Toward a general method for CCC N-heterocyclic carbene pincer synthesis: Metallation and transmetallation strategies for concurrent activation of three C–H bonds

Synthesis and characterization of a free phenylene bis(N-heterocyclic carbene) and its di-Rh complex: Catalytic activity of the di-Rh and CCC–NHC Rh pincer complexes in intermolecular hydrosilylation of alkynes

“…The phosphines in pincer ligands have been replaced by NHCÕs to produce pincer architectures incorporating the carbene as the r-donor. We were the first to report the CCC-NHC pincer architecture illustrated in Scheme 2, where the NHC architecture with a M-C bond at the central position has been directly mapped atom for atom onto the PCP pincer architecture [9]. Several different types of NHC pincer complexes have been reported and been extensively studied.…”

Synthesis and complexes of imidazolinylidene-based CCC pincer ligands

“…13 Similar to that employed for the pro-ligand associated with D, 10 we chose a synthetic route involving amide coupling reactions between 1,3-diaminobenzene and aminooxoacetic acids 2 (R = Mes, a; Dipp, b; i Pr, c;…”

“…Thermal ellipsoids drawn at the 50% probability level; solvent molecules omitted for clarity. Selected bond lengths (Å) and angles (º): Cu1···Cu11, 3.789(2); Cu1-Cl1, 2.116(3), Cu1···Cl11, 3.483(4); Cu1-C17, 1.908(8); Cu11···Cl1, 3.635(4); Cu11-Cl11, 2.103(3); Cu11-C117, 1.895 (7); Cu2···Cu12, 2.8715(16); Cu2-Cl2, 2.274(3); Cu2-Cl12, 2.331(3); Cu2-C22, 1.891 (8); Cu12-Cl2, 2.339(3); Cu12-Cl12, 2.270(3); Cu12-C122, 1.903(8); Cnt(C10)···Cnt(C110), 5.140(12); C17-Cu1-Cl1, 168.7(3); C17-Cu1···Cl11, 89.1(3); C117-Cu11···Cl1, 90.8(3); C117-Cu11-Cl11, 171.4(3); C22-Cu2-Cl2, 136.6(3); C22-Cu2-Cl12, 125.6(3); C122-Cu12-Cl2, 125.5(3); C122-Cu12-Cl12, 136.8(3); Cu1-Cl1···Cu11, 77.48(11); Cu1···Cl11-Cu11, 81.39(10); Cu2-Cl2-Cu12, 76.98(9); Cu2-Cl12-Cu12, 77.21 (10).…”

“…4 Such an observation is rather surprising given the successful application of mono-dentate imidazolinylidene ligands in catalysis; epitomised by their wide-spread use in olefin metathesis reactions, where they significantly out perform their unsaturated counterparts. 9 Indeed, in late 2015 when we compiled our review the only known imidazolinylidene-based example to our knowledge was zirconium adduct D. 10 In the intervening time, Chirik and co-workers have prepared iron-based E and demonstrated its ability to selectivity catalyse trituration reactions of C(sp 2 )-H bonds with high efficiently, highlighting the potential versatility of such NHC-pincers. 11 As part of our work developing the organometallic chemistry of NHC-based pincer ligands, which has involved investigation of macrocyclic variants, backbone geometry, atropisomerism and transmetallation methodology, 12 in this report we describe the preparation and preliminary coordination chemistry of imidazolinylidene-based CCC pincer ligands 1 (Chart 2).…”

The Role of NHC Ligands in Oxidation Catalysis

“…Although other reagents have been proposed [68], the use of Ag 2 O as introduced by Lin [69,70] is currently the most important pathway for the synthesis of NHC metal complexes. The imidazolium halide forms a silverhalide-NHC complex which then transfers the carbene ligand to the metal precursor.…”