The unexpectedly facile insertion of Rh or Ir into a B-Ph bond (reversible for Rh) converts a borane/bis(phosphine) precursor into a boryl/bis(phosphine) PBP pincer ligand. Interconversions between the boryl/borane/borate central functionality are demonstrated in reactions with dihydrogen.

The synthesis of the novel S,CNHC type half‐pincer ligand precursors (L1 and L2) is described herein by using the atom economy reactions of 1‐(2‐(phenylthio)ethyl)‐1H‐imidazole with benzyl bromide and bromodiphenylmethane, respectively. The analogous reaction of 1‐(2‐(phenylselanyl)ethyl)‐1H‐imidazole with 2‐bromoethyl phenyl sulfide has also resulted in a imidazolium bromide (L3) which is a precursor of novel S,CNHC,Se type pincer ligand. The route of silver‐NHC transmetalation was employed to get the palladium complexes [Pd(L1/L2–HBr)Cl2] (C1 and C2) and [Pd(L3–HBr)Cl]BF4 (C3). The imidazolium bromide (L1–L3) and palladium complexes (C1–C3) were characterized by using multinuclear NMR and HR‐MS. The structure and bonding in the complexes C1 and C2 were validated by X‐ray crystallography. Thermally robust and moisture/air insensitive palladium complexes C1–C3 have been explored in the catalysis of C–H bond arylation of imidazoles. The protocol operates under mild reaction conditions in air with an excellent regioselective C–H bond arylation at C‐5 position in imidazoles. All the complexes were found to be efficient (yield up to 97 % in 12 h) in the catalysis; however, the activating pincer ligand framework containing Pd catalyst C3, was found to be utmost effective among the three catalysts. Only 0.5 mol‐% catalyst loading is required to achieve admirable yield of the desired cross‐coupled products. A wide range of substrates was examined, and the developed protocol was applicable to all derivatives with high functional group tolerance and greater efficiency. More importantly, the catalyst C3 has also been found recyclable up to five cycles with minor decrease in efficiency which is highly desirable feature for the development of economical and sustainable industrial reaction processes. The PPh3 and Hg poisoning tests have established the complete homogeneous nature of the catalysis.

Five new safe, solid, and soluble H2O2 adducts of triarylphosphine oxides, including the displayed (p-Tol3PO·H2O2)2, have been synthesized and characterized.