Homometallic glycolates containing hydroxyl functionality for anchoring another metal: synthesis and characterization of heterometallic alkoxide<b>–</b>glycolates of Ti and Zr incorporating Al and Nb

Reaction of Ti(OPr^<i>i</i>)₄ with 2-methyl-2,4-pentanediol [HOGOH, where G = CMe₂CH₂CH(Me)] in 1 : 3 M ratio under reflux afforded the monomeric [Ti(OGO)(OGOH)₂] (<b>1</b>), which on further reactions with [Al(OPr^<i>i</i>)₃] or [Nb(OPr^<i>i</i>)₅] in 1 : 1 and 1 : 2 M ratios afforded heterometallic derivatives, [Ti(OGO)₃{M(OPr^<i>i</i>)_n−2}] and [Ti(OGO)₃{M(OPr^<i>i</i>)_n−1}₂] [where M = Al (<i>n</i> = 3), Nb (<i>n</i> = 5)], respectively. Similar reactions of Zr(OPr^<i>i</i>)₄∙Pr^<i>i</i>OH with a number of glycols [HOGOH, where G = CH(Me)CH(Me), CMe₂CMe₂, CMe₂CH₂CH(Me)] yielded dimeric [Zr₂(OGO)₂(OGOH)₄]. [Zr₂(OGO)₆{M(OPr^<i>i</i>)_n−2}₂] and [Zr₂(OGO)₄(OGOH)₂M(OPr^<i>i</i>)_n−2] [M = Al (<i>n</i> = 3), Ti (<i>n</i> = 4), Nb (<i>n</i> = 5)] were prepared by 1 : 2 and 1 : 1 reactions, respectively, of [Zr₂(OGO)₂(OGOH)₄] with Al(OPr^<i>i</i>)₃, Ti(OPr^<i>i</i>)₄, or Nb(OPr^<i>i</i>)₅. Surprisingly, a 1 : 2 reaction of [VO(OPr^<i>i</i>)₃] with 2,2-diethyl-1,3-propanediol in benzene followed a different reaction and produced a neutral tetranuclear derivative [V₄(O)₄(μ-OCH₂CEt₂CH₂O)₂(OCH₂CEt₂CH₂O)₄] (<b>18</b>). All of these derivatives were characterized by elemental analysis, molecular weight measurements, FT-IR, and ¹H NMR (and wherever possible, by ²⁷Al or ⁵¹V NMR) spectroscopic studies. The derivatives [Zr₂(OCMe₂CH₂CH(Me)O)₂(OCMe₂CH₂CH(Me)OH)₄] (<b>9</b> and <b>18</b>) were additionally characterized by single-crystal X-ray structure analysis.