Anionic Cyclometalated Platinum(II) Tetrazolato Complexes as Viable Photoredox Catalysts

Abstract

The synthesis, characterization, photophysical and photocatalytic studies of anionic platinum­(II) tetrazolato complexes, with the general structure [TBA]­[Pt­(CNC)­TzR], are reported, where CNC2– represents a doubly cyclometalated 2,4,6-triphenylpyridine, TzR– is an anionic 5-substituted tetrazolato ligand (with a variable R functional group), and TBA+ is the tetrabutylammonium countercation. The complexes were prepared by substitution of the DMSO ligand in [Pt­(CNC)­(DMSO)] with the corresponding tetrazolato ligand. No emission from the platinum­(II) complexes was detected at room temperature in solution, but the photophysical properties could be assessed in the solid state, where all the complexes display emission bands attributed to aggregates. The platinum­(II) complexes were found to facilitate a range of fundamental classes of visible-light-mediated photoredox-catalyzed reactions, including α-amino C–H functionalization processes, such as Povarov-type reactions and the addition of α-amino C–H bonds across Michael acceptors, in addition to ATRA chemistry, and a hydrodeiodination. With the exception of the hydrodeiodination process, the best Pt­(II) catalysts provided turnover numbers of 150–175 in each of these transformations.

Cyclometalated Pt Complexes of CNC Pincer Ligands: Luminescence and Cytotoxic Evaluation

“…Tridentate CNC bis-cyclometalating Hph­(py)­phH ligands such as the prototypical 2,6-diphenylpyridine (HPhPyPhH) (Chart ) were introduced to organoplatinum­(II) chemistry about 30 years ago. , Neutral or anionic complexes (Chart ) of these dianionic – CNC – ligands have been studied together with derivatives of the monoanionic CNN or NCN ligands (HCNN = derivatives of 6-phenyl-2,2′-bipyridine, Hphbpy; NC­(H)N = derivatives of 1,3-bis­(2-pyridyl)­benzene, py­(Hph)­py), mainly due to their interesting luminescence properties − and their use as scaffolds with particular chemical reactivity. − …”

Synthetic access to a phosphorescent non-palindromic pincer complex of palladium by a double oxidative addition – comproportionation sequence

“…Pincer complexes 1 of platinum and gold gained increasing attention during the past 30 years due to their simple preparation 2 and appealing photophysical properties making them interesting for applications in photocatalysis 3 and electroluminescent devices, 4,5 but in the field of catalysis 6 and biomedical applications 7 as well. Contrasting the plethora of investigations concerned with diphenylpyridine-based (C^N^C) pincer complexes, only one example of palladium (1) has been published in the literature until now (Fig.…”

The Povarov Reaction: A Versatile Method to Synthesize Tetrahydroquinolines, Quinolines and Julolidines

“…This can be achieved with photocatalysis by platinum(II) complexes and oxidation of N,N-dimethylaniline to the corresponding iminium species, which readily undergoes a [4+2] cyclization with N-phenylmaleimide. 100 Functionalization can also be effected in the absence of light. In the work of Min et al, the use of Cu(I) as a catalyst and tert-butyl hydroperoxide as the terminal oxidant enabled the reactions of tertiary…”