Lead(II) as a template for the synthesis of a [1 + 1] 18-membered hexadentate N4S2-donor macrocycle; crystal and molecular structure of (acetato-O,O′)[3,13-dithia-6,10-diaza-1,8(2,6)-dipyridinacyclotetradecaphane-6,9-diene]lead(II) hexafluorophosphate