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-MeC 6 H 4 CHMe 2, C 6 H 6, or C 6 Me 6; M = Ir, L = C 5 Me 5 ) with silver salts AgX (X = BF 4, CF 3 SO 3, CF 3 CO 2 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)]X 2 n ( n = 1, 2, 3). Further salts (X = ReO 4 -, 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 (NO 2 Me, Et 2 O, H{CF 3 CO 2 } 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 BF 4 -, CF 3 SO 3 -, or ReO 4 -, by radiotracer analysis in solution using 99m TcO 4 - and 188 ReO 4 -, and by cyclic voltammetry. The trimetallic complex [{Ir(Cp*)} 3 (CTV)][BF 4 ] 6 ( 9a ) in particular exhibits F···C CTV contacts as short as 2.78(3) Å. The dimetallic host [{Ru(η 6 -4-MeC 6 H 4 CHMe 2 )} 2 (η 6:η 6 -CTV)] 4+ ( 4 ) is shown to have a specific affinity for large tetrahedral anions and will selectively extract both 99 TcO 4 - and ReO 4 - from aqueous solution, even in the presence of a large excess of Cl -, CF 3 SO 3 -, NO 3 -, SO 4 2 -, and to some extent ClO 4 - .