Toward New Organometallic Architectures: Synthesis of Carbene-Centered Rhodium and Palladium Bisphosphine Complexes. Stability and Reactivity of [PC^BImPRh(L)][PF₆] Pincers

Abstract

In this article, we report the synthesis of a tridentate carbene-centered bisphosphine ligand precursor and its complexes. The developed four-step synthetic strategy of a new PC(BIm)P pincer ligand represents the derivatization of benzimidazole in the first and third positions by (diphenylphosphoryl)methylene synthone, followed by phosphine deprotection and subsequent insertion of a noncoordinating anion. The obtained ligand precursor undergoes complexation, with PdCl2 and [μ-OCH3Rh(COD)]2 smoothly forming the target organometallics [PC(BIm)PPdCl][PF6] and [PC(BIm)PRh(L)][PF6] under mild hydrogenation conditions. A more detailed study of the rhodium complexes [PC(BIm)PRh(L)][PF6] reveals significant thermal stability of the PC(BIm)PRh moiety in the solid state as well as in solution. The chemical behavior of 1,3-bis(diphenylphosphinomethylene)benzimidazol-2-ylrhodium acetonitrile hexafluorophosphate has been screened under decarbonylation, hydrogenation, and hydroboration reaction conditions. Thus, the PC(BIm)PRh(I) complex is a sufficiently stable compound, with the potential to be applied in catalysis.

Remarkable catalytic activity of dinitrogen-bridged dimolybdenum complexes bearing NHC-based PCP-pincer ligands toward nitrogen fixation

“…1a). One is the complex bearing methylene linkers between the NHC skeleton and the phosphorus atom, where a similar PCP-pincer ligand bearing two phenyl groups on each phosphorus atom has quite recently been reported by Rieger and co-workers49. The other is the complex bearing ethylene linkers, where similar PCP-pincer ligands bearing two phenyl groups on each phosphorus atom have already been reported by some research groups505152535455.…”

Iron pyrrole-based PNP pincer ligand complexes as catalyst precursors

“…The structure of a pincer ligand consists of a backbone, such as benzene (van der Boom & Milstein, 2003; or pyridine (Benito-Garagorri & Kirchner, 2008;Gunanathan & Milstein, 2011), and two 'arms' which typically contain a phosphorus (Werkmeister et al, 2014; or nitrogen (Zhang et al, 2006;Bleith et al, 2015) atom. They have found use in organometallic chemistry, as their ability to chelate tends to make the metal complexes thermally robust (Selander & Szabó, 2011;Plikhta et al, 2015). In addition, pincer ligands can help tune the properties of the metal center by tuning their steric and electronic properties (Bichler et al, 2014;Glatz et al, 2015).…”

Synthesis of platinum, palladium and rhodium complexes of α-aminophosphine ligands

“…A similar aminophosphine containing a benzhydryl substituent on the N atom acted similarly in the complexation (Scheme 47). 81 Starting from the mixture of the meso and the racemate forms, only the complexes of the meso form were obtained. The teracoordinated complex was formed in cis and trans forms in a ratio of 78 : 22.…”