Facile Insertion of CO₂ into the Ru−H Bonds of Ru(dmpe)₂H₂ (dmpe = Me₂PCH₂CH₂PMe₂):  Identification of Three Ruthenium Formate Complexes

The reaction of cis-Ru(dmpe)2H2 (dmpe = Me2PCH2CH2PMe2), 1, with carbon dioxide has been investigated. Addition of CO2 at 293 K results in the formation of two formate complexes: the major product is the trans formate hydride, trans-Ru(dmpe)2(OCHO)H, 2, while the minor species is the bis(formate) complex, cis-Ru(dmpe)2(OCHO)2, 3. When the addition of carbon dioxide is performed at 195 K, both the bis(formate) and the cis-formate hydride complex, cis-Ru(dmpe)2(OCHO)H, 4, are observed in larger concentrations. All three complexes have been characterized by multinuclear NMR while 2 has been isolated and characterized by X-ray crystallography. The ruthenium formate group is planar with Ru−O(1) = 2.243(4) Å. The Ru−O(1) vector is tilted away from the normal to the P4 plane with resultant O(1)−Ru−P angles of 84.4(2), 88.4(1), 96.7(1), and 101.5(2)°. The C−O(2) vector of the formate group points toward the RuP4 plane. The symmetric and antisymmetric OCO stretching modes in the IR spectrum of 2 were identified by reaction with 13CO2.