Palladium–Carbon σ-Bonded Complexes

Bidentate Chelate Complexes of Palladium(II) with the Carbanion 2-C6F4PPh2and Their Transformation into Complexes Containing Bridging 2-C6F4PPh2

“…Since the discovery of the ortho -palladation of azobenzene and N,N -dimethylaniline in the 1960s, , cyclopalladated complexes, especially those containing N-, O-, and S-donor groups, have attracted continuous interest because of their diverse applications, particularly in organic synthesis, and because of the relevance of cyclopalladation to the transition metal promoted C–H activation of hydrocarbons. − Cyclopalladation of P-donor groups by C–H activation ,,− is generally observed only with very bulky or sterically constrained tertiary phosphines or with phosphites; ortho -palladated complexes of triphenylphosphine cannot be obtained by this route. Attempts to make them from Pd(0) or Pd(II) precursors by transmetalation from [Hg(2-C 6 H 4 PPh 2 ) 2 ] gave exclusively complexes in which 2-C 6 H 4 PPh 2 bridges Pd and Hg. , However, Lahuerta et al , have shown that 2-BrC 6 H 4 PPh 2 adds oxidatively to the palladium(0)-dibenzylideneacetone complex, [Pd(dba) 2 ], to give a tetranuclear complex [Pd 4 (μ-Br) 4 (μ-2-C 6 H 4 PPh 2 ) 4 ] ( 1 ), in which an approximate rectangle of palladium atoms is bridged on alternate sides either by two bromine atoms or by two 2-C 6 H 4 PPh 2 units arranged head-to-tail.…”

Cyclometalated and Alkoxyphenyl-Substituted Palladium Imidazolin-2-ylidene Complexes. Synthetic, Structural, and Catalytic Studies

“…In view of the success of cyclometalated Pd phosphine and phosphite complexes in various C−C coupling reactions, we compared the activity of 4 and 9d , e in the Heck reaction of aryl bromides and chlorides with n -butyl acrylate under different conditions. Selected data are compiled in Table .…”

“…As a continuation of our work aiming at the development of well-defined NHC complexes suitable for cross-coupling reactions, we initiated a study of Pd complexes with “saturated” NHCs substituted with electron-rich or cyclometalated aromatic rings. Palladium complexes with cyclometalated phosphines and phosphites have shown activity in Suzuki and C−heteroatom bond formation reactions . Surprisingly, there has been a very limited number of spectroscopically characterized cyclometalated Pd(NHC) complexes reported by Hiraki et al…”