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

Abstract

Reaction of Ti(OPrⁱ)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] (1), which on further reactions with [Al(OPrⁱ)₃] or [Nb(OPrⁱ)₅] in 1 : 1 and 1 : 2 M ratios afforded heterometallic derivatives, [Ti(OGO)₃{M(OPrⁱ)_n−2}] and [Ti(OGO)₃{M(OPrⁱ)_n−1}₂] [where M = Al (n = 3), Nb (n = 5)], respectively. Similar reactions of Zr(OPrⁱ)₄∙PrⁱOH 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(OPrⁱ)_n−2}₂] and [Zr₂(OGO)₄(OGOH)₂M(OPrⁱ)_n−2] [M = Al (n = 3), Ti (n = 4), Nb (n = 5)] were prepared by 1 : 2 and 1 : 1 reactions, respectively, of [Zr₂(OGO)₂(OGOH)₄] with Al(OPrⁱ)₃, Ti(OPrⁱ)₄, or Nb(OPrⁱ)₅. Surprisingly, a 1 : 2 reaction of [VO(OPrⁱ)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] (18). 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] (9 and 18) were additionally characterized by single-crystal X-ray structure analysis.

Keywords:

• Metal glycolates
• alkoxides
• heterometallics
• precursors
• X-ray structure

Acknowledgements

J.S. wishes to thank DST, New Delhi for a fellowship. A.S. (Emeritus Scientist) wishes to acknowledge the Department of Science and Technology (DST) and University Grants Commission, New Delhi for the financial support. N.B.S. is indebted to the Department of Chemistry and the State Government of Rajasthan for a fellowship under Special Assistance Programme. Authors are also grateful to S.K. Gupta (UOR) for recording microanalytical (C, H) and spectral data and C. Lorentz (IRCELYON) for low-temperature ¹H NMR studies.

Disclosure statement

No potential conflict of interest was reported by the authors.

Notes

¹ The product 8 was characterized earlier by X-ray diffraction studies [14].