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

[Image: see text] The molecular nanocluster [Ni(36–x)Pd(5+x)(CO)(46)](6–) (x = 0.41) (1(6–)) was obtained from the reaction of [NMe(3)(CH(2)Ph)](2)[Ni(6)(CO)(12)] with 0.8 molar equivalent of [Pd(CH(3)CN)(4)][BF(4)](2) in tetrahydrofuran (thf). In contrast, [Ni(37–x)Pd(7+x)(CO)(48)](6–) (x = 0.69) (2(6–)) and [HNi(37–x)Pd(7+x)(CO)(48)](5–) (x = 0.53) (3(5–)) were obtained from the reactions of [NBu(4)](2)[Ni(6)(CO)(12)] with 0.9–1.0 molar equivalent of [Pd(CH(3)CN)(4)][BF(4)](2) in thf. After workup, 3(5–) was extracted in acetone, whereas 2(6–) was soluble in CH(3)CN. The total structures of 1(6–), 2(6–), and 3(5–) 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 1(6–), 2(6–), and 3(5–) 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.