On the question of site-selective ligand exchange in carboxylate-substituted metal oxo clusters

Abstract

Reaction of [Ti4Zr4O6(OBu)4(OMc)16] (OMc = methacrylate) with acetylacetone (acacH) resulted in dissection of the cluster and formation of [Ti(OBu)2(acac)2] and the smaller cluster [Ti2Zr4O4(OMc)16]. In contrast, the same reaction with [Zr6O4(OH)4(OOCR)12]2·6RCOOH (R = Et, CH2CH=CH2) led to site-selective substitution of two carboxylate ligands and formation of isostructural [Zr6O4(OH)4(OOCR)12-x(acac)x]2·6RCOOH (x ≤ 1). The question of cluster degradation upon ligand exchange was probed for reactions of [Ti4Zr4O6(OBu)4(OMc)16] (OMc = methacrylate) and [Zr6O4(OH)4(OOCR)12]2·6RCOOH with acetylacetone (acacH). A [Ti(OBu)2(acac)2] unit was dissected from the bimetallic Ti/Zr cluster, while site-selective substitution of two carboxylate ligands occurred in the latter cluster.