When molecular chloride clusters of Nb, Mo, Ta, and W ([(M6Cl12)Cl-2(H2O)].4H(2)O (M = Nb, Ta) and (H3O)(2)[(M6Cl8)Cl-6](.)6H(2)O (M = Mo, W)) possessing an octahedral metal framework were treated in a helium stream above 200 degrees C, catalytic activity for the selective decomposition of phenyl acetate to phenol and ketene arose. The Fries rearrangement did not occur. The activity was ascribed to the Bronsted acidity of the hydroxo ligand that was formed by elimination of hydrogen chloride from the chloro and aqua ligands, and the selectivity was attributable to the large counter cluster anion that did not stabilize the intermediate protonated phenyl acetate and acetyl cations. The maximum activities of the Nb and Mo clusters appeared by activation at 250 degrees C and 400 degrees C, respectively, at which temperatures the retention of the octahedral cluster framework was ascertained by XDR analyses, Raman spectrometry, EXAFS spectrometry, and elemental analyses. (c) 2006 Elsevier B.V All rights reserved.