Unsymmetrical Tren-Based Ligands:  Synthesis and Reactivity of Rhenium Complexes

Abstract

Reaction of bis(2-aminoethyl)(3-aminopropyl)amine with C(6)F(6) and K(2)CO(3) in DMSO yields unsymmetrical [(C(6)F(5))HNCH(2)CH(2)](2)NCH(2)CH(2)CH(2)NH(C(6)F(5)) ([N(3)N]H(3)). The tetraamine acts as a tridentate ligand in complexes of the type H[N(3)N]Re(O)X (X = Cl 1, Br 2) prepared by reacting Re(O)X(3)(PPh(3))(2) with [N(3)N]H(3) and an excess of NEt(3) in THF. Addition of 1 equiv of TaCH(CMe(2)Ph)Br(3)(THF)(2) to 1 gives the dimeric compound H[N(3)N]ClReOReBrCl[N(3)N]H (3) in quantitative yield that contains a Re(V)[double bond]O[bond]Re(IV) core with uncoordinated aminopropyl groups in each ligand. Addition of 2 equiv of TaCH(CMe(2)Ph)Cl(3)(THF)(2) to 1 leads to the chloro complex [N(3)N]ReCl (4) with all three amido groups coordinated to the metal, whereas by addition of 2 equiv of TaCH(CMe(2)Ph)Br(3)(THF)(2) to 2 the dibromo species H[N(3)N]ReBr(2) (5) with one uncoordinated amino group is isolated. Reduction of 4 under an atmosphere of dinitrogen with sodium amalgam gives the dinitrogen complex [N(3)N]Re(N(2)) (6). Single-crystal X-ray structure determinations have been carried out on complexes 1, 3, 5, and 6.

Activation of Molecular Nitrogen: Coordination, Cleavage and Functionalization of N2 Mediated By Metal Complexes

“…[26] The dinitrogen unit is only weakly activated; the N À N bond length of 1.087(4) ä corresponds to a triple bond, virtually identical to that of free N 2 (1.0976 ä).…”

One-pot synthesis of tripodal tris(2-aminoethyl)amine derivatives from seven molecular components

“…6,10,12,13 They have also been used to stabilise redox active oxoanions, such as thiosulfate, 14 and to prepare cyano-bridged heteropolynuclear clusters with ferromagnetic properties. 15,16 Less well explored are aryl-substituted tren ligand structures, although some have been employed in the formation of transition metal amido complexes, [17][18][19][20][21][22][23] which have been demonstrated to act as catalysts in dinitrogen reduction (Mo, V and Cr complexes) 20,21 and which have been tested in alkene epoxidation reactions (Fe and Mn complexes). 17 Aryl-substituted tren-based ligands are generally synthesised via aryl substitution reactions using commercially available ArF compounds in 28-99% yields.…”

“…17 Aryl-substituted tren-based ligands are generally synthesised via aryl substitution reactions using commercially available ArF compounds in 28-99% yields. 18,24 A different pathway to these aryl-substituted tren compounds involves Pd-mediated aromatic coupling, which is limited to commercially available ArBr compounds, affording the products in 27-90% yields. 19,25 More extended tren structures have been prepared via a two-step synthesis of the starting ArBr compound followed by Pd-mediated aromatic coupling in lower but acceptable overall yields of 36-45%.…”

Reactions of HMPA with hexafluorobenzene, pentafluorochlorobenzene and pentafluorophenol

“…Indeed, many nucleophilic substitution reactions of hexafluorobenzene can be safely performed in these solvents [1,2]. Hexafluorobenzene, as a solvent, is very soluble, and could favor the intramolecular cyclization of dialkynyl imidazoles and products separation in much higher yields [3].…”

“…In some conditions, however, the cleavage of C-F bond of hexafluorobenzene and its derivatives is known to occur in the presence of nucleophiles. The nucleophilic replacement of the C-F bond always need wild conditions like high temperature, strong base or violent nucleophiles [1,[4][5][6][7][8]. The use of HMPA to effect N,Ndimethylamination of aromatic substrates has captured wide interest previously, for example, the reaction of HMPA with halogenated aromatics containing electron-withdrawing groups [9][10][11].…”