Organotin(IV) Alkoxides, Siloxides, and Related Stannoxanes. Characterisation and Thermogravimetric Studies

The pendant-arm ligand [2-(CH₂O)₂CH]C₆H₄ (L) was successfully employed in the isolation of a limited series of organotin(IV) alkoxides and siloxides. A unique example of stannaboroxane was synthesised following a straight-forward protocol. The thermogravimetric studies performed on the novel organotin(IV) siloxides reveal their potential application as single-source precursors for tin-silicate materials.

Abstract

A series of C,O-chelated organotin(IV) alkoxides, L₂PhSnO ^t Bu (4), L₂PhSnOMe (6), L₂Sn(O ^t Bu)₂ (11), and siloxides L₂PhSnOSiPh₃ (3), L₂Sn(OSiPh₃)₂ (10) (L=[2-(CH₂O)₂CH]C₆H₄), was prepared by salt elimination reactions. They were obtained from the organotin(IV) iodides L₂PhSnI (1) or L₂SnI₂ (2) upon reactions with ^t BuOK, MeONa or Ph₃SiONa, respectively, in dry THF or methanol. Under non-inert conditions, compounds 4 and 6 undergo combined hydrolysis and condensation to give the hexaorganodistannoxane (L₂PhSn)₂O (5). The stannoxane 5 is easily hydrolysed to L₂PhSnOH (7), which quickly converts back when heated. Basic hydrolysis of diiodide 2 produces the cyclic oxide (L₂SnO)₃ (8). Its reaction with an equimolar amount of Ph₃SiONa gives only a mixture of the expected L₂SnI(OSiPh₃) (9), 10 and the precursor, 2. Yet, 8 shows a unique reactivity pattern when combine with m-tolyl boronic acid, affording stannaboroxane (L₂SnO)₂OB(m-tol) (12). All the isolated species were characterised in solution by NMR spectroscopy and mass spectrometry. The solid-state molecular structures of 1–5, 10–12 were established by single-crystal X-ray diffraction (XRD). Additionally, thermogravimetric analysis of 3–5, 8, 10, and 12 was conducted.

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