The unsaturated complexes Ru(CO)Cl(CRCHR′)(PPh3)2 react rapidly with the sodium salt of the anion 3,3-dimethylacrylate. The family of complexes obtained contains the 3,3-dimethylacrylate ligand η2-coordinated through the carboxylate group. The structure of the complex Ru(O2CCHCMe2)(CO)(C(CO2Me)CH(CO2Me))(PPh3)2 was determined by X-ray diffraction. The complex is triclinic, space group P1, with dimensions of the unit cell of a = 17.401(1), b = 12.633(3), c = 12.054(1) Å; α = 119.092(4), β = 72.423(5), γ = 109(7)° and Dcalc = 1.226 g cm-3 for Z = 2. The molecule consists of a ruthenium hexacoordinated with two triphenylphosphines in the apical positions and the rest of the ligands in the equatorial plane of a distorted octahedron. © 1990.