Complexes of Group 2 dications with soft thioether- and selenoether-containing macrocycles

A new route to cationic complexes of Mg, Ca, Sr and Ba with 18-membered ring O4S2, O4Se2 and O2S4 donor macrocycles from metal acetonitrile complexes with weakly coordinating [BAr(F)](-) anions is described. The precursors used were [M(MeCN)x][BAr(F)]2 (M = Mg, x = 6; M = Ca, x = 8) and [M'(acacH)(MeCN)5][BAr(F)]2 (M' = Sr or Ba). Reaction of these with the heterocrowns, [18]aneO4S2 (1,4,10,13-tetraoxa-7,16-dithiacyclooctadecane), [18]aneO4Se2 (1,4,10,13-tetraoxa-7,16-diselenacyclooctadecane) or [18]aneO2S4 (1,10-dioxa-4,7,13,16-tetrathiacyclooctadecane) in anhydrous CH2Cl2 solution gave [M(heterocrown)(MeCN)2][BAr(F)]2 for M = Mg, Ca or Sr, whilst the larger Ba forms [Ba(heterocrown)(acacH)(MeCN)][BAr(F)]2. The complexes have been characterised by microanalysis, IR, (1)H and (13)C{(1)H} NMR spectroscopy. X-ray crystal structures are reported for [Ca([18]aneO2S4)(MeCN)2][BAr(F)]2, [Ca([18]aneO4Se2)(MeCN)2][BAr(F)]2, [Sr([18]aneO4S2)(MeCN)2][BAr(F)]2, and [Sr([18]aneO4Se2)(MeCN)2][BAr(F)]2 which contain 8-coordinate metal centres with trans-nitrile ligands and κ(6)-heterocrowns, and for the 9-coordinate [Ba([18]aneO4Se2)(acacH)(MeCN)][BAr(F)]2. Adventitious hydrolysis of the magnesium complexes in solution results in six-coordinate complexes, [Mg(κ(3)-[18]aneO4Se2)(OH2)2(MeCN)][BAr(F)]2 and [Mg(κ(3)-[18]aneO4S2)(OH2)2(MeCN)][BAr(F)]2, whose structures were determined. X-ray crystal structures are also reported for [Mg(MeCN)6][BAr(F)]2, [M(MeCN)8][BAr(F)]2 (M = Ca, Sr) and [Ca(18-crown-6)(MeCN)2][BAr(F)]2.