UNUSUAL ORTHOMETALLATION OF A TETRAPHENYLCYCLOPENTADIENONE LIGAND

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 P2(1)/c, a = 12.130(8), b = 20.972(9), c = 20.861 (12) angstrom, beta = 98.80(5)-degrees and Z = 4], which reveals that the structure contains a diruthenium pentacarbonyl unit [Ru(1)-Ru(2) 2.810(2) angstrom], 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 sigma bond to Ru(1) [2.138(8) angstrom]. The same phenyl group is bonded in an eta-6 manner to a third ruthenium atom, which in turn is ligated by the second tetracyclone (again bound as a planar eta-5 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) angstrom].