The maximum number of carbonyl groups around an Ru6C polyhedral cluster: hexanuclear ruthenium carbonyl carbides

Abstract

Octahedral, trigonal prismatic, and capped square pyramidal structures have been optimized for the Ru(6)C(CO)(n) clusters (15 ≤ n ≤ 20) using density functional theory. The experimentally known very stable Ru(6)C(CO)(17) is predicted to have an octahedral structure in accord with experiment as well as the Wade-Mingos rules. The stability of Ru(6)C(CO)(17) is indicated by its high carbonyl dissociation energy of ~37 kcal mol(-1) and the high energy of ~33 kcal mol(-1) required for disproportionation into Ru(6)C(CO)(18) + Ru(6)C(CO)(16). Theoretical calculations predict a doubly carbonyl bridged octahedral Ru(6)C(CO)(17) structure to be ~0.7 kcal mol(-1) more stable than the experimentally observed singly bridged structure. A trigonal prismatic Ru(6)C(CO)(19) cluster isoelectronic with the known Co(6)C(CO)(15)(2-) dianion does not appear to be viable as indicated by a low carbonyl dissociation energy of 8.8 kcal mol(-1) and a required energy of only 4.9 kcal mol(-1) for disproportionation into Ru(6)C(CO)(20) + Ru(6)C(CO)(18). The predicted instability of Ru(6)C(CO)(n) (n ≥ 18) derivatives suggests a maximum of 17 external carbonyl groups around a stable polyhedral Ru(6)C structure.

Highly Reduced Ruthenium Carbide Carbonyl Clusters: Synthesis, Molecular Structure, Reactivity, Electrochemistry, and Computational Investigation of [Ru6C(CO)15]4–

“…Indeed, protonation of 2 resulted in the monohydride 3 , whereas oxidation of 2 under different experimental conditions allowed the synthesis of 4–8 . Clusters 1 and 4 were previously described, − whereas 2 , 3 , 5 , 6 , 7, and 8 were reported here for the first time. Clusters 1–8 are all based on the same octahedral Ru 6 C core and display 86 CVE.…”

“… 50 − 53 The latter possesses 84 cluster valence electrons (CVE) rather than 86 CVE, as normally found in octahedral carbonyl clusters, including [Ru 6 C(CO) 16 ] 2– and [HRu 6 C(CO) 16 ] − . 54 , 55 As it is shown here, it is likely that [HRu 6 C(CO) 15 ] − might be better reformulated as an electron precise 86 CVE trihydride, that is, [H 3 Ru 6 C(CO) 15 ] − .…”

Unexpected formation of a μ-carbido diruthenium(iv) complex during the metalation of phthalocyanine with Ru3(CO)12 and its catalytic activity in carbene transfer reactions

“…This tentative mechanism might be corroborated by the results of DFT calculations which suggest that among all the possible products of thermolysis of Ru 3 (CO) 12 , Ru 6 C(CO) 17 has the lowest reactivity, while the other complexes Ru 6 C(CO) 23−n should be less stable towards further chemical transformations. 16 Although carbido complexes have been well-known in ruthenium chemistry for a long time, 17 the herein reported µcarbido-dimer 2 is exceptionally rare in the chemistry of ruthenium complexes with tetrapyrrolic ligands. It is limited to the single example of the unsubstituted (PcRu) 2 (µ-C), reported by Homborg et al in 1997.…”