Inclusion of Neutral and Anionic Guests within the Cavity of π-Metalated Cyclotriveratrylenes

Abstract

Treatment of the chloride bridged species [{M(L)Cl(μ-Cl)}2] (M = Ru, L = 4-MeC6H4CHMe2, C6H6, or C6Me6; M = Ir, L = C5Me5) with silver salts AgX (X = BF4, CF3SO3, CF3CO2 etc.) followed by reflux with the bowl-shaped macrocycle cyclotriveratrylene (CTV) results in the clean formation of mono-, di-, and trimetallic CTV complexes [{M(L)} n (CTV)]X2 n (n = 1, 2, 3). Further salts (X = ReO4 -, I-) may be generated by anion metathesis. All three types of complex display novel host−guest properties. In the case of the monometallic hosts the disruption of the characteristic columnar packing mode of the CTV, a result of the presence of the metal center, leads to the inclusion of neutral and anionic guest species (NO2Me, Et2O, H{CF3CO2}2 -, etc.) within the CTV cavity. For complexes where n = 2 or 3 the inclusion of anionic guests is invariably observed. The extent of anion binding has been established by means of X-ray crystal structure determinations upon various di- and trimetallic species containing BF4 -, CF3SO3 -, or ReO4 -, by radiotracer analysis in solution using 99mTcO4 - and 188ReO4 -, and by cyclic voltammetry. The trimetallic complex [{Ir(Cp*)}3(CTV)][BF4]6 (9a) in particular exhibits F···CCTV contacts as short as 2.78(3) Å. The dimetallic host [{Ru(η6-4-MeC6H4CHMe2)}2(η6:η6-CTV)]4+ (4) is shown to have a specific affinity for large tetrahedral anions and will selectively extract both 99TcO4 - and ReO4 - from aqueous solution, even in the presence of a large excess of Cl-, CF3SO3 -, NO3 -, SO4 2-, and to some extent ClO4 -.

Immobilization, Trapping, and Anion Exchange of Perrhenate Ion Using Copper-Based Tripodal Complexes

“…cavity. [34][35][36] In our tripodal system, the three Cu-containing arms of 2 fold to form a preorganized cavity that can encapsulate a ReO 4 -anion through electrostatic interactions.…”

Organometallic cavitands: Cation–π interactions and anion binding via π-metallation

“…have synthesised lariat ethers with pendant arms containing alkene, alkyne and arene groups (10)(11)(12) to study the interaction of the side arms with the metal cation. Binding of Na + and K + by the macrocycle is observed but solid-state structures of 10 and 11 show that there is no interaction between the side arms and the metal cation [50,51].…”

“…This work was extended to a series of ruthenium and iridium cationic hosts involving mono-, bi-and tri-metallated CTV hosts [{M(L)} n (CTV)] 2n+ (M = Ru, L = pMeC 6 H 4 CHMe 2 , n = 1, 29a; 2, 29b; 3, 29c; M = Ir, L = C 5 Me 5 , n = 1, 30a; 2, 30b; 3, 30c), which all show intra-cavity guest inclusion, in contrast to classical CTV inclusion compounds [10]. In the case of the monometallic complexes 29a and 30a the disruption of the columnar CTV packing mode [27] creates a cavity for neutral guest inclusion such as nitromethane.…”

“…Metal-binding by cavitands containing aromatic -surfaces and the resulting modifications in their properties is of enduring interest [1][2][3][4][5][6][7][8][9][10][11][12][13]. The calixarenes and their relatives, particularly the partially pre-organised cone isomer of calix [4]arenes have been studied for many years in this regard, Fig.…”

Anion‐π‐Wechselwirkungen ins rechte Licht gerückt

“…Ein Beispiel dafür ist in Abbildung 5 (oben) zu sehen. ¾hnlich zeigten Fairchild und Holman, [103,104] dass ) und Gleichgewichtsabstände (R e , ), berechnet auf dem MP2/6-31 + + G**-Niveau. [85] Anion-p-Kation …”