Elucidation of the resting state of a rhodium NNN-pincer hydrogenation catalyst that features a remarkably upfield hydride ¹H NMR chemical shift

Abstract

Rhodium(I) alkene complexes of an NNN-pincer ligand catalyze the hydrogenation of alkenes, including ethylene. The terminal or resting state of the catalyst, which exhibits an unprecedentedly upfield Rh-hydride (1)H NMR chemical shift, has been isolated and a synthetic cycle for regenerating the catalytically active species has been established.

An H‐Substituted Rhodium Silylene

“…Rhodium complexes bearing phosphinimine donors as part of am onoanionic R NNNl igand set, ( R NNN = 2,5-[R 2 P = N(4-iPrC 6 H 4 )] 2 N(C 4 H 2 ) À ,R= Ph, iPr) have recently been shownt o have ap ropensity to enact cooperative bond activation of H 2 and CO. [12] The ylidic nature of the PÀNb ond results in strongly basic Nd onors capable of stabilizing electrophilicm etals and main group functionalities. [13] Following the recognition that silylenes are defined by the pronouncedL ewis acidity of the Si atom, [8] precursor Rh silyl hydride complexes bearing a strongly-donating ligand set were targeted.…”

“…Recognizing that the iPr NNN ligand platform had previously demonstrated cooperative activity with Rh toward small molecules, [12] we sought am ethod by which silylene formation could be mediated by ah emilabile phosphinimine donor.W ith this goal in mind, and the knowledget hat ( iPr NNN)Rh(CO) 2 (1-(CO) 2 )e xhibits a k 2 -N,N bound iPr NNN ligand,i tw as postulated that combinations of 1-CO and/or 1-(CO) 2 with silanes might lead to oxidativea ddition products featuring ap endant phos-phinimine donor capableo fs tabilizing aL ewis acidic silylene Si.…”

X-ray crystal structure of [L 2Ag3]+[OTf]−·5C6D6: a monoanionic bisphosphinimine ligand supported trisilver complex

“…Crystals were grown in the NMR tube from benzene-d 6 . The synthesis of NaL has been previously published and utilizes a modified Staudinger reaction (Hä nninen et al, 2016;Staudinger & Meyer, 1919).…”

Tridentate NNN Ligand Associating Amidoquinoline and Iminophosphorane: Synthesis and Coordination to Pd and Ni Centers

“…The ligand C , exhibiting a central anionic pyrrole in place of a pyridine, was employed by the Hayes group to stabilize rare-earth complexes or prepare Rh I complexes able to promote CO activation in the presence of borane . Ligands D with a nitrogen atom as a linker between the PN functions were shown to stabilize rare-earth or uranium complexes, while ligands E based on carbazole were coordinated to f elements as well as rhodium centers . The coordination of the neutral ligands F to group 10 metal centers was studied by Stephan’s group .…”

“…9 Ligands D with a nitrogen atom as a linker between the PN functions were shown to stabilize rare-earth 10 or uranium 11 complexes, while ligands E based on carbazole were coordinated to f elements 12 as well as rhodium centers. 13 The coordination of the neutral ligands F to group 10 metal centers was studied by Stephan's group. 14 A closely related ligand labeled G was synthesized by Alajarin via an original Michael addition of amine onto vinyliminophosphorane and coordinated to cationic palladium centers.…”