Reactions of ruthenium vinylidene and acetylide complexes containing trichloromethyl groups: preparation of a cyclobutenonyl complex by solid-state photolysis.

Solid-state route to a cyclobutenone: Ruthenium perchlorocyclobutenonyl complex 2 is obtained by solid-state photoisomerization of ruthenium trichloroacetyl acetylide complex 1. The four-membered ring is sufficiently robust that transfer of the intact ligand could be readily achieved in a reaction of 2 with an enyne. Cyclobutenedionyl complex 3 was obtained by hydrolysis of 2 in H(2)O/THF.New reactions were observed for the cationic gamma-hydroxyvinylidene complex [Ru(2)]==C==CHC(OH)(CCl(3))(2) (+) (2, [Ru(2)]=CpRu(PPh(3))(2)). A rare chloroform elimination was observed when 2 was treated with nBu(4)NOH to give neutral acetylide complex [Ru(2)]--C[triple chemical bond]CC(==O)CCl(3) (3). Solid-state photoinduced isomerization of 3 generated ruthenium perchlorocyclobutenonyl complex [Ru(2)]--C(4)Cl(3)O (4) in high yield. This transformation was analyzed by DFT calculations, and 4 was found to be 4.22 kcal mol(-1) more stable in terms of Gibbs free energy than 3. In the coupling reaction of 4 with 2-methyl-1-buten-3-yne the four-membered cyclic ligand is transferred to the enyne to give substituted eta(3)-butadienyl complex 5 containing a cyclobutenonyl group. This coupling product could be removed from the metal by HCl. Deprotonation of 2 gave gamma-hydroxyacetylide complex [Ru(2)]--C[triple chemical bond]CC(OH)(CCl(3))(2) (9). In the photolysis of 9 phosphine dissociation is followed by addition of HCl to give neutral vinylidene complex Cl[Ru(1)]==C==CHC(OH)(CCl(3))(2) (10, [Ru(1)]=Cp(PPh(3))Ru). Complex 4 catalyzed the coupling reaction of dimethyl acetylenedicarboxylate with styrene yielding the diene PhCH==CHC(CO(2)Me)==CHCO(2)Me. Solid-state structures of 3-6 and 10 were determined by single-crystal X-ray diffraction analysis.