Heterometallic Ru–Ir Hydride Carbonyl Clusters

[NEt₄][Ru₃(µ-H)(µ-CO)(CO)₁₀] (1) reacts with [{Ir(µ-Cl)(cod)}₂] in a 1 : 0.5 molar ratio under H₂ atmosphere affording the previously reported [NEt₄][Ru₃Ir(µ-H)₂(µ-CO)₃(CO)₉] (2). Performing the reaction under N₂ atmosphere with a 1 : 1 molar ratio of the reagents results in the new species [NEt₄][Ru_3–xIr_2+x(μ-H)_1–x(µ_3-CO)(µ-CO)₃(CO)₈(cod)] (x = 0.11) (3), whereas [Ru_3−xIr_2+x(µ-H)_2–x(µ-CO)₄(CO)₆(cod)₂] (x = 0.5 and 0.77) (4) is obtained by further increasing the amount of [{Ir(µ-Cl)(cod)}₂]. In particular, compound 4 with x = 0.5 has been obtained with a 1:1.25 molar ratio of the reagents, whereas 4 with x = 0.77 is formed increasing the stoichiometry to 1:1.5. Reaction of 1 and [{Ir(µ-Cl)(cod)}₂] under CO atmosphere affords [NEt₄]₂[Ru₄Ir₂(µ-CO)₅(CO)₁₂] (5) (molar ratio of the reagents 1:0.7). Syntheses of 2-5 are very sensitive to the experimental conditions, and optimized procedures in order to obtain each of these compounds in good yield and high purity have been identified. Slight variations of the experimental conditions lead to lower yield and traces of side-products are formed, among which [NEt₄][Ru₃Ir(µ-H)₂(µ-CO)₃(CO)₇(cod)] (6), [NEt₄][Ru₃Ir(µ-H)(µ-Cl)(µ-CO)₃(CO)₉] (7), [NEt₄]₃[Ru₂Ir₂(µ₃-H)(µ-CO)₃(CO)₉]Cl₂ (8) and [NEt₄]₂[Ru₄(µ₄-O)(µ-Cl)₄(µ-CO)₂(CO)₈] (9) have been identified by single-crystal X-ray diffraction (SC-XRD). All the main products 2-5 have been structurally characterized by SC-XRD and further investigated by IR and ¹H NMR spectroscopy in solution. Hydride locations have been elucidated by computational methods.

Graphical Abstract

Homoleptic and heteroleptic heterometallic Ru-Ir hydride carbonyl clusters have been obtained from [NEt4][Ru3(µ-H)(µ-CO)(CO)10] and [Ir(COD)Cl]2 under different experimental conditions.