Bonding Insights from Structural and Spectroscopic Comparisons of {SnW5} and {TiW5} Alkoxido- and Aryloxido-Substituted Lindqvist Polyoxometalates

Identifier:  imarina:5132288

Handle: https://hdl.handle.net/20.500.11797/imarina5132288

Authors:  Kandasamy, Balamurugan; Bruce, Peter G; Clegg, William; Harrington, Ross W; Rodriguez-Fortea, Antonio; Pascual-Borras, Magda; Errington, R John

Abstract:
Incorporation of {MX}n+ groups into polyoxometalates (POMs) provides the means not only to introduce reactivity and functionality but also to tune the electronic properties of the oxide framework by varying M, X and n. In order to elucidate the factors responsible for differences in reactivity between {TiW5} and {SnW5} Lindqvist‐type hexametalates, a series of alkoxido‐ and aryloxido‐tin substituted POMs (nBu4N)3[(RO)SnW5O18] (R=Me, Et, iPr and tBu) and (nBu4N)3[(ArO)SnW5O18] (Ar=C6H5, 4‐MeC6H5, 4‐tBuC6H5, 4‐HOC6H4, 3‐HOC6H4 and 2‐CHOC6H4) has been structurally characterised and studied by multinuclear NMR (1H, 13C, 17O, 119Sn and 183W) and FTIR spectroscopy. Spectroscopic and structural parameters were compared with those of titanium‐substituted homologues and, when coupled with theoretical studies, indicated that Sn−OR and Sn−OAr bonds are ionic with little π‐contribution, whereas Ti−OR and Ti−OAr bonds are more covalent with π‐bonding that is more prevalent for Ti−OR than Ti−OAr. This experimental and theoretical analysis of bonding in a homologous series of reactive POMs is the most extensive and detailed to date, and reveals factors which account for significant differences in reactivity between tin and titanium congeners.