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

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 -.