Isolation and characterization of the [Ga2Al18O8(OH)36(H2O)12]8+ cluster: cationic variations on the Wells-Dawson topologyElectronic supplementary information (ESI) available: Additional synthetic and characterization details, bond distance and valence tables, CIF file, computational methods details, benchmarking, and additional computational results. CCDC 1058796. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c5cc03069b

The structural chemistry of Group 13 polyoxometalates lags far behind related negatively charged transition metal species and limits the development of advanced materials. A novel heterometallic cluster [Ga 2 Al 18 O 8 (OH) 36 (H 2 O) 12 ] 8+ (Ga 2 Al 18 ) has been isolated using a supramolecular approach and structurally characterized using single-crystal X-ray diffraction. Ga 2 Al 18 represents the Wells-Dawson structure polycations and variations in the structural topology may be related to the initial stabilization of the Keggin isomer. DFT calculations on the related -Keggins (GaAl 12 and Al 13 ), Ga 2 Al 18 , and theoretical Al 2 Al 18 clusters reveal similar features of electronic structure, suggesting additional heteroatom substitution in other isostructural clusters should be possible. A new structural topology for a Wells-Dawson type of polyoxometalate has been isolated and DFT calculations show the same valence electronic structure regardless of heteroatom identity.