Towards clustered carbonyl cations [M 3 (CO) 14 ] 2+ (M = Ru, Os): the need for innocent deelectronation.

To access the hitherto almost unknown class of clustered transition metal carbonyl cations, the trimetal dodecacarbonyls M ₃ (CO) ₁₂ (M = Ru, Os) were reacted with the oxidant Ag ⁺ [WCA] ^- , but yielded the silver complexes [Ag{M ₃ (CO) ₁₂ } ₂ ] ⁺ [WCA] ^- (WCA = [Al(OR ^F ) ₄ ] ^- , [F{Al(OR ^F ) ₃ } ₂ ] ^- ; R ^F = -OC(CF ₃ ) ₃ ). Addition of further diiodine I ₂ to increase the redox potential led for M = Ru non-specifically to divalent mixed iodo-Ru ^II -carbonyl cations. With [NO] ⁺ , even the N-O bond was cleaved and led to the butterfly carbonyl complex cation [Ru ₄ N(CO) ₁₃ ] ⁺ in low yield. Obviously, ionization of M ₃ (CO) ₁₂ with retention of its pseudo-binary composition including only M and CO is difficult and the inorganic reagents did react non-innocently. Yet, the radical cation of the commercially available perhalogenated anthracene derivative 9,10-dichlorooctafluoroanthracene (anthracene ^Hal ) is a straightforward accessible innocent deelectronator with a half-wave potential E _1/2 of 1.42 V vs. Fc ^0/+ . It deelectronates M ₃ (CO) ₁₂ under a CO atmosphere and leads to the structurally characterized cluster salts [M ₃ (CO) ₁₄ ] ²⁺ ([WCA] ^- ) ₂ including a linear M ₃ chain. The structural characterization as well as vibrational and NMR spectroscopies indicate the presence of three electronically independent sets of carbonyl ligands, which almost mimic M(CO) ₅ , free CO and even [M(CO) ₆ ] ²⁺ in one and the same cation.
Competing Interests: The authors declare no conflict of interest.
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