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 γ‐hydroxyvinylidene complex [Ru 2 ]CCHC(OH)(CCl 3 ) 2 + ( 2 , [Ru 2 ]=CpRu(PPh 3 ) 2 ). A rare chloroform elimination was observed when 2 was treated with n Bu 4 NOH to give neutral acetylide complex [Ru 2 ]CCC(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 η 3 ‐butadienyl complex 5 containing a cyclobutenonyl group. This coupling product could be removed from the metal by HCl. Deprotonation of 2 gave γ‐hydroxyacetylide complex [Ru 2 ]CCC(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 ]CCHC(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 PhCHCHC(CO 2 Me)CHCO 2 Me. Solid‐state structures of 3 – 6 and 10 were determined by single‐crystal X‐ray diffraction analysis.