Neutral thioether and selenoether macrocyclic coordination to Group 1 cations (Li-Cs) - synthesis, spectroscopic and structural properties

The complexes [M(L)][BArF] (BArF = tetrakis{3,5-bis(trifluoromethyl)-phenyl}borate), L = [18]aneO(4)S(2) (1,4,10,13-tetraoxa-7,16-dithiacyclooctadecane): M = Li-Cs; L = [18]aneO(2)S(4) (1,10-dioxa-4,7,13,16-tetra-thiacyclooctadecane): M = Li, Na, K; L = [18]aneO(4)Se(2) (1,4,10,13-tetraoxa-7,16-diselenacyclooctadecane): M = Na, K, as well as [Na(18-crown-6)][BArF], are obtained in good yield as crystalline solids by reaction of M[BArF] with the appropriate macrocycle in dry CH2Cl2. X-ray crystallographic analyses of [Li([18]aneO(4)S(2))][BArF] and [Li([18]aneO(2)S(4))][BArF] show discrete distorted octahedral cations with hexadentate coordination to the macrocycle. The heavier alkali metal complexes all contain hexadentate coordination of the heterocrown, supplemented by M. F interactions via the anions, producing extended structures with higher coordination numbers; Na: CN = 7 or 8; K: CN = 8; Rb: CN = 9; Cs: CN = 8 or 10. Notably, all of the structures exhibit significant M-S/Se coordination. The crystal structures of the potassium and rubidium complexes show two distinct [M(heterocrown)](+) cations, one with M. F interactions to two mutually cis [BArF](-) anions, and the other with mutually trans [BArF](-) anions, giving 1D chain polymers. Solution multinuclear (H-1, C-13, Li-7, Na-23, Cs-133) NMR data show that the macrocyclic coordination is retained in CH2Cl2 solution.