Chiral Bicyclic NHC/Rh Complexes and Their Application to Catalytic Asymmetric Ring-Opening Reaction of Oxabenzonorbornadienes with Amines

Abstract

A rhodium complex bearing a chiral bicyclic NHC ligand, [RhCl(3az)(cod)] 4az, was synthesized and fully characterized by X-ray diffraction analysis, high-resolution mass spectrometry, and multinuclear NMR spectroscopy. The electronic and steric properties of NHC ligand 3az were evaluated by IR measurement and X-ray diffraction analysis of dicarbonyl complex [RhCl(3az)(CO) 2 ] 5az, which was prepared by replacing the COD ligand of 4az with CO. The potential of novel complex 4az as a chiral catalyst was investigated in the Rh-catalyzed asymmetric ringopening reaction of oxabenzonorbornadienes with amines, and the corresponding products were afforded in good yields with good enantioselectivities (up to 81% ee).

Synthesis of Pincer type carbene and their Ag(I)-NHC complexes, and their Antimicrobial activities

“…One lower class of these ligands are protic NHCs that have an acidic proton on one of the nitrogen atoms in the diamine heterocyclic compound [17]. In addition, they are deprotonated compounds containing a basic ring-nitrogen atom [18] (Fig.…”

A S=3/2 Cr(III) Complex In A Square‐Capping NHC Framework

“…This ligand is most closely related to the dianionic NN 4 topology of the B 2 Pz 4 Py ligand, [1,2] as well as to charge neutral frameworks consisting of five nitrogenous donors like N4Py, [3] ImPy 3 N, [4] PY5Me 2 and their derivatives; [5,6] or the charge neutral P 2 Ph PP 2 Ph and P 2 Me PP 2 Ph frameworks consisting of five phosphine donors [7] . While the coordination chemistries of monodentate, [8–10] bidentate, [11–16] tripodal [17–20] and macrocyclic [21–25] NHC ligands are well developed, study of the coordination chemistry of square‐capping NHC frameworks are in their infancy. NHC ligands are an attractive alternative to widely used phosphine ligands as they share strong σ‐donor and moderate π‐accepting ability, are insensitive to oxidizing conditions, [26] and can support a wide variety of oxidation states best exemplified by isolable complexes of iron ranging from +6 to 0 [13,19,27] …”

“…Ph and P 2 Me PP 2 Ph frameworks consisting of five phosphine donors. [7] While the coordination chemistries of monodentate, [8][9][10] bidentate, [11][12][13][14][15][16] tripodal [17][18][19][20] and macrocyclic [21][22][23][24][25] NHC ligands are well developed, study of the coordination chemistry of square-capping NHC frameworks are in their infancy. NHC ligands are an attractive alternative to widely used phosphine ligands as they share strong σ-donor and moderate π-accepting ability, are insensitive to oxidizing conditions, [26] and can support a wide variety of oxidation states best exemplified by isolable complexes of iron ranging from + 6 to 0.…”

A Tetrapodal Penta‐Carbene Ligand and Iron(III) Complex

“…Coordination compounds of the B 2 Pz 4 Py ligand have provided complexes of Fe and Co relevant to nitrogen fixation, [25][26][27] vitamin B12, [28] and dioxygen reduction. [29] Considering the rich chemistry of coordination complexes supported by monodentate, [30][31][32] bidentate, [33][34][35][36][37][38] tripodal [39][40][41][42] and macrocyclic [43][44][45][46][47] ligands consisting of N-heterocyclic carbene (NHC) donors a particularly striking absence in the tetrapodal pentadentate family of ligands are those composed of equatorial and axial NHC donor groups. Intrigued by the impact a pentadentate framework composed entirely of NHC donors would have on the chemistry of first-row transition metals we undertook the preparation of the tricationic protoligand [CC 4H5 Me ](OTf) 3 (3).…”