The complex H2Ru(PPh3)4 reacts with Me acrylate to give bis(methylacrylate)bis(triphenylphosphine)ruthenium(0). Temp.-dependent NMR spectra show that the complex exists in two isomeric forms in soln. The major form, I (ca. 74%), has one Me acrylate ligand h2-coordinated and the other h4-coordinated as a 1-oxabutadiene ligand. This complex reacts with water to give the monoaqua adduct, the crystal structure of which is reported. The minor form, II (ca. 18% in equil. mixt.), is proposed to have a tetrahedral structure with two equiv. h2-bonded Me acrylate ligands.