Metal‐to‐Metal Distance Modulation by Ligand Design: A Case Study of Structure‐Property Correlation in Planar Chiral Cyclophanyl Metal Complexes

Abstract

Multinuclear metal complexes have seen tremendous progress in synthetic advances, their versatile structural features, and emerging applications. Here, we conceptualize Metal-to-Metal distance modulation in cyclophanyl metal complexes by bridging ligand design employing the cofacially stacked cyclophanyl-derived pseudo-geminal, -ortho, -meta, and -para constitutional isomers grafted with N-, O-, and P-containing chelates that allow the installation of diverse (hetero)metallic moieties in a distance-defined and spatially-oriented relation to one another. Metal-to-Metal distance modulation and innate transannular "through-space" π-π electronic interactions via the co-facially stacked benzene rings in cyclophanyl-derived complexes as well as their specific stereochemical structural features (element of planar chirality) are crucial factors that contribute to the tuning of structure-property relationships, which stand at the very center from the perspective of cooperative effects in catalysis as well as emerging material applications.

Metal‐to‐Metal Distance Modulated Au(I)/Ru(II) Cyclophanyl Complexes: Cooperative Effects in Photoredox Catalysis

“…Scheme 2. Incorporation of the gold(I) chloride and ruthenium(II) moiety to obtain pAuRu (6) as a 1 : 1 mixture of diastereomers. tht = tetrahydrothiophene, 2,2'-bpy = 2,2'-bipyridine.…”

“…Mass Spectrometric Analysis: The metal complexes AuRu (6,(18)(19)(20), PCP-Ru (22) and Ru(bpy) 2 (ppy) were analyzed by ESI-MS in their monocationic form, without counterions. In a second step, those were isolated in the ion trap and exposed to collision induced dissociation (CID) and photodissociation (PD).…”

“…The transition S45 at 345 nm shows ILCT (interligand charge transfer) character, where the electron density moves from a ligand coordinated at Au to the ppy ligand. In the UV-PD gas phase spectrum of pAuRu (6), a weak shoulder appears around 310 nm. This is assigned to the transitions S79 and S80, characterized as MLCT involving Au and the ligands ppy, bpy and bpy'.…”

“…Figure 10. Gas phase UV-PD spectrum (blue) and calculated transitions (stick) of [pAuRu] + calculated with B3LYP, as well as the liquid phase absorption spectrum in CH 2 Cl 2 (red) of pAuRu (6). The different ligands of the complex are marked with their abbreviations.…”

Regioselective ortho‐Palladation of [2.2]Paracyclophane Scaffolds: Accessing Planar and Central Chiral N,C‐Palladacycles

“…[12] Previously, a series of oxazolinyl substituted and PCP bearing pyridines located on different decks that display various regioisomers for their ability in mono-and dinuclear regioselective cycloruthenation complexes with [RuCl 2 (p-cymene)] 2 were introduced that hold two Ru-metal centers with defined distance and spatial orientation. [13] In this work, we sought to develop a series of new mono-and bimetallic N,C-palladacycles by regioselective ortho-palladation of amine-and imine-functionalized PCPs, employing Pd(OAc) 2 , and LiCl followed by the modular treatment of Ph 3 P, Cy 3 P, and (Ph 2 PCH 2 ) 2 (dppe). The dimethylethylamine derivative 2 b was prepared by reductive amination starting from 4-acetyl[2.2]paracyclophane (1, Scheme 1A).…”