A route to new methylpalladium(II) carbene complexes

Synthesis of N-heterocyclic carbene palladium(ii) bis-phosphine complexes and their decomposition in the presence of aryl halides

“…The 31 P{ 1 H} chemical shift of 3b has been previously reported as d 58.3 and 45.7 ppm. 16 A brief survey of the literature indicates that palladium(II) complexes of dppp typically resonate between 25 and −10 ppm in the 31 P{ 1 H} NMR spectrum. 17, 18 This, coupled with the similar shifts for complexes 3a-d, suggests that the previously reported chemical shift of 3b is incorrectly reported.…”

“…The compound [Pd(dmiy)Me(dppp)]BF 4 (dmiy = 1,3-dimethylimidazol-2-ylidene; dppp = 1,3-bis(diphenylphosphino)propane) is stable at room temperature in solution for prolonged periods, 16 and is significantly more stable than analogous compounds containing monodentate phosphines which commonly decompose within several hours at room temperature. 4 It would seem reasonable to assume that the reductive elimination of 2-methylimidazolium salts from compounds of the type [Pd(carbene)Me(P-P)]BF 4 (P-P = chelating phosphine) would yield the reactive fragment Pd(P-P) which could be trapped by further reaction with, for example, an aryl halide to yield a Pd(Ar)X(P-P) compound.…”

Rhodium(I) complexes containing a bulky pyridinyl N-heterocyclic carbene ligand: Preparation and reactivity

“…13 C{ 1 H} NMR (100 MHz) d 159. 6,152.0,140.8,137.7,137.5,137.3,136.7,135.0,133.9,130.3,129.4,127.9,124.5,123.6,122.2,121.4,53.8,21.0,20.1,17.3. Anal.…”

“…Since the stable diaminocarbene was first isolated by Arduengo [1], the chemistry involving this type of carbenes has been attracted considerable attention [2][3][4][5][6][7][8][9][10][11][12][13]. These carbenes are considered as an important class of ligands with strong basicity and good r-donating properties.…”

The influence of N-substitution on the reductive elimination behaviour of hydrocarbyl–palladium–carbene complexes—a DFT study

“…The steric and electronic effects of nitrogen substituents on the stability and catalytic activity of complexes bearing N-heterocyclic carbene ligands are less well known. Certainly both the bulk and donor capacity of the NHC ligand play a role in catalysis, This decomposition mode was an unfortunate side-effect of incorporating a palladium-hydrocarbyl bond into the precatalyst in an attempt to rapidly generate the active palladium(0) catalyst, 16,18, 21 and has since been recognised as an Achilles' heel for these types of catalytic systems. 22, 23 A theoretical analysis of this decomposition using DFT revealed that the reaction proceeded in a reductive-elimination type fashion via a threecentred intermediate (Fig.…”