Keywords: Zirconium / Zirconium oxo cluster / Hafnium oxo cluster / Metal carboxylate / Ligand exchange 12 ] 2 is also reported for comparison. The Zr12 clusters are structurally related to the Zr6 clusters since they are composed of two Zr6 sub-units which are bridged by four carboxylate ligands. In each compound, carboxylic acid molecules interact with the cluster by hydrogen bonding to part of the µ 3 -OH ligands. The clusters are highly dynamic in solution, due to site exchange of the

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Crystalline oximate derivatives of titanium alkoxides [Ti(OR)2(ON=CR′R″)2]2 were obtained when Ti(OR)4 (R = iPr, Et) was treated with various oximes (cyclopentanone oxime, cyclohexanone oxime, acetoxime, ethyl methyl ketoxime or 2,4‐pentandione dioxime). Formation of bis‐substituted derivatives was favored in each case, and only one mono‐substituted derivative, [Ti(OiPr)3(ON=C6H10)]2, was isolated. Two isomers were observed for [Ti(OR)2(ON=CR′R″)2]2, differing by the mutual orientation of the oximate ligands. The NO groups of the oximate ligands are side‐on coordinated to one titanium atom in each case. Three partially hydrolyzed derivatives, viz. Ti6O6(OiPr)6(ON=CR2)6 (CR2 = CMe2 or C5H8) and Ti4O2(OiPr)8(ON=CMe–CH2–CMe=NO)2 were also structurally characterized. In these derivatives the NO groups bridge two titanium atoms.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

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