Intramolecular NH···Pt Interactions of Platinum(II) Diimine Complexes with Phenyl Ligands

Abstract

Pt(pipNC)(2)(phen) [pipNC(-) = 1-(piperidylmethyl)phenyl anion; phen = 1,10-phenanthroline] was prepared by the reaction of cis-Pt(pipNC)(2) with phen. Crystallographic and (1)H NMR data establish that the phen ligand is bidentate, whereas each piperidyl ligand is monodentate and bonded to the platinum at the ortho position of the phenyl group. Acidic conditions allowed for isolation of the salts of diprotonated Pt(pipNHC)(2)(diimine)(2+) adducts (diimine = phen, 2,2'-bipyridine, or 5,5'-ditrifluoromethyl-2,2'-bipyridine). Crystallographic and spectroscopic data for the diprotonated complexes are consistent with H···Pt interactions (2.32-2.51 Å) involving the piperidinium groups, suggesting that the metal center behaves as a Brønsted base. Metal-to-ligand (diimine) charge-transfer states of Pt(pipNHC)(2)(phen)(2+) in solution are strongly destabilized (>2500 cm(-1)) relative to Pt(pipNC)(2)(phen), in keeping with the notion that NH···Pt interactions effectively reduce the electron density at the metal center. Though N···Pt interactions in Pt(pipNC)(2)(phen) appear to be weaker than those found for outer-sphere two-electron reagents, such as Pt(pip(2)NCN)(tpy)(+) [pip(2)NCN(-) = 1,3-bis(piperidylmethylphenyl anion; tpy = 2,2':6',2'-terpyridine], each of the Pt(pipNC)(2)(diimine) complexes undergoes diimine ligand dissociation to give back cis-Pt(pipNC)(2) and free diimine ligand. Electrochemical measurements on the deprotonated complexes suggest that the piperidyl groups help to stabilize higher oxidation states of the metal center, whereas protonation of the piperidyl groups has a destabilizing influence.

New C∧N∧C Bis-Cyclometalated Platinum(II) Complexes: Synthesis, Structures, and Photophysical Properties

“…13,49 Complexes 6-10 exhibit Pt-N and Pt-C (C^N^C) distances which are slightly shorter when compare to those observed in complexes 2-5. This is also related to the C 1 -Pt coupling constants obtained in the 13 95,97 Additionally, in the structure of 8 ( Figure 3c) we find an edge-to-face  interaction, one when compare with the first one and both lie in the upper range of those observed for hydrogen bonds. 76,81,[104][105][106] Despite the weakness of these interactions, which is reflected in the long contact parameters (d (N---O) = 2.90 -3.06 Å), they are strong enough to arrange the monomers into a 3D network.…”

“…C NMR spectra. Because the pyridine derivatives appear to be poorer -acceptors, the bonding within the Pt-CNC moiety is stronger, showing shorter bond distances and bigger coupling constants.Inspection of the packing within the crystals of 2-10 revealed the presence of weak intermolecular interactions including •••,[48][49][50]85 C-H•••,48,50,[85][86][87][88] C-H•••O,48,50,[89][90][91] C-H•••N,48,90,92,93 N-H•••Pt,[94][95][96][97][98] N-H•••,[99][100][101] and as well as conventional N-H•••Ohydrogen bonding in 10,76,81,90 (Figures 1-4and S1-S8). The combination of these weak interactions results in the packing of the monomers molecules into 2D or 3D networks.…”

An electrochemical technique for controlled dissolution of zirconium based components of light water reactors

“…Glassy carbon was eliminated based on the inability to formulate it in the shape, size or orientation needed for effective electrical contact between the electrode and the liner surfaces with convenient ease. Platinum based working electrodes were observed to produce more reproducible voltammograms compared to Ni and Au as observed before, [32][33][34] and were adapted as working electrode for subsequent studies.…”

Click Reaction Driven, Highly Fluorescent Dinuclear Organogold(I) Complex Exhibits a Dual Role: A Rare Au···H Interaction and an Antiproliferative Agent

“…Transition metal complex based M···H interactions have attracted enormous interest in fundamental and applied chemistry, such as in organometallic catalysts . In general, the M···H hydrogen bonds involving N–H/O–H donor groups with various transition-metal elements are well documented. − In addition, aurophilic (Au/Au) interactions have been well reported . However, the Au···H interaction in gold is still rarely found and has been less explored in gold chemistry and is present either due to the ligand–counterion interaction or crystal packing rather than direct interactions between Au and H atoms. − However, M···H hydrogen bonds in other transition-metal complexes have been well investigated both structurally in the solid state and spectroscopically in the solution state. − However, to the best of our knowledge there exist few reports of experimental evidence of rare C–H···Au “hydrogen bond” interactions both in the solid state and in the solution state. , …”