Organometallic benzylidene anilines: donor–acceptor features in NCN-pincer Pt(ii) complexes with a 4-(E)-[(4-R-phenyl)imino]methyl substituent

Abstract

A series of organometallic 4,4'-substituted benzylidene aniline complexes 4-ClPt-3,5-(CH2NMe2)2C6H2CH[double bond, length as m-dash]NC6H4R'-4', abbreviated as PtCl[NCN(CH[double bond, length as m-dash]NC6H4R'-4')-4], with R' = NMe2, Me, H, Cl, CN (, respectively), was synthesized via a Schiff-base condensation reaction involving reaction of PtCl[NCN(CH[double bond, length as m-dash]O)-4] () with the appropriate 4-R'-substituted aniline derivative () in toluene. The resulting arylplatinum(ii) products were obtained in 75-88% yield. Notably, product was also obtained in 68% yield from a reaction in the solid state by grinding solid with aniline . The structures of , , and in the solid state (single crystal X-ray diffraction) showed a non-planar geometry, in particular for compound . The electronic interaction between the donor benzylidene fragment PtCl(NCN-CH) and the para-R' aniline substituent through the azomethine bridge was studied with NMR and UV/Vis spectroscopy. Linear correlations were found between the azomethine (1)H, the (195)Pt NMR and various (13)C NMR chemical shifts, and the substituent parameters σF and σR of R' at the aniline site. In common with organic benzylidene anilines, the azomethine (1)H NMR chemical shift showed anomalous substituent behavior. The (195)Pt NMR chemical shift of the platinum center can be used as a probe for the electronic properties of the delocalized π-system of the benzylidene aniline framework, to which it is connected. The dual substituent parameter treatment of the azomethine (13)C NMR shift gave important insight into the unique behaviour of the Pt-pincer group as a substituent. Inductively, it is a very strong electron-withdrawing group, whereas mesomerically it behaves like a very strong electron donating group.

Metal‐ligand cooperative activation of HX (X=H, Br, OR) bond on Mn based pincer complexes

“…In such an approach one can start with a “skeleton” complex bearing a TM center coordinated to a pincer scaffold. Selected sites on the scaffold or metal center can be functionalized generating an ensemble of new TM complexes using various combinations of functional groups [13–16] . Experimentally only a handful of functionalized variants of pincer ligand scaffolds have been reported.…”

A rapidly-reversible absorptive and emissive vapochromic Pt(II) pincer-based chemical sensor

“…The polypyridine ligand incorporates significant scope for modification, with numerous potential and synthetically-accessible substitution sites. By varying the ligand chemistry, compounds with emissive frequencies across the visible spectrum have been reported 22 – 24 . The monodentate ancillary ligand L, occupying the fourth Pt coordination site, likewise plays an important role in the solid-state aggregation and intermolecular interactions 25 , 26 .…”

Structural, spectral, electronic, and molecular docking investigations on N,N‐dimethyl‐2‐[(1E)‐({[(methylsulfanyl)methanethioyl]amino}imino)methyl]aniline

“…The azomethine group (CHN) protons can be observed as singlet signals in region (in the range of about 9.00 ± 0.70 ppm) slightly above the aromatic proton chemical shift region. [ 34–36 ] In this connection, the H21 azomethine proton was obtained at 8.56 ppm (exp.) and 8.38 ppm (calc.)…”