The Supporting Information is available free of charge on the ACS Publications website. Supporting methods and experimental section, Tables and Figures, Single-crystal X-ray Diffraction Data of M1-I, M1-Cl and M2-I, CCDC numbers: 2280568, 2280576 and 2280826 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by emailing data_request@ccdc.cam.ac.uk, or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033.