Rhodium and Palladium Complexes of N-Heterocyclic Olefin (NHO) Ligand Fused with the 9,10-Dihydro-9,10-ethanoanthracene Framework

Abstract

A saturated type of N-heterocyclic olefin (NHO) was synthesized by fusing 2-methyleneimidazolidine with a 9,10dihydro-9,10-ethanoanthracene framework, and rhodium and palladium complexes with this NHO were successfully obtained. The Tolman electronic parameter (TEP) value calculated using the Rh complex indicated that the electron-donating ability of the present saturated NHO was weaker than those of unsaturated NHOs. X-ray diffraction (XRD) studies of three Pd complexes confirmed that these complexes were [(NHO)PdCl(μ-Cl)] 2 , trans-[(NHO) 2 PdCl 2 ], and cis-[(NHO) 2 PdCl 2 ]. trans-[(NHO) 2 PdCl 2 ] isomerized to a cis-complex in an acetonitrile solution. Furthermore, our computational studies indicated that the Nsubstituent is crucial for the planarity of the 2-methyleneimidazolidine moiety of our NHO and its metal complexes.

Towards structurally versatile mesoionic N-heterocyclic olefin ligands and their coordination to palladium, gold, and boron hydride

“…30)) yet similar to that of the imidazole-based-NHO-Pd ( δ = −7.0 − (+0.99) ppm). 14 Increasing the substitution of C exo when going from 7aPd to 7bPd caused a downfield shift of about +11 ppm for the methyl group; in diastereomeric 7bPd , C exo resonated at δ = 10.7 and 10.9 ppm, which is close to the value expected in alkane series (+9 ppm). 45…”

“…1a) and have been identified as a promising new class of electron-rich and carbon-based ligands. [2][3][4][5][6][7][8][9][10] Imidazole-based NHO coordination compounds with Mo, 11 Rh, [12][13][14] Au, 10,13 W, 11,15 Ir, 5,16 Pd, 8,14 and Ti 17 have been reported. Their utility in catalysis is also documented.…”

Synthesis of a N‐heterocyclic Olefin‐Ligated Pd Complex [(NHO)Pd{[2‐(CH3O)C6H4]3P}Cl2] as a Catalyst for Suzuki−Miyaura Coupling

“…We recently reported that our original NHO ligand based on 2‐methyleneimidazolidine, which we refer to as DHASICH 2 , is useful in obtaining stable NHO−Pd complexes [22] . In that study, we decided to apply this motif to a core NHO for the development of a stable NHO−Pd catalyst.…”

“…We recently reported that our original NHO ligand based on 2methyleneimidazolidine, which we refer to as DHASICH 2 , is useful in obtaining stable NHOÀ Pd complexes. [22] In that study, we decided to apply this motif to a core NHO for the development of a stable NHOÀ Pd catalyst. Our motif makes it relatively easy to introduce varied N-substituents, and this allows us to tune the steric environments around the olefin portions.…”

Group 4 Transition Metal Complexes with Anionic N‐Heterocyclic Olefin Ligands

“…Indeed, since the discovery of the first transition metal‐NHO complex by Kaska and coworkers ( A ), [2] NHOs have been used as supporting ligands for transition metal‐mediated catalysis [3] . Examples of NHO‐transition metal complexes include those from the groups of Kuhn ( B ), [4] Ando and Ishizuka ( C ), [5] Rivard ( D ), [3d] and others (Chart 1) [6] . While multiple examples of transition metal complexes supported by neutral NHO donors can be found in the literature, examples of metal complexes bearing deprotonated, anionic N ‐heterocyclic olefins (aNHOs) remain rare [7] .…”