₄ from aqueous solutions is observed in the presence of Dawson-derived sandwich type polyoxometalates (POMs) [M₄(P₂W₁₅O₅₆)₂]¹⁶⁻, M = Co²⁺, Ni²⁺ and Zn²⁺ as photocatalyst and an organic substrate (propan-2-ol) as sacrificial electron donor. The direct photochemical excitation of the Dawson-derived sandwich type polyoxometalates in the presence of propan-2-ol leads to its reduction. That first reduction step induces electron transfer to Ag⁺ ions to give Ag⁰ metal atoms which then form by aggregation colloidal metal nanoparticles stabilized by POM. In the case of [Co₄(P₂W₁₅O₅₆)₂]¹⁶⁻, TEM experiments reveal that the Ag_n particles obtained with a slight excess of Ag⁺ are almost spherical with size in the range 20 – 50 nm. However, in a large excess of Ag⁺, the obtained colloids are more oblate and assembled together to give larger aggregates.     

Altering Charges on Heterobimetallic Transition-Metal Carbonyl Clusters

The homoleptic group 5 carbonylates [M(CO)₆]⁻ (M=Nb, Ta) serve as ligands in carbonyl-terminated heterobimetallic Ag_mM_n clusters containing 3 to 11 metal atoms. Based on our serendipitous [Ag₆{Nb(CO)₆}₄]²⁺ ( 4 a ²⁺) precedent, we established access to such Ag_mM_n clusters of the composition [Ag_m{M(CO)₆}_n]^x (M=Nb, Ta; m=1, 2, 6; n=2, 3, 4, 5; x=1−, 1+, 2+). Salts of those molecular cluster ions were synthesized by the reaction of [NEt₄][M(CO)₆] and Ag[Al(OR^F)₄] (R^F=C(CF₃)₃) in the correct stoichiometry in 1,2,3,4-tetrafluorobenzene at −35 °C. The solid-state structures were determined by single-crystal X-ray diffraction methods and, owing to the thermal instability of the clusters, a limited scope of spectroscopic methods. In addition, DFT-based AIM calculations were performed to provide an understanding of the bonding within these clusters. Apparently, the clusters 3 ⁺ (m=6, n=5) and 4 ²⁺ (m=6, n=4) are superatom complexes with trigonal-prismatic or octahedral Ag₆ superatom cores. The [M(CO)₆]⁻ ions then bind through three CO units as tridentate chelate ligands to the superatom core, giving overall structures related to tetrahedral AX₄ ( 4 ²⁺) or trigonal bipyramidal AX₅ molecules ( 3 ⁺).     

Electrospray mass spectrometric studies of the complexational behavior of maleonitrile thiacrown ethers with various metals

Electrospray ionization was employed to study the mass spectrometric behavior of the maleonitrile tetrathiacrown ethers mn12S₄ (1) and mn13S₄ (2) and maleonitrile pentathiacrown ether mn15S₅ (3) and of their complexes with various metal salts (MX₂, M = Pd, Pt, Ni, Co, Fe; X = Cl, CrCl₃, Ni(BF₄)₂, TlPF₆ or Cd(NO₃)₂) and Cu(SO₃CF₃)₂. Both singly charged, [MXL]⁺ and [MXL₂]⁺, and doubly charged complexes, [ML_n]²⁺ (n = 2–5), were observed. The formation of the different complexes consisting of the transition metal ion, the counterion and the various crown ethers and their subsequent dissociation was also studied by collision‐induced dissociation measurements which were also used to evaluate the relative stabilities of the complexes. It was found that the collisional voltages for the dissociation of the complexes were generally greater in the [MXL]⁺ complexes than in the corresponding [MXL₂]⁺ complexes. Copyright © 2006 John Wiley & Sons, Ltd.