Preparation, Characterization, and Reactivity of Dinitrogen Molybdenum Complexes with Bis(diphenylphosphino)amine Derivative Ligands that Form a Unique 4-Membered P–N–P Chelate Ring

Abstract

Five dinitrogen-molybdenum complexes bearing bis(diphenylphosphino)amine derivative ligands (L(R)) that form a unique 4-membered P-N-P chelate ring, trans-[Mo(N(2))(2)(L(R))(2)] (2(R): R = Ph, Xy, p-MeOPh, 3,5-iPr(2)Ph, iPr), were prepared for the purpose of binding a dinitrogen molecule. The corresponding two dichloride-molybdenum complexes, trans-[MoCl(2)(L(R))(2)] (1(R): R = Ph, Xy), were also prepared as comparisons. FT-IR spectra of 2(R) were measured and compared the ν(N≡N) values. Moreover, X-ray crystal structure determination of 1(R) (R = Ph, Xy) and 2(R) (R = Xy, 3,5-iPr(2)Ph) is performed. These experimental results indicated that the coordinated dinitrogen molecule gets easily influenced by the N-substitutent of diphosphinoamine ligand. In addition, to investigate the effect of the properties of the diphosphinoamine ligand for the dinitrogen molybdenum complexes, we performed DFT calculations that focused on the difference of N-substituent, the dihedral angle between P-N-P plane and N-substituent aryl group, and the P-N-P bite angle. This calculation revealed that the competition between the back-donation from metal to dinitrogen and that from metal to ligand was affected by P-N-P bite angle and the dihedral angle of N-substituent of ligand. In order to examine the reactivity with respect to conversion of dinitrogen to ammonia, protonation and trimethylsilylation reactions of the coordinated dinitrogens were carried out for 2(R).

Recent Progress in Transition-Metal-Catalyzed Reduction of Molecular Dinitrogen under Ambient Reaction Conditions

“…However, unfortunately, we have not yet found any evidence to support our proposal shown in Scheme 22. Recently, Masuda and co-workers have reported the preparation and characterization of several molybdenum− dinitrogen complexes bearing bis(diphenylphosphino)amines as ligands (41) and investigated their catalytic activity toward the formation of N(SiMe 3 ) 3 under ambient reaction conditions (Scheme 21). 43 Here, only a low catalytic activity (4 equiv based on the catalyst) has been found in the use of some molybdenum−dinitrogen complexes as a catalyst. More recently, Meźailles and co-workers have reported the reduction of molecular dinitrogen into N(SiMe 3 ) 3 by using molybdenum complexes bearing a bulky tetradentate phosphine as a ligand (42) under ambient reaction conditions (Scheme 21).…”

“…Iron System. As another approach, we have found that Fe(CO) 5 (43) promoted the catalytic conversion of molecular dinitrogen into N(SiMe 3 ) 3 . Thus, with the reaction of Na and Me 3 SiCl with atmospheric molecular dinitrogen in the presence of 43 in THF at room temperature for 20 h, 25 equiv of N(SiMe 3 ) 3 were formed based on the catalyst (Scheme 23).…”

Cobalt‐Catalyzed Transformation of Molecular Dinitrogen into Silylamine under Ambient Reaction Conditions

“…Quite recently, other MoÀN 2 or FeÀN 2 complexes were found to promote the transformation of N 2 into 1. [7,[12][13][14] Almost all of the aforementioned catalytic systemsf or the formation of NH 3 and 1 depend on the use of either Mo or Fe complexes as catalysts. Furthermore, Shilov and co-workers previously reported the catalytic reduction of N 2 into NH 2 NH 2 by using ap olynuclearM oc omplex as ac atalyst.…”

Catalytic Dinitrogen Fixation to Form Ammonia at Ambient Reaction Conditions Using Transition Metal-Dinitrogen Complexes

“…Masuda and coworkers have also prepared several molybdenum‐dinitrogen complexes bearing bis(diphenylphosphino)amine derivative ligands, and have investigated their catalytic activity towards the formation of silylamine under ambient conditions, where 4 equiv. of N(SiMe 3 ) 3 were produced, based on the Mo atom, when trans ‐[Mo(N 2 ) 2 ( L Ph ) 2 ] ( L Ph = N , N ‐bis(diphenylphosphino)aniline) was used as a catalyst (Scheme ) 117…”