Synthesis and reactivity of a PC_carbeneP cobalt(i) complex: the missing link in the cobalt PXP pincer series (X = B, C, N)

Abstract

We report the first example of a cobalt PCcarbeneP pincer complex (1) featuring a central alkylidene carbon donor accessed through the dehydration of an alcoholic POP proligand.

C−N, C−S and S−S Bond Cleavage by Rhodium PCcarbeneP Pincer Complexes

“…Herein, we report that 1‐PPh 3 and 1‐PPh 2 (C 6 F 5 ) readily cleave C−N and C−S formal double bonds in isothiocyanates and carbodiimides, and S−S bonds in disulfides (Scheme , D). These reactions demonstrate the ability of these electron deficient rhodium PC carbene P pincer systems to act as formal nucleophiles in addition to their electrophilic nature that we have previously reported upon …”

Cobalt(II) and (I) Complexes of Diphosphine‐Ketone Ligands: Catalytic Activity in Hydrosilylation Reactions

“…Possible reactivity involving the ketone moiety include: a) hemilabile behavior upon changing the oxidation state of the metal center, b) reversible addition of hydride to the moiety under catalytic conditions in analogy to the borane in Peters' catalyst, or c) its hydrosilylation to generate a catalytically active species. Recent experimental and computational investigations on similar Ph dpbp complexes with Co or Rh by Young and co‐workers showed the ability of the ketone to reversibly accept a hydride equivalent to become an sp 3 hydroxyalkyl ligand , . Related processes are plausible under hydrosilylation conditions, but the exact nature of the involved species is unclear, and further investigations are ongoing to address details of the mechanism.…”

“…Especially, exploration of the cobalt complexes in hydrosilylation reactions is of interest given the recent success in the field. Cobalt complexes ( Ph dpbp)CoCl 2 ( 2 Ph ) and ( Ph dpbp)CoCl ( 3 Ph ) illustrate the particular hemilabile behavior of the ketone moiety upon changing the oxidation state from Co II to Co I , resulting in an η 2 (C,O)‐coordination in the latter complex (Figure ) , . The adaptivity of the ligand in combination with the accessibility of low oxidation state such as Co I prompted us to evaluate the activity of these complexes for hydrosilylation.…”

H/D exchange under mild conditions in arenes and unactivated alkanes with C6D6 and D2O using rigid, electron-rich iridium PCP pincer complexes

“…Design elements of the ligands II/IV and III have been incorporated into a family of PCP ligands V introduced by our group 35 and also explored by others. [36][37][38][39] An attractive feature of these ligands is their ability to assume PC sp 3P or PC carbene P forms by the addition or removal of a hydrogen atom from the anchoring carbon of the pincer framework. This has precedence in the ligands II and IV but in the aryl-linked PCP systems V (and the related benzothiophene-based system VI 40 ) this is potentially more controllable because of the lack of b-hydrogens in the PCP linker framework, and through manipulation of the electronic properties of the ligand via substitution on the aryl linkers and/or rigidication of the ligand via additional linking of the backbone aryl groups.…”