Alcohol–alkoxide exchange between Sn(OBut)4 and HOBut in co-ordinating and non-co-ordinating solvents

Proton NMR magnetization-transfer experiments have been utilized to measure the kinetic parameters of alcohol interchange between the homoleptic tin(IV) alkoxide Sn(OBut)4 and ButOH in various solvents. The reaction was studied in pyridine with rate constants measured over the temperature range 24–112 °C (k1= 0.22 s–1 at 24 °C to 12 s–1 at 112 °C) from which activation parameters were derived (ΔG‡298= 18.8 kcal mol–1, ΔH‡= 9.5 kcal mol–1 and ΔS‡=–30 cal K–1 mol–1). These data along with variable-temperature 119Sn-{1H} NMR data are consistent with a five-co-ordinate intermediate such as [Sn(OBut)4·HOBut] and suggest that the metal, even in sterically encumbered metal alkoxide compounds such as Sn(OBut)4, is sufficiently co-ordinatively and electronically unsaturated to react with bulky alcohols. In non-co-ordinating solvents such as benzene the exchange rate is faster (k= 1.93 s–1 at 24 °C). Room-temperature solution 119Sn-{1H} NMR spectroscopy of Sn(OBut)4 dissolved in pyridine (py) shows evidence for formation of Sn(OBut)4·py, consistent with an exchange mechanism in which py competes with ButOH for co-ordination sites at tin(IV). Unambiguous evidence for the co-ordination of donor molecules to tin(IV) in homoleptic tin(IV) alkoxide compounds was obtained from the isolation and structural characterization of Sn(OSiPh3)4(NC5H5)2·0.5NC5H5, the first example of a donor adduct of a homoleptic tin(IV) alkoxide. Single-crystal X-ray diffraction showed that this compound is monomeric and approximately octahedral with trans pyridine groups.

[1]  M. Hampden‐Smith,et al.  Solvent-Dependent Ester Elimination and Ligand Exchange Reactions between Trimethylsilyl Acetate and Tin(IV) Tetra-tert-Butoxide , 1995 .

[2]  M. Hampden‐Smith,et al.  Ester elimination versus ligand exchange: the role of the solvent in tin–oxo cluster-building reactions , 1995 .

[3]  R. W. Schwartz,et al.  Formation of perovskite phase mixed metal oxides via thermal decomposition of metal-organic complexes with bifunctional ligands , 1994 .

[4]  G. Beaucage,et al.  General routes to porous metal oxides via inorganic and organic templates , 1994 .

[5]  V. Day,et al.  Dodecatitanates. A new family of stable polyoxotitanates , 1993 .

[6]  M. Hampden‐Smith,et al.  Chemical aspects of solution routes to perovskite-phase mixed-metal oxides from metal-organic precursors , 1993 .

[7]  A. McCormick,et al.  Kinetic and thermodynamic study of the hydrolysis of silicon alkoxides in acidic alcohol solutions , 1993 .

[8]  Mark J. Hampden-Smith,et al.  The solid state and solution structures of tin(IV) alkoxide compounds and their use as precursors to form tin oxide ceramics via sol-gel-type hydrolysis and condensation , 1992 .

[9]  V. Day,et al.  Solution structure elucidation of early transition metal polyoxoalkoxides using oxygen-17 NMR spectroscopy , 1991 .

[10]  C. Sanchez,et al.  Hydrolysis-condensation process of .beta.-diketonates-modified cerium(IV) isopropoxide , 1991 .

[11]  A. Datye,et al.  Hydrolytic Condensation of Tin(IV) Alkoxide Compounds to Form Particles with Well‐Defined Morphology , 1991 .

[12]  N. Bampos,et al.  Kinetics of skeletal rearrangement of H2FeP[CH2CH2CH2P(CH3)2]3 by an inversion–transfer–recovery NMR method , 1991 .

[13]  M. Hampden‐Smith,et al.  Solid state and solution structural investigation of homoleptic tin(IV) alkoxide compounds. Part I. Sn(O—t-Bu)4 and [Sn(O—i-Pr)4•HO—i-Pr]2 , 1991 .

[14]  M. Veith,et al.  Darstellung und Struktur von Alkali-penta-tert-butoxystannaten. IV , 1990 .

[15]  L. Hubert-Pfalzgraf,et al.  Synthesis, structural principles and reactivity of heterometallic alkoxides , 1990 .

[16]  L. Hubert-Pfalzgraf,et al.  Alcohol adducts of alkoxides: intramolecular hydrogen bonding as a general structural feature , 1990 .

[17]  M. Hampden‐Smith,et al.  Synthesis and characterization of thallium tin ethoxide ([Tl2Sn(OEt)6]n), a one-dimensional polymer in the solid state , 1989 .

[18]  Clément Sanchez,et al.  Sol-gel chemistry of transition metal oxides , 1988 .

[19]  L. Hubert-Pfalzgraf.  Alkoxides as molecular precursors for oxide-based inorganic materials: opportunities for new materials , 1988 .

[20]  C. Sanchez,et al.  Hydrolysis of titanium alkoxides: modification of the molecular precursor by acetic acid , 1987 .

[21]  Bernd Wrackmeyer.  119Sn-NMR Parameters , 1985 .

[22]  P. Kuchel,et al.  NMR spin exchange kinetics at equilibrium in membrane transport and enzyme systems. , 1983, Journal of theoretical biology.

[23]  J. J. Led,et al.  The applicability of the magnetization-transfer NMR technique to determine chemical exchange rates in extreme cases. The importance of complementary experiments , 1982 .

[24]  J. I. Kaplan,et al.  NMR of Chemically Exchanging Systems , 1980 .

[25]  Frederic A. Prisley,et al.  Tertiary Butyl Alcohol , 1924, Science.