Atomically Precise Ni-Pd Alloy Carbonyl Nanoclusters: Synthesis, Total Structure, Electrochemistry, Spectroelectrochemistry, and Electrochemical Impedance Spectroscopy

The molecular nanocluster [Ni36-xPd5+x(CO)46]6- (x = 0.41) (16-) was obtained from the reaction of [NMe3(CH2Ph)]2[Ni6(CO)12] with 0.8 molar equivalent of [Pd(CH3CN)4][BF4]2 in tetrahydrofuran (thf). In contrast, [Ni37-xPd7+x(CO)48]6- (x = 0.69) (26-) and [HNi37-xPd7+x(CO)48]5- (x = 0.53) (35-) were obtained from the reactions of [NBu4]2[Ni6(CO)12] with 0.9-1.0 molar equivalent of [Pd(CH3CN)4][BF4]2 in thf. After workup, 35- was extracted in acetone, whereas 26- was soluble in CH3CN. The total structures of 16-, 26-, and 35- were determined with atomic precision by single-crystal X-ray diffraction. Their metal cores adopted cubic close packed structures and displayed both substitutional and compositional disorder, in light of the fact that some positions could be occupied by either Ni or Pd. The redox behavior of these new Ni-Pd molecular alloy nanoclusters was investigated by cyclic voltammetry and in situ infrared spectroelectrochemistry. All three compounds 16-, 26-, and 35- displayed several reversible redox processes and behaved as electron sinks and molecular nanocapacitors. Moreover, to gain insight into the factors that affect the current-potential profiles, cyclic voltammograms were recorded at both Pt and glassy carbon working electrodes and electrochemical impedance spectroscopy experiments performed for the first time on molecular carbonyl nanoclusters

The chemistry of htdridocarbonylferrates revisited: syntheses and structures of the new [H2Fe4(CO)12]2– and [HFe5(CO)14]3– amions, and the [Fe(DMF)4][Fe4(CO)12(6-2-CO)(-H)]2 adduct containing an unprecedented isocarbonyl

The di-hydride di-anion [H2Fe4(CO)(12)](2-) has been quantitatively obtained by protonation of the previously reported mono-hydride tri-anion [HFe4(CO)(12)](3-) in DMSO and structurally characterised in its [NEt4](2)[H2Fe4(CO)(12)] salt. It shows some subtle but yet significant differences in the stereochemistry of the ligands in comparison to the heavier Ru-4 and Os-4 congeners. The study of the reactivity of these [H4-nFe4(CO)(12)](n-) (n = 2,3) species allowed the serendipitous isolation and structural characterization of the new pentanuclear [HFe5(CO)(14)](3-) mono-hydride tri-anion. Attempts to obtain the latter in better yields led to the discovery of intermolecular CO/H- mutual exchange reactions and isolation and structural characterization of the [Fe(DMF)(4)][Fe-4(CO)(12)(mu(5)-eta(2)-CO)(mu-H)](2)center dot 0.5CH(2)Cl(2) and [M+][Fe-4(CO)(12)(mu(4)-eta(2)-CO)(mu-H)](-) (M = K, Cs) adducts, the former containing an unprecedented isocarbonyl group. The isolation of new tetranuclear and, above all, pentanuclear hydridocarbonylferrates indicates that it is possible to further expand the chemistry of homoleptic Fe carbonyl specie

Synthesis, molecular structure and fluxional behavior of the elusive [HRu4(CO)12]3− carbonyl anion

The elusive mono-hydride tri-anion [HRu4(CO)12]3− (4) has been isolated and fully characterized for the first time. Cluster 4 can be obtained by the deprotonation of [H3Ru4(CO)12]− (2) with NaOH in DMSO. A more convenient synthesis is represented by the reaction of [HRu3(CO)11]− (6) with an excess of NaOH in DMSO. The molecular structure of 4 has been determined by single-crystal X-ray diffraction (SC-XRD) as the [NEt4]3[4] salt. It displays a tetrahedral structure of pseudo C3v symmetry with the unique hydride ligand capping a triangular Ru3 face. Variable temperature (VT) 1H and 13C{1H} NMR experiments indicate that 4 is fluxional in solution and reveal an equilibrium between the C3v isomer found in the solid state and a second isomer with Cs symmetry. Protonation–deprotonation reactions inter-converting H4Ru4(CO)12 (1), [H3Ru4(CO)12]− (2), [H2Ru4(CO)12]2− (3), [HRu4(CO)12]3− (4) and the purported [Ru4(CO)12]4− (5) have been monitored by IR and 1H NMR spectroscopy. Whilst attempting the optimization of the synthesis of 4, crystals of [NEt4]2[Ru3(CO)9(CO3)] ([NEt4]2[7]) were obtained. Anion 7 contains an unprecedented CO32− ion bonded to a zero-valent Ru3(CO)9 fragment. Finally, the reaction of 6 as the [N(PPh3)2]+ ([PPN]+) salt with NaOH in DMSO affords [Ru3(CO)9(NPPh3)]− (9) instead of 4. Computational DFT studies have been carried out in order to support experimental evidence and the location of the hydride ligands as well as to shed light on possible isomer

Mercurophilic interactions in heterometallic Ru-Hg carbonyl clusters

The reaction of [HRu3(CO)11]– (1) with 0.35 mol equivalents of Hg(CH3CO2)2 afforded [HgRu6(CO)22]2– (3), whereas a mixture of 3 and [Hg2Ru7(CO)26]2– (4) was obtained using 0.5 mol equivalents of Hg(CH3CO2)2 per mole of 1. A few crystals of [Ru3(CO)10(CH3COO)]– (7) were obtained as side products of the latter reaction. The reaction of 1 with one mole equivalent of Hg(CH3CO2)2 or HgCl2 afforded [Hg3Ru8(CO)30]2– (5) as the major product. By employing HgCl2, formation of 5 was accompanied by traces of the new homometallic cluster [Ru2Cl4(CO)5]2– (8). [HRu4(CO)12]3– (2) reacted with one mole equivalent of HgCl2 resulting in [Hg4Ru10(CO)32]4– (6). The molecular structures of the new clusters 3–8 were determined by single crystal X-ray diffraction (SC-XRD) as their [NEt4]2[3], [NEt4]2[4]·0.5CH2Cl2, [NEt4]2[5], [NEt4]4[6], [NEt4][7], [NEt4]2[8]·0.5CH3CN salts. Heterometallic Ru-Hg clusters 3–6 contain [Hg]2+, [Hg2]4+, [Hg3]6+, and [Hg4]8+ cores stabilized by [Ru(CO)4]2–, [Ru3CO)11]2– and [Ru4(CO)12]4– fragments. Metal-metal bonds were investigated by DFT calculations and atoms-in-molecules (AIM) analyses