Influence of Jack Thrust on H&V Shield Behavior

Anion influences on reactivity and NMR spectroscopic features of NHC precursors

“…IR spectroscopy cannot reveal smaller differences between halides and pseudohalides due to its insufficient resolution. 29 However, one piece of information that can be extracted from the data is that halide salts have notably smaller wavenumbers than their BF 4 À or PF 6 À counterparts, which is within expectations. Notably, the IR data for the BPh 4 À salt appears to be in line with its 13 C NMR data.…”

“…30 However, it was noted that conclusions made did not consider neither anion nor solvent inuences on the 1 J C-H values. 29 In order to address this issue, we decided compare the 1 J C2-H of the four salts A-D in the aforementioned solvents. The data summarized in Table 4 indicate that anion or solvent inuences on the 1 J C2-H are surprisingly small or even negligible.…”

Design and synthesis of cyclometallated sulphur-n-heterocyclic carbene complexes and their application in catalysis

“…We constantly observed low yields for the neutral S-NHC palladium complexes (±)-67(a-c) and the reason behind this was the formation of dimeric complexes which are consistent with dynamic/hemiliable studies reported by Huynh et al 62 The existence of the dimeric complex ( Figure 2.1) was confirmed by its molecular ion peak in LCMS and additional proton peaks in 1 H-NMR spectrum along with its monomeric unit. However, we failed to obtain the pure…”

“…13 However, 13 C NMR spectra are generally well accepted as it is more accurate and it also reduces the manipulation involved in the coordination of CO trans to the NHC system. The Figure 1.1 shows the donor ability of NHC in 13 C NMR, 14 where it describes that the saturated NHCs are strong donors compared to the corresponding unsaturated ones which in turn is in agreement with the calculated relative basicity of corresponding NHCs reported by Magill et al 15 Nolan proposed a model to define the steric properties of NHC ligands that are measured in terms of buried volume %V Bur, 16 as shown in Figure 1.2, which is "the amount of volume of a sphere centered on the metal, buried by overlap with atoms of various NHC ligands". The volume is the space around the metal occupied by the ligand fragment and therefore, the %V Bur increases as the functionality of the N-substituent is bulkier.…”

“…Hahn et al, 60 reported pyridine functionalized benzimidazolium tridentate palladium complex, and portrayed that complex 28 showed high catalytic activity towards Heck reaction. After exploring these studies on thioether tethered NHCs recently, Huynh et al extended their research towards thiophene 62 functionalized palladium(II) bis carbene complexes which were closely similar to their thioether system. The following discussion will spotlight only on organometallic palladacycles with sulphur as two electron donor atom.…”