Molybdenum Complexes Supported by Mixed NHC/Phosphine Ligands: Activation of N₂ and Reaction With P(OMe)₃ to the First Meta‐Phosphite Complex

Abstract

Molybdenum(0) dinitrogen complexes, supported by the mixed NHC/phosphine pincer ligand PCP, exhibit an extreme activation of the N2 ligand due to a very π-electron-rich metal center. The low thermal stability of these compounds can be increased using phosphites instead of phosphines as coligands. Through an amalgam reduction of [MoCl3(PCP)] in the presence of trimethyl phosphite and N2 the highly activated and room-temperature stable dinitrogen complex [Mo(N2)(PCP)(P(OMe)3)2] is obtained. As a second product, the first transition metal complex containing the meta-phosphite ligand P(O)(OMe) originates from this reaction.

Remarkable catalytic activity of dinitrogen-bridged dimolybdenum complexes bearing NHC-based PCP-pincer ligands toward nitrogen fixation

“…One is the complex bearing methylene linkers between the NHC skeleton and the phosphorus atom, where a similar PCP-pincer ligand bearing two phenyl groups on each phosphorus atom has quite recently been reported by Rieger and co-workers49. The other is the complex bearing ethylene linkers, where similar PCP-pincer ligands bearing two phenyl groups on each phosphorus atom have already been reported by some research groups505152535455.…”

Recent progress on NHC-stabilized early transition metal (group 3–7) complexes: Synthesis and applications

“…1). 110 The low p-accepting character of the NHC ligand may enhance dinitrogen activation when compared to phosphine-based ligands. (R = Me, Et) in moderate to good yields (Scheme 37, eq.…”

Recent Progress with Pincer Transition Metal Catalysts for Sustainability

“…Back in 1965, the first dinitrogen complex was synthetized by Allen and Senoff [668]; since this report, many studies have focused on the synthesis of novel transition metal dinitrogen complexes and their reactivity with dinitrogen with the purpose of finding alternative approaches for a greener nitrogen fixation process. Several homogeneous systems have been explored for this transformation [669][670][671][672][673][674][675][676][677][678], inspired by the biological nitrogen fixation performed by the active Fe/Mo site of nitrogenase [679,680]. In addition, various works have covered the photochemical activation of molecular nitrogen [681][682][683][684][685][686][687][688].…”