Unusual orthometallation of a tetraphenylcyclopentadienone ligand

Abstract

Controlled pyrolysis of the reaction between [Ru₃(CO)₁₂] and tetracyclone (tetraphenylcyclopentadienone) in refluxing heptane gives a new complex with the empirical formula [Ru₃(CO)₅(C₄Ph₄CO)₂] in moderate yield. The compound has been characterised by a single-crystal X-ray diffraction study [monoclinic, space group P2₁/c, a= 12.130(8), b= 20.972(9), c= 20.861(12)Å, β= 98.80(5)° and Z= 4], which reveals that the structure contains a diruthenium pentacarbonyl unit [Ru(1)–Ru(2) 2.810(2)Å], bridged by a tetracyclone ligand bonded in the planar ‘hydroxycyclopentadienyl’ mode. One of the phenyl groups of this ligand is cyclometallated in the ortho position, forming a Ru–C σ bond to Ru(1)[2.138(8)Å]. The same phenyl group is bonded in an η⁶ manner to a third ruthenium atom, which in turn is ligated by the second tetracyclone (again bound as a planar η⁵ ligand), forming a sandwich-type fragment. The hydrogen atom released by the metallation of C(30) is intramolecularly hydrogen bonded between the oxygen atoms of the two tetracyclone ligands [O(6)⋯ H ⋯ O(7) 2.590(7)Å].