Fulvene Complex Stabilized by Triangular Ruthenium Cluster

The tetranuclear complex H₂Ru₄(CO)₁₁(µ₄-η¹,η⁵-CC₅H₄) (I) was obtained by the photochemical reaction of Ru₃(CO)₁₂ with Z-1-(4-tolyl)-3-phenylaminoprop-2-en-1-one (λ ≥ 210 nm). The structure of complex I was established by single crystal X-ray diffraction. According to X-ray diffraction data, the complex is described by a superposition of resonance structures, that is, the carbene cluster YCRu₃, in which the substituent Y at the carbyne carbon atom is (η⁵-C₅H₄)Ru(CO)₂, and a vinylidene complex containing a fulvene form of the ligand, in which the exocyclic carbenium carbon atom is additionally stabilized by coordination to a triangular ruthenium cluster. For description of the interatomic binding in I, quantum chemical calculations of the electronic structure of the molecule in the gas phase were carried out at the PBE0/def2TZVP level. The features of binding of the organic ligand to the metal core were described in terms of the atoms in molecules theory. According to the calculations, the C₆H₄ moiety in I is a fulvene type ligand in which two hydrogen atoms in the CH₂ group have been replaced by ruthenium atoms.