Breaking Symmetry: Spontaneous Resolution of a Polyoxometalate

A chiral polyoxometalate [Hf(PW 11 O 39 ) 2 ] 10− ( 1 ) has been prepared and structurally characterized. It crystallizes in the chiral space group P 2 1 2 1 2, as a conglomerate of two enantiomerically pure crystals in the absence of any chiral source. The absolute configuration of 1 was determined from the Flack parameter by X‐ray crystallography. The structure of 1 comprises two lacunary [PW 11 O 39 ] 7− units, each functioning as a tetra‐dentate ligand sandwiching an 8‐coordinate Hf IV centre in a distorted square antiprismatic geometry. Optically active crystals of both enantiomers were spectroscopically distinguishable by means of solid state circular dichroism spectroscopy. This hafnium‐substituted polyoxometalate (POM), 1 , shows that spontaneous chiral resolution, a rare phenomenon, can be operable in POM systems.