Assembly of titanium embedded polyoxometalates with unprecedented structural featuresElectronic supplementary information (ESI) available: Thermogravimetric analysis, FT-IR spectra, catalytic experiments and detailed information regarding electrochemistry, mass spectrometry experiments, and DFT calculations. CCDC reference numbers 795796and 795797. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c0dt01327g

Two titanium embedded polyoxometalates with unprecedented structural features are presented: a monotitanium containing tungstoantimonate Na13H3[TiO(SbW9O33)2]·33 H2O featuring a {TiO}2+moiety (1) and a hexatitanium containing tungstoarsenate K6[Ti4(H2O)10(AsTiW8O33)2]·30 H2O containing a {Ti4(H2O)10}16+moiety (2). Both compounds have been fully characterised by single crystal X-ray diffraction, elemental analysis, IR and TGA. 1is constructed from two α-B-{SbIIIW9O33} fragments linked by five sodium cations and an unprecedented square pyramidal Ti(O)O4group with a terminal TiO bond, and 2exhibits a Krebs-type structure composed of two {AsTiW8O33} fragments, where one W(vi) centre has been substituted for a Ti(iv) centre in each, fused together viaa belt of four additional Ti(iv) centres. This system represents the tungsten Ti-incorporated polyoxoanion with one of the highest Ti : W ratios so far reported. Additionally, 2could also be isolated as an n-tetrabutylammonium salt and has been further characterised by electrochemistry and electrospray ionisation (ESI) MS studies. Due to the unique nature of these systems, both have been fully investigated using DFT calculations yielding highly interesting results. Structure 1has been optimised with five sodium atoms in the belt position, which in addition to reducing the high charge of the cluster influence a stabilisation of the antimony lone pairs. Electrostatic potential calculations highlight the high electronegativity of the terminal oxygen on the titanium centre, enhancing real potentiality as a reactive site for catalysis. [ABSTRACT FROM AUTHOR]