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Redox Instability of Copper(II) Complexes of a Triazine‐Based PNP Pincer
Author(s) -
Mohammadnezhad Gholamhossein,
Amirian Ali Mohammad,
Görls Helmar,
Plass Winfried,
Sandleben Aaron,
Schäfer Sascha,
Klein Axel
Publication year - 2021
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.202001129
Subject(s) - chemistry , ligand (biochemistry) , medicinal chemistry , redox , phosphinate , pincer movement , pincer ligand , copper , triazine , pyridine , cycloaddition , electron paramagnetic resonance , azide , catalysis , stereochemistry , polymer chemistry , inorganic chemistry , organic chemistry , fire retardant , biochemistry , physics , receptor , nuclear magnetic resonance
Abstract The new Cu(I) complex [Cu(PNP NTPh ‐Ph)Cl] ( 1 ) containing the tridentate PNP pincer ligand N , N ′‐bis(diphenylphosphino)‐2,6‐diamino‐4‐phenyl‐1,3,5‐triazine was obtained from the reaction of [Cu(SMe 2 )Cl] n with the ligand as ether solvate 1 . 0.5Et 2 O. 1 was independently obtained from a reaction mixture containing the ligand and the Cu(II) precursor CuCl 2 . 2H 2 O in 50 % yield alongside with the Cu(II) coordination polymer [Cu(O 2 PPh 2 ) 2 ] n ( 2 ). From the reaction of Cu(NO 3 ) 2 ⋅ 3H 2 O with PNP NTPh ‐Ph in the presence of pyridine the complexes [Cu(O 2 PPh 2 ) 2 (Py) 2 (H 2 O)] ( 3 ), [Cu(O 2 PPh 2 )(Py) 2 (NO 3 )] 2 ( 4 ), and [Cu(Py) 4 (NO 3 ) 2 ] . Py ( 5 ), were obtained, 2 , 3 , and 4 contain diphenyl‐phosphinate ligands. The underlying redox reaction of the ligand and Cu(II) yielding the oxidised ligands observed in the by‐products and the Cu(I) product complex was further studied using electrochemistry and UV‐vis spectroelectrochemistry. Attempts to synthesise the Cu(II) complex [Cu(PNP NTPh ‐Ph)(NO 3 ) 2 ] ( 6 ) in a mechanochemical experiment gave evidence for this unprecedented species from ESI‐MS(+) and EPR spectroscopy but also revealed its very high sensitivity to air and moisture. The catalytic activity of 1 was investigated in the azide‐alkyne cycloaddition yielding various 1‐benzyl‐4‐phenyl‐1 H ‐1,2,3‐triazoles. The environmentally benign (“green”) and cheap EtOH/H 2 O solvent mixture turned out to be very suitable. Melting points, FT‐IR, and NMR spectra of the triazole products were analysed.