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

Abstract

The reaction of cis -Ru(dmpe) 2 H 2 (dmpe = Me 2 PCH 2 CH 2 PMe 2 ), 1, with carbon dioxide has been investigated. Addition of CO 2 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 P 4 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 RuP 4 plane. The symmetric and antisymmetric OCO stretching modes in the IR spectrum of 2 were identified by reaction with 13 CO 2 .