Titanium(IV) and Zirconium(IV) Sulfato Complexes Containing the Kläui Tripodal Ligand: Molecular Models of Sulfated Metal Oxide Surfaces
✍ Scribed by Qian-Feng Zhang; Tony C. H. Lam; Xiao-Yi Yi; Eddie Y. Y. Chan; Wai-Yeung Wong; Herman H. Y. Sung; Ian D. Williams; Wa-Hung Leung
- Publisher
- John Wiley and Sons
- Year
- 2004
- Tongue
- English
- Weight
- 544 KB
- Volume
- 11
- Category
- Article
- ISSN
- 0947-6539
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✦ Synopsis
Abstract
Treatment of titanyl sulfate in about 60 mM sulfuric acid with NaL~OEt~ (L~OEt~^−^=[(η^5^‐C~5~H~5~)Co{P(O)(OEt)~2~}~3~]^−^) afforded the μ‐sulfato complex [(L~OEt~Ti)~2~(μ‐O)~2~(μ‐SO~4~)] (2). In more concentrated sulfuric acid (>1 M), the same reaction yielded the di‐μ‐sulfato complex [(L~OEt~Ti)~2~(μ‐O)(μ‐SO~4~)~2~] (3). Reaction of 2 with HOTf (OTf=triflate, CF~3~SO~3~) gave the tris(triflato) complex [L~OEt~Ti(OTf)~3~] (4), whereas treatment of 2 with Ag(OTf) in CH~2~Cl~2~ afforded the sulfato‐capped trinuclear complex [{(L~OEt~)~3~Ti~3~(μ‐O)~3~}(μ~3~‐SO~4~){Ag(OTf)}][OTf] (5), in which the Ag(OTf) moiety binds to a μ‐oxo group in the Ti~3~(μ‐O)~3~ core. Reaction of 2 in H~2~O with Ba(NO~3~)~2~ afforded the tetranuclear complex (L~OEt~)~4~Ti~4~(μ‐O)~6~ (6). Treatment of 2 with [{Rh(cod)Cl}~2~] (cod=1,5‐cyclooctadiene), [Re(CO)~5~Cl], and [Ru(__t__Bu~2~bpy)(PPh~3~)~2~Cl~2~] (t__Bu~2~bp__y=4,4′‐di‐tert‐butyl‐2,2′‐dipyridyl) in the presence of Ag(OTf) afforded the heterometallic complexes [(L~OEt~)~2~Ti~2~(O)~2~(SO~4~){Rh(cod)}~2~][OTf]~2~ (7), [(L~OEt~)~2~Ti(O)~2~(SO~4~){Re(CO)~3~}][OTf] (8), and [{(L~OEt~)~2~Ti~2~(μ‐O)}(μ~3~‐SO~4~)(μ‐O)~2~{Ru(PPh~3~)(__t__Bu~2~bpy)}][OTf]~2~ (9), respectively. Complex 9 is paramagnetic with a measured magnetic moment of about 2.4 μ~B~. Treatment of zirconyl nitrate with NaL~OEt~ in 3.5 M sulfuric acid afforded [(L~OEt~)~2~Zr(NO~3~)][L~OEt~Zr(SO~4~)(NO~3~)] (10). Reaction of ZrCl~4~ in 1.8 M sulfuric acid with NaL~OEt~ in the presence Na~2~SO~4~ gave the μ‐sulfato‐bridged complex [L~OEt~Zr(SO~4~)(H~2~O)]~2~(μ‐SO~4~) (11). Treatment of 11 with triflic acid afforded [(L~OEt~)~2~Zr][OTf]~2~ (12), whereas reaction of 11 with Ag(OTf) afforded a mixture of 12 and trinuclear [{L~OEt~Zr(SO~4~)(H~2~O)}~3~(μ~3~‐SO~4~)][OTf] (13). The Zr^IV^ triflato complex [L~OEt~Zr(OTf)~3~] (14) was prepared by reaction of L~OEt~ZrF~3~ with Me~3~SiOTf. Complexes 4 and 14 can catalyze the Diels–Alder reaction of 1,3‐cyclohexadiene with acrolein in good selectivity. Complexes 2–5, 9–11, and 13 have been characterized by X‐ray crystallography.