Preparation and characterization of rhodium(iii), iridium(iii) and ruthenium(ii) bearing 1,3- or 1,4-dithianesElectronic supplementary information (ESI) available: Crystal data and ORTEP figures for 2b, 2ab and 3c and further experimental details. See http://www.rsc.org/suppdata/dt/b3/b306496d/