Synthesis, characterization and reactivity studies of electrophilic ruthenium(II) complexes: a study of H2 activation and labilization

摘要

Reaction of 2,2'-bipyridine (bpy) with dinuclear complexes RuCl(dfppe)(μ-Cl)_3Ru(dmso-S)_3 (dfppe = 1,2-bis(dipentafluorophenyl phosphino)ethane (C_6F_5)_2PCH_2CH_2P(C_6F_5)_2; dmso = dimethyl sulfoxide) (1) or RuCl(dfppe)(μ-Cl)_3RuCl(dfppe) (2) affords the mononuclear species trans-RuCl_2(bpy)(dfppe) (3). Using this precursor complex (3), a series of new cationic Ru(II) electrophilic complexes RuCl(L)(bpy)(dfppe)Z (L = P(OMe)_3 (5), PMe_3 (6), CH_3CN (7), CO (8), H_2O (9); Z = OTf (5, 6, 7, 8), BAr_4~F (9) have been synthesized via abstraction of chloride by AgOTf or NaBAr_4~F in the presence of L. Complexes 5 and 6 were converted into the corresponding isomeric hydride derivatives RuH(PMe_3)(bpy)(dfppe)OTf (10a, 10b) and RuH(P-(OMe)_3)(bpy)(dfppe)OTf (11a, 11b) respectively, when treated with NaBH_4. Protonation of the cationic monohydride complex (11a) with HOTf at low temperatures resulted in H_2 evolution accompanied by the formation of either solvent or triflate bound six coordinated species Ru(S)(P(OMe)_3)(bpy)(dfppe)OTf_n (S = solvent (n = 2), triflate (n = 1) (13a/13b); these species have not been isolated and could not be established with certainty. They (13a/13b) were not isolated, instead the six-coordinated isomeric aqua complexes cis-Ru(bpy)(dfppe)(OH_2)(P(OMe)_3)OTf_2 (14a/14b) were isolated. Reaction of the aqua complexes (14a/14b) with 1 atm of H_2 at room temperature in acetone-d_6 solvent resulted in heterolytic cleavage of the H-H bond. Results of the studies on H_2 lability and heterolytic activation using these complexes are discussed. The complexes 3, 5, 11a, and 14a have been structurally characterized.