Pergamon 0277-5387(94) 00399-8 Polyhedron Vol. 14, No. 10, pp. 1327-1332, 1995 Copyright © 1995 Elsevier Science Ltd Printed in Great Britain. All rights reserved 0277-5387/95 $9.50+0.00 SYNTHESIS, COORDINATION AND REDOX PROPERTIES OF A NOVEL TETRATHIAFULVALENE TETRA(BENZO- 15-CROWN-5)ETHER LIGAND PAUL D. BEER,* JONATHAN P. DANKS and DUSAN HESEK Inorganic Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QR, U.K. (Received 23 September 1994; accepted 29 September 1994) Abstraet--A new tetrathiafulvalene tetra(benzo-15-crown-5)ether ligand (4) has been pre- pared and polymetallic alkali metal complexes of 4.4Na ÷ and 4.2K ÷ stoichiometries isolated. Relatively small anodic perturbations of the redox-active ligand's redox couples were observed in the presence of either alkali metal cation. The design of new chemical sensors 1'2 and redox switchable ligands3 has led in recent years to the syntheses of a variety of organometallic and tran- sition metal coordinated redox-active macrocyclic receptor molecules, which have been shown to elec- trochemically recognize, in some cases selectively, cationic and anionic guests in polar solvents includ- ing water. 4'5 The tetrathiafulvalene (TTF) moiety is an attractive organic redox centre to incorporate or append to various macrocyclic host cavities, and indeed Otsubo and Ogura 6 and Becher et aL7 have recently prepared some TTF--crown ether deriva- tives. We report here the synthesis, coordination and electrochemical properties of a novel TTF- tetra(benzo-15-crown-5)ether ligand including the isolation of polymetallic complexes of sodium and potassium cations. RESULTS AND DISCUSSION Synthesis TTF (1) was treated with just over four equi- valents of lithium diisopropylamide at -78°C in dry tetrahydrofuran to give the tetralithium salt (2). 8 Reaction of 2 with the disulphide of benzo- l 5-crown-5 (3) 9 gave the new TTF-tetra(benzo-15- crown-5)ether ligand (4) as a yellow solid in 41% yield (Scheme 1). IH and 13C NMR spectroscopy, fast atom bombardment mass spectrometry (FABMS) and elemental analysis characterized the new redox-active ligand's proposed structure (see Experimental section). Coordination studies Refluxing 4 with acetonitrile solutions of excess amounts of sodium and potassium hexa- fluorophosphate salts led to the isolation of the respective alkali metal complexes as red solids in quantitative yields. The elemental analysis of the sodium complex (Table 1) indicated a 4Na+: 4 stoichiometry in which one sodium cation is com- plexed within each of the benzo crown ether moi- eties (Fig. 1). With potassium the elemental analysis (Table 1) suggested 2K ÷ : 4 stoichiometry and the FABMS spectrum of the complex revealed a molecular ion at m/z = 1620, corresponding to Table 1. Elemental analyses for sodium and potassium complexes of 4 Analysis a (%) Complex C H [4" Na4] (PF6)4 35.9 3.9 (36.0) (3.7) [4" K21 (PF6)z 42.7 4.6 (42.2) (4.3) *Author to whomcorrespondenceshould be addressed, aCalculated values in parentheses. 1327