Syntheses of reactive mixed-metal carbide clusters and their interaction with proton sources

Article abstract of DOI:10.1021/om00120a026

The three-iron ketenylidene [Fe₃(CO)₉(CCO)]^2-, I, undergoes a redox condensation reaction with [Rh-(CO)₂Cl]₂ to produce a reactive butterfly carbide [RhFe₃(CO)₁₂C]^-, VIII. Similarly, I in the prescence of [Mn(CO)₅(CH³CN)]⁺ leads to [MnFe₃(CO)₁₃C]^-, IX. Both products were characterized by ¹³C NMR spectroscopy, and the structure of the rhodium cluster VIII was determined by single-crystal X-ray diffraction. Monoprotonation of VIII and IX yields the butterfly methylidynes RhFe₃(CO)₁₂(CH), XII, and MnFe₃-(CO)₁₃(CH), XIII. This site of protonation contrasts with the butterfly carbide [Fe₄(CO)₁₂C]^2-, II, which first protonates on the metal framework. In some cases the redox condensation reaction does not terminate at the four-metal butterfly cluster stage, thus the reaction of I with [CpNi(CO)]₂ yields [Ni₃Fe₃(CO)₁₃C]^2-, X. Attempts to generate a butterfly carbide via a metal substitution pathway employing II and Co₂(CO)₈ did not lead to a tetranuclear cluster but produced instead the pentanuclear carbide [CoFe₄(CO)₁₄C]^-, XI, the structure of which was also determined by single-crystal X-ray diffraction. X-ray crystal data for [PPN][RhFe₃(CO)₁₂C]·CH₂Cl₂, VIII: orthorhombic, a = 17.780 (2) A?, b = 19.641 (4) A?, c = 15.145 (4) A?, Z = 4, space group Pna2₁. For [PPN][CoFe₄(CO)₁₄C], XI: monoclinic, a = 17.403 (3) A?, b = 16.030 (3) A?, c = 19.055 (2) A?, β= 105.34 (1)°, Z = 4, space group P2₁/n.