Hexa- and Octanuclear Heterometallic Clusters with Copper–, Silver–, or Gold–Molybdenum Bonds and d10–d10 Interactions

Peraurated ruthenium hydride carbonyl clusters: aurophilicity, isolobal analogy, structural isomerism, and fluxionality

The stepwise addition of increasing amounts of Au(PPh3)Cl to [HRu4(CO)12]3- (1) results in the sequential formation of [HRu4(CO)12(AuPPh3)]2- (2), [HRu4(CO)12(AuPPh3)2]- (3), and HRu4(CO)12(AuPPh3)3 (4). Alternatively, 4 can be obtained upon addition of HBF4·Et2O (two mole equivalents) to 3. Further addition of acid to 3 (three mole equivalents) results in the formation of the tetra-aurated cluster Ru4(CO)12(AuPPh3)4 (5). Compounds 2-5 have been characterized by IR, 1H and 31P{1H} NMR spectroscopies. Moreover, the molecular structures of 3-5 have been determined by single crystal X-ray diffraction as [NEt4][3]·2CH2Cl2, 4-b·2CH2Cl2, 4-a, 5·0.5CH2Cl2·solv, and 5·solv crystalline solids. Two different isomers of 4, that is 4-a and 4-b, have been crystallographically characterized and their rapid interconversion in solution was studied by variable temperature 1H and 31P{1H} NMR spectroscopies. Weak aurophilic Au⋯Au contacts have been detected in the solid state structures of 3-5. Computational studies have been performed in order to elucidate bonding and isomerism, as well as to predict the possible structure of the elusive species 2.

Thermal Growth of Au-Fe Heterometallic Carbonyl Clusters Containing N-Heterocyclic Carbene and Phosphine Ligands

The thermal reactions of [NEt₄][Fe(CO)₄(AuNHC)] [NHC = IMes ([NEt₄][1]) or IPr ([NEt₄][2]); IMes = C₃N₂H₂(C₆H₂Me₃)₂; IPr = C₃N₂H₂(C₆H₃ⁱPr₂)₂], Fe(CO)₄(AuNHC)₂ [NHC = IMes (3) or IPr (4)], Fe(CO)₄(AuIMes)(AuIPr) (5), and Fe(CO)₄(AuNHC)(AuPPh₃) [NHC = IMes (6) or IPr (7)] were investigated in different solvents [CH₂Cl₂, CH₃CN, dimethylformamide, and dimethyl sulfoxide (dmso)] and at different temperatures (50-160 °C) in an attempt to obtain higher-nuclearity clusters. 1 and 2 completely decomposed in refluxing CH₂Cl₂, resulting in [Fe₂(CO)₈(AuNHC)]^- [NHC = IMes (10) or IPr (11)]. Traces of [Fe₃(CO)₁₀(CCH₃)]^- (12) were obtained as a side product. Conversely, 6 decomposed in refluxing CH₃CN, affording the new cluster [Au₃{Fe(CO)₄}₂(PPh₃)₂]^- (15). The relative stability of the two isomers found in the solid state structure of 15 was computationally investigated. 4 was very stable, and only after prolonged heating above 150 °C in dmso was limited decomposition observed, affording small amounts of [Fe₃S(CO)₉]^2- (9), [HFe(CO)₄]^- (16), and [Au₁₆S{Fe(CO)₄}₄(IPr)₄]ⁿ⁺ (17). A dicationic nature for 17 was proposed on the basis of density functional theory calculations. All of the other reactions examined led to species that were previously reported. The molecular structures of the new clusters 11, 12, 15, and 17 were determined by single-crystal X-ray diffraction as their [NEt₄][11]·1.5toluene, [Au(IMes)₂][15]·0.67CH₂Cl₂, [NEt₄][12], and [17][BF₄]_n·solvent salts, respectively.

Shedding light on the bonding situation of triangular and square heterometallic clusters: computational insight

DFT calculations reproduced the experimentally observed out-of-plane distortions in heterometallic clusters [MMoCp(CO)₃]_n (M = Cu⁺, Ag⁺ or Au⁺, n = 3 or 4); (Cp = η⁵-C₅H₅), while EDA analysis gives new insights into bonding situations.

Polymerization Isomerism in [{MFe(CO)4} n] n- (M = Cu, Ag, Au; n = 3, 4) Molecular Clusters Supported by Metallophilic Interactions

Triangular clusters [{MFe(CO)₄}₃]^3- (M = Cu, 4; Ag, 5; Au, 6) were selectively obtained by heating Fe(CO)₄(MIMes)₂ (M = Cu, 1; Ag, 2; Au, 3; IMes = C₃N₂H₂(C₆H₂Me₃)₂). 1-3 were synthesized by reacting Na₂[Fe(CO)₄]·2thf with 2 equiv of M(IMes)Cl. As previously described, the direct reactions of Na₂[Fe(CO)₄]·2thf with one equivalent of M(I) salts resulted in the triangular cluster [{CuFe(CO)₄}₃]^3- for Cu, whereas the square clusters [{MFe(CO)₄}₄]^4- were formed for Ag and Au. Thus, depending on the synthetic protocol adopted, both the triangular [{MFe(CO)₄}₃]^3- and square [{MFe(CO)₄}₄]^4- polymerization isomers can be selectively obtained, at least for Ag and Au. Polymerization isomerism, that is two compounds having the same elemental compositions but different molecular weights, was investigated in [{MFe(CO)₄} _n] ^n- ( n = 3, 4; M = Cu, Ag, Au) by means of structural and theoretical methods and the role of metallophilic interactions was computationally studied by means of the atoms-in-molecules (AIM) approach.

The Triple-Decker Complex [Cp*Fe(µ,η⁵:η⁵-P₅)Mo(CO)₃] as a Building Block in Coordination Chemistry

Although the triple-decker complex [Cp*Fe(µ,η⁵:η⁵-P₅)Mo(CO)₃] (2) was first reported 26 years ago, its reactivity has not yet been explored. Herein, we report a new high-yielding synthesis of 2 and the isolation of its new polymorph (2’). In addition, we study its reactivity towards Ag^I and Cu^I ions. The reaction of 2 with Ag[BF₄] selectively produces the coordination compound [Ag{Cp*Fe(µ,η⁵:η⁵-P₅)Mo(CO)₃}₂][BF₄] (3). Its reaction with Ag[TEF] and Cu[TEF] ([TEF]⁻ = [Al{OC(CF₃)₃}₄]⁻) leads to the selective formation of the complexes [Ag{Cp*Fe(µ,η⁵:η⁵-P₅)Mo(CO)₃}₂][TEF] (4) and [Cu{Cp*Fe(µ,η⁵:η⁵-P₅)Mo(CO)₃}₂][TEF] (5), respectively. The X-ray structures of compounds 3–5 each show an M^I ion (M^I = Ag^I, Cu^I) bridged by two P atoms from two triple-decker complexes (2). Additionally, four short M^I···CO distances (two to each triple-decker complex 2) participate in stabilizing the coordination sphere of the M^I ion. Evidently, the X-ray structure for compound 3 shows a weak interaction of the Ag^I ion with one fluorine atom of the counterion [BF₄]⁻. Such an Ag···F interaction does not exist for compound 4. These findings demonstrate the possibility of using triple-decker complex 2 as a ligand in coordination chemistry and opening a new perspective in the field of supramolecular chemistry of transition metal compounds with phosphorus-rich complexes.