The first triple-decker complex with a carbenium center, [CpCo(μ-C₃B₂Me₅)RuC₅Me₄CH₂]⁺: Synthesis, reactivity, X-ray structure, and bonding

The first derivative of the methylium cation with the triple-decker substituent, [CpCo(C₃B₂Me₅)RuC₅Me₄CH₂]PF₆ (2PF₆), was synthesized from the reaction of the triple-decker complex CpCo(C₃B₂Me₅)RuCp* (1) with the salt of the trityl cation [CPh₃]⁺. The X-ray crystal structure of 2PF₆ reveals that the methylium carbon is bound to the ruthenium with Ru−C bond length of 2.259 Å and corresponds to the description of its structure as η⁶-fulvene-ruthenium. Reactions of 2PF₆ with nucleophiles OH⁻, Ph₃P, Et₃N led to the corresponding derivatives of 1 in high yields. Aromatic amines PhNEt₂ and 4-MeC₆H₄NH₂ react with 2PF₆ to give the electrophilic aromatic substitution products quantitatively. Chemical reduction of 2PF₆ with Zn powder in tetrahydrofuran leads to the formation of the bis(triple-decker) derivative (CpCo(C₃B₂Me₅)RuC₅Me₄CH₂)₂ (10) with a CH₂CH₂-bridge. The structures of complexes 4, 7–10 were determined by X-ray diffraction. Density functional calculations support the crystallographically determined geometry of 2 and allow rationalization of some characteristics of its structure, spectroscopy, and reactivity.